The Human Stratum Corneum Prevents Small Gold Nanoparticle Penetration and Their Potential Toxic Metabolic Consequences
Figure 2
(a)–(e) Gold nanoparticle penetration in cryosectioned skin using MPT-FLIM and (f) gold nanoparticle luminescence skin depth profile. Cross-sectional images of the skin showing the superficial stratum corneum, viable epidermis and upper dermis. Images are pseudocoloured based on signal (skin autofluorescence 0–95% and AuNPs 95–100% signal). Both the saline (a) and sodium citrate buffer (b) controls show no AuNP signal. The 10 nm (c), 30 nm (d), and 60 nm (e) AuNP-treated groups resulted in high amounts of AuNP signal in the stratum corneum with no signal in the lower layers. High signal was detected in the upper dermis corresponding to second harmonic generation of dermal collagen. Scale bar indicates 50 μm. Data from MPT-FLIM depth series (stratum corneum to basale of excised human skin) were processed to quantify gold nanoparticle luminescence intensity as a function of depth in non-furrow containing regions (i.e., AuNP penetration) (f). The top of the skin is at −20 μm, whereas 0 μm is the start of viable epidermis (stratum granulosum). These data were stacked from a depth series of en face images. Color bar, blue to red indicates 0–100%.
