Antimicrobial Effect of Electrospun Nanofibers Loaded with Silver Nanoparticles: Influence of Ag Incorporation Method

Villarreal-Gómez, Luis Jesús; Pérez-González, Graciela Lizeth; Bogdanchikova, Nina; Pestryakov, Alexey; Nimaev, Vadim; Soloveva, Anastasiya; Cornejo-Bravo, José Manuel; Toledaño-Magaña, Yanis

doi:https://doi.org/10.1155/2021/9920755

Journal of Nanomaterials

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Cellular Responses to Nanomaterials with Biomedical Applications

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Review Article | Open Access

Volume 2021 | Article ID 9920755 | https://doi.org/10.1155/2021/9920755

Antimicrobial Effect of Electrospun Nanofibers Loaded with Silver Nanoparticles: Influence of Ag Incorporation Method

Luis Jesús Villarreal-Gómez,^1,2Graciela Lizeth Pérez-González,^1,2Nina Bogdanchikova,³Alexey Pestryakov,^4,5Vadim Nimaev,⁶Anastasiya Soloveva,⁶José Manuel Cornejo-Bravo,²and Yanis Toledaño-Magaña⁷

Academic Editor: Antonios Kelarakis

Received03 Mar 2021

Accepted29 Jul 2021

Published17 Aug 2021

Abstract

The antimicrobial bioactivity of silver nanoparticles is well known, and they can be used widely in many applications, becoming especially important in the biomedical industry. On the other hand, the electrospun nanofibers possess properties that can enhance silver nanoparticle applicability. However, silver nanoparticle bioactivity differs depending on the loading of silver ions into electrospun nanofibers. This review is aimed at comparing different silver incorporation methods into electrospun nanofibers and their antimicrobial activity, discussing each procedure’s limitations, and presenting the most promising one. This review showed that the preferred techniques for incorporating silver nanoparticles were direct blending and ultraviolet irradiation methods due to their simplicity and efficient results. Besides, polyacrylonitrile nanofibers (PAN) have been the most reported system loaded with silver nanoparticles. Finally, independently of the technique used, silver nanoparticle-loaded nanofibers show high antimicrobial activity in all cases.

1. Introduction

In the last decades, the interest of the biomedical industry in nanomaterials has increased due to its promising applications against different diseases. In this sense, AgNPs are among the most studied nanomaterials principally due to their highly efficient antimicrobial properties [1–6]. It is known that AgNP efficiency increases using a carrier [4]. Electrospun nanofibers are ideal carriers for AgNPs since their small dimensions permit homogeneous distribution and avoid mass aggregation. The blend of technologies between nanofibers and nanoparticles maximizes both structure properties, making them an ideal amalgam for many applications.

Electrospun nanofibers are synthesized by the electrospinning technique, which allows the generation of ultrafine fibers using natural or synthetic biomaterials [7–9]. These three-dimensional scaffolds are produced in a 10–1000 nm diameter’s range [10–18]. Nanofiber’s properties such as nanometric thickness, controllable porosity, and high surface contact area [7, 8] allow the potential applications in tissue engineering [19, 20], drug delivery systems [21–24], biosensor fabrication [25, 26], energy storage [27], solar cells [28], water filtration [29, 30], catalysis [31, 32], and sensing [33, 34], among other uses. Specifically, the loading of electrospun nanofibers with AgNPs has become attractive [35–37] for many applications such as food packaging [38], filters [39]. Moreover, there are investigations of electrospun nanofibers loaded with AgNPs for their use in healthcare and other biomedical applications [37, 40, 41], including wound dressing [9] and implants [40].

Thus, this amalgam of nanofiber/AgNP system properties has been proved and attributed to the metallic nanoparticle proportion, size, and spatial distribution of AgNPs in the fibers [42] (entry 3).

The AgNP-loaded electrospun systems can control the silver ions released through the immobilization of the AgNPs [43]. Strategies for the fabrication of AgNP-loaded nanofibers include incorporation of silver nitrate (AgNO₃) by direct blending into the polymeric solution followed by photoreduction with ultraviolet (UV) irradiation [44–46], thermal reduction [47] (entry 14), or the silver mirror reaction [48] (entry 12), among other methods.

A comparative study of AgNP loading methods on PVA was performed by electrospinning AgNO₃-polymeric solutions followed by a reduction posttreatment. In that study, the AgNPs were mixed in the polymer solution before the electrospinning process, and the resulting polymeric scaffolds were immersed in a silver solution followed by a reduction process (comparing UV and thermal treatments). The authors reported that UV reduction was the more efficient method to incorporate AgNPs on nanofibers’ surfaces [49].

In this work, we compare the results published regarding the incorporation of AgNPs in nanofibers, including all the above methods. Nevertheless, AgNP-loaded nanofibers differ in their activity depending on the silver loading method into the nanofibers. Hence, this review compares different techniques of AgNP incorporation into electrospun nanofibers and their antimicrobial effectivity to identify the most promising method and discuss the current limitation of each of them.

2. Methods of AgNP Immobilization for Loading of Electrospun Nanofibers

In literature, several strategies merge the electrospun nanofibers and AgNPs, which coat the nanofibers’ surface or are embedded into the bulk [50].

The parameters considered in this work to determine the best among the discussed methods include the AgNP distribution in/on the electrospun fibers. Bortolassi et al. discussed that the bioactivity of the AgNPs depends on their capacity to attach to the microbial cell membrane’s surface, altering the permeability and cellular homeostatic, thereby AgNP distribution and availability over the surface of the fibers become crucial for the bioactivity. Hence, the combination of the high specific surface area of the electrospun fibers and an AgNP high loading with homogeneous distribution over the surface of the fibers become a desirable design for the high final antimicrobial activity [51, 52]. For instance, the loaded AgNP nanofibers fabricated by the direct addition of AgNPs into the polymeric solution decreased the antimicrobial efficiency of AgNPs due to their aggregation. When the AgNPs are incrusted in the fibers, they are not exposed for direct contact with the cellular membrane [53].

Also, it is remarkable that the presence of AgNPs into/on the polymeric nanofibers affects its intrinsic properties. The most important characteristic that is modified is its bioactivity, which is improved [46, 51–53]. Among other properties that are affected by the presence of the AgNPs on/in the fibers are the mechanical properties such as reduction in surface tension [54], increase in average fiber diameter [36], and changes in thermal properties including the glass transition temperature, degradation temperature, and temperature-dependent mass loss. In general, AgNP-loaded nanofibers are more resistant to heat. All property changes mentioned above are caused by the structural changes of the polymeric backbone [36, 46, 47].

Below, we present and compare several methods to create AgNP-loaded electrospun nanofiber scaffolds.

2.1. Direct Blending Method

A facile method to produce AgNP-loaded nanofibers is the direct blending of premade AgNPs in the polymer solution before electrospinning [35], being preferred the AgNP colloidal solutions for easy incorporation into the nanofibers [55]. The encapsulation of AgNPs within the poly(έ-caprolactone) (PCL) microfibers without Ag at the surface of microfibers allows controlling release of AgNPs from the hybrid constructs in combination with high antibacterial activity [56].

Several polymeric systems have been reported to be electrospun and loaded with AgNPs, such as the case of poly(vinylidene fluoride) (PVDF) [20] (entry 4), PVA/poly(urethane) (PU) [57] (entry 2), nylon [42, 58], and poly(vinyl pyrrolidone) (PVP) [59] (entry 1), among others. This versatility of modified nanofibers is because AgNPs can be prepared with various solvents such as formic acid (FA), dimethylacetamide (DMAc), water (H₂O), and hexafluoro propanol (HFIP). Also, it has been recognized by several studies that the loaded amount of AgNPs can greatly differ from 0.1 to 30% wt., of the total polymeric mass. On the other hand, it has been observed that the higher the content of AgNPs added to the polymeric solution, the higher the conductivity, promoting smaller fiber’s diameters [35, 55]. These resultant fiber morphologies can be rough due to the coating and immersion of AgNPs mentioned before [55].

