Inducing Microscale Structural Order in Phage Nanofilament Hydrogels via Macromolecular Crowding with Globular Proteins

Biological hydrogels play important physiological roles in the body. These hydrogels often contain ordered subdomains that provide mechanical toughness and other tissue-specific functionality. Filamentous bacteriophages are nanofilaments with a high aspect ratio that can self-assemble into liquid crystalline domains that could be designed to mimic ordered biological hydrogels and can thus find application in biomedical engineering. We have previously reported hydrogels of pure crosslinked liquid crystalline filamentous phage formed at very high concentrations exhibiting a tightly packed microstructure and high stiffness. In this work, we report a method for inducing self-assembly of filamentous phage into liquid crystalline hydrogels at concentrations that are several orders of magnitude below that of lyotropic liquid crystal formation, thus creating structural order, but a less densely packed hydrogel. Hybrid hydrogels of M13 phage and bovine serum albumin (0.25 w/v%) were formed and shown to adsorb up to 16 its weight in water. Neither component gelled on its own at the low concentrations used, suggesting synergistic action between the two components in forming the hydrogel. The hybrid hydrogels exhibited repetitive self-healing under physiological conditions and at room temperature, autofluorescence in three channels, and antibacterial activity towards <i>Escherichia coli</i> host cells. Furthermore, the hybrid hydrogels exhibited more than 2 higher ability to pack water compared to BSA-only hydrogels and 2 higher flexibility (lower compression modulus) compared to tightly packed M13-only hydrogels, suggesting that our method could be used to create hydrogels with tunable mechanical properties through the addition of globular proteins, while maintaining structural order at the microscale.