Acoustofluidic platform for in-channel immunoassays

We demonstrate proof of concept for a point-of-care diagnostic that is used for the detection of chloride channel accessory 1 (CLCA1), a key regulator of mucus production. The prototypical device utilizes ultrasound-confined polystyrene (PS) microspheres held in a longitudinal standing bulk acoustic wave (LSBAW) as reaction substrates. Pressure field amplification between two included pillar arrays enables immobilization of these antigen-coated beads in a predetermined low-pressure region perpendicular to the direction of flow. Bronchoalveolar lavage (BAL) samples from IL-13 stimulated pigs were incubated overnight in a solution of untreated PS beads prior to channel introduction. A PZT- 8 piezoceramic transducer was used to actuate the channel (f_1,E = 575 kHz) to focus and confine the beads in a linear zero-pressure node. A solution of two proprietary anti-CLCA1 monoclonal antibodies (mAbs) modified with sulfocyanine3 (Cy3) NHS ester were flowed (7 μL/min, 15 min) into the channel and incubated for 1.5 hours. A solution of phosphate-buffered saline was then used to remove excess antibodies prior to channel/bead cluster imaging. The bead solution was collected, under no acoustic actuation, at the outlet for analysis by flow cytometry. Increased fluorescence over control samples (p<0.0001) demonstrated that the LSBAW platform can serve as a functional immunoassay to allow for serial, contactless reagent washes and fluorescent probe introduction.