Recently, there has been a wave of reports on the fabrication of peptide-based underwater adhesives with the aim of understanding the adhesion mechanism of marine sessile organisms or creating new biomaterials beyond nature. However, the poor shear adhesion performance of the current peptide adhesives has largely hindered their applications. Herein, we proposed to sequentially perform the interfacial adhesion and bulk cohesion of peptide-based underwater adhesives using two redox-complementary peptide/polyoxometalate (POM) coacervates. The oxidative coacervates were prepared by mixing oxidative H5PMo10V2O40 and cationic peptides in an aqueous solution. The reductive coacervates consisted of K5BW12O40 and cysteine-containing reductive peptides. Each of the individual coacervate has well-defined spreading capacity to achieve fast interfacial attachment and adhesion, but their cohesion is poor. However, after mixing the two redox-complementary coacervates at the target surface, effective adhesion and spontaneous curing were observed. We identified that the spontaneous curing resulted from the H5PMo10V2O40-regulated oxidization of cysteine-containing peptides. The formed intermolecular disulfide bonds improved the cross-linking density of the dual-peptide/POM coacervates, giving rise to the enhanced bulk cohesion and mechanical strength. More importantly, the resultant adhesives showcased excellent bioactivity to selectively suppress the growth of Gram-positive bacteria due to the presence of the polyoxometalates. This work raises further potential in the creation of biomimetic adhesives through the orchestrating of covalent and noncovalent interactions in a sequential fashion.

Self-assembly has been identified as an innovative strategy for improving the antimicrobial efficacy and bioavailability of short peptides. However, the detailed molecular information of short peptides linking to the self-assembly structures and antimicrobial activity remains to be more clearly understood. This work reported that the constitutional isomeric sequences of cationic peptides showed a significant impact on their antimicrobial activity. We investigated the self-assembly structures of two constitutional isomeric peptides Ac-RFSFSFR-NH2 and Ac-SFRFRFS-NH2, which contained the same serine, alkaline, and phenylalanine residues but in a different order. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed that the constitutional isomers self-assembled into different morphologies in an aqueous solution. The sequence with alkaline residues located at both termini of the peptide favored the formation of β-sheet conformation and nanofibers, while irregular nanospheres were observed when positioning the alkaline residues at the center of the isomeric peptide. The ζ-potential measurements showed that the Ac-RFSFSFR-NH2 nanofibers had a net potential of +17.4 mV, whereas the apparent potential of Ac-SFRFRFS-NH2 nanospheres dropped steeply to +1.0 mV. These differences of the constitutional isomeric peptides were directly reflected in their antimicrobial activities. In comparison with the peptide Ac-SFRFRFS-NH2, the constitutional isomer Ac-RFSFSFR-NH2 exhibited much higher antimicrobial efficacy against Gram-positive Staphylococcus aureus and Bacillus subtilis and Gram-negative Escherichia coli and Pseudomonas aeruginosa. Moreover, several pairs of constitutional isomeric peptides with a similar sequence layout yielded the same outcome. These collective results not only highlight the importance of the isomeric sequence on the antimicrobial efficacy of short peptides but also increase further potential in optimizing the design of self-assembled nano-antimicrobial peptides (AMPs).

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The fusion of protein science and peptide science opens up new frontiers in creating innovative biomaterials. Herein, a new kind of adhesive soft materials based on a natural occurring plant protein and short peptides via a simple co‐assembly route are explored. The hydrophobic zein is supercharged by sodium dodecyl sulfate to form a stable protein colloid, which is intended to interact with charge‐complementary short peptides via multivalent ionic and hydrogen bonds, forming adhesive materials at macroscopic level. The adhesion performance of the resulting soft materials can be fine‐manipulated by customizing the peptide sequences. The adhesive materials can resist over 78 cmH2O of bursting pressure, which is high enough to meet the sealing requirements of dural defect. Dural sealing and repairing capability of the protein‐peptide biomaterials are further identified in rat and rabbit models. In vitro and in vivo assays demonstrate that the protein‐peptide adhesive shows excellent anti‐swelling property, low cell cytotoxicity, hemocompatibility, and inflammation response. In particular, the protein‐peptide supramolecular biomaterials can in vivo dissociate and degrade within two weeks, which can well match with the time‐window of the dural repairing. This work underscores the versatility and availability of the supramolecular toolbox in the easy‐to‐implement fabrication of protein‐peptide biomaterials.

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