New Membrane-Forming Aromatic Co-Poly(amide-imide)s: Influence of the Chemical Structure on the Morphological, Thermal and Transport Properties

Polymer film membranes are used to solve specific separation problems that dictate structural requirements. Structural and morphological parameters of film membranes based on glassy polyheteroarylenes can be controlled in the process of preparation from solutions that opens up prospects for obtaining structured membranes required for targeted separation. In the case of aromatic poly(amide-imide)s, the possibility of controlling film formation and structure virtually has not been studied. In the present work, a series of homologous co-poly(amide-imide)s differing in the number of repeating units with carboxyl-substituted aromatic fragments was synthesized by polycondensation. Comparative analysis of the processes of formation of membranes with different morphologies based on these polymers under equal conditions was performed. New information was obtained about the influence of the amounts of carboxyl groups and the residual solvent on structural properties of asymmetric membranes. The influence of these factors on transport properties of dense membranes under pervaporation conditions was studied. It was demonstrated that in the case of carboxyl-containing poly(amide-imide)s, the domains formed during film preparation had a significant effect on membrane properties.

Development of a mafedine lyophilizate for parenteral use

Introduction. Cerebrovascular disease (CVD) is the most important medical and social problem of modern neurology because they have the highest rates of morbidity, mortality and disablement in the population. The growing incidence of CVD as a result of an aging population worldwide requires the emergent development of therapeutics, diagnostic and preventive tools. However, the development of drugs for the treatment of brain diseases has limitations due to the presence of the blood-brain barrier, which protects the brain against most molecules from the bloodstream entering the central nervous system. At the St. Petersburg State Chemical Pharmaceutical University of the Ministry of Health of Russia the alpha-2 adrenergic agonist mafedine was synthesized, which has mild psychostimulant and anxiogenic effects and which may be used in the treatment of traumatic brain injury as a neuroprotective agent.Aim. The development of a dosage form of mafedine in order to improve its penetration into the central nervous system.Materials and methods. Mafedine (pharmaceutical substance) [6-oxo-1-phenyl-2-(phenylamino)-1,6-dihydropyrimidin-4-olate sodium] (St. Petersburg State Chemical-Pharmaceutical University of the Ministry of Health of Russia); lecithin, span-60, Tween-80, Poloxamer 188, mannitol, vitamin E, ascorbic acid, methylene chloride, dimethyl sulfoxide, acetonitrile, trifluoroacetic acid. The fine emulsion of mafedine was obtained by ultrasound. The dosage form of mafedine was obtained by freeze drying. Residual solvents were determined by gas chromatography. Quantitative analysis of mafedine was performed by high-performance liquid chromatography. Particle size and zeta potential of emulsion were determined on a Zetasizer Nano ZS.Results and discussion. Lyophilizate of mafedine was obtained and presenting as a light yellow porous, odorless tablet. The average mass of dry tablet was (0,17 ± 0,01) g with mafedine content is (26 ± 1) mg. The water content in the lyophilizate was 3,85 %. The quantity of methylene chloride in the lyophilizate correspond to the requirements for residual solvent content. The reconstitution time of lyophilizate into a primary emulsion was 3–5 seconds. The reconstituted dispersion was yellow, odorless, and did not break within 2 days during storage. The pH of the reconstituted emulsion was 7,34. The average particle size was (164,7 ± 6,4) nm, the zeta potential was –32 mV.Conclusion. The developed dosage form is stable according to its physicochemical and pharmaceutical characteristics and is suitable for experimental study on models as a neuroprotective and neurorehabilitation agent.

