Amphiphilic silicones to reduce the absorption of small hydrophobic molecules

Silicones (i.e. crosslinked poly(dimethylsiloxane), PDMS) are commonly used material for microfluidic device fabrication. Nonetheless, due to the uncontrollable absorption of small hydrophobic molecules (< 1 kDa) into the bulk, its applicability to cell-based drug assays and sensing applications has been limited. Here, we demonstrate the use of substrates made of silicones bulk modified with a poly(ethylene oxide) silane amphiphile (PEO-SA) to reduce hydrophobic small molecule sequestration for cell-based assays. Modified silicone substrates were generated with concentrations of 2 wt.%, 9 wt.% and, 14 wt.% PEO-SA. Incorporation of PEO-SA into the silicone bulk was assessed by FTIR analysis in addition to water contact angle analysis to evaluate surface hydrophobicity. Cell toxicity, absorption of small hydrophobic drugs, and cell response to hydrophobic molecules were also evaluated. Results showed that the incorporation of the PEO-SA into the silicone led to a reduction in water contact angle from 114 degrees to as low as 16 degrees that was stable for at least three months. The modified silicones showed viability values above 85% for NIH-3T3, MCF7, MDA-MB-468, and MDA-MB-231 cell lines. A drug response assay using tamoxifen and the MCF7 cell line showed full recovery of cell toxicity response when exposed to PDMS modified with 9 wt.% or 14 wt.% PEO-SA compared to tissue culture plastic. Therefore, our study supports the use of PEO-SA at concentrations of 9 wt.% or higher for enhanced surface wettability and reduced absorption of small hydrophobic molecules in PDMS-based platforms. Statement of significance Silicones, such as poly(dimethylsiloxane) known as PDMS, are commonly used material for microfluidic device fabrication, yet the uncontrollable absorption of small hydrophobic molecules ( < 1 kDa) into the bulk of silicones, limit their applicability into drug assays and hydrophobic sensing applications in aqueous solutions. The present study examined the hydrophilic properties and cell compatibility of PDMS combined with poly(ethylene oxide) silane amphiphile (PEO-SA). The data shown supports the use of PEO-SA at concentrations of 9 wt.% or higher for enhanced and stable surface wettability and reduced absorption of small hydrophobic molecules in silicons for cell-based and hydrophobic sampling applications. (c) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

Silicones, such as PDMS, are commonly used in microfluidic device fabrication, but the uncontrollable absorption of small hydrophobic molecules limits their applicability in cell-based drug assays and sensing applications. This study demonstrates that incorporating PEO-SA into silicone substrates can reduce small hydrophobic molecule sequestration and improve cell compatibility in assays.