2.1.1. Experimental Conditions of the Direct Blending Method

For a reported direct blending technique, the first step was the dissolution at 50°C of nylon 6 (15% wt.) in formic acid, a reduction agent for AgNO₃. In this study, the AgNO₃ (0.5 and 1.25% wt.) was slowly added to the polymer solution, kept in darkness with constant stirring at room temperature for 24 h, enough time for the reduction of AgNO₃. After that, the final dispersion was electrospun [42] (entry 3).

In another study, tannic acid prepared in an ammonia solution (NH₃·H₂O) was added to the polymer solution as a reducing agent of AgNO₃. After one hour, the powder obtained by solution concentration was resuspended in acetone and filtered. Synthesized AgNPs were extracted using vacuum drying at room temperature and then added to a PVP solution before electrospinning (Figure 1).

2.2. UV-Irradiation Method

The amount of AgNPs loaded on nanofibers is more significant when a UV-irradiation method is used to produce the initial silver burst release, either in the form of AgNPs or in the residual Ag⁺ ions. This method promotes incorporating the AgNPs into nanofibers’ surface in a random distribution [44–46]. The method induces the silver ion migration from the core to the surface during the formation of the AgNPs [45]. Also, it has been described that the UV-irradiation method achieves smaller AgNP diameters with narrower distributions than the other methods. These results are relevant for antimicrobial activity because the high surface area of AgNPs promotes a faster Ag⁺ ion release [60] (entries 8 and 16).

Moreover, the biological activity of electrospun scaffolds is related to the AgNO₃ content. It was reported that AgNP-loaded poly(ether amide) (PEBA) fibers were fabricated using 0.15% of AgNO₃ in the polymer solution for electrospinning inhibits >99.99% of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) cultures. However, when the AgNO₃ concentration decreased (0.05% AgNO₃), the bacterial inhibition decreases (20% less activity in both bacterial strains) [61] (entry 7). A similar activity was observed on loaded AgNPs in gelatin nanofibers evaluated against S. aureus and E. coli, with selective activity for the later strain. Authors suggest that the different biocidal effect is due to the generous peptidoglycan layer next to the cell membrane of Gram-positive bacteria such as S. aureus, which serves as a protective structure for external threats reducing the AgNP introduction to the bacterial cell [60].

Phan et al. [46] (entry 5) synthesized silver/polyacrylonitrile (Ag/PAN) nanocomposite membranes testing their antibacterial activity. In this study, electrospun AgNP/PAN nanofibers were prepared from the solution of PAN and AgNO₃ using the UV-irradiation method to reduce the Ag⁺ ions into AgNPs. The nanofiber antibacterial activity was tested against E. coli and Bacillus subtilis (B. subtilis), finding long-term bactericidal effects. The authors claim that these nanofiber systems are useful for water purification, bacterial filtration, and biomedical devices [46] (entry 5).

2.2.1. Experimental Conditions of the UV-Irradiation Method

In the case of the UV-irradiation method, most of the studies prepared the Ag-loaded nanofibers by mixing the polymeric and AgNO₃ solutions previous to the electrospinning process [44, 45, 60–62] except for Phan et al. [46] (entry 5) that electrospun the fibers before the AgNO₃ incorporation. An advantage of this method is that, as reported, no extra time or additional solvent is required [44–46, 60–63]. Besides, no further treatments are needed after the irradiation step, and the exposition time to UV light can be changed depending on the desired results. Interestingly, it has been reported that after four hours of irradiation, the number and size of the AgNPs continuously increased [44]. Figure 2 explains the UV-irradiation method general procedure, where the incrusted AgNPs can be appreciated over the nanofiber surface.

Additionally, the electrospinning conditions in both methods (direct blending and UV irradiation) are selected depending on the polymer system used [62]. After the electrospinning process, the UV irradiation step is developed. Here, the UV light’s specific wavelengths are 254 and 365 nm [46] (entry 5), but not a specific irradiation time is presented. Several conditions are reported as follows: UV light (254 nm) irradiation for 24 h [46] (entry 5), UV light (254 nm) for 6 h [61] (entry 7), UV light (254 and 365 nm) irradiation from 10 min to 8 h [44] (entry 10), UV light (254 nm) irradiation for 10 min [45] (entry 9), UV light (365 nm) irradiation from 3 h [62] (entries 8 and 16), and UV light (not defined wavelength) irradiation for 4 h [63] (entry 6).

2.3. Silver Mirror Reaction Method (SMR)

The SMR method is a versatile method that uses different substances as reducing agents for AgNO₃ solution to produce the AgNPs, which coat the surface of an object submerged in the reaction solution. This reduction can generate a visual phenomenon that resembles a shiny mirror coat over the upper surface of the solution or over an object submerged.

It is used to create a controllable smooth coating over different surfaces: for large surfaces (e.g., telescope glasses) and extremely small surfaces (nanofibers) [64] (entry 13). The reaction occurs at ambient conditions, which is very appropriate for nanotechnology applications [65] (entry 11). Even though using this method is impossible to achieve shape control of AgNPs, the technique can produce quasispheres, wires, rods, right bipyramids, beams, spheres, cubes, or octahedrons [65, 66].

Several applications have been reported for SMR synthesized nanofibers. Excellent antimicrobial activities against bacteria and fungi were observed with PAN/AgNP nanofibers with AgNPs evenly dispersed on the nanofiber’s external surface. Those were prepared with PAN nanofibers pretreated in AgNO₃ aqueous solution followed by the SMR process [48]. Also, noble metal nanoparticles loaded on electrospun nanofibers have been synthesized due to their potential use as sensors [67]. Another application is for silver nanowire membranes, in this case, Ag⁺ ions coated poly(acrylonitrile–co–phenylethylene) (P(AN-S)) nanofibers used as a template for the reduction of a silver solution on the nanofibers’ surface. The SMR process allows silver deposition on the nanofiber’s surface. Thus, nanowires were developed and characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). These nanowires have different resistance and transmittance on PET and glass: 15 Ω/sq and 80%, and 37 Ω/sq and 81%, respectively [65].

2.3.1. Experimental Conditions of the SMR Method

The reported methodologies differ in time and posttreatment steps [53, 54], but an advantage over other methods is that the reaction can be made at room temperature. In two manuscripts, the polymeric solution needs a 12 h reaction at room temperature before the electrospinning process [48, 65]. In another study, just 30 min were used, and a sol-gel process was done before the electrospinning step [64]. Hence, the polymer solution preparation time is not standardized and differs depending on the methodology used to achieve complete polymer dissolution. Wang et al. prepared PAN nanofibers stirring the polymeric solution just for 1 hour at room temperature, using the same polymer as the compared studies. Hence, these polymeric solution reaction times can vary depending on the polymer chosen and the AgNP incorporation method [11]. Within the reported procedures, we can find nanofibers exposed to the AgNO₃ solution for 18 and 24 h in a dark room at room temperature [48], and AgNO₃ solution mixed with the polymer solution before the electrospinning process [64, 65]. Hence, the AgNO₃ solution can be added before or after the formation of fibers.

Regarding electrospinning, parameters depend more on the polymeric solution than on the AgNP immobilization method or the presence of AgNO₃. The electrospinning parameters determine the morphology, diameter, porosity, and distribution of the fibers [20]. After fiber preparation, several posttreatments are needed. Obtained fibrous mats are submerged into AgNO₃ solution at the desire concentration, usually in a 1 : 2 AgNO₃/polymer solution ratio, but other relative proportions AgNO₃/polymer were also tested [64, 65]. Ag⁺ ions are deposited over the fiber’s surface when the AgNO₃ solution is added to the fibers earlier prepared. In contrast, Ag⁺ ions get encapsulated into the fibers if AgNO₃ solution is added before fiber preparation [68]. Other procedures include fibrous scaffolds freeze-drying before the SMR [48] or a two-step filtration with an organic-free filter followed by a 0.2 μm filter to removed particles [64].

