Microneedles for Ocular Drug Delivery and Targeting: Challenges and Opportunities

Microneedle array systems for long-acting drug delivery

“…Upon application to the skin, the microprojections penetrate the epidermal layer and deliver or implant the compounds within the dermis below, wherein lies a high density of vascular and lymphatic beds available to absorb the drug systemically [4][5][6]. Besides the application of MNs for intradermal drug delivery, they have also been used for ocular drug delivery, as well as administrations of vaccines and DNA delivery [7][8][9]. MNs have been vastly exploited to enhance penetration of small and macromolecules through the skin or the ocular tissues in a pain-free manner with the potential capability of self-application.…”

Potential of Microneedle Systems for COVID-19 Vaccination: Current Trends and Challenges

“…Microneedle separation into the skin was shown by Kim et al [ 254 ] to be mediated by hydrogel swelling in reaction to contact with bodily fluid after the needles were introduced into the skin [ 243 , 280 , 281 ]. The hydrogel particles immediately absorbed water, causing the microneedles to break owing to the differential volume expansion between the needle–matrix polymer and the hydrogel particles [ 253 , 282 , 283 ]. The enlarged particles completely disintegrated the microneedles, leaving the microneedle tips in the skin of a porcine cadaver in vitro and a hairless mouse in vivo [ 284 , 285 , 286 ].…”