Treatment of dandruff condition usually involves use of antidandruff shampoos containing antifungal agents. Different antifungal agents show variable clinical efficacy based on their cutaneous distribution and bioavailability. Using stimulated Raman scattering (SRS), we mapped the distribution of unlabeled low-molecular weight antifungal compounds zinc pyrithione (ZnPT) and climbazole (CBZ) on the surface of intact porcine skin with cellular precision. SRS has sufficient chemical selectivity and sensitivity to detect the agents on the skin surface based on their unique chemical motifs that do not occur naturally in biological tissues. Moreover, SRS is able to correlate the distribution of the agents with the morphological features of the skin using the CH2 stretch mode, which is abundant in skin lipids. This is a significant strength of the technique since it allows the microscopic accumulation of the agents to be correlated with physiological features and their chemical environment without the use of counter stains. Our findings show that due to its lower solubility, ZnPT coats the surface of the skin with a sparse layer of crystals in the size range of 1 to 4 μm. This is consistent with the current understanding of the mode of action of ZnPT. In contrast, CBZ being more soluble and hydrophobic resulted in diffuse homogeneous distribution. It predominantly resided in microscopic lipid-rich crevasses and penetrated up to 60 μm into the infundibular spaces surrounding the hair shaft. The ability of the SRS to selectively map the distribution of agents on the skin’s surface has the potential to provide insight into the mechanisms underpinning the topical application of antifungal or skin-active agents that could lead to the rational engineering of enhanced formulations.
Recent advances in pharmaceutical nanotechnology have enabled the development of nano-particulate medicines with enhanced drug performance. Although the fate of these nano-particles can be macroscopically tracked in the body (e.g. using radio-labeling techniques), there is little information about the sub-cellular scale mechanistic processes underlying the particle-tissue interactions, or how these interactions may correlate with pharmaceutical efficacy. To rationally engineer these nano-particles and thus optimize their performance, these mechanistic interactions must be fully understood. Coherent Anti-Stokes Raman scattering (CARS) microscopy provides a label-free means for visualizing biological samples, but can suffer from a strong non-resonant background in samples that are prepared using aldehyde-based fixatives. We demonstrate how formalin fixative affects the detection of polymeric nanoparticles within kidneys following oral administration using CARS microscopy, compared with samples that were snap-frozen. These findings have implications for clinical applications of CARS for probing nanoparticle distribution in tissue biopsies.
Fungi have been found to be an underlying cause of 70% of all plant and animal extinctions caused by infectious
diseases. Fungal infections are a growing problem affecting global health, food production and ecosystems. Lipid
metabolism is a promising target for antifungal drugs and since effective treatment of fungal infections requires a better
understanding of the effects of antifungal agents at the cellular level, new techniques are needed to investigate this
problem.
Recent advances in nonlinear microscopy allow chemically-specific contrast to be obtained non-invasively from intrinsic
chemical bonds within live samples using advanced spectroscopy techniques probing Raman-active resonances. We
present preliminary data using Stimulated Raman Scattering (SRS) microscopy as a means to visualise lipid droplets
within individual living fungi by probing Raman resonances of the CH stretching region between 2825cm-1 and
3030cm-1.
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