Peptide-based Supramolecular Polymers And Biomimetic Underwater Adhesives

Inspired by natural marine organisms,researchers have developed a large number of dependent on the synthesis of covalent polymers biomimetic underwater adhesives.Although the interface adhesion and bulk cohesion of the covalent polymer adhesives have great advantages compared with other system,the synthetic polymer adhesives have poor biocompatibility and biodegradability,resulting in limitation of its extensive application.Therefore,researchers began to focus on non-covalent systems,which have diverse materials,flexible design,dynamic adhesion,and de-detach characteristics.However,non-covalent adhesives have poor shear strength,and most of the components are still synthetic polymer materials.Moreover,the common problem faced by these adhesive systems is that most adhesives can only be used in dry or semi-wet conditions,and it is difficult to use directly in the water environment.At present,a series of underwater adhesives were prepared by recombinant proteins.It is a great challenge to further study the mechanism of interface adhesion,which was attribute to the long synthetic term,complicated purifying process,low yield,and poor cost-efficiency.Therefore,on this basis,we successfully prepared underwater adhesives or coacervates for supramolecular polymerization of short peptides with certain mechanical strength by using cationic short peptides or amino acids as building blocks and multivalent nano-crosslinking agents as bonding units through ion co-assembly supramolecular polymerization.The stability and functional properties of the adhesives were improved by improving the structure and type of small molecules.Still,there is plenty of room for growth.For example,1)a deeper understanding of design laws is needed,including the design and functionalization of short peptide sequences;2)study on the adhesion mechanism of short peptide system;3)underwater crosslinking curing problem:the cohesion is improved through underwater in-situ curing,thus further improving the bonding strength;4)illntelligent response characteristics of underwater adhesive:physical response(light,heat,magnetic,electric,pressure,etc.)and chemical response(redox response);5)development of biocompatible adhesives:improve the selection of cross-linking agents.Therefore,based on the above problems,in this research paper,through the design and optimization of cationic short peptide and multivalent nano crosslinking agent,the following works were performed:Firstly,in order to further understand the mechanism and thermodynamic characteristics of peptide with cationic units and multivalent crosslinking agents,a class of p H-responsive adhesive coacervate was successfully prepared by the electrostatic attraction of anion and anion as well as the salt-bridge hydrogen bonding between the main chains of amino acids by using simple and readily available basic amino acids as the building blocks and polyoxometalates with multiple bonding sites as bonding units.Isothermal calorimetric titration(ITC)experiment further confirmed that the supramoleular polymeration process was driven by enthalpy and entropy,and was a spontaneous process.In addition,we systematically studied the influencing factors of the coacervate,such as temperature,concentration,molar ratio,p H,and salt concentration.We drew a detailed two-dimensional phase diagram,which laid a foundation for the rational design of amino acid coacervate.More importantly,the coacervate with p H responsiveness can realize the dynamic phase transition between coacervate and adhesives,which will be more conducive to implement interface spreading,adhesion and curing.Therefore,it has been successfully applied as a viscous acid-resistant coating by combing the coacervtae acidity responsive,adhesive properties,and polyoxometalate corrosion resistance.Secondly,in order to further balance the relationship between interface adhesion and bulk phase strength,we successfully constructed a class of self-curing supramolecular underwater adhesives with redox response by rationally designing short peptides containing cysteine residues and polyoxometalates with excellent oxidation performance as the building elements.Furthermore,the antibacterial properties of polyoxometalates were further utilized to explore their functional applications as sticky antibacterial coatings.Firstly,in order to achieve both interface adhesion and bulk cohesion curing,we optimized the sequence of short peptides,designed and synthesized a short peptide carrying lysine residues and cysteine residues.By co-assembly with K₅BW₁₂O₄₀ in an aqueous solution,the reduced adhesive coacervates were successfully prepared.H₅PMo₁₀V₂O₄₀ and tripeptide were co-assembled in an aqueous solution to obtain oxidized adhesive coacervates.In situ mixing with a double syringe,a high cohesive underwater adhesive was formed by oxidation covalent crosslinking of the sulfhydryl group in cysteine with H₅PMo₁₀V₂O₄₀ through redox reaction.Rheological results showed that the individual coacervate had lower modulus and viscosity,whereas the modulus and viscosity of the cured adhesives were significantly increased after curing.Similarly,the underwater lap shear strength further indicated that the shear strength of the cured adhesive is significantly higher than that of the single coacervate.Experimental results showed that the two redox complementary coacervates could achieve stable interfacial spreading and bulk curing within 90 min.Finally,a novel adhesive antibacterial coating was developed by utilizing the antibacterial properties of polyoxometalates and the adhesive synergy.This complementary redox strategy will provide an innovative standard for improving shear adhesive performance of underwater adhesives.Because of its relatively short amino acid sequence,curable peptide adhesives can also be used as a simplified model,which is of great significance to study the bonding mechanism of biomimetic adhesives and guide the rational design of biomimetic adhesives.Thirdly,to improve the biocompatibility of underwater adhesives,further develop their functional applications,the choice of ends was designed and synthesized with arginine,personal relationship among hydrophilcity and hydrophobicity arranged alternately short peptide.Taking advantage of multiple non-covalent function assembly with biological small molecules glycyrrhizic acid(GA),a class of biocompatibility,good degradability of biological medical adhesive was fabricated.Transmission electron microscopy(TEM)and atomic force microscopy(AFM)experiments showed that the individual GA molecules self-assembled to form the worm-like nano-fiber structure by hydrophobicity.Experimental results of Zeta potential showed that the net potential of GA in aqueous solution is-55.6m V,indicating that GA exhibits in aqueous solution in the form of aggregate,and the aggregate surface has a large number of negative charges.The supramolecular underwater adhesive was formed by electrostatic attraction,hydrogen bonding and hydrophobicity.More importantly,because of its good biocompatibility and excellent adhesion with biological tissue,it successfully realized the seal and repair function of the dura mater,which provides a new idea and method for further realization of short peptide adhesive as biomedical adhesive.In conclusion,in this research paper,we mainly use cationic short peptides as building motifs,and use non-covalent forces to co-assemble with different multivalent nano-crosslinking agents in an aqueous solution to successfully construct acid-responsive adhesive coacervate,redox complementary response underwater adhesives and biomedical supramolecular underwater adhesives.It has important guiding significance for the design and functional application of short peptide underwater adhesive materials.