Application of Gas Chromatography for the Analysis of Residual Solvents in Transdermal Drug Delivery Systems (TDS)

Background: Transdermal drug delivery systems (TDS) are widely used to deliver a number of different drug therapeutics. The design delivery can be impacted by excipients and, more broadly, organic solvents. Organic or residual solvents are routinely monitored due to safety concerns. However, there is little information on the mechanical properties and delivery performance of TDS. Objective: The objective of this study was to develop and validate an efficient GC-Headspace method to determine the residual solvents (n-heptane, o-xylene, and ethyl acetate) in transdermal patches. The analytical method was applied to monitor residual solvents in TDS and evaluate the potential effect of the residual solvent levels on the TDS adhesion properties. Methods: An Agilent GC 7890A was integrated with an Agilent headspace analyzer 7697A system and was used for method development, analytical method validation, and the testing phases of the study. For the analysis of residual solvents in TDS, 2cm x 3cm, a TDS sample was placed in a 20 mL Headspace vial containing 2 mL of a DMSO/water (1:1, v/v) solvent mixture, and an external standard (cyclohexane) was extracted by the headspace analyzer. The system suitability test was conducted according to USP <621>, and analytical method validation was conducted according to USP <1225> over 3 days for validation and was also performed during in-study sample analysis. Results: The resolution between the solvents was acceptable (2.5, %RSD = 8.0). Intra- and inter-day accuracy and precision of all quality control standards as well as the spiked standards in the transdermal patches were found to be acceptable with RSD% ≤ 10% and accuracy ≥ 85%, respectively. Linearity was > 0.99 for all analytes. Conclusion: The validated GC-Headspace method was successfully applied to a pilot study for in-house manufactured TDS patches to study the impact of residual solvent concentration on adhesion performance.

ANTHOCYANIN EXTRACTION OF RED DRAGON FRUIT PEELS (Hylocereus polyrhizus) USING MACERATION METHOD

Anthocyanins present in the red dragon fruit peel (Hylocereus polyrhizus) can be used as natural dyes. An extraction procedure can be used to acquire anthocyanins. The maceration method was used to isolate anthocyanin dyes in this analysis. The aim of this study was to see how the solvent ratio affected the total anthocyanin content in the skin of red dragon fruit. This research used laboratory experimental method using descriptive analysis. The solvent ratios used were (1:30, 1:40, 1:50 and 1:60) with a mixture of distilled water with 10% citric acid as the solvent. Parameters observed were total yield, pH, residual solvent content, spesific gravity and total anthocyanin content. The best treatment was found to be red dragon fruit peel with a solvent ratio of 1:30, which produced the highest total anthocyanin content of 4.73 mg/L. This treatment resulted total yield 7.40%, residual solvent content 0.05%, spesific gravity 1.30, and pH 1.05, respectively. It was proven that the more solvent added could linearly decrease the effectiveness of anthocyanin extraction of dragon fruit peel extracts.

The Influence of Sonication Processing Conditions on Electrical and Mechanical Properties of Single and Hybrid Epoxy Nanocomposites Filled with Carbon Nanoparticles

Graphene nanoplatelets (GNP) and carbon nanotubes (CNT) are used to enhance electrical and mechanical properties of epoxy-based nanocomposites. Despite the evidence of synergetic effects in the hybrid GNP-CNT-epoxy system, there is still a lack of studies that focus on the influence of different dispersion methods on the final properties of these ternary systems. In the present work, direct and indirect ultrasonication methods were used to prepare single- and hybrid-filled GNP-CNT-epoxy nanocomposites, varying the amplitude and time of sonication in order to investigate their effect on electrical and thermomechanical properties. Impedance spectroscopy was combined with rheology and electron microscopy to show that high-power direct sonication tends to degrade electrical conductivity in GNP-CNT-epoxy nanocomposites due to damage caused in the nanoparticles. CNT-filled samples were mostly benefitted by low-power direct sonication, achieving an electrical conductivity of 1.3 × 10−3 S·m−1 at 0.25 wt.% loading, while indirect sonication was not able to properly disperse the CNTs and led to a conductivity of 1.6 ± 1.3 × 10−5. Conversely, specimens filled with 2.5 wt. % of GNP and processed by indirect sonication displayed an electrical conductivity that is up to 4 orders of magnitude higher than when processed by direct sonication, achieving 5.6 × 10−7 S·m−1. The introduction of GNP flakes improved the dispersion state and conductivity in hybrid specimens processed by indirect sonication, but at the same time impaired these properties for high-power direct sonication. It is argued that this contradictory effect is caused by a selective localization of shorter CNTs onto GNPs due to strong π-π interactions when direct sonication is used. Dynamic mechanical analysis showed that the addition of nanofillers improved epoxy’s storage modulus by up to 84%, but this property is mostly insensitive to the different processing parameters. Decrease in crosslinking degree and presence of residual solvent confirmed by Fourier-transform infrared spectroscopy, however, diminished the glass transition temperature of the nanocomposites by up to 40% when compared to the neat resin due to plasticization effects.

