Topical and Transdermal Drug Delivery: From Simple Potions to Smart Technologies

Abstract

This overview on skin delivery considers the evolution of the principles of percutaneous absorption and skin products from ancient times to today. Over the ages, it has been recognised that products may be applied to the skin for either local or systemic effects. As our understanding of the anatomy and physiology of the skin has improved, this has facilitated the development of technologies to effectively and quantitatively deliver solutes across this barrier to specific target sites in the skin and beyond. We focus on these technologies and their role in skin delivery today and in the future.

Keywords: History; follicular transport; microneedles; minimally invasive; nanotechnology; physical enhancement; skin delivery; stratum corneum; targeted delivery; transdermal technologies; wearable devices..

Fig. (1)

A. Approved and underdevelopment transdermal drugs and their recommended site of application. B. Close-up of human skin and various sites and targets within the skin.

Fig. (2)

Diagrammatic illustration of human skin. Barriers, sites of action and drug delivery opportunities.

Fig. (3)

Nanodelivery systems for topical and transdermal drug delivery. (Adapted with permission from Roberts et al. 2016 [26]).

Fig. (4)

Physical penetration enhancement techniques.

Fig. (5)

Anti-influenza immunogenicity of Fluvax^® 2010 coated Nanopatches applied to the buccal mucosa. (A) Total serum IgG responses at various times after immunisation and boost. (B) IgA responses in samples extracted from faeces, female reproductive tract and nasal passages after the final immunisation (Day 70). (C) Haemagglutination inhibition titres against the A/Perth/16/2009 like influenza strain in serum collected 21 days after the initial immunisation. The black line at a HI titre of 40 represents the accepted minimum that correlates with protection in humans. In all panels bars represent the mean and standard deviation from the mean are shown. Significance of p ≤ 0.01 (***), p = 0.01-0.05 (**) or p = 0.05-0.1 (*) is indicated. In all immune studies n = 5 animals were used per group. Reproduced with permission from [167].

Fig. (6)

a) The ‘smart insulin patch’ effectively regulates blood glucose levels by sensing hypoxia in the local microenvironment. b) A sophisticated system to sense glucose, pH, humidity and temperature by absorbing sweat and release antidiabetic drug upon trigger.