Microstructuration of poly(3-hexylthiophene) leads to bifunctional superhydrophobic and photoreactive surfaces.

In this paper, we present the first report on an organic conducting polymer film, which alone exhibits both superhydrophobicity and visible light photoactivity. The microstructure of poly(3-hexylthiophene) was optimized using controlled precipitation until superhydrophobic behavior was achieved. Photocatalytic tests employing visible light irradiation proved that polymer degrades the ethanol test molecule.

Nonactivated titanium-dioxide nanoparticles promote the growth of Chlamydia trachomatis and decrease the antimicrobial activity of silver nanoparticles.

AIMS: Chlamydia trachomatis and herpes simplex virus (HSV) are the most prevalent bacterial and viral sexually transmitted infections. Due to the chronic nature of their infections, they are able to interact with titanium-dioxide (TiO2 ) nanoparticles (NPs) applied as food additives or drug delivery vehicles. The aim of this study was to describe the interactions of these two prevalent pathogens with the TiO2 NPs. METHODS AND RESULTS: Chlamydia trachomatis and HSV-2 were treated with nonactivated TiO2 NPs, silver NPs and silver decorated TiO2 NPs before infection of HeLa and Vero cells. Their intracellular growth was monitored by quantitative PCR. Unexpectedly, the TiO2 NPs (100 µg ml-1 ) increased the growth of C. trachomatis by approximately fourfold, while the HSV-2 replication was not affected. Addition of TiO2 to silver NPs decreased their antimicrobial activity against C. trachomatis up to 27·92-fold. CONCLUSION: In summary, nonactivated TiO2 NPs could increase the replication of C. trachomatis and decrease the antimicrobial activity of silver NPs. SIGNIFICANCE AND IMPACT OF THE STUDY: The food industry or drug delivery use of TiO2 NPs could enhance the growth of certain intracellular pathogens and potentially worsen disease symptoms, a feature that should be further investigated.

Comprehensive study on the structure of the BSA from extended-to aged form in wide (2-12) pH range.

In this work we studied the structure of the bovine serum albumin (BSA) and the protein-ligand interactions since researchers prefer to use them as carriers in drug delivery systems. Systematic study (between pH 2-12, in double distilled water and physiological salt solution) was carried out to determine the changes in the secondary and the tertiary structures of the BSA, the apparent molecular weight (Mw), the size (dLS) and the electrokinetic potential (ζ). At pH 7, the BSA has higher stability in the absence (ζ=-69mV, dLS=2.2nm, A2=1.4×10(-3)mlmol/g(2)) than in the presence of salt solution (ζ=-2.4mV, dLS=5.3nm, A2=-3.2×10(-4)mlmol/g(2)). The Mw strongly depends on the pH and the ionic strength (at pH 3 in the absence of salt, the Mw is 54.6kDa while in the presence of salt is 114kDa) which determines the geometry of the protein. The protein-ligand interactions were characterized by fluorescence (FL) and isothermal microcalorimetry (ITC) methods; these independent techniques provided similar thermodynamic parameters such as the binding constant (K) and the Gibbs free energy (ΔG).

Targeting of the kynurenic acid across the blood-brain barrier by core-shell nanoparticles.

Core-shell nanoparticles (CSNPs) were developed to get over therapeutic amount of kynurenic acid (KYNA) across the blood-brain barrier (BBB). Bovine serum albumin (BSA) was used as core for encapsulation of KYNA and the BSA/KYNA composite was finally encapsulated by poly(allylamine) hydrochloride (PAH) polymer as shell. In the interest of the optimization of the synthesis the BSA and KYNA interaction was studied by two-dimensional surface plasmon resonance (SPR) technique as well. The average size of d~100 nm was proven by dynamic light scattering (DLS) and transmission electron microscopy (TEM), while the structure of the composites was characterized by fluorescence (FL) and circular dichroism (CD) spectroscopy. The in vitro release properties of KYNA were investigated by a vertical diffusion cell at 25.0 °C and 37.5 °C and the kinetic of the release were discussed. The penetration capacity of the NPs into the central nervous system (CNS) was tested by an in vitro BBB model. The results demonstrated that the encapsulated KYNA had significantly higher permeability compared to free KYNA molecules. In the neurobiological serial of in vivo experiments the effects of peripherally administered KYNA with CSNPs were studied in comparison with untreated KYNA. These results clearly proved that KYNA in the CSNPs, administrated peripherally is suitable to cross the BBB and to induce electrophysiological effects within the CNS. As the neuroprotective properties of KYNA nowadays are proven, the importance of the results is obvious.

