Antigen-Antibody Interaction-Based Self-Healing Capability of Hybrid Hydrogels Composed of Genetically Engineered Filamentous Viruses and Gold Nanoparticles

Background: Filamentous M13 phages have recently been utilized as components for developing novel functional soft materials in various fields such as sensor, device, and biomedical applications. Recently, we have developed liquid crystalline hydrogels composed of M13 phages and gold nanoparticles (GNPs) based on specific interactions between the components. Objectives: The main objective of this study was to clarify the self-healing capability of the hydrogels composed of M13 phages and GNPs. Methods: M13 phages displaying tag peptides with a sequence of YPYDVPDYA (HA phages) were genetically constructed through general molecular biology. The mechanical strength of hydrogels composed of the HA phages and anti-HA peptide antibodies-immobilized GNPs (HA-GNPs) was measured by indentation tests. The rupture point of the hydrogels was visually observed. An aliquot of buffer solution was added into the rupture point of the hydrogels after the indentation test. After incubation for 2 days, self-healing of the rupture point was checked visually. The indentation test was also performed after self-healing. To clarify the assembled structures of the components in the hydrogels, transmission electron microscopy (TEM) observation was performed by transferring the hydrogel onto a TEM grid before and after healing. Results: The strength of the original hydrogel (before self-healing) required for rupture was approximately 55 mN. Self-healing of the rupture point was confirmed visually, and the hydrogels behaved as uniform hydrogels again during the vial inversion tests. As a result of the indentation test for the self-healed points of the hydrogels, the rupture force of approximately 45 mN was detected, indicating the self-healing capability of the hydrogels. TEM observation of the before and after self-healing exhibited the regularly assembled structures composed of the HA-GNPs, suggesting that the ruptured networks were recovered into regularly assembled network structures. Importantly, control of the concentration of the HA-GNPs resulted in suppression of decreasing the rupture forces during the repetitive self-healing processes. Conclusion: Our results demonstrated the self-healing capability of structurally regular hybrid hydrogels composed of genetically engineered filamentous viruses displaying antigen peptides and antibody-immobilized GNPs. The results indicated that supramolecular hydrogels containing filamentous viruses would expand the applicability of virus-based soft materials. Keywords: Filamentous virus, bacteriophage, hydrogel, gold nanoparticle, self-healing, antigen-antibody.