Shape and size-controlled starch nanoparticles prepared by self-assembly in natural deep eutectic solvents: Effect and mechanism

Regulating particle size and shape of starch nanoparticles (SNPs) is imperative to producing natural nanomaterials with controllable physicochemical properties enabling novel applications. In this study, natural deep eutectic solvents (NADES) based on lactic acid and glucose were obtained and used for the self-assembly of SNPs with different shapes and sizes. The size of fabricated SNPs ranged from 406.7 to 104.6 nm, and the shape of SNPs changed from spherical to rice-like with increasing proportion of NADES. X-ray diffraction was shown that SNPs were in B + V crystalline structure, and the relative crystallinity was decreased with the increase of NADES content, indicating that the NADES disrupted the recrystallization of starch molecules. DSC and TGA analysis demonstrated that the longer starch chains self-assembled in NADES system to form SNPs with less ordered crystallization structure. Fourier transform infrared spectra exhibited a shift of O–H stretching band at 3500-3300 cm−1 towards higher wavenumber values due to the weakened hydrogen bond strength of SNPs. In addition, turbidity analysis indicated that the formation of rice-like and smaller size SNPs was related to the inhibition of nucleation and growth of starch by NADES, which was confirmed with the results of yield results. This study has significant implications for the preparation of SNPs with various size and shape in a completely new and highly effective approaches.