Surface modification of silica nanoparticles by chitosan for stabilization of water-in-oil Pickering emulsions

Water-in-oil (W/O) Pickering emulsions (PEs) as delivery systems have recently attracted important research efforts. The lack of food-grade hydrophobic particulate as emulsion stabilizers is the most important challenge in this field. This study investigates the surface modification of silica (SiO2) nanoparticles (SNPs) by chitosan and their role in formulation and stabilization of PEs; namely, the adsorption of chitosan on the surface of SNPs through electrostatic attraction with different chitosan/SiO2 ratio and pH values. The ability of SNPs to stabilize water in oil PEs regarding this modification was then investigated. The interaction between SNPs and chitosan was characterized by zeta potential, wettability, FTIR, Energy dispersive X-ray mapping analysis (EDX- MAP) and nitrogen absorption/desorption isotherm. The results confirmed that the surface modification of SNPs by chitosan had a significant impact on zeta potential and on the wettability of SNPs. Finally, modified SNPs were applied to the formulation of PEs; we identified the optimized conditions that increase the emulsion formulation process and stability. Therefore, modified SNPs by chitosan in this study could act as food-grade W/O Pickering stabilizers to fabricate environmental-friendly emulsion products.