Development of a green metallochromic indicator for selective and visual detection of copper(II) ions.

Heavy metal ions, i.e., copper(II) (Cu(II)), are harmful to the environment and our health. The current research established an eco-friendly and efficient metal-sensitive indicator, which can identify Cu(II) ions in both liquid and solid forms, by utilizing anthocyanin extract obtained from jambolao fruit (Syzgium cumini) that is incorporated within bacterial cellulose nanofibers (BCNF).The CIE Lab color parameters demonstrated that Cu(II) binding causes a sensible change in color. It was observed that the visible color altered with an increase in the Cu(II) concentration. The bacterial cellulose nanofibers that were altered with anthocyanin were analyzed using ATR-FTIR and FESEM. The sensor's selectivity was tested by using a range of metal ions such as lead (Pb2+), cobalt (Co2+), cadmium (Cd2+), nickel (Ni2+), aluminium (Al3+), barium (Ba2+), manganese (Mn2+), zinc (Zn2+), mercury (Hg2+) and sodium (Na+). The findings demonstrated that the suggested sensor showed excellent selectivity toward Cu(II) ion. Cu(II) can be accurately identified using the sensing technique, with detection limits ranging from 10-400 ppm and 50-500 ppm for liquid and solid samples, respectively, and through observation with naked eye. The fabricated green metallochromic sensor is promising to be a simple, cheap, mobile and easily operable for the real-time and on-site detection of Cu(II) ion.

Development of a pH-sensing indicator for shrimp freshness monitoring: Curcumin and anthocyanin-loaded gelatin films.

An intelligent pH-sensing indicator containing Roselle (Hibiseus sabdariffa L.) (RS) anthocyanin and curcumin (CR) was developed and characterized as on-package indicator tags to check the freshness of shrimp during the storage at 4°C. FE-SEM and FT-IR analysis showed that RS and CR were successfully immobilized in the gelatin-glycerol film-forming substrate. The addition of various natural dyes increased the thickness and antioxidant action of the colorimetric film. To assess the response to changes in the pH, the colorimetric film was immersed in different buffers. Based on volatile amines secreted by shrimp, a test application of a colorimetric film containing natural dyes at a ratio of CR:RS = 1:4 (v/v) was conducted in shrimp at 4°C. The total volatile basic nitrogen (TVB-N) and the pH of shrimp were monitored during refrigerated storage for 10 days, and the color changes of the indicator were recorded simultaneously. The results indicated that the designed colorimetric film could produce various colors, which are thought to be indicative of the freshness and spoilage of packaged shrimp. Therefore, the target film can be utilized as a promising smart packaging material for monitoring the freshness of shrimp and aquatic products in real time.

Anthocyanin-induced color changes in bacterial cellulose nanofibers for the accurate and selective detection of Cu(II) in water samples.

The environment and our health are negatively impacted by heavy metal ions, like Cu(II). The present study developed a green and effective metallochromic sensor that detects copper (Cu(II)) ions in solution and solid state using anthocyanin extract from black eggplant peels embedded in bacterial cellulose nanofibers (BCNF). Cu(II) is quantitatively detected by the sensing method with detection limits between 10-400 ppm and 20-300 ppm in solution and solid state, respectively. In the solution state, we depicted a sensor for Cu(II) ions in aqueous matrices in the pH range from 3.0 to 11.0, with the capability to produce a visual color change from brown to light blue and dark blue depending on the Cu(II) concentration. Additionally, BCNF-ANT film can act as a sensor for Cu(II) ions in the pH range of 4.0-8.0. Neutral pH was selected from the standpoint of high selectivity. It was found that visible color changed when Cu(II) concentration was increased. Bacterial cellulose nanofibers modified with anthocyanin were characterized with ATR-FTIR and FESEM. Various metal ions, including Pb2+, Co2+, Zn2+, Ni2+, Al3+, Ba2+, Hg2+, Mg2+, and Na+, were used to challenge the sensor to determine its selectivity. Anthocyanin solution and BCNF-ANT sheet were employed in the actual tap water sample successfully. The results also clarified that the various foreign ions did not significantly interfere with Cu(II) ions detection at optimum conditions. Compared to previously developed sensors, no electronic components, trained personnel, or sophisticated equipment were needed to apply the colorimetric sensor developed in this research. Cu(II) contamination in food matrices and water can be monitored on-site easily.

