Poly(lactides) co-electrospun with carbon nanotubes: thermal and cell culture properties

Abstract

Multi-walled carbon nanotubes (MWCNTs) often serve as an effective nucleating agent that facilitates the crystallization of semicrystalline polymers. Here we study the influence of MWCNTs on thermal and structural properties of electrospun fibers of Poly-lactide (PLA), a biodegradable and biocompatible thermoplastic polymer. MWCNTs were co-electrospun with either poly(l-lactide) (PLLA, with 100% l-isomer) or poly (d-lactide) (PDLA, containing 4% d-isomer) in weight ratios ranging from 1.0 to 4.0wt.% MWCNT. Electrospun fibers had average diameters below one micron, and addition of MWCNTs reduced the average fiber diameter and narrowed the diameter distribution. Using heat capacity measurements, the crystal, mobile amorphous, and rigid amorphous fractions were evaluated in MWCNT-containing PLA fibers. More rigid amorphous fraction was observed upon increasing the MWCNT concentration to 1.0wt.% due to the restricted polymer chain mobility induced by MWCNTs. However, at the highest concentration of 4.0wt.% MWCNTs, the crystal and rigid amorphous fractions were both reduced due to MWCNT aggregation. Fibers were assessed for their efficacy as substrates for growth of human umbilical vein fibroblasts. Cell culture results of fibroblasts plated on oriented PLLA fibers indicated cells grew preferentially in the same direction as the fiber orientation. Cell metabolic activity was reduced, compared to a control substrate, with greatest reduction occurring in crystalline fibers, or those containing MWCNTs.