Exosomes are cell-secreted nanovesicles (40-200 nm) that represent a rich source of novel biomarkers in the diagnosis and prognosis of certain diseases. Despite the increasingly recognized relevance of these vesicles as biomarkers, their detection has been limited due in part to current technical challenges in the rapid isolation and analysis of exosomes. The complexity of the development of analytical platforms relies on the heterogeneous composition of the exosome membrane. One of the most attractive tests is the inmunochromatographic strips, which allow rapid detection by unskilled operators.
Researchers at the Universidad de Oviedo have successfully developed a novel lateral flow immunoassay (LFIA) for the detection of exosomes based on the use of tetraspanins as targets. They have applied this platform for the detection of exosomes purified from different sources: cell culture supernatants, human plasma and urine. As proof of concept, they explored the analytical potential of this LFIA platform to accurately quantify exosomes purified from a human metastatic melanoma cell line. The one-step assay can be completed in 15 min, with a limit of detection of 8.54×10(5) exosomes/µL when a blend of anti-CD9 and anti-CD81 were selected as capture antibodies and anti-CD63 labelled with gold nanoparticles as detection antibody. Based on their results, this platform could be well suited to be used as a rapid exosome quantification tool, with promising diagnostic applications, bearing in mind that the detection of exosomes from different sources may require adaptation of the analytical settings to their specific composition.
Schematic view of the experimental procedure for exosomes detection
(a) Schematic representation of the ELISA set up for exosomes detection. Here, each reagent is added in sequential steps. (b) Schematic representation of the lateral flow immunoassay dipstick. (1) Specific antibodies against tetraspanins (test, T) and anti-mouse immunoglobulin antibodies (control, C) are immobilized on the membrane. (2) Exosomes, if present in the sample, are detected by the detection probes (AuNP-conjugated antibodies). (3) As the complexes flow, they are captured onto the membrane by the immobilized antibodies.