New SERS probe that can accurately monitor the pH Variation in Live Cells

Intracellular pH is an important regulator of cell physiological activities and an important parameter for studying cell functions. Fluorescent probes are currently an effective method for detecting the pH value in cells. However, fluorescent probes have shortcomings such as low fluorescence intensity, narrow excitation spectrum, and easy photobleaching. Therefore, surface-enhanced Raman scattering (SERS) probes are used in intracellular pH detection, cell imaging, and intracellular multi-component detection application.

Professor Liu Dingbin of Nankai University and others reported a robust Prussian blue (PB)-caged pH-responsive surface-enhanced Raman scattering (SERS) probe for precisely mapping the dynamic pH values in live cells.

Prussian blue has excellent electrochemical reversibility and stability, and is widely used in the fields of electrochemistry and electronics. The coating of Prussian blue material on the substrate not only improves its agglomeration, but also forms an attractive color. 

The Prussian blue shell used in the study has a subnanoscale porous structure that allows only very small biospecies such as H⁺ or OH^– to pass freely through the shell and react with the encased pH-responsive SERS probe, while physically resisting the entry of large biomolecules. This probe achieved unmatched detection linearity (R2 > 0.999) for pH measurements in diverse complex biological samples. Moreover, the nitrile (C≡N) in PB shows a sharp band in the cellular Raman-silent region, which serves as a background-free internal standard for accurate profiling of the probe distribution inside the cells.

Researchers applied the proposed probe to monitor the dynamic pH changes during cellular autophagy induced by different stimuli and thereby demonstrated that the PB-caged probe can reliably quantify subtle intracellular pH variations, providing an effective tool for revealing the relationship between abnormal intracellular pH and cellular functions.

Reference: Yingna Bi. et al. Reliable Quantification of pH Variation in Live Cells Using Prussian Blue-Caged Surface-Enhanced Raman Scattering Probes. Analytical Chemistry. 2020.DOI: 10.1021/acs.analchem.0c00714