Self-Healing, Self-Assembled β‑Sheet Peptide–Poly(γ-glutamic acid) Hybrid Hydrogels

Self-assembled biomaterials are an important class of materials that can be injected and formed <i>in situ</i>. However, they often are not able to meet the mechanical properties necessary for many biological applications, losing mechanical properties at low strains. We synthesized hybrid hydrogels consisting of a poly­(γ-glutamic acid) polymer network physically cross-linked via grafted self-assembling β-sheet peptides to provide non-covalent cross-linking through β-sheet assembly, reinforced with a polymer backbone to improve strain stability. By altering the β-sheet peptide graft density and concentration, we can tailor the mechanical properties of the hydrogels over an order of magnitude range of 10–200 kPa, which is in the region of many soft tissues. Also, due to the ability of the non-covalent β-sheet cross-links to reassemble, the hydrogels can self-heal after being strained to failure, in most cases recovering all of their original storage moduli. Using a combination of spectroscopic techniques, we were able to probe the secondary structure of the materials and verify the presence of β-sheets within the hybrid hydrogels. Since the polymer backbone requires less than a 15% functionalization of its repeating units with β-sheet peptides to form a hydrogel, it can easily be modified further to incorporate specific biological epitopes. This self-healing polymer−β-sheet peptide hybrid hydrogel with tailorable mechanical properties is a promising platform for future tissue-engineering scaffolds and biomedical applications

Single-Step Homogeneous Immunoassays Utilizing Epitope-Tagged Gold Nanoparticles: On the Mechanism, Feasibility, and Limitations

A single-step gold nanoparticle (AuNP)-based immunoassay is demonstrated in which the nanoparticle surface is tagged with short viral peptide epitopes. Antiviral antibodies with monoclonal specificity trigger nanoparticle aggregation yielding a colorimetric response that enables detection of antibodies in the low-nanomolar range within a few minutes. <i>In silico</i> insights into the interactions at the epitope–gold interface demonstrate that the conformational landscape exhibited by the epitopes is strongly influenced by the amino acid sequence and location of particular residues within the peptides. The conformation, orientation, and linker chemistry of the peptides affect the immune complex formation in nonintuitive ways that are, nevertheless, explained by a unique sterically kinetically driven aggregation mechanism. The rapid and specific performance of the AuNP immunoassay may have generic potential in point of care diagnostics and other laboratory routines