Argonaute protein and microRNA
Argonaute protein. Molecular model of human argonaute-2 protein complexed with microRNA (micro ribonucleic acid). This protein is part of the RNA-induced silencing complex (RISC). RISC plays a role in gene regulation and defence against viral infection.

Oncologists may soon be able to detect and quantify cancer biomarkers while their patients are still in the clinic using a test developed by researchers at the University of Illinois Urbana-Champaign.

The test uses nanoparticles to capture tumor-specific microRNAs (miRNAs) in human serum. These small, single-stranded, noncoding RNAs play an important role in gene expression and regulation and have been linked to tumor progression and metastases.

However, detecting miRNAs can be a challenge because of their low concentrations in body fluids, explained Congnyu Che, bioengineering graduate student in the Department of Bioengineering and Nick Holonyak Micro and Nanotechnology Laboratory at the University of Illinois at Urbana-Champaign and first author of the ACS Nano paper that describes the test.

She added that “some conventionally used methods like PCR or microarrays can either be very expensive or can take up to several hours before you find out the result.”

To address this, Che and colleagues adapted a technique called Photonic Resonator Absorption Microscopy (PRAM) that had already been developed by her lab to capture miRNA biomarkers.

PRAM uses gold nanoparticles that are prepared with a molecule which allows them to capture and bind to miRNA in a liquid sample. The bound particles then diffuse around in the sample and eventually float to the bottom of the test well where they are detected with a photonic crystal biosensor after around 1 to 2 hours.

To accelerate the process, Che added an iron element to the nanoparticles which once bound to the miRNA are drawn to the bottom of the test well by a magnet placed underneath the biosensor. This reduces the detection time to just 1 minute whilst maintaining the sensitivity of the test, meaning that it could be a candidate for use in a point-of-care setting.

“Right now we’re working on [developing] a portable device that can be used in a clinic or hospital and give some early cancer diagnosis, [providing a] result within several minutes,” said Che.

The researchers evaluated the feasibility of the method by spiking human serum samples with different concentrations of miR-375, an miRNA biomarker for prostate cancer, and testing the samples without any purification steps. After 1 minute they were able to detect miR-375 at a concentration of 61.9 aM, which is three orders of magnitude lower than the concentration expected in human serum, highlighting the sensitivity of the test.

Study lead Professor Brian Cunningham, who holds positions at the University of Illinois at Urbana-Champaign, the Cancer Center at Illinois, and the Woesse Institute for Genomic Biology, told Inside Precision Medicine that the magnetized PRAM assay could not only be used for cancer diagnosis, but also perhaps more importantly for monitoring therapy responses and the emergence of mutations or disease recurrence.

He added that the group, which is funded by the National Institutes of Health, has several collaborations underway looking including work on prostate cancer with the Huntsman Cancer Institute, a collaboration with the Mayo Clinic focussing on lung cancer, and work with Mount Sinai Hospital whose speciality is liver cancer.

Indeed, this latter collaboration has led to a recent publication in the journal Talanta, which showed that the PRAM assay is able to detect liver cancer-associated small RNA in plasma samples from people with hepatocellular carcinoma.

And the benefits of the test may extend beyond oncology. “We’re discovering there’s so many microRNAs involved in your health and nutrition, with cardiovascular disease, with neurological disease. It’s a very interesting class molecule [and] people are finding more and more ways that they are important indicators for biology,” Cunningham said.

He also noted that he expects the test to be cost-effective. Its main components, a red LED, a webcam image sensor, and the photonic crystals are “very inexpensive,” with a component cost of approximately $5000 for the portable PRAM device plus $1-2 per test for each biosensor.

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