Novel microneedle patches for transdermal delivery of AP39, a hydrogen sulphide donor, in the treatment of scenarios mimicking neurological disorders

Purpose: Neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease are debilitating conditions resulting from a progressive degeneration of nerve cells that is attributed to oxidative stress. Given the role of hydrogen sulphide (H₂S), an endogenously produced signalling molecule involved in regulating of oxidative stress, exogenous administration of H₂S has been proposed as a potential treatment strategy. This research study involved an investigation into the mechanical properties of microneedles loaded AP39 (a H₂S donor), their ability to penetrate skin and effectiveness to deliver AP39 across murine skin. Additionally, the study explored the capability of permeated AP39 to release H₂S and thus quench H₂O₂-induced oxidative stress in neuroblastoma cells, SHSY5Y cells. Methods: Microneedles were prepared using 20% w/v polyvinyl alcohol (PVA) of either 27,000 or 67,000 molecular weights, with or without trehalose 15% w/v. Mechanical and insertion properties of microneedles were determined and optimised formulation applied to murine skin to observe AP39 flux through the skin. Collected media was applied to a microvasculature blood–brain-barrier model to evidence AP39 permeation, following which, permeated AP39 was applied to an oxidative stress scenario in SHSY5Y cells to assess AP39 potential in limiting oxidative stress. Results: Microneedle fracture testing observed the microneedles produced from polyvinyl alcohol 67,000 with trehalose were best able to withstand compression force applied. Microneedles formulated from PVA 67,000 were best able to penetrate the parafilm model. Further, the PVA 67,000 with trehalose microneedle formulation was observed to pierce murine skin and deliver 32.84 ± 2.11% of applied AP39 across the skin over 32 h. AP39 transport across the HUVEC microvasculature model gave an apparent membrane permeability of 18.6 ± 1.4. Finally, AP39 attenuated H₂O₂-induced oxidative stress as well as inflammation in SHSY5Y cells; resulting in reduced neurodegeneration burden. Conclusion: These findings demonstrate that microneedle patches for the transdermal delivery of AP39 may provide a promising clinical approach in the treatment of neurological disorder associated with oxidative stress.