Photodegradable polyacetal-based cross-linkers and polymer hydrogels
Photodegradable polymers constitute an emerging class of materials that finds numerous applications in biotechnology, biomedicine, and nanoscience . Photodegradable polymers in the form of hydrogels are of particular interest, because of their excellent adaptation in cell cultures allowing also the spatiotemporal control of their gelation behavior by an external stimulus such as light irradiation.
In this work, we have synthesized photodegradable cross-linkers based on a photodegradable acetal oligomer decorated with acrylate terminal groups. The photodegradable acrylate terminated oligomers were synthesized via a two-step process. In the first step, 1,4benzene dimethanol was reacted with an excess of cyclohexanol divinyl ether in mildly acidic conditions to obtain a photo-cleavable acetal oligomer with vinyl ether terminal groups. For the second step, hydroxyethyl acrylate was added in the reaction to convert the vinyl ether terminal groups of the oligomer into acrylate functionalities. The progress of the reaction was monitored by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy.
The synthesis of the gel was achieved using radical polymerization. Poly (ethylene glycol) methyl ether methacrylate was reacted with the crosslinker under nitrogen at 70oC with Azobisisobutyronitrile as initiator. The gel purified, and the swelling degree was calculated in both water and THF. To demonstrate the degradation and the release of substances, first, malachite green dye was encapsulated in the gel. Then, after the irradiation of the gel, the release of the dye in a solution was measured by UV/Vis spectroscopy.