Allosteric ProbeRecognition-Induced Exponential AmplificationReaction for Label-Free Photosensitization Colorimetric Detectionof Small Extracellular Vesicles

The expression levels of small extracellular vesicles (sEVs) are acknowledged as highly promising diagnostic biomarkers for a variety of diseases, including chronic obstructive pulmonary disease and lung cancer. However, a convenient and sensitive system for on-site rapid detection of sEVs is still highly desired. We have created a portable and highly efficient photosensitization colorimetric platform for label-free, sensitive, and colorimetric sEV detection by using an allosteric probe to specifically identify the CD63 protein on the surface of sEVs, which triggers numerous signal cycles to generate color changes. Visual detection of sEVs could be accomplished in 60 min using this detection platform. It was noted that this detection platform was capable of effectively detecting the target at a concentration as low as 1.21 particles/μL, and the reaction was completed in a single step. The proposed assay could be potentially engineered to serve as a universal bioassay platform for the detection of other molecules when used in conjunction with other aptamers for probe design. The principle of this strategy is highly versatile and sensitive, making it accessible for a variety of biosensor developments and applications.