Continuous Single-Phase Flow-Assisted Isolation for Parallel Observation of Reactions Between Deterministically Paired Particles

We propose a microarray-based microfluidic platform that uses a continuous single-phase flow-assisted isolation (CSFI) method to conduct multiplex analysis of reactions between co-located heteroparticles in a single-phase aqueous solution. The CSFI method is performed by consistently and continuously introducing an aqueous-phase fluid through microchannels. Hence, the unit elements of a particle pair array can be isolated without interelement cross-contamination, as they exist in independent air curtains. The formation of particle pairs with different sizes is accomplished by sequentially loading microparticles without changing the flow directions, which achieves a particle pairing efficiency up to 91%. The immunoreaction between the receptor-coated beads and the fluorescence-labeled analytes encapsulated within the hydrogels was used as a proof of concept. The analytes were diffused from the hydrogels and only treated the paired receptor-coated beads under continuous single-phase flow. Parallel monitoring of reactions on the receptor-coated beads was conducted using the CSFI method. By characterizing the operation flow rate of the CSFI method, we demonstrated the prevention of interelement cross-contamination and the enhancement of binding efficiency on receptor-coated beads.