Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.

Development and validation of a microbiological assay for determination of chlorhexidine digluconate in aqueous solution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The role of Bi2O3 on the thermal, structural, and optical properties of tungsten-phosphate glasses

Glasses in the ternary system (70 - x)NaPO3-30WO 3-xBi2O3, with x = 0-30 mol %, were prepared by the conventional melt-quenching technique. X-ray diffraction (XRD) measurements were performed to confirm the noncrystalline nature of the samples. The influence of the Bi2O3 on the thermal, structural, and optical properties was investigated. Differential scanning calorimetry analysis showed that the glass transition temperature, Tg, increases from 405 to 440 C for 0 ≤ x ≤ 15 mol % and decreases to 417 C for x = 30 mol %. The thermal stability against devitrification decreases from 156 to 67 C with the increase of the Bi2O3 content. The structural modifications were studied by Raman scattering, showing a bismuth insertion into the phosphate chains by Bi-O-P linkage. Furthermore, up to 15 mol % of Bi 2O3 formation of BiO6 clusters is observed, associated with Bi-O-Bi linkage, resulting in a progressive break of the linear phosphate chains that leads to orthophosphate Q0 units. The linear refractive index, n0, was measured using the prism-coupler technique at 532, 633, and 1550 nm, whereas the nonlinear (NL) refractive index, n 2 was measured at 1064 nm using the Z-scan technique. Values of 1.58 ≤ n0 ≤ 1.88, n2 ≥ 10-15 cm 2/W and NL absorption coefficient, α2 ≤ 0.01 cm/GW, were determined. The linear and NL refractive indices increase with the increase of the Bi2O3 concentration. The large values of n0 and n2, as well as the very small α2, indicate that these materials have large potential for all-optical switching applications in the near-infrared. © 2012 American Chemical Society.

Clastogenicity of landfarming soil treated with sugar cane vinasse

The addition of nutrients and/or soil bulking agents is used in bioremediation to increase microbial activity in contaminated soils. For this purpose, some studies have assessed the effectiveness of vinasse in the bioremediation of soils contaminated with petroleum waste. The present study was aimed at investigating the clastogenic/aneugenic potential of landfarming soil from a petroleum refinery before and after addition of sugar cane vinasse using the Allium cepa bioassay. Our results show that the addition of sugar cane vinasse to landfarming soil potentiates the clastogenic effects of the latter probably due the release of metals that were previously adsorbed into the organic matter. These metals may have interacted synergistically with petroleum hydrocarbons present in the landfarming soil treated with sugar cane vinasse. We recommend further tests to monitor the effects of sugar cane vinasse on soils contaminated with organic wastes. © 2012 Springer Science+Business Media B.V.

Assessment of the genotoxicity of two agricultural residues after processing by diplopods using the Allium cepa assay

Agroindustrial by-products and residues from treatment of sewage sludge have been recently recycled as soil amendments. This study was aimed at assessing toxic potential of biosolid, obtained from a sewage treatment plant (STP), vinasse, a by-product of the sugar cane industry, and a combination of both residues using Allium cepa assay. Bioprocessing of these samples by a terrestrial invertebrate (diplopod Rhinocricus padbergi) was also examined. Bioassay assembly followed standards of the Brazilian legislation for disposal of these residues. After adding residues, 20 diplopods were placed in each terrarium, where they remained for 30 days. Chemical analysis and the A. cepa assay were conducted before and after bioprocessing by diplopods. At the end of the bioassay, there was a decrease in arsenic and mercury. For the remaining metals, accumulation and/or bioavailability varied in all samples but suggested bioprocessing by animals. The A. cepa test revealed genotoxic effects characterized by different chromosome aberrations. Micronuclei and chromosome breaks on meristematic cells and F1 cells with micronuclei were examined to assess mutagenicity of samples. After 30 days, the genotoxic effects were significantly reduced in the soil + biosolid and soil + biosolid + vinasse groups as well as the mutagenic effects in the soil + biosolid + vinasse group. Similar to vermicomposting, bioprocessing of residues by diplopods can be a feasible alternative and used prior to application in crops to improve degraded soils and/or city dumps. Based on our findings, further studies are needed to adequately dispose of these residues in the environment. © 2013 Springer Science+Business Media Dordrecht.

Aspectos fundamentais no desenvolvimento de sistemas microemulsionados contendo anfotericina B para uso oftálmico

As occurs with a number of drugs, the bioavailability of amphotericin B (AmB) used to treat fungal infections by the ocular route remains a great challenge to research scientists. In fact, the poor bioavailability of AmB is due mainly to the corneal barrier, which leads to a precorneal loss and consequent decrease in the absorption of this drug into the intraocular tissues. The toxicity associated with this molecule, together with its poor ability to penetrate the intact corneal epithelium, also represents a major drawback to its clinical use. New effective and safe drug vehicles for ocular delivery of AmB are therefore urgently needed. Microemulsions (MEs) seem to be an interesting system, owing to their transparent appearance, thermodynamic stability and favorable viscosity. Knowledge of the process of formation of AmB-containing MEs, as well as a good understanding of the physical chemistry of such systems, would provide reliable information on the best conditions for the use of these systems as eye drops. The goal of this research was thus to make an approach to this subject by reviewing the main studies on the use of MEs as delivery systems for AmB in topical eye treatment.

