PAMAM Dendrimers as Potential Agents against Fibrillation of α‐Synuclein,a Parkinson's Disease‐Related Protein

The effect of PAMAM dendrimers (generations G3, G4 and G5) on the fibrillation of α‐synuclein was examined by fluorescence and CD spectroscopy, TEM and SANS. PAMAM dendrimers inhibited fibrillation of α‐synuclein and this effect increased both with generation number and PAMAM concentration. SANS showed structural changes in the formed aggregates of α‐synuclein – from cylindrical to dense three‐dimensional ones – as the PAMAM concentration increased, on account of the inhibitory effect. PAMAM also effectively promoted the breaking down of pre‐existing fibrils of α‐synuclein. In both processes – that is, inhibition and disassociation of fibrils – PAMAM redirected α‐synuclein to an amorphous aggregation pathway.

     

Experimental study on stability of different solid contact arrangements of ion-selective electrodes

Comparison of potentials stability of different types of solid contact lead selective electrodes is presented. Conducting polymer based sensors (hydrophilic and conducting - poly(3,4-ethylenedioxythiophene) or hydrophobic and semiconducting-polyoctylthiophene) were studied in parallel with coated wire and hydrogel (poly(hydroxyethylmethacrylate)) contact electrodes. The within day and between days potential stability was compared, highlighting the effect of sensor storing conditions. The obtained results clearly demonstrate that different conclusions on stability of sensors’ potential can be drawn depending on experimental protocol applied. Polyoctylthiophene based contacts show superior within day stability with no influence of dry storage. On the other hand, a chronopotentiometric method of stability evaluation clearly prefers poly(3,4-ethylenedioxythiophene) based sensors, pointing to smallest resistance and polarizability. It is clearly shown that the choice of experimental conditions applied to test stability can favor particular type of contact used.The inductively coupled plasma mass spectrometry with laser ablation (LA-ICP-MS) experiments conducted for different arrangements tested has shown that for poly(3,4-ethylenedioxythiophene) and poly(hydroxyethylmethacrylate) type contacts longer contact time with lead(II) solution results in changes in the elemental composition of the transducer layer. On the other hand, in line with high stability observed under potentiometric conditions, no changes were seen for polyoctylthiophene based transducer.     

Stereoselective formation of a P-P bond in the reaction of 2-alkoxy-2-thio-1,3,2-oxathiaphospholanes with O,O-dialkyl H-phosphonates and H-thiophosphonates

A new method for the formation of organohypophosphates containing a P-P bond under mild conditions, based on the DBU-assisted reaction of 2-alkoxy-2-thio-1,3,2-oxathiaphospholanes with O,O-dialkyl H-phosphonates or H-thiophosphonates, has been elaborated. The resulting triesters of P(1)-thio- and P(1),P(2)-dithiohypophosphoric acids, respectively, having O-methyl or O-ethyl groups, can be selectively dealkylated to form the corresponding di- or monoesters. Appropriately protected 2'-deoxyguanosine-3'-O-(2-thio-1,3,2-oxathiaphospholane) was converted into the corresponding P(1)-thio- and P(1),P(2)-dithiohypophosphate esters in a highly stereoselective manner (98%+ and 90%+, respectively).     

Determination of hafnium at the 10% level (relative to zirconium content) using neutron activation analysis,inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry

Hafnium at the very low level of 1–8 ppm (in relation to zirconium) was determined in zirconium sulfate solutions (originating from investigations of the separation of ca. 44 ppm Hf from zirconium by means of the ion exchange method) by using three independent methods: inductively coupled plasma mass spectrometry (ICP MS), neutron activation analysis (NAA) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results of NAA and ICP MS determinations were consistent with each other across the entire investigated range (the RSD of both methods did not exceed 38%). The results of ICP-AES determination were more diverse, particularly at less than 5 ppm Hf (RSD was significantly higher: 29–253%). The ion exchange method exploiting Diphonix^® resin proved sufficient efficiency in Zr–Hf separation when the initial concentration ratio of the elements ([Zr]₀/[Hf]₀) ranged from 1200 to ca. 143,000.     

Anodic polarization of nanocrystalline titanium

TiO₂ nanotubes are extensively investigated because of their unique properties and wide range of applications, e.g., in biomedicine. They are used as coatings on titanium implant materials accelerating osteoblast (bone cell) adhesion and improving osteointegration. Owing to its high mechanical properties, nanocrystalline titanium is likely to replace the widely used titanium alloys, which contains harmful ions such as V and Al. The performance properties of nanocrystalline titanium can be modified by subjecting it to various surface treatments tailored to the demands of a given application. The aim of this study is to determine whether the grain refinement of the titanium substrate has an influence on the formation of TiO₂ nanotubes. The TiO₂ nanotubes were fabricated by anodic polarization of micro- and nanotitanium at a constant voltage of 10, 15, and 20 V for 2 h in an electrolyte containing fluoride ions. The nanocrystalline bulk titanium (grade 2) with grain size of about 90 nm and high density of dislocations was obtained using hydrostatic extrusion. Commercially available coarse-grained titanium with grain size of 20 μm was used as a reference sample. The microstructure of the fabricated nanotubular layers was revealed using scanning electron microscopy and focus ion beam microscopy. Auger electron spectroscopy and X-ray photoelectron spectroscopy were used to determine the chemical composition of the fabricated layers. The results indicate that grain refinement influences the morphology of TiO₂ nanotubes while their chemistry remains unchanged.     

