Highly selective detection of intracellular glutamine (Gln) is very essential to understand the roles of Gln in some biological processes. Here, we report a new fluorescent method for selective imaging of Gln in live cells with an aldehyde-containing iridium complex, [Ir(pba)2(DMSO)2]PF6 (Hpba = 4-(2-pyridiyl)benzaldehyde) (Ir1), as the probe. Density functional theory (DFT) calculation and experimental results suggest that the coordination and hydrogen bonding interaction between Ir1 and Gln synergistically stabilize the Ir1–Gln complex, modulate charge-transfer characteristics and emission of Ir1, and as a consequence, enable Ir1 as the probe for the fluorescent sensing of Gln. The sensing strategy is well-responsive to Gln without interference from other amino acids or Gln-containing peptides and is demonstrated to be useful for in situ Gln imaging in live cells. The study provides a new method for fluorescent imaging of Gln in live cells, which is envisioned to find interesting applications in understanding the roles of Gln in some physiological processes.

In this study, we demonstrate a facile and environmentally friendly method for the synthesis of glutathione (GSH)-capped water-soluble CdS quantum dots (QDs) with a high cytocompatibility and a tunable optical property based on alkaline post-treatment of Cd–GSH coordination polymers (CPs). Cd–GSH CPs are synthesized with the coordination reaction of Cd2+ with GSH at different pH values, and the CdS QDs are then formed by adding NaOH to the aqueous dispersion of the Cd–GSH CPs to break the coordination interaction between Cd2+ and GSH with the release of sulfur. The particle size and optical property of the as-formed CdS QDs are found to be easily tailored by simply adjusting the starting pH values of GSH solutions used for the formation of Cd–GSH CPs, in which the wavelengths of trap-state emission of the QDs red-shift with an increase in the sizes of the QDs that is caused by an increase in the starting pH values of GSH solutions. In addition, the use of GSH as the capping reagent eventually endows the as-formed CdS QDs with enhanced water solubility and good cytocompatibility, as demonstrated with HeLa cells. The method demonstrated here is advantageous in that the cadmium precursor and the sulfur source are nontoxic and easily available, and the size, optical properties, water solubility, and cytocompatibilty of the as-formed CdS QDs are simply achieved and experimentally regulated. This study offers a new and green synthetic route to water-soluble and cytocompatible CdS QDs with tunable optical properties.Keywords: CdS quantum dots; coordination polymers; cytocompatibility; glutathione; green synthesis; water solubility;

This study demonstrates the first exploitation of zeolitic imidazolate frameworks (ZIFs) as the matrix for constructing integrated dehydrogenase-based electrochemical biosensors for in vivo measurement of neurochemicals, such as glucose. In this study, we find that ZIFs are able to serve as a matrix for coimmobilizing electrocatalysts (i.e., methylene green, MG) and dehydrogenases (i.e., glucose dehydrogenase, GDH) onto the electrode surface and an integrated electrochemical biosensor is readily formed. We synthesize a series of ZIFs, including ZIF-7, ZIF-8, ZIF-67, ZIF-68, and ZIF-70 with different pore sizes, surface areas, and functional groups. The adsorption capabilities toward MG and GDH of these ZIFs are systematically studied with UV–vis spectroscopy, confocal laser scanning microscopy, and Fourier transfer-infrared spectroscopy. Among all the ZIFs demonstrated here, ZIF-70 shows excellent adsorption capacities toward both MG and GDH and is thus employed as the matrix for our glucose biosensor. To construct the biosensor, we first drop-coat a MG/ZIF-70 composite onto a glassy carbon electrode and then coat GDH onto the MG/ZIF-70 composite. In a continuous-flow system, the as-prepared ZIF-based biosensor is very sensitive to glucose with a linear range of 0.1–2 mM. Moreover, the ZIF-based biosensor is more highly selective on glucose than on other endogenous electroactive species in the cerebral system. In the end, we demonstrate that our biosensor is capable of monitoring dialysate glucose collected from the brain of guinea pigs selectively and in a near real-time pattern.