Copper(II)/polyimide linked covalent organic framework as a powerful catalyst for the solvent-free microwave irradiation-based synthesis of 2,4,5-trisubstituted imidazoles.

Copper(II)/polyimide-linked covalent organic frameworks under solvent-free and microwave-assisted conditions have been used in an efficient one-pot protocol for the preparation of 2,4,5-trisubstituted imidazoles via benzil, aromatic aldehydes and ammonium acetate. By applying solvent-free conditions and microwave irradiation, three-component condensation provides safe operations, low pollution, quick access to products, and an easy set-up. As a result of its reusability, the catalyst can also be reutilized for many runs without missing any activity.

Anthocyanin-loaded bacterial cellulose nanofiber as a green sensor for monitoring the selective naked eye and visual detection of Al(III) Ions.

The present study developed a green metallochromic sensor that detects aluminium (Al(III)) ions in solution and solid state using anthocyanin extract from purple onion peels embedded in bacterial cellulose nanofibers (BCNFs). The CIE Lab colour parameters demonstrated that Al(III) binding causes a sensible change in colour. A variety of metal ions including K+, Mn2+, Cu2+, Hg2+, Cr2+, Pb2+ and Ni2+ were used to challenge the sensor to determine its selectivity. The findings demonstrated that the suggested sensor showed excellent selectivity toward Al(III) ion. Al(III) is quantitatively detected by the sensing method with detection limits in the range between 30-200 and 20-300 ppm in solution and solid state, respectively, and through observation with naked eye. The fabricated green metallochromic sensor is promising to be a simple, cheap, mobile and easily operable for real-time and on-site detection of Al(III) ions in food matrices.

Selective Ligand-Doped Liquid Crystal-Based Sensing Platform for Detection of ClO- Ions in Aqueous Media.

The liquid crystal (LC) detection platform has been fabricated for the detection of hypochlorite ions (ClO-) in aquatic solutions. In this system, an imine consisting of the ligand (E)-2-((4-(diethylamino)-2-hydroxybenzylidene)amino)-5-methoxybenzenesulfonic acid (MBA) was doped in 4-cyano-4'-pentyl biphenyl as a selecting LC for ClO-. When immersing the platform in a solution containing ClO-, hypochlorite appears to react with the imine bond in the MBA, and cause it to cleave, which eventually disrupts the direction of LC and causes a dark-to-bright conversion of the LC image. The detection limit for ClO- is 0.05 µM. This sensory platform was unresponsive to NO3 -, BrO3 -, CH3COO-, CO3 2-, and PO4 3- ions. Our sensing platform also detected ClO- in piped water. Since this sensory platform is colored under ambient light, it is easy for regular operators, and it can be used as a mobile tool for monitoring water quality anywhere.

A cationic surfactant-decorated liquid crystal-based sensor for sensitive detection of quinoline yellow.

Quinoline yellow (QY) is one of the popular synthetic food colorants and in food industry greatly used. Developing accurate and simple QY detection procedures is of major considerable importance in ensuring food safety. Hence, it is important to detect this food colorant effectively to reduce risk. Herein, an innovative liquid crystal (LC)-based sensor was designed for the label-free and ultra-sensitive detecting of the QY by means of a cationic surfactant-decorated LC interface. The nematic liquid crystal in touch with CTAB revealed a homeotropic alignment, when QY was injected into the LC-cell, the homeotropic alignment consequently altered to a planar one by electrostatic interactions between QY and CTAB. The designed LC-based sensor detected QY at the too much trace level as low as 0.5 fM with analogous selectivity. The suggested LC-based sensor is a rapid, convenient and simple procedure for label-free detection of QY in food industrial and safety control application.

Bovine ß-casein binding studies of a Schiff base ligand: fluorescence and circular dichroism approaches.

In this study, a Schiff base derived from a heterocyclic moiety was synthesized and characterized. The in vitro binding behaviour of this ligand with ß-casein (ß-CN) was investigated using biophysical techniques. For evaluation, thermodynamics variables of interactions between the Schiff base ligand and ß-CN, such as fluorescence at different temperatures, were measured. The results showed that the Schiff base ligand possessed considerable associated binding to ß-CN and that the procedure was enthalpy driven. The ß-CN conformation was also changed to give a further unfolded structure. Fluorescence resonance energy transfer was used to estimate the interval between donor (ß-CN) and acceptor (Schiff base ligand). All these experimental results proposed that ß-CN might act as carrier protein for the Schiff base ligand to deliver it to the target molecules.

