Spanish validation of the HIV dementia scale in women

HIV infection is increasing in minority groups, particularly in African American and Hispanic women. Although the incidence of HIV dementia has decreased since the advent of highly active antiretroviral treatment, prevalence of neurocognitive complications has increased as patients are now living longer. This study's purpose was to determine the psychometric properties of the Spanish-language HIV Dementia Scale (HDS) in a group of HIV-infected women. We recruited 96 women: 60 HIV-seropositive and 36 HIV-seronegative. Modification of the HDS into a Spanish-language version consisted of translating the instructions, substituting four words in Spanish (gato, media, azul, pi?a), increasing 1 second in the psychomotor speed because the Spanish alphabet has more letters than the English alphabet, and not offering clues for memory recall. Cognitive impairment (CI) was defined according to the modified American Academy of Neurology HIV-dementia criteria including an asymptomatic CI group. Statistical analysis consisted of analysis of variance to determine group differences and receiver operator characteristics (ROC) to determine the optimal cutoff point for the screening of CI. HDS-Spanish total score and subscores for psychomotor speed and memory recall showed significant differences between HIV-seronegative and women with HIV-dementia (p < 0.001) and between HIV-seropositive women with normal cognition and those with HIV-dementia (p < 0.001). The optimal cutoff point of 13 or less had performance characteristics of 87% sensitivity and 46% specificity for HIV-associated CI (50.0% positive predictive value, 85.0% negative predictive value). The HDS-Spanish translation offers a useful screening tool with value for the identification of Hispanic women at risk of developing HIV-associated symptomatic neurocognitive disturbances.     

Transparent micro- and nanopatterned poly(lactic acid) for biomedical applications

The formation of structures in poly(lactic acid) has been investigated with respect to producing areas of regular, superficial features with dimensions comparable to those of cells or biological macromolecules. Nanoembossing, a novel method of pattern replication in polymers, has been used for the production of features ranging from tens of micrometers, covering areas up to 1 cm(2), down to hundreds of nanometers. Both micro- and nanostructures are faithfully replicated. Contact-angle measurements suggest that positive microstructuring of the polymer (where features protrude from the polymer surface) produces a more hydrophilic surface than negative microstructuring. The ability to structure the surface of the poly(lactic acid), allied to the polymer's postprocessing transparency and proven biocompatibility, means that thin films produced in this way will be useful for bioengineers studying the interaction of micro- and nanodimensioned features with biological specimen, with regard to tissue engineering, for example.     

Material characterization and in vivo behavior of silicon substituted alpha-tricalcium phosphate cement

The possibility and biological effects of substituting silicon in alpha-tricalcium phosphate (alpha-TCP) by way of solid-state reaction have been evaluated. alpha-TCP powders with varying substitution amounts (1 and 5 mol % Ca2SiO4) were synthesized by reacting mixtures of CaCO3, Ca2P2O7, and SiO2, at a rate of 4 degrees C(min)(-1) to 1100 degrees C, left to dwell for 2 h and then heated to 1325 degrees C at 4 degrees C(min)(-1) and left to dwell for a period of 4 h. The powders were then rapidly quenched in air. Si incorporation could be verified by X-ray diffraction analysis, indicating an increase of the lattice volume with increasing Si content from 4284.1(8) to 4334(1) A3 for pure alpha-TCP and alpha-Si5%TCP, respectively. The hydrolysis of milled alpha-SiTCP powders was monitored by isothermal calorimetry, and the compressive strength of set cements was tested. The results showed changes in speed and amount of heat released during reactivity tests and a decrease in mechanical strength (60, 50, and 5 MPa) with increasing Si content. In vitro bioactivity of the set cements after soaking in simulated body fluid for 4 weeks was also tested. The formation of a bonelike apatite layer on the surface of the set cements could be observed and was thickest for 1%Si (20 microm). These results were in good agreement with the in vivo studies performed, which showed strong evidence that the cement containing 1% silicon doped alpha-TCP enhanced mesenchymal cell differentiation and increased osteoblast activity compared with alpha-TCP.     

Bioceramics as nanomaterials

Nanostructured materials possess unique capabilities for specific interactions with biological entities. This article reviews several types of nanostructured ceramics, cements and coatings that are being considered for use in medical applications. The processing methods for obtaining ceramics are presented and related to the properties (such as wettability, topography and charge) that directly affect interactions with biological entities (ions, biomacromolecules and cells). The literature reviewed demonstrates that these interactions are directly affected by the nanostructure of the ceramic surfaces. Thus, the understanding and control of the interactions between nanoceramics and biological entities may play one of the leading roles in the development of nanomedicine.     

