Separable nanocomposite hydrogel microneedles for intradermal and sustained delivery of antigens to enhance adaptive immune responses.

Vaccines play a critical role in combating infectious diseases and cancers, yet improving their efficacy remains challenging. Here, we introduce a separable nanocomposite hydrogel microneedle (NHMN) patch designed for intradermal and sustained delivery of ovalbumin (OVA), a model antigen, to enhance adaptive immune responses. The NHMN patch consists of an array of OVA-loaded microneedles made from photo-cross-linked methacrylated hyaluronic acid and laponite (LAP), supported by a hyaluronic acid backing. The incorporation of LAP not only enhances the mechanical strength of the pure hydrogel microneedles but also significantly prolongs OVA release. Furthermore, in vitro cell experiments demonstrate that NHMNs effectively activate dendritic cells without compromising cell viability. Upon skin penetration, NHMNs detach from the backing as the hyaluronic acid rapidly dissolves upon contact with the skin interstitial fluid, thereby acting as antigen reservoirs to release antigens to abundant skin dendritic cells. NHMNs containing 0.5% w/v LAP achieved a 15-day OVA release in vivo. Immunization studies demonstrate that the intradermal and sustained release of OVA via NHMNs elicited stronger and longer-lasting adaptive immune responses compared to conventional bolus injection. Given its easy to use, painless and minimally invasive features, the NHMN patch shows promise in improving vaccination accessibility and efficacy against a range of diseases. STATEMENT OF SIGNIFICANCE: The study introduces a separable nanocomposite hydrogel microneedle (NHMN) patch. This patch consists of an array of ovalbumin (OVA, a model antigen)-loaded microneedles made from photo-cross-linked methacrylated hyaluronic acid and laponite, with a hyaluronic acid backing, designed for intradermal and sustained delivery of antigens. This patch addresses several key challenges in traditional vaccination methods, including poor antigen uptake and presentation, and rapid systematic clearance. The incorporation of laponite enhances mechanical strength of microneedles, promotes dendritic cell activation, and significantly slows down antigen release. NHMN-based vaccination elicits stronger and longer-lasting adaptive immune responses compared to conventional bolus injection. This NHMN patch holds great potential for improving the efficacy, accessibility, and patient comfort of vaccinations against a range of diseases.