Other differences were observed for the reported SMR step. In some cases, the authors dropped ammonium hydroxide (NH₄OH) into AgNO₃ solution to prepare a diamine silver (I) (Ag (NH₃)₂⁺) solution [65] (entry 11). Others used a hydrazinium hydroxide (N₂H₅OH) solution as a reducing agent [64] (entry 13). On the other hand, Shi et al. [48] (entry 12) submerged the fibers into the AgNO₃ solution, then added concentrated ammonia (NH₃) (2.5% wt.) into the beakers just until the brown precipitate dissolved, and then added formaldehyde (HCHO) (1% wt.) as the final step. Additional steps after SMR as a threefold washing procedure with distilled water or 40°C vacuum oven drying are reported [64, 65].

A simplified schematization of the silver mirror reaction method showing the AgNP distribution on the nanofiber’s surface is represented in Figure 3.

2.4. Thermal Reduction Method

This method is promising due to the easy steps to perform. Some advantages of this method are as follows: uniform AgNP distribution on the nanofiber’s cross-section [69], decomposition temperature decreases when Ag content increases on PVA-AgNPs [49, 62], and more desired stability (less probability of AgNP aggregation). However, AgNP leaching could inactivate the membrane once the first Ag⁺ release from the nanofiber surface has occurred [62].

Silver conducting nets were synthesized using the thermal reduction method over a plane scaffold prepared with electrospun nanofibers of poly(methyl methacrylate) (PMMA), and silver trifluoroacetate (STA) deposited on transparent substrates. Those nets had high transmittance and low resistance [70]. STA is reduced to AgNPs with a 100°C postthermal treatment that decomposes the organic polymer to achieve the one-dimensional net configuration. The nets’ sheet resistance was as low as 15 Ω/sq correlated with the morphology and the STA/PMMA ratio. Properties as surface plasmon resonances (SPRs), fiber morphologies, and electrical and optical properties (diffusive optical transparency of ≈54%) were determined.

2.4.1. Experimental Conditions of the Thermal Reduction Method

For this method, several strategies are reported to incorporate the Ag⁺ ions into the nanofibers. Jatoi et al. [47] (entry 14) prepared acetate cellulose (CA) solution under constant stirring for 24 h and then electrospun the solution. On the other hand, Chen et al. [70] (entry 15) replaced the AgNO₃ solution with an STA solution and mixed it with the PMMA solution using a reaction time of 24 h at room temperature. Similarly, Lin et al. [62] (entries 8 and 16) mixed the previously prepared (~2 h) PVA solution with the AgNO₃ solution stirring vigorously for an additional 30 min, taking just 2.5 h before the electrospinning step.

For the electrospinning technique, no special modifications were added. The optimization of the fiber formation and the electrospinning parameters were chosen depending on the properties (viscosity, concentration, conductivity, and surface tension) of the polymer solution [20, 47, 62, 70].

CA fibrous mats were synthesized with a simple alkaline treatment (NaOH) by submerging the fibers in the solution for 48 h, creating cellulose fibers (CEF). The CEAg samples were obtained immersing the CEF for 24 h at 23°C in an AgNO₃ solution then dried for 2 h. Finally, the reduction process of CEAg was done in a drying oven at 160°C for 1 h, 1.5 h, and 2 h [47]. Silver nets also could be obtained by thermal decomposition at 500°C of PMMA for 3 h under air or nitrogen atmosphere. In this case, AgNPs were obtained by reduction of silver precursors for 12 h at 100°C [70]. Contrary to the previous two discussed methods, before the electrospinning process, Lin et al. [62] (entries 8 and 16) pretreated the polymeric/AgNO₃ solution at 105°C for 1 h, no further treatments after the obtention of the fibers.

Figure 4 represents the general procedure of the thermal reduction method.

AgNP particle size and average nanofiber diameter obtained with four AgNP incorporation methods are presented in Table 1.

3. Antimicrobial Activities of Ag Nanofibers

AgNPs are well known to have antimicrobial bioactivity. This bioactivity occurs through cell membrane damage, free radical generation, and DNA interaction, among others (Figure 5) [71, 72]. One of the proposed mechanisms of AgNP action is the effect on the lipid bilayer induced by the AgNP accumulation in the bacterial cell wall [59]. Thus, membrane permeability increased, causing cell damage and death. Moreover, the effect increases while the AgNP size decreases [73]. Another mechanism suggested for cell death induced by AgNPs is the reaction with thiol groups (–SH) of cysteine and phosphorus compounds on the cell wall, affecting respiration and replication processes [59, 74]. Another explanation for the antimicrobial activity is that metal depletion may cause the formation of irregularly shaped pits in the outer membrane and change membrane permeability, which is caused by a progressive release of lipopolysaccharide molecules and membrane proteins [63] (entry 6).

AgNPs or the released silver ions (Ag⁺) can also enter the bacterial cells and interact with compounds containing sulfur and phosphorus, preventing DNA replication and inactivating proteins. Besides, they can inhibit the activity of endocellular ATP levels, thereby preventing the cell’s respiratory function. Furthermore, AgNPs have been reported to induce the release of reactive oxygen species (ROS), forming free radicals with strong bactericidal effects (Figure 5) [75]. AgNPs have a broad antibacterial spectrum covering aerobic, anaerobic, and Gram amphoteric bacteria [76], low incidence of resistance [77], and sustained antibacterial activity [78], thus have been widely used in antibacterial wound dressings [75].

The antimicrobial activity of AgNPs depends on the surface area of the nanomaterial [72]. The highest concentrations of released Ag⁺ ions have been observed from AgNPs with the highest surface area. On the contrary, Ag⁺ ion’s low release has been found for AgNPs with low surface area, resulting in weak antimicrobial properties [79]. Most electrospun nanofibers do not affect microbial cell reproduction by themselves, but only with the presence of AgNPs. Such is the case of PAN nanofibers which were endowed with excellent antibacterial properties due to the introduction of AgNPs. The authors claim that AgNPs have strong antibacterial properties since they attach to the cell walls and disturb cell-wall permeability and cellular respiration [48] (entry 12).

Poly(vinyl alcohol-co-vinyl acetate)/octadecyl amine-montmorillonite) (P(VA-co-VAc)/ODA-MMT) nanofibers loaded with AgNPs showed high antimicrobial activity against fungus (Candida albicans, tropicalis, glabrata, keyfr, and krusei) and bacteria (S. aureus and E. coli) [80]. It has been demonstrated that Ag⁺ release confers the AgNP microbicidal effect [81–83]. Moreover, the internalization of AgNPs into the fibers permits a longer bioavailability of the silver on the application site because the release of the A⁺ ions depends on the time of fiber degradation [84]. This could explain that 10 nm AgNPs were more toxic for E. coli than 20-80 nm due to a more efficient cell-particle contact. Thus, AgNP toxicity correlates with size and content because of the Ag⁺ initial release rate, affecting the fibrous scaffold cytotoxicity. However, the AgNP amount also regulates the long-term Ag⁺ release rate and, therefore, the microbicidal activity [72, 75].

AgNP-loaded electrospun membranes with antibacterial properties have been tested in food packaging material to delay food spoilage or bacteria contamination [63, 78]. Chaudhary et al. [63] (entry 6) used an electrospun AgNP/PAN composite filter media to cover a nutrient media in room conditions and pass ambient air through the filter media. The nutrient media protected by the nanofibrous filter remained free of bacteria growth after two months, while the unprotected nutrient media show microorganism growth. Taking advantage of the excellent dispersion of AgNPs in electrospun nanofibers, Castro-Mayorga et al. [85] reported electrohydrodynamic processing, which combines the electrospraying and electrospinning techniques to produce a multilayer system comprising a poly(hydroxy alkanoate) (PHA) substrate and an electrospun PHA coating containing AgNPs. The materials reduced the Salmonella enterica population below the detection limits at a very low silver loading of 0.002% wt.

