Preparation, characterization and evaluation of tea polyphenol–Zn complex loaded β-chitosan nanoparticles

•Method of preparing chitosan (CS) nanoparticles (NPs) was modified to obtain small particle size.•Tea polyphenol-Zn (TP-Zn) complex loaded α- and β-chitosan NPs were created with size <100 nm.•TP–Zn complex loaded CS NPs showed good thermal stability.•Antioxidant activity of TP–Zn complex loaded CS NPs was significantly improved.•TP-Zn loaded CS NPs have hardly any cytotoxicity.

This study investigated the preparation of β-chitosan (CS) nanoparticles (NPs) based on the principle of ionic gelation between CS and sodium tripolyphosphate (TPP). The β-CS was depolymerized to molecular mass (MM) < 40 kDa for obtaining β-CS NPs at < 50 nm. Tea polyphenol (TP)-Zn complex loaded β-CS NPs were further prepared with a TP–Zn complex encapsulation efficacy of 97.33%, average particle size of 84.55 nm, and Zeta-potential of 29.23 mV. TP–Zn complex loaded β-CS NPs exhibited higher antioxidant activity than that of TP loaded β-CS NPs based on reducing power, DPPH radical scavenging activity, and oxygen radical absorbance capacity (ORAC) values. The in vitro release study conducted at pH 4.5 and 7.4 showed that the TP–Zn complex loaded β-CS NPs sustained the release of the TP–Zn complex over 5.5 h. Structural analysis using transmission electron microscope (TEM), atomic force microscopy (AFM), Fourier transform infrared spectrometer (FT-IR), and thermogravimetric analysis (TGA)-differential scanning calorimetry (DSC) indicated that TP–Zn complex was well incorporated into CS NPs. Fluorescein-5-isothiocyanate (FITC)-TP-Zn complex loaded β-CS NPs maintained the morphological characteristics of living cells and were well attached to the inside of EBM-2 endothelial cells, corroborating the result of the cytotoxicity test that NPs have hardly any cytotoxicity. This study suggested that TP–Zn complex loaded β-CS NPs can be used as an antioxidants delivery system for food and other applicants.

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