Simultaneous Chemo/Enantioseparation and Assay of R-(+)-Rabeprazole and Related Impurities in Pharmaceutical Formulations

Simultaneous chiral and chemoseparation of R-(+)-rabeprazole and related (enantio)impurities was achieved on a cellulose tris-(3,5-dichlorophenylcarbamate) stationary phase chemically bonded to silica gel (Chiralpak IC). A gradient elution was applied in the reverse-phase separation mode. The mobile phase consisted of a mixture of acetonitrile and aqueous phosphate buffer at pH 7. The other operational parameters were flow rate of 1 mL min⁻¹, column temperature of 35 °C and ultraviolet (UV) detection at 282 nm. Quantification limits for R-(+)-rabeprazole and the related impurities ranged in the interval of 0.02–0.03 %. Linear response intervals of 0.02–0.66 % were obtained with UV detection. Validation of the proposed method was achieved according to current regulations in force. For better understanding of the R-(+)-rabeprazole impurity profile, (+)-EMS/MS and MS/MS detection were also used.

     

Bioreducible hyperbranched polyglycerols with disulfide linkages: Synthesis and biocompatibility evaluation

In this article, we describe the development of multifunctional, water‐soluble hyperbranched polyglycerols containing redox‐sensitive disulfide linkages as a new class of biodegradable polymers. The polymers were synthesized by the anionic ring opening multibranching (co)polymerization of glycidol with an epoxide monomer bearing disulfide groups, 2‐((2‐oxiran‐2‐ylmethoxy)ethyl)disulfanyl) ethan‐1‐ol. Polymerizations were optimized at 65 °C unlike the homopolymerization of glycidol. Both low (5–10 kDa) and high (100 kDa) molecular weight polymers were synthesized in a controlled manner with low polydispersity. The polymers underwent degradation in presence of reducing agents such as tris(2‐carboxyethyl)phosphine, dithiothreitol, and glutathione resulting in low molecular weight fragments with thiol groups. Blood compatibility analysis using coagulation, platelet activation, complement activation and red blood cell lysis assays as well as cell toxicity analysis using MTS assay revealed the excellent biocompatibility of these newly synthesized polymer architectures. All these features make these polymers suitable for intracellular delivery of therapeutic molecules. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2104–2115     

Investigation of leaching of an antifouling agent from marine paint formulations using radiotracer technique

A radiotracer technique was used to investigate the leaching of an antifouling agent from different marine paint formulations with an objective to select the best paint formulation for bulk production. The antifouling agent (Diuron) itself was labeled with carbon-14 (half-life: 5,730?years, ??-energy: 156?keV) and used as a radiotracer. The different paint formulations added with radiolabeled Diuron were applied onto suitably selected substrates and measured for initial intensity of ??-radiation using a Geiger-Muller detector connected to a ratemeter. The painted substrates were subjected to shower tests for a pre-decided time and subsequently measured for ??-radiations. The comparison of intensity of ??-radiations in substrates prior and post shower tests provides information about leaching of antifouling agent Diuron from the paint formulation. The high leaching percentage of antifouling agent Diuron post shower tests indicates non-suitability of paint formulation for marine and civil structures. However, low leaching rate of Diuron will make a paint formulation more efficient and suitable. Based on the results of investigation, a paint formulation with minimum leaching rate was identified and selected for bulk production by a paint company.     

Photoacoustic studies on optical and thermal properties of p‐type and n‐type nanostructured porous silicon for (100) and (111) orientations

Nanostructured p‐type and n‐type porous silicon samples were prepared for (100) and (111) orientations and a systematic study is carried out on the effects of orientations, dopant type (boron and phosphorous), current density (20 and 30mA/cm²) and etching time on the formation, optical and thermal properties by photoacoustic spectroscopy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Performance evaluation of indigenous amperometers for the determination of uranium

The performance evaluation studies of three indigenously manufactured amperometers were carried out for uranium determination in U₃O₈ standard solution. Three analysts independently carried out ten determinations each of uranium by Biamperometric end point detection method with each of these amperometers. Two-way ANOVA test was performed on the data using MATLAB-7.0 software to test whether the variation in the observed data is statistically significant. No significant bias in the data produced by three analysts with three independent instruments was observed. The results obtained show that the indigenous amperometers are suitable for uranium determination in fuel materials and for nuclear material accounting, with high precision and accuracy.     