Table 1 shows the physicochemical and antimicrobial properties of AgNP-nanofiber systems prepared by the discussed methods. It can be observed that each of the four methods affects the resulted size of the incorporated AgNPs. Moreover, small particle sizes (<10 nm) can be achieved in all methods.

It should be noted that the data in Table 1 include the following: (1) inhibition zone diameter, which may not be comparable, or (2) results of distinct AgNP concentrations leading to approximately 100% inhibition of microorganism growth, which is also not representative. In the future, the minimal inhibitory concentration (MIC) and the inhibitory concentration (IC₅₀) should be presented as data; moreover, for this purpose, the microdilution test to evaluated antimicrobial activity should be used [37].

Also, it can be appreciated that information about the resulting AgNP size is not reported in some articles. The antimicrobial results are reported in different ways, making it difficult to compare studies.

4. Comparisons among Methods of Incorporation of AgNPs

Metal nanoparticles tend to aggregate in the polymer matrix during nanofiber formation, highlighting the need for new and better methods that allow better metal nanoparticle dispersion on the polymer nanofiber matrix [42] (entry 3). Another requirement is to reduce the number of reaction steps and reduce the use of toxic chemical agents to form AgNP/composite polymeric scaffolds. The search for a facile and ecofriendly method is an important task [86]. There is not a noticeable difference in AgNP size and antimicrobial activity for the studied methods; they all reported similar results (Tables 1 and 2). Hence, in our further discussion, we can focus on finding the method possessing the most advantages other than appropriate AgNP size.

Among the compared methods, the direct blending method is the easiest, more accessible, and most commonly used technique to incorporated AgNPs into nanofiber mats [35, 55]. It has been reported that the electrospinning conditions do not affect AgNP bioactivity on microbial cells; however, fiber-matrix encapsulation could reduce it [87]. Despite that, the lack of chemical treatment, irradiation, and thermal treatment made the direct blending method preferable compare to others that consume more time and energy [42] (entry 3). However, it has been described that the mechanical mixing of the AgNPs with the polymeric solution by the direct blending method affects the homogeneity of particle dispersion, facilitating their aggregation, increase viscosity of the polymeric solution, which increase the surface tension, complicating nanofiber formation [66] (entry 13).

Otherwise, comparing the UV-irradiation method with the direct blending, an initial burst release of the AgNPs incorporated into the nanofibers is observed only in the UV method. As mentioned above, this burst release was attributed to the silver ion’s migration from the core to the nanofiber surface [45]. Moreover, in the UV-reduction method, the AgNP diameters are smaller with narrower distribution than other methods. In its turn, the size of AgNPs is an essential parameter of antimicrobial activity [62] (entries 8 and 16). AgNP/PVA nanofibers prepared by the UV irradiation method showed more effectivity against S. aureus than those prepared by the thermal reduction method. In the first case, after 30 minutes of incubation, no bacterial colonies were detected. In comparison, microbial colonies were detected in both treated and untreated AgNP/PVA scaffolds. The authors discussed the last result is ascribed to a higher dispersion diameter resulted from the AgNO₃ reduction from the thermal treatment in the PVA samples [62] (entries 8 and 16).

In the thermal reduction method, the size and spatial distribution of AgNPs can be tuned by varying the AgNO₃ solution concentration. The strategy to immobilizing and manipulating the size of the AgNPs on polymer nanofibers may be extended to other particle systems for various applications such as catalysis, energy, sensing, photonic, and biomedical applications [88]. Unfortunately, this method has been observed that leaching of AgNPs in the initial stage can occur [62] (entries 8 and 16). However, UV irradiation prepared AgNPs are preferred over those loaded on electrospun poly(vinyl alcohol) (PVA) by heat treatment of AgNO₃ for its cytotoxic and microbicidal properties.

The silver mirror reaction method produces different morphologies of Ag nanostructures (quasispheres, wires, rod, right bipyramid, beam, spheres, cube, and octahedron) which cannot be predefined [66], limiting its use for the synthesis of a particular Ag nanostructure. However, to our knowledge, none of the methods compared in this review allow us to design the nanostructure. On the other hand, the silver mirror reaction method is easily controlled, and it takes place at ambient conditions but requires further processing (filtration, purification, and washing) [64] (entry 13). Nanofiber morphology has no significant differences if prepared by SMR or the thermal reduction method [47].

Hence, from the above analysis, we can conclude that all four considered methods presented difficulties in loading AgNPs into the nanofibers, but this does not impact the antimicrobial effectivity of the nanofiber/nanoparticle systems (Table 2). It would be interesting to compare the concentration of AgNO₃ is used and how much Ag is loaded. Still, at the moment, several studies do not evaluate the Ag loaded on the nanofibers, which does not allow to do these correlations.

5. Future Perspectives and Limitations

The properties as porosity, a high surface area/volume ratio, and porous interconnection that can be reached with electrospun polymeric nanofibers make them attractive in different fields [89]. Thus, in the last years, applications for filtering, tissue engineering, wound dressing, drug delivery, and biosensors have been reported using electrospun nanofibers with inorganic particles [90]. However, several variables affect the electrospinning process. Such variables are not yet fully described [48].

The electrospinning method is also limited for parameters that have to be optimized. For example, the large-scale production may present polymer blockage, and electrospinning flux may alter the electric field. It has been reported that this can be fixed using a multirow component in the injection system [91]. Also, it is desired to control nanofiber thickness with collecting devices with different characteristics [9], such as centrifugal electrospinning, or surface-free systems [92]. Other improvement points are precision and reproducibility; for those, the control of temperature and humidity is essential [9]. Finally, stability and mechanical properties can be upgraded with new electrospinning formulations [92–94].

The microbicidal effect of silver has been related to Ag⁺ ion interaction with the cell membrane. It has been described that in AgNPs, Gram-negative bacteria inhibition depends on the concentration associated with cell wall damage [63], but a precise mechanism is still unknown. Still, more studies have to be implemented to investigate the mechanism of the antimicrobial action of the AgNPs. Most importantly, it is necessary to develop the ideal method that does not present any of the troubles mentioned in this review.

The literature data analysis made in the present review indicates that at the present moment, there are numerous publications dedicated to the application of different methods of deposition of AgNPs on nanofibrous scaffolds. Nevertheless, these results are not enough to conclude which method is the most promising for the best control of Ag⁺ ion release. Research where all methods are applied in similar experimental conditions (the same silver nanoparticles type, including stabilizer, particle size, hydrodynamic diameter, and Ag concentration) is necessary to carry out to answer this question.

6. Conclusions

The analysis carried out in this work showed that the methods of AgNP incorporation into the electrospun nanofibers could alter the size of AgNPs, their distribution on the electrospun nanofibers, and their antimicrobial activity. The differences among the four analyzed methods also come from the incorporation time, method difficulty, complexity, and cost of the equipment and solvents used. The latter is not determined by the technique but by the selected nanofiber polymer. Until now, polyacrylonitrile nanofibers are the most frequently chosen system.

We found that the preferred methods are direct blending and UV irradiation. The other two methods (silver mirror reaction and thermal reduction) are less used and less studied. It was found that the UV treatment and thermal reduction methods can manipulate the size and concentration of AgNPs by varying the time of exposition. The direct blending and silver mirror reaction methods cannot control the AgNPs size, and small-sized AgNPs can be incorporated. The silver mirror reaction method’s advantage is that it is a unique technique that can cover large surfaces with AgNPs.

On the other hand, taking into account the presented data, it is proposed that the best method to control the release of Ag⁺ ions from the nanofibrous scaffolds is the SMR method because it already reported that the UV treatment and thermal reduction methods presented a leaching phenomenon after the AgNP loading on the fibers. In the case of the direct blending method, agglomerations of the AgNPs occur affecting controlled release. Moreover, the SRM method provides a homogeneous and well-defined distribution where the AgNP release can be controlled by optimizing the polymeric nanofiber’s degradation.

