Rapid generation of three-dimensional microchannels for vascularization using a subtractive printing technique

The development of tissue-engineered products has been limited by lack of a perfused microvasculature that delivers nutrients and maintains cell viability. Current strategies to promote vascularization such as additive three-dimensional printing techniques have limitations. This study validates the use of an ultra-fast laser subtractive printing technique to generate capillary-sized channels in hydrogels prepopulated with cells by demonstrating cell viability relative to the photodisrupted channels in the gel. The system can move the focal spot laterally in the gel at a rate of 2500 mm/s by using a galvanometric scanner to raster the in plane focal spot. A Galilean telescope allows z-axis movement. Blended hydrogels of polyethylene glycol and collagen with a range of optical clarities, mechanical properties and swelling behavior were tested to demonstrate that the subtractive printing process for writing vascular channels is compatible with all of the blended hydrogels tested. Channel width and patterns were controlled by adjusting the laser energy and focal spot positioning, respectively. After treatment, high cell viability was observed at distances greater than or equal to 18 μm from the fabricated channels. Overall, this study demonstrates a flexible technique that has the potential to rapidly generate channels in tissue-engineered constructs.