Preparation and antibacterial performances of silver-copper bimetallic nanoparticles/polylactic acid composite nanofiber membranes
Objective In the past few decades,the increase of bacterial antibiotic resistance worldwide has posed a serious threat to public health.The research aims to develop green,safe and durable polylactic acid(PLA)antibacterial textiles to protect wounds from the influence of drug-resistant bacteria.In order to develop a green,safe and durable antibacterial textile,PLA were blended with silver-copper bimetallic nanoparticles(Ag-Cu NPs)to prepare Ag-Cu NPs/PLA composite nanofiber membranes with different composition.Method Silver and copper nitrates first were reduced using ascorbic acid by green synthetic method to obtain Ag-Cu NPs.Then,Ag-Cu NPs were blended with PLA spinning dope to prepare Ag-Cu NPs/PLA composite nanofiber membranes with different compositions by electrostatic spinning.The morphologies,structures,hydrophilicities and antibacterial properties of Ag-Cu NPs/PLA composite nanofiber composites were characterized and analyzed by using scanning electron microscopy,X-ray diffraction,Flourier transform infrared spectroscopy,water contact angle testing and antibacterial testing.Results Ag-Cu NPs presented an irregular spherical shape with a particle size of about 32 nm.PLA electrospun nanofibers had a uniform diameter and a large number of tiny pores appeared on the fiber surface.Compared with PLA nanofibers,the average fiber diameter of Ag-Cu NPs/PLA composite nanofiber membrane decreased,and the average fiber diameter increased with the increase of Ag-Cu NPs concentration.Ag and Cu elements appeared on the surface of the composite nano-electrospinning membranes and uniformly distributed along the fiber diameter direction,indicating that Ag-Cu NPs were encapsulated by PLA matrix.Compared with PLA,the XRD diffraction peaks belonging to Ag and Cu appeared in the XRD patterns of Ag-Cu NPs/PLA composite nano-electrospinning membranes.The FT-IR spectrum of PLA electrospun nanofiber membrane showed the typical characteristic peaks of PLA.The infrared spectra of Ag-Cu NPs/PLA composite nanofiber membranes were similar to the pure PLA electrospun nanofiber membrane,indicating that there exists only physical interaction between Ag-Cu NPs and PLA matrix.The pure PLA electrospun nanofiber membrane with a water contact angle(WCA)value of about 135° displayed the poor hydrophilicity.The WCA value of Ag-Cu NPs/PLA composite nanofiber membranes slightly decreased compared with pure PLA electrospun nanofiber membrane,meaning the hydrophilicity of the composite nanofiber membranes increased.Pure PLA electrospun nanofiber membrane showed very limited antibacterial ability against Staphylococcus aureus and Escherichia coli.The antibacterial efficiencies of the Ag-Cu NPs/PLA composite nanofiber membranes against these two bacteria were significantly increased with the increasing of Ag-Cu NPs concentration.When the dosage of Ag-Cu NPs was 7%,the composite nano-electrospinning membrane showed high antibacterial activity,and the antibacterial efficiencies for both Staphylococcus aureus and Escherichia coli reached 99%.Conclusion Ag-Cu NPs/PLA composite nanofiber membranes had excellent antibacterial activity against Staphylococcus aureus and Escherichia coli.When the Ag-Cu NPs dosage was 7%,the antibacterial efficiencies of Ag-Cu NPs/PLA composite nanofiber membrane against both Escherichia coli and Staphylococcus aureus could reach 99%.It is expected that our studies may provide some theoretical reference for the application of PLA nanofiber membrane on the biomedical field.