Stiffer hydrogels, formed via higher peptide concentrations, required a shorter gelation period i.e., 2 wt% (20 mg mL -1 ) of P2 took only a few seconds for gelation, compared to 1 h for 0.3 wt% (3 mg mL -1 ) (Fig. ). The gels formed in MilliQ are transparent; however, when the concentration of metal exceeds 3 equiv. of the peptide, precipitation occurs. The gels formed in PBS are opaque. At peptide concentrations which are sufficiently high for hydrogel formation, the resulting hydrogels containing Zn(II) are stiffer than those without. The mechanical properties of the Zn-containing hydrogels differ when they are in buffer versus in Milli-Q water. The difference in their behavior was quantified and further assessed via oscillatory rheology (section 3.3).