Determination of binding capacity and adsorption enthalpy between Human Glutamate Receptor (GluR1) peptide fragments and kynurenic acid by surface plasmon resonance experiments. Part 2: Interaction of GluR1270-300 with KYNA.

In the course of our previous work, the interactions of two peptide fragments (GluR1201-230 and GluR1231-259) of human glutamate receptor (GluR1201-300) polypeptide with kynurenic acid (KYNA) were investigated by surface plasmon resonance (SPR) spectroscopy. Besides quantitation of the interactions, the enthalpies of binding of KYNA on certain peptide fragment-modified gold surfaces were also reported. In the present work, a third peptide fragment (GluR1270-300) of the glutamate receptor was synthesized and its interaction with KYNA was investigated by an SPR technique. This 31-membered peptide was chemically bonded onto a gold-coated SPR chip via a cysteine residue. The peptide-functionalized biosensor chip was analyzed by atomic force microscopy (AFM) and theoretical calculations were performed on the structure and dimensions of the peptide on the gold surface. In order to determine the isosteric heat of adsorption of the binding of KYNA on the peptide-functionalized gold thin film, SPR experiments were carried out between +10°C and +40°C. The results on the GluR1270-300-KYNA system were compared with the previously published binding parameters of the interactions of GluR1201-230 and GluR1231-259 with KYNA. The binding abilities of KYNA with all three peptide fragments immobilized on the gold surface were estimated by a molecular docking procedure and the binding free energies of these AMPA receptor subunits with KYNA were determined.

Bovine serum albumin-sodium alkyl sulfates bioconjugates as drug delivery systems.

Precipitation of bovine serum albumin (BSA) by anionic surfactants with alkyl chains of increasing lengths (octyl, decyl, dodecyl sulfates) was studied at room temperature, at pH 3.0, in isotonic sodium chloride solution. The particle size of albumin, the zeta potential, the surface charge and fluorescent properties of BSA-surfactant composites were investigated concerning addition of increasing amount of surfactant. The thermal stability of the systems was monitored by calorimetric analysis (DSC). The formation of the well-ordered structure in the self-assembly process in liquid phase was studied by XRD measurement. The structure of the precipitated BSA-surfactant nanocomposites was characterized by small-angle X-ray scattering (SAXS). Finally, ibuprofen (IBU) molecules were enclosed in BSA-surfactant bioconjugate systems and the release properties of the drug were investigated. It has been found out that, as a consequence to the increasing number of carbon atoms in the alkyl chains of the surfactant, the structure and the fluorescent properties of the aggregates formed can be controlled due to the increase in the hydrophobicity of BSA-surfactant composites. The bioconjugates are well applicable as carrier to realize controlled release of drug molecules.

Determination of binding capacity and adsorption enthalpy between Human Glutamate Receptor (GluR1) peptide fragments and kynurenic acid by surface plasmon resonance experiments.

The interaction between kynurenic acid (KYNA) and two peptide fragments (ca. 30 residues) of Human Glutamate Receptor 201-300 (GluR1) using surface plasmon resonance (SPR) spectroscopy was investigated. Because of the medical interest in the neuroscience, GluR1 is one of the important subunits of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR). AMPARs are ionotoropic glutamate receptors, which are mediating fast synaptic transmission and are crucial for plasticity in the brain. On the other hand, KYNA has been suggested to have neuroprotective activity and it has been considered for apply in therapy in certain neurobiological disorders. In this article the adsorption of the GluR1201-230 and GluR1231-259 peptides were studied on gold biosensor chip. The peptides were chemically bonded onto the gold surface via thiol group of L-cysteine resulted in the formation of peptide monolayer on the SPR chip surface. Because the GluR1231-259 peptide does not contain L-cysteine the Val256 was replaced by Cys256. The cross sectional area and the surface orientation of the studied peptides were determined by SPR and theoretical calculations (LOMETS) as well. The binding capability of KYNA on the peptide monolayer was studied in the concentration range of 0.1-5.0 mM using 150 mM NaCl ionic strength at pH 7.4 (±0.02) in phosphate buffer solutions. In order to determine the binding enthalpy the experiments were carried out between +10°C and +40°C. The heat of adsorption was calculated by using adsorption isotherms at different surface loading of KYNA on the SPR chip.

