Conventional administration methods have problems including low bioavailability, complex operation process, and discomfort of patients with fear of needles. Transdermal delivery can avoid these problems, whereas most drugs are difficult to directly penetrate the skin cuticle and reach the diseased site. Microneedling is an emerging method of local drug delivery, enabling the drug penetration through the stratum corneum of the skin in a minimally invasive manner and delivering the drug directly to the diseased site, thereby improving the treatment effect. Stimuli-responsive microneedles have attracted much attention because of the spatiotemporal controllability, high drug delivery efficiency, and mild potential side effects. This review introduced the commonly used materials and various types of stimuli-responsive microneedles and the drug release mechanisms. In addition, this paper expounded the biomedical applications of stimuli-responsive microneedles as drug delivery systems in response to different stimuli and discusses the challenges and potential solutions for stimuli-responsive microneedles.
Needles ; Drug Delivery Systems/instrumentation* ; Microinjections/instrumentation* ; Humans ; Administration, Cutaneous