The availability of rapid, accessible testing was integral to overcoming the worst surges of the COVID-19 pandemic, and will be necessary to keep up with emerging variants. However, these tests come with unfortunate costs.

Polymerase chain reaction (PCR) tests, the “gold standard” for diagnostic testing, are hampered by waste. They require significant time (results can take up to a day or more) as well as specialized equipment and labor, all of which increase costs. The sophistication of PCR tests makes them harder to tweak, and therefore slower to respond to new variants. They also carry environmental impacts. For example, most biosensor tests developed to date use printed circuit boards, or PCBs, the same materials used in computers. PCBs are difficult to recycle and slow to biodegrade, using large amounts of metal, plastic and non-eco-friendly materials.

In addition, most PCR tests end up in landfills, resulting in material waste and secondary contamination. An analysis by the World Health Organization (WHO) estimated that, as of February 2022, “over 140 million test kits, with a potential to generate 2,600 tonnes of non-infectious waste (mainly plastic) and 731,000 litres of chemical waste (equivalent to one-third of an Olympic-size swimming pool) have been shipped.”

In order to balance the need for fast, affordable and accurate testing while addressing these environmental concerns, César de la Fuente, a Presidential Assistant Professor in the departments of bioengineering and chemical & biomolecular engineering in the School of Engineering and Applied Science, with additional primary appointments in psychiatry and microbiology in the Perelman School of Medicine, has turned his attention to the urgent need for “green” testing materials.

The de la Fuente lab has been working on creative ways to create faster and cheaper testing for COVID-19 since the outbreak of the pandemic.

The team’s latest innovation incorporates the speed and cost-effectiveness of previous tests with eco-friendly materials. In a paper published in Cell Reports Physical Science, the group introduces a new test made from Bacterial Cellulose (BC), an organic compound synthesized from several strains of bacteria, as a substitute for PCBs.

Bacteria naturally serves as a “factory” for the production of cellulose, a paper-like substance which can be used as the basis for biosensors. BC is highly versatile, having been used for wound care, regenerative medicine and point-of-care or POC diagnostics. POC testing is especially important for the prevention of pandemics, in that it allows for quick and accurate diagnostics at the testing site without the need for expensive, specialized equipment or for the samples to be sent away to a lab. This new BC test is non-toxic, naturally biodegradable and both inexpensive and scalable to mass production, currently costing less than $4.00 per test to produce. Its cellulose fibers do not require the chemicals used to manufacture paper, and the test is almost entirely biodegradable. (The exception is a small amount of silver, which can be easily removed and recycled by healthcare professionals.)

In addition to these green benefits, the test proved highly accurate in clinical trials, correctly identifying multiple variants in under ten minutes. This means that the tests won’t require “recalibration” to accurately test for new variants.

As researchers and healthcare providers continue to manage the effects of COVID-19, and look ahead to the prevention of future pandemics, inexpensive and accurate testing that is also environmentally friendly is crucial to protecting the health of both our planet and its people. The results of this study suggest that these goals need not be mutually exclusive.

Adapted from a Penn Engineering news article by Kat Sas, August 25, 2023.