Development and Validation of Head-space Gas Chromatographic Method in Tandem with Flame ionized detection for the determination of Residual solvents in Simeprevir API Synthesis

Residual solvent testing is an integral part of reference material certification. A gas chromatography/flame ionization detector/headspace method has been developed and validated to detect and quantitate commonly used residual solvents in our production processes: Methanol, Tetrahydrofuran, Toluene, Dichloromethane and Dichloroethane in Simeprevir API. A simple and selective HS-GC method is described for the determination & quantification of Residual Solvents in Simeprevir API. Chromatographic separation was achieved on USP G43 equivalent capillary column Thermo Scientific™ Trace GOLD™ TG-624 SilMS, 30m × 0.32mm × 1.8µm column (P/N 26059-3390) using nitrogen as carrier gas by using different temperature gradient of FID Detectors. Linearity was observed in the range 40-120% of standard concentrations for Methanol, Tetrahydrofuran, Toluene, Dichloromethane and Dichloroethane (r2>0.999) for the amount of solvent estimated by the proposed methods was in good agreement. The proposed methods were validated. The accuracy of the methods was assessed by recovery studies at three different levels. Recovery experiments indicated the absence of interference from commonly encountered diluent and API. The method was found to be precise as indicated by the repeatability analysis, showing %RSD less than 10 for Methanol, Tetrahydrofuran, Toluene, Dichloromethane and Dichloroethane. All statistical data proves validity of the methods and can be used for routine analysis of pharmaceutical active ingredients for estimation of Residual Solvents of Methanol, Tetrahydrofuran, Toluene, Dichloromethane and Dichloroethane in Simeprevir. Baseline separation of all five solvents and Simeprevir API is achieved within 20.5 minutes of analysis time. Method validation comprised the following parameters: limit of detection (LOD), limit of quantitation (LOQ), linearity and range, accuracy, precision (repeatability and intermediate precision), system suitability, specificity, and robustness. Linearity and LOQ (ppm) are listed for each solvent in manuscript. The present method was proven to be robust and accurate for quantitative analysis of residual solvent in neat materials.

Nanoparticles eluting stents for coronary intervention: Formulation, characterization and in vitro evaluation

Coronary artery disease (CAD) is currently a leading cause of death worldwide. In the history of percutaneous coronary intervention for the treatment of CAD, a drug-eluting stent (DES) is recognized as a revolutionary technology that has the unique ability to significantly reduce restenosis and provide both mechanical and biological solutions simultaneously to the target lesion. The aim of the research work was to design and fabricate DES coated with a nanoparticulate drug formulation. Sirolimus, an inhibitor of the smooth muscle cell (SMC) proliferation and migration, was encapsulated in polymeric nanoparticles. The nanoparticle formulation was characterized for various physicochemical parameters. Cell viability and cell uptake studies were performed using human coronary artery smooth muscle cells (HCASMCs). The developed nanoparticle formulation showed enhanced efficacy compared to plain drug solution and exhibited time-dependent uptake into the HCASMCs. The developed nanoparticle formulation was coated on the FlexinniumTM ultra-thin cobalt-chromium alloy coronary stent platform. The nanoparticle coated stents were characterized for morphology and residual solvent analysis. In-vitro drug release was also evaluated. Ex-vivo arterial permeation was carried out to evaluate the nanoparticle uptake from the surface of the stents. The characterization studies together corroborated that the developed nanoparticle coated stent can be a promising replacement of the current drug-eluting stents.