Human hair follicle: reservoir function and selective targeting

Area of Science:

• Dermatology and Pharmaceutical Sciences
• Cutaneous Drug Delivery Research

Background:

• Topical compound penetration occurs through the stratum corneum, skin appendages, and hair follicles.
• The hair follicle, particularly the infundibulum, serves as a reservoir and barrier disruptor, facilitating deeper skin penetration.
• Targeted delivery to hair follicle compartments offers potential for localized treatment of inflammatory conditions with minimized systemic effects.

Purpose of the Study:

• To explore the role of hair follicles in topical compound penetration.
• To identify factors influencing follicular drug delivery and retention.
• To discuss methods for studying follicular penetration pathways.

Main Methods:

• Utilizing in vitro and in vivo techniques to investigate hair follicle structure and penetration.
• Methods include cyanoacrylate skin surface stripping, confocal microscopy, and cyanoacrylate scalp follicle biopsy.
• Analysis of factors such as molecule/particle size, polarity, and preparation type influencing delivery.

Main Results:

• Hair follicles offer significant pathways for topical compound penetration into the skin.
• The infundibulum acts as a reservoir, influencing compound delivery and retention.
• Factors like particle size and polarity are critical for controlling penetration depth and storage time.

Conclusions:

• Hair follicles are crucial targets for topical drug delivery systems.
• Designing effective delivery systems requires consideration of follicular anatomy, cyclical activity, and physicochemical properties.
• Further research is needed on drug release mechanisms from nanoparticles for optimized follicular delivery.