A Switch-On NIR Probe for Specific Detection of Hg²⁺ Ion in Aqueous Medium and in Mitochondria

Abstract

A new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-based probe molecule (L) is synthesized for specific binding to Hg ion in physiological condition with an associated luminescence ON response in the near-IR region of the spectrum. Appropriate functionalization in the 5-position of each of two pyrrole moieties with styryl functionality in a BODIPY core helped us in achieving the extended conjugation and a facile intramolecular charge transfer transition with a narrow energy gap for frontier orbitals. This accounted for a poor emission quantum yield for the probe molecule L. Binding to Hg helped in interrupting the facile intramolecular charge transfer (ICT) process that was initially operational for L. This resulted in a hypsochromic shift of absorption band and a turn-on luminescence response with λ of 650 nm on specific binding to Hg. Observed spectral changes are rationalized based on quantum chemical calculations. Interestingly, this reagent is found to be localized preferentially in the mitochondria of the live human colon cancer (Hct116) cells. Mitochondria is one of the major targets for localization of Hg, which actually decreases the mitochondrial membrane potential and modifies various proteins having sulfudryl functionality(ies) to cause cell apoptosis. Considering these, ability of the present reagent to specifically recognize Hg in the mitochondrial region of the live Hct116 cells has significance.

A highly selective colorimetric and long‐wavelength fluorescent probe for the detection of Hg2+

“…In recent years, many methods have been reported to detect Hg 2+ in the world, including atomic absorption spectroscopy, optical probes, electrochemical analysis, and so on . Specifically, the colorimetric fluorescence probes stand out from numerous detection methods because they allow the target analytes to be detected using the naked‐eye, therefore needing no help from other sophisticated instruments .…”

A carbonothioate‐based highly selective fluorescent probe with a large Stokes shift for detection of Hg2+

“…2.3 | Synthesis of compound 3 [37] Compound 2 (460.5 mg, 2.8 mol) was dissolved in 20 ml absolute alco- [27] 192 15 Yes 55 This work pH 7.4). The free probe solution showed weak fluorescence ( Figure 1) and, when Hg 2+ was added, a large fluorescence intensity enhancement was observed at 562 nm.…”

“…Many methodologies have been used to detect Hg 2+ , such as atomic absorption spectroscopy, electrochemical analysis, inductively coupled plasma mass spectrometry, optical probes and so on . Among these methods, optical probes might be the most attractive method due to their high selectivity, sensitivity, quick response and relatively low‐cost .…”

“…[10] Many methodologies have been used to detect Hg 2+ , such as atomic absorption spectroscopy, electrochemical analysis, inductively coupled plasma mass spectrometry, optical probes and so on. [11][12][13][14][15] Among these methods, optical probes might be the most attractive method due to their high selectivity, sensitivity, quick response and relatively low-cost. [16][17][18][19][20][21][22] Despite reports on Hg 2+ detection, some shortcomings still existed, such as longer response time, bad water solubility, a smaller Stokes shift, and poor selectivity ( Table 1).…”

Highly selective and sensitive fluorescent probe for the rapid detection of mercury ions

“…Nowadays, several classical methods have been applied to determine Hg 2+ including electrochemical analysis, atomic absorption/emission spectroscopy, electrochemical analysis, and inductively coupled plasma mass spectrometry. [19][20][21][22][23] Though these methods are selective and accurate to detect ions, most of them require long time, expensive instruments, and tedious sample pre-treatment. [24][25][26] Thus, the techniques of uorescent probes were widely studied due to the advantages of highly selective, operational simplicity, and relatively low-cost.…”