Researchers have created a new light-based sensor that can detect vanishingly small amounts of cancer-related molecules in the blood. This highly sensitive technology is designed to pick up early warning signs of disease long before symptoms appear, potentially allowing doctors to identify cancer and other conditions using a straightforward blood test rather than invasive procedures or complex imaging.
Many diseases, including cancer, leave behind molecular traces known as biomarkers. These can include proteins, fragments of DNA, or other biological molecules that signal the presence or progression of illness. The difficulty is that, at very early stages of disease, these biomarkers are present in extremely low concentrations, often too low for conventional tests to detect reliably. Overcoming this limitation is one of the biggest challenges in early diagnosis, when treatment is most effective.
The new sensor addresses this problem by combining several advanced technologies into a single system. It uses carefully designed DNA nanostructures, tiny semiconductor particles called quantum dots, and a CRISPR-based detection mechanism. Together, these components work with a light-based method known as second harmonic generation, or SHG. This optical technique is especially powerful because it produces very little background noise, making it easier to spot weak signals from just a few biomarker molecules.
At the heart of the sensor is a thin layer of a two-dimensional material called molybdenum disulfide. When light shines on its surface, SHG causes light at a new wavelength to be produced. To amplify this signal, the researchers attach quantum dots to the surface using DNA tetrahedrons—small, pyramid-shaped structures made entirely from DNA. These DNA structures act like nanoscale scaffolding, positioning the quantum dots at precise distances from the surface so they enhance the light signal as much as possible.
CRISPR technology provides the sensor’s ability to recognise specific biomarkers. When the system encounters a target molecule, a CRISPR-associated protein cuts the DNA strands holding the quantum dots in place. This causes the quantum dots to detach, leading to a noticeable drop in the SHG signal. Because this change is easy to measure and does not require amplifying the biomarker itself, the sensor can detect extremely low concentrations quickly and efficiently. The design treats DNA not just as genetic material, but as a programmable construction tool that allows precise control at the nanometre scale.
To test the system, the researchers focused on miR-21, a microRNA commonly linked to lung cancer. They first demonstrated that the sensor could detect this biomarker in a simple laboratory solution. More importantly, they then showed it could identify the same molecule in human blood serum from lung cancer patients, closely mimicking real clinical conditions. The sensor proved highly specific, responding only to the intended target and ignoring similar molecules that could otherwise cause false results.
Looking ahead, the team aims to make the technology smaller and more practical for everyday use. By miniaturising the optical components, they hope to develop a portable device that could be used in hospitals, clinics, or even remote and low-resource settings. In the long term, this approach could enable routine blood screening for cancer before tumours are visible on scans, support personalised treatment by tracking biomarker levels frequently, and reduce both healthcare costs and the burden on patients.
More information: Bowen Du et al, Sub-attomolar-level biosensing of cancer biomarkers using SHG modulation in DNA-programmable quantum dots/MoS2disordered metasurfaces, Optica. DOI: 10.1364/OPTICA.577416
