Researchers at Nagoya University in Japan have developed a nanowire assay that can be used to capture and detect specific extracellular vesicles in a urine sample that indicate the presence of a brain tumor. These extracellular vesicles are naturally excreted in the urine but techniques to capture and analyze them have been complex, requiring different pieces of equipment, until now. This all-in-one assay uses a simple well plate that has been coated with zinc oxide nanowires that extracellular vesicles are attracted to because of their surface electrical charge. Then, the researchers can detect tumor-specific extracellular vesicles in each well using fluorescently-labeled antibodies. The technique could allow for earlier, non-invasive detection of brain tumors, helping to improve treatment outcomes.
Brain tumors are frequently diagnosed when neurological symptoms have already begun, and the tumor is at an advanced stage. This complicates and ultimately hampers treatment, leading to a survival rate that has barely changed in a couple of decades. Developing new ways to screen patients for such tumors and therefore identify them at a much earlier stage could be very beneficial. Ideally such an approach would be able to highlight the presence of a brain tumor without recourse to invasive biopsies or even a blood draw. These factors have inspired these researchers to develop a urine test for brain tumors.
“Liquid biopsy can be performed using many body fluids, but blood tests are invasive,” said Takao Yasui, a researcher involved in the study. “Urine tests are an effective, simple, and non-invasive method because the urine contains many informative biomolecules that can be traced back to identify the disease.”
This latest technology is based on the concept of extracellular vesicles that are shed by brain tumors into the blood stream, and which ultimately are excreted in the urine. Such vesicles can provide a variety of tumor hallmarks, from RNA and DNA to protein markers. However, they are typically present in urine in very small quantities, and so far researchers looking to isolate and analyze them have had to use cumbersome laboratory techniques and expensive equipment that is poorly suited for a quick one-well assay.
Instead, these researchers took a simple well plate and coated the bottom of each well with zinc oxide nanowires. When a urine sample is added to the wells, the extracellular vesicles stick to the nanowires because of their surface charge, and then stay in place for a simple immunoassay that allows the researchers to label those vesicles that derived from a brain tumor with fluorescent antibodies.
“Currently, EV isolation and detection methods require more than two instruments and an assay to isolate and then detect EVs,” said Yasui. “The all-in-one nanowire assay can isolate and detect EVs using one simple procedure. In the future, users can run samples through our assay and change the detection part, by selectively modifying it to detect specific membrane proteins or miRNAs inside EVs to detect other types of cancer. Using this platform, we expect to advance the analysis of the expression levels of specific membrane proteins in patients’ urinary EVs, which will enable the early detection of different types of cancer.”
Study in ACS Nano: All-in-one nanowire assay system for capture and analysis of extracellular vesicles from an ex vivo brain tumor model
Via: Nagoya University