A CRISPR-based rapid test called CrisprZyme could help general practitioners to diagnose heart attacks and distinguish between different types of prostate cancer. They do not even need a lab, as an international team of scientists – including Michael Kaminski – reports in "Nature Nanotechnology".
Thanks to the pandemic, antigen rapid tests are familiar to just about everyone. If a swab contains viral protein fragments, antibodies bind to them on a test strip and a line appears. Yet if characteristic genetic material (RNA or DNA) is to be detected, more sophisticated procedures such as a PCR test are necessary. The genetic material must first be processed and amplified. Such tests take longer and are only possible in a special lab.
So far, this has mostly been the case with CRISPR-based diagnostics, in which Cas enzymes are programmed to detect segments of DNA or RNA. Using a test strip, this technology can detect tiny segments of an RNA sequence (biomarkers) in a urine or blood sample that indicate the presence of a specific disease or infection. But first the RNA usually has to be amplified under controlled conditions using expensive equipment to make the signal strong enough. This makes it impossible to know how much biomarker was in the sample. Yet for doctors who monitor the development of diseases like cancer or heart disease, this information is vital.
As an international research team reports in the journal Nature Nanotechnology, a new method called CrisprZyme now increases the signal for CRISPR-based diagnostics. The team includes scientists from Imperial College London, MIT in Boston, the Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), and Charité – Universitätsmedizin Berlin. In the future, this rapid test could allow doctors to quickly identify biomarkers for acute heart attacks and to distinguish between certain types of prostate cancer. The method is therefore of primary relevance to general practitioners and resource-limited clinics in developing countries.
Even at room temperature
“The test is easy to use and even works at room temperature. The result can be seen by the naked eye or using a paper strip,” said Dr. Michael Kaminski, one of the first authors on the paper and the head of an Emmy Noether independent junior research group at Charité and the MDC. “By making clinical diagnostic tests simpler, we will be able to provide clinicians with the right tools to test at the same GP surgery instead of having to reschedule for follow-up analyses and blood tests,” added co-first author Dr. Marta Broto from Imperial College London.
CrisprZyme replaces or augments the amplification process with colorimetric analysis. A color scale indicates how much biomarker is present. This is made possible by nanozymes –tiny synthetic materials that behave like enzymes. They increase the signal of the test, making the colorimetric analysis easier to read. Temperature control and further steps are no longer necessary. The test can also detect non-coding RNA, including microRNA, long non-coding RNA, and circular RNA.
Faster and more user-friendly
“The process can tell us just how much biomarker is present, which can help us not just with diagnosing a disease, but with monitoring its progress over time and in response to treatment,” said senior author Prof. Molly Stevens of Imperial College London.
In its current form, CrisprZyme does not quite remove all the steps, as the sample must be treated with chemicals to extract the desired biomarker before the test. “But we’re working on making the process even faster and more user-friendly,” said Kaminski. The team must also carefully assess how sensitive and how reliable the test is in detecting various biomarkers in patients. Nevertheless, the scientists believe it has great potential. They’re already looking at what other diseases it could be used for.
Reference: Broto M, Kaminski MM, Adrianus C, et al. Nanozyme-catalysed CRISPR assay for preamplification-free detection of non-coding RNAs. Nat Nanotechnol. 2022. doi: 10.1038/s41565-022-01179-0
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