Easy detection of enzymes with the electrochemical-SERS effect

Significance of the Topic

Surface-enhanced Raman spectroscopy (SERS) combined with electrochemical control offers a powerful approach to detect and characterize low-concentration biomolecules. By activating silver electrodes electrochemically, Raman signal amplification enables fingerprint identification of enzymes that are otherwise challenging to observe.

Objectives and Overview

This study aimed to develop a straightforward, in-situ method for enzyme detection using the electrochemical-SERS (EC-SERS) effect. Two model enzymes—aldehyde dehydrogenase (ALDH) and cytochrome c—were selected to demonstrate proof-of-concept on both screen-printed and conventional silver electrodes.

Methodology and Instrumentation

The protocol consists of two sequential steps in a single experiment:

• Electrochemical activation: scanning from positive to negative potentials to oxidize and then reduce the silver surface, creating SERS-active nanostructures.
• Operando Raman detection: continuous spectral acquisition during potential cycling to capture optimal signal intensity.

Key instrumentation:

• SPELEC RAMAN 638 spectroelectrochemical system (638 nm laser)
• DropView SPELEC control software
• Silver screen-printed electrodes (Ag SPEs) and conventional Ag working electrodes with steel counter and Ag/AgCl reference electrodes

Main Results and Discussion

For ALDH detection on Ag SPEs, the highest Raman intensity was recorded at –0.50 V in 0.1 M KCl, revealing characteristic bands that had not been previously reported for this enzyme. Cytochrome c analysis on conventional electrodes, scanned from +0.80 V to –0.80 V, yielded its strongest SERS response at –0.70 V. Band assignments between 713 and 1604 cm⁻¹ were used to confirm enzyme identity and to distinguish reduced from oxidized states based on band position shifts.

Benefits and Practical Applications

This EC-SERS approach provides:

• Rapid, label-free enzyme detection in aqueous media
• Enhanced sensitivity through electrochemical activation
• Simultaneous electrochemical and spectroscopic monitoring for real-time analysis

Potential applications include biochemical assays, clinical diagnostics, and on-site quality control.

Future Trends and Applications

Advancements may focus on:

• Extending the method to a broader range of biomolecules and complex matrices
• Miniaturizing and multiplexing electrode formats for high-throughput screening
• Integrating machine-learning algorithms for automated spectral interpretation

Conclusion

The developed spectroelectrochemical protocol demonstrates an efficient route to activate SERS-sensitive silver surfaces and detect enzymes with high specificity. It expands analytical capabilities for enzymatic studies and paves the way for real-time biochemical sensing.

References

• Martin-Yerga et al. Electrochimica Acta 2018, 264, 183–190.
• Brazhe et al. Sci Rep 2015, 5, 13793.
• Hu et al. J. Am. Chem. Soc. 1993, 115(26), 12446–12458.