In this work, a natural polysaccharide gellan gum (GG) has been modified with methacrylic groups (GG-MA) and combined with polyethylene glycol dimethacrylate (PEG-DMA) in order to create novel injectable hydrogels that can be easily delivered through a needle and photocross-linked in the injection site. A novel synthetic procedure for methacrylation of GG has been proposed to better control its derivatization. Different degrees of functionalization have been achieved and their effects on the solubility and mechanical properties of GG-MA were investigated. A good balance in terms of hydrophilicity and elasticity of the corresponding hydrogels was identified, although not suitable enough as injectable material for the treatment of damaged soft tissues. For this reason, several concentrations and different molecular weights of PEG-DMA were investigated to modulate the composition of GG-MA hydrogels and overcome their extreme fragility. Swelling abilities of the hydrogels in different media were studied as a key parameter able to affect the release profile of loaded therapeutic agents. Model molecules having different spherical hindrance (sulindac and vitamin B12) were then chosen to study how the hydrogels were able to modulate their diffusion profiles over time. Finally, the hydrogel's safety was evaluated trough an MTT cytotoxicity test on human fibroblasts.