“Nano-electronic barcoding” opens path to wearable biosensor monitors

A method for identifying molecules that are markers for diseases could lead to miniaturised wearable health monitoring devices

Artist’ rendition of barcoded beads being scanned. Image: Ella Maru studios

A novel approach to lab-on-a-chip diagnostics could lead to health monitoring devices small enough to be worn like a smartwatch, according to researchers at Rutgers University in New Jersey. The technique, a form of bioassay (which works by attaching traceable substances to molecules known as biomarkers, tell-tale proteins and other molecules that indicate the presence of disease), could be used to continuously monitor blood or sweat.

In a paper published in the Royal Society of Chemistry journal Lab on a Chip, the Rutgers team, led by electrical and computer engineer Mehdi Javanmard, describes how microparticles, engineered to attach to biomarkers such as prostate-specific antigen (PSA), which often indicates the presence of prostate cancer, can be “barcoded” so that they can be identified by compact electronic equipment. Currently, biomarkers are detected using bulky optical detectors that are too large to be added to wearable or portable devices, Javanmard said.

The technique works by forming a tunable micro-capacitor on the surface of a tiny bead of polystyrene. These beads are coated with metal over half of their surfaces with a thin layer of oxide on top of that; varying the thickness and electrical properties of the oxide layer and the surface area of the bead tunes the capacitance of the bead and allows it to be sorted using electric fields in an electronic device.

Using these beads as part of a bioassay could allow several biomarkers to be detected in a single sample. This is important because diseases often have complex mechanisms and more than one biomarker needs to be detected for a certain diagnosis. “One biomarker is often insufficient to pinpoint a specific disease because of the heterogeneous nature of various types of diseases, such as heart disease, cancer and inflammatory disease,’ Javanmard said. “To get an accurate diagnosis and accurate management of various health conditions, you need to be able to analyse multiple biomarkers at the same time.”

Because detection is fully electronic, the technique allows bioassays to be analysed in a very much miniaturised device than was previously possible, the team claims. “Our technology enables true labs on chips. We’re talking about platforms the size of a USB flash drive or something that can be integrated onto an Apple Watch, for example, or a Fitbit,” Javanmard said.

In their paper, the team claims the technology is currently 95 per cent accurate at identifying biomarkers, and they are currently fine tuning it to increase the accuracy to 100 per cent. Further research also aims to expand the technique to identify microorganisms, including bacteria and viruses.

“Imagine a small tool that could analyse a swab sample of what’s on the doorknob of a bathroom or front door and detect influenza or a wide array of other virus particles,” said Javanmard. “Imagine ordering a salad at a restaurant and testing it for E. coli or Salmonella bacteria.”

Such a device could be commercially available within two years, he claimed, with monitoring and diagnostic tools available within five years.