Biosensing platform simultaneously detects vitamin C and SARS-CoV-2

In the COVID-19 pandemic era, at-home, portable tests were crucial for knowing when to wear a mask or isolate at home. Now, Penn State engineering researchers have developed a portable and wireless device to simultaneously detect SARS-CoV-2, the virus that causes COVID-19, and vitamin C, a critical nutrient that helps bolster infection resistance, by integrating commercial transistors with printed laser-induced graphene.

Their results were published as the cover article of the November 2024 issue of ACS Applied Materials & Interfaces. By simultaneously detecting the virus and vitamin C levels, the test could help individuals and their health care providers decide on more effective treatment options, the researchers said. For example, someone with low vitamin C levels may benefit from a supplemental boost, while someone with normal or high vitamin C levels may need to consider other options.

“There are several studies that show that vitamin C can help with managing the symptoms of viral respiratory infections like SARS-CoV-2,” said corresponding author Aida Ebrahimi, the Thomas and Sheila Roell Early Career Associate Professor of electrical engineering, of biomedical engineering and of materials science and engineering. “There are testing platforms for vitamin C, but they are bulky, expensive and not suitable for point-of-care, at home testing. Our device is portable, easy to operate and can detect vitamin C and SARS-CoV-2 simultaneously, with the option to add new target molecules to the same testing platform in the future.”

Researchers chose to test vitamin C and SARS-CoV-2 not only for their clinical importance for patients, but also to demonstrate the versatility of their testing approach.

“We used vitamin C and SARS-CoV-2 as model targets to demonstrate the applicability of our approach for detecting biomarkers with the two common types of sensors used in the biosensors community: those with a capture element to ‘capture’ the target molecules, and those without one,” Ebrahimi said. “We used the molecules to show our improvement in the test’s functionality compared to existing methods.”

After processing a small sample of saliva, the device sends results wirelessly to a user’s cell phone, Ebrahimi explained. Users can then continue to monitor their vitamin C levels at home and take a supplement or eat vitamin-rich foods to potentially improve their symptoms.

To develop their sensing platform, the researchers investigated several parameters of laser-induced graphene, which is an incredibly thin material with high sensitivity and other desirable properties. It is fabricated by a highly precise laser printing method to create the sensing material, which has a three dimensional, porous structure. The team assessed its porosity, electrical properties and surface roughness to determine the best number of “passes,” or layers, in which to print the sensors.

The number of passes impacts the sensor’s sensitivity and limit of detection, which refers to the lowest concentration of a substance that can be detected within a certain confidence interval.

“We showed that with two laser printing passes, known as two-pass laser induced graphene, the sensor sensitivity and the limit of detection improve significantly for both vitamin C and SARS-CoV-2,” said first author Heshmat “Amir” Asgharian, a doctoral student in electrical engineering at Penn State.

Similar to the small test strips that diabetes patients use for glucose monitoring, the one-time-use sensing device, which is made on a plastic substrate, is cheap and easy to manufacture, researchers said, while the testing module is reusable.

In addition to Ebrahimi and Asgharian, the co-authors include Vinay Kammarchedu and Pouya Soltan Khamsi, electrical engineering doctoral students at Penn State; and Caroline Brustoloni, who graduated with a master’s degree from Penn State.