Thermal, spectroscopic characterization and evaluation of antibacterial and cytotoxicity properties of quercetin-PEG-silica hybrid materials

This study reports the characterization of two series of organic-inorganic silica-based hybrid materials with 15 and 20 wt% of quercetin (Q), respectively, and 6, 12, 24 and 50 wt% of polyethylene glycol (P) (for each of them). After the sol-gel synthesis they have been characterized using different techniques (Fourier-Transform Infrared and Micro-Raman spectroscopies, Thermogravimetry, Differential Thermal Analysis). Two tests were also carried out to evaluate their biomedical properties to estimate their antibacterial activity and their cytotoxicity. FT-IR measurements revealed the interaction between the components of the hybrid materials, while Micro-Raman spectra confirmed the presence of quercetin in an oxidized form. Simultaneous Thermogravimetry and Differential Thermal Analysis coupled with Mass Spectrometry enabled to investigate the thermal behavior of the hybrids (up to 800 ◦C) and to analyze the gas mixtures evolved upon heating in severe inert argon atmosphere. Antibacterial tests showed that an increase of PEG contents results in a decrease of the bacterial growth. Finally, cytotoxicity assessment highlighted that entrapping quercetin in hybrids at high PEG content leads to the constitution of materials that enjoy PEG biocompatibility, while cytotoxic effects are depleted.