Exosomes are nanoscale (about 100–200 nm) extracellular vesicles (EVs) that are secreted by cells into the extracellular space and in body liquid circulation. Recent studies on exosomes have shown that they play an important role in various biological processes and can be detected for an early diagnosis of cancer. In this work, we developed a graphene-based biosensor that could isolate exosomes of breast cancer cells from EVs and simultaneously achieve quantitative detection of exosomes. G-OH (hydroxylated graphene), a novel nanomaterial with high conductivity, good biocompatibility, and huge surface area, is quite suitable for the preparation of biosensors. First, the G-OH nanosheets were deposited to form the membrane with the micropores to screen exosomes and microvesicles in EVs. Then, rabbit α-human CD44 antibody was incubated in the membrane to capture MDA-MB-231 (MM-231) exosomes. Finally, modified mouse α-human CD9 antibodies and the third anti-horseradish peroxidase complex were incubated in the membrane, respectively. Under the optimal experimental conditions, this biosensor showed a wide linear range of 25 to 1 × 106 particles·μL–1 and a low detection limit of 9 particles·μL–1 (S/N = 3), spanning 5 orders of magnitude. The quantitative detection of the cancer cell exosomes could be achieved in a mixture of cancer cells and healthy cell exosomes.

An excellent heterojunction structure is vital for the improvement of photocatalytic performance.

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