Textile reinforcement of tissue-engineered heart valves by tailored fibre placement.

The mechanical properties and long term durability of tissue-engineered heart valves are still in need of improvements before their implantation in the systemic circulation will become widespread. Textile engineering offers a multi-scale toolbox to improve heart valve scaffolds by conferring mechanical strength and anisotropy. The aim of this study was to develop a scaffold for aortic tissue-engineered valves specifically designed to deal with the mechanical stresses they must endure. It is postulated that an optimized load-bearing capability with minimized stress will ensure long-term durability.

To this end we developed valves with a tubular leaflet design consisting of an electrospun construct with tailored placed fibres. The layout of the reinforcing fibres was based on computer simulations of a finite element model to determine the stress distribution and identify fibre volume fraction and orientation. A cylindrical collector was used to produce one layer of electrospun nonwoven on which fibres were placed in a load-oriented arrangement and covered with a second electrospun polymeric layer. Different materials were used for the tubular scaffold (PLGA, PCL, TPU) and multi- or monofilament fibres were applied.

These reinforced electrospun valves were sutured into silicone tubes mimicking the aortic root and tested in a mock circulation loop at physiological aortic hydrodynamic conditions in accordance with ISO 5840. These included flow rates of 2, 4, 5 and 7 L/min and a peak differential pressure of 100 mmHg. The presence of the fibres did not compromise the valve’s functionality and the ISO requirements were fulfilled.

The scaffold’s porosity was further optimized for cellular infiltration.