Enhancing cisplatin anticancer effectivity and migrastatic potential by modulation of molecular weight of oxidized dextran carrier.

The molecular weight (Mw) of dextran derivatives, such as regioselectively oxidized dicarboxydextran (DXA), is greatly influencing their faith in an organism, which could be possibly used to improve anticancer drug delivery. Here we present a modified method of sulfonation-induced chain scission allowing direct and accurate control over the Mw of DXA without increasing its polydispersity. Prepared DXA derivatives (Mw = 10-185 kDa) have been conjugated to cisplatin and the Mw of the carrier found to have a significant impact on cisplatin release rates, in vitro cytotoxicity, and migrastatic potential. Conjugates with the high-Mw DXA showed particularly increased anticancer efficacy. The best conjugate was four times more effective against malignant prostatic cell lines than free cisplatin and significantly inhibited the ovarian cancer cell migration. This was traced to the characteristics of spontaneously formed cisplatin-crosslinked DXA nanogels influenced by Mw of DXA and amount of loaded cisplatin.

Mechanism of sulfonation-induced chain scission of selectively oxidized polysaccharides.

Oxidation of polysaccharides to 2,3-dicarboxypolysaccharides is a two-stage process, where selective oxidation by periodate is followed by secondary oxidation by chlorite. Addition of sulfamic acid before the secondary oxidation influences the molecular weight and degree of oxidation of the product. Here, mechanism of sulfamic acid-catalysed chain scission is elucidated for selectively oxidized cellulose and dextrin. Initially, sulfamic acid sulfonates the aldehyde groups of 2,3-dialdehydepolysaccharide. Introduced -SO3H groups are in ideal position to protonate the oxygen atom of 1-4' glycosidic bond and to trigger acidic hydrolysis. This can be used to obtain a direct control over the molecular weight of the product. Observed slightly lower degree of oxidation was ascribed to the ability of sulfamic acid to scavenge the hypochlorite and thus protect the intermolecular hemiacetals from oxidation. Usually undesirable hypochlorite thus seems to be necessary for preparation of selectively oxidized polysaccharides with degree of oxidation above 90%.

The formation mechanism of iron oxide nanoparticles within the microwave-assisted solvothermal synthesis and its correlation with the structural and magnetic properties.

Magnetic nanoparticles based on Fe3O4 were prepared by a facile and rapid one-pot solvothermal synthesis using FeCl3·6H2O as a source of iron ions, ethylene glycol as a solvent and NH4Ac, (NH4)2CO3, NH4HCO3 or aqueous NH3 as precipitating and nucleating agents. In contrast to previous reports we reduce the synthesis time to 30 minutes using a pressurized microwave reactor without the requirement of further post-treatments such as calcination. Dramatically reduced synthesis time prevents particle growth via Ostwald ripening thus the obtained particles have dimensions in the range of 20 to 130 nm, they are uniform in shape and exhibit magnetic properties with saturation magnetization ranging from 8 to 76 emu g(-1). The suggested method allows simple particle size and crystallinity tuning resulting in improved magnetic properties by changing the synthesis parameters, i.e. temperature and nucleating agents. Moreover, efficiency of conversion of raw material into the product is almost 100%.

The electrorheological behavior of suspensions based on molten-salt synthesized lithium titanate nanoparticles and their core-shell titanate/urea analogues.

This paper concerns the preparation of novel electrorheological (ER) materials using microwave-assisted synthesis as well as utilizing a suitable shell-providing system with enhanced ER performance. Lithium titanate nanoparticles were successfully synthesized, and their composition was confirmed via X-ray diffraction. Rheological properties were investigated in the absence as well as in the presence of an external electric field. Dielectric properties clarified the response of the particles to the application of an electric field. The urea-coated lithium titanate nanoparticle-based suspension exhibits higher ER performance in comparison to suspensions based on bare particles.

Ultraviolet photoinduced weak bonds in aryl-substituted polysilanes.

The susceptibility of aryl-substituted polysilylenes to photodegradation by ultraviolet (UV) radiation is examined on the prototypical materials poly[methyl(phenyl)silylene] (PMPSi) and poly[(biphenyl-4-yl)methylsilylene] (PBMSi). We extend the scope of our last paper (Schauer et al 2004 Polym. Degrad. Stabil. 84 383) with the elucidation of the degradation mechanisms for two different degradation wavelengths: 266 and 355 nm. The main purpose of this paper was to study photoluminescence (PL) after major degradation, predominantly in long-wavelength range 400-600 nm, studying the disorder, dangling bonds (DBs) and weak bonds (WBs) created by the degradation process. We claim that the PL of the 500-600 nm band is related to the existence of WBs on the Si chain and originates in the σ(*)-σ exciton migration at room temperature by diffusion, free electron-hole formation, trapping in WBs and subsequent radiative recombination by tunnelling. Increase of the normalized PL 520-540 nm band after UV degradation can be then evaluated as the increase of the density of states (DOS) of WBs. The efficiency of the WB creation in PMPSi is greater for 266 nm irradiation, supporting the notion of the suppressed exciton transport compared to the less energetical photon of 355 nm, where the WB creation is lowered due to the exciton migration to longer segments and/or already existing defects. For PBMSi the WB creation kinetics for 355 nm degradation is similar to that of PMPSi. The 266 nm degradation results then support the model calculations of DB and WB reconstruction in the more rigid Si skeleton.