B. S. Sherigara

Synthesis and characterization of chitosan-based pH-sensitive semi-interpenetrating network microspheres for controlled release of diclofenac sodium

pH-Sensitive semi-interpenetrating networks (IPNs) based on chitosan (Cs) and acrylamide-grafted hydroxyethylcellulose (AAm-g-HEC) were prepared in the form of microspheres (MPs) by emulsion-crosslinking technique using glutaraldehyde (GA) as a crosslinker. Diclofenac sodium (DS) drug was successfully encapsulated into IPN microspheres by varying the ratio of Cs and AAm-g-HEC, % drug loading, and amount of GA. DS encapsulation of up to 83% was obtained as measured by UV spectroscopy. MPs with average particle sizes in the range of 188-310microm were obtained. MPs were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Differential scanning calorimetry (DSC). Diffusion coefficients (D) of water transport through the microspheres were determined using an empirical equation. In vitro release of DS from these matrices has been investigated in pH 1.2 and 7.4 media.

Electropolymerisation of l-arginine at carbon paste electrode and its application to the detection of dopamine, ascorbic and uric acid

L-arginine was electropolymerised on a carbon paste electrode (CPE) to form the biopolymer by free radical formation in the electro oxidation process of the amino and carboxylic group containing compound by cyclic voltammetric technique. The modified electrode shows an excellent electrocatalytic activity towards the oxidation of both dopamine (DA) and ascorbic acid (AA). It was demonstrated that the deposited biopolymer has positive charges over the bare carbon electrode surface, which leads to the formation of electrical double layer made the fast electron transfer process could leads to the diffusion of dopamine, ascorbic acid and uric acid on their charge gradient by cyclic voltammetric technique. The response of the sensor was tested towards the different dopamine concentration. The catalytic peak current obtained was linearly related to DA concentrations in the ranges of 5×10(-5) to 1×10(-4)M L(-1) with correlation co-efficient of 0.9924 which reveals the adsorption controlled process. The detection limit for dopamine was 5×10(-7)M L(-1). The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid (AA) and response is fast stable, reliable, resistant to biofouling and can be applied for the real sample analysis in medical, pharmaceutical and biotechnological sectors. The adsorption-controlled process and kinetic parameters of the poly(L-arginine) were determined using electrochemical approaches.

Multi-walled carbon nanotube/poly(glycine) modified carbon paste electrode for the determination of dopamine in biological fluids and pharmaceuticals.

A modified carbon paste electrode (CPE) for the selective detection of dopamine (DA) in presence of large excess of ascorbic acid (AA) and uric acid (UA) at physiological pH has been fabricated by bulk modification of CPE with multi-walled carbon nanotubes (MWCNTs) followed by electropolymerization of glycine (Gly). The surface morphology is compared using SEM images. The presence of nitrogen was confirmed by the energy dispersion X-ray spectroscopy (EDS) indicating the polymerization of Gly on the surface of the modified electrode. The impedance study indicates a better charge transfer kinetics for DA at CPE modified with MWCNT/polyglycine electrode. The presence of MWCNTs in carbon paste matrix triggers the extent of electropolymerization of Gly and imparts more selectivity towards DA by electrochemically not sensing AA below a concentration of 3.1×10(-4)M. Due to the exclusion of the signal for AA, the interference of AA in the determination of DA is totally ruled out by DPV method which is used for its detection at lower concentrations. Large peak separation, good sensitivity, reproducibility and stability allow this modified electrode to analyze DA individually and simultaneously along with AA and UA. Detection limit of DA was determined from differential pulse voltammetric (DPV) study and found to be 1.2×10(-8)M with a linear dynamic range of 5.0×10(-7)M to 4.0×10(-5)M. The practical analytical application of this electrode was demonstrated by measurement of DA content in dopamine hydrochloride injection and human blood serum.

Semi-interpenetrating network of acrylamide-grafted-sodium alginate microspheres for controlled release of diclofenac sodium, preparation and characterization

The semi-interpenetrating networks (semi-IPNs) of acrylamide grafted sodium alginate (AAm-g-NaAlg) microspheres (MPs) were prepared by emulsion-crosslinking method using glutaraldehyde (GA) as a crosslinking agent. The grafting of acrylamide onto sodium alginate was prepared by free-radical graft polymerization using ceric ammonium nitrate (CAN) as initiator at three acrylamide concentrations with monomer to polymer ratio of 1:1, 2:1 and 3:1, respectively. The grafting efficiency was found to be 91%. The produced MPs are almost spherical in nature with smooth surfaces. Diclofenac sodium (DS), an anti-inflammatory drug was successfully encapsulated into the MPs. The encapsulation efficiency was found to vary between 83% and 95%. The MPs were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The diffusion coefficient (D) was dependent upon the amount of crosslinking agent (GA) and amount of grafting ratio in the matrix. The rate of release was found to be dependent on the amount of GA, AAm:NaAlg grafting ratio and % drug loading in the MPs. The release data have been fitted to an empirical equation to investigate the diffusional exponent (n), which indicated that the release mechanism from MPs follows the super Case II transport.

