Recent advances in follicular drug delivery of nanoparticles

ABSTRACT

Introduction: The improvement of percutaneous absorption represents a clear dermatopharmaceutical aim. Recently, the hair follicle was recognized to be an important penetration pathway. Especially nanoparticles show an enhanced intrafollicular penetration and can be utilized to target specific cell populations within the hair follicle.

Areas covered: The present review briefly summarizes the recent advances in follicular drug delivery of nanoparticles. Moreover, the particularities of the hair follicle as a penetration pathway are summarized which include its structure and specific barrier properties. Recently, the mechanism of the follicular penetration process has been clarified.

In the meantime, different strategies have been developed to successfully improve follicular drug delivery of nanoparticles. One approach is to equip the nanocarriers with a triggered release system enabling them to release their drug load at the right time and place.

Expert opinion: Follicular drug delivery with smart nanocarrier-based drug delivery systems represents a promising approach to increase the percutaneous absorption of topically applied substances. Although technical achievements and efficacy proofs concerning an increased penetration of substances are already available, the practical implementation into clinical application still represents an additional challenge and should be in the focus of interest in future research.

KEYWORDS:

• Hair follicle
• nanocarrier
• penetration pathway
• topical drug delivery
• triggered release

Article highlights

• Hair follicles are an important penetration pathway for topically applied substances

• Up to now, there is no clear evidence that nanoparticles >20–40 nm are able to overcome the intact skin barrier

• Nanoparticles show a deep penetration into the hair follicles

• The follicular penetration process seems to be predominantly mechanically driven by hair movement

• Increasing the skin or systemic bioavailability can be realized by using nanocarriers which transport the drug of interest into the hair follicles where it is released either continuously or by an endogenous or exogenous trigger signal and then overcomes the hair follicle barrier independently

• Translation of innovative nanoparticle-based drug delivery systems into clinical applications still represents a challenge

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Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was funded by the Foundation of Skin Physiology of the Donor Association for Science and Humanities.