Gold Nanoparticles and Nanocomposites in Clinical Diagnostics Using Electrochemical Methods

Table 1

Expected applications of AuNPs in various areas.

Serial number	Fields	Applications
1	Electronics	AuNPs are considered for use as conductors from printable inks to electronic chips. As the world of electronics becomes smaller in size, nanoparticles are important components in the electronic chip design. AuNPs are being used to connect resistors, conductors, and other elements of electronic devices [20].
2	Photodynamic therapy	Photodynamic therapy that is a mode of treatment by laser light at a particular wavelength is combined with exogenous chromophores to accomplish a therapeutic effect. Near-IR absorbing AuNPs (including Au nanoshells and nanorods) produce heat when excited by light at wavelengths from 700 to 800 nm. This enables these nanoparticles to destroy targeted tumors. When light is applied to a tumor-containing AuNPs, the particles rapidly heat up, killing tumor cells in a treatment also known as hyperthermia therapy [21].
3	Therapeutic agent delivery	Therapeutic agents can be covered with AuNPs. Whereas the NIR-resonant Au/silica nanoshells used in therapeutic and imaging applications have an average diameter of 120–140 nm [22].
4	Sensors	AuNPs can be used in different sensors. For example, a colorimetric sensor based on AuNPs can identify if foods are suitable for consumption [23]. Other methods, such as surface-enhanced Raman spectroscopy, exploit AuNPs as substrates to enable the measurement of vibrational energies of chemical bonds. This strategy could also be used for the detection of proteins, pollutants, and other molecules label-free [24].
5	Probes	AuNPs also scatter light and can create an array of interesting colors under dark-field microscopy. The scattered colors of AuNPs are currently used for biological imaging. Also, AuNPs are relatively dense, allowing them helpful as probes for transmission electron microscopy [25].
6	Diagnostics	AuNPs are also used to detect biomarkers in clinical and medical diagnosis. They are also useful in the lateral flow immunoassays, a common household example being the home pregnancy test [26].
7	Catalysis	AuNPs are used as catalysts in a number of chemical reactions [27]. The surface of AuNPs can be used for oxidation or reduction of certain chemicals. AuNPs are being developed for fuel cell applications. These technologies would be useful in the automotive and display industry.
8	Fluorescence properties	Fluorescence-based detection techniques are among the most highly sensitive and popular biological tests in the clinical analysis. AuNPs show outstanding behavior of antiphoto bleaching under the presence of powerful light [28].