(688f) Rapid Intradermal Drug Delivery Using Separable Microneedles for Bolus and Controlled Release

Current transdermal drug delivery based on passive diffusion using topical formulations or non-invasive patches requires a long dosing time and is limited to chemical compounds less than approximately 500 Da that are highly lipophilic due to the presence of skin's barrier layer of stratum corneum. To efficiently deliver a wider range of therapeutics including hydrophilic drugs and macromolecules, we have developed a novel type of microneedle called separable microneedles that can administer drug quickly across the stratum corneum and into the superficial layer of skin. The microneedles are featured by sharp tips encapsulating drug (?arrowheads?) and an array backing connected by spacers (?shafts?). Upon insertion into skin, the arrowhead tips quickly become separated from the backing shafts. As a result, the tips are left embedded within the skin for subsequent release of drug while the backing can be removed and discarded. Depending on the microneedle tip materials used for drug encapsulation, the intradermal drug release can either be bolus or controlled release.

The result has shown that our model drug sulforhodamine B encapsulated in dissolvable tips made of polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) was released and dispersed quickly in pig cadaver skin as the tips dissolved and disintegrated. In contrast, biodegradable tips made of poly(lactic-co-glycolic acid) (PLGA) encapsulating sulforhodamine B remained embedded within the skin and slowly released the encapsulated drug.

We envision that intradermal drug delivery using separable microneedles can serve as an alternative drug delivery method for dual purposes: either as an invasive bolus injection or implantation of materials containing therapeutics for controlled release. All in all, using separable microneedles can potentially enhance patient compliance for less invasive injection and less frequent dosing via the skin.