Interfacial Modification Of Peptide-polymer Conjugates And Its Application In Bacterial Detection,Antibacterial And Antifouling

Bacterial pathogens cause a series of medical and health problems in recent years,which significantly increase the morbidity and mortality of humans and animals.Therefore,the development of bacterial detection and preparation of antibacterial and antifouling materials are particularly vital for preventing bacterial diseases.However,the current detection of bacteria with high cost,long analysis time and the characteristic of unportable and professional are unpractical.In addition,although the bactericidal effect of the bactericide coated materials is remarkable,,it is unfriendly to the environment.In recent years,peptide-polymer conjugates as a new class of soft materials have combined the advantages of peptide with degradability and functional diversity and polymer with stability and processability,which have attracted wide attention.Therefore,in this paper,the corresponding functional interface was prepared by peptide-polymer conjugates in order to carry out relevant research on bacterial detection,antibacterial and antifouling.Firstly,the antibacterial peptide(AMP)was synthesized by solid-phase peptide synthesis,and the side chain amino group of lysine was used as the modification site to modify the side chain of the response peptide LPKTGG and the control peptide LPTKGG,respectively.The side chain of recombinant peptide GGGKA was labeled with fluorescent molecule.All synthetic peptides were characterized by matrix-assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS).Copolymers with different molar ratios of N-isopropylacrylamide(NIP AM)and N-(2-hydroxyethyl)acrylamide(HEAA)were synthesized by reversible addition fragmentation chain transfer(RAFT)polymerization.The side chain of the copolymer functionalized double bond was obtained by reaction with acryloyl chloride.The results showed that the lower critical solution temperature(LCST)of the copolymer increased with the decreased of the molar ratio of NIPAM/HEAA,that is,the LCST of the copolymer can be controlled by regulating the the molar ratio of NIPAM/HEAA,which contribute to the application of thermo-sensitive polymers at different temperature.Secondly,The synthesized materials were then used for interfacial modification by "graft to" and "graft from" respectively.It was confirmed by Fourier transform infrared spectroscopy(FTIR)to each step of interfacial modification by "graft to".The thermo-sensitive hydrogel coatings prepared by "graft from" were a network structure observed by scanning electron microscope(SEM).As the molar ratio of NIP AM to methylenebisacrylamide(BIS)increased,the thickness of the hydrogel coating decreased and the pore size increased respectively.The thermosensitivity of hydrogel coating was characterized by the water contact angle at 4? and 37?,where the hydrogel coating formed by the NIPAM/BIS with molar ratio of 100:1(HP2)had the best thermosensitivity.Finally,the application of the functional interface in bacterial detection,antibacterial and antifouling had been studied.The visual detection of Gram-positive bacteria was achieved via the site-specific cleavaged of responsive peptide by Sortase A and the site-specific attachmented of fluorescent peptide.It was confirmed that the hydrogel coating had good sterilization when the molar ratio of AMP/NIPAM up to 0.5%by LIVE/DEAD bacteria viability assay,and the colony count showed that the bacterial adherence of hydrogel coating modified interface decreased significantly and the minimum adherence of E.coli and Staphylococcus aureus in test group was 4.2%and 9.8%relative to the control group respectively,which proven excellent antifouling efficacy.Meanwhile,the anti-infection ability of the hydrogel coating modified interface was verified by the subcutaneous infection experiment in vivo,and the colony count showed that the thermo-sensitive hydrogel coated implants exhibited 4 ordered magnitudes of adhered bacterial cells and 3 ordered magnitudes of tissue infected bacterial cells lower than that of bare substrate.The cell viability with the molar ratio of AMP/NIPAM in the range of 0-0.5%was higher than 80%by a cell counting kit-8(CCK-8)assay,and the cell viability was basically higher than 90%after incubation with hydrogel coating modified interface for 5 days,indicating good biocompatibility of the hydrogel coating.In summary,this study designed,synthesized and characterized peptides and polymers for preparing the corresponding functional interface and carring out relevant research on bacterial detection,antibacterial and antifouling with desirable results,which will provide a certain reference for the development of bacterial detection and preparation of antibacterial and antifouling materials.