Fabrication And Applications Of Functionalized Electrospun Nanofibrous Mats

Electrospun nanofibers have special structures which give them unique properties. Such properties make them useful in many fields and have a broad application prospect, leading to worldwide attention. However, most of spinning raw materials themselves have certain chemical inertness, making nanofibers have limited functions. In this point of view, in order to improve the performance of nanofibers, broaden its application scope, it is imperative to give them functional treatment. Surface modification technology, such as layer-by-layer assembly technology, wet chemistry, liquid phase deposition technology, etc., as a kind of convenient, mature and effective method, has been widely applied in electrospun nanofibers. This paper adopted different surface modification technology for surface modification of nanofibrous mats to get different functions and evaluated its application in the field of biomedicine, catalysis, packing and so on. In this paper, the main research results are as follows:1. The effects of traditional assembly technology and vacuum-assisted assembly technology on the morphology of the composite nanofibers were investigated. Vacuum-assisted assembly technology could make assembling components uniformly deposite on the surface of fibers and well maintain the three-dimensional structure of the fiber membrane. However, the assembling components could not be uniformly loaded on the surface of fibers using traditional assembly method and the structure of nanofibirous membranes changed obviously;2. Cationic polysaccharide(chitosan) and negatively charged yolk protein(phosvitin) used as assembling components were alternatively deposited on the surface of nanofibrous mats. Electrostatic and hydrogen bond interaction were considered as the main driving force. SEM, FTIR, XRD, XPS, TGA, DSC and other methods were combined to characterize the properties of nanofibrous mats;Composite nanofibrous mats have good antibacterial property against E. coli and S. aureus and the antibacterial performance increased with the increase of the number of bilayers. After incubation in simulated body fluid, a layer of hydroxyapatite crystals grew in the surface of nanofibrous mats, and the amount of hydroxyapatite increased with the layer number and the incubation time. Element analysis results showed that calcium phosphorus ratio was 1.50 after 7 days of incubation, lower than Ca/P mole ratio of hydroxyapatite(1.67) which showed that crystals were calcium-deficient hydroxyapatite and similar to natural bone. Experimental results showed that the composite membranes have good biocompatibility, making osteoblasts grow normally on it.3. Tannic acid could form purple complex with Fe3+ combined in phosphoric acid root in phosvitin. Through the interaction of tannic acid and Fe3+, these two components were assembled in the surface of nanofibrous mats through layer-by-layer assembly technology. The structure characterization was evaluated using SEM, TEM, FTIR and XPS and its ability to remove all kinds of free radicals and the performance of the mineralization was investgated.The results showed that:(TA/PV)n composite nanofibrous membranes have excellent DPPH free radical scavenging activities. The increase of the number of bilayers and the outermost components did not have significant effects on the DPPH radical scavenging activity. For hydroxyl radicals, the composite nanofibrous membranes also showed good scavenging activities, and free radical clearance activity enhanced with the increase of the number of bilayers. When the outermost component was tannins acid, composite nanofibrous membranes showed a relatively high scavenging activities. To some extent,(TA/PV)n composite nanofibrous membranes can remove superoxide anion free radicals. With the increase of the number of bilayers, free radical clearance rate increased. However, if tannins acid was the outermost components, the composite fiber membrane showed a relatively weak scavenging activity.A layer of hydroxyapatite crystals grew in the surface of nanofibers after incubation 5 days in simulated body fluid. In the XRD spectrum, the sharp diffraction peak of(002) crystal face indicated that hydroxyapatite was preferentially grew along the c axis. Ca/P mole ratio of hydroxyapatite was 1.44 lower than Ca/P mole ratio of hydroxyapatite(1.67) which showed that crystals were calcium-deficient hydroxyapatite and similar to natural bone.4. The positive charged lysozyme-stabilized Ag nanoparticles(Ag NPs@Lys) were prepared using Na BH4 as a reducing agent at room temperature. The Ag NPs@Lys and tannic acid were alternately deposited on the surface of nanofibers through the interaction between them via LBL assembly technology. The composite hybrid nanofibrous mats were characterized by SEM, TEM, FT-IR, XRD, XPS and so on. The results of antioxidation experiment revealed that the composite mats have good DPPH free radical-scavenging activity. The antioxidant activity has no significant difference with the number of bilayers increased when the outmost component was tannic acid. However, the outmost components markedly impacted the antioxidant activity. The(Ag NPs@Lys/TA)5 mats showed higher antioxidant activity than(Ag NPs@Lys/TA)5.5. the result of microbial inhibition assay indicated that the composite nanofibrous mats had excellent antibacterial activity against E.coli and S.aureus, and the antibacterial activity enhanced with increasing the numbers of bilayers.5. Lysozyme and tannic acid were deposited on the surface of cellulose nanofibers via LBL technology, then the gold nanoparticles were reduced in the Lys/TA shell. the particle size was about 20.78 nm when the concentration of the chloroauric acid solution was low(1 m M). However, the particle size of the gold nanoparticles increased to 40 nm when the concentration of the chloroauric acid solution reached to 5 m M. The morphology, structure and performance of the composite hybrid nanofibrous mats were characterized by SEM, TEM, FT-IR, XRD, XPS and so on. We investigated the catalytic performance of the hybrid nanofibrous mats based on the reduction of 4-nitrophenol(4-NP) with sodium borohydride. The results showed that composite nanofibrous mats revealed excellent catalytic performance, and the catalytic performance enhanced with the number of bilayers increased. The catalytic properties of the mats did not occur significantly reduced. The hybrid nanofiber membranes could be used in water treatment and preparation of 4- aminophenol.6. Ag NPs/Ti O2/h PAN hybrid nanofibrous mats were successfully fabricated via electrospinning technology combined with liquid deposition methods and wet chemistry. Firstly, the PAN nanofibers were hydrolyzed in hot Na OH solution, then obtained the Ti O2/h PAN nanofibrious mats via liquid deposition methods. Finally, silver nanoparticles were deposited on the surface of Ti O2/h PAN nanofibers under ultraviolet light. The performance and structure of namofibrous mats were characterized by SEM, TEM, XRD, XPS, FTIR, TGA and so on. The antibacterial test results showed that h PAN nanofibrous mats and Ti O2/h PAN nanofibrous mats hardly have antimicrobial activity, however, the Ag NPs/Ti O2/h PAN have good antibacterial properties. Composite nanofibrous materials revealed excellent catalytic properties on the reduction of 4-nitrophenol(4-NP) with sodium borohydride.