Nanosized T1 MRI Contrast Agent Based on a Polyamidoamine as Multidentate Gd Ligand

A linear polyamidoamine (PAA) named BAC-EDDS, containing metal chelating repeat units composed of two tert-amines and four carboxylic groups, has been prepared by the aza-Michael polyaddition of ethylendiaminodisuccinic (EDDS) with 2,2-bis(acrylamido)acetic acid (BAC). It was characterized by size exclusion chromatography (SEC), FTIR, UV–Vis and NMR spectroscopies. The pKa values of the ionizable groups of the repeat unit were estimated by potentiometric titration, using a purposely synthesized molecular ligand (Agly-EDDS) mimicking the structure of the BAC-EDDS repeat unit. Dynamic light scattering (DLS) and ζ-potential analyses revealed the propensity of BAC-EDDS to form stable nanoaggregates with a diameter of approximately 150 nm at pH 5 and a net negative charge at physiological pH, in line with an isoelectric point <2. BAC-EDDS stably chelated Gd (III) ions with a molar ratio of 0.5:1 Gd (III)/repeat unit. The stability constant of the molecular model Gd-Agly-EDDS (log K = 17.43) was determined as well, by simulating the potentiometric titration through the use of Hyperquad software. In order to comprehend the efficiency of Gd-BAC-EDDS in contrasting magnetic resonance images, the nuclear longitudinal (r1) and transverse (r2) relaxivities as a function of the externally applied static magnetic field were investigated and compared to the ones of commercial contrast agents. Furthermore, a model derived from the Solomon–Bloembergen–Morgan theory for the field dependence of the NMR relaxivity curves was applied and allowed us to evaluate the rotational correlation time of the complex (τ = 0.66 ns). This relatively high value is due to the dimensions of Gd-BAC-EDDS, and the associated rotational motion causes a peak in the longitudinal relaxivity at ca. 75 MHz, which is close to the frequencies used in clinics. The good performances of Gd-BAC-EDDS as a contrast agent were also confirmed through in vitro magnetic resonance imaging experiments with a 0.2 T magnetic field.

A Comparative Study on Nickel Binding to Hpn-like Polypeptides from Two Helicobacter pylori Strains

Combined potentiometric titration and isothermal titration calorimetry (ITC) methods were used to study the interactions of nickel(II) ions with the N-terminal fragments and histidine-rich fragments of Hpn-like protein from two Helicobacter pylori strains (11637 and 26695). The ITC measurements were performed at various temperatures and buffers in order to extract proton-independent reaction enthalpies of nickel binding to each of the studied protein fragments. We bring up the problem of ITC results of nickel binding to the Hpn-like protein being not always compatible with those from potentiometry and MS regarding the stoichiometry and affinity. The roles of the ATCUN motif and multiple His and Gln residues in Ni(II) binding are discussed. The results provided the possibility to compare the Ni(II) binding properties between N-terminal and histidine-rich part of Hpn-like protein and between N-terminal parts of two Hpn-like strains, which differ mainly in the number of glutamine residues.

Measurement of Solubility of CO2 in NaCl, CaCl2, MgCl2 and MgCl2 + CaCl2 Brines at Temperatures from 298 to 373 K and Pressures up to 20 MPa Using the Potentiometric Titration Method

Understanding the carbon dioxide (CO2) solubility in formation brines is of great importance to several industrial applications, including CO2 sequestration and some CO2 capture technologies, as well as CO2-based enhanced hydrocarbon recovery methods. Despite years of study, there are few literature data on CO2 solubility for the low salinity range. Thus, in this study, the solubility of CO2 in distilled water and aqueous ionic solutions of NaCl, MgCl2, CaCl2 and MgCl2 + CaCl2 were obtained in a low salinity range (0–15,000 ppm) at temperatures from 298–373 K and pressures up to 20 MPa using an accurate and unconventional method called potentiometric titration. An experimental data set of 553 data points was collected using this method. The results of the experiments demonstrate that increasing pressure increases the solubility of CO2 in various brines, whereas increasing temperature and salinity reduces the solubility. The role of different ions in changing the solubility is elaborated through a detailed discussion on the salting-out effect of different ionic solutions. To verify the experimental results of this research, the solubility points obtained by the potentiometric titration method were compared to some of the well-established experimental and analytical data from the literature and a very good agreement with those was obtained.

