Optical fiber amplifier and thermometer assisted point-of-care biosensor for detection of cancerous exosomes

Abstract

Developing a simple, reliable and sensitive point-of-care testing (POCT) biosensor for cancerous exosomes detection is crucial to early cancer diagnosis and prognosis. Herein, a colorimetric and photothermal POCT biosensor was demonstrated based on rolling circle amplification (RCA) mediated 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS)‑H2O2 system for sensitive detection of cancerous exosomes. In the presence of target exosomes, RCA could be triggered and produced multiple units that hybridized to horseradish peroxidase (HRP) modified DNA probes. Colorless ABTS would be converted by HRP into the oxidized form with strong near-infrared absorbance, enabling colorimetric and photothermal detection of exosomes. Then, colorimetric and photothermal responses were recorded by optical fiber amplifier and forehead thermometer, respectively, enabling hand-held detection. Moreover, EpCAM aptamer was used as biorecognition element for exosomes secreted by MCF-7 breast cancer cells so that the point-of-care biosensor exhibited excellent specificity. Furthermore, the point-of-care biosensor could effectively detect the cancerous exosomes in 30% fetal bovine serum with lots of normal exosomes. Moreover, the biosensor could avoid the influence of the external environment, including surrounding light and temperature. These results suggest that the proposed strategy has great potential as a powerful tool for POCT application of exosomes in future diagnosis.