Para-phenylenediamine crosslinked alginate gels and their mechanical properties

Alginate hydrogels are widely applicable in bioengineering and pharmaceutical applications due to their biocompatibility. Conventionally, calcium ions are used to crosslink alginate chains. However, gel modulus decreases in physiological solutions due to ion exchange with the medium, leading to a deterioration of their microstructure. This can be overcome by replacing the crosslinking calcium ions with covalent bonds. Here, we investigate chemically crosslinked alginate hydrogels using para-phenylenediamine (PPD) as a crosslinker. PPD binds the carboxylic groups present in β-D-mannuronic acid and α-L-guluronic acid residues of alginate chains. The gel modulus is tuned by changing polymer and crosslinker concentrations. These gels show higher moduli and are more brittle as compared to ionic alginate gels for the same crosslinker concentration. A comparison of mechanical properties with respect to the ionic alginate gels will be presented.