Cell Printing in Complex Hydrogel Scaffolds

Abstract

Advancements in the microfabrication of soft materials have enabled the creation of increasingly sophisticated functional synthetic tissue structures for a myriad of tissue engineering applications. A challenge facing the field is mimicking the complex microarchitecture necessary to recapitulate proper morphology and function of many endogenous tissue constructs. This paper describes the creation of PEGDA hydrogel microenvironments (microgels) that maintain a high level of viability at single cell patterning scales and can be integrated into composite scaffolds with tunable modulus. PEGDA was stereolithographically patterned using a digital micromirror device to print single cell microgels at progressively decreasing length scales. The effect of feature size on cell viability was assessed and inert gas purging was introduced to preserve viability. A composite PEGDA scaffold created by this technique was mechanically tested and found to enable dynamic adjustability of the modulus. Together this approach advances the ability to microfabricate tissues that better mimic native constructs on cellular and subcellular length scales.

Fig. 1.

A) Plot of percent cell viability and percent increase in reactive oxygen species (ROS) after microgel fabrication vs. the channel height in which the microgel feature was fabricated. B) Brightfield image of cells fabricated in 250 μm diameter microgels within a 55 μm deep channel. C) Color combined image of LIVE/DEAD stain for B) showing full viability after microgel fabrication.

Fig. 2.

A) Plot of percent cell viability and percent increase in reactive oxygen species (ROS) after microgel fabrication vs. microgel width. B-E) Brightfield images of cells fabricated in microgels of 100 μm, 60 μm, 45 μm, and 30 μm, respectively.

Fig. 3.

A) Plot of percent cell viability after encapsulation in a 30 μm diameter microgel under ambient atmospheric conditions and under nitrogen purge (+ N2). B) Plot of percent cell viability after microgel encapsulation in a 25 μm deep channel under ambient atmospheric conditions and under nitrogen purge (+N2). C) Brightfield image of cells fabricated in 30 μm diameter microgels within a 100 μm deep nitrogen purged channel. D) Color combined image of LIVE/DEAD stain for B) showing full viability after microgel fabrication with nitrogen purge.

Fig. 4.

Stress vs. strain plotted for composite scaffolds with microgel features exposed for 15 milliseconds, 30 milliseconds, and solid hydrogel control.