Inducing Microscale Structural Order in Phage Nanofilament Hydrogels with Globular Proteins

Abstract

Biological hydrogels play important physiological roles in the body. These hydrogels often contain ordered subdomains that provide mechanical toughness and other tissuespecific 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 applications 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 selfassembly 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 microstructure. Hybrid hydrogels of M13 phage and bovine serum albumin (0.25 w/v%) were formed and shown to adsorb up to 16× their weight in water. Neither component gelled on its own at the low concentrations used, suggesting synergistic action between the two components in the formation of the hydrogel. The hybrid hydrogels exhibited repetitive self-healing under physiological conditions and at room temperature, autofluorescence in three channels, and antibacterial activity toward Escherichia coli host cells. Furthermore, the hybrid hydrogels exhibited a more than 2× higher ability to pack water compared to BSA-only hydrogels and 2× lower compression modulus compared to tightly packed M13-only hydrogels, suggesting that our method could be used to create hydrogels with tunable mechanical properties and pore structure through the addition of globular proteins, while maintaining bioactivity and microscale structural order.

Bacteriophage‐built gels as platforms for biomedical applications

“…Furthermore, it was found that the addition of globular proteins can influence M13 phages to self‐assemble into ordered nanostructures at concentrations 50 000‐fold lower than they otherwise would naturally. [ 47 ]…”

“…Hydrogels developed using both M13 phage and BSA, or hybrid M13‐BSA hydrogels, exhibited a significantly larger swelling ratio (~14 times their dry weight) when compared to BSA hydrogels (~4 times their dry weight). [ 47 ] Further decreasing the BSA concentration of these hydrogels from 3% to 1% resulted in an even higher swelling ratio of ~15 times their dry weight. These results suggest a possible change in the pore structure of the hydrogels in the presence of BSA.…”

“…[ 46 ] Our lab also observed a decrease in the swelling ratio (from 13 times to 10 times) at temperatures other than room temperature (~25°C). [ 47 ]…”

“…[ 41–45 ] In fact, the modification of phages significantly expands the functions of phage materials, which will be illustrated later. Self‐organization: Filamentous phages are rod‐shaped viruses that have the capacity to self‐assemble at high concentrations, creating hierarchical macro‐structures. [ 46–48 ] These macro‐structures are based on the formation of liquid crystalline formations that display unique optical properties that expand the functionality of these bioactive materials. Excellent biocompatibility: Phages and phage‐composed materials were found to have great biocompatibility. [ 49–51 ] Therefore, phages can be regarded as powerful building blocks with unique properties for material synthesis.…”

“…[ 68–71 ] Since 2019, our team at McMaster University has fabricated pure phage hydrogels and microgels for antimicrobial applications. [ 46–48 ] The details of these works will be discussed in the following sections.…”