A specific colorimetric signaling of biological thiolsbased on intermolecular n-π charge transfer interaction

A new charge-transfer (CT) complex, consisting of 2,3-dichloro-5-nitro-1,4-naphthoquinone and biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) has been designed to sensing biothiols. The method is selective and sensitive for biothiols detection without the interference of other amino acids.     

Dithiosquarylium-based colorimetric sensors for Hg<Superscript>2+</Superscript>

A new Hg²⁺-selective chemosensor based on dithiosquarylium (DTSQ) dye was investigated. Among various metal cations tested, exclusively Hg²⁺ ion responses to irreversible color change of DTSQ-1, along with the Hg²⁺-triggered desulfurization of dithiosquarylium into its oxygen analogue squarylium (SQ) dye.     

Anti-Microbial,Anti-Biofilm Activities and Cell Selectivity of the NRC-16 Peptide Derived from Witch Flounder,Glyptocephalus cynoglossus

Previous studies had identified novel antimicrobial peptides derived from witch flounder. In this work, we extended the search for the activity of peptide that showed antibacterial activity on clinically isolated bacterial cells and bacterial biofilm. Pseudomonas aeruginosa was obtained from otitis media and cholelithiasis patients, while Staphylococcus aureus was isolated from otitis media patients. We found that synthetic peptide NRC-16 displays antimicrobial activity and is not sensitive to salt during its bactericidal activity. Interestingly, this peptide also led to significant inhibition of biofilm formation at a concentration of 4–16 μM. NRC-16 peptide is able to block biofilm formation at concentrations just above its minimum inhibitory concentration while conventional antibiotics did not inhibit the biofilm formation except ciprofloxacin and piperacillin. It did not cause significant lysis of human RBC, and is not cytotoxic to HaCaT cells and RAW264.7 cells, thereby indicating its selective antimicrobial activity. In addition, the peptide’s binding and permeation activities were assessed by tryptophan fluorescence, calcein leakage and circular dichroism using model mammalian membranes composed of phosphatidylcholine (PC), PC/cholesterol (CH) and PC/sphingomyelin (SM). These experiments confirmed that NRC-16 does not interact with any of the liposomes but the control peptide melittin did. Taken together, we found that NRC-16 has potent antimicrobial and antibiofilm activities with less cytotoxicity, and thus can be considered for treatment of microbial infection in the future.     

Benzothiazole and indole based dye sensor: Optical switching functions with pH stimuli

A new designed dye sensor based on indole as a donor unit and benzothiazole as an acceptor unit have provided very clear optical switching functions when monitored with a pH triggered molecular chemosensor effects in the presence of alkali/acid addition. The prepared dye sensor shows cleared fluorescence quenching effect with alkali addition. The level of energy potential and the electron distribution of this compound were calculated by computational simulation approaches.     

pH triggered switching dye sensor based on furan and pyrone units

pH triggered dye sensor based on pyrone unit as a donor group and furan unit as an acceptor grouphave resulted in very promising optical switches, when dye was applied by alkali-induced nucleophilic additionreaction. The dye displayedclear UV-Visible absorption changes and new fluorescence emission behaviors, which are based on intramolecular charge transfer (ICT) system of the dye molecular structure. The levels of energy potential and the electron density distributions of this dye chemosensor were also simulated and discussed using computational modelcalculation.     

Ionochromism of Crystal Violet Lactone triggered by metal cations

The ionochromic properties of Crystal Violet Lactone(CVL), 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalate with metal cations were investigated. It showed interestingly ring open reaction with addition of several metal ions in CH₃CN solution. Upon addition of Hg²⁺, the CVL shows a new peak around 603nm in its absorption spectra, and the color of solution changed from colorless to blue. Whereas other ions including Fe³⁺, Cu²⁺, Fe²⁺, Al³⁺ and so on induced basically weakly spectral change, which makes it promising application in Hg²⁺ sensor.     

Fluorescent thermometer based on poly(<Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam) with 2D-<Emphasis Type="Italic">π</Emphasis>-A type pyran-based fluorescent dye

A thermoresponsive poly(VCa-co-fluorophore) hydrogel labeled with fluorescent dye was prepared using conventional radical polymerization. A poly(VCa-co-fluorophore) copolymer consisting of N-vinylcaprolactam (VCa) and 2D-π-A type pyran-based fluorescent dye (fluorophore) units behaves as a temperature-driven fluorescent thermometer. This polymer in aqueous solution underwent a phase transition at 27–45 °C. The morphology of the internal microstructure of the poly(VCa-co-fluorophore) hydrogel was observed using SEM.     

Synthesis and VOC ethylamine sensing properties of new colorimetric chemosensor based on thiobarbituric-isophorone chromophore

A new chemosensor based on thiobarbituric-isophorone chromophore (BIC) was synthesized and its volatile organic compounds (VOCs) EtNH₂ sensing properties were investigated by UV-vis absorption spectroscopy. Upon the addition of EtNH₂, the solution of BIC showed clear color change. Sensing mechanism of the BIC to EtNH₂ were confirmed by ¹NMR studies, together with theoretical calculations based on DFT and PPP-MO methods. We have investigated ability of complex formation based on the association constant, K _ass . The BIC test strip was exposed to EtNH₂ gas. Reversible response and recovery were achieved using alternating EtNH₂ gas exposure.     

Novel triazacarbocyanine dye sensor synthesis: pH switching effect

Design, synthesis and pH switching effects of the intramolecular charge transfer (ICT) dye sensor chromophore prepared by the coupling reaction of 6-methoxy-2-aminobenzothiazole (donor moiety) with 4-nitroaniline (acceptor moiety) were carried out and discussed. Optical absorption properties were monitored with the addition of increasing alkali/acid equivalence. In this determination, the prepared pH dye sensor chromophore showed reversible optical switching functions. The levels of energy potential and the electron density distribution of this dye sensor such as HOMO and LUMO values were calculated by computational simulation approaches using Material Studio 4.3. The functions of molecular switching sensor with pH stimulation of alkali-acid addition were determined in DMSO:H₂O, which was operated by deprotonation/protonation effects based on ICT system.