Enhanced follicular penetration of antiseptics using nanocrystals – investigated via novel hair follicle content removal method

Effective skin disinfection is critical in preventing surgical-site infections (SSIs), particularly during long surgical procedures where bacteria from hair follicles can continuously emerge onto the skin surface and recolonize it. To enhance follicular disinfection, this study investigates the intrafollicular delivery of isopropanol, an antiseptic agent, dissolved in the outer phase of a suspension of specifically-engineered hesperetin nanocrystals. To accurately quantify follicular penetration, we analyzed both intrafollicular concentration and penetration depth. For the former, we developed the 'hair plucking method', a novel technique that extracts whole hair follicles, comprising the hairs and their associated follicular epidermis. Using porcine ear skin as an ex vivo model, we applied two formulations: an isopropanol-based hesperetin nanocrystals suspension, and an isopropanol-based particle-free control, while a third skin area remained untreated and served as a baseline. Rhodamine 6G, a fluorescent dye, was incorporated into both formulations to track penetration. Fluorescence spectroscopy analysis of fully plucked hair follicles was employed to measure the intrafollicular concentration of the dyed antiseptic, while laser scanning microscopy of cryohistological hair follicle sections was employed to measure its penetration depth. The results showed that the nanocrystals increased intrafollicular concentration of the antiseptic formulation by over 85 % (p < 0.05) and its penetration depth by approximately 38 % (p < 0.001), demonstrating enhanced follicular delivery and validating the efficacy of the hair plucking method. These findings highlight the potential of nanoparticle-based formulations to improve surgical antisepsis and reduce SSI risks, contributing to safer and more effective preoperative disinfection strategies.