Chlorogenic acid entrapped in hybrid materials with high PEG content: A strategy to obtain antioxidant functionalized biomaterials?

The formation of pro-oxidant species after implantation of biomaterials could be responsible for the failure of the implant itself, because of oxidative stress-induced damage. In this work, the SiO 2 /polyethylene glycol (PEG)/chlorogenic acid (CGA) hybrids synthesized by the sol-gel method with 50 wt% of the polymer and different amounts of CGA (5, 10, 15 and 20 wt%) were studied. The hybrids soaked in simulated body fluid (SBF) showed the formation of hydroxyapatite layers on their surface, suggesting that the hybrids are bioactive. Their radical scavenging capacity towards DPPH · and ABTS ·+ (2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), evaluated at three different doses (0.5, 1 and 2 mg), showed probe- and dose-dependent behavior. In addition, the antioxidant properties of CGA were not affected by the presence of high amounts of the polymer. The in vitro biocompatibility in three cell lines (NIH 3T3, HaCaT and SH-SY5Y) was assessed by using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Apart from SH-SY5Y, the cell viability-expressed as mitochondrial redox activity percentage of cells directly exposed to powders-and morphology was not affected, suggesting that the hybrids have the ability to interfere and act selectively against tumor cells. The antibacterial properties of the different materials against Escherichia coli and Enterococcus faecalis were affected by different amounts of the natural antioxidant component.