Enhancement in site-specific delivery of carvacrol for potential treatment of infected wounds using infection responsive nanoparticles loaded into dissolving microneedles: A proof of concept study

Chronic wound infections have become a challenging problem due to escalating antibiotic resistance and lack of viable delivery approaches. Carvacrol (CAR) has been reported to be effective against multidrug resistant pathogens. In this study, CAR was formulated into a site-specific nanoparticle (NP) delivery system using poly (caprolactone) (PCL) to achieve a sustained antimicrobial effect at infection sites. These NPs were further incorporated into dissolving microneedles (MNs) to facilitate painless application and overcome the necrotic tissue barrier which hinders drug penetration into wound bed. The release study exhibited significantly higher release of CAR from PCL NPs in the presence of bacteria, highlighting its potential for on-demand delivery. Moreover, encapsulation of CAR in PCL NPs resulted in 2-4 fold increase in its antimicrobial activity. Dermatokinetic studies revealed that CAR-PCL NPs-MNs were able to enhance skin retention of CAR after 24 h (83.8 +/- 5.15%), compared to free CAR-MNs (7.3 +/- 2,04%). Importantly, this novel approach exhibited effective antimicrobial activity in an ex-vivo wound model. Hence, these findings have proven the concept that loading of CAR into this advanced MNs platform can lead to sustained antimicrobial effect at desired site and may provide a novel effective approach for treatment of infected wounds. However, further studies must be conducted to investigate in-vivo efficacy of the developed system in an appropriate infection model.