Gamma-Irradiated Starch/Chitosan Composite Particles for the Adsorption of Neospora caninum Membrane Proteins as a Potential Vaccine Delivery Platform

Gamma irradiation offers a simple and reagent-free strategy for tailoring the physicochemical properties of starch for the development of functional biomaterials, although its application in protein delivery systems remains largely unexplored. In this study, starch was irradiated at doses between 50 and 500 kGy and combined with chitosan to produce composite particles for the adsorption of Neospora caninum membrane proteins (NcMP), with the aim of developing a potential intranasal vaccine delivery platform. Irradiation induced progressive oxidation and depolymerization of starch, as evidenced by Fourier transform infrared (FTIR) analysis, increased apparent amylose content, reduced molecular weight and hydrodynamic diameter, and shifted the zeta potential to −13.4 mV, leading to the selection of starch irradiated at 300 kGy for particle preparation. The resulting starch–chitosan particles exhibited spherical morphology and, following protein adsorption, formed a protein-associated nanosystem with a hydrodynamic diameter of 105.7 nm and a zeta potential of −18.8 mV. Protein association was confirmed by fluorescence co-localization and an adsorption efficiency of 34%. These findings demonstrate that gamma irradiation is an effective approach for engineering starch-based composite particles with physicochemical characteristics suitable for protein association and intranasal delivery, supporting their potential as a versatile platform for protein subunit vaccine formulations.