Site specific biotinylated antibody functionalized Ag@AuNIs LSPR biosensor for the ultrasensitive detection of exosomal MCT4, a glioblastoma progression biomarker

Glioblastoma (GBM) is an incurable brain tumor in which hypoxic GBM cells (GMs) increase the production and release of exosomes, which are 30-200 nm vesicles crossing the blood-brain-barrier, enabling exosomal biomarkers to be promising targets for the tracking of GBM malignancy. Here, a localized surface plasmon resonance (LSPR) sensor chip was developed to detect an infinitesimal amount of exosomal biomarkers. Self-assembly silver nanoparticles decorated on gold nano-islands (Ag@AuNIs) sensor chip was used to provide site-specific bioconjunction of biotinylated antibodies for detection of exosomal surface biomarkers. The biotinylated antibody functionalized (BAF) Ag@AuNIs LSPR biosensor sensitively detected cluster of differentiation 63, an exosome marker, and monocarboxylate transporter 4 (MCT4), a GBM progression biomarker, in malignant GMs-derived exosomes in the dynamic range of 3.8 x 10-4 to 50 mu g/ml with limit of detection (LOD) of 0.38 ng/ml and 1.4 x 10-3 to 500 mu g/ml with LOD of 1.4 ng/ml, respectively. Furthermore, it detected the enhanced level of MCT4 in malignant hypoxic GMs-derived exosomes as well as increased MCT4 in the blood serum-derived exosomes of GBM mice in the dynamic range of 4 x 10-4 to 50 mu g/ml with LOD of 0.4 ng/ml. Finally, it could quantify MCT4 in the isolated GMs-derived exosomes from the blood of GBM mice by epidermal growth factor receptor variant III-based immunocapture, suggesting its utility for minimally-invasive monitoring of GBM progression as liquid biopsy. With excellent attributes of high sensitivity and selectivity in label-free sensing for exosomal biomarkers, the BAF Ag@AuNIs LSPR biosensor has great potential for early detection of GBM formation and progression.