Optimization of electrospinning parameters to fabricate
aligned nanofibers for neural tissue engineering

Abstract

Electrospinning is the most promising method to fabricate random as well as aligned fibers in nanoscale. The scaffolds with embedded nanofibers have successfully been used for in vitro proliferation and differentiation of stem cells into various lineages for specific tissue engineering. Currently, a lot of effort is being put to optimize electrospinning set up for producing aligned nanofibers since scaffolds with aligned nanofibers can be propagative to neuronal cells for engineering neurons. In case of neuronal damage, aligned nanofibers have the potential to guide the axonal regeneration and neurite extension in a polarized manner on the parent nerve fiber leading to regeneration. The main objective of current study is to electrospun the aligned nanofibrous scaffolds from poly-ε-caprolactone (PCL) for its potential application in neural tissue engineering. Briefly, for electrospinning of PCL solution, the correct solvent system,their ratios and other process parameters were optimized. A solvent system of chloroform and methanol was used with an initial ratio of 3:1respectively. The electrospinning trials were conducted with a fixed plate distance of 10cm, the flow rates range of 1-2ml/hr(0.5 ml increment), and an applied voltage of 10- 14 KV (2 kV increment) for 30 second in each run. Determining the best process parameters, the polymer solution tested at 6-12% (w/w) of PCL (2% increment). Within each concentration three different solvent systems (chloroform: methanol, dichloro methane: dimethyl formamide, chloroform + dichloro methane: dimethyl formamide and chloroform: dimethyl formamide) and within each solvent mix five different solvent ratios (1:1 to 5:1) were tested. Post electrospinning characterization by optical and scanning electron microscopes (SEM) concluded the best optimized parameters as: a solvent system of chloroform + dichloromethane: methanol (3:1 ratio) , 10% (w/w) PCL, 10cm of spinning distance, a flow rate of 1ml/hr and an applied voltage of 12 KV. With these parameters, fibers produced were uniform, continuous and the average diameter was in a range of 350 to 480nm. The best set of parameters was used for electrospinning aligned nanofibers with an array of in house designed collectors i.e. air gap metallic strip collector, parallel magnetic collector, frame collector and copper grid collector. The optical microscopy and SEM analysis showed that the copper grid collector produced best aligned nanofibers that were further confirmed by Fast Fourier Transformation (FFT) of image. The range of fiber diameter produced was 330 to 560 nm. The current study established the best electrospinning parameters for PCL and the best collector set up to produce aligned nanofibers for neural tissue engineering applications.