Uncured PDMS inhibits myosin in vitro motility in a microfluidic flow cell

Abstract

The myosin motor powers cardiac contraction and is frequently implicated in hereditary heart disease by its mutation. Principal motor function characteristics include myosin unitary step size, duty cycle, and force-velocity relationship for translating actin under load. These characteristics are sometimes measured in vitro with a motility assay detecting fluorescent labeled actin filament gliding velocity over a planar array of surface immobilized myosin. Assay miniaturization in a polydimethylsiloxane/glass (PDMS/glass) hybrid microfluidic flow channel is an essential component to a small sample volume assay applicable to costly protein samples however the PDMS substrate dramatically inhibits myosin motility. Myosin in vitro motility in a PDMS/glass hybrid microfluidic flow cell was tested under a variety of conditions to identify and mitigate the effect of PDMS on myosin. Substantial contamination by unpolymerixed species in the PDMS flow cells is shown to be the cause of myosin motility inhibition. Normal myosin motility recovers by either extended cell aging (~20 days) to allow more complete polymerization or by direct chemical extraction of the unpolymerized species from the polymer substrate. PDMS flow cell aging is the low cost alternative compatible with the other PDMS and glass modifications needed for in vitro myosin motility assaying.

Polylactic is a Sustainable, Low Absorption, Low Autofluorescence Alternative to Other Plastics for Microfluidic and Organ-on-Chip Applications

“…Although PDMS is biocompatible, transparent, gas permeable, flexible, and relatively easy to manufacture at small scale, some issues have been encountered by consumers while using PDMS devices for certain applications. These problems include channel deformation, high evaporation, leaching of uncured oligomers, absorption of hydrophobic compounds, and unstable surface treatment which can lead to inconsistent and unpredictable results with respect to some biological outcomes . While some of these issues have been overcome (e.g., via Soxhlet extraction in ethanol, or other organic solvent, to remove un-cross-linked oligomers), PDMS molding still remains a difficult process to fully automate and significantly slows down the translation from the research to the mass market production.…”

Organ-on-chip applications in drug discovery: an end user perspective

“…Of importance for pharmaceutical applications, the hydrophobic surface also encourages the non-specific, unpredictable binding of small molecules to its surface, which reduces free drug concentration [64,65]. Another challenge with the use of PDMS in microfluidic systems is the leaching of remaining uncured oligomers into the culture medium and cells which can interfere with biological processes and lead to spurious experimental outcomes [66][67][68] The field has been looking into alternative materials that are non-absorbent, gas permeable, biocompatible, optically clear and amenable to mass manufacturing. Thermoplastics, hydrogels, glass and biocompatible materials with a long history of being used for tissue engineering, such as polylactic acid (PLA), as well as the combinations of these materials, are investigated to support the next generation of microfluidic chip manufacturing [69][70][71].…”