Instrumentation: 1 H NMR and 13 C NMR spectra were recorded either on a Bruker AVANCE III 500 (Bruker Corporation), or a Jeol ECP 600 (JEOL GmbH). Chemical shifts are reported in δ (ppm) and referenced to the respective solvent. Deuterated water (D2O) was used for the characterization of the final polymeric products. Infrared spectroscopy measurements of the compounds were conducted using a JASCO FT/IR-6700 FT-IR Spectrometer. For the encapsulation and release experiments, UV/vis measurements were conducted on an Agilent Cary 8454 UV/visible spectrophotometer, using semi-micro reusable cuvettes. The rheological trends of the hydrogels were evaluated by using a Malvern Kinexus rheometer. A plate upper geometry (8 mm diameter) and a cone upper geometry (1:20 mm diameter) were used as test geometries depending on the viscosity of the hydrogels. Time and frequency sweep tests were conducted before the measurements and fixed at 1 Hz and 1% strain. A closed system was used to avoid evaporation of water from the hydrogels during measurements. The surface morphologies of lyophilized hydrogel samples were analyzed using a Scanning Electron groups of the PEG in PBS solution at a pH of 7.4. The general procedure consisted of preparing two solutions of SS-hPG-Acry and 4-arm-PEG-thiol in PBS solution. 100 µL of 4-arm-PEGthiol was first added to a 2-mL Eppendorf cap, followed by 100 µL SS-hPG-Acry solution and mixed with the help of an Eppendorf pipette. The cap was then sealed with the inversed Eppendorf and the hydrogels were left to shake at 100 rpm overnight.