Johns Hopkins blood test detects earliest signs of heart attack

22 Oct 2024

Modified metasurface for Raman spectroscopy speeds up diagnosis, points to new medical uses.

A project at Johns Hopkins University (JHU) has developed a fast and accurate diagnostic tool for physicians and first responders dealing with patients experiencing heart attacks.

At present, confirmation of heart attack involves electrocardiograms to measure the organ's electrical activity, which takes valuable time, and blood tests to detect the biomarker hallmarks of an attack, involving lab work measured in hours.

The new JHU blood test offers a diagnosis in minutes, and could be adapted as a tool for both clinicians and people at home.

"Heart attacks require immediate medical intervention in order to improve patient outcomes," said Peng Zheng from JHU.

"But while early diagnosis is critical, it can also be very challenging - and near impossible outside of a clinical setting. We were able to invent a new technology that can quickly and accurately establish if someone is having a heart attack."

Published in Advanced Science, the breakthrough is based on surface-enhanced Raman spectroscopy (SERS), in which the molecule-specific but inherently weak Raman fingerprint signals from a sample are amplified by attaching the molecules to a patterned nanostructured surface.

Although SERS has been applied to a number of photonics applications, including atmospheric monitoring and screening of Covid-19 patients, the technique has made limited progress into clinics according to the JHU team.

"Despite its great promise, the translation of SERS into a quantitative analysis technique in clinical settings is hindered by two major challenges," noted JHU in its published paper.

Enormous commercial potential for rapid blood testing

One of the hurdles is that most SERS methods focus on amplifying the electric field component of the electromagnetic Raman signal, rather than its equally valuable magnetic field component. The other is the inherent complexity of the interaction between molecule and substrate, leading to only a fraction of Raman molecules contributing to the detected signals even when surface-enhanced.

JHU tackled both of these hurdles by designing a new SERS substrate to enhance both the electric and magnetic signals during Raman spectroscopy, making heart attack biomarkers visible in seconds even in ultra-low concentrations.

This surface has a hexagonally periodic pattern of meta-atoms, each built from layers of gold and silica, and each having sharp vertices and edges. Plasmonic coupling at the interfaces between metal and dielectric dramatically alters the surface's ability to amplify signals in SERS, according to the project.

In trials, the new metasurface was first used to separately detect three specific cardiac biomarkers in blood serum. Then a 3D-printing operation integrated the functionalized metasurface into a biosensing platform for multiplexed detection of the same three biomarkers in sample mixtures.

The new multiplexed stand-alone SERS blood test produced results in five to seven minutes, and is also more accurate and more affordable than current methods. The same tool could be adapted to detect cancer and infectious diseases, said the project.

"We're talking about speed, we're talking about accuracy, and we're talking of the ability to perform measurements outside of a hospital," commented Ishan Barman from JHU. "There is enormous commercial potential. There's nothing that limits this platform technology."