Dissolving Microneedle Array Patches Manufactured By Solvent Casting Technique and Essential Characterization of Microneedle-Based Biomedical Devices

Microneedle-based technology has revolutionized the field of skin and transdermal delivery research and is considered nowadays as the most straightforward approach to administering drugs through the skin. Microneedle Array Patches (MAPs) success is mainly due to their ability to nullify the skin barrier function that opposes the entrance of topically applied drugs by painless piercing the stratum corneum layer. Dissolving MAPs (DMAPs) stand out among other MAPs-based device types due to the biocompatibility of their constituent materials, the possibility of self-administration by patients, and the absence of sharp waste generated after use. DMAPs are usually made of polymeric materials that redisperse upon insertion into the skin when in touch with interstitial fluids, releasing their cargo. At the bench level, DMAPs are commonly manufactured using the solvent casting method, which involves the use of negative master molds of the desired MAPs shape and length, onto which drug-loaded polymeric dispersions are cast. They are subsequently forced to fill the mold's cavities by the application of a centrifugal force or positive pressure. After drying, DMAPs become solid and are peeled off from the master molds, and they routinely undergo various characterization studies before use. These assays typically comprise the study of the mechanical properties of DMAPs, determination of residual water content, ex vivo capacity to penetrate the skin structure, drug release performance, and in vitro assessment of biocompatibility.