Application of microcrystalline cellulose as an efficient and cheap sorbent for the extraction of metoprolol from plasma and wastewater before HPLC–MS/MS determination

A dispersive solid-phase extraction method based on a new sorbent has been performed on plasma and wastewater samples to determine metoprolol by high-performance liquid chromatography–tandem mass spectrometry. In this study, the analyte was adsorbed from the samples onto microcrystalline cellulose as a green and efficient sorbent and then eluted for use in the determination step. In the mass spectrometer, the analyte was detected in the positive mode and selectivity of the analysis was increased by sequential mass analysis through multiple reaction monitoring. All of the effective parameters in the extraction of metoprolol from plasma and wastewater were optimized. Under optimal conditions the method was linear in the ranges of 1–1,000 and 0.1–1,000 ng/ml in plasma and wastewater samples, respectively. The detection limits of the method were 0.30 and 0.03 ng/ml in plasma and wastewater samples, respectively. The data showed that the method provides low detection limit, wide linear range, good precision and high extraction recovery. Finally several plasma and wastewater samples were successfully analyzed using the method. The use of a small amount of a green and inexpensive sorbent and a low volume of plasma without the need for further pretreatment steps are the main advantages of the method.     

Binary teaching-learning-based optimization algorithm is used to investigate the superscattering plasmonic nanodisk

A new efficient binary optimization method based on Teaching-Learning-Based Optimization (TLBO) algorithm is proposed to design an array of plasmonic nanodisks in order to achieve maximum scattering coefficient spectrum. In binary TLBO (BTLBO), a group of learner consists of a matrix with binary entries; control the presence (‘1’) or the absence (‘0’) of nanodisks in the array. Simulation results show that scattering coefficient strongly depends on the localized position of nanoparticles and non-periodic structures have more appropriate response in term of scattering coefficient. This approach can be useful in optical applications such as plasmonic nanoantennas.     

Surface modification of cellulose nanocrystal with chitosan oligosaccharide for drug delivery applications

A novel drug delivery system based on two of the most abundant natural biopolymers was developed by modifying the surface of oxidized cellulose nanocrystal (CNC) with chitosan oligosaccharide (CS_OS). First, the primary alcohol moieties of CNC were selectively oxidized to carboxyl groups using the 2,2,6,6-tetramethylpiperidine-1-oxyl radical catalyst. The amino groups of CS_OS were then reacted with carboxylic acid groups on oxidized CNC (CNC-OX) via the carbodiimide reaction using N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide as coupling agents. Successful grafting of CS_OS to CNC-OX was confirmed by infrared spectroscopy, thermogravimetry, potentiometric titration, and zeta potential measurements. The grafting resulted in a conversion of ~90 % carboxyl groups on CNC-OX and the degree of substitution was 0.26. CNC–CS_OS nanoparticles showed a binding efficiency of 21.5 % and a drug loading of 14 % w/w. A drug selective electrode was used to directly measure the concentration of procaine hydrochloride released from CNC–CS_OS particles. The in vitro drug release was studied at pH 8 and the nanoparticles revealed a fast release of up to 1 h, which can be used as biocompatible and biodegradable drug carriers for transdermal delivery applications.     

Riboflavin as a green sorbent in dispersive micro-solid-phase extraction of several pesticides from fruit juices combined with dispersive liquid–liquid microextraction

A vortex-assisted dispersive micro-solid-phase extraction procedure using a new and green sorbent was developed as a simple, fast, and efficient sample preparation method for the extracting five pesticides in several fruit juice samples. In this study, for the first time, riboflavin was used as an efficient sorbent. A few milligrams of riboflavin was directly added into the aqueous solution containing the analytes to adsorb them. After adsorption the analytes, they were desorbed and more concentrated by a dispersive liquid–liquid microextraction procedure. The influence of several effective parameters such as amount of riboflavin, pH, vortex time, eluent nature and volume, and extraction solvent type and volume on the extraction efficiency was investigated. In optimal conditions, linear ranges of the calibration curves were broad. The limits of detection and quantification were attained in the ranges of 0.56–1.5  and 1.9–0.52 ng mL⁻¹, respectively. The proposed method demonstrated to be suitable for concurrent extraction of the studied pesticides in various fruit juice samples with high enrichment factors (320–360) and precision (relative standard deviation ≤7.8% for intra- [n = 6] and interday [n = 4] precisions at a concentration of 25 ng mL⁻¹ of each pesticide).     

