Sol-Gel Synthesis of Caffeic Acid Entrapped in Silica/Polyethylene Glycol Based Organic-Inorganic Hybrids: Drug Delivery and Biological Properties

The failure of medical devices, such as bones prosthesis, is mainly due to inflammatory and infectious phenomena. Entrapping anti-inflammatory and antimicrobial agents inside the biomaterial matrix could avoid these phenomena. In this context, inorganic/organic silica (S)/polyethylene glycol (P)/caffeic acid (A) hybrid systems were synthesized via the sol-gel method with different weight percentages of P and A. Fourier-transform infrared (FT-IR) revealed that caffeic acid undergoes an oxidizing phenomenon in the sol-gel synthesis condition. Additionally, the formation of a hydroxyapatite layer on hybrid surfaces was demonstrated by employing the Kokubo test and analyzing the samples using scanning electron microscopy, X-ray diffraction, and FT-IR. Moreover, further characterization of the antimicrobial activity of the synthesized biomaterials was carried out using the Kirby–Bauer test. Finally, UV-Vis measurement was useful to evaluate the caffeic acid kinetic release in simulated body fluid (SBF) at 37 °C. The kinetic study disclosed that the hybrid materials without polyethylene glycol had faster release rates than the ones obtained without the organic polymer.