Heart failure is one of the leading causes of death worldwide and is particularly deadly for people who do not have access to medical facilities. A team of researchers therefore wants to bring heart failure screening from the laboratory to the home setting. Their point-of-care prototype electrochemical biosensor, which resembles a see-through lateral flow test for COVID-19, can measure the levels of two heart failure biomarkers in just 15 minutes using a single drop of saliva.

Trey Pittman, a graduate student at Colorado State University, will present his team’s research at the fall meeting of the American Chemical Society (ACS).

“Our device would be ideal for people who are at high risk for heart failure but have limited access to a hospital or central laboratory,” says Pittman.

“Working on this project to address health care disparities in rural and resource-poor areas is a real concern for me because I come from Mississippi, where the death rate from heart failure is among the highest in the United States,” he says.

Heart failure is a weakening of the heart muscle, which cannot pump enough oxygen-rich blood throughout the body. The current gold standard for early detection of heart failure is a twice-yearly blood test performed by a doctor that measures levels of B-type natriuretic peptide (BNP), a protein that indicates that the heart is working too hard.

But new developments in point-of-care devices could bring healthcare parity to simple at-home saliva tests. Such a test for heart failure screening could be performed by a person to check their health every few weeks instead of every six months, Pittman suggests. Until now, the widespread use of portable saliva tests for heart health has been limited by complicated manufacturing processes and the lack of relevant data beyond the presence or absence of a single biomarker.

Pittman and colleagues have addressed these challenges and are presenting promising results using an intuitive, low-cost biosensor prototype they call an electrochemical capillary-driven immunoassay (eCaDI).

Charles Henry’s group at Colorado State University combined two of their previous innovations to develop the wearable testing platform: a saliva microfluidic device and a biosensor for the biomarker proteins galectin-3 and S100A7. Collaborator Chamindie Punyadeera’s group at Griffith University in Australia quantified the concentrations of galectin-3 and S100A7 in saliva, which correlated with heart failure.

The heart failure eCaDI consists of five layers – like a club sandwich: three layers of clear, flexible plastic held together with alternating layers of double-sided tape.

• Tiny holes are drilled into the top plastic layer to insert the saliva sample.
• The middle plastic layer has laser-cut channels with blotting paper squares at the end that draw saliva from the loading point through the channels.
• Between the outer plastic layers are fiberglass reagent pads containing compounds that react with saliva and measure galectin-3 and S100A7 when an electrical current is applied to the device.
• Carbon ink electrodes are screen printed onto the surface of the lower plastic layer.
• Two electrodes, powered by tiny wired terminals from an external source called a potentiostat, control the chemical reaction taking place on the reagent pads.

“The devices are very easy to put together,” says Pittman. “We can make five of them in about 20 to 30 minutes.” The eCaDI is single-use, and researchers estimate that each device costs about $3. The potentiostat, a small reusable power source, costs about $20.

To demonstrate, the researchers spiked standardized human saliva samples with concentrations of the two biomarkers that indicate heart failure. Their results showed that the eCaDI accurately detected the amounts of galectin-3 and S100A7 in saliva.

“These demos are a first step toward a robust and noninvasive electrochemical sensor for heart failure biomarkers,” says Pittman. The next step will be for the team to test eCaDIs at Griffith University in studies with healthy and heart-failed individuals.

“This work could provide a starting point for new saliva testing platforms for other diseases,” explains Pittman. “I think this technology could help many people – especially the underserved – live longer and healthier lives.”