Enhanced Transdermal Delivery of Rhein In Vitro Using a Dissolving Microneedle Patch

Transdermal delivery presents an attractive option for rhein (RN) to circumvent the undesirable laxative effect associated with oral administration. However, the stratum corneum (SC) acts primarily as a barrier against RN permeation across the skin. Thus, dissolving microneedle patches (DMNPs) serve as an effective tool for enhancing skin permeation by bypassing the SC. This study focused on preparing a RN-loaded DMNP and evaluating its efficacy in enhancing transdermal RN delivery. The DMNP was fabricated from a 10% (w/w) aqueous polyvinyl alcohol solution using the micro-molding technique. The efficiency of the prepared DMNP in delivering RN across neonatal porcine skin was compared in vitro with a film as a control. The DMNP effectively pierced a skin-simulating Parafilm® M stack and neonatal porcine skin. The DMNP completely dissolved within 30 min after skin insertion. A 1 cm × 1 cm piece of the DMNP contained 96.5 ± 2.0 μg of RN. In a light-protected drug release study, the DMNP released 79.44 ± 2.0% of RN within 8 h and then achieved approximately 100% of RN release at 24 h. The in vitro permeation study showed that the DMNP exhibited a significantly greater RN permeation than the film. The amount of RN permeated at 24 h from the DMNP was 31.6 ± 2.4 μg/cm2, corresponding to a flux of 1.24 ± 0.10 μg/cm2/h, whereas RN permeation from the film was undetectable. Therefore, the DMNP exhibits promising potential for enhancing transdermal RN delivery in vitro and could be used in further in vivo studies.