Hydroxyapatite ceramic bodies with tailored mechanical properties for different applications

A perfect control on the final ceramic features will enable the research/clinical community to spread the use of calcium phosphate ceramic bodies to a large number of applications and/or requirements. The mechanical properties of hydroxyapatite ceramic bodies manufactured by different techniques and with different porosities is presented. The flexural strength, hardness, fracture toughness, surface roughness, and their evolution after immersion in SBF are studied. An increase of the mechanical properties with density is observed. The factors governing these results are analyzed. The increase of the porosity percentage of the bodies results in an increase on the surface roughness. The degradation studies show that the HA ceramics keep their integrity and mechanical properties under physiological conditions during the soaking time studied. The OHAp ceramic bodies with controlled porosity could be appropriated for hard tissue substitution or as a carriers for controlled delivery of drugs or as scaffolds for tissue engineering.     

Surface hardening by anodizing and heat treatments of Ti6Al4V alloys for articular prostheses

This paper presents a study of the surface hardening of Ti6Al4V alloy produced by electrochemical anodizing and by different heat treatments, in addition to studying the annealing of the martensitic structure. Results of the combination of both methods produce hardening over 1300 HV and an important improvement on the tribological behaviour. These values could improve wear resistance of this alloy in applications like articular prostheses.     

Acrylic bone cements modified with beta-TCP particles encapsulated with poly(ethylene glycol)

Beta-tricalcium phosphate (beta-TCP) has been encapsulated with poly(ethylene glycol) (PEG) to improve the filler/cement interface, and it was later incorporated to a poly(methyl methacrylate) bone cement in order to obtain cements with improved stability in the long term. Size and size distribution of the agglomerates forming the initial powder was drastically changed after its dispersion in a PEG aqueous solution. Whereas the initial beta-TCP particles had a 584 microm average diameter, the treated particles (TCP-PEG) presented more than 60% of the particles in a range of 2-6 microm. The effect of adding the treated particles to an acrylic cement was evaluated in terms of curing parameters, in vitro behaviour and mechanical performance. The presence of the TCP-PEG particles did not affect either peak temperature or setting time, indicating a good homogeneity of polymerising mass in contrast to the effect observed with the plain beta-TCP particles, which gave rise to higher setting times. In vitro behaviour studies revealed hydration degree values of the modified cements comparable to that of PMMA cements. Early stages of water uptake was Fickian in nature for all the experimental formulations indicating that the water absorption followed a diffusion controlled mechanism. After 3 months of storage in SBF the experimental formulations presented values of compressive strength in the range 76-78 MPa, higher than the minimum required by ISO 5833 (70 MPa) and those of tensile strength in the range 42-48 MPa, higher than the minimum reported for commercial formulations (30 MPa), but no significant differences in the strengths and elastic modulus were observed with the treatment of the filler particles. This observation was confirmed by ESEM analysis of the tensile fracture surfaces, which revealed a rather good cohesion between the bioceramic particles with some gaps around them, independently of the type of particles. The themogravimetric analysis of dry and wet specimens showed a higher dissolution rate of the plain beta-TCP particles in comparison to the encapsulated ones, indicating that the PEG adsorbed on the surface of the TCP particles could be a way to control the resorbability of the bioceramic component.     

Discerning the role of topography and ion exchange in cell response of bioactive tissue engineering scaffolds

Surface topography is known to have an influence on osteoblast activity. However, in the case of bioactive materials, topographical changes can affect also ion exchange properties. This makes the problem more complex, since it is often difficult to separate the strictly topographical effects from the effects of ionic fluctuations in the medium. The scope of this paper is to analyze the simultaneous effect of topography and topography-mediated ion exchange on the initial cellular behavior of osteoblastic-like cells cultured on bioactive tissue engineering substrates. Two apatitic substrates with identical chemical composition but different micro/nanostructural features were obtained by low-temperature setting of a calcium phosphate cement. MG63 osteoblastic-like cells were cultured either in direct contact with the substrates or with their extracts. A strong and permanent decrease of calcium concentration in the culture medium, dependent on substrate topography, was detected. A major effect of the substrate microstructure on cell proliferation was observed, explained in part by the topography-mediated ion exchange, but not specifically by the ionic Ca(2+) fluctuations. Cell differentiation was strongly enhanced when cells were cultured on the finer substrate. This effect was not explained by the chemical modification of the medium, but rather suggested a strictly topographical effect.