Encapsulation of ciprofloxacin,sparfloxacin, and ofloxacin drugs with α- and β-cyclodextrins: spectral and molecular modelling studies

Inclusion complexation of ciprofloxacin (CIP), sparfloxacin (SPA), and ofloxacin (OFL) drugs with α-CD and β-CD was studied by UV-visible, fluorescence, time-resolved fluorescence, Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (¹HNMR), scanning electron microscopy (SEM), and molecular modelling techniques. Changes in the absorbance and fluorescence intensities and fluorescence lifetime of the drugs in the cyclodextrin (CD) solutions suggest the formation of inclusion complexes. Carbonyl stretching frequency moved to higher wave numbers and broadening of the N–H stretching band indicated the formation of inclusion complex. Cyclohexane ring protons of the drugs show remarkable upfield or downfield shift in the ¹HNMR spectrum, indicating that the cyclohexane part of the guest molecule is entrapped inside CD cavities. SEM images of CIP/CD, SPA/CD, and OFL/CD complexes have a crystal structure with different morphology from the isolated CIP, SPA, OFL, and CDs. Investigations of the energetic, thermodynamic, and electronic properties of parametric model number 3 computational calculations confirmed the stability of the inclusion complex.     

Intramolecular charge transfer effects on 4-hydroxy-3-methoxybenzaldehyde

The absorption and fluorescence spectral characteristics of 4-hydroxy-3-methoxybenzaldehyde (HMB) have been studied in different solvents, pH and beta-cyclodextrin (beta-CD) and compared with 4-hydroxy-3,5-dimethoxybenzaldehyde (HDMB). The inclusion complex of HMB with beta-CD is analysed by UV-vis, fluorimetry, FT-IR, (1)H NMR, SEM and AM1 methods. In HMB, the normal emission (B band) is originates from a locally excited state and the longer emission (A band) is due to intramolecular charge transfer state (ICT). The OH group of HMB is present in the interior part of the beta-CD cavity and aldehyde group present in the upper part of the beta-CD cavity.     

Non-covalent DNA binding and cytotoxicity of certain mixed-ligand ruthenium(II) complexes of 2,2'-dipyridylamine and diimines

A series of mixed ligand ruthenium(II) complexes [Ru(Hdpa)2(diimine)](ClO4)2, 1-5 where Hdpa is 2,2'-dipyridylamine and diimine is 1,10-phenanthroline (phen) and a modified/extended 1,10-phenanthroline such as, 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), 5-methyldipyrido[3,2-d:2',3'-f]quinoxaline (mdpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) have been isolated and characterized by analytical and spectral methods. The complex [Ru(Hdpa)2(phen)](PF6)2 1 has been structurally characterized and the coordination geometry around Ru(II) in it is described as distorted octahedral. 1H NMR spectral data reveal that 1-5 should have a C2 symmetry lying on the diimine plane due to the rapid flapping of the coordinated Hdpa ligands. The interaction of the complexes with calf thymus (CT) DNA has been explored by using absorption and emission spectral and viscometry and electrochemical techniques and the mode of DNA binding of the complexes has been proposed. The DNA binding affinity of the complexes decreases with decrease in number of planar aromatic rings in the co-ligand supporting the intercalation of the diimine co-ligands in between the DNA base pairs. Circular dichroic spectral studies reveal that the complexes 3-5 exhibit induced circular dichroism upon binding to CT DNA. Interestingly, upon interaction with CT DNA all the complexes show an increase in anodic current in the cyclic voltammograms suggesting that they are involved in electrocatalytic guanine oxidation. Interestingly, of all the complexes, only 5 alters the DNA superhelicity upon binding with supercoiled pBR322 DNA, which is consistent with its higher DNA binding affinity. Further, the cytotoxicities of the complexes against human cervical epidermoid carcinoma cell line (ME180) have been examined. Interestingly, 5 exhibits a cytotoxicity against ME180 higher than other complexes with potency approximately 8 times more than cisplatin for 24 h incubation but 4 times lower than cisplatin for 48 h incubation.     

Solid‐phase microextraction for the human biomonitoring of environmental chemicals: Current applications and future perspectives

Sample preparation is one of the crucial steps in the analytical chemistry including human biomonitoring studies. Although there are several traditional approaches available, solid‐phase microextraction is emerged as one of the pioneering techniques due to its simplicity, rapidness, wide applicability, and miniaturization of traditional sample preparation (e.g., use of less or no organic solvents). There are few earlier review articles available on the advancements in solid‐phase microextraction and its use for the measurement of environmental chemicals in various types of environmental samples. However, a collective information on applicability and current usage of solid‐phase microextraction for the human biomonitoring of environmental chemicals are scarce, nonetheless, rising demands on innovative analytical approaches for human biomonitoring studies. Hence, in this review article, we covered the application of solid‐phase microextraction as extraction/purification methods for more than 15 classes of environmental chemicals to assess their respective exposure levels and associated health outcomes in various human population reported across the globe. Further, a detailed discussion on various types of matrix used, nature of coupled analytical instrumentations, and limitations and future perspectives of solid‐phase microextraction for human biomonitoring studies is presented in this review.     

