Fig. 4. The effect of the configuration of homocysteine-based linkers on hydrogel behavior. (a) Comparison of the photopolymerization of formulations based on 10 wt% 8armPEG20k SH, 0.4 mM LiTPO and linkers with a homocysteine core. When using Nor-d,l-HCys a 20 mol% excess of ene (8arm-d,l-HCys 120) gives a higher storage modulus G′ than in the equimolar case. In contrast, with Nor-l-HCys the equimolar formulation 8arm-l-HCys 100 exhibits the highest G′ of the series, whereas an excess of Nor-l-HCys results in a reduced storage modulus. (b) Swelling behavior of the studied hydrogels in PBS. Nor-l-HCys gives stable hydrogels at equimolar conditions and when an excess of linker is used. In contrast, with Nor-d,l-HCys and excess of ene is required to yield a stable hydrogel. The data is depicted as mean values of at least triplicates and error bars illustrating the standard deviation.