Conjugation of well-known antimicrobial activity of AgNPs with electrospun nanofibers could take AgNP antimicrobial properties to their highest efficiency. However, up to now, the antimicrobial efficiency of AgNP-loaded nanofibers has not been explored thoughtfully. The mechanisms of antimicrobial action of AgNPs still need to be addressed. Finally, it is recommended to accompany the future performance of four methods discussed here with a comprehensive determination of physicochemical and antimicrobial characteristics of obtained AgNP-loaded nanofibers. This will allow making a more objective comparison of these methods.

Conflicts of Interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

Acknowledgments

The team of Research Institute of Clinical and Experimental Lymрhology–Branch of the Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences thanks to the Ministry of Education and Science of Russia (theme No. 0324-2019-0046). Dr. Alexey Pestryakov thanks Tomsk Polytechnic University Task Program “Science” project FSWW-2020-0011 and Sevastopol State University Task Program “Science” project No. FEFM-2020-0003 and Research grant 42-01-09/169/2021-4.

References

H. Soliman, A. Elsayed, and A. Dyaa, “Antimicrobial activity of silver nanoparticles biosynthesised byRhodotorulasp.strain ATL72,” Egyptian Journal of Basic and Applied Sciences, vol. 5, no. 3, pp. 228–233, 2018.
View at: Publisher Site | Google Scholar
M. Akter, M. T. Sikder, M. M. Rahman et al., “A systematic review on silver nanoparticles-induced cytotoxicity: physicochemical properties and perspectives,” Journal of Advanced Research, vol. 9, pp. 1–16, 2018.
View at: Publisher Site | Google Scholar
H. Singh, J. Du, P. Singh, and T. H. Yi, “Extracellular synthesis of silver nanoparticles by Pseudomonas sp. THG-LS1.4 and their antimicrobial application,” Journal of Pharmaceutical Analysis, vol. 8, no. 4, pp. 258–264, 2018.
View at: Publisher Site | Google Scholar
R. Kalaivani, M. Maruthupandy, T. Muneeswaran et al., “Synthesis of chitosan mediated silver nanoparticles (Ag NPs) for potential antimicrobial applications,” Frontiers in Laboratory Medicine, vol. 2, no. 1, pp. 30–35, 2018.
View at: Publisher Site | Google Scholar
M. Behravan, A. Hossein Panahi, A. Naghizadeh, M. Ziaee, R. Mahdavi, and A. Mirzapour, “Facile green synthesis of silver nanoparticles using _Berberis vulgaris_ leaf and root aqueous extract and its antibacterial activity,” International Journal of Biological Macromolecules, vol. 124, pp. 148–154, 2019.
View at: Publisher Site | Google Scholar
S. Gurunathan, “Rapid biological synthesis of silver nanoparticles and their enhanced antibacterial effects against _Escherichia fergusonii_ and _Streptococcus mutans_,” Arabian Journal of Chemistry, vol. 12, no. 2, pp. 168–180, 2019.
View at: Publisher Site | Google Scholar
C. S. Nunes and P. Philipps-Wiemann, “Chapter 22 - formulation of enzymes,” in Enzymes in Human and Animal Nutrition Principles and Perspectives, C. S. Nunes and B. T. Vikas, Eds., Academic Press, Versailles, France, 1st ed. edition, 2018.
View at: Publisher Site | Google Scholar
F. Khalili Amand and A. Esmaeili, “Investigating the properties of electrospun nanofibers made of hybride polymer containing anticoagulant drugs,” Carbohydrate Polymers, vol. 228, p. 115397, 2020.
View at: Publisher Site | Google Scholar
J. Quirós, K. Boltes, and R. Rosal, “Bioactive applications for electrospun fibers,” Polymer Reviews, vol. 56, no. 4, pp. 631–667, 2016.
View at: Publisher Site | Google Scholar
V. Agarwal, D. Ho, D. Ho et al., “Functional reactive polymer electrospun matrix,” ACS Applied Material and Interfaces, vol. 8, no. 7, pp. 4934–4939, 2016.
View at: Publisher Site | Google Scholar
M. Wang, T. Hai, Z. Feng, D.-G. Yu, Y. Yang, and S. W. Annie Bligh, “The relationships between the working fluids, process characteristics and products from the modified coaxial electrospinning of zein,” Polymers, vol. 11, no. 8, p. 1287, 2019.
View at: Publisher Site | Google Scholar
L. D. Ghosh, A. Jain, N. R. Sundaresan, and K. Chatterjee, “Elucidating molecular events underlying topography mediated cardiomyogenesis of stem cells on 3D nanofibrous scaffolds,” Materials Science and Engineering: C, vol. 88, pp. 104–114, 2018.
View at: Publisher Site | Google Scholar
V. Agarwal, F. M. Wood, F. Mark, and I. K. Swaminathan, “Polymeric nanofibre scaffold for the delivery of a transforming growth factor β1 inhibitor,” Australian Journal of Chemistry, vol. 70, pp. 280–285, 2017.
View at: Publisher Site | Google Scholar
A. Jain, M. Behera, V. Ravi, S. Mishra, N. R. Sundaresan, and K. Chatterjee, “Recapitulating pathophysiology of skeletal muscle diseases in vitro using primary mouse myoblasts on a nanofibrous platform,” Nanomedicine: Nanotechnology, Biology and Medicine, vol. 32, article 102341, 2021.
View at: Publisher Site | Google Scholar
S. Sankar, C. S. Sharma, S. N. Rath, and S. Ramakrishna, “Electrospun nanofibres to mimic natural hierarchical structure of tissues: application in musculoskeletal regeneration,” Journal of Tissue Engineering and Regenerative Medicine, vol. 12, pp. e604–e619, 2018.
View at: Publisher Site | Google Scholar
G. Sandri, S. Rossi, M. C. Bonferoni, C. Caramella, and F. Ferrari, Technologies in Wound Dressing Applications. In Therapeutic Dressings and Wound Healing Applications, J. Boateng, Ed., Wiley, United Kingdom, 2020.
View at: Publisher Site
S. R. K. Meka, S. Kumar Verma, V. Agarwal, K. Chatterjee, and K. Chatterjee, “In situ silication of polymer nanofibers to engineer multi-biofunctional composites,” Chemistry Select, vol. 3, no. 13, pp. 3762–3773, 2018.
View at: Publisher Site | Google Scholar
S. Sankar, C. S. Sharma, S. N. Rath, and S. Ramakrishna, “Electrospun fibers for recruitment and differentiation of stem cells in regenerative medicine,” Biotechnology Journal, vol. 12, no. 12, article 1700263, 2017.
View at: Publisher Site | Google Scholar
L. J. Villarreal-Gómez, R. Vera-Graziano, M. R. Vega-Ríos et al., “Biocompatibility evaluation of electrospun scaffolds of poly (L-lactide) with pure and grafted hydroxyapatite,” Journal of the Mexican Chemical Society, vol. 58, no. 4, pp. 435–443, 2017.
View at: Publisher Site | Google Scholar
L. J. Villarreal-Gómez, J. M. Cornejo-Bravo, R. Vera-Graziano, and D. Grande, “Electrospinning as a powerful technique for biomedical applications: a critically selected survey,” Journal of Biomaterials Science, Polymer Edition, vol. 27, no. 2, pp. 157–176, 2016.
View at: Publisher Site | Google Scholar
