Phenylboronic Acid-Functionalized Ratiometric Surface-Enhanced Raman Scattering Nanoprobe for Selective Tracking of Hg2+ and CH3Hg+ in Aqueous Media and Living Cells

The development of appropriate molecular tools to monitor different mercury speciation, especially CH 3 Hg +, in living organisms is attractive because its persistent accumulation and toxicity are very harmful to human health. Herein, we develop a novel activity-based ratiometric SERS nanoprobe to selectively monitor Hg 2+ and CH 3 Hg + in aqueous media and in vivo. In this nanoprobe, a new bifunctional Raman probe bis-s-s′-[(s)-(4-(ethylcarbamoyl)phenyl)boronic acid] (b-(s)-EPBA) was synthesized and immobilized on the surface of gold nanoparticles via a Au–S bond, in which the phenylboronic acid group was employed as the recognition unit for Hg 2+ and CH 3 Hg + based on the Hg-promoted transmetalation reaction. In the presence of Hg 2+ and CH 3 Hg +, a new surface-enhanced Raman scattering (SERS) peak aroused from of C–Hg appeared at 1080 cm –1, and the SERS intensity at 1002 cm –1 belonged to the B–O symmetric stretching decreased simultaneously. The quantitative tracking of Hg 2+ and CH 3 Hg + was realized based on the SERS intensity ratio ( I 1080 / I 1303 ) with rapid response (∼4 min) and high sensitivity, with detection limits of 10.05 and 25.13 nM, respectively. Moreover, the SERS sensor was used for the quantitative detection of Hg 2+ and CH 3 Hg + in four actual water samples with a high accuracy and excellent recovery. More importantly, cell imaging experiments showed that AuNPs@b-(s)-EPBA could quantitatively detect intracellular CH 3 Hg + and had a good concentration dependence in ratiometric SERS imaging. Meanwhile, we demonstrated that AuNPs@b-(s)-EPBA could detect and image CH 3 Hg + in zebrafish. We anticipate that AuNPs@b-(s)-EPBA could potentially be used to study the physiological functions related to CH 3 Hg + in the future.