In vivo liquid biopsy for glioblastoma malignancy by the AFM and LSPR based sensing of exosomal CD44 and CD133 in a mouse model.

Glioblastoma (GBM) is the fatal brain tumor in which secreted lactate enhances the expression of cluster of differentiation 44 (CD44) and the release of exosomes, cell-derived nanovesicles (30-200 nm), and therefore promotes tumor malignant progression. This study found that lactate-driven upregulated CD44 in malignant Glioblastoma cells (GMs) enhanced the release of CD44-enriched exosomes which increased GMs' migration and endothelial cells' tube formation, and CD44 in the secreted exosomes was sensitively detected by "capture and sensing" Titanium Nitride (TiN) - Nanoholes (NH) - discs immunocapture (TIC) - atomic force microscopy (AFM) and ultrasensitive TiN-NH-localized surface plasmon resonance (LSPR) biosensors. The limit of detection for exosomal CD44 with TIC-AFM- and TiN-NH-LSPR-biosensors was 5.29 × 10 μg/ml and 3.46 × 10 μg/ml in exosome concentration, respectively. Importantly, this work first found that label-free sensitive TiN-NH-LSPR biosensor could detect and quantify enhanced CD44 and CD133 levels in immunocaptured GMs-derived exosomes in the blood and the cerebrospinal fluid of a mouse model of GBM, supporting its potential application in a minimally invasive molecular diagnostic for GBM progression as liquid biopsy.