Synthesis of polyfunctional phosphorodithioates and structural analogues mediated by azetidinium ions and epoxides

The nucleophilic ring opening reactions of N,N-dialkyl-3-hydroxy(benzyloxy)azetidinium salts 1 and N,N-dibenzyl-2,3-epoxypropylamine 10 with anions of mono- and dithioacids of phosphorus 2 affords phosphorodithioates (and structural analogues) 3 and 11 possessing S-propyl substituents incorporating 2-hydroxy and 3-dialkylamino functionalities. A strong dependence of the stability of these compounds on structural factors is discussed.     

HPLC-UV and GC-MS Methods for Determination of Chlorambucil and Valproic Acid in Plasma for Further Exploring a New Combined Therapy of Chronic Lymphocytic Leukemia

High performance liquid chromatography with ultra-violet detection (HPLC-UV) and gas chromatography–mass spectrometry (GC-MS) methods were developed and validated for the determination of chlorambucil (CLB) and valproic acid (VPA) in plasma, as a part of experiments on their anticancer activity in chronic lymphocytic leukemia (CLL). CLB was extracted from 250 µL of plasma with methanol, using simple protein precipitation and filtration. Chromatography was carried out on a LiChrospher 100 RP-18 end-capped column using a mobile phase consisting of acetonitrile, water and formic acid, and detection at 258 nm. The lowest limit of detection LLOQ was found to be 0.075 μg/mL, showing sufficient sensitivity in relation to therapeutic concentrations of CLB in plasma. The accuracy was from 94.13% to 101.12%, while the intra- and inter-batch precision was ≤9.46%. For quantitation of VPA, a sensitive GC-MS method was developed involving simple pre-column esterification with methanol and extraction with hexane. Chromatography was achieved on an HP-5MSUI column and monitored by MS with an electron impact ionization and selective ion monitoring mode. Using 250 µL of plasma, the LLOQ was found to be 0.075 μg/mL. The accuracy was from 94.96% to 109.12%, while the intra- and inter-batch precision was ≤6.69%. Thus, both methods fulfilled the requirements of FDA guidelines for the determination of drugs in biological materials.     

N-Skatyltryptamines—Dual 5-HT6R/D2R Ligands with Antipsychotic and Procognitive Potential

A series of N-skatyltryptamines was synthesized and their affinities for serotonin and dopamine receptors were determined. Compounds exhibited activity toward 5-HT_1A, 5-HT_2A, 5-HT₆, and D₂ receptors. Substitution patterns resulting in affinity/activity switches were identified and studied using homology modeling. Chosen hits were screened to determine their metabolism, permeability, hepatotoxicity, and CYP inhibition. Several D₂ receptor antagonists with additional 5-HT₆R antagonist and agonist properties were identified. The former combination resembled known antipsychotic agents, while the latter was particularly interesting due to the fact that it has not been studied before. Selective 5-HT₆R antagonists have been shown previously to produce procognitive and promnesic effects in several rodent models. Administration of 5-HT₆R agonists was more ambiguous—in naive animals, it did not alter memory or produce slight amnesic effects, while in rodent models of memory impairment, they ameliorated the condition just like antagonists. Using the identified hit compounds 15 and 18, we tried to sort out the difference between ligands exhibiting the D₂R antagonist function combined with 5-HT₆R agonism, and mixed D₂/5-HT₆R antagonists in murine models of psychosis.     

Comparative analysis of commercial dermal fillers based on crosslinked hyaluronan: Physical characterization and in vitro enzymatic degradation

The cosmetic market for hyaluronic acid (HA)-based dermal fillers is in continuous and rapid growth and, simultaneously, the development of more effective and safer products is strongly intensifying. In order to highlight the differences among the currently available fillers, in terms of their physical characteristics and on the relation of such properties with product effectiveness, an in vitro evaluation of eight marketed HA-based gels was performed.Filler swelling properties, soluble HA fraction and rheological behaviour were investigated. Furthermore the relative stability to enzymatic hydrolysis was tested. The presence of soluble HA in the formulations varied from 7 ± 1(%) to 33 ± 5(%) with respect to the total HA concentration. Chromatographic analyses showed that the soluble fractions consist of low molecular weight chains (M_w: 260-480 kDa) presenting large distributions (M_w/M_n: 1.6-2.5). The investigated fillers were found to be non-equilibrium gels in their commercial formulation also showing different swelling capacities. Rheological measurements indicated a shear thinning behaviour for all the products and elastic modulus values varied over a wide range (100-1800 Pa). Fillers proved differently sensitive to enzymatic degradation. Swelling capacity and enzymatic stability were found consistently dependent on the total HA concentration, insoluble/soluble HA ratio and on the crosslinking extent.