E. J. Torres-Martinez, J. M. Cornejo Bravo, A. Serrano Medina, G. L. Pérez González, and L. J. Villarreal Gómez, “A summary of electrospun nanofibers as drug delivery system: drugs loaded and biopolymers used as matrices,” Current Drug Delivery, vol. 15, no. 10, pp. 1360–1374, 2018.
View at: Publisher Site | Google Scholar
G. L. Pérez-González, L. J. Villarreal-Gómez, A. Serrano-Medina, E. J. Torres-Martínez, and J. M. Cornejo-Bravo, “Mucoadhesive electrospun nanofibers for drug delivery systems: applications of polymers and the parameters’ roles,” International Journal of Nanomedicine, vol. Volume 14, no. 1, pp. 5271–5285, 2019.
View at: Publisher Site | Google Scholar
E. J. Torres-Martínez, G. L. Pérez-González, A. Serrano-Medina et al., “Drugs loaded into electrospun polymeric nanofibers for delivery,” Journal of Pharmacy and Pharmaceutical Sciences, vol. 22, no. 1, pp. 313–331, 2019.
View at: Publisher Site | Google Scholar
G. L. Pérez-González, L. J. Villarreal-Gómez, A. Olivas-Sarabia, R. Valdez, and J. M. Cornejo-Bravo, “Development, characterization, and in vitro assessment of multilayer mucoadhesive system containing dexamethasone sodium phosphate,” International Journal of Polymeric Materials and Polymeric Biomaterials, vol. 1, pp. 1–13, 2020.
View at: Publisher Site | Google Scholar
A. Macagnano and F. De Cesare, “17 - Electrospinning: a versatile technology to design biosensors and sensors for diagnostics,” in Electrospun Materials for Tissue Engineering and Biomedical Applications, T. Uyar and B. T. Erich, Eds., Woodhead Publishing, 2017, Electrospun Materials for Tissue Engineering and Biomedical Applications Kny.
View at: Publisher Site | Google Scholar
E. Sapountzi, M. Braiek, J.-F. Chateaux, N. Jaffrezic-Renault, and F. Lagarde, “Recent advances in electrospun nanofiber interfaces for biosensing devices,” Sensors, vol. 17, no. 8, p. 1887, 2017.
View at: Publisher Site | Google Scholar
H.-G. Wang, S. Yuan, D.-L. Ma, X.-B. Zhang, and J.-M. Yan, “Electrospun materials for lithium and sodium rechargeable batteries: from structure evolution to electrochemical performance,” Energy and Environmental Science, vol. 8, no. 6, pp. 1660–1681, 2015.
View at: Publisher Site | Google Scholar
J. G. López-Covarrubias, L. Soto-Muñoz, A. L. Iglesias, and L. J. Villarreal-Gómez, “Electrospun nanofibers applied to dye solar sensitive cells: a review,” Materials, vol. 12, no. 19, p. 3190, 2019.
View at: Publisher Site | Google Scholar
I. Tlili and T. A. Alkanhal, “Nanotechnology for water purification: electrospun nanofibrous membrane in water and wastewater treatment,” Journal of Water Reuse and Desalination, vol. 9, no. 3, pp. 232–248, 2019.
View at: Publisher Site | Google Scholar
H. Chen, M. Huang, Y. Liu, L. Meng, and M. Ma, “Functionalized electrospun nanofiber membranes for water treatment: a review,” Science of the Total Environment, vol. 739, article 139944, 2020.
View at: Publisher Site | Google Scholar
B. M. Sollier, M. Bonne, N. Khenoussi et al., “Synthesis and characterization of electrospun nanofibers of Sr-La-Ce oxides as catalysts for the oxidative coupling of methane,” Industrial & Engineering Chemistry Research, vol. 59, no. 25, pp. 11419–11430, 2020.
View at: Publisher Site | Google Scholar
S. Wen, M. Liang, R. Zou, Z. Wang, D. Yue, and L. Liu, “Electrospinning of palladium/silica nanofibers for catalyst applications,” RSC Advances, vol. 5, no. 52, pp. 41513–41519, 2015.
View at: Publisher Site | Google Scholar
B. Ding, M. Wang, X. Wang, J. Yu, and G. Sun, “Electrospun nanomaterials for ultrasensitive sensors,” Materials Today, vol. 13, no. 11, pp. 16–27, 2010.
View at: Publisher Site | Google Scholar
N. Aliheidari, N. Aliahmad, M. Agarwal, and H. Dalir, “Electrospun nanofibers for label-free sensor applications,” Sensors, vol. 19, no. 16, p. 3587, 2019.
View at: Publisher Site | Google Scholar
J. Yuan, J. Geng, Z. Xing, J. Shen, I.-K. Kang, and H. Byun, “Electrospinning of antibacterial poly (vinylidene fluoride) nanofibers containing silver nanoparticles,” Journal of Applied Polymer Science, vol. 116, no. 2, pp. 668–672, 2009.
View at: Publisher Site | Google Scholar
S. Ren, L. Dong, X. Zhang et al., “Electrospun nanofibers made of silver nanoparticles, cellulose nanocrystals, and polyacrylonitrile as substrates for surface-enhanced raman scattering,” Materials (Basel, Switzerland), vol. 10, no. 1, p. 68, 2017.
View at: Publisher Site | Google Scholar
A. S. Álvarez-Suárez, S. G. Dastager, N. Bogdanchikova et al., “Electrospun fibers and sorbents as a possible basis for effective composite wound dressings,” Micromachines, vol. 11, no. 4, p. 441, 2020.
View at: Publisher Site | Google Scholar
K. E, M. C. K, B. P, T. S. A, and J. C. R. I, “Biocompatible silver nanoparticles/poly(vinyl alcohol) electrospun nanofibers for potential antimicrobial food packaging applications,” Food Packaging and Shelf Life, vol. 21, article 100379, 2019.
View at: Publisher Site | Google Scholar
A. C. Canalli Bortolassi, V. G. Guerra, M. L. Aguiar et al., “Composites based on nanoparticle and pan electrospun nanofiber membranes for air filtration and bacterial removal,” Nanomaterials, vol. 9, no. 12, p. 1740, 2019.
View at: Publisher Site | Google Scholar
J. Wang, L. Zhan, X. Zhang, R. Wu, L. Liao, and J. Wei, “Silver nanoparticles coated poly(L-lactide) electrospun membrane for implant associated infections prevention,” Frontiers in Pharmacology, vol. 11, pp. 1–8, 2020.
View at: Publisher Site | Google Scholar
S. Jin, J. Li, J. Wang et al., “Electrospun silver ion-loaded calcium phosphate/chitosan antibacterial composite fibrous membranes for guided bone regeneration,” International Journal of Nanomedicine, vol. Volume 13, pp. 4591–4605, 2018.
View at: Publisher Site | Google Scholar
Q. Shi, N. Vitchuli, J. Nowak et al., “One-step synthesis of silver nanoparticle-filled nylon 6 nanofibers and their antibacterial properties,” Journal of Materials Chemistry, vol. 21, no. 28, pp. 10330–10335, 2011.
View at: Publisher Site | Google Scholar
A. W. Jatoi, Y. K. Jo, H. Lee et al., “Antibacterial efficacy of poly(vinyl alcohol) composite nanofibers embedded with silver-anchored silica nanoparticles,” Journal of Biomedical Materials Research Part B: Applied Biomaterials, vol. 106, no. 3, pp. 1121–1128, 2018.
View at: Publisher Site | Google Scholar
W. K. Son, J. H. Youk, and W. H. Park, “Antimicrobial cellulose acetate nanofibers containing silver nanoparticles,” Carbohydrate Polymers, vol. 65, no. 4, pp. 430–434, 2006.
View at: Publisher Site | Google Scholar
P.-o. Rujitanaroj, N. Pimpha, and P. Supaphol, “Preparation, characterization, and antibacterial properties of electrospun polyacrylonitrile fibrous membranes containing silver nanoparticles,” Journal of Applied Polymer Science, vol. 116, no. 4, pp. 1967–1976, 2010.
