Nisin-loaded chitosan/sodium alginate microspheres enhance the antimicrobial efficacy of nisin against Staphylococcus aureus

Abstract Aims To develop and evaluate nisin-loaded chitosan/sodium alginate (CS/SA) microspheres as an improved antimicrobial delivery system targeting Staphylococcus aureus strains. Methods and Results The microspheres were prepared using a modified water-in-oil emulsion cross-linking method, resulting in spherical particles sized 1–8 µm with a surface charge of -7.92 ± 5.09 mV, confirmed by scanning electron microscopy (SEM) and Zetasizer analysis. Encapsulation efficiency (EE) and loading capacity (LC) of nisin were 87.60 ± 0.43% and 1.99 ± 0.01%, respectively. In vitro release studies over 48 hours indicated a controlled release pattern of nisin, described by the Korsmeyer–Peppas model, with higher release rates at 37°C and alkaline pH. Antimicrobial assays showed an enhanced efficacy of nisin-loaded CS/SA microspheres compared to free nisin, with minimum inhibitory concentration (MIC) values reduced by 50%. Confocal laser scanning microscopy (CLSM), SEM and transmission electron microscopy (TEM) showed significant bacterial membrane damage and cellular disruption induced by the microspheres. Conclusions This study highlights the potential of nisin-loaded CS/SA microspheres as an innovative antimicrobial delivery system with improved stability and antimicrobial efficacy against S. aureus, addressing limitations associated with nisin alone.