Key Results and Findings

Wearable Biochip Design

The research team developed a wearable multimodal biochip that integrates an electrochemical sensor with microfluidic channels to monitor multiple indicators in sweat, including Phe concentration, chloride levels, and sweat rate. 

Unlike most existing sweat biosensors, which typically measure a single indicator (such as glucose or lactate), this biochip’s design enables the simultaneous measurement of multiple indicators, providing a comprehensive analysis of exercise metabolism.

The biochip on skin for multimodal sweat sensing

Phenylalanine Sensing

A molecularly imprinted polymer (MIP) electrode, which consists in creating specific cavities in a polymer matrix that are tailored to selectively bind and detect target molecules, was used to create a selective sensor for Phe, enabling direct electrocatalytic oxidation and quantification of Phe in sweat. This approach overcomes the limitations of previous methods that relied on indirect detection techniques, which were less sensitive and required more complex procedures.

Sweat Rate Normalization

The researchers introduce a novel method for correlating sweat phenylalanine levels with blood levels by normalizing the concentrations based on sweat rate. Most existing biosensors do not account for sweat rate, which can significantly affect the concentration of biomarkers in sweat and lead to misleading results. This approach reduces interindividual variability, allowing for more accurate correlations between sweat and blood Phe levels. The study demonstrated a negative correlation between Phe concentration and sweat rate, suggesting that Phe loss through sweat is influenced by both diffusion from blood and skin surface contributions.

Metabolic Risk Assessment

The study also introduced a new indicator, the Phe secretion rate (SP), which combines Phe concentration and sweat rate to assess metabolic risk during exercise. The researchers identified subjects with high metabolic risk based on their SP values, demonstrating the biochip’s potential for personalized health monitoring.

Correlation with Blood Phe Levels

A pilot study involving volunteers showed a strong correlation between sweat and serum Phe levels, particularly after normalizing the data by sweat rate. This finding supports the biochip’s potential use in non-invasive monitoring of blood Phe levels, making it a promising tool for managing conditions like phenylketonuria (PKU) or monitoring dietary protein intake.

Implications and Future Directions

The development of this multimodal biochip represents a significant advancement in the field of wearable biosensors, particularly for exercise and metabolic monitoring. By providing real-time, non-invasive measurements of critical biomarkers, the biochip could be used in various applications, from personalized fitness programs to managing chronic conditions like PKU.

Future work could expand on these findings by involving a larger and more diverse population to strengthen the correlation between sweat and blood Phe levels. Additionally, the biochip’s design could be adapted to monitor other non-NMF AAs or integrate additional sensors for a broader range of health indicators.

Conclusion

The study successfully demonstrates the feasibility of using a wearable multimodal biochip for in situ monitoring of Phe and other sweat indicators during exercise. This innovative approach not only provides valuable insights into individual metabolic responses but also lays the groundwork for more sophisticated, personalized health monitoring systems.

Reference

The research was conducted by a team from various institutions, including the State Key Laboratory for Superlattices and Microstructures at the Chinese Academy of Sciences and the School of Chemical Engineering at Sungkyunkwan University. The full study is available in Nature Communications (2024), DOI: 10.1038/s41467-024-44751-.