Bioactive glasses as carriers for bioactive molecules and therapeutic drugs: a review

Bioactive glasses (BG) show great promise for bone tissue engineering based on their key properties, e.g., biocompatibility, biodegradability, osteoconductivity as well as osteogenic and angiogenic potential, which make them excellent candidates for bone tissue scaffolds and bone substitute materials. Recent work has shown that dissolution products of bioactive glasses have the potential to induce angiogenesis in addition to their known effect of influencing gene expression and promoting osteoblastic differentiation. One of the most interesting features of BG is their ability to bond both to soft and hard tissues, depending on their composition. To intensify the positive impact of BG for medical applications, there are considerable research efforts on using bioactive glass based platforms as carriers for the encapsulation, delivery and controlled release of bioactive molecules and therapeutic drugs. Different types of bioactive glasses have been considered in combination with different therapeutic drugs, hormones, growth factors and peptides. Using bioactive glasses as drug delivery system combines thus the effectiveness of therapeutic drugs (or bioactive/signaling molecules) with the intrinsic advantages of this inorganic biomaterial. Considering research carried out in the last 15?years, this review presents the different chemical compositions and morphologies of bioactive glasses used as carrier for bioactive molecules and therapeutic drugs and discusses the expanding potential of BG with drug delivery capability focusing in the field of bone tissue engineering.     

Temporal trends and controlling factors for polychlorinated biphenyls in the UK atmosphere (1991-2008)

Long-term air monitoring data sets are needed for persistent organic pollutants (POPs), to assess the effectiveness of source abatement measures and the factors controlling ambient levels. The Toxic Organic Micro-Pollutants (TOMPS) program in the United Kingdom started in 1991, generating a data set for polychlorinated biphenyls (PCBs). The history and volumes of production, usage, and subsequent restrictions on PCBs in the UK are well-characterized relative to many countries, providing a valuable case study on the effectiveness of controls and the factors influencing ambient levels and trends of these "model POPs". PCB air concentrations (congeners PCB 28, 52, 90/101, 118, 138, 153, and 180) from six rural and urban monitoring sites are presented. Most show a statistically significant decrease in PCBs levels over time, consistent with estimates of emissions, helping to validate emissions inventories. Times for a 50% decline in concentrations (sometimes called clearance rates) averaged 4.7 ± 1.6 years for all congeners at all sites. The trends at different sites and for different congeners were not statistically different from each other. Concentration differences between sites are correlated with local population density (i.e., the degree of urbanization), which supports approaches to modeling of primary emissions on the national and regional scale. The data set indicates that ambient levels and underlying trends of PCBs continue to reflect the controlling influence of diffuse primary sources from the ongoing stock of PCBs in urban environments. Production and use restrictions came into force in the UK over 40 years ago; trends since monitoring began in the early 1990s should be seen as part of a continuing decline in ambient levels since that time.     

Validation of scales measuring attitudes and norms related to mammography screening in women veterans.

Validation of psychosocial measures for use in mammography screening research has been given inadequate attention in the literature. The authors report on the validation of 5 measures examining 4 attitudinal constructs (i.e., pros, cons, outcome expectations, and cancer worries) and 1 social influence construct (i.e., subjective norms) in a 22-item inventory. The study participants consisted of a national, randomly sampled population of women veterans (n = 2,910). After minor revision of scales, the authors found independent measures for 4 constructs: pros, cons, cancer worries, and subjective norms. The authors concluded that these scales have acceptable psychometric properties; support construct validity; and provide brief, reliable, and valid measures of attitudes toward and norms regarding mammography screening. These scales may be useful for intervention research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis, Structure Determination, and Aqueous Durability of Cs2ZrSi3O9

