Self-Applicable Thermostable Heterogeneous Microneedle Patch for Recombinant Protein Vaccination against Botulinum Neurotoxin Serotype A

Botulinum neurotoxin serotype A (BoNT/A), a Class A bioterrorism agent, poses significant poisoning risks, with diagnosis challenges and no specific antidotes, making vaccination the most effective prevention. However, traditional needle-based vaccines are painful, thermally unstable, require trained professionals for administration, and carry infection risks, leading to low patient compliance. To overcome these limitations, we introduce a self-applicable, thermostable, heterogeneous microneedle (MN) patch for delivering a recombinant protein vaccine based on the C-terminal heavy chain of BoNT/A to prevent botulism. By incorporating materials with varying hydrophilicity, the MN patch enhances drug-layer contact with skin, improving vaccine delivery efficiency. Fabricated via heat- and pressure-assisted micromolding, the polycaprolactone MNs demonstrate sufficient mechanical strength for effective skin penetration. In vivo studies in a mouse model show that MN patches loaded with the recombinant C-terminal heavy chain of BoNT/A elicit strong IgG antibody responses and provide protective efficacy comparable to those of intramuscular injections, with all immunized mice surviving lethal BoNT/A challenges. The IgG responses of MN patches did not decrease after storage for 6 mol (25 °C, 60% relative humidity), indicating good stability. These findings suggest that thermostable MN patches offer a noninvasive, effective, patient-friendly alternative to traditional vaccines, with potential applications in bioterrorism prevention.