Stem cell-integrated microneedles for regenerative therapy

Microneedles, hundreds of micrometers in length, have been a focal point in transdermal drug delivery research for decades. Their ability to effectively penetrate skin barriers, such as the stratum corneum and epidermis, while minimizing tissue damage and patient discomfort has driven their extensive development. Recently, there has been a surge in the development of specialized microneedles designed for more accurate and rapid drug delivery, with some designs incorporating detachable features. These detachable microneedles, whether the entire structure or a portion thereof, are engineered to separate from the substrate after drug delivery. Various biocompatible materials, particularly hydrogels, have been employed in these designs, significantly enhancing the biocompatibility of microneedles. Beyond drug delivery, there is emerging research on integrating cells into microneedles. This encompasses efforts ranging from culturing cells on the microneedle substrate to deliver bioactive molecules secreted by the cells, to directly delivering stem cells to target sites through innovative microneedle designs. This review delves into the exploration of microneedle technologies capable of cell delivery for regenerative therapy, offering insights into the future directions of microneedle technology in biomedical applications.