A Novel Poly(cytosine)-Based Electrochemical Biosensor for Sensitive and Selective Determination of Guanine in Biological Samples.

The novel poly(cytosine)-modified glassy carbon electrode-based electrochemical sensor was fabricated potentiodynamically for the detection of Guanine (G) in clinical and biological samples. The surface of the electrode was successfully activated by electropolymerization, and about a 7.5-fold current improvement due to modification was achieved. From the analysis of the dependence of peak current and peak potential on a scan rate, a higher R 2 for the peak current on the square root of scan rate (R 2 = 0.999) than the dependence of peak current on scan rate (R 2 = 0.982) indicated that the oxidation of G at poly(cytosine)/GCE was predominantly diffusion controlled. The oxidative peak response of the electrode revealed a high linear range of G concentration (0.1-200 µM) under optimized conditions. The detection limit and limit of quantification were 6.10 and 20.13 nM, respectively, associated with the %RSD of under 1%. The validation of the developed electrochemical sensor for the determination of G was investigated by analyzing human urine DNA and serum samples with spike recovery results in the range of 98.20-103.70% with the interferent recovery percentage in the range of 97.86-103.10% containing 50-300% of potential interferents. The newly designed sensor demonstrated the highest level of performance for the G detection in real samples.

Characterization and Application of a Synthesized Novel Poly(chlorobis(1,10-phenanthroline)resorcinolcobalt(II) chloride)-Modified Glassy Carbon Electrode for Selective Voltammetric Determination of Cefadroxil in Pharmaceutical Formulations, Human Urine, and Blood Serum Samples.

Cefadroxil belongs to the ß-lactam antibiotics, mainly used for the treatment of various bacterial infections, caused by Gram-positive and Gram-negative bacteria. However, it is also encountering serious bacterial resistance, necessitating continuous monitoring of its level in pharmaceutical and biological samples. This study presents a selective, accurate, and precise square-wave voltammetric method based on a novel poly(chlorobis(1,10-phenanthroline)resorcinolcobalt(II)chloride)-modified glassy carbon electrode (poly(CP2RCoC)/GCE) for determination of cefadroxil (CDL). UV-vis spectroscopy, FT-IR spectroscopy, metal and halide estimation, CHN elemental analysis, and electrolytic conductivity measurement results confirmed the synthesis of the title complex modifier. Electrode characterization results revealed modification of the surface of the electrode by an electroactive and a conductive polymer film (poly(CP2RCoC)/GCE), leading to an improved effective electrode surface area. In contrast to the bare electrode, the appearance of an irreversible oxidative peak at a much reduced potential with a 7-fold current enhancement at poly(CP2RCoC)/GCE showed the catalytic effect of the modifier toward oxidation of CDL. The square-wave voltammetric current response of poly(CP2RCoC)/GCE showed a linear dependence on the concentration of CDL in the range of 1 × 10-7-3.0 × 10-4 M with a detection limit of 4.3 × 10-9. The CDL level in the selected two tablet brands was in the range of 97.25-100.00% of their labeled values. The spike recovery results in tablet, human blood serum, and urine samples were 98.85-101.30, 99.20-100.39, and 98.10-99.99%, respectively. Interference recovery results with a less than 4.74% error, lower LoD, and wider dynamic range than the previously reported methods validated the potential applicability of the present method with excellent accuracy and sensitivity based on the novel mixed-ligand complex-modified GCE (poly(CP2RCoC)/GCE) for determination of CDL in various real samples with a complex matrix.

Electrochemical Determination of Chloroquine Phosphate in Real Samples Using a Diresorcinate-1,10-phenanthrolinecobalt(II)-Modified Glassy Carbon Electrode.

Chloroquine phosphate (CQP) is used for malaria treatment. As it is facing increasing resistance, it needs continuous monitoring using sensitive and specific detection methods. In this work, a voltammetric sensor was prepared by electropolymerization of a diresorcinate-1,10-phenanthrolinecobalt(II) complex on a glassy carbon electrode (poly(DHRPCo)/GCE) which was followingly characterized. Compared with a bare GCE, CQP showed single well shaped irreversible oxidative peak at the poly(DHRPCo)/GCE. The peak current showed excellent linearity with CQP concentration in the range of 0.005-300.0 µm with a detection limit of 0.39 nm. The response of CQP at poly(DHRPCo)/GCE was not influenced by the presence of amoxicillin, ciprofloxacillin and paracetamol in addition to its high stability and reproducibility. It was applied for detection of CQP in various real samples, including three brands of tablets, human blood serum, and urine samples. The detected amount in tablets were in the range 98.4-103.2 % of their labeled value. Spike recovery results in human blood serum, urine, and tablet samples were 99.35-100.28 %, 99.03-100.32 %, and 98.40-100.41 %, respectively. Interference recovery results with less than 4.60 % error, the lower limit of detection and the wider dynamic range than most of the previously reported methods validate the potential applicability of the proposed method for CQP determination in various real samples with complex matrices.

Synthesis, structural investigations, and in vitro biological activity of Co(II) and Fe(III) mixed ligand complexes of 1,10-phenanthroline and 2,2'-bipyridine.

