Precision-controlled synthesis of monodisperse starch nanoparticles: Factors affecting the self-assembly kinetics

Enzymatic modification has emerged as a crucial technique for enhancing the physicochemical attributes of starch. In particular, the short-chain glucans (SCGs) obtained from the debranching of native starch has been utilized to produce functional micro- and nano-structures through their inherent self-assembly property. However, a significant challenge remains in controlling the self-assembly kinetics of SCGs, which often results in undesirable heterogeneous structures. This study explores the factors governing SCG self-assembly and their impact on the formation of monodisperse starch nanoparticles (SNPs). We discovered that incomplete removal of the debranching enzyme during SCG self-assembly leads to particle aggregation, with the degree of aggregation dependent on the concentration of remaining enzyme. Furthermore, the initial SCG concentration significantly influences SNP growth; high concentration results in gel-like structures, while lower concentration produces discrete and spherical nanoparticles. Complete dispersion of growth species, SCGs, before self-assembly through appropriate high-temperature heating was found to be critical for uniform nuclei formation, thereby resulting in the production of well-defined nanoparticles. Systematically manipulating these kinetic factors allowed us to fabricate monodisperse SNPs with an average size of 200 nm. This study advances our understanding of SCG selfassembly kinetics, providing valuable insights for the precision-controlled synthesis of starch-based nanoparticles.