Microneedle & film-forming gel transdermal delivery strategy: A novel approach for vaccine delivery.

The COVID-19 pandemic has underscored the significant challenges of vaccine distribution, particularly to low- and middle-income countries. Even when vaccines are made available through purchases or donations, issues such as insufficient trained medical personnel and inadequate infrastructure impede their widespread use. To address these challenges, we propose the Microneedle & Film-Forming Gel Transdermal Delivery Strategy (MFT strategy), which combines the minimally invasive nature of microneedles with the stability of film-forming gels that can be stored at room temperature. This strategy aimed to simplify vaccine production, reduce logistical burdens, and improve the efficiency of transdermal vaccine delivery while generating strong immune responses. In this study, we used ovalbumin as a model antigen and developed microneedles from methacrylic acid-modified hyaluronic acid, polyvinylpyrrolidone, and polyvinyl alcohol, in conjunction with a polyvinyl alcohol-borax (PVA-B) film-forming gel. In vitro experiments demonstrated that the MFT strategy has achieved an efficiency improvement of 202.75 % compared to previously reported strategies. Besides, PVA-B film forming gel displayed strong antimicrobial properties and effectively stabilized proteins over 30 days at 25 °C, preserving the antigenic structure essential for vaccine efficacy. In vivo tests revealed that the MFT strategy induced humoral immune responses comparable to those achieved by intramuscular injection, with histological analysis confirming good skin tolerance and safety. Overall, the MFT strategy represents a promising vaccine delivery method with substantial clinical potential.