The structure of Cs₂ZrSi₃O₉ synthesized using a sol–gel method was determined from the Rietveld refinement of experimental powder X-ray diffraction data. The refinement confirmed that this compound was isostructural with wadeite: its structure was hexagonal (space group P 6₃/ m ), and its lattice parameters were a = 7.2303(2) Å and c = 10.2682(4) Å. The aqueous durability of Cs₂ZrSi₃O₉ varied, depending on the solution conditions. In modified leach tests with buffered (pH 7) and unbuffered solutions, the 7-d cesium release rates were <1.2 × 10⁻⁴ g·(m²·day)⁻¹, which indicated high aqueous durability. However, in unsaturated, unbuffered solutions with a pH of 9–10, the durability was much lower, with 7-d cesium release rates of 2.2 × 10⁻³ g·(m²·day)⁻¹. The ability of this material to retain cesium in aqueous environments can be explained by its condensed ring structure, in which the size of the channel openings is smaller than the diameter of a Cs⁺ ion. However, dissolution of the network silicate occurred at high pH, which resulted in the release of cesium.     

Early attentional deficits in an attention-to-prepulse paradigm in ADHD adults.

Adults with attention-deficit/hyperactivity disorder (ADHD) were examined for early and late attentional processes as a function of controlled attention. The test paradigm was the attentional modulation of prepulse inhibition (PPI; early controlled attentional processing) and prepulse facilitation (PPF; late controlled attentional processing). In 49 patients and 49 controls, the authors measured acoustic startle responses to 96-dB startle pulses preceded 120, 240 (for PPI), 2,000, and 4,500 (for PPF) ms by a 68-dB prepulse noise. Geometric figures signaled that prepulses were to be ignored or attended to (automatic vs. controlled attention). ADHD patients exhibited deficits in prepulse modulation, but these reflected an interaction of controlled attention and time of information processing. Normal PPI and PPF occurred under all conditions except for controlled attentional modulation of PPI. Attention deficits in ADHD patients may reflect not general derangements in information processing or ability to attend but, rather, selective disturbances of controlled attention during early information processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of magnetic nanoparticles performance as photocatalyst for the catalytic treatment of direct red 28 dye in synthetic and real water effluents

Integrated water resources management practice is gaining popularity as an alternative water source due to the limited supply of freshwater. The present study was carried out on the photocatalytic degradation of Direct red 28 (DR-28) dye using magnetic nanoparticles (MNPs; Fe₃O₄) as a photocatalyst. The study was conducted on the photocatalytic degradation of DR-28 dye in synthetic dye effluent water, to understand the effects of different photoreaction parameters on the degradation kinetics. The influence of different parameters such as time, amount of photocatalyst, concentration of H₂O₂ and pH was investigated. At the optimum dosage of MNPs (0.6?g/L) with 4?mmol/L of H₂O₂, significant photocatalytic degradation of DR-28 dye (93.2%) was observed. The kinetic study revealed that the photocatalytic degradation followed pseudo-first-order kinetics. The degradation performance of Fe₃O₄ nanoparticles as a photocatalyst for DR-28 dye was compared with titanium dioxide (TiO₂) and it was found that the performance of Fe₃O₄ as a photocatalyst is superior to TiO₂ photocatalyst. The real dye effluent was also degraded at optimum conditions and promising results were achieved.     

Precision thickness and refractive index imaging of molecular films

We present an interferometric contrasting technique that allows visualizing the thickness and refractive index of a molecular film being part of an optical multilayer structure (etalon). Small wavelength shifts of the comblike etalon spectrum are transformed into measurable intensity variations using a second reference etalon (optical correlator), illuminated in series. A charge-coupled device camera acting as two-dimensional photometer is utilized to measure the optical spectral correlation (OSC) image. The performance of the here proposed optical spectral correlation method is demonstrated using very thin confined liquid films. We give a detailed signal-to-noise analysis. Subangstrom film thickness resolution is experimentally verified with single exposure images acquired at frame rates comparable to video standards (approximately 25 Hz). Finally, we describe the calibration procedures necessary to obtain an absolute quantification of the OSC image.