Fabrication Of Bioactive Tissue Engineering Scaffolds By Blend, Coaxial And Emulsion Electrospinning

Tissue engineering (TE) is one of the new subjects which combined Biology and Material Science. The basic concept of TE is aimed to reestablish human tissue and organs by planting the TE scaffolds with functional cells incorporated into the damaged position. Therefore, the key point and the most challenged technique of TE are to fabricate the tissue engineering scaffolds which could mimic the natural extracellular matrix (ECM):a) the TE scaffolds could mimic the 3-Dimensional structure of natural ECM, b) the scaffolds should be provided with biosafety and biocompatibility, and c) the scaffolds should mimic the functions of natural ECM to accelerate the growth of new cells and induce the formation of new tissue.In the present studies, TE scaffolds which mimic the natural ECM from materials, structure and functions were fabricated by means of electrospinning.The morphology, crystal and chemical structure, mechanical properties, thermodynamic properties, hydrophilicity and biocompatibility of electrospun poly(l-lactide-co-caprolactone) (PLLACL)-Chitosan nanofibers were investigated. The results demonstrated that the mechanical properties get better, the hydrophilicity and biocompatibility get worse with the increasing of PLLACL content in the resultant nanofibers. However, the nanofibers maintained the crystal and chemical structure of PLLACL and Chitosan. Polycaprolactone/Chlorophyllin sodium copper salt (PCL/CSC) nanofibrous mats were successfully prepared by electrospinning from their 2,2,2-trifluoroethanol (TFE) solutions. Systematic investigations were carried out to study the effects of CSC content on the morphology of nanofibrous. The incorporation of CSC with PCL nanofibers resulted in lower strength due to the reason that the CSC could not electrospun into any fibers alone, and the existing of CSC could impact PCL to be fabricated into ultrafine nanofibers. SEM examinations revealed that the PCL/CSC nanofibers with 20%CSC loss their fiber structure. For evaluating of the PCL/CSC nanofibrous mats performance for being the scaffolds which could provide sufficient space for the cells, it was investigated by examination of the weight loss and CSC release tests.The core-shell nanofibers with bioactive factors incorporated in the core part were fabricated with the method of coaxial electrospinning. PLLACL was dissolved into TFE as the outer solution to form the shell part; and the proteins were dissolved into distilled water as the inner solution to form the core part. The coaxial electrospun nanofibers have thinner diameter than plain PLLACL nanofibers and the mechanical properties of coaxial electrospun nanofibers are worse than plain PLLACL nanofibers. To investigate the behaviors of small molecules releasing from coaxial electrospun nanofibers, the blend and coaxial electrospun nanofibers were produced and the release profiles were determined under the same conditions. The results showed that Tetracycline Hydrochloride (TCH, used as model drug) released from coaxial electrospun nanofibers sustainedly and stably, while it releasing from blend electrospun nanofibers showed a "burst" behavior in the initial stage. The concentrations of proteins in coaxial electrospun nanofibers were simulated. In addition, nanofibrous tubes with spiral form were fabricated. The bioactivity of released protein were tested and convinced by testing the neurite outgrowth of a rat pheochromocytoma cell (PC 12).The biofunctional nanofibers with nerve induced bioactivity were produced by means of emulsion electrospinning. Nanofibrous mats which electrospun from a emulsion made of PLLACL solution, Phosphate buffered saline (PBS, pH 7.4) solution contained proteins and Sorbitan Monooleate (Span-80, an emulsifier/surfactant widely used in food products and oral Pharmaceuticals) were investigated. The morphologies of the fabricated nanofibrous mats were examined by scanning electron microscopy (SEM); Span80 was used as surfactant in the emulsion electrospinning, and the distribution of the surfactant in nanofibers was studied. The cell viability on emulsion electrospun nanofibrous mats was evaluated. The release behavior of proteins from core-shell nanofibrous was measured; the bioactivity of released NGF from nanofibrous mats was confirmed by PC 12 neurite outgrowth assay. Furthermore, the forming process of emulsion electrospun nanotibers and the distribution of Span80 in nanofibers were discussed.In this work, a novel type of tissue engineering scaffold or drugs delivery carrier with the capability of encapsulation and controlled release drugs were fabricated by emulsion electrospinning. Rhodamine B and Bovine Serum Albumin (BSA) were successfully incorporated into nanofibers. The morphology of composite nanofibers was studied by SEM. The composite nanofibrous mats made from emulsion electrospinning were characterized by water contact angle measurement and X-ray diffraction. In vitro dual drugs release behaviors from composite nanofibrous mats were investigated. The results indicated that the incorporated drug and/or proteins in composite fibrous mats made from electrospinning could be control released by adjusting the processes of emulsions preparation.Bead/block-type nanofibers were prepared by electrospinning of a ternary system consisting of water, acetone, and PCL. The phase diagram for the ternary H₂O-acetone-PCL system was determined from the cloud point data. The ternary phase diagram can be used to investigate the mechanism of fiber formation, which is unlike that of traditional electrospun fibers. And the formation of bead or block-like nanofibers was caused by the solidification of gelation.In this work, nanofibers for the applications of TE scaffolds were successfully fabricated by blend, coaxial and emulsion electrospinning. The nanofibrous system for duel-drugs (or proteins) incorporation and release was also prepared and investigated.