A microfluidic chamber to study the dynamics of muscle contraction specific molecular interactions

Horia Nicolae Roman, David Juncker, and Anne-Marie Lauzon

In vitro motility and laser trap assays are commonly used for molecular mechanics measurements. However, chemicals cannot be added during measurements because they create flows that alter the molecular mechanics. Thus, we designed a microfluidic device that allows the addition of chemicals without creating bulk flows. Biocompatibility of the components of this device was tested. A micro-channel chamber was created by photolithography with the patterns transferred to polydimethylosiloxane (PDMS). The PDMS chamber was bound to a polycarbonate membrane which itself was bound to a molecular mechanics chamber. The micro-channels assured rapid distribution of the chemicals over the membrane whereas the membrane assured efficient delivery to the mechanics chamber while preventing bulk flow. The biocompatibility of the materials was tested by comparing the velocity (νmax) of propulsion by myosin of fluorescently labeled actin filaments to that of the conventional assay; no difference in νmax was observed. To estimate total chemical delivery time, labeled bovine serum albumin was injected in the channel chamber and TIRF was used to determine the time to reach the assay surface (2.7±0.1 s). Furthermore, the standard distance of a trapped microsphere calculated during buffer diffusion using the microfluidic device (14.9±3.2 nm) was not different from that using the conventional assay (15.6±5.3 nm, p=0.922). Finally, νmax obtained by injecting adenosine triphosphate (ATP) in the micro-channel chamber (2.37±0.48 µm/s) was not different from that obtained when ATP was delivered directly to the mechanics chamber (2.52±0.42 µm/s, p=0.822). This microfluidic prototype validates the design for molecular mechanics measurements.

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