Potential and practical implementation of bioactive polyvinylsuccinate derivatives

A review of the works reflecting the authors' research on the synthesis and study of the physico-chemical properties of polymer biologically active substances (BAS) is presented. The research results are analyzed in relation to the specific biological activity of polymers in order to establish the possibility of predicting their prolonged bioactive effect based on the values of the constants of formation, stability, dissociation and other characteristics of complexes of ionogenic polymers and BAS using methods of potentiometric titration, conductometry, viscometry, thermal analysis methods, equilibrium dialysis, biological tests.

Bulk Solution Assay Test Procedure Development and validation for Esomeprazole Sodium Injection 40mg as a CPP

Assay analytical test procedure at the Bulk-Solution stage for Esomeprazole Sodium Injection 40mgas a Critical Processing Parameters during manufacturing developed and validated. As per current available literature and the references, Esomeprazole active substance is available in market in the five forms, i.e. Esomeprazole as Plain [Tablet]; Esomeprazole Magnesium Trihydrate [Tablet, Capsule Delayed Release]; Esomeprazole Potassium [Tablet and Capsule]; Esomeprazole Strontium [Capsule Delayed Release] and Esomeprazole Sodium [Injectable].Assay test procedure for Active and other dosage forms [Tablet, Capsule] were available based on either Potentiometric Titration or HPLC basis. Product Esomeprazole Sodium Injection 40mg is not available in official pharmacopeia. As per available reference and literature assay test method for intermediate testing and finished product is based on HPLC. Intermediate testing [In-Process Testing] required as Critical Process Parameters [CPP] to ensure the quality i.e. appropriate bulk-solution purity, before to proceed for filtration and filling of Bulk-solution in unit dosage form [Vials]. To test the bulk solution purity approximate 5-6 hours required by HPLC. Which leads to hold the Bulk solution, further it impact and may risk to Bio-Burden of bulk solution. Also it impact and reduce the productivity of line by 5-6 hours. HPLC testing required special skilled manpower and cost. Considering all above concerns Study carried for test method development based on UV-Spectroscopy, HPLC and potentiometric titration. Based on method validation performed for UV-Spectrometry, HPLC and potentiometric titration; Test procedure developed and validated based on UV-Spectrometry is found Simple, Accurate, Precise, Economical and Rapid to save time and cost with increase in productivity as a Critical Processing Parameters for Esomeprazole Sodium Injection 40mgat the Bulk-Solution stage during manufacturing.

Polymer Sorbents from “Nitron Fiber Waste”

New sorbents were synthesized from nitron fiber waste modified with various anion-exchange groups. The structure was studied by potentiometric titration and IR spectroscopy. The possibility ихof using them for immobilizationis shown, andthe physicochemical characteristics of polymer sorbentsare studied.

Potentiometric Titration of Vanadium (V) with Iron (II) in the Presence of NTA and DTPA Using Dry-Cell Graphite Electrode

A sensitive potentiometric titration for vanadium (V) based effect of ligands such as nitrilotriacetic acid (NTA) and diethylenetriaminepenta-acetic acid (DTPA) are reviewed. The potential iron system decreased the presence of NTA and DTPA. In this case, iron (III) increased with respect to the vanadium (IV) volume. The production of iron (III)-ligand complex has increased. This result suggested that the formation of V(V)-NTA and V(V)-DTPA complexes were less favoured than that of V(IV)-NTA and V(IV)-DTPA complexes. The calculated correlation coefficients (r) conveyed the effectiveness of the graphite electrode as the indicator electrode for the potentiometric titrations. On comparing the potential jump values, the extent of potential caused by DTPA was found to be more than that of NTA. The utilization of graphite electrode has facilitated the potentiometric titration by significantly causing larger potential jump. This method was precise and accurate as no interference of foreign ions was observed. Hence, the approach could be applied to the vanadium (V) of any samples.