WPI hydrogels as a potential substrate for tissue scaffolds: mechanical properties

Whey protein isolate (WPI) sol–gel is proposed for use as a bone tissue regeneration scaffold based on its biocompatibility and potentially suitable mechanical properties. The gel surface successfully supports the attachment and proliferation of healthy, motile MC3T3-E1 preosteoblast cells, as confirmed by scanning electron microscopy. Material stiffness and ultimate compressive and tensile properties of high-protein concentration, heat-induced gels from WPI were characterized, and trends were established based on the protein and CaCl2 concentrations of the gel. The elastic modulus and ultimate material strength were determined to be functions of both varying concentrations. Scanning electron micrographs of gel cross-sections confirmed the network hypothesized based on the macroscopic mechanical testing. One finding challenges the linear nature of concentration dependence reported for similar, low-concentration whey protein gels. A maximum gel strength and subsequent decrease were found at 35% w/v WPI due to local charge screening. The strongest of the gels constructed failed at 2.37 ± 0.09 MPa and had an elastic modulus of 1.65 ± 0.02 MPa, or within one order of magnitude of values considered acceptable for a bone-regeneration scaffold.