Preparation, characterization and in vitro release study of gallic acid loaded silica nanoparticles for controlled release.

Gallic acid (GA) is an interesting pharmaceutical component of plants. However, the short lifetime and the autoxidation of GA in aqueous solution significantly reduces its bioavailability and the residence time in the body system. In this study, GA was chemically bound to silica nanoparticles to control the release of GA based on the hydrolysis of the chemical bonds, and a silica nanoparticle drug delivery system was established. Gallic acid loaded silica nanoparticles (GA-SiO2) were synthesized by a modified Stober method. The Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis proved that GA did conjugate to silica nanoparticles. The particle size of the GA-SiO2 nanoparticles observed by Scanning Electron Microscope (SEM) was about 30 nm and the drug loading efficiency determined by Thermo Gravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) was 89.39%. The in vitro release study demonstrated that GA could be gradually released from the GA-SiO2. In addition, the antioxidant capability increased continuously during the immersion time, so the GA could serve as an excellent antioxidant to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals in a long release period. Therefore, this study provided a novel drug delivery system for GA with controlled release capability and prolonged antioxidant activity.