View at: Publisher Site | Google Scholar
D.-N. Phan, N. Dorjjugder, Y. Saito et al., “The synthesis of silver-nanoparticle-anchored electrospun polyacrylonitrile nanofibers and a comparison with as-spun silver/polyacrylonitrile nanocomposite membranes upon antibacterial activity,” Polymer Bulletin, vol. 77, no. 8, pp. 4197–4212, 2020.
View at: Publisher Site | Google Scholar
A. W. Jatoi, I. S. Kim, and Q. Q. Ni, “A comparative study on synthesis of AgNPs on cellulose nanofibers by thermal treatment and DMF for antibacterial activities,” Materials Science and Engineering: C, vol. 98, pp. 1179–1195, 2019.
View at: Publisher Site | Google Scholar
Y. Shi, Y. Li, J. Zhang, Z. Yu, and D. Yang, “Electrospun polyacrylonitrile nanofibers loaded with silver nanoparticles by silver mirror reaction,” Materials Science and Engineering: C, vol. 51, pp. 346–355, 2015.
View at: Publisher Site | Google Scholar
D. Kharaghani, H. Lee, T. Ishikawa, T. Nagaishi, S. H. Kim, and I. S. Kim, “Comparison of fabrication methods for the effective loading of Ag onto PVA nanofibers,” Textile Research Journal, vol. 89, no. 4, pp. 625–634, 2019.
View at: Publisher Site | Google Scholar
P. Li, M. Zhang, X. Liu, Z. Su, and G. Wei, “Electrostatic assembly of platinum nanoparticles along electrospun polymeric nanofibers for high performance electrochemical sensors,” Nanomaterials, vol. 7, no. 9, p. 236, 2017.
View at: Publisher Site | Google Scholar
A. C. C. Bortolassi, S. Nagarajan, B. de Araújo Lima et al., “Efficient nanoparticles removal and bactericidal action of electrospun nanofibers membranes for air filtration,” Materials Science and Engineering: C, vol. 102, pp. 718–729, 2019.
View at: Publisher Site | Google Scholar
E. A. Skomorokhova, T. P. Sankova, I. A. Orlov et al., “Size-dependent bioactivity of silver nanoparticles: antibacterial properties, influence on copper status in mice, and whole-body turnover,” Nanotechnology, Science and Applications, vol. 13, pp. 137–157, 2020.
View at: Google Scholar
Q. Shi, N. Vitchuli, J. Nowak et al., “Durable antibacterial Ag/polyacrylonitrile (Ag/PAN) hybrid nanofibers prepared by atmospheric plasma treatment and electrospinning,” European Polymer Journal, vol. 47, no. 7, pp. 1402–1409, 2011.
View at: Publisher Site | Google Scholar
Z. Xu, S. Mahalingam, J. L. Rohn, G. Ren, and M. Edirisinghe, “Physio-chemical and antibacterial characteristics of pressure spun nylon nanofibres embedded with functional silver nanoparticles,” Materials Science and Engineering C, vol. 56, pp. 195–204, 2015.
View at: Publisher Site | Google Scholar
Y. Gao, Y. Bach Truong, Y. Zhu, and I. Louis Kyratzis, “Electrospun antibacterial nanofibers: production, activity, andin vivoapplications,” Journal of Applied Polymer Science, vol. 131, no. 18, pp. 9041–9053, 2014.
View at: Publisher Site | Google Scholar
S. K. Bhullar, D. G. Ruzgar, G. Fortunato et al., “A facile method for controlled fabrication of hybrid silver nanoparticle-poly(-caprolactone) fibrous constructs with antimicrobial properties,” Journal of Nanosciences and Nanotechnology, vol. 19, no. 11, pp. 6949–6955, 2019.
View at: Publisher Site | Google Scholar
R. Wang, Z. Wang, S. Lin et al., “Green fabrication of antibacterial polymer/silver nanoparticle nanohybrids by dual-spinneret electrospinning,” RSC Advances, vol. 5, no. 50, pp. 40141–40147, 2015.
View at: Publisher Site | Google Scholar
N. Tucker, K. Hofman, J. Stanger, M. Staiger, N. A. Hamid, and P. L. Torres, “The history of the science and technology of electrospinning from 1600 to 1995,” in International Symposium on New Frontiers in Fiber Materials Science, Conference Proceedings, pp. 63–73, Charleston, South Carolina, USA, 2011.
View at: Google Scholar
M. He, M. Chen, Y. Dou et al., “Electrospun silver nanoparticles-embedded feather Keratin/Poly(vinyl alcohol)/Poly(ethylene oxide) antibacterial composite nanofibers,” Polymers, vol. 12, no. 2, p. 305, 2020.
View at: Publisher Site | Google Scholar
T. Nuge, K. Y. Tshai, S. S. Lim, N. Nordin, and M. E. Hoque, “Preparation and characterization of CU-, FE-, AG-, ZN- and NI- doped gelatin nanofibers for possible applications in antibacterial nanomedicine,” Journal of Engineering Science and Technology, vol. 12, no. 1, pp. 68–81, 2017.
View at: Google Scholar
S. Liang, G. Zhang, J. Min, J. Ding, and X. Jiang, “Synthesis and antibacterial testing of silver/poly (ether amide) composite nanofibers with ultralow silver content,” Journal of Nanomaterials, vol. 2014, Article ID 684251, 10 pages, 2014.
View at: Publisher Site | Google Scholar
S. Lin, R. Z. Wang, Y. Yi et al., “Facile and green fabrication of electrospun poly(vinyl alcohol) nanofibrous mats doped with narrowly dispersed silver nanoparticles,” International Journal of Nanomedicine, vol. 9, no. 1, pp. 3937–3947, 2014.
View at: Publisher Site | Google Scholar
A. Chaudhary, A. Gupta, R. B. Mathur, and S. R. Dhakate, “Effective antimicrobial filter from electrospun polyacrylonitrile-silver composite nanofibers membrane for Conductive Environments,” Advanced Materials Letters, vol. 5, no. 10, pp. 562–568, 2014.
View at: Publisher Site | Google Scholar
D. Y. Lee, K.-H. Lee, B.-Y. Kim, and N.-I. Cho, “Silver nanoparticles dispersed in electrospun polyacrylonitrile nanofibers via chemical reduction,” Journal of Sol-Gel Science and Technology, vol. 54, no. 1, pp. 63–68, 2010.
View at: Publisher Site | Google Scholar
Y. Liu, D. Chunnuan, X. Lv, Z. Jia, S. Sun, and Y. Jianxiang, “Synthesis of silver nanofiber transparent electrodes by silver mirror reaction with electrospun nanofiber template,” Composite Interfaces, vol. 26, pp. 1–10, 2021.
View at: Publisher Site | Google Scholar
M. Rycenga, C. M. Cobley, J. Zeng et al., “Controlling the synthesis and assembly of silver nanostructures for plasmonic applications,” Chemical Reviews, vol. 111, no. 6, pp. 3669–3712, 2011.
View at: Publisher Site | Google Scholar
C. Chen, Y. Tang, B. Vlahovic, and F. Yan, “Electrospun polymer nanofibers decorated with noble metal nanoparticles for chemical sensing,” Nanoscale Research Letters, vol. 12, no. 1, p. 451, 2017.
View at: Publisher Site | Google Scholar
M. W. Munir and U. Ali, “Classification of electrospinning methods,” in Nanorods and Nanocomposites, M. S. Ghamsari and S. Dhara, Eds., IntechOpen, 1st ed. edition, 2020.
View at: Google Scholar
C.-N. Lok, C.-M. Ho, R. Chen et al., “Silver nanoparticles: partial oxidation and antibacterial activities,” JBIC Journal of Biological Inorganic Chemistry, vol. 12, no. 4, pp. 527–534, 2007.
View at: Publisher Site | Google Scholar
H.-T. Chen, H.-L. Lin, I.-G. Chen, and C. Kuo, “Conducting silver networks based on electrospun Poly(Methyl methacrylate) and silver trifluoroacetate,” ACS Applied Materials & Interfaces, vol. 7, no. 18, pp. 9479–9485, 2015.
