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.     

Synthesis,characterization, and molecular structures of Ni(II) and Cd(II) complexes derived from dithiophosphonate

Two novel dithiophosphonate ligands, HS₂P(p‐C₆H₄OMe)(OCH₂CH₂CH(CH₃)₂) ( 1 ) and HS₂P(p‐C₆H₄OMe)(OCH(CH₃)₂) ( 2 ), were synthesized and characterized by multinuclear (¹H, ³¹P, and ¹³C) NMR, infrared spectroscopy as well as elemental analysis. The reactions of 1 and 2 with NiCl₂·6H₂O and Cd(NO₃)₂·4H₂O in methanol led to novel complexes 3 and 4 . The single crystal X‐ray structures of 3 and 4 showed tetracoordinated structure with square planar geometry for the nickel complex, while it showed pentacoordinated structure with distorted square‐pyramid environment for the cadmium complex.     

l-Proline-catalysed one-pot synthesis of tetrahydrobenzo[c]acridin-8(7H)-ones at room temperature

Only 10 mol% of l-Proline in ethanol proved to be a very efficient catalyst for the one-pot synthesis of a wide variety of highly substituted tetrahydrobenzo[c]acridin-8(7H)-ones at room temperature. The key advantages of this process are high yields, cost effectiveness of the catalyst, easy work-up and the products can be directly recrystallized from hot ethanol.     

Development of a New Dynamic Headspace Liquid-Phase Microextraction Method

A new technique, namely dynamic headspace liquid-phase microextraction, has been developed for the extraction of 1,4-dioxane in cosmetic and hygiene samples followed by gas chromatography–flame ionization detection. In this method, the sample is mixed with acetone as a diluent solvent. Then, a few microliters of n-octanol are added into a home-made extraction vessel placed in the headspace of the sample. By heating, the target analyte is transferred to the headspace of the sample and then extracted into n-octanol. Under the optimized conditions, the method showed a good linearity in the range of 3.24–1000 μg kg⁻¹ with a coefficient of determination 0.998. Figures of merit such as enrichment factor of 375, extraction recovery of 94 %, limits of detection and quantification 0.97 and 3.24 μg kg⁻¹, respectively, and relative standard deviation 4.7 % (n = 6, C = 30 μg kg⁻¹) of the proposed method were satisfactory for determination of the target analyte. Finally, the method was successfully applied in determination of 1,4-dioxane in various cosmetic and hygiene samples including shampoo, toothpaste, lotion, washing liquid, and dishwashing liquid.

     

A practical innovative method for highly selective oxidation of alkenes and alkanes using Fe (III) and Mn (III) porphyrins supported onto multi‐wall carbon nanotubes as reusable heterogeneous catalysts

Functionalized multi‐walled carbon nanotubes were used for covalent immobilization of meso‐tetrakis(4‐carboxyphenyl) porphyrinatoiron (III) chloride [Fe (TCPP)Cl] and meso‐tetrakis(4‐carboxyphenyl) porphyrinatomanganese (III) acetate [Mn (TCPP)OAc]. The full characterization of the hybrid porphyrinic nanomaterials, by Fourier transform‐infrared and UV–Vis spectroscopy, transmission electron microscopy, thermogravimetry and flame atomic absorption spectrometry is described. The oxidation of alkenes and alkanes with molecular oxygen as green oxidant in the presence of Mn‐ and Fe‐catalysts has been studied in a comparative manner. The Fe‐catalyst was shown to have higher catalytic activity compared with the Mn‐catalyst. In addition, both separable solid catalysts can be recovered and reused at least 10 times along with good yields.     

Copper nanoparticles incorporated on a mesoporous carbon nitride,an excellent catalyst in the Huisgen 1,3‐dipolar cycloaddition and N‐arylation of N‐heterocycles

Cu nanoparticles with average particles size around 10 nm were incorporated on the surface of a mesoporous carbon nitride support. The XRD and N₂ adsorption isotherms show that it maintains a hexagonal mesoporous structure with a high surface area (600.03 m² g^?1). The embedded Cu nanoparticles exhibit extremely high catalytic performance in two different kinds of organic reactions. The Huisgen 1,3‐dipolar cycloaddition and N‐arylation of N‐heterocycles were all accomplished.     

Development of a dispersive liquid–liquid microextraction (DLLME) method coupled with GC/MS as a simple and valid method for simultaneous determination of phthalate metabolites in plasma

Phthalates are ubiquitous environmental contaminants, and frequent biological monitoring of their metabolites (as toxic species of phthalates in human body) is highly recommended. A novel dispersive liquid–liquid microextraction (DLLME) coupled with Gas Chromatography–Mass Spectrometry (GC-MS) has been developed for the determination of seven phthalate metabolites in human plasma for the first time. Plasma proteins were efficiently precipitated by adding of 0.2mg dry trichloroacetic acid to 10 mL plasma samples, incubation and centrifuging. For DLLME, a mixture of extraction solvent (chlorobenzene, 10 µL) and dispersive solvent (acetonitrile, 750 µL) were rapidly injected into 5.0 mL aqueous sample for the formation of cloudy solution, the analytes in the sample were extracted into the fine droplets of chlorobenzene. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were subjected to GC-MS analysis. All important parameters affecting DLLME performance were investigated and optimised. Under the optimum extraction condition, the method yields a linear calibration curve for all target analytes in the concentration range from 5 to 5000 ng mL^?1. The limits of detection and relative standard deviations for all phthalate metabolites were between 1.21–2.09 ng mL^?1 and 4.8–6.8%, respectively. This is a very simple, rapid and reproducible method, which requires low volume of sample and toxic solvents.     

Development of dynamic headspace-liquid phase microextraction method performed in a home-made extraction vessel for extraction and preconcentration of 1,4-dioxane from shampoo

In the present study, a new, simple, rapid, and environmentally friendly headspace-liquid phase microextraction method followed by gas chromatography–flame ionization detection has been developed for the extraction/preconcentration and determination of 1,4-dioxane from shampoo. The developed procedure is performed in a home-made extraction vessel, connected to a glass vial containing sample and extraction solvent. In this method, an aliquot weight of shampoo is mixed with a binary mixture of n-hexane and dichloromethane (50:50, v/v) as the extractant and the target analyte is extracted during a liquid–liquid extraction procedure. Then a home-made extraction vessel containing a few microliters of a collection/extraction solvent is contacted to a glass vial containing the organic phase obtained from the previous step. By heating 1,4-dioxane is vaporized and enriched in a μL volume of the collection/extraction solvent. Then an aliquot volume of the collected phase is injected into the separation system. The effect of several factors which may influence performance of the method, including kind and volume of the extraction solvents used in both steps, extraction temperature, extraction time, and salt addition were evaluated. Under the optimum extraction conditions, limits of detection and quantification for the target analyte were obtained 0.52 and 1.73 μg kg^?1, respectively. Enrichment factor and extraction recovery were 333 and 89 %, respectively. The method precision was evaluated at a concentration of 25 μg kg^?1 and relative standard deviation was less than 6.9 % for intra-day (n = 6) and inter-day (n = 4) precisions. Finally, the proposed method has been successfully applied in analysis of 1,4-dioxane in different shampoo samples.