Electrospinning is a simple and versatile technique for producing micro- and nanofibers. It has been shown that electrospun tissue engineering scaffolds mimic the structure of the extracellular matrix of human body tissues. These scaffolds can improve cell attachment behavior and subsequent cell proliferation and differentiation. On the other hand, due to their large surface area to volume ratio and porous morphology, electrospun micro- and nanofibers are potentially useful for the controlled release of therapeutic agents (drugs and therapeutic biomolecules) in human bodies. In this study, electrospinning of poly(L-lactic acid) (PLLA) nonwoven micro- and nanofibrous membranes was investigated. It is known that the morphology and size of a drug carrier could play very important roles in the drug release behavior. Therefore, in the present investigation, a comprehensive study on the fabrication parameters that could affect the morphology and diameter of PLLA fibers was conducted. For electrospinning, several parameters were associated with intrinsic properties of the polymer solution, such as PLLA intrinsic viscosity, polymer solution concentration and solvent used, while other parameters were related to the experimental setup and electrospinning environment, including applied voltage, working distance, needle size, feeding rate, etc. Among these parameters, some solution related factors were important for controlling the fiber diameter. The average fiber diameter decreased from 3.2 μm to 0.6 μm when N,N-dimethylformamide (DMF) was added into a solvent system. While using dichloromethane (DCM) as the solvent, the fiber diameter could vary between 1 μm to 8 μm using different PLLA solution concentrations. Different solvent systems could also affect the morphology of PLLA fibers. On the other hand, most of the apparatus and environment related parameters could help to improve the fiber morphology, but not very significantly. It was also found that the stability of electrospinning conditions may improve the uniformity of PLLA fiber diameter. When lower voltage was applied, although the average fiber diameter increased, the range of variation of fiber diameters decreased. This study shows that PLLA fibrous membranes with a controllable average fiber diameter ranging from 600 nm to 8 μm could be fabricated via electrospinning. These fibrous membranes have the potential as vehicles for the controlled release of therapeutic agents in tissue engineering.

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