ALA-induced fluorescence detection with photoresist-based microfluidic cell sorter for bladder cancer diagnosis

• A photoresist-based μFACS for bladder cancer diagnosis was developed.
• Bladder cancer cells are detected using ALA-induced PpIX fluorescence.
• Autofluorescence of photoresist was investigated to improve detection sensitivity.
• Suitability of the developed μFACS is confirmed through clinical test.
• A combination of developed μFACS and PCR analysis is a promising diagnostic approach.

We present a photoresist-based microfluidic fluorescence-activated cell sorter (μFACS) for bladder cancer diagnosis and assess its potential for clinical application. In the developed μFACS system, bladder cancer cells in urine sediment are detected using aminolevulinic acid (ALA)-based fluorescence detection, and then sorted at the Y-junction of the microchannel using an off-chip pinch valve. Once cancer cells are collected, they can be analyzed using polymerase chain reaction (PCR) for detailed gene alteration analysis. Generally, time and cost-effective advantages of negative photoresist material and fabrication technologies have been widely pronounced; however, autofluorescence is a significant drawback when negative photoresist is used as a structural material for μFACS applications. To achieve sensitive fluorescence detection, autofluorescence in the detection area is minimized by thinning the photoresist cover layer of the microchannel and inclining the optical angle of the detection system. Through system calibrations and clinical tests using urine sediments, our experimental results demonstrate a combination of ALA-based photodynamic diagnostic tests using μFACS systems and subsequent PCR analysis is a promising diagnostic approach for bladder cancer.