Preparation and characterization of starch nanoparticles: Effects of various natural deep eutectic solvents

Self-assembly is an effective strategy for synthesizing starch nanoparticles (SNPs); however, conventional approaches have been limited by low yields and restricted morphological diversity. This study introduces an environmentally friendly, highly efficient strategy for regulating SNP morphology, achieving diverse particle structures through the controlled use of various natural deep eutectic solvents (NADES). Scanning electron microscopy revealed that SNPs prepared using water as the solvent exhibited an irregular morphology. By contrast, all NADES induced the formation of smaller, more regular SNPs. Those prepared using betaine and xylitol were regular spheres, and those using choline chloride and malic acid (CMDES) exhibited regular spindle shapes. Turbidity analysis indicated that NADES self-assembly systems containing organic acids all exhibited a lag phase, delaying the nucleation process. Concurrently, the crystallinity of SNPs self-assembled with NADES was higher than that obtained in aqueous solutions. CMDES-prepared SNPs exhibited a maximum layer thickness of 13.80 nm. By contrast, betaine-based NADES-controlled SNPs displayed smaller layer thicknesses but higher fractal dimensions. This study deepens our understanding of NADES-regulated SNP self-assembly and demonstrates the feasibility of NADES for synthesizing diverse SNPs, which are promising for applications in bioactive delivery, biodegradable packaging, or functional foods.