The Preparation Of Functional Electrospun Nanofibers And Their Applications In Tissue Engineering

Tissue engineering is one of the new subjects which combined Biology, Material Science and Engineering, aimed to reestablish or repair human tissue and organs. Ideal tissue engineering scaffolds is biomimicing the natural extracellular matrix (ECM) and promoting cells and tissue growth; as such it can be matched by host tissue. Natural ECM is composed of a crosslinked porous hydrogel network of collagens with diameters ranging from50-500nm and embedded in glycosaminoglycans. Electrospun fibers, with diameters in the range of nanometers to micrometers, having extremely high specific surface area, porosity and capturing sites for cell adhesion, proliferation, migration and differentiation, could mimic ECM microstructure.The purpose of the present study is to prepare functional nanofibrous tissue engineering scaffolds by electrospinning. It included two parts:Firstly, the reaction of nanofibers based tissue engineering scaffolds and cells or tissue has been investigated.Surface roughness has been shown to be an important determinant of cell adhesion and proliferation. Studies on electrospun nanofibers have thus far focused on using non-beaded nanofibers as it has been assumed that it mimics ECM and thus improve cell adhesion and proliferation. However, the real effect may be due to surface roughness. Therefore in this study, electrosprayed beads, more beaded nanofibers, less beaded nanofibers and non-beaded nanofibers have been tested for cell proliferation. As a result, the human dermal fibroblasts proliferation on non-beaded nanofibers is much better than that on electrospayed beads and more beaded nanofibers. The morphologies of fibroblasts on the non-beaded nanofibers look better. And we hypothesized that bone marrow derived MSC may attach better on a hydrophilic substrate compared to hydrophobic substrate. PLLA nanofibers and PLLA nanofibers treated with plasma were used to test the BM-MSC capture rate at10min,20min,30min, and60min. From the result, the cell capture rate on hydrophilic nanofibers is significantly higher than that on hydrophobic nanofibers. An implantable graft with pre-seeded cells needs to remain viable and encourage rapid angiogenesis in order to replace injured tissues. We have created a bioartificial adipose graft that is made out of an electrospun3D nanofibrous scaffold and fat tissue. The cells within the bioartificial graft are viable and vascular tubes are present at4weeks while cells in a complete fat tissue have died. The angiogenic potential of the bioartificial graft was demonstrated by capillaries sprouting from it in Matrigel. Improved cell viability and angiogenesis as demonstrated by our bioartificial graft will significantly improve its survivability after implantation.Secondly, the application of bioactive factors loaded nanofibers in tissue engineering.An innovative tissue engineering nanofibrous scaffold with a controllable drug releasing capability has been investigated. The hypothesis is that the nanofibers fabricated by coaxial electrospinning could encapsulate and release sustainedly Tetracycline Hydrochloride (TCH). To testify the hypothesis, nanofibers were prepared by coaxial electrospinning from Poly(L-lactid-co-e-caprolactone)[PLLACL]/2,2,2-Frifluoroethanol (TFE) solutions (as the shell solutions) and TCH/TFE solutions (as the core solutions). In addition, nanofibers of PLLACL-blend-TCH were also prepared as the control by mix electrospinning. The relationship between fibers morphologies and processed conditions in electrospinning were investigated. TCH release behaviors from the nanofibrous mats were studied. The antibacterial properties of aforementioned nanofibers were detected by the Escherichia coli growth-inhibiting tests. The results indicated that the nanofibers prepared by coaxial-electrospinning had the desired and controllable TCH encapsulation/release profile; thus, it could be utilized as both a drug encapsulation/release vehicle and a tissue engineering scaffold.Core-shell electrospun poly(L-lactide-co-ε-caprolactone)[PLLACL]/NGF nanofibers for nerve tissue engineering was investigated. PLLACL as the shell and BSA/NGF as the core in the nanofibers were characterized. Morphologies were observed by SEM, TEM and Fluorescence microscope, mechanical properties and protein released behavior of nanofibrous mats were also examined. The results demonstrated that the release behavior of protein is stable and sustainedly form core-shell nanofibers, however, protein released from blended electrospun nanofibers present a burst release behavior at the beginning of the release process. The bioactivity of released NGF from core-shell nanofibers was verified by testing the differentiation of rat pheochromocytoma cells (PC12). The NGF released could induce the axon differentiation of PC12. The functional nanofibers have a great potential in nerve tissue engineering.A novel tissue engineering scaffold/drugs delivery carrier with the capability of loading and controlled release drugs has been developed by emulsion electrospinning. Rhodamine B and Bovine Serum Albumin (BSA), as model drugs, were successfully incorporated into nanofibers. The morphology of pure PLLACL nanofibers arid composite nanofibers of encapsulated drugs was observed by SEM. The nanofibrous mats loaded drugs were characterized by water contact angle measurement and X-ray diffraction. In vitro, release behaviors of Rhodamine B and BSA from composite nanofibrous mats were also investigated. The drug in the oil phase released fast at the beginning, however, the drug in the water phase released in a stable and sustained manner. The results indicated that the encapsulated drugs in fibrous mats made from emulsion electrospinning could be control released by adjusting the emulsions.It is limited that tissue engineering scaffold or drugs delivery carrier with the capability of incorporation and controlled release of dual drugs by means of emulsion electrospinning, because of one drug is water-soluble and the other drug is oil-soluble. In this study, we introduced coaxial electrospinning to load dual drugs. Rhodamine B and Bovine Serum Albumin (BSA) were successfully incorporated into nanofibers by means of blending or coaxial electrospinning. The morphology of composite nanofibers was studied by SEM and TEM. The composite nanofibrous mats made from coaxial electrospinning were characterized by X-ray diffraction. In vitro, BSA and Rhodamine B release behaviors from core-shell nanofibrous mats were tested. From the drug release profiles, it shows that where the drug or protein is put into (into the core or shell of the nanofibers) can affect the drug release profile in the coaxially electrospun fibers. The results imply that that the drugs release profile in composite fibrous mats made from coaxial electrospinning can be controlled by altering the coaxial electrospinning process and has significant implications for a wide range of applications such as tissue regeneration, combined therapies or even cancer treatments.Electrospun nanofibers mimic the native extracellular matrix of the bone and fascinated considerable interest in bone tissue regeneration. The strategy of this study is to fabricate a novel poly(L-Lactide-co-caprolactone), PLLACL/collagen nanofibers blended with bone morphogenetic protein2(BMP2) and dexamethasone (DEX) for the controlled release for bone tissue engineering (BTE). The morphology, surface hydrophilicity, and mechanical properties of the PLLACL/collagen nanofibrous mats were analyzed by Scanning Electron Microscope (SEM), water contact angles and mechanical stability. The performance of scaffolds was investigated by viability and morphology of human mesenchymal stromal cells (hMSCs) on the nanofibrous mats for bone tissue regeneration. The PLLACL/collagen blended fibers are proved for the hMSCs cultures and then BMP2and DEX were successfully incorporated into PLLACL/collagen nanofibers by means of blending or coaxial electrospinning. In vitro dual growth factors release behaviors from PLLACL/collagen nanofibrous mats were investigated by UV spectrophotometer. Release profiles showing that the controlled release of growth factor better in core/shell nanofibers compared to the blended electrospun fibers. The observed results proved that the BMP2and DEX controlled release are possible to promote hMSCs to osteogenic induction for bone tissue engineering. The results imply that PLLACL/collagen nanofibers encapsulated with dual drug and/or protein have a great potential in bone tissue engineering.