Synthesis and characterization of retrograded starch nanoparticles through homogenization and miniemulsion cross-linking

• RS3NPs prepared by homogenization with w/o cross-linking technique about 200 nm.
• The optimization of RS3NPs using Box-Behnken experimental design methodology.
• The nanosized character was confirmed by DLS, SEM, XRD, DSC and FTIR observation.
• The physicochemical properties of the RS3NPs have changed.
• RS3NPs exhibited low in vitro starch digestibility rate, high adsorption capacities, and long in vitro release.

A new and convenient route to synthesizing retrograded starch nanoparticles (RS3NPs) through homogenization combined with a water-in-oil miniemulsion cross-linking technique was developed. The RS3NPs were optimized using Box–Behnken experimental design. Homogenization pressure (X1), oil/water ratio (X2), and surfactant (X3) were selected as independent variables, whereas particle size was considered as a dependent variable. Results indicated that homogenization pressure was the main contributing variable for particle size. The optimum values for homogenization pressure, oil/water ratio, and surfactant were 30 MPa, 9.34:1, and 2.54 g, respectively, whereas the particle size was predicted to be 288.2 nm. Morphological, physical, chemical, and functional properties of the RS3NPs were the assessed. Scanning electron microscopy and dynamic light scattering images showed that RS3NP granules were broken down to size of about 222.2 nm. X-ray diffraction results revealed a disruption in crystallinity. The RS3NPs exhibited a slight decrease in To, but Tp and Tc increased and narrowest Tc–To. The solubility and swelling power were also increased. New peaks at 1594.84 and 1403.65 cm−1 were observed in the FTIR graph. However, homogenization minimally influenced the antidigestibility of RS3NPs. The absorption properties improved, and the adsorption kinetic described the contact time on the adsorption of captopril onto RS3NPs. In vitro release experiment indicated that the drug was released as follows: 21% after 2 h in SGF, 42.78% at the end of 8 h (2 h in SGF and 6 h in SIF), and 92.55% after 12 h in SCF. These findings may help better utilize RS3NP in biomedical applications as a drug delivery material.