Changqing Yi

Synthesis, characterization, and DNA binding of a novel ligand and its Cu(II) complex

A novel naphthalene-2,3-diamine-2-salicylaldehyde (NS) ligand and its mononuclear copper(II) complex (CuNS) have been synthesized and structurally characterized. The UV–vis absorption and emission spectra of NS showed obvious changes on addition of Cu2+ solution. The interaction of the compounds with calf thymus DNA and G-quadruplex DNA were investigated by spectroscopic methods and thermal melting assay. The nucleolytic cleavage activity of the compounds was investigated on double-stranded circular pBR322 plasmid DNA and G-quadruplex DNA by electrophoretic mobility shift assay. The results show that CuNS has a greater ability to stabilize G-quadruplex DNA over calf-thymus DNA. The cytotoxicity of the compounds toward HpeG2 cancer cells was also studied, and they showed significant potential for antineoplastic effects.

One-pot synthesis of gadolinium-doped carbon quantum dots for high-performance multimodal bioimaging

In this study, an efficient and mild approach is reported for the facile synthesis of a carbon quantum dot (CQD)-based dual-modal fluorescence (FL)/magnetic resonance (MR) imaging probe by doping Gd(iii) into CQDs through a one-pot pyrolysis process at low temperature. The as-prepared Gd-encapsulated CQDs (GCDs), which have an average diameter of ∼15 nm, are highly water-soluble. The GCDs are observed to have a high MR response with a longitudinal relaxation of 57.42 mM-1 s-1 and a strong fluorescence brightness with an absolute quantum yield of 40% while containing only 1.0% (w/w) of Gd3+ content. Stemming from the minimum Gd-doping and the inert carbon coating, GCDs exhibit excellent biocompatibility and blood compatibility. Dual-modality bioimaging applications of GCDs are successfully demonstrated by the use of HeLa cells and mice as models, revealing their great potential in fundamental biomedical research studies and even clinical fields such as fluorescence-guided surgery and dual-modal FL/MR imaging of blood vessels.

Coumarin-modified gold nanoprobes for the sensitive detection of caspase-3

Caspase-3 has been identified as a key mediator and a well-established cellular marker of apoptosis. To increase the sensitivity, coumarin-functionalized gold nanoparticles (AuNPs) connected to polypeptide chains containing specific sequences (DEVD) were designed and synthesized for the sensing of caspase-3, because there was a large overlap between the emission of coumarin-343 and the absorption of the AuNPs. The fluorescence of coumarin 343 was quenched due to the energy transfer process by the gold nanoparticles. The fluorescence could be restored after the particular polypeptide sequence (DEVD) was cut off by caspase-3. Based on this mechanism, the caspase enzyme activity in vitro could be detected by a fluorescence assay with a high sensitivity. The effect of the different lengths of polypeptide chains on the luminescence quenching efficiency and sensing ability was also studied, which is of great importance in designing FRET-based sensing platforms. This kind of sensitive luminescent functional coumarin 343-modified gold nanoprobe is suitable for caspase-3 sensing in biological applications.

Grafting polyethylenimine with quinoline derivatives for targeted imaging of intracellular Zn(2+) and logic gate operations.

In this study, a highly sensitive and selective fluorescent Zn(2+) probe which exhibited excellent biocompatibility, water solubility, and cell-membrane permeability, was facilely synthesized in a single step by grafting polyethyleneimine (PEI) with quinoline derivatives. The primary amino groups in the branched PEI can increase water solubility and cell permeability of the probe PEIQ, while quinoline derivatives can specifically recognize Zn(2+) and reduce the potential cytotoxicity of PEI. Basing on fluorescence off-on mechanism, PEIQ demonstrated excellent sensing capability towards Zn(2+) in absolute aqueous solution, where a high sensitivity with a detection limit as low as 38.1nM, and a high selectivity over competing metal ions and potential interfering amino acids, were achieved. Inspired by these results, elementary logic operations (YES, NOT and INHIBIT) have been constructed by employing PEIQ as the gate while Zn(2+) and EDTA as chemical inputs. Together with the low cytotoxicity and good cell-permeability, the practical application of PEIQ in living cell imaging was satisfactorily demonstrated, emphasizing its wide application in fundamental biology research.