Peptide solutions containing water were prepared at a concentration of 10 mg/ml (1%, v/v). The pH was adjusted to 7.4 with KOH and the solutions were incubated at 37°C. Hybrids formed soft and transparent gels, which visually showed no difference from the original RADA16-I hydrogel, despite being 12 to 17 amino acids longer (Fig. ). The viscoelastic properties of the hybrids were evaluated at physiological temperature (37°C) by dynamic rheometry using cone-plate geometry. For all the studied gels the storage modulus (G') was greater than the loss modulus G", and both were relatively independent of the oscillatory frequency applied, indicating a gel's elastic profile (Fig. ). The storage modulus G' reached a value of 550 Pa for the RADA-GHK peptide (Fig. ), almost the same as for the original RADA16-I peptide. The magnitude of G' for the peptides RADA-IM and RADA-KGHK was around one-tenth of these values. (Fig. ). All hybrids showed good shear-thinning properties. Strain sweep curves of hybrids remained constant in the low shear strain region (strain < 10%), however they indicated a rapid decay in G' above 10% strain and, ultimately, behaviour as a liquid (G" > G') as the shear strain percentage value progressed. RADA16-I behaved like a liquid above 40%, RADA-GHK and RADA-IM above 30% and RADA-KGHK above 25% of shear strain (Fig. ). All the hybrids exhibited elasticity at rest and up to 4 Pa; above this value, they behaved like liquids (Fig. ). This property is necessary to keep cells in suspension in the gel. The application of shear stress resulted in a decrease in these properties, presumably due to disruption of the hydrogen bonds between amino acids in the RADA16-I chains.