(781d) Aligned Nanoporous Electrospun Polycaprolactone Fibers for Enhanced Protein Adhesion

Prateik Singh, John J. Lannutti, and W.S. Winston Ho, The Ohio State University

Electrospinning is an inexpensive and effective method for producing nanofibrous scaffolds. These scaffolds have large surface areas and porosity which enhance cell adhesion and growth. The creation of nano-scaled features on the surface of electrospun fibers can significantly improve biocompatibility by selective adsorption of proteins and other biological moieties.  A simple yet effective approach for enhancing the nanotopography of the substrate by increasing the porosity and hydrophilicity of the surface consists of creating nanopores followed by plasma treatment.

In the present work, non-solvent induced phase separation (NIPS) was used in conjunction with vapor induced phase separation (VIPS) to create nanoporous fibers. A ternary system comprising polymer (polycaprolactone, PCL) / solvent (dichloromethane, DCM) / non-solvent (acetonitrile) was chosen such that both the solvent and non-solvent are miscible with water. VIPS was simultaneously invoked with NIPS since the evaporating solvent was replaced by the incoming water, which is a non-solvent for PCL due to its hydrophobic nature.  NIPS occurred, due to the invasion of water into the PCL system caused by the humid air.  Aligned nanoporous fibers were produced on a rotating drum in an environment of 98% relative humidity. Approximately 65% of the fibers spun were aligned within a ± 10º interval of the chosen reference fiber. Scanning electron microscopy (SEM) showed that the mean fiber diameter was approximately 1.8 µm and the pore size distribution was 50 - 300 nm with a mean pore size of 180 nm. A high surface porosity of 74% was observed. The key factors found to affect fiber porosity were relative humidity and solvent/non-solvent ratio. Fiber alignment was found to be mostly dependent on the rotational speed.  

Plasma treatment was used to improve the hydrophilicity and biocompatibility of the otherwise hydrophobic PCL fibers. For plasma treatment, air was used as the medium at 1 torr pressure at 20 cc/min. Four categories of fibers, namely, porous (plasma-treated), non-porous (plasma-treated), porous (no-plasma), non-porous (no-plasma) were used to study the effects of porosity and plasma treatment on the adhesion of BSA (bovine serum albumin) protein to the said fibers. It was found that after 24 hours, porous fibers that were plasma treated, exhibited a 2.5 fold increase in protein retention over their non-porous counterparts. The functionalization of the fiber surface with -COOH and –OH groups due to plasma treatment apparently boosted the effect of nanoporosity in enhancing protein adhesion.