A Microchip-Based Gauge for Visual Prediction of Immunotherapy via Distance Readout of Microvesicles

Extracellular vesicles (EVs) have emerged as a promising class of liquid biopsy biomarkers, and programmed death-ligand 1-positive EVs (PD-L1⁺ EVs) have been proven to accurately predict patient response to tumor immunotherapy. Therefore, rapid and sensitive detection of PD-L1⁺ EVs is of great importance for improving treatment efficiency and promoting clinical application. Here, we developed a microchip-based gauge (MicroGauge) for rapid (<30 min) and highly sensitive detection (up to 4.8 × 10⁴ particles/mL) of the purified salivary PD-L1⁺ EVs by reading a visible distance signal, thereby facilitating real-time prediction of immunotherapy efficacy. In this method, the purified salivary PD-L1⁺ EVs are efficiently captured via a one-step immune reaction and then injected into a MicroGauge with a dual pressure-division structure and an inclined capture structure. MicroGauge guides the immune complex to arrange in a monolayer close-packed array, finally forming a visual distance signal and achieving a good sensitivity. Using this MicroGauge, it was found that tumor patients had a higher level of salivary PD-L1⁺ EVs than healthy individuals. Moreover, to evaluate the clinical application potential, an immunotherapy clinical trial was conducted in oral cancer patients. By comparing the changes in the signal length before and after patients received immunotherapy, we found that the signal length of those with a good treatment response continued to shorten during the treatment process, while nonresponders showed a trend of first decreasing and then increasing. This result indicates that MicroGauge can effectively predict the efficacy of immunotherapy by rapidly and highly sensitively detecting the level of PD-L1⁺ EVs.