Herein, we report, four new mixed ligand complexes of Cobalt(II) and Iron(III), viz., [Co(L1 )(L2 )(H2 O)2 ]Cl2 (1), [Co(L1 )(L2 )(L3 )(H2 O)]Cl2 (2), [Fe(L1 )(L2 )(H2 O)2 ]Cl3 (3), and [Fe(L1 )(L2 )(L3 )(H2 O)]Cl3 (4), where L1  = 1,10-phenanthroline (C12 H8 N2 ), L2  = 2,2'-bipyridine (C10 H8 N2 ), and L3  = acetamide (C2 H5 NO)). They were synthesized and characterized using spectroscopic analysis (ESI-MS, ICP-OES, FT-IR, and UV-Vis), elemental analysis, melting point determination, and conductance measurement. The in vitro antibacterial activity was tested on two Gram-positive Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) and two Gram-negative Escherichia coli (E. Coli)and Klebsiella pneumoniae (K. pneumoniae) bacteria using the disc diffusion method. Based on the analytical and spectroscopic data, octahedral geometries are assigned to the complexes. Co(II) complexes were found more active against K. pneumoniae than the corresponding Fe(III) complexes which indicated that antibacterial activities of metal complexes have tuned with the nature of the metal. The results provide an insight to design and readily prepare task-specific metal-based drugs for interaction with particular bacterial strains.

Synthesis of a novel diaquabis(1,10-phenanthroline)copper(II)chloride complex and its voltammetric application for detection of amoxicillin in pharmaceutical and biological samples.

A one step facile synthesis of the novel diaquabis(1,10-phenanthroline)copper(II)chloride (A2P2CuC) complex is demonstrated. Cyclic voltammetric and electrochemical impedance spectroscopic results revealed potentiodynamic deposition of a conductive electroactive poly(A2P2CuC) film on the glassy carbon electrode surface increasing its effective surface area. In contrast to the unmodified glassy carbon electrode, appearance of an oxidative peak at a reduced potential with over two fold current for amoxicillin at poly(A2P2CuC)/GCE demonstrated its electrocatalytic property attributed to reduce charge transfer resistance and the improved surface area of the electrode surface. Better correlation of the oxidative peak current with square root of scan rate (R2 = 0.99779) than with scan rate (R2 = 0.96953) supplemented by slope of 0.58 for log(current) versus log(scan rate) confirmed diffusion controlled irreversible oxidation of amoxicillin. At optimized solution and SWV parameters, current response of poly(A2P2CuC)/GCE showed linear dependence on concentration of amoxicillin (2.0-100.0 µM) with LoD 0.0115 µM. While no amoxicillin was detected in the human blood serum sample, an amount 89.40-100.55% of the nominal level was detected in the analyzed eight tablet brands. Spike recovery in tablet samples (98.90-101.95%) and blood serum sample (102.20-101.37%); interference with an error (%RSD) of 0.00-4.51% in tablet and 0.00-2.10% in serum samples; excellent stability and reproducible results, added with the wide dynamic range and low LoD validated the method for amoxicillin determination in pharmaceutical formulations and human urine samples.

Potentiodynamic Poly(resorcinol)-Modified Glassy Carbon Electrode as a Voltammetric Sensor for Determining Cephalexin and Cefadroxil Simultaneously in Pharmaceutical Formulation and Biological Fluid Samples.

This study covers the development of a fast, selective, sensitive, and stable method for the simultaneous determination of cephalosporins (cephalexin (CLN) and cefadroxil (CFL)) in biological fluids and tablet samples using potentiodynamic fabrication of a poly(resorcinol)-modified glassy carbon electrode (poly(reso)/GCE). The results of cyclic voltammetry and electrochemical impedance spectroscopy supported the modification of the GCE by a polymer layer that raised the electrode surface area and conductivity. At the poly(reso)/GCE, an irreversible oxidative peak with four- and fivefold current enhancement for CLN and CFL, respectively, at a substantially lower potential demonstrated the catalytic action of the modifier. Under optimized solution and parameters, the peak current response at the poly(reso)/GCE revealed a linear dependence on the concentration of CLN and CFL within the range 0.1-300 and 0.5-300 µM, respectively, with a limit of detection (LoD) of 3.12 and 8.7 nM, respectively. The levels of CLN in four selected tablet brands and CFL in two tablet brands were in the vicinity of 91.00-103.65% and 97.7-98.83%, respectively, of their nominal values. The recovery results for CLN in pharmaceutical samples were in the range of 99.00-100.67% and for CFL 97.9-99.75% and for blood serum and urine samples 99.55-100.55% and 99.33-100.34% for CLN and 97.13-100.60% and 96.73-102.50% for CFL, respectively. Interference recovery results with errors less than 4.81%, lower LoD, wider dynamic range, excellent recovery results, and good stability of the modifier compared to those for the previously reported methods validated the use of the poly(reso)/GCE for determining CLN and CFL simultaneously in various real samples.

Rapid and simultaneous determination of trigonelline, caffeine, and chlorogenic acid in green coffee bean extract.