Synthesis and Characterization of Cobalt(II) and Manganese(II) Schiff Base Complexes: Metal Effect on the Binding Affinity with ß-Casein.

In this study, two metal Schiff base complexes (cobalt(II) and manganese(II), were synthesized and characterized by 1H-NMR and FT-IR analyses. The in vitro binding behavior of this complexes with ß-Casein (ß-CN) was investigated by using biophysical techniques. For evaluation the thermodynamics parameters of interaction between Schiff base complexes and ß-CN,the fluorescence data at different temperatures were done. The results showed that the intrinsic fluorescence of the ß-CN was quenched by increasing the complexes through the dynamic quenching mechanism. Also, these complexes demonstrated a considrable binding affinity to ß-CN and the process is mainly entropy driven. Fluorescence resonance energy transfer was used in order to estimating the distance between donor (ß-CN) and acceptor (complex). Results demonstrated that the sequence of tendency of the complexes to ß-CN was as follows: Mn-Schiff base complex > Co-Schiff base complex. All these experimental results propose that ß-CN might act as carrier protein for Co(II) and Mn (II) complexes to deliver it to the target molecules.

Spectroscopy and molecular dynamics simulation study on the interaction of sunset yellow food additive with pepsin.

The interaction of pepsin with sunset yellow food additive (SY) was studied by fluorescence spectroscopy and molecular dynamics simulation. The experimental results indicated that SY can quench the fluorescence of pepsin with static quenching. The apparent binding constant Ka and binding site number n were evaluated at different temperatures. Thermodynamic analysis suggests that SY interact with pepsin spontaneously by van der Waal's forces and hydrogen bond formation. Three-dimensional fluorescence spectra showed that pepsin undergoes a slightly conformation change when it interacts with SY. The molecular dynamics simulation (MD) revealed that the binding site is located mainly on the tyrosine residues at the entrance of the active site of pepsin and the main interactions occurred between SY and pepsin are hydrogen bond and stacking interactions, according to experimental results. Furthermore, the binding between SY and pepsin can inhibit pepsin activity. Our MD results showed that the SY prevents substrate from entering the active site by making a barrier at the entrance of the active site, reducing the pepsin activity.

Combined multispectroscopic and molecular dynamics simulation investigation on the interaction between cyclosporine A and ß-lactoglobulin.

ß-Lactoglobulin (ß-LG), the major whey protein in milks of many mammals, has a high affinity for a wide range of compounds. Cyclosporine A (CsA), is an immunosuppressant drug mainly prescribe in organ transplantation to prevent rejection. In this study, the interaction of CsA with ß-LG was investigated using various spectroscopic techniques (UV-visible and fluorescence) in an aqueous medium at two temperatures of 298 and 310K in combination with a molecular dynamics simulation study. The titration results indicated that CsA quenched the fluorescence intensity of ß-LG through a static mechanism. The binding constants for the binding of CsA to ß-LG at two different temperatures 298 and 310K were obtained 1.12×105 and 0.87×105M-1, respectively. Thermodynamic data indicated that the hydrophobic interactions and hydrogen bonds dominate in the binding site. Results of fluorescence resonance energy transfer (FRET) measurements suggest that resonance energy transfer occurs between ß-LG and CsA. Moreover, MD simulation results implied that CsA can interact with ß-LG, without affecting the secondary structure of ß-LG. Experimental and MD simulations data reciprocally supported each other.

Investigation into the interaction of losartan with human serum albumin and glycated human serum albumin by spectroscopic and molecular dynamics simulation techniques: A comparison study.

The interaction between losartan and human serum albumin (HSA), as well as its glycated form (gHSA) was studied by multiple spectroscopic techniques and molecular dynamics simulation under physiological conditions. The binding information, including the binding constants, effective quenching constant and number of binding sites showed that the binding partiality of losartan to HSA was higher than to gHSA. The findings of three-dimensional fluorescence spectra demonstrated that the binding of losartan to HSA and gHSA would alter the protein conformation. The distances between Trp residue and the binding sites of the drug were evaluated on the basis of the Förster theory, and it was indicated that non-radiative energy transfer from HSA and gHSA to the losartan happened with a high possibility. According to molecular dynamics simulation, the protein secondary and tertiary structure changes were compared in HSA and gHSA for clarifying the obtained results.