Biofabrication of a vascular capillary by ultra-short laser pulses

Over the last ten years, the need for organ donors for transplants became critical due to the increased incidence of organ failure [1]. Today, the development of tissue engineering (TE) appears as the best opportunity to overcome this shortage. TE is an interdisciplinary emerging field that aims to restore and maintain human tissue functions by applying engineering and live science principles [2]. However, one of its greatest challenges is the vascularization of tissue for the transport of oxygen and nutrients to prevent cell death. Here an innovative method is proposed to answer vascularization issues and the difficulty to create blood microcapillaries constructs, with a special interest to renal microcapillaries, which allow blood filtration. A cell-bilayer covering a tubular collagen I matrix with a diameter of about 150μm was developed and treated by ultra-short pulse (USP) laser processing in order to selectively remove the collagen core to create a capillary. The precise laser treatment allows indeed for the creation of voids in the fibre-shaped construct which results in the final formation of the capillary. Firstly, experiments were carried on a 2D model of gelatine hydrogel. The hydrogel-laser interaction was parametrically investigated in order to define a window of laser process parameters allowing the creation of voids within the hydrogel. The best window of laser process parameters was then applied to the 3D cell bilayer microfibres. Confocal microscopy examination demonstrated the presence of a lumen through the collagen I matrix without extended damage to surrounding cells. Live/Dead assays were also carried to assess cell viability.