View at: Publisher Site | Google Scholar
A. Kędziora, M. Speruda, E. Krzyżewska, J. Rybka, A. Łukowiak, and G. Bugla-Płoskońska, “Similarities and differences between silver ions and silver in nanoforms as antibacterial agents,” International Journal of Molecular Sciences, vol. 19, no. 2, p. 444, 2018.
View at: Publisher Site | Google Scholar
N. Durán, M. Durán, M. B. de Jesus, A. B. Seabra, W. J. Fávaro, and G. Nakazato, “Silver nanoparticles: a new view on mechanistic aspects on antimicrobial activity,” Nanomedicine: Nanotechnology, Biology, and Medicine, vol. 12, no. 3, pp. 789–799, 2016.
View at: Publisher Site | Google Scholar
T. C. Dakal, A. Kumar, R. S. Majumdar, and V. Yadav, “Mechanistic basis of antimicrobial actions of silver nanoparticles,” Frontiers in Microbiology, vol. 7, pp. 1–17, 2016.
View at: Publisher Site | Google Scholar
S. Zhang, Y. Tang, and B. Vlahovic, “A review on preparation and applications of silver-containing nanofibers,” Nanoscale Research Letters, vol. 11, no. 1, pp. 80–88, 2016.
View at: Publisher Site | Google Scholar
H. Lv, S. Cui, Q. Yang et al., “AgNPs-incorporated nanofiber mats: relationship between AgNPs size/content, silver release, cytotoxicity, and antibacterial activity,” Materials Science and Engineering C, vol. 118, p. 111331, 2021.
View at: Publisher Site | Google Scholar
B. Le Ouay and F. Stellacci, “Antibacterial activity of silver nanoparticles: a surface science insight,” Nano Today, vol. 10, no. 3, pp. 339–354, 2015.
View at: Publisher Site | Google Scholar
D. Liang, Z. Lu, H. Yang, J. Gao, and R. Chen, “Novel asymmetric wettable AgNPs/chitosan wound dressing: in vitro and in vivo evaluation,” ACS Applied Materials & Interfaces, vol. 8, no. 6, pp. 3958–3968, 2016.
View at: Publisher Site | Google Scholar
D. Kharaghani, Y. Kee Jo, M. Q. Khan, Y. Jeong, H. J. Cha, and I. S. Kim, “Electrospun antibacterial polyacrylonitrile nanofiber membranes functionalized with silver nanoparticles by a facile wetting method,” European Polymer Journal, vol. 108, pp. 69–75, 2018.
View at: Publisher Site | Google Scholar
K. Zawadzka, K. Kądzioła, A. Felczak et al., “Surface area or diameter - which factor really determines the antibacterial activity of silver nanoparticles grown on TiO2coatings?” New Journal of Chemistry, vol. 38, no. 7, pp. 3275–3281, 2014.
View at: Publisher Site | Google Scholar
Z. M. O. Rzayev, D. Erdönmez, K. Erkan, M. Şimşek, and U. Bunyatova, “Functional copolymer/organo-MMT nanoarchitectures. XXII. Fabrication and characterization of antifungal and antibacterial poly vinyl alcohol-co-vinyl acetate/ODA-MMT/AgNPs nanofibers and nanocoatings by e-spinning and c-spinning methods,” International Journal of Polymeric Materials and Polymeric Biomaterials, vol. 64, no. 5, pp. 267–278, 2015.
View at: Publisher Site | Google Scholar
A. Ivask, A. ElBadawy, C. Kaweeteerawat et al., “Toxicity mechanisms in Escherichia coli vary for silver nanoparticles and differ from ionic silver,” ACS Nano, vol. 8, no. 1, pp. 374–386, 2014.
View at: Publisher Site | Google Scholar
A. Ivask, I. Kurvet, K. Kasemets et al., “Size-dependent toxicity of silver nanoparticles to bacteria, yeast, algae, crustaceans and mammalian cells in vitro,” PLoS One, vol. 9, no. 7, article e102108, 2014.
View at: Publisher Site | Google Scholar
H. Palza, “Antimicrobial polymers with metal nanoparticles,” International Journal of Molecular Sciences, vol. 16, no. 1, pp. 2099–2116, 2015.
View at: Publisher Site | Google Scholar
I. L. Hsiao, Y. K. Hsieh, C. F. Wang, I. C. Chen, and Y. J. Huang, “Trojan-horse mechanism in the cellular uptake of silver nanoparticles verified by direct intra- and extracellular silver speciation analysis,” Environmental Science and Technology, vol. 49, no. 6, pp. 3813–3821, 2015.
View at: Publisher Site | Google Scholar
J. L. Castro-Mayorga, M. J. Fabra, L. Cabedo, and J. M. Lagaron, “On the use of the electrospinning coating technique to produce antimicrobial polyhydroxyalkanoate materials containing in situ-stabilized silver nanoparticles,” Nanomaterials, vol. 7, no. 1, p. 4, 2017.
View at: Publisher Site | Google Scholar
B. Pant, M. Park, and S. J. Park, “One-step synthesis of silver nanoparticles embedded polyurethane nano-fiber/net structured membrane as an effective antibacterial medium,” Polymers, vol. 11, no. 7, p. 1185, 2019.
View at: Publisher Site | Google Scholar
S. Zohoori, L. Karimi, and S. Ayaziyazdi, “A novel durable photoactive nylon fabric using electrospun nanofibers containing nanophotocatalysts,” Journal of Industrial and Engineering Chemistry, vol. 20, no. 5, pp. 2934–2938, 2014.
View at: Publisher Site | Google Scholar
S. Xiao, W. Xu, H. Ma, and X. Fang, “Size-tunable Ag nanoparticles immobilized in electrospun nanofibers: synthesis, characterization, and application for catalytic reduction of 4-nitrophenol,” RSC Advances, vol. 2, no. 1, pp. 319–327, 2012.
View at: Publisher Site | Google Scholar
J. Xue, J. Xie, W. Liu, Y. Xia, and D. Holland, “Electrospun nanofibers: new concepts, materials, and applications,” Accounts of Chemical Research, vol. 50, no. 8, pp. 1976–1987, 2017.
View at: Publisher Site | Google Scholar
S. Yu and N. V. Myung, “Minimizing the diameter of electrospun polyacrylonitrile (PAN) nanofibers by design of experiments for electrochemical application,” Electroanalysis, vol. 30, no. 10, pp. 2330–2338, 2018.
View at: Publisher Site | Google Scholar
J. Lev, M. Holba, M. Došek, L. Kalhotka, P. Mikula, and D. Kimmer, “A novel electrospun polyurethane nanofibre membrane – production parameters and suitability for wastewater (WW) treatment,” Water Science and Technology, vol. 69, no. 7, pp. 1496–1501, 2014.
View at: Publisher Site | Google Scholar
G. G. Chase, J. S. Varabhas, and D. H. Reneker, “New methods to electrospin nanofibers,” Journal of Engineered Fibers and Fabrics, vol. 6, no. 3, pp. 32–38, 2011.
View at: Publisher Site | Google Scholar
R. Sridhar, S. Sundarrajan, A. Vanangamudi, G. Singh, T. Matsuura, and S. Ramakrishna, “Green processing mediated novel polyelectrolyte nanofibers and their antimicrobial evaluation,” Macromolecular Materials and Engineering, vol. 299, no. 3, pp. 283–289, 2014.
View at: Publisher Site | Google Scholar
B. Pant, M. Park, G. P. Ojha, D.-U. Kim, H.-Y. Kim, and S.-J. Park, “Electrospun salicylic acid/polyurethane composite nanofibers for biomedical applications,” International Journal of Polymeric Materials and Polymeric Biomaterials, vol. 67, no. 12, pp. 739–744, 2018.
View at: Publisher Site | Google Scholar

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