Optimizing Process Variables to Control Fiber Diameter of Electrospun Polycaprolactone Nanofiber Using Factorial Design
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Optimizing Process Variables to Control Fiber Diameter of Electrospun Polycaprolactone Nanofiber Using Factorial Design Saida P. Khan1, Kadambari Bhasin2, Golam M. Newaz1 1 Mechanical Engineering, 2 Biomedical Engineering, Wayne State University, Detroit, MI 48202, U.S.A. ABSTRACT In the electrospinning process, fibers ranging from 50 nm to 1000 nm or greater can be produced by applying an electric potential to a polymeric solution [1, 2]. Our group has studied the fabrication of electro-spun Poly-caprolactone (PCL) nanofiber consisting of a range of fiber diameter (nm-um) and pore sizes. PCL is a biocompatible, FDA approved and biodegradable [3, 4] polymer. As a solvent we have used 2,2,2-trifluoroethanol (TFE) for its biocompatibility, conductivity and high dielectric constant. The electrospinning technique consists of a simple setup with a number of variables working in a complex and unpredictable way. The variables affecting fiber diameter are polymer concentration in the solution, flow rate, applied voltage, tip to collector distance, diameter of the needle/capillary, polymer/solvent dielectric constant etc. In our study we have found that concentration of the solution and molecular weight of the polymer are the most important parameters for forming the nanofibers and viscosity is important for the fiber diameter. To optimize so many variables to control the fiber diameter, we have used the factorial design method. The study is important for the fabrication of biomimetic scaffold for vascular implant and tissue engineering application. INTRODUCTION Using electrospinning technique it is possible to create both random and aligned nanofibers ranging from 10 nm to beyond 10 μm in diameter. A vast range of synthetic and natural polymers in pure or blended solutions, as well as melts, have been electrospun to form nanofibers. The resulting surface can mimic the extracellular matrix morphology [5, 6]; having nanoscale topography with high porosity and fine fibers (5-500 nm) in order to enhance cell attachment and proliferation for the regeneration of the natural tissues. A wide variety of biodegradable and biocompatible polymers have been developed for medical applications specially in cases where a temporary or short term implant is needed, e.g., sutures, substrates for tissue regeneration and carriers for drug and gene delivery [7-11]. Among them, Polycaprolactone ( PCL) an FDA approved and biodegradable polymer has been widely studied due to its good biocompatibility, slow biodegradability and convenience to further functionalize PCL molecule [3, 4, 12-14]. It has been demonstrated that the molecular structure and morphology of biodegradable polymers and their copolymers can play a major role in the degradation and mechanical properties of the final products [15, 16]. Other than its use as a temporary support for tissue regeneration, electrospun non-woven nanofiber membranes have been demonstrated usefulness in multiple biomedical applications including postoperative local chemotherapy[17]. In general, the process
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