Preparation And Properties Of Antibacterial Materials Based On Polylactic Acid

Based on the requirements of the current sustainable development economy,polylactic acid(PLA),as a naturally derived and renewable biopolymer,has received great attention in the alternative to fossil energy-based plastics and has drawn significant interests in development of textile,packaging,medical industries and additive manufacturing for the advantages of biocompatibility,biodegradability,high strength and excellent thermal processing property.In this study,polydopamine(PDA)and epsilon-polylysine(?-PL)were used to modify the surface of PLA nonwoven fabrics to obtain antibacterial and hemostatic nonwoven fabrics.With the aim of expanding the application of PLA,cellulose acetate(CA)was selected to improve the modulus of PLA liquid ink,and the antibacterial agent was added into the ink in order to endow the 3D-printed composite with the antibacterial performance.The antimicrobial and biocompatible properties of the 3D-printed composites were tested.Graphene oxide(GO)was dispersed evenly into the liquid ink for 3D printing,and the prepared 3D-printed composite could promote the formation of hydroxyapatite(HAp),meanwhile,the 3D-printed composites could cause the inactivation of bacterium.First of all,dopamine was utilized to enhance the hydrophilicity and cell affinity of PLA nonwoven fabrics for various tissue engineering applications including wound dressing via the self-polymerizing adhesion property of the PDA itself.Such a treatment allowed a layer of PDA to be coated on the surface of nonwoven fabrics.This PDA layer greatly improved the surface hydrophilicity and served as a platform for the post-treatment of ?-PL,which introduced hemostatic and antibacterial functions to the surface of the material.The effect of coating PDA and ?-PL on the surface of PLA nonwoven fabrics were observed by Scanning electron microscope(SEM)and X-ray photoelectron spectroscopy(XPS),which demonstrated the successful deposition of PDA and ?-PL.The antibacterial efficacy,in vitro whole blood clotting evaluation,in vitro hemolysis assay,interfacial interaction between hemocytes and nonwoven fabrics and cytocompatibility assay were explored.PLA-PDA-?-PL nonwoven fabrics could cause over 99.00%(6.12 log)and 99.00%(6.04 log)reductions of Staphylococcus aureus(S.aureus)and Escherichia coli O157:H7(E.coli O157:H7),respectively.Moreover,PLA-PDA-?-PL nonwoven fabrics achieved an outstanding hemostatic performance and excellent hemocompatibility.The leaching liquid assay showed that the cell viability could reach more than 80.00% compared with the control group,demonstrating good cytocompatibility of the samples' extracts.Secondly,in order to broaden the application of PLA and realize the transformation from "manufacturing" to "intelligent manufacturing",PLA was applied to 3D printing.PLA/CA inks with different composition ratios were prepared,and the effect of CA content on the rheological behaviors of inks was investigated.All the inks possessed a shear-thinning behavior.Besides,the printability of the prepared direct ink writing(DIW)inks was improved with the addition of appropriate amount of CA,which was due to the formation of hydrogen bonding 3D network between PLA and CA.Afterwards,the antimicrobial agent,1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone(MC)was incorporated into the inks for preventing bacterial infections,and an appropriate addition amount was selected by sodium thiosulfate/iodometric titration to possess excellent antibacterial effect and good cell compatibility at the same time.The surface morphologies of the 3D-printed PLA/CA and PLA/CA-MC composites were observed by SEM and Atomic force microscopy(AFM).As expected,the results revealed the excellent interfacial compatibility of the inks.Additionally,the antibacterial efficacy,shelf life stability,release property of the MC and cytocompatibility were investigated.The 3D-printed composites showed excellent stability and effective antibacterial activity against 100.00% of S.aureus(6.00 log)and E.coli O157:H7(6.26 log)within 30 min.Simultaneously,the antibacterial 3D-printed composites possessed the rapid and lasting sterilization efficacy.Furthermore,in vitro cytotoxicity assay significantly supported the biocompatibility of the 3D-printed composites.Finally,in order to further expand the functionality and application of the PLA/CA inks,GO was supplied and dispersed uniformly in the liquid form ink.SEM and AFM images were collected and the results showed that there were few isolated microscale voids indicating the uniformity of the inks.Biomimetic mineralization on 3D-printed composites was induced by soaking each sample in the 1.5×simulated body fluid(1.5×SBF).Furthermore,the surfaces of the modified 3D-printed composites were investigated by Attenuated total reflection flourier transformed infrared spectroscopy(ATR-FTIR),SEM,Energy dispersive X-ray spectroscopy(EDX)and X-ray diffraction(XRD).The characterization results evidently verified that the formation of HAp,revealing that the occurrence of GO could induce the formation of HAp.At the same time,the antibacterial efficacy and biocompatibility of the 3D-printed composites were tested.The sterilization ratios were 100.00% and 98.92% toward both S.aureus(6.00 log)and E.coli O157:H7(6.26 log)within 30 min,respectively.Furthermore,the cell proliferation assay demonstrated that the 3D-printed composites had excellent biocompatibility.