Structural and Phylogenetic Studies with MjTX-I Reveal a Multi-Oligomeric Toxin - a Novel Feature in Lys49-PLA2s Protein Class

The mortality caused by snakebites is more damaging than many tropical diseases, such as dengue haemorrhagic fever, cholera, leishmaniasis, schistosomiasis and Chagas disease. For this reason, snakebite envenoming adversely affects health services of tropical and subtropical countries and is recognized as a neglected disease by the World Health Organization. One of the main components of snake venoms is the Lys49-phospholipases A2, which is catalytically inactive but possesses other toxic and pharmacological activities. Preliminary studies with MjTX-I from Bothrops moojeni snake venom revealed intriguing new structural and functional characteristics compared to other bothropic Lys49-PLA2s. We present in this article a comprehensive study with MjTX-I using several techniques, including crystallography, small angle X-ray scattering, analytical size-exclusion chromatography, dynamic light scattering, myographic studies, bioinformatics and molecular phylogenetic analyses.Based in all these experiments we demonstrated that MjTX-I is probably a unique Lys49-PLA2, which may adopt different oligomeric forms depending on the physical-chemical environment. Furthermore, we showed that its myotoxic activity is dramatically low compared to other Lys49-PLA2s, probably due to the novel oligomeric conformations and important mutations in the C-terminal region of the protein. The phylogenetic analysis also showed that this toxin is clearly distinct from other bothropic Lys49-PLA2s, in conformity with the peculiar oligomeric characteristics of MjTX-I and possible emergence of new functionalities inresponse to environmental changes and adaptation to new preys. © 2013 Salvador et al.

Hydrostatic and [001] uniaxial pressure on anatase TiO2 by periodic B3LYP-D* calculations

The effect of high hydrostatic and [001] uniaxial pressures on TiO 2 anatase was studied under the framework of periodic calculations with the inclusion of DFT-D2 dispersion potential adjusted for this system (B3LYP-D*). The role of dispersion in distorted unit cells was evaluated in terms of lattice parameters, elastic constants, equation of state, vibrational properties, and electronic properties (band structure and density of states). A more reliable description at high pressures was achieved because the B3LYP-D* presented an improvement in all properties for undistorted bulk over conventional B3LYP and B3LYP-D. From density of states analysis, we observed that the contribution of crystalline orbitals to the edge of valence and conduction bands changed within applied pressure. The studied distortions can give some insight into behavior of electronic and structural properties due to local stress in anatase bulk from doping, defects, and physical tensions in nanometric forms. © 2013 American Chemical Society.

Nasal administration of liquid crystal precursor mucoadhesive vehicle as an alternative antiretroviral therapy

The purpose of this study was to develop a mucoadhesive stimuli-sensitive drug delivery system for nasal administration of zidovudine (AZT). The system was prepared by formulating a low viscosity precursor of a liquid crystal phase, taking advantage of its lyotropic phase behavior. Flow rheology measurements showed that the formulation composed of PPG-5-CETETH-20, oleic acid and water (55, 30, 15% w/w), denominated P, has Newtonian flow behavior. Polarized light microscopy (PLM) revealed that formulation P is isotropic, whereas its 1:1 (w/w) dilution with artificial nasal mucus (ANM) changed the system to an anisotropic lamellar phase (PD). Oscillatory frequency sweep analysis showed that PD has a high storage modulus (G′) at nasal temperatures. Measurement of the mucoadhesive force against excised porcine nasal mucosa or a mucin disk proved that the transition to the lamellar phase tripled the work of mucoadhesion. Ex vivo permeation studies across porcine nasal mucosa exhibited an 18-fold rise in the permeability of AZT from the formulation. The Weibull mathematical model suggested that the AZT is released by Fickian diffusion mechanisms. Hence, the physicochemical characterization, combined with ex vivo studies, revealed that the PPG-5-CETETH-20, oleic acid, and water formulation could form a mucoadhesive matrix in contact with nasal mucus that promoted nasal absorption of the AZT. For an in vivo assessment, the plasma concentrations of AZT in rats were determined by HPLC method following intravenous and intranasal administration of AZT-loaded P formulation (PA) and AZT solution, respectively, at a dose of 8 mg/kg. The intranasal administration of PA resulted in a fast absorption process (Tmax = 6.7 min). Therefore, a liquid crystal precursor formulation administered by the nasal route might represent a promising novel tool for the systemic delivery of AZT and other antiretroviral drugs. In the present study, the uptake of AZT absorption in the nasal mucosa was demonstrated, providing new foundations for clinical trials in patients with AIDS. © 2012 Elsevier B.V. All rights reserved.