BSA/polyelectrolyte core-shell nanoparticles for controlled release of encapsulated ibuprofen.

Bovine serum albumin (BSA) based core-shell nanoparticles were developed as carrier systems for drug transportation. At pH=3, the oppositely charged polyelectrolytes: poly(sodium-4-styrene)sulphonate (PSS) and the chitosan (Chit) bind to the positively charged protein via electrostatic interactions. We applied ibuprofen (IBU) as model molecule which has low solubility. The changes in the BSA's secondary structure during the steps of the synthesis were inspected by FT-IR measurements. The size and the zeta potential were determined by dynamic light scattering (DLS). The changes in the structure and in the size were investigated by small angle X-ray scattering (SAXS) too, for each composite. The release of the ibuprofen was studied by vertical diffusion cell (Franz cell) at pH 7.4 at 25 and 37.5°C. The structure of the core-shell nanoparticles have significantly changed as the pH has risen from 3.0 to 7.4. Kinetic models were used to describe the release mechanism. The experimental results demonstrated that the BSA has an ordered structure at pH=3 which will become random coil by adding ibuprofen. The first shell restores the ordered structure of the protein. The controlled release was carried out; the IBU release decreased by 40% in the case of two-layered composites compared with the "naked" BSA.

Preparation and properties of nanoscale containers for biomedical application in drug delivery: preliminary studies with kynurenic acid.

The main purpose of this study was to facilitate the delivery of kynurenic acid (KYNA) across the blood-brain barrier (BBB) by applying micelles as nanoscale containers. Non-ionic amphiphilic molecules were used for preparation of spherical micelles for delivery of kynurenic acid in aqueous solution in physiological condition. It was established that Triton X 100 and Lutensol AP 20 non-ionic surfactants are able to produce stable nanocontainers for delivery of kynurenic acid molecules. The incorporation of KYNA molecules was investigated by dynamic light scattering and the size of micelles were calculated between 5 and 10 nm in 150 mM NaCl and pH 7.5-7.6 solutions. Encapsulated kynurenic acid showed a significantly higher blood-brain barrier permeability compared with non-encapsulated kynurenic acid. The in vivo experiments showed that the encapsulated kynurenic acid is able to display effects within the central nervous system, even after its peripheral administration.

Functionalization of gold nanoparticles with amino acid, beta-amyloid peptides and fragment.

Gold nanoparticles (Au NPs) were functionalized by cysteine (Cys), beta-amyloid peptides (Cys(0)Abeta(1-28), Cys(0)Abeta(1-40), Abeta(1-42)) and a pentapeptide fragment (Leu-Pro-Phe-Phe-Asp-OH (LPFFD-OH)). Optical absorption spectra of these systems were recorded and the plasmon resonance maximum values (lambda(max)) of the UV-vis spectra together with the transmission electron microscopy (TEM) images were also analysed. Both TEM images and the appearance of a new absorption band between approximately 720 and 750 nm in the visible spectra of the Au-cysteine and Au-LPFFD-OH systems most probably indicate that upon addition of these molecules to Au NPs-containing aqueous dispersions formation of aggregates is occurred. The wavelength shift between the two observed absorption bands in cysteine- and pentapeptide-modified Au NPs systems are Deltalambda=185 and 193 nm, respectively. These results suggest that the monodisperse spherical gold nanoparticles were arranged to chained structure due to the effect of these molecules. For confirmation of the binding of citrate and cysteine onto the plasmonic metal surface (1)H NMR measurements were also performed. (1)H NMR results may suggest that the citrate layer on the metal surface is replaced by cysteine leading to a formation of organic double layer structure. In the presence of beta-amyloid peptides the aggregation was not observed, especially in the Au-Cys(0)Abeta(1-40) and Au-Abeta(1-42) systems, however compared to the cysteine or LPFFD-OH-containing gold dispersion with Cys(0)Abeta(1-28) measurable less aggregation were occurred. The spectral parameters clearly suggest that Abeta(1-42) can attach or bind to the surface of gold nanoparticles via both the apolar and the N-donors containing side-chains of amino acids and no aggregation in the colloidal gold dispersion was observed.

