Dual-modified starch nanospheres encapsulated with curcumin by self-assembly: Structure, physicochemical properties and anti-inflammatory activity

Pullulanase debranching and subsequent hydroxypropylation were applied to prepare a series of dual-modified starches (Hydroxypropylated debranched starch, HPDS) with different degrees of hydroxypropyl substitution. Their structural and physicochemical properties varied with the degree of hydroxypropyl substitution, and all HPDS exhibited the ability to self-assemble into well-shaped nanospheres (100-150 nm, PDI < 0.2). These HPDS nanospheres were attempted to encapsulate curcumin with the aim of improving the bioavailability, solubility and stability of curcumin. Their structural characteristics, thermal stability, iodine staining, morphology, safety, encapsulation efficiency, in vitro gastrointestinal release behavior, and anti-inflammatory activity were evaluated. The results showed that curcumin could be effectively encapsulated into the HPDS nanospheres, and the encapsulation efficiency, water solubility and physical stability were positively correlated with the degree of hydroxypropyl substitution. After encapsulation, the water solubility and physical stability of curcumin could be increased up to 226-fold and 6-fold, respectively. The HPDS nanospheres also exhibited good safety (including hemolysis and cytotoxicity) and sustainable release of curcumin. Evaluation of anti-inflammatory activity showed that the activity of curcumin-encapsulated HPDS was enhanced by 170% compared to unencapsulated curcumin. These suggest that HPDS nanospheres encapsulation may be a more suitable option for the development of functional foods containing bioactive compounds.