Since clinical laboratories are recognizing the importance of implementing sensitive and specific molecular diagnostic tests that require simplified workflows without requiring expensive supporting instrumentation, this article describes a valveless flow cell for disposable use that supports PCR coupled with microarray hybridization in the same chamber.
The flow cell assembly consists simply of double-faced tape, a plastic microarray substrate, an absorbent, and a commercially available hydrophilic thin film. The simple construction lends itself to low-cost and ease of manufacturing, and several features reduce the complexity of the standard microarray workflow. First, there is no requirement for custom instrumentation. Second, the hydrophilic thin film enables uniform filling of a microfluidic chamber. Third, a geometric capillary stop design confines liquid to the microarray chamber during PCR, and thus eliminates the need for a valve or hydrophobic surface treatment. And fourth, imbibition drives the uniform removal of liquid reagents from the array chamber. Three hundred genomic copies of methicillin-resistant Staphylococcus aureus (MRSA) are detected in a flow cell with gel drop microarrays printed on an unmodified plastic substrate. This sensitivity is shown to be comparable to conventional methods (i.e., PCR in a tube, with separate hybridization in a microarray chamber, where amplicon is exposed to the workspace before and after hybridization); however, the flow cell combines these multiple steps into a simple, compact workflow without the need for complex valves or custom instrumentation and is less susceptible to contamination of the workspace than conventional methods because the amplicon is confined to the device. (publisher abstract modified)