Acrylamide, acrylic acid and N-isopropylacrylamide hydrogels as osmotic tissue expanders.

BACKGROUND AND AIM: Osmotically active tissue expanders allow the harvesting of soft tissue for reconstruction after different injuries. However, their expansion properties could be improved. Thus, our goal was to examine the in vivo applicability of acrylamide (AAm), acrylic acid (AAc) and N- isopropylacrylamide (NIPAAm) hydrogels. MATERIALS AND METHODS: Cylinders of AAm, AAc and NIPAAm hydrogels were implanted under the skin of rats in the dorsal region. The diameter and the length of the cylinders were measured daily. After removal of the hydrogels, their mass and rheological properties were determined. Further, biopsies were taken from the adjacent tissue for histological analysis. RESULTS: The hydrogels reached the peak of swelling by the end of the 2nd postoperative week. The wet mass of the removed cylinders was 25 times their dry mass prior to implantation. NIPAAm polymers exhibited the most favourable visco-elastic properties, with the highest tendency to retain their preformed shape. The histological analysis revealed serious tissue damage when the AAc devices were used, whereas the AAm and NIPAAm did not result in such lesions. CONCLUSION: In view of its mechanical and biological properties, NIPAAm hydrogel seems to be the most appropriate of these materials for application in plastic and reconstructive surgery.

Metal ion coordination of macromolecular bioligands: formation of zinc(II) complex of hyaluronic acid.

The coordination of zinc(II) ion to hyaluronate (Hya), a natural copolymer, in aqueous solution at pH 6 was investigated by potentiometric and circular dichroism (CD) spectroscopic methods, and by monitoring the changes in macroscopic properties by high-precision measurements. The zinc(II)-selective electrode, and CD measurements proved the binding of zinc(II) by Hya. A number of Hya fragments (Mr approximately 3.3 x 10(3)-1.4 x 10(6)) were studied to estimate the contributions of the polyelectrolyte effect, the solvation and host-guest interactions to the extra stabilization of the macromolecular zinc(II) complexes as compared with the monomeric unit. The zinc(II) ion activity increase reflected a stability decrease for the fragments with Mr < 4 x 10(4). This molecular weight differs from that where cleavage of the Hya skeleton starts (approximately 5 x 10(5), according to the size-exclusion gel, and anion-exchange chromatographic behavior of the Hya fragments) and from that where the polyelectrolyte effect stops (approximately 6 x 10(3)). The excess volumes and Bingham shear yield values of the solutions revealed the transformation of the coherent random coil structure stabilized by intermolecular association in the NaHya to an intramolecular association producing the globular structure of the ZnHya molecule, with a smaller but more strongly bound solvate water sheet.

Cadmium Ion Adsorption Controls the Growth of CdS Nanoparticles on Layered Montmorillonite and Calumit Surfaces.

Adsorption isotherms have been determined for the intercalation of cadmium ions (Cd2+) into layered hydrophobized montmorillonite (HDP-M) and calumit (DBS-C) sheets dispersed in ethanol (1)-cyclohexane (2) mixtures. The amount of Cd2+ adsorbed depended strongly on the composition of the binary liquid; at an ethanol mole fraction of 0.05 (x1 = 0.05), 95% of the added Cd2+ is located in the ethanolic nanoreactor at the HDP-M (or DBS-C) surface. CdS nanoparticles have been generated in situ in ethanolic nanoreactors at the HDP-M and DBS-C surfaces. Absorption spectrophotometric measurements provided information on the number of CdS nanoparticles formed and on their absorption edges, bandgaps, and mean diameters. Good correlations have been obtained between the adsorption isotherms and the size (and the amount) of the CdS formed. X-ray diffractometry established that CdS nanoparticles stretched the HDP-M and DBS-C lamellas unevenly upon intercalation. Copyright 1999 Academic Press.

