2.4. Nanoparticle characterization

The average particle size, polydispersity index, and zeta potential of freshly prepared nanoparticles solution(pH = 5.0) were measured at 25°C using DLS (Brookhaven 90 Plus).

Used X‐ray CCD single crystal diffractometer to measure RES‐ZEIN‐SHA NPs, proportional physical mixture and X‐ray diffraction (XRD) patterns of three components. The XRD patterns were recorded at a scanning range of 10°–40° (2θ) and a scanning rate of 5°/min.

A certain concentration of nanoparticles solution was dropped on a carbon‐coated copper mesh, dried by natural air, and the morphology of the nanoparticles was observed and analyzed by Transmission electron microscope (JEM‐1011, JEOL).

An ultraviolet spectrophotometer was used to determine the content of resveratrol in the nanoparticles. An aliquot of freeze‐dried nanoparticles (20 mg) was dissolved in 10 ml DMSO, and stirred for 2 hr in the dark. Then the solution was centrifuged at 13,700 g for 30 min. The supernatant was diluted with DMSO and analyzed by UV‐visible spectroscopy at 327 nm, and the content of resveratrol was calculated by the standard curve, which was established using a standard solution in the range of 0–10 μg/ml (R ² = .9977).

The freshly prepared colloidal dispersion was dialyzed to remove free resveratrol and organic reagents, and then centrifuged at 1,200 g for 5 min to remove large particles, and then freeze‐dried. Particle yield and resveratrol loading use formula to determine efficiency were determined using equations (Equation 1) and (Equation 2):

Measured the release of resveratrol in vitro using the previously reported dialysis method. (Wang et al., ²⁰¹⁸). Put 2 ml of RES loaded zein‐SHA NPs with a certain concentration into the dialysis bag. The dialysis bag was completely immersed in the dialysate (PBS solution, pH = 5.0, pH = 7.4), and the measurement was carried out at 37°C and 100 rpm. 1 ml of dialysate was taken out at certain intervals, and 1 ml of corresponding fresh buffer was added, and the content of resveratrol was measured by UV. The sampling points were 1, 2, 4, 6, 10, 12, 24 hr.

In order to determine the storage stability of the nanoparticles, the nanoparticles were stored in the dark at 25°C for 14 days, and the stability was evaluated by measuring the average size, PDI and potential of the nanoparticles. Stability experiment repeated three times.