Dual-target magneto-immunoassay with bifunctional nanohybrids for breast cancer exosome detection

Exosomes, crucial for intercellular communication, hold potential as noninvasive liquid biopsy biomarkers especially in early breast cancer detection benefitted from the distinctive "cancer signature" on their membrane surface. Yet, the present methodologies of exosomes for breast cancer detection have involved the implementation of only a single member from the tetraspanin protein group as a biomarker. Moreso, due to the high concentration of exosomes in complex body fluids, there is a compelling need to measure a small concentration of cancer-derived exosomes with a low background noise signal. In this study, we designed and characterized magnetic core-gold shell nanohybrids (mAuNHs) that function as detection and isolator probes, which were integrated in a simple colorimetric sandwich magneto-immunoassay (mLISA). The magnetic core of mAuNHs facilitates the separation of exosomes from complex samples of biological origin whereby amorphous structures were effectively removed, decreasing background signal. Meanwhile, the coalescence effect of pairing biologically abundance exosomal marker (CD9 antibody) with the cancer specific (CD24 antibody) offers a highly selective and sensitive detection of our target model, MCF7 exosomes. As a result, using our mLISA system, exosomes derived from MCF7 can be selectively recognized from other tested cancer cell lines, BT474 and PC3. Besides, as low as 37 particles/μL of limit of detection (LOD) was achieved using mLISA sensor, exhibiting a good sensitivity as compared to conventional ELISA. Overall, our proposed dual-target biosensor offers a great reduction on background noise from samples, simplicity for users as in exosome's lengthy preparation is reduced as well as good sensitivity.