(74c) Isolating the Effects of Material Stiffness: Fabrication and Characterization of Univarient Synthetic Cell Culture Substrates

There  are strong indications that the mechanical properties of a substrate plays an important role in many cellular functions. Native human soft tissue has elastic modulus in the range of 0.01 to 1000 kPa. The synthetic materials commonly used as cell culture platforms with varied moduli, including polyacrylamide (PA) and polydimethylsiloxane (PDMS), are limited in applicability due to a restricted range of achievable moduli and/or surface chemistry instabilities. The copolymer network of n-octyl methacrylate (nOM) and diethylene gycol dimethacrylate (DEGDMA) offers attractive material properties that overcome these limitations. In our laboratory, co-polymer networks were fabricated with 3 to 33 wt% DEGDMA. The compressive modulus was 25 ± 2 kPA for the 3% DEGDMA network and increased to 4700 ± 300 kPa at 33 wt% DEGDMA fraction. The networks demonstrated consistent surface wettability over the range of substrate formulations examined as determined by static Sessile drop contact angle. Surface interrogation with x-ray photoelectric spectroscopy (XPS) at the two extremes of formulations, 3 and 33 wt.% DEGDMA, showed similar elemental and chemical bond compositions. The 3% DEGDMA formulation had an elemental composition ratio (carbon to oxygen) of 4.7. The higher DEGDMA composition of 33 wt% DEGDMA showed a carbon oxygen ratio of 4.6. High resolution carbon XPS indicated similar ratios of ether, ester and aliphatic groups at the two extremes of DEGDMA compositions. Quantification of protein adsorption showed no statistical differences between formulations after incubation in a solution of the model protein bovine serum albumin (BSA). Atomic force microscopy was used to map as well as quantify the surface roughness for each of the formulations, obtaining a maximum surface roughness of R_rms 17 ± 6 nm. The murine osteoblastic cell line MC-3T3 E1 was used as a model for cell attachment and viability at six and 96 hours, respectfully. Our results indicate nOM/DEGDMA substrates can vary in modulus over three orders of magnitude while maintaining comparable chemical and topographical surface features. These networks are the first that allow for the study of the effects of material mechanics without the interference of other material properties.