An in vitro release study of indomethacin from nanoparticles based on methyl methacrylate/glycidyl methacrylate copolymers

Indomethacin was coupled onto some macromolecular nanostructures based on methyl methacrylate copolymers with glycidyl methacrylate and tested as a model drug. The polymeric matrices were synthesized by radical emulsion copolymerization with and without the presence of a continuous external magnetic field of 1500 Gs intensity. Mathematical analysis of the release data was performed using Higuchi, Peppas–Korsmeyer equations. NIR chemical imaging (NIR-CI) was used to provide information about the spatial distribution of the components in the studied nanostructures. This opportunity was used to visualize the spatial distribution of bioactive substances (indomethacin) into the polymeric matrix, as well as to evaluate the degree of chemical and/or physical heterogeneity of the bioactive samples. The release rate dependence on the synthesis conditions as well as on the chemical compositions of the tested polymeric systems, it was also evidenced.     

Probing the heat‐induced structural changes in bovine serum albumin by fluorescence spectroscopy and molecular modelling

The fluorescence spectroscopy and in silico methods were used to evaluate the structural changes in bovine serum albumin (BSA) over a temperature range of 25–70 °C for 15 min. Experimental results indicated that the polypeptide chain rearrangements at temperatures higher than 40 °C lead to a lower exposure of hydrophobic residues causing the decrease in fluorescence intensity. The nonlinearity of the phase diagram indicated a sequential denaturation process involving several molecular species. The molecular dynamics simulations at the single‐molecule level showed the high stability of the BSA structure, compensating for the entropic costs associated with the prevalent helical folding.     

How does hydrogen-based renewable energy change with economic development? Empirical evidence from 32 countries

The hydrogen-based renewable energy resource base is sufficient to meet several times the present world energy demand. This paper analyzes the drivers promoting hydrogen-based renewable energy utilization, focusing on a group of 32 countries by applying panel data techniques. The pooled ordinary least square estimator and fixed effect estimator are employed for comparison. Grey relational analysis is used to explore the relationships at a national level between renewable energy development and its influencing factors. The main results over our time span indicate that: (1) GDP per capita is a significantly positive contributor to renewable energy consumption, while oil price does not present a strong relationship in the use of renewables; (2) social awareness about climate change and concerns for energy security is not enough to motivate the switch from traditional to renewable energy sources; (3) the role of urbanization in renewable energy consumption relies on different stages of the urbanization process, resulting in opposite trends in renewable energy development between developing and developed countries. The results show that the market mechanism is not entirely responsible for encouraging the use of renewables and the role of climate change and energy security concerns in renewables use should be enhanced. By analyzing the results, policy implications are provided for the sustainable development of renewable energy.     

Localization of Mn2+ ions in mesoporous NnS

Nanocrystalline cubic ZnS doped with 0.2% mol manganese, exhibiting a stable mesoporous structure, was synthesized at room temperature by a non toxic surfactant-assisted liquid-liquid reaction. The X-ray diffraction measurements demonstrate the formation of a sponge-like mesoporous material built from cubic ZnS nanocrystals of 1.8 nm average sizes, with a tight distribution of pores of 1.8 nm mean diameter. The transmission electron microscopy images confirm the formation of the mesoporous structure with walls of 3.1 nm mean thickness built from cubic ZnS nanocrystallites of 2.1 nm average size. The resulting tight distribution of crystallites and pores yields a well resolved Electron Paramagnetic Resonance spectrum, with the narrowest reported component lines attributed to three types of isolated Mn2+ centers, called Mn2+(I), Mn2+(II) and Mn2+(III). From the analysis of the spin Hamiltonian parameters it is shown that in the Mn2+(I) centers the paramagnetic ion is situated at substitutional Zn sites in the ZnS nanocrystals, being also subjected to a small axial distortion. The relative concentration changes under thermal treatment experiments strongly suggest that in both Mn2+(II) and Mn2+(III) centers the Mn2+ ion is localized on the surface of the ZnS nanocrystallites, being bond to an oxygen ion in the first case and to an additional water molecule in the second case.     

Upon some multi-membrane hydrogels based on poly(N,N-dimethyl-acrylamide-co-3,9-divinyl-2,4,8,10-tetraoxaspiro (5.5) Undecane): preparation,characterization and in vivo tests

The study presents the possibility of preparation of multi-membrane gel systems with different morphologies and properties, based on poly(N,N-dimethyl-acrylamide-co-3,9-divinyl-2,4,8,10-tetraoxaspiro (5.5) undecane) copolymer and crosslinked with N,N′-methylene-bis-acrylamide. The basic copolymer has dual thermo- and pH sensitive character. After the core hydrogel is realized, the preformed gel is immersed in the aqueous solutions of ammonia, sodium chloride and sodium citrate for further edge constructing of the supramolecular assemblies. Then, the new layers by adding new sets of gelifying components are realized. The new multi-membrane gel systems are intended to be used as matrix for bioactive substances embedding. In this context the systems were loaded with norfloxacin as drug model. The in vivo tests show good biocompatibility for the implants based on multi-membrane gel structures loaded with drug.     