Calculation of the BET Compatible Surface Area from Any Type I Isotherms Measured below the Critical Temperature.

It may occur in practice that the nitrogen isotherm should be measured at 77 K only in order to determine the Brunauer-Emmett-Teller (BET) specific surface area [as(N2, 77)]. This fact has given cause for an elaborate method to calculate the value of as(N2, 77) from Type I isotherms measured on any adsorbents at any temperature. Since Type I isotherms are measured most often in practice the proposed method makes it possible to calculate the value of as(N2, 77) from isotherms of adsorptives which are the actual topics of the investigations. Thus, in these cases the determination of nitrogen isotherms at 77 K can be omitted. The proposed method is based on the Tóth (T) equation and on its modified and extended forms. In these equations are present the parameters chim, chio, and t with the following physical meanings: chim and chio are integral constants originating from the Gibbs equation integrated between definite limits of pressure and coverage and t is a parameter characterizing the heterogeneity of the adsorbents. The parameters chim and chio assure the thermodynamic consistence of these relationships. It is proven that the parameters (chim)1/t and (chio)1/t depend only on the structure of adsorbents (micro-, mezoporous, or smooth surfaces). These parameters, calculated from Type I isotherms measured under the critical temperature of the adsorptives, are the bases of the calculation of the BET compatible surface areas. Copyright 1999 Academic Press.

Separation of the First Adsorbed Layer from Others and Calculation of the BET Compatible Surface Area from Type II Isotherms.

In the previous paper it has been proven that a BET compatible specific surface area, asc(N2, 77), can be calculated from any Type I isotherm measured below the critical temperature. In this paper it is proven that the same calculation can be performed from any Type II isotherms if the isotherm has a pure monolayer domain. In order to distinguish the mono- and multilayer adsorption the relative free energy of the surface as a function of the adsorbed amount, pir(ns), and the functions psi(pr) and psi(ns) are applied, both defined by the differential expression (ns/pr)(dpr/dns). When the multilayer adsorption becomes the dominant process then the function pir(ns) has a point of inflexion and functions psi(pr) and psi(ns) have maximum values. It has been demonstrated that in most of the Type II isotherms the mono- and multilayer domains can be separated, so the monolayer component isotherm can be calculated by the T (Tóth) equation. Therefore, it is possible to calculate the BET compatible specific surface area discussed in detail in the previous paper. It has also been proven that there are Type II isotherms which describe only multilayer adsorption; i.e., the functions psi(pr) and psi(ns) do not have maximum values. In these cases the Harkins-Jura equation should be applied. Copyright 1999 Academic Press.

The Effect of Cadmium Ion Adsorption on the Growth of CdS Nanoparticles at Colloidal Silica Particle Interfaces in Binary Liquids

Adsorption isotherms have been determined for the binding of Cd2+ onto the surfaces of hydrophilic A200 SiO2 and hydrophobic R972 SiO2 particles dispersed in ethanol (1>)-cyclohexane (2) mixtures at ethanol mole fractions of x1 = 0.05, 0.10, 0.20, and 0.40. CdS nanoparticles have been generated in situ within the ethanolic nanoreactors at surfaces of SiO2 particles in the different ethanol-cyclohexane binary liquids by the addition of hydrogen sulfide. Absorption spectra of the CdS particles provided information on their quantity, absorption edges, optical band gaps, and mean diameters. Good correlations have been obtained between the adsorption isotherms and size of the CdS particles as well as between the adsorption isotherms and the amount of CdS formed. The smallest CdS particles (ca. 6 nm diameter) have been obtained on the surfaces of SiO2 particles dispersed in ethanol (1>)-cyclohexane (2) mixtures at ethanol mole fractions of x1 = 0.05. More CdS particles have been observed to coat the hydrophilic A200 SiO2 than the hydrophobic R972 particles. In the x1 = 0.10 ethanol (1)-cyclohexane (2) liquid mixtures up to 10% of the SiO2 surface can be covered by CdS nanoparticles. Immersion wetting enthalpy measurements in methanol established the surface of the SiO2 particles to be hydrophilic, which became partially hydrophobic upon and the binding of cadmium ions and hence upon the subsequent formation of CdS. Copyright 1997 Academic Press. Copyright 1997Academic Press