Aminobenzohydrazide based colorimetric and ‘turn-on’ fluorescence chemosensor for selective recognition of fluoride

Chemosensors based on aminobenzohydrazide Schiff bases bearing pyrene/anthracene as fluorophores have been designed and synthesized for F⁻ ion recognition. The addition of fluoride ions to the receptors causes a dramatically observable colour change from pale yellow to brown/red. ¹H NMR studies confirm that the F⁻ ion facilitates its recognition by forming hydrogen bond with hydrogens of amide and amine groups. Moreover these sensors have also been successfully applied to detection of fluoride ion in commercial tooth paste solution.     

Green Chemical Synthesis of N-Cholyl-L-Cysteine Encapsulated Gold Nanoclusters for Fluorometric Detection of Mercury Ions

Herein we report a simple, single-step, cost-effective, environmentally friendly, and biocompatible approach using sodium salt of N-cholyl-L-cysteine (NaCysC) capped gold nanoclusters (AuNCs) with green emission properties at above the CMC in aqueous medium under UV-light irradiation. The primary and secondary CMC of NaCysC was found to be 4.6 and 10.7 mM respectively using pyrene as fluorescent probe. The synthesized AuNCs exhibit strong emission maxima at 520 nm upon excitation at 375 nm with a large Stokes shift of 145 nm. The surface functionality and morphology of NCs are studied by fourier transform infrared spectroscopy, dymanic light scattering studies and transmission electron microscopy. The formation of AuNCs was completed within 5 h and exhibit high stability for more than 6 months. The NaCysC templated AuNCs selectively quenches the Hg²⁺ ions with higher sensitivity in aqueous solution over the other metal ions. The fluorescence analysis of Hg²⁺ showed a wide linear range from 15 to 120 µM and a detection limit was found to be 15 nM.

     

TiO2 derived by titanate route from electrospun nanostructures for high-performance dye-sensitized solar cells

We report the use of highly porous, dense, and anisotropic TiO(2) derived from electrospun TiO(2)-SiO(2) nanostructures through titanate route in dye-sensitized solar cells. The titanate-derived TiO(2) of high surface areas exhibited superior photovoltaic parameters (efficiency > 7%) in comparison to the respective electrospun TiO(2) nanomaterials and commercially available P-25.     

Biological synthesis of silver and gold nanoparticles using apiin as reducing agent

We report a novel strategy for the biological synthesis of anisotropic gold and quasi-spherical silver nanoparticles by using apiin as the reducing and stabilizing agent. The size and shape of the nanoparticles can be controlled by varying the ratio of metal salts to apiin compound in the reaction medium. The resultant nanoparticles were characterized by UV-vis-NIR, transmission electron microscopy (TEM), FT-IR spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The interaction between nanoparticles with carbonyl group of apiin compound was confirmed by using FT-IR analysis. TEM photograph confirming the average size of the gold and silver nanoparticles were found to be at 21 and 39 nm. The NIR absorption of the gold nanotriangles is expected to be of application in hyperthermia of cancer cells and in IR-absorbing optical coatings.     

Synthesis of first ever 4-quinolone-3-carboxylic acid-appended spirooxindole-pyrrolidine derivatives and their biological applications

A series of 4-quinolone-3-carboxylic acid-containing spirooxindole-pyrrolidine derivatives was synthesized via multicomponent 1,3-dipolar cycloaddition reactions of azomethine ylides with new (E)-4-oxo-6-(3-phenyl-acryloyl)-1,4-dihydroquinoline-3-carboxylic acids in good yields with high regioselectivity. The cycloadducts were characterized by analytical and spectral data including \(^{1}\hbox {H}\), \(^{13}\hbox {C}\), 2D NMR and mass spectroscopy. The structure of one of the compounds (8a) was investigated theoretically by computational techniques. DFT studies support the proposed mechanism for this cycloaddition reaction. Furthermore, antibacterial activities of the new compounds were evaluated against Gram-positive and Gram-negative bacterial strains. Compounds 8f, 8m and 8p showed potent inhibition activities against selected bacteria. The in vitro cytotoxicity of spirooxindole derivatives (8a–r) was evaluated against MCF-7 breast cancer cell line. Among the various compounds tested, compound 8f \((\hbox {IC}_{50} = 18.35~\upmu \hbox {M})\) showed significant cytotoxic activity compared to the standard drug doxorubicin \((\hbox {IC}_{50 }= 15.00~\upmu \hbox {M})\).     

Excimer Emission in Norepinephrine and Epinephrine Drugs with α- and β-Cyclodextrins: Spectral and Molecular Modeling Studies

The inclusion complexation behavior of norepinephrine (NORE) and epinephrine (EPIN) with native cyclodextrins (α-CD and β-CD) were investigated by UV-visible, fluorimetry, time-resolved fluorescence, SEM, TEM, FT-IR, ¹H NMR, DSC, powder XRD and PM3 methods. Single emission was observed in aqueous solution where as dual emission (excimer) noticed in the CD solutions. Both drugs form 1:1 drug-CD complexes in lower CD concentrations and 1:2 CD-drug₂ complexes in the higher CD concentrations. Time-resolved fluorescence studies indicated that both drugs showed single exponential decay in water and biexponential decay in CD. Nano-sized self-aggregated particles of drug-CD were found by TEM studies. Molecular modeling studies indicated that aliphatic chain part of the drug was entrapped in the CD cavity. Thermodynamic parameters and binding affinity of complex formation of the CD were determined according to PM3 method. The PM3 results were in good agreement with the experimental results.