Chitosan/Polycaprolactone electrospun biodegradable scaffolds for Cardiovascular Tissue Engineering

Introduction:

Polycaprolactone (PCL) and chitosan (CS) are polymers with attractive properties (excellent biocompatibility & degradation). However their mechanical properties seperately do not satisfy the needs for cardiovascular tissue engineering. In the present work we aimed to optimize electrospinning parameters to obtain a flexible PCL/CS polymeric scaffold, with combined nano- and micro-fiber architecture and appropriate mechanical properties for cardiovascular tissue engineering in regenerative medicine.

Methods:

PCL and CS were dissolved in acetic acid (AAC) and 2,2,2-trifluroethanol (TFE) using different concentrations. Electrospinning was performed at a custom made apparatus, at room temperature. Morphology of the fibrous membranes were examined by SEM. Cyclic sinusoidal uniaxial mechanical tests were performed with an electroforce dynamic tensile testing system. Rectangular, 15 × 10 mm strips were cut and tested at 0 – 30% strain, 1 cycle/s, RT, dry conditions. The applied force and the local principal strain were monitored and stress/strain data was computed. Mechanical properties like Young's modulus (the elastic modulus at linear portion of stress/strain curve) was evaluated. For biophysical characterization FTIR spectroscopy and contact-angle studies were performed.

Results:

SEM observations showed a micro fibrous (2 µm) structure in PCL scaffolds and a combined nano/micro- (0.25 – 2 µm) arrangement in PCL/CS blend scaffolds. Young's modulus showed a significant drop from 25 MPa (PCL) to 5 – 6 MPa for AAC and 12 MPa for TFE with increasing CS concentration, (0 – 30% total strain). The hydrophillicity of the scaffolds was significantly higher with the addition of CS.

Discussion:

From preliminary results it seems that the concentration of CS plays an important role in structural appearance of electrospun PCL fibers. A combination of small porous nanofibers with a greater porous microfibers arrangement was obtained in polymer blends, suitable for potential cell seeding. Elastic modulus of polymer blends, especially in higher CS concentration, was close to properties measured in soft cardiovascular tissues.

References:

Szentivanyi A. et al. Electrospun cellular microenviroments: Understanding controlled release and scaffold structure. Advanced Drug Delivery Reviews 2011;63:209 – 220.

Dimosthenis Mavrilas et al. Dynamic mechanical characteristics of intact and structurally modified bovine pericardial tissues. Journal of Biomechanics, Volume 2005;38:761 – 768