Photosensitive hydrogels

For example, stereolithography can be used. It is a liquid-based technique that utilizes LBL curing of a photosensitive hydrogel precursor solution by means of a laser. Alternatively, nozzle-based systems are applied. They process the material chemically as it passes through the nozzle (ink-jet printing, 3D printing cf. Section 3.10). Cells and biomolecules can be simultaneously printed with the scaffold material [79]. 

Photosensitive Hydrogels, Table 1 Examples of pho-tochromic molecules and photochromic processes... 

Encapsulating drugs in hydrogel nanoparticles 2-nm-diameter polyacrylamide nanoparticles lacking charge on then-surfaces, which prevents blood proteins from sticking to their surfaces For delivery of photosensitizer meta-tetra(hydroxyphenyl) chlorin for head and neck cancer 26... 

After the cross-linking process is started, it cannot be cancelled or stopped it is controlled only by the initial process conditions. Photopolymerization is the conversion of a liquid polymer solution to gel under the action of photosensitizing additives and light [10] and is the most ideal method for synthesis of cross-linked hydrogels intended for use in medical practice since it allows for the reaction to be carried out with almost 100% efficiency. 

Ruan et al. (2003) presented a mass-changing pH-responsive HG that increased sensitivity by increasing the fraction of the AA in the poly(acrylic acid-co-isooctyl acrylate) copolymer. Maruyama et al. (2008) described a hydrogel film made of UV photosensitive resin. Tlie output is a change in color of the HGs that is one of the most easily recognizable changes for humans to detect (Deligkaris et al., 2010). 

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