Improving access to heart failure screening with a low-cost saliva test

Heart failure is a leading cause of death worldwide and is particularly deadly for people without access to medical facilities. A team of researchers aims to bring heart failure screening from the lab to the home. Their prototype point-of-care electrochemical biosensor, which resembles a transparent lateral flow test for COVID-19, can measure levels of two heart failure biomarkers in just 15 minutes from a single drop of saliva.

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

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

“Working on this project to address health disparities in rural and low-resource areas really resonates with me because I come from Mississippi, which has one of the highest heart failure mortality rates in the United States,” he shares.

Heart failure is a weakening of the heart muscle that can no longer pump enough oxygenated blood throughout the body. The current standard for screening for heart failure is a blood test done twice a year by a healthcare professional that measures levels of B-type natriuretic peptide (BNP), a protein that indicates that the heart is working too hard.

However, new developments in point-of-care devices could level the playing field in health care with simple, at-home saliva tests. Such a heart failure screening test could be administered by a person to check their health status every few weeks instead of every six months, Pittman suggests. Until now, widespread use of portable saliva tests for heart health has been limited by complex manufacturing techniques and a lack of relevant data beyond the presence or absence of a single biomarker.

Pittman and his colleagues have addressed these challenges and have promising results to share on an intuitive, inexpensive biosensor prototype, which they call an electrochemical capillary immunoassay (eCaDI).

Charles Henry’s group at Colorado State University combined two of its previous innovations to create the portable testing platform: a salivary microfluidic device and a biosensor for the biomarker proteins Galectin-3 and S100A7. Collaborator Chamindie Punyadeera’s group at Griffith University in Australia quantified levels of Galectin-3 and S100A7 in saliva that correlated with heart failure outcomes.

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

• The top plastic layer has tiny holes drilled into it to load the saliva sample.
• The plastic middle layer has laser-cut channels with blotting paper squares on the end that draw saliva from the loading site through the channels.
• Sandwiched between the outer plastic layers are fiberglass test pads containing compounds that react with saliva and measure Galectin-3 and S100A7 when an electrical current is applied to the device.
• The bottom plastic layer has carbon ink electrodes screen printed on its surface.
• Two electrodes, powered by tiny wired clamps from an external source called a potentiostat, drive the chemical reaction that occurs on the reagent pads.

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

In demonstrations, the researchers added levels of two biomarkers indicative of heart failure to standardized human saliva samples. Their results showed that eCaDI accurately detected the amounts of galectin-3 and S100A7 in saliva.

“These demonstrations are a first step toward a robust, non-invasive electrochemical sensor for heart failure biomarkers,” Pittman says. As a next step, the team will test the eCaDIs at Griffith University in human subject research trials, with both healthy individuals and those with heart failure.

“This work could serve as a starting point for new saliva testing platforms for other diseases,” Pittman says. “It’s a technology that I think could help a lot of people, especially the most disadvantaged, live longer and healthier lives.”