Probing the association behavior of poly(ethylene glycol)-based amphiphilic comb-like polymer in NaCl solution

The effect of salt on the associative behavior of intramolecular aggregates obtained from poly(ethylene glycol)-based amphiphilic comb-like polymers in aqueous medium at pH 6.2 has been investigated by surface tension, fluorescence probe, dynamic light-scattering, and viscometry techniques. Results reveal that the addition of salt screens the electrostatic repulsion between the charges along the polymer backbone in the aggregates and consequently (1) reduces the surface activity at the air/water interface, (2) leads to the contraction of the polymer backbone, and (3) reduces the hydrodynamic sizes of the aggregates. In contrast, the hydrophobicity of the aggregates remains unperturbed.     

Properties of ZnSe films pulse electrodeposited in the presence of phosphotungstic acid

ZnSe films were pulse-electrodeposited on conducting glass substrates with and without the addition of phosphotungstic acid. X-ray diffraction studies indicated the formation of single phase cubic ZnSe. Addition of phosphotungstic acid resulted in films with nanocrystallites. The band gap of the films was found to increase due to addition of phosphotungstic acid. The films had a crystallite size of the order of 15nm and a surface roughness of 1.8nm. Laser Raman studies exhibited the LO phonon peaks of ZnSe. The films were found to possess a slight excess of Se as evident from the energy dispersive X-ray analysis measurements.     

Grafted Polymeric Microspheres: A Synthetic Approach to Structurally Well-Defined Brush Polymers

Abstract

A simple method for the surface grafting of crosslinked polystyrene latex particles of narrow size distribution as core is described. Amino groups were generated on the surface of these microspheres by a two-step process of nitration and subsequent reduction. Polyethylene glycol chain of desired molecular weight was covalently linked to the surface amino group using diiso-cyanate-coupling reaction. The method is appropriate for designing brush polymers.

     

Self-assembled monothiol-terminated hyperbranched polyglycerols on a gold surface: a comparative study on the structure, morphology, and protein adsorption characteristics with linear poly(ethylene glycol)s

Monothiol-terminated hyperbranched polyglycerols (HPGs) were synthesized by ring-opening polymerization of glycidol from partially deprotonated 2,2'-dihydroxyethane disulfide as the initiator and subsequent reduction of the disulfide group. Two molecular weights of HPG thiols were synthesized. The molecular weights of the polymers were determined by MALDI-TOF analysis, and the presence of thiol was verified by Ellman's assay. The self-assembly of HPG thiols on gold was studied and compared with that of linear poly(ethylene glycol) (PEG) thiols utilizing various surface analysis techniques. Monothiol-functionalized HPGs readily adsorbed to a gold surface and formed highly uniform thin films on the surface. The graft density of the HPG layer decreased with an increase in the molecular weight of the polymer. The amount of polymer on the surface increased with increasing incubation concentration and saturated above 6 g/L polymer concentration. Generally, HPG thiols gave lower graft density compared to linear PEG thiols of similar molecular weight. AFM morphological studies showed that HPG thiols form more uniform and smooth surface films compared to PEG thiols. Incubation of a polymer-coated surface (HPG thiols and PEG thiols) with bovine serum albumin and immunoglobulin showed that the high molecular weight hyperbranched polyglycerol was more resistant to protein adsorption than linear PEG of similar molecular weight or lower molecular weight HPG. The protein adsorption decreased with increasing graft density of the HPG chains on the surface. Our results show that HPG could be a good alternative to PEG in the development of nonfouling functional surfaces.