Photoresponsive alginate hydrogels and their derivatization with small molecules

The creation and commercialization of 3D printing in conjunction with the optimization of photolithography techniques have opened new doors to create scaffolds for tissue engineering. The main drawback of most 3D printed scaffold is the cytotoxicity of either the polymers used or the products formed by their degradation. This project aims at answering this by reverse engineering these issues. A biocompatible polymer, alginate, was used with a redox crosslinker to make it photoresponsive. This polysaccharide can form a hydrogel by crosslinking hard metal cations. Using iron(III) as a crosslinker, the gels obtained proved to be responsive to light in the presence of a photoreducing agent. The photo-responsivity of ferric alginate not only allowed for its in-depth patterning and a surface etching but also provided a template for the fabrication of homogeneous alginate hydrogels crosslinked with other hard cations. The patterned gels were also turned non-responsive to their environment by further chemical crosslinking of the polymer with a diamine compound, Cystamine. A new technique was developed to create thin-layer assembly of photodegradable iron(III) alginate layers. This technique is a new step toward the creation of scaffolds suitable for tissue engineering. The presence of carboxylate groups on alginate made possible its derivatization with small molecules such as amino acids, fluorescent dyes and proteins, which could be of use later on for drug delivery systems. The use of iron(III) alginate nanoparticles as 'smart' carriers was investigated, using Forster Resonance Energy Transfer between two fluorescent dyes, coumarin and fluorescein.