Vitamin B6 supports immune function and brain health, but can be deficient in individuals with illnesses like diabetes, leading to symptoms such as fatigue, depression, and numbness. Currently, B6 levels are only measurable through blood tests.
The sensor, developed by a team led by Huanyu Cheng, Memorial Associate Professor of Engineering Science and Mechanics at Penn State, uses laser-induced graphene nanocomposites as a scaffold for molecularly imprinted polymers (MIPs). These synthetic polymers mimic biological receptors and selectively bind to target molecules like vitamin B6 and glucose.
To enhance signal detection, the team incorporated Prussian blue redox probes, which produce an electrical signal when target molecules are present. The system is also designed to be regenerable and stable across repeated uses, with improved reliability over time.
It can detect B6 concentrations as low as 0.93 nM, well below the ~100 nM usually found in sweat, and achieved a high sensitivity of 39.95 μA log10 (μM)-1 mm-2 for vitamin B6.
Since vitamin B6 is a very trace molecule available in the sweat only at small quantities, we had to determine a different approach for detecting it using an artificial enzyme, or MIP. The MIP in the testing platform binds to the target molecule, giving it a one-to-one process match with a high selectivity to the target molecule, like a toddler fitting a shape into a shape sorter.
Huanyu "Larry" Cheng, the James L. Henderson, Jr. Memorial Associate Professor, Engineering Science and Mechanics, Penn State
For glucose detection, the platform demonstrated a sensitivity of 19.33 μA log10 (μM)-1 mm-2, providing accurate measurements without invasive sampling. The researchers also included a microfluidic module in the sensor, enabling continuous, near-instant monitoring of sweat during physical activity.
Due to the versatility and adaptability of using MIPs, the sensing platform is versatile and will work to also detect other biomarkers, like glucose. We would just change the MIP to target other proteins of interest, such as female reproductive hormones or proteins indicating an infectious disease, like sepsis, which we hope to do in subsequent phases of research.
Huanyu "Larry" Cheng, the James L. Henderson, Jr. Memorial Associate Professor, Engineering Science and Mechanics, Penn State
Cheng explained that monitoring vitamin B6 along with other vitamins can be beneficial for enhancing patient health, as variations in vitamin B6 levels may signify a weakened immune system.
If health care providers detect a large fluctuation of vitamin B6 in the sweat, it can indicate that the patient will be more vulnerable to disease conditions, particularly if they have chronic conditions like diabetes. The production of antibodies and the corresponding health of the immune system relies on a steady source of B6, so patients could potentially make changes before they get sick.
Huanyu "Larry" Cheng, the James L. Henderson, Jr. Memorial Associate Professor, Engineering Science and Mechanics, Penn State
The device addresses the challenge of detecting non-electroactive substances like B6, which cannot be directly oxidized or reduced. By combining laser-induced graphene's conductivity with the selective binding capabilities of MIPs, the system enables indirect detection at ultralow concentrations, even in complex fluids like sweat.
Journal Reference:
Yang, L., et al. (2025) Laser-induced graphene nanocomposites with molecularly imprinted polymers and Prussian blue for electrochemical sensing of vitamin B6 and glucose. Composites Part B: Engineering. doi.org/10.1016/j.compositesb.2025.112843