A simple, inexpensive, and rapid method for simultaneous determination of trigonelline, caffeine, and chlorogenic acid from green coffee bean extract was proposed based on salting-out assisted liquid-liquid extraction, using QuEChERS salt and acetonitrile followed by UV-Vis analysis. The proposed method represents acceptable linearity for trigonelline (0.9978), caffeine (0.9995), and chlorogenic acid (0.9996) with excellent correlation (0.93 and 0.83) for trigonelline and caffeine, respectively, when compared to RP-HPLC-DAD. The proposed method could be used in coffee industries for quality control and geographical origin traceability studies of green coffee samples.

Nonfunctionalized Cation of an Ionic Liquid as a Ligand in the Synthesis of a New Coordination Compound and Assessment of Its Biological Activity.

Literature evidences reveal the affinity of ionic liquids for biomembranes that they are readily absorbed into the cell, resulting in a variety of biological effects, including broad antibacterial potential and anticancer activity. Recent research directions considered the ions of this class of compounds as a new choice of ligands in the synthesis of transition metal complexes for various applications. Based on this, the present work reports the synthesis, structural characterization, and in vitro antibacterial activities of a tetrahedral hexacationic Co(II) complex formed by coordinating with the cation of an ionic liquid, N-butyl-4,4-bipyridinium bis(trifluoromethylsulfonyl)amide ([C4Bip][Tf2N]). It has been demonstrated by the isolation and characterization of tetrakis-(N-butyl-4,4'-bipyridinium)cobalt(II)dichloride-tetrakis-(bis(trifluoromethylsulfonyl)amide, ([(C4Bip)4Co]Cl2(Tf2N)4). The ligand and complex are characterized spectroscopically (1H, 13C, and 19F NMR, ESI MS, ICP OES), and by CHNS elemental analysis, halide estimation, and conductivity studies. The antibacterial activities of the compounds against two bacteria, Klebsiella pneumoniae (K. pneumoniae) and Staphylococcus aureus (S. aureus), are screened using the agar well-diffusion method and were compared with a reference (gentamicin). The metal complex demonstrated better inhibition than the ionic liquid and the reference.

Synthesis of N-Tetradecyl-1,10-phenathrolinium-Based New Salts for Biological Applications.

New organic salts were synthesized by quaternizing 1,10-phenanthroline using 1-bromotetradecane. The first step yielded an organic salt of formula [C26H37N2]Br. Anion exchange reaction using Li[(CF3SO2)2N] resulted in a more stable salt of formula [C26H37N2][(CF3SO2)2N]. The organic salts were investigated by spectrometry (1H, 13C, 19F NMR, X-ray photoelectron spectroscopy (XPS), UV-Vis, and matrix-assisted laser desorption/ionization mass spectroscopy (MALDI MS), CHNSBr elemental analysis, and thermal analysis (TGA and DSC). The thermal characterization showed the melting and decomposition points of [C26H37N2][(CF3SO2)2N] to be 48°C and 290°C, respectively, which indicates it is an ionic liquid with large liquidus range. The biological activities of the salts were investigated against two Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and two Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria, and they are found to be active against all of them. They were compared with [Cu(1,10-phenanthroline)2Cl]Cl. They are found more active against the Gram-negative bacteria. The salts demonstrated minimum inhibitory concentration as low as 50 µg/L. These results suggest the synthesized salts can be considered as a better alternative to certain transition metal complex drugs. This minimizes the concern of introducing metal ions into the organism.

Synthesis and Assessment of Antibacterial Activities of Ruthenium(III) Mixed Ligand Complexes Containing 1,10-Phenanthroline and Guanide.

In this work, two complexes of ruthenium(III) ([Ru(phen)2Cl2]Cl·2H2O and [Ru(phen)2(G)Cl]2Cl·H2O) were synthesized from 1,10-phenanthroline alone as well as from both 1,10-phenanthroline and guanide. The synthesis was checked using halide test, conductance measurement, and spectroscopic (ICP-OES, FTIR, and UV/Vis) analysis. Their in vitro antibacterial activities were also investigated on two Gram-positive (Staphylococcus aureus (S. aureus) and methicillin resistant Staphylococcus aureus (MRSA)) and two Gram-negative (Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae)) bacteria. These complexes showed wide-range better activities than the commercially available controls (Chloramphenicol and Ciprofloxacin) against even the most drug resistant K. pneumoniae. [Ru(phen)2(G)Cl]2Cl·H2O inhibited S. aureus, MRSA, E. coli, and K. pneumoniae by 17.5%, 27.4%, 16%, and 52%, respectively, better than Chloramphenicol. It also inhibited these pathogens by 5.9%, 5.1%, 2.3%, and 17.2%, respectively, better than Ciprofloxacin. Similarly, [Ru(Phen)2(Cl)2]Cl·2H2O inhibited these pathogens by 11%, 8.7%, 0.1%, and 31.2%, respectively, better than Chloramphenicol. Therefore, after in vivo cytotoxicity investigations, these compounds can be considered as potential antibiotic drugs.