Studies On Preparation And Properties Of Amino Acid Based Wet Adhesives

Biological adhesives have been widely used in the field of tissue repair due to their good biocompatibility,flexibility and adhesion properties.However,the hydration layer on the substrate surface will reduce the interface interaction between the adhesive and the substrate in humid environment,leading to wet adhesion performance decline or even failure.In order to improve the wet adhesion performance of adhesives,many studies have designed to introduce catechol groups into adhesives,which can form covalent bond or non-covalent interaction with the substrate surface（such as hydrogen bond,electrostatic interaction,hydrophobic interaction,ionic bond,etc.）to achieve wet adhesion.However,partial oxidation of catechol can produce cytotoxic reactive oxygen species,and its effect is usually stronger in non-physiological conditions.Therefore,it is of great significance to develop wet adhesives that have strong comprehensive properties in physiological environment without cytotoxicity.Thus,amino acid-like monomer,N-acrylicylglycine（ACG）was selected as the basic unit in this thesis.In order to improve adhesion and mechanical properties,hydrophobic and amphoteric structures were introduced into the chain to prepare hydrogel adhesives.The swelling properties,degradation properties,mechanical properties,self-healing properties,wet adhesion properties,biocompatibility and antibacterial properties were investigated.1.Hydrophilic N-propenylglycine（ACG）and hydrophobic N-propenylphenylalanine（ACP）were synthesized from glycine and phenylalanine,and then P（ACG-ACP）hydrogel was then prepared through copolymerization.A series of P（ACGx-ACPy）hydrogel with different hydrophilic and hydrophobic ratios were obtained by changing the ratio of the two monomers.Proton Nuclear magnetic resonance（¹H NMR）and Fourier infrared spectroscopy（FTIR）were used to demonstrate the synthesis of the two monomers and their copolymers.The wet adhesion of P（ACGx-ACPy）hydrogel adhesive was detected by lap-shear and tensile models.When the molar ratio of monomer was 1:1,the highest wet lap-shear adhesion strength and the wet tensile adhesion strength were 80.2 k Pa and 103.5 k Pa,respectively.Compared with commercial fibrin glue（8.0 k Pa）,the wet adhesion properties were improved nearly 9 times and 12 times,respectively.The hydrophobic PACP chain segment can remove the interfacial hydration layer and promote the infiltration of adhesive and substrate,thus improving the wet adhesion of hydrogel adhesive.After 30 days of in vitro degradation,the degradation rate of P（ACGx-ACPy）hydrogel reached more than 40%,indicating that it had degradability.Cytotoxicity test showed that P（ACGx-ACPy）hydrogel had almost no effect on cell proliferation and had good cytocompatibility.2.Antibacterial property is of great significance for preventing wound infection and inflammation and promoting wound healing.Therefore,P（ACG-SBMA）hydrogel was prepared by copolymerization of methyl acryloethyl sulfobetaine（SBMA）and ACG.By changing the molar ratio of the two monomers,a series of P（ACGx-SBMAy）hydrogel with different structures were obtained and characterized.The wet adhesion strength of P（ACGx-SBAMy）was tested by lap-shear and tensile models,when the molar ratio of monomer was 5:1,the wet lap-shear adhesion strength and wet tensile adhesion strength reached the maximum,which were 59.7 k Pa and 58.2 k Pa,respectively.Compared with commercial fibrin glue（8.0k Pa）,the wet adhesion strength of P（ACGx-SBMAy）was improved by nearly 6 times,which can be used in tissue repair.The cell survival rate was above 90%,indicating that P（ACGx-SBMAy）hydrogel had good biocompatibility.The antibacterial performance test showed that P（ACGx-SBMAy）hydrogel had certain antibacterial activity.The highest antibacterial rates of E.coli and S.aureus were 99%and 91%,respectively,after 3 h incubation.3.The use of flexible conductive hydrogel for vital sign detection has received increasing attention in recent years,but it remains a challenge to perform vital sign detection in humid environments.Among the P（ACGx-SBMAy）hydrogel,P（ACG₅-SBMA₁）hydrogel had the best comprehensive performance.Therefore,P（ACG₅-SBMA₁）-Al-X conductive hydrogel was prepared by adding Al³⁺to P（ACG₅-SBMA₁）hydrogel.The lap-shear model test showed that the maximum wet adhesion strength of P（ACG₅-SBMA₁）-Al-24 hydrogel was 70.4 k Pa when the content of Al³⁺was 24%.The conductivity of P（ACG₅-SBMA₁）-Al-X hydrogel was measured by electrochemical workstation.When the content of Al³⁺was 75%,the conductivity reached 1.7×10^-3 S/m.The cytotoxicity test showed that P（ACG₅-SBMA₁）-Al-X hydrogel had less cytotoxicity when the content of Al³⁺was low.The antibacterial performance test showed that P（ACG₅-SBMA₁）-Al-X hydrogel had certain antibacterial activity,and the antibacterial rate of P（ACG₅-SBMA₁）-Al-X hydrogel against E.coli and S.aureus could reach more than 99%after 3 h cultivation.In conclusion,the prepared hydrogel wet adhesives with good biocompatibility,adhesion,antibacterial and electrical properties is expected to be used as biological adhesive,medical dressing,tissue repair and biological monitoring materials.