BIO25: Toward a Biocompatible 3D Printing Resin for Microfluidic Organ Models

Abstract

Background: Microfluidics is a desirable platform to create artificial organ models, such as organs-on-a-chip, to study disease and develop therapeutics in a 3D microenvironment. There is a gap in understanding and reproducing the microenvironment due to a lack of suitable models and means to fabricate these micron-scale architectures. 3D printed microfluidics offer a reliable fabrication approach with geometric control for replicating the tissue microenvironment at a relevant size-scale. However, gas-permeable, biocompatible materials for high-resolution microfluidic 3D printing do not exist. Here, we report a biocompatible, polydimethylsiloxane (PDMS) resin for facile 3D printing of microfluidics for tissue-based devices. Methods: 3D-printed parts were made using the Asiga MAX X UV27 digital light processing (DLP) 3D printer and our custom, high-resolution PDMS resin. Unreacted monomers and leachable components were extracted from 3D-printed well plates by soaking in ethanol for 72h and compared against untreated (no ethanol extraction) 3D-printed plates and standard cell culture plates. Absorbance of extraction media was measured to quantify the removal of leachables. Gas permeability of thin, 3D-printed films was measured for O2 and CO2 by Labthink International, Inc. according to ASTM D1434-82(R09)e1. Biocompatibility of the novel gas-permeable, high-resolution PDMS resin was tested by BioAssay Systems via a cell viability study with HepG2 cells in vitro. Results: Figure 1A shows a diminishing absorbance signal of the extractable compounds in the ethanol solution after each 24h soak of the cured resin. Reduction in the absorbance signal indicates removal of these unwanted constituents as confirmed by the lighter hue of extracted 3D-printed cell culture plate vs unextracted controls (Figure 1B). O2 and CO2 permeability are comparable to Sylgard 184 (Figure 1C). Cell viability studies performed with HepG2 cells (Figure 1D) grown on untreated 3D-printed plates, extracted 3D-printed plates, and control cell culture plates show that removal of unreacted groups and photoabsorbing compounds have a significant effect (p<0.05), improving cell growth and viability relative to the untreated and control groups. Conclusion: We have demonstrated the potential of this PDMS 3D printing resin as a biocompatible, gas-permeable material for cell-based microfluidic devices. Applications range from µALs as respiratory support devices to tissue-engineered, microfluidic organ models to study disease.Figure 1. (A) Absorbance signal of extraction media after soaking the 3D printed part in ethanol. (B) 3D printed well plates, untreated (no ethanol extraction) and extracted in ethanol (72h soak). (C) Gas permeability measurements of 100µm film made from PDMS resin. Sylgard 184 data were taken from literature. (D) Cell viability of HepG2 cells grown on control plates (standard 12-well), untreated 3D printed plates, and extracted 3D printed plates (n=3). Analyses of unpaired multiple t-tests between treatment groups (* indicates p-value<0.05) and 2-way ANOVA with Tukey’s multiple comparison test determined there was a significant interaction (p-value<0.0001) between the effects of treatment (control, untreated, and extracted) and time (24h and 72h) on cell viability (absorbance).