Study On Preparation And Antifouling Performance Of Bio-organic Metal Materials Modified By Bio-peptides

Biofouling is widespread in many areas such as ships,pipelines,food packaging,aquaculture cages and medical devices.The antifouling properties of material surfaces are closely related to their surface physical/chemical properties.The formation of the biofilm is the initial and key stage of biofouling,it is beneficial to the antifouling if the biofilm formation is prevented.In this study,304 stainless steel was chosen to be modified with peptides to generated modified bio-organic metal materials.The properties of modified surface were then characterized.Escherichia coli(E.coli),Staphylococcus aureus(S.aureus),Phaeodactylum tricornutum,Chlorella pyrenoidosa and Navicula sp.were selected to assess the antifouling properties of the modified surfaces.Peptides were further optimized to improve antifouling capacity of metals.The obtained results were as follows:The attachment of bacteria and the formation of biofilm on material surface are the initial stages of biofouling.Surfaces with nanoparticle can effectively reduce bacterial attachment.Silver nanoparticles(AgNPs)have been known to have a broad spectrum antifouling activity.In this study,in situ generation of AgNPs on the surface of dopamine modified 304 stainless steel(DA-SS AgNPs)layer by layer in weak alkaline aqueous solution was reported.Field emission scanning electron microscope(FE-SEM),Atomic force microscope(AFM)and X-ray photoelectron spectroscopy(XPS)were utilized to analyze the surface morphology and chemical composition of the modified stainless steel.The results demonstrated that the surface of stainless steel was successfully coated with polydopamine and AgNPs.Antimicrobial assay showed that modified surface possessed the ability of resistance of E.coli and S.aureus.The presence of silver offers the coatings excellent capability to inhibit effectively the adhesion of marine algae Chlorella pyrenoidosa,Phaeodactylum tricornutum and Navicula sp..This strategy exhibited a realistic paradigm for further improving the antifouling performances of materials.Some metal affinity peptides can reduce the adhesion of the metal surface by modifying metal surfaces,thereby reducing the attachment of fouling organisms.A direct surface modification between peptide solution with different concentrations and stainless steel was performed,and the reaction mechanism was explained by simulation of the modification process.The optimal modification concentration of peptide solution was obtained by the results of surface water contact angle,surface hardness and the elements of modified surface.Under the optimal concentration,peptide-modified stainless steel was prepared through the reaction between peptide and 304 stainless steel.Results of SEM-EDS,Fourier Transform infrared spectroscopy(FTIR)and XPS demonstrated that the peptide was successfully bound on stainless steel surface.Antimicrobial activity of samples surface was tested against S.aureus.The results illustrated that the peptide treated samples surface possess significant antimicrobial property.Dopamine is a common coupling agent which was used to bind the peptides to the surface of 304 stainless steel,and the dopamine-linked biopeptide modified surface was obtained.XPS analysis confirmed the optimal dopamine concentration was 40 ?g/mL in the coupling reaction.Element analysis and the robustness assay showed that dopamine and the peptides had bound to the steel surfaces firmly,and the wettability of the sample surface was changed.S.aureus attachment experiments demonstrated that the modified surface of dopamine-linked biopeptide has antibacterial and anti-biofilm properties.The effects of the surface microstructure on the surface antibacterial properties of the material were studied using 304 stainless steel surface treated with different particle size sandpapers.The steel sample surfaces polished with 600 # sand paper exhibited stronger antibiofilm capacity than others after peptide modification.The conclusion can be drawn from the parameters of the sample surface,which is consistent with the attachment point theory.Surface activation can make the surface more active and facilitate the modification of the surface of the sample.304 stainless steel with hydroxylated surface was obtained by modifying with "piranha" solution.After treatment with silane coupling agent and hydroxysuccinimide,the antibacterial peptide Maganin ? was covalently adhered on the material surface,which was confirmed by SEM-EDS,XPS,and surface contact angle results.Antimicrobial tests were performed on the modified samples using S.aureus and E.coli.The results showed that the amount of biofilm and bacteria on the stainless steel surface decreased after modification with Maganin ?.Viola philippica is a common Chinese herbal medicine rich in macrocyclic oligopeptides(cyclotides).The cyclotides have antibacterial,insecticidal and antiviral properties.In order to obtain green antimicrobial peptides,three macrocyclic cyclotides were extracted from Viola philippica by high performance liquid chromatography(HPLC),and the structure and amino acid sequence of the cyclotides were detected and compared by mass spectrometry.In the coupling of dopamine,cyclotides were firmly bonded to 304 stainless steel surface.The parameters of the modified surface were analyzed using FTIR and contact angles.The results showed that dopamine and cyclotides were combined on the surface of the sample,and the surface contact angle was reduced.Bacterial attachment assays of cyclotides modified surfaces were conducted using S.aureus,which proved that the modified surface of the cyclic peptide had antibacterial properties.SEM images of bacteria morphology on the surface of the sample showed that the cyclotides treated surface destroyed the integrity of the bacterial cells,thereby achieving the purpose of inhibiting bacterial adhesion.The results of this thesis provide a new method and new attempt in the field of biological antifouling,contributing to the green antifouling of ships.