An enzyme flow immunoassay that uses beta-galactosidase as the label and a cellobiose dehydrogenase biosensor as the label detector

The aim was to develop a fast generic enzyme flow immunoassay (EFIA) using a beta-galactosidase (beta-GAL) label in combination with colorimetric detection as well as with a new amperometric biosensor as the label detector. The amperometric biosensor was previously developed within the group for the determination of diphenols in surface water samples. Antigen (Ag, analyte), tracer (Ag*, antigen labeled with beta-GAL), and antibody (Ab) were incubated off-line. After the equilibrium was reached, the sample was introduced into the flow system. The antibody complexes, AgAb and Ag*Ab, were trapped in a protein G column while the free unbound tracer was eluted and detected by an amperometric biosensor downstream after substrate reaction. The enzyme label beta-GAL converted the substrate 4-aminophenyl-beta-D-galactopyranoside (4-APG) into 4-aminophenol (4-AP), which subsequently was detected by a cellobiose dehydrogenase (CDH) modified solid graphite electrode. 4-AP was first oxidized at the electrode surface at +300 mV vs Ag/AgCl, and the formed 4-imino quinone (4-IQ) was reduced back to 4-AP by the CDH in the presence of cellobiose. By combining the EFIA with the CDH biosensor, the overall signal of one tracer molecule is amplified at two occasions, i.e., one enzyme label converts the substrate into many 4-AP molecules, and second these are further amplified by the CDH biosensor. The optimum conditions for the EFIA in terms of the molar ratio between tracer and beta-GAL, temperature, flow rate, etc., was investigated with colorimetric detection, using 2-nitrophenyl-beta-D-galactopyranoside (2-NPG) as the beta-GAL substrate. The performance of both the colorimetric and CDH biosensor detection was investigated and both methods were applied for determination of the model compound atrazine in spiked surface water samples. Detection limits of 0.056 +/- 0.008 and 0.038 +/- 0.007 microg L(-1) and IC50 values of 2.04 +/- 0.294 and 0.42 +/- 0.08 microg L(-1) were obtained for colorimetric and CDH detection, respectively. Matrix effects were less pronounced with the CDH biosensor than with colorimetric detection.     

The accuracy of CT and MR evaluation of the sella turcica for detection of adrenocorticotropic hormone-secreting adenomas in Cushing disease

PURPOSE: To document the accuracy of CT and MR of the sella turcica for detecting adrenocorticotropic hormone-secreting adenomas in Cushing disease. METHODS: The radiologic findings of the sella turcica prior to transsphenoidal surgery are reviewed in 141 patients who had biochemical evidence of pituitary-dependent Cushing disease. Axial thin-collimation CT scans with sagittal and coronal reformations before and after contrast enhancement were obtained in 125 patients. Seventy-eight patients had MR examinations with a 1.5-T superconducting magnet. In 11 of the patients gadolinium-enhanced MR scans were also obtained. The preoperative interpretation of the imaging studies was correlated with the surgical findings and patients follow-up. RESULTS: The sella turcica was enlarged in 43 cases (30%). In 125 patients reformatted or direct coronal thin-collimation CT scans were available. Seventy-eight of the patients had MR. In the 12 patients with pituitary macroadenomas, the accuracy of CT (n = 10) and MR (n = 10) in respect to detection of the lesion was 100%. Of the 98 microadenomas assessed by CT, 47 (48%) were directly depicted as distinct hypodense lesions. In only 31 of 73 cases (42%), however, could CT predict the precise anatomic location and extent of the lesions. Only patients in whom the hypercortisolism was corrected by later surgery were considered for the correlation analysis. Of the 52 microadenomas assessed by MR, 28 (53%) were directly depicted as distinct lesions of reduced signal intensity on T1-weighted images, and in only 21 of 41 cases (52%) did MR show good correlation to the surgical findings. Some degree of partially empty sella was found in 22% of the patients. CONCLUSIONS: Although both the sensitivity and the diagnostic accuracy of imaging methods of the sella turcica have been considerably improved in comparison with previous reports, they still provide only a minor contribution to the diagnosis and differential diagnosis of Cushing syndrome.     

Localization of uranium ions in synthetically grown CaF2.U single crystals

Single crystals of CaF₂ doped with 0.1% wt. uranium were grown by the Czochralski-Kyropoulos method. The localization of uranium ions was investigated by optical and transmission electron microscopy, optical absorption and electron spin resonance. These studies revealed not only the presence of isolated uranium ions but also of UO₂ agglomerates which can play an important role in understanding the properties of such systems.