Pyridine–Biquinoline–Metal Complexes for Sensing Pyrophosphate and Hydrogen Sulfide in Aqueous Buffer and in Cells

Abstract

Herein, we report a new pyridine-biquinoline-derivative fluorophore L for effectively sensing pyrophosphate (PPi) and monohydrogen sulfide (HS(-)) in aqueous buffer and in living cells. L could selectively coordinate with metal ions (M(n+)) in Groups IB and IIB to form L-M(n+) complexes with 1:1 stoichiometry, resulting in fluorescence quenching via photoinduced electron transfer (PET) mechanism. L-Zn(2+) complex was applied to competitively coordinate with PPi to form a new "ate"-type complex, turning on the fluorescence by a 21-fold-increase. The limit of detection (LOD) of this assay for PPi detection in aqueous buffer is 0.85 μM. L-Cu(2+) complex was applied for highly selective detection of HS(-) with an excellent sensitivity by 25-fold decomplexation-induced fluorescence increase. LOD of L-Cu(2+) complex for HS(-) detection in aqueous buffer is 2.24 μM. With the in vitro data obtained, we successfully applied these two complexes for sequential imaging Zn(2+) and PPi, Cu(2+) and HS(-) in living cells, respectively. Since PPi and HS(-) occur in vascular calcification in positive correlation, our multifunctional probe L might help doctors to more precisely diagnose this disease in vivo in the future. For example, we could use radioactive tracer L-(64)Cu for qualitative and quantitative positron emission tomography/computed tomography (PET/CT) imaging of HS(-) in vivo.

Optical Response of Terpyridine Ligands to Zinc Binding: A Close Look at the Substitution Effect by Spectroscopic Studies at Low Temperature

“…1–3 For example, the weakly fluorescent zinc complex ( 1a –Zn 2+ ; see Scheme 1) 4 was recently shown to generate a large fluorescence turn-on upon addition of a pyrophosphate anion (PPi), while its structural analogue zinc complex shows the response to both mono- and diphosphates. 5 The luminescent properties of a typ–zinc complex are dependent on not only the electronic property of tpy ligand but also the heteroatom X as shown in 1a –ZnX 2 . For example, when X − is sulfonate (CF 3 SO3 − ), the tpy–zinc complex gives emission at ~394 nm.…”

Plasmon‐Enhanced Fluorescence‐Based Core–Shell Gold Nanorods as a Near‐IR Fluorescent Turn‐On Sensor for the Highly Sensitive Detection of Pyrophosphate in Aqueous Solution

“…Given the significance of PPi, numerous PPi reactive and selective fluorescent probes have been developed in the past decades . However, owing to the issues, including strong hydration of anions and low solubility of organic probes, the majority of methods require organic or mixed aqueous media in previous researches, which greatly limits analytical application . Up to now, the sensitivity toward PPi detection in aqueous media is invariably limited to micromolar levels in recent reports and their emission spectra are mostly in the short wavelength range from 400 to 600 nm.…”

Peptide‐based supramolecular hydrogels for delivery of biologics

“…Rapid responses to diverse external stimuli are easy to achieve because of the highly reversible property of non‐covalent interactions. Extensive research and reviews have discussed supramolecular hydrogels formed by urea derivatives, serine‐based amphiphiles, pyridine‐containing hydrogelators, multi‐component small molecule systems, drug amphiphiles, and so on. Peptide‐, nucleobase‐, and saccharide‐based molecules are the three common supramolecular hydrogelators .…”