Disease Detection Without a Hospital: DNA and Proteins Detected With a Single Laser

A technology that identifies disease signals using only a palm-sized chip and a camera has been developed. The metasurface biosensor precisely detects DNA and proteins using a single-wavelength laser and imaging, without an expensive spectrometer.

According to Azure Life Science on the 17th (local time), a research team led by Professor Jun-seok Rho of POSTECH (Pohang University of Science and Technology) developed a metasurface biosensor that accurately detects biomolecules without a spectrometer. The study involved POSTECH researchers Dr. Hong-yoon Kim and Hee-chang Yoon and Se-bin Jeong, as well as teams led by Professor Hyo-min Lee of POSTECH and Professor Yong-sang Ryu of Korea University. The findings were published in the international academic journal Nature Communications.

Biosensors are used for disease diagnosis, infectious disease testing, cancer biomarker detection and genetic analysis. Optical biosensors, in particular, can directly detect biomolecules without fluorescent labels by measuring subtle optical changes that occur when target molecules bind to the sensor surface.

However, conventional methods require high-resolution spectrometers and broadband light sources to read subtle optical changes. Because the equipment is large and expensive, it has been difficult to extend the technology beyond laboratories and hospitals.

Instead of measuring spectra with a spectrometer, the research team took an approach that converts spectral information into spatial information that can be read as an image. The key component is a continuously gradient metasurface whose geometric structure gradually changes in one direction.

As the shape of the nanostructures gradually changes across the chip, each position responds to a different wavelength of light. The principle is similar to piano keys producing different notes depending on their position. When a compact single-wavelength laser illuminates the surface, a dark line appears where the local optical resonance matches the laser wavelength.

When biomolecules bind to the sensor surface, the surrounding refractive index changes slightly, shifting the optical resonance and, consequently, the position of the dark line. The research team accurately measured the molecular binding signal by tracking this spatial shift through imaging.

The sensor achieved a spectral readout resolution of approximately 0.1 nanometers (nm) over an area of approximately 300 micrometers (μm), corresponding to the width of a few human hairs. In protein and DNA experiments, the researchers detected biomolecules at concentrations as low as several hundred picomolar (pM) and confirmed the ability to selectively recognize specific DNA sequences.

Instead of a bulky spectrometer and broadband light source, the technology requires only a compact single-wavelength laser and an image sensor. The research team expects it could be widely used in point-of-care diagnostic applications, including infectious disease testing, cancer biomarker detection, genetic analysis and liquid biopsy.

Professor Jun-seok Rho said, "This study overcame the limitations of conventional spectrometer-based biosensors by combining the high optical sensitivity of metasurfaces with the simplicity of imaging-based readout," adding, "It has strong potential to develop into a compact, low-cost biosensing technology for point-of-care diagnostics."

The study was conducted with support from the Korean ARPA-H Project, funded by the Ministry of Health and Welfare, and a National Research Foundation of Korea program supported by the Ministry of Science and ICT.