Time-dependent discrete road network design with both tactical and strategic decisions

This paper aims to model and investigate the discrete urban road network design problem, using a multi-objective time-dependent decision-making approach. Given a base network made up with two-way links, candidate link expansion projects, and candidate link construction projects, the problem determines the optimal combination of one-way and two-way links, the optimal selection of capacity expansion projects, and the optimal lane allocations on two-way links over a dual time scale. The problem considers both the total travel time and the total CO emissions as the two objective function measures. The problem is modelled using a time-dependent approach that considers a planning horizon of multiple years and both morning and evening peaks. Under this approach, the model allows determining the sequence of link construction, the expansion projects over a predetermined planning horizon, the configuration of street orientations, and the lane allocations for morning and evening peaks in each year of the planning horizon. This model is formulated as a mixed-integer programming problem with mathematical equilibrium constraints. In this regard, two multi-objective metaheuristics, including a modified non-dominated sorting genetic algorithm (NSGA-II) and a multi-objective B-cell algorithm, are proposed to solve the above-mentioned problem. Computational results for various test networks are also presented in this paper.     

Effect of self-fields on the electron cyclotron maser instability in a dielectric loaded waveguide

The influence of self-fields on the cyclotron maser instability in a hollow electron beam propagating parallel to a uniform axial magnetic field B ₀ ê _z in a dielectric loaded waveguide is investigated. The theoretical analysis is carried out within the framework of linearized Vlasov-Maxwell equations. It is assumed that the beam is thin with the radial thickness much smaller than the beam radius. A new dispersion relation for azimuthally symmetric electromagnetic perturbation is derived and analyzed numerically. The influence of self-fields on the cyclotron maser instability in a dielectric loaded waveguide for different dielectric medium is studied. It is found that unlike the hollow waveguide the growth rate is increased by increasing self-fields. The instability band width decreases due to the increasing self-fields. The maximum growth rate increases gradually as self-fields increase as regards a different dielectric medium.     

A new molecularly imprinted polymer for selective extraction and pre‐concentration of guaifenesin in different samples: Adsorption studies and kinetic modeling

This paper describes the synthesis of a molecularly imprinted polymer by chemical oxidation of pyrrole as the functional monomer, and at the presence of guaifenesin as the template. The prepared polymer was used as adsorbent in molecularly imprinted solid‐phase extraction followed by spectrophotometric determination. Different parameters in the solid‐phase extraction including sample pH, adsorbent weight, washing solution, and elution solvent were studied to determine optimum conditions for isolation and enrichment of guaifenesin. The results showed guaifenesin was quantitatively adsorbed on the molecularly imprinted polymer at pH 6.0 and completely eluted with an ethanol–water solution (50% v/v). An enrichment factor of four with satisfactory recoveries (87.0–95.0%) was obtained. The solid‐phase extraction columns could be used for up to six consecutive elution‐loading cycles without significant decreases in the analyte recoveries. The method had a dynamic range of 3.0 × 10^?6–1.5 × 10^?4 mol/L with a limit of detection and limit of quantification of 1.4×10^?6 and 4.5×10^?6 mol/L, respectively. The proposed procedure was used for the extraction and determination of guaifenesin in different pharmaceutical formulations, with satisfying results being achieved.     

Development of <Superscript>111</Superscript>In labeled insulin for receptor imaging/therapy

In order to target insulin receptors in various diabetic and insulinoma conditions, human recombinant insulin was successively labeled with [¹¹¹In]-indium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (ccDTPA). The best results of the conjugation were obtained by addition of 0.5 mL of an insulin pharmaceutical solution (5 mg/mL, in phosphate buffer, pH 8) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25 °C with continuous mild stirring for 30 minutes. Radio-thin layer chromatography (RTLC), instant thin layer chromatography (ITLC) and high performance liquid chromatography (HPLC) have shown an overall radiochemical purity of higher than 93% at optimized conditions (specific activity = 550–750 MBq/mg, radiochemical yield =81%). The white blood cell labeling capacity of the tracer was determined up to 4 hours at 37 °C. Preliminary in vivo studies in normal rat model was performed to determine the biodistribution of the radiotracer up to 48 hours. It showed a high liver and spleen uptake of the tracer which is consistent with other reported radiolabeled insulins. SPECT images have also shown high liver accumulation of the tracer.