Gellan Gum (GG) hydrogels are attractive biomaterials for regenerative medicine and tissue engineering applications since they can be easily prepared by temperature decrease below critical solution temperature, and by the addition of ions. This has been advantageous for the encapsulation of viable cells within a structure that gellifies at room temperature ^[1]. However, GG hydrogels do not present cell adhesive properties ^[1] and are slowly degraded by hydrolysis. Considering these constrains, GG polymer was chemically functionalized with divinyl sulfone (DVS) groups by a one-step reaction, followed by dialysis and diethyl ether precipitation, obtaining degrees of substitution up to 95%. Divinyl sulfone functionalized gellan gum (GG-DVS) was reacted with different amounts of a thiol crosslinker sensitive to human metalloproteinase 1 (MMP-1), under physiological conditions, obtaining stable GG-DVS hydrogels with tuned mechanical properties and MMP-1 degradation kinetics. Polymer modifications were analyzed by NMR, rheology, sol fraction, swelling and MMP-1-driven degradation. In order to improve endothelial cell adhesion, thiol terminated peptides (e.g., C16 or T1) were reacted with GG-DVS. The T1 peptide exists in the third domain of the pro-angiogenic CCN1 protein and is known to mediate vascular cell adhesion, proliferation and neovascularization ^[2], while C16 is a peptide sequence which exists in laminin, which is known to promote the differentiation of cells into capillary-like structures ^[3]. In vitro studies with GG-VS hydrogels containing different crosslinker concentrations, and with either T1 or C16 at different concentrations, promoted Human Umbilical Vein Endothelial cells (HUVECs) spreading, proliferation and differentiation. Functionalized GG-based hydrogels showed tunable physical properties and degradability, as well as cell-binding properties that improved cell endothelial performance. There are promising novel materials for tissue regeneration purposes, specifically for improved angiogenesis via the direct interaction with endothelial progenitor cells either seeded or derived from the host after implantation.

[1]      J. T. Oliveira, L. Martins, R. Picciochi, P. B. Malafaya, R. A. Sousa, N. M. Neves, J. F. Mano, R. L. Reis, J Biomed Mater Res A 2010, 93, 852.

[2]      K. Grote, G. Salguero, M. Ballmaier, M. Dangers, H. Drexler, B. Schieffer, Blood 2007, 110, 877.

[3]      M. Ponce, M. Nomizu, H. Kleinman, FASEB J. 2001, 1389.