Impact of Rosemary Essential Oil-Loaded Chitosan Nanoparticles on the Properties of PCL and Sodium Alginate Films

This study reports the formulation and evaluation of separate biodegradable films composed of polycaprolactone (PCL) and sodium alginate (SA), enriched with rosemary essential oil (REO)-loaded chitosan nanoparticles (RChiNPs). Plain chitosan nanoparticles (ChiNPs) and RChiNPs were produced by ionic gelation and characterized by dynamic light scattering (DLS), zeta potential analysis, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Loading with REO increased the mean nanoparticle diameter from 235.7 nm (ChiNPs) to 257.6 nm (RChiNPs), with a statistically significant difference (p < 0.05), and slightly reduced the zeta potential from +42.9 mV to +40.7 mV. RChiNPs were incorporated into PCL and SA films at 0%, 1%, and 2% (w/w of polymer), and the resulting films were evaluated for surface morphology, water contact angle, and water vapor transmission rate (WVTR). SEM showed increased apparent surface roughness after RChiNP incorporation. In PCL films, the water contact angle decreased from 172.1° to 134.4° with 2% RChiNPs (p < 0.0001); in SA films, it decreased from 91.1° to 73.8°, although the reported change between RChiNP loadings was not statistically significant. WVTR increased from approximately 2 to 6 g/m²·h in PCL films and from approximately 200 to 350 g/m²·h in SA films, with p < 0.0001 reported for both significant comparisons. These findings show that RChiNP incorporation modified surface wettability and water-vapor transmission in both matrices.