| When the polymer fiber diameter decreased from micron to nanometer level, there willbe a series of excellent characteristics, which make the polymer nanometer fiber and itsproducts have high research and potential application value in many fields. Theelectrospinning technology is one of the most economic methods to prepare nano-fiber.,which is continuous, uniform and have good performance. So this technology has become thefirst choice to prepare nano-fiber and its products. However, different research objectivesrequire the polymer with different types, performances and functions. In order to maximizethe function of the research material and make up for the lack of performance of a singlematerial, the research object is expanded from one kind of polymer to two or more kinds. Thepolylactic acid (PLA) polymer with good biocompatibility was used as a substrate, andmixtured with Tea Polyphenol, which has many functions and various pharmacological effects. The PLA/TP composite nanofiber membrane was prepared by electrospinning process. Thespinning process and the performance were studied, and the main research contents andconclusions have the following several parts:(1) Determine the best parameters of electrospinning the PLA/TP composite nanofibermembranes. Firstly, through the scanning electron microscopy (SEM) to observe and analysisthe morphology of the fibers, the optimal experimental parameters of each experimentalcondition were determined. The results showed that: the quality score of PLA and TP hasgreat influence on the spinning process. The SEM images show when the mass fraction ofPLA is less than or greater than10%, the spinnability and the diameters of the fibers can’t bethe best, so to determine the solute mass fraction is10%. Secondly, the aim is to determinethe spinning solvent. Through the SEM images and considering the experimental efficiencyand effect, the electrospinning solvent was the mixed solution of dichloromethane (DCM) andN, N-two dimethyl formamide (DMF), and the volume ratio (V/V) was7/3. Throughstudying the influences of different spinning conditions on the morphologies of PLA/TPcomposite nanofibers, and using the SEM images and distributions of the fibers’ diameters,the spinning voltage, spinning distance and spinning speed were determined as18kV,17.5cmand0.8mL/h. Finally, to research different quality blending ratios of PLA and TP have theinfluence on the compound nanofibers. Through analysising the influence of different qualitymixed ratio on the electrospinning solution’s properties, including solution viscosity,conductivity, surface tension. And through comparing the SEM images and distributions ofthe fibers’ diameters, we can draw the conclusion: the fiber diameter will be smaller with theincrease content of TP.(2) Research on the structure and performance of the PLA/TP composite nanofibrous me-mbranes. The PLA/TP composite nanofibrous membranes were prepared in the condition ofdifferent mixing ratio of PLA/TP. The structures of the membranes were characterized byFourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC),and the wetting properties, mechanical properties and pore size distribution were tested andanalyzed. The results showed: the two components of PLA and TP existed in the composite membranes, and bonded together by valence bond. The DSC test results showed that: with thechange of the two composites in the nanofibrous membrane, the crystalline structure, glasstransition temperature (Tg) and melting temperature (Tm) would also change. The contactangle test results showed that: with the decrease of PLA and the increase of TP in thecomposite nanofibrous membranes, the wettability of the membranes was improved. Themechanical testing results also showed that: the tensile strength and elongation of thecomposite nanofibrous membranes had a downward trend with the decrease of PLA and theincrease of TP in the membranes. The pore size analysis results make us understand that: withdifferent quality of mixing ratio of the composites, the pore size and distribution conditionsare different in nanofibrous membranes.(3) Test the antibacterial property and study on the mechanism of the PLA/TP compositenanofibrous membrane. Through testing the composite nanofibrous membranes with differentquality ratios of PLA and TP by oscillation flask method and inhibition zone test, the resultshowed that: the antibacterial property of the composite nanofibrous membrane wasimproved with adding TP, and the effect was more obvious with the increase of TP content.The antibacterial rate and bacteriostatic ring width of the Staphylococcus aureus (S. aureus)and Escherichia coli (E. coli) membranes were increased by76.4%,76.3%and1.96cm,1.5cm. The antimicrobial modle of PLA/TP composite nanofibrous membranes was proposedbased on the molecular theory. The lipid bilayer was adsorbed and protein molecule wascomplexed by phenolic hydroxyl group, then the integrity and permeability of cell membranewas damaged. The test results of flow cytometry (FACS) and transmission electronmicroscopy (TEM) showed that: one of the antibacterial mechanisms is to destroy theintegrality of cell membrane, which result in the death of bacteria.(4) Study on the sustained-release properties of PLA/TP composite nanofibrous membrane.The release modle of TP in PLA/TP composite nanofibrous mambranes was proposed. Theabsorbances at different concentration of TP at the maximum wavelength were measured, andthe TP standard curve equation was obtained by analysis software. According to the equationand the absorbance of each solutions, the sustained-release curve of the PLA/TP compositenanofibrous membranes within72hours was drawn, which showed the composite film hadsustained-release property. After degradationof8weeks, the pH value of50/50compositefilms was maintained at about7.1. At the same time, the SEM images and the pH valueshowed that PLA was a good biodegradable carrier and had a certain role in promoting thesustained-release property. |
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