Novel eco-friendly initiation system based on vitamin C for energy efficient synthesis of PMAA hydrogel used for delivery of phenolic compounds

This study reports successful free radical synthesis of pH-sensitive hydrogels based on poly(methacrylic acid) (PMAA) by using new green initiation system based on vitamin C and hydrogen peroxide (VC/H2O2). The application of proposed initiation system provides many advantages, above all cost effective and eco-friendly synthesis which can be carried out under ambient conditions. The obtained PMAA hydrogels are analyzed by various technics: Differential Scanning Calorimetry, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy and by using single compression tests. In line with the intended application, PMAA hydrogels are further investigated in terms of their potential to be used for encapsulation and controlled release of active substances such as antioxidant phenolic compounds. To keep it green, the total phenolic compounds (TPC) were obtained from orange peels waste by applying ultrasonic-assisted extraction and deep eutectic solvent (DES) based on glycerol:urea:water. The TPC were successfully encapsulated into the PMAA hydrogels which were previously estimated to have the optimal mechanical and swelling properties with respect to the final applica-tion. The swelling behavior of the PMAA hydrogels and controlled release of the TPC were tested as a function of the various synthesis parameters in several media with different pH values. It was shown that TPC can be released in control manner in medium which simulates the environment in human intestines, finally resulting in enhanced bioavailability of TPC, reduced side effects and improved therapeutic effects.