Efficient and Straightforward Synthesis of Tetrahydrocarbazoles and 2,3-Dimethyl Indoles Catalyzed by CAN

Abstract A simple protocol was established to synthesize 2,3-dialkyl indoles and various tetrahydrocarbazoles via Fischer indole synthesis. This method uses ceric ammonium nitrate as a catalyst for the Fischer indole synthesis with substituted phenyl hydrazine hydrochlorides and 2-butanone, phenyl propanal, and cyclohexanone. This process is a practical synthetic method for the preparation of various 2,3-disubstituted alkyl indoles and tetrahydrocarbazoles.

Microwave induced synthesis of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters and their antibacterial activity

A series of thieno[2,3-b]quinoline-2-carboxylic acids and alkyl esters, (3a–i) have been synthesized by the condensation of 2-chloro-3-formyl quinolines (1a–c) with thioglycolic acid/alkyl esters under microwave irradiation using anhydrous potassium carbonate. These compounds were characterized by elemental analysis, IR, 1H NMR, and mass spectral studies. Their antibacterial activity was also evaluated.

Microwave Induced One-Pot Synthesis of Some New Thiopyrano[2,3-b]quinolin-2-ones under Solvent-Free Conditions

A series of some new thiopyrano[2,3-b]quinolin-2-one 2a-i have been synthesized by the one pot reaction between 2-mercaptoquinoline-3-carbaldehyde 1a-i and phenoxyacetic acid using TEA catalyst under microwave irradiation in solvent free conditions. The procedure is simple, environmentally benign and occurs in good yields. All the newly synthesized compounds were characterized by elemental analyses, IR, 1H NMR and mass spectral data.

Mild and Simple Access to Diverse 4-Amino-substituted 2-Phenyl-1,2,3,4-tetrahydroquinolines and 2-Phenylquinolines Based on a Multicomponent Imino Diels–Alder Reaction

A straightforward synthesis of new 1-(2-phenyl-1,2,3,4-tetrahydroquinolin-4-yl) pyrrolidin-2-ones/azepan-2-one from N-vinyl caprolactam/N-vinylpyrrolidin-2-one and N-benzylideneaniline via the imino Diels–Alder reaction has been reported for the first time. Antimony(III) chloride has been shown to effectively catalyze imino-Diels–Alder reaction to afford both 2-phenylquinoline and 2-phenyl-1,2,3,4-tetrahydroquinolin derivatives in excellent yields at ambient temperature. The cis diastereoselectivity to give cis 2-phenyl-1,2,3,4-tetrahydroquinolines is also highlighted in this reaction.

Poly (Naphthol Green B) film based sensor for resolution of dopamine in the presence of uric acid: A voltammetric study

A polymer film of Naphthol Green B was prepared on the surface of a graphite pencil electrode using cyclic voltammetry. This poly(Naphthol Green B) coated electrode exhibits an excellent electroanalytical activity towards the determination of dopamine and uric acid. The voltammogram obtained for dopamine at the modified electrode was reversible. The effect of concentration and also pH were investigated. The peak current and peak potential were recorded in a 0.2 M phosphate buffer solution of pH 7.0. The modified electrode shows the ability to detect the dopamine and uric acid separately. The interference study was done using differential pulse voltammetry. The modified electrode was also used for the detection of dopamine in injections.

Spectral characterisation and electrochemical investigation of some divalent transition metal complexes of di(4-fluorophenyl)carbazone

Abstract The complexes of Co(II), Ni(II), Cu(II), Cd(II) and Pd(II) with di(4-fluorophenyl)carbazone (D4FPC) have been synthesised and characterised by elemental analyses, magnetic moment measurements, IR, 1 H NMR, UV–vis, and EPR spectral studies. The results show that D4FPC behaves as a bidentate monoanionic ligand coordinating through O and N donor atoms and forms 1:2 (metal–ligand) stoichiometry. The electrochemical reduction of Cu(II) complex has been studied on a glassy carbon electrode in non aqueous media using tetrabutylammonium perchlorate (Bu 4 NClO 4 ) as a supporting electrolyte. The redox properties are discussed from the voltammetric measurements.