Importantly, in all cases robust growth was observed and cell morphology was normal (representative phase contrast photomicrographs are available in Figure ). It is also noteworthy that in this case we did not observe any significant effect of the photocuring atmosphere, air vs. argon. This indicates that the effect of oxygen inhibition was relatively modest and is consistent with the gel fraction results which were similar for both photocuring atmospheres. From an application standpoint, this is particularly important, because in situ photocuring is much easier to perform under room air, rather than specialized inert gas atmosphere. Overall, these results are similar to those in our previous work with homometallic Bi and Zn catalyzed macromonomers and in contrast to the cytotoxic response observed for organotin catalyst . Interestingly, this is despite significantly lower gel fraction for the materials tested here, which suggests that indeed toxicity of residual catalyst is likely the main driving factor of cytotoxic response, rather than residual macromonomers/oligomers.