Electrospray induced surface activation of polystyrene microbeads for diagnostic applications.

Electrospray is generally regarded as a "soft" technique due to the absence of any observable molecular fragmentation or destruction. This study reports on a novel and easy way to induce surface activation on the surface of polystyrene microbeads through electrospray deposition into a grounded aqueous electrolyte solution bath. This process, nicknamed EISA, which stands for electrospray induced surface activation, proposes that when a highly charged microbead formed by the electrospray process sinks into the aqueous electrolyte solution, it behaves like a highly charged spherical capacitor that discharges in the conductive liquid. The energy released leads to a breakup of the polystyrene surface bonds and water oxidation with oxygen. Further reactions produce a carboxylated surface that was confirmed by X-ray photoelectron spectroscopy (XPS) and protein coupling. An immunoassay based on these modified microbeads was also developed and presented for use in syphilis detection, demonstrating a reliable signal-to-noise ratio between positive and negative results.

Bioactive nanocomposites of bacterial cellulose and natural hydrocolloids.

The aim of this work was to develop bioactive films from bacterial cellulose and hydrocolloids (guar gum and hyaluronic acid), coated or not with collagen. After mechanical treatment, a suspension of cellulose nanofibres was obtained which, combined with the dispersions of hydrocolloids, was used to produce bionanocomposite films by wet casting. The materials were stable in physiological solution and presented better swelling capacity than that of the bacterial cellulose. The films were coated with collagen by dipping. Cell adhesion tests and surface analysis by tensiometry, X-ray photoelectron spectroscopy and atomic force microscopy showed that the surface properties of the films can be adjusted by changing the proportions of the components. The collagen coating presented a self-assembling pattern resembling that of living tissues. The materials developed in this work showed potential for applications in the medical field as bioactive wound dressings, scaffolds for cellular growth and sustained drug release systems. The films were obtained by simple production and purification methods, including the use of low toxicity solvents. Thus, in addition to potential cost saving, the development of these bionanocomposites is in accordance with green chemistry principles.

Synthesis of TiO2 nanocrystals with a high affinity for amine organic compounds.

This article describes a different approach to the colloidal synthesis of TiO(2) nanocrystals using a polymer melt as a solvent. This approach allowed us to obtain a colloidal dispersion with a high degree of stability in a polymeric solvent, resulting in a transparent colloid. Using this method, it was possible to obtain the TiO(2) nanocrystal with Brønsted acid sites and polymer chains chemically anchored on the nanocrystal surface. The acid surface of those nanocrystals has the chemical property to react in the presence of amine organic compounds and to maintain the colloidal stability. In this way, TiO(2) nanocrystals were combined with a molecular probe containing amine functional groups such as polyaniline. Through the combination of the molecular probe and inorganic nanocrystals, we obtained a hybrid material with interesting chemical, optical, and electronic behavior, making it a promising material for photovoltaic, photochromic, and sensor devices.

Intercalation of an oxalatooxoniobate complex into layered double hydroxide and layered zinc hydroxide nitrate.

A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH(4)[NbO(C(2)O(4))(2)(H(2)O)(2)]2H(2)O. In a similar way, the layered zinc hydroxide nitrate, Zn(5)(OH)(8)(NO(3))(2)2H(2)O, was synthesized, preexpanded with azelate ions ((-)OOC(CH(2))(7)COO(-)), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV-vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix.