During the month of September, we showed some applications involving photostimulation of hydrogels. The use of light to induce reactions in materials is closer to our daily life than we think. A popular one is in the treatment of dental cavities or reparative procedures in which dentists apply a strong light to finalize the curing of resins. Some types of paintings and protective coatings also require ultraviolet (UV) light to increase the adhesion and gain efficiency in the process. Even in beauty salons, lamp nail lights can be applied to cure some types of nail polishes making them more resistant.
In the biomedical research context, biomaterials based on water and specially natural components (hydrogels) have been investigated with great success for improving or developing novel treatments in healthcare. Since the major constituent of hydrogels is water, their processability can be challenging and their final sturdiness delicate to control. In this light, natural components found in animal tissues and organs such as collagen, gelatin, hyaluronic acid and dextran have been extracted and chemically modified to be able to react under light exposure. In addition to this chemical modification where methacrylate or acrylate groups are added into the polymer chain, a photoinitiator is also needed to generate free radicals and start the reactions. These induced reactions make a liquid solution turn into a solid gel (gelation process).
The use of light for inducing these reactions allows the researcher to have a better control over the processability and the final viscoelastic properties of the hydrogel. In the biomedical context, the first relates to our ability to handle liquid-to-solid phase transitions (in vivo injection, 3D bioprinting, 3D cell culture, etc.). The second relates to the need of controlling the viscoelastic properties of the hydrogel that needs to match the mechanical behavior of the intended implantation site.