Biocompatible, Flexible, and Oxygen-Permeable Silicone-Hydrogel Material for Stereolithographic Printing of Microfluidic Lab-On-A-Chip and Cell-Culture Devices

We present a photocurable, biocompatible, and flexible silicone-hydrogel hybrid material for stereolithographic (SLA) printing of biomedical devices. The silicone-hydrogel polymer is similar to mixtures used for contact lenses. It is flexible and stretchable with a Young's modulus of 78 MPa and a maximum elongation at break of 51%, shows a low degree of swelling (<4% v/v) in water, and can be bonded easily to flat glass substrates via a surface-modification method. The in vitro cytotoxicity of the material is assessed with a WST-8 cell viability assay using five different cell lines: HT1080, L929, and Hs27 fibroblasts, cardiomyocyte-like HL-1 cells, and neuronal-phenotype PC-12 cells. On this account, the silicone-hydrogel polymer is compared to several other common SLA printing materials used for cell-culture applications and polydimethylsiloxane (PDMS). A simple extraction step in water is sufficient for reaching biocompatibility of the material with respect to the tested cell types. The oxygen permeability of the silicone-hydrogel material is investigated and compared to that of PDMS, Medicalprint clear- A commercial resin for medical products, and a short-chain hydrogel-based resin. As a proof of concept, we demonstrate a 3D-printed microfluidic device with integrated valves and mixers. Furthermore, we show a printed culture chamber for analyzing signal propagation in HL-1 cardiomyocyte cell networks. Ca2+ imaging is used to observe the signal propagation through the cardiac cell layers grown in the microchannels. The cells are shown to maintain normal electrophysiological activity within the printed chambers. Overall, the biocompatible silicone-hydrogel material will be an advancement for SLA printing in cell-culture and microfluidic lab-on-a-chip applications.