Tailoring assembly behavior of starches to control insulin release from layer-by-layer assembled colloidal particles.

Self-assembly behavior of charged-starches significantly influenced core-shell structures of layer-by-layer assembled particles. In this study, insulin (IN)-loaded nanoparticles with structured shell features were fabricated to investigate how the interactions of carboxymethyl starch (CMS) with spermine-modified starch (SS) influenced IN release properties of the particles (IN/CMS/SS/CMS) within the gastrointestinal tract (GIT). Results indicated that the assembly action of CMS and SS could be controlled by simply tailoring the ratio of CMS/SS content. An intermediate CMS/SS ratio (1:4) was required to construct nanoparticles with compact shell structure and desirable IN release properties in the colon (74.23%). However, a higher CMS/SS ratio (1:2) yielded particles with loose shell structure and an excessive IN release in the upper GIT (58.89%), and a lower CMS/SS ratio (1:8) rather resulted in particles with higher compactness shell structure along with limited IN release in the colon (29.01%). The interactions between CMS and SS should be the key factor influencing core-shell structures and in turn the IN-release properties of the carrier. The shell structure and release properties of layer-by-layer assembled particles could be tailored by controlling the interactions between starches.