Characterization and Drug Delivery Properties of OSA Starch-Based Nanoparticles Prepared in [C3OHmim]Ac-in-Oil Microemulsions System

In this work, an enhanced starch-dissolving room-temperature ionic liquid 1-hydroxypropyl-3-methylimidazolium acetate ([C3OHmim]Ac) was tailor-made to serve as the polar phase in the formation of [C3OHmim]Ac/TX-100 + 1-butanol/cyclohexane (IL/O) microemulsion. Its superior solubility to starch was verified by the polarized-light microscope and turbidity test. Furthermore, a pseudoternary phase diagram, conductivity measurement, and dynamic light scattering (DLS) were used to analyze the phase behavior and microregion of IL/O microemulsion. On this basis starch nanoparticles with a mean diameter of 86.69 nm were successfully prepared in this novel IL/O microemulsion with octenyl succinic anhydride (OSA) maize starch as the raw material and epichlorohydrin as a cross-linker through microemulsion cross-linking reaction. For starch nanoparticles, Fourier transform infrared spectroscopy (FTIR) data demonstrated the formation of ester bonds, and cross-linking reaction in starch molecules and X-ray diffraction (XRD) disclosed the destruction of the crystal structure. In addition, scanning electron microscopy (SEM) intuitively revealed that OSA-modified starch nanoparticles possessed good dispersibility, nanoscaled size, and a relatively concentrated size distribution. Finally, drug loading and releasing properties of starch nanoparticles were investigated with indomethacin as a drug model.