Tissue Chips ? microfluidic devices containing human cells in 3D architectures that attempt to recapitulate the physiology and pathophysiology of human tissues and organs ? contain advanced designs that critically require 3D/modular fabrication, the incorporation of multiple materials and functionalities, and fluidic automation. The vast majority of Tissue Chips are still prototyped in poly(dimethylsiloxane) (PDMS). However, difficult barriers remain for PDMS as a Tissue Chip material. The surface of PDMS is porous and hydrophobic, so both absorption into PDMS and adsorption onto PDMS can potentially alter experimental outcomes by changing the target concentrations and by partitioning molecules in undesired regions of a microfluidic device. 3D-Printing holds an obvious potential for Tissue Chips. Stereolithography (SL), in particular, has been an excellent choice for modulating shapes in 3D at high resolution but modulating material composition is still a challenge. There is a critical need for more advanced, high-resolution and multi-material SL-printing approaches to building future Tissue Chips that can integrate the structural components of a device (channels and valves) with biofabrication (cells and scaffolds). Yet there is no off-the-shelf solution to SL-print multi-material microfluidic devices of wide applicability. This application proposes the synthesis and SL-printing of cyclo-octyne methacrylate (COMA) resin, which will enable the immobilization of any biomolecule-azide of choice onto the COMA-printed surfaces. COMA for derivatizing printed parts via straightforward copper-free (biocompatible) click chemistry, in this case by conjugation to an azide group which spontaneously and specifically reacts with the COMA group in aqueous solutions. Using biotin-azide (commercially available) and an avidin linkage, we will be able to immobilize any biotinylated biomolecule of choice onto the COMA-printed surfaces. We will also use a baseline acrylate resin composed of poly(ethylene glycol) diacrylate (MW~258) (PEG-DA-258), which has successfully been used in microfluidics by several labs, and will experiment with blending PEG-DA-258 with other diacrylates and/or monoacrylates to obtain resins with differing properties, such as higher flexibility. To print devices that are made partially with PEG-DA-258 resin (or blends) and partially with COMA resin (or blends), we will utilize a strategy for co-printing multiple acrylate resins recently utilized by the Folch lab that consists of pausing the print and exchanging the resins in the vat. This scheme will have wide applicability to 3D-print microfluidic devices with multiple regions bearing molecular functionalities (e.g. biomolecular detection, cell capture) and/or elements with distinct sensing/actuating properties (e.g. microvalves, force sensors, etc.). Examples include 3D-printed multiplexed immunosensors based on COMA-derivatized regions, cell trapping devices for drug screening, and organoid-on-a-chip automated platforms, among others.
Progress in Tissue Chips is now hindered by limitations in materials and 3D design/fabrication. We propose to develop stereolithography resins made as blends of acrylates and cyclo-octyne methacrylate (COMA) utilizing copper-free (biocompatible) click chemistry. This blending strategy offers a flexible and convenient strategy for the functionalization of sub-domains of microfluidic devices with multiple, arbitrary biomolecular motifs and with some interesting physicochemical properties.
