To achieve a cross-linkable SS-hPG, 7% of the hydroxyl groups were converted into acrylate groups by esterification with acryloyl chloride to obtain SS-hPG-Acry. The hydrogel was subsequently formed by mixing the PBS solution of SS-hPG-Acry and 4-arm-PEG-SH with a determined concentration after overnight incubation at room temperature. The hydrogels were prepared at different weight percent concentrations to investigate the effect of gel concentration on the stiffness and mechanical properties of the hydrogels. The hydrogels were prepared by chemical cross-linking of the thiol groups of the 4-arm-PEG-SH and the acrylates of the SS-hPG-Acry via a thiol-Michael addition click reaction (Figure ). After gelation, the 1 H NMR spectrum showed 90% reduction in the peaks associated with the protons of the alkene group of the acrylate in the region between 6.0 and 6.6 ppm (Figure ) after 1 hour. When observing the corresponding FTIR spectra of the compounds, an alkene band appeared after acrylation at 800 cm -1 and disappeared in result of gelation. The thiol stretching absorbance band at 2700 cm -1 disappeared as well in the hydrogel spectra, indicating the thiol-ene click reaction. G´ and G´´of 17.5% hydrogel measured in cycles of 1% and 600% strain. (F) Photos taken at different time points of 17.5% and 8% hydrogel, one half without dye and second half with blue dye, combined together to prove the self-healing properties of the hydrogel.