Morphological modifications and surface amorphization in ZnO sonochemically treated nanoparticles

Application of nanoscale materials in photovoltaic and photocatalysis devices and photosensors are dramatically affected by surface morphology of nanoparticles, which plays a fundamental role in the understanding of the physical and chemical properties of nanoscale materials. Zinc oxide nanoparticles with an average size of 20 nm were obtained by the use of a sonochemical technique. X-ray diffraction (XRD) associated to Rietveld refinements and transmission electron microscopy (TEM) were used to study structural and morphological characteristics of the samples. An amorphous shell approximately 10 nm thick was observed in the ultrasonically treated sample, and a large reduction in particle size and changes in the lattice parameters were also observed. © 2012 Elsevier B.V. All rights reserved.

The effects of water molecules on the electronic and structural properties of peptide nanotubes

The self-assembly of short amino acid chains appears to be one of the most promising strategies for the fabrication of nanostructures. Their solubility in water and the possibility of chemical modification by targeting the amino or carboxyl terminus give peptide-based nanostructures several advantages over carbon nanotube nanostructures. However, because these systems are synthesized in aqueous solution, a deeper understanding is needed on the effects of water especially with respect to the electronic, structural and transport properties. In this work, the electronic properties of l-diphenylalanine nanotubes (FF-NTs) have been studied using the Self-Consistent Charge Density-Functional-based Tight-Binding method augmented with dispersion interaction. The presence of water molecules in the central hydrophilic channel and their interaction with the nanostructures are addressed. We demonstrate that the presence of water leads to significant changes in the electronic properties of these systems decreasing the band gap which can lead to an increase in the hopping probability and the conductivity. © the Owner Societies 2013.

Corneal Absorption of a New Riboflavin-Nanostructured System for Transepithelial Collagen Cross-Linking

Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion. © 2013 Bottos et al.

Desenvolvimento de métodos analíticos qualitativos para a análise de darunavir comprimidos

Darunavir is a protease inhibitor used in the treatment of HIV infection. It is a pillar of the drug cocktail for patients diagnosed with the virus. Quality control in the pharmaceutical industry, to verify the content of active substance and study the physicochemical characteristics of the drug, is essential to ensure final product quality. Until now, standardized methods for the analysis of darunavir have not been available in official compendia. This justifies new research, to develop and validate analytical methods, as well as physicochemical and pharmaceutical analysis for this drug, both as a raw material and a finished product. Thus, in this study, (a) the average weight of darunavir tablets and (b) the melting point of the pure drug were determined, and the following analytical techniques were performed: (c) thin-layer chromatography, (d) ultraviolet spectroscopy, (e) infrared spectroscopy and (f) high performance liquid chromatography. By developing the above techniques, it is possible to make a qualitative assessment of the quality of darunavir tablets.

Elucidation of carbohydrate molecular interaction mechanism of recombinant and native ArtinM

The quartz crystal microbalance (QCM) technique has been applied for monitoring the biorecognition of ArtinM lectins at low horseradish peroxidase glycoprotein (HRP) concentrations, using a simple kinetic model based on Langmuir isotherm in previous work.18 The latter approach was consistent with the data at dilute conditions but it fails to explain the small differences existing in the jArtinM and rArtinM due to ligand binding concentration limit. Here we extend this analysis to differentiate sugar-binding event of recombinant (rArtinM) and native (jArtinM) ArtinM lectins beyond dilute conditions. Equivalently, functionalized quartz crystal microbalance with dissipation monitoring (QCM-D) was used as real-time label-free technique but structural-dependent kinetic features of the interaction were detailed by using combined analysis of mass and dissipation factor variation. The stated kinetic model not only was able to predict the diluted conditions but also allowed to differentiate ArtinM avidities. For instance, it was found that rArtinM avidity is higher than jArtinM avidity whereas their conformational flexibility is lower. Additionally, it was possible to monitor the hydration shell of the binding complex with ArtinM lectins under dynamic conditions. Such information is key in understanding and differentiating protein binding avidity, biological functionality, and kinetics. © 2013 American Chemical Society.

RBPI21 interacts with negative membranes endothermically promoting the formation of rigid multilamellar structures

rBPI21 belongs to the antimicrobial peptide and protein (AMP) family. It has high affinity for lipopolysaccharide (LPS), acting mainly against Gram-negative bacteria. This work intends to elucidate the mechanism of action of rBPI21 at the membrane level. Using isothermal titration calorimetry, we observed that rBPI21 interaction occurs only with negatively charged membranes (mimicking bacterial membranes) and is entropically driven. Differential scanning calorimetry shows that membrane interaction with rBPI21 is followed by an increase of rigidity on negatively charged membrane, which is corroborated by small angle X-ray scattering (SAXS). Additionally, SAXS data reveal that rBPI21 promotes the multilamellarization of negatively charged membranes. The results support the proposed model for rBPI21 action: first it may interact with LPS at the bacterial surface. This entropic interaction could cause the release of ions that maintain the packed structure of LPS, ensuring peptide penetration. Then, rBPI21 may interact with the negatively charged leaflets of the outer and inner membranes, promoting the interaction between the two bacterial membranes, ultimately leading to cell death. © 2013 Elsevier B.V.