Functionalized Fibres for Sustained Delivery of Bioactive Substances Via Emulsion Electrospinning

Objectives: Functionalization of electrospun fibres is one of the major challenges for their use as scaffolds in tissue engineering. Most biodegradable polymers require organic solvents for electrospinning, which typically denature the bioactive molecules. Hence, we describe here a modification to the traditional process, called emulsion electrospinning, to circumvent this problem. Methods: Poly(caprolactone) (PCL) was dissolved in chloroform at different concentrations, with Span 85TM added as an emulsifier. The dispersed phase consisted of albumin and alkaline phosphatase (AP) dissolved in PBS. Alternatively, aqueous Eosin-Y solution was used for fluorescence microscopy. Stability of emulsions over time was studied using spectrophotometry. Fibre morphology was observed using scanning electron microscopy (SEM). For release kinetic studies, protein concentration was measured using Bradford assay. AP activity was measured using p-nitrophenyl phosphate as the substrate.

Results: The stability of emulsions showed a distinct dependence on the polymer concentration in the solution with an optimum range between 15% - 20w/v PCL. SEM observations of fibre morphology also confirmed this range to be the most suitable for electrospinning. The proteins were released in a sustained manner from the fibres. AP released from the fibres retained up to 70% specific activity at day 3, indicating that the proteins did not denature during the process.

Conclusions: A method was developed to produce functionalized polymer fibers using emulsion electrospinning. Best results were obtained with emulsions having PCL concentrations between 15% and 20%w/v. Using alkaline phosphatase, it was shown that the released enzyme was active and did not denature extensively during the process. Release of proteins over a longer period, as well as experiments to determine the cytocompatibility are currently in progress.