Amylopectin-Sodium Palmitate Complexes as Sustainable Nanohydrogels with Tunable Size and Fractal Dimensions

Starch-based nanohydrogels with polyelectrolyte characteristics may find unique applications. Herein, the branch chains of amylopectin (AP) were elongated to different extents by amylosucrase, followed by complexation with sodium palmitate (SP) to produce nanohydrogels. Modified AP (mAP) with a longer chain length displayed a better ability to complex with SP, and the mixtures exhibited nanosized particles with an average diameter ranging from 153.5 to 1049.8 nm. The gel strength of bulk nanohydrogels was dependent on the chain length of mAP and SP content, and their fractal dimension was between 1.82 and 2.45. The crystalline structure of native AP was altered from A- to B-type after chain elongation and, subsequently, to B + V-type after complexing with SP. Diffraction peaks of the complexes at 2θ of 7.5°, 12.9°, and 19.8° implied that the AP side chains formed left-handed single helices and the hydrophobic SP was entrapped in the helix cavity.