Development of lysozyme loaded microneedles for dermal applications

Microneedles are being widely explored for dermal delivery of macromolecules. They have the capability and the potential for entrapping enzymes such as lysozyme within a polymeric matrix that do not alter the protein integrity, enable a bolus or a sustained release. In this study, polymeric microneedles have been used to entrap lysozyme (14 kDa) using biodegradable and dissolving polymers such as Polyvinylpyrrolidone (PVP), Hyaluronic acid (HA), and Poly lactic co glycolic acid (PLGA). Microneedles were fabricated using mold casting technique. The structural strength was determined using texture analyzer where PLGA microneedles (16.56 ± 0.23 g) required a significantly higher puncture force as compared to PVP and HA microneedles (12.10 ± 0.04 g and 11.40 ± 0.32 g respectively). The release profile showed an instantaneous release in the case of PVP and HA with almost 50% of the drug released within the first 20 min in both cases and remaining drug was released within the next 2 h whereas Lysozyme entrapped in PLGA showed a release of 29.53 ± 0.78% of lysozyme 72 h. Lysozyme entrapped in microneedles was characterized using circular dichroism and SDS-page analysis for structural stability post microneedle fabrication. The stability studies were performed on these polymeric microneedles for understanding its delivery potential of bio-active lysozyme. At the end of 90 days lysozyme concentration entrapped was 90.35 ± 0.06% 93.76 ± 0.34% 91.74 ± 0.37% for PVP, HA and PLGA respectively. The protein integrity remained intact for three months (α + β) sheets remained intact in the three different polymeric microneedles. The enzyme assay showed that the enzyme entrapped inside microneedles is biologically active and could be used to lyse bacterial infections for dermal applications. However, a detailed analysis of protein formulations would be useful for extending microneedles applications in wounds, skin infections.