T1−T2T_{1}-T_{2} dual-modal MRI contrast agents based on superparamagnetic iron oxide nanoparticles with surface attached gadolinium complexes

Dual-mode MRI contrast agents consisting of superparamagnetic iron oxide nanoparticle (SPION) cores and gadolinium ions associated with the ionic chitosan protecting layer were synthesized and studied. Gadolinium ions were introduced into the coating layer via direct complex formation on the nanoparticles surface, covalent attachment or electrostatically driven deposition of the preformed Gd complex. The modified SPIONs having hydrodynamic diameters ca. 100 nm form stable, well-defined dispersions in water and have excellent magnetic properties. Physiochemical prop- erties of those new materials were characterized using e.g., FTIR spectroscopy, dynamic light scattering, X-ray fluorescence, TEM, and vibrating sample mag- netometry. They behave as superparamagnetics and shorten both T 1 and T 2 proton relaxation times, thus influencing both r 1 and r 2 relaxivity values that reach 53.7 and 375.5 mM - 1 s - 1 , respectively, at 15 MHz. The obtained materials can be considered as highly effective contrast agents for low-field MRI, particu- larly useful at permanent magnet-based scanners

The influence of tobacco smoking on the plasma level of S-citalopram in patients treated for depression.

The aim of the study was evaluation of the effect of tobacco smoking on the pharmacokinetics of S-citalopram. The enzymes involved in the metabolism of drugs may have been induced or inhibited by the substances contained in tobacco smoke.For the determination of the plasma concentrations of citalopram and desmethylcitalopram and also the enantiomers of citalopram and their metabolites, the analytical methods validation was performed. Analyses were performed using high performance liquid chromatography (HPLC) connected with diode array detector (DAD). The results have confirmed the effectivness of the selected analytical methods.Epidemiological data of the patients treated with citalopram or escitalopram indicate there are no additional factors influencing on the pharmacokinetics of these drugs.The plasma concentrations of citalopram and desmethylcitalopram and also the enantiomers of citalopram and their metabolites were determined in human samples. All patients have been smokers. The results show that the citalopram’s steady-state concentration is close to the lower limit of quantification of analytical method. Furthermore, steady-state plasma level of S-citalopram is mostly below the level quoted in the literature. The results suggest that the substances contained in tobacco smoke may accelerate the elimination of citalopram and its S(+)-enantiomer from human body.W pracy badano wpływ palenia tytoniu na poziom S-citalopramu u pacjentów leczonych z powodu depresji. Zawarte w dymie tytoniowym substancje mogą indukować lub inhibować enzymy biorące udział w biotransformacji ksenobiotyków. Dokonano walidacji metod analitycznych oznaczania citalopramu (mieszanina racemiczna) i demetylocitalopramu oraz oznaczania enancjomerów citalopramu i ich metabolitów. Oznaczenia analitów wykonano metodą wysokosprawnej chromatografii cieczowej (HPLC) z detektorem spektrofotometrycznym z szeregiem diod (DAD). Następnie opracowano dane epidemiologiczne dotyczące pacjentów leczonych citalopramem lub escitalopramem w celu uwzględnienia wpływu różnych czynników na poziom badanych leków w osoczu ludzkim.Główną część badań stanowiło oznaczenie citalopramu i demetylocitalopramu oraz enancjomerów citalopramu i ich metabolitów w próbkach osocza ludzkiego pochodzących od pacjentów palących tytoń, którzy leczeni są z powodu depresji. Otrzymane wyniki wskazują, iż stężenie stacjonarne citalopramu jest zbliżone do dolnej granicy zakresu, w którym można go oznaczyć. Także w przypadku S-citalopramu w większości przypadków obserwuje się, iż poziom tego leku we krwi pacjentów palących tytoń jest niższy od danych literaturowych. Istnieje więc duże prawdopodobieństwo, że zawarte w dymie tytoniowym substancje mogą mieć wpływ na szybszą eliminację citalopramu oraz escitalopramu z organizmu ludzkiego

Properties of NiTi Shape Memory Alloy Micro-Foils Obtained by Pulsed-Current Sintering of Ni/Ti Foils

Successful one-step manufacturing of micro-foils of NiTi shape memory compound by pulsed-current sintering of nickel and titanium is reported. Sandwich-like starting configurations of Ni/Ti/Ni (ST1, ST4), Ti/Ni/Ti (ST3), and a simple Ni/Ti (ST2) one, were used. XRD and differential scanning calorimetry (DSC) measurements revealed multistep martensitic transformation, much more pronounced for ST1 than for ST2 and ST3. SEM/energy dispersive X-ray spectrometer (EDS) measurements showed the predominant NiTi phase in ST1, ST4, and other intermetallic compounds in addition to it, for ST2 and ST3. The temperature dependence of the electrical resistance for ST4 shows a peak corresponding to the R-phase and a high residual resistivity. The shape memory effect of 100% was obtained for ST1 and ST4, with the temperature range of its recovery dependent on the initial strain. The ST2 and ST3 materials revealed brittleness and a lack of plasticity due to the dominancy of the austenite phase and/or the intermetallic compound content