Applications of environmental scanning electron microscopy (ESEM) in biomaterials field

Various tasks were undertaken in our laboratory where environmental scanning electron microscopy (ESEM) has been of particular interest within the biomaterials field. The possibility of observing wet samples, as well as the fact that sample preparation is minimal, has improved shorter time scales and lower costs in microscopy. Minimal preparation has also reduced the possibility of introducing artifacts. Examples like cell cultures used for pit resorption assays, calcium phosphate deposition processes, and dissolution of phosphate glasses used as biomaterials are presented. Finally, a servohydraulic testing machine designed for mechanical testing in situ in ESEM has allowed the study of shape memory alloys for orthodontic applications or the behavior of different adhesives used in odontology.     

Disposition of the flavonoid quercetin in rats after single intravenous and oral doses

The pharmacokinetic and mean time tissue distribution parameters, after a single 50-mg/kg dose of quercetin administered as intravenous bolus, oral solution, and oral suspension, were determined using rat as an animal model. Following intravenous administration, the elimination rate constant and the elimination half-life were found to be 0.0062 min^-1 and 111 min, respectively. Examining the mean time tissue distribution parameters reflected a strong binding affinity of the drug molecules to both plasma and tissue proteins. In addition, the low permeability rate of drug molecules in the peripheral system was demonstrated. Following the oral administration of the drug, the extent of absorption was greater from solution than from suspension. Moreover, the solution showed a shorter T_max and a higher C_max than suspension. The absolute bioavailability for the solution was 0.275 and that for suspension was 0.162. The mean residence time (MRT) and the mean absorption time (MAT) were higher for suspension, reflecting the need for dissolving the drug in order to be absorbed. The mean (in-vivo) dissolution time (MDT_in-vivo) was 34.5 min. Thus, an oral quercetin formulation that can readily form a drug solution in the gastrointestinal tract may enhance the absorption of the drug.     

Engineering Functional Collagen Scaffolds: Cyclical Loading Increases Material Strength and Fibril Aggregation

Variation in collagen fibril diameter in nature is a major factor determining biological material properties. However, the mechanism resulting in this fibril diameter difference is not clear and generally assumed to be cell‐dependent. It is certainly not possible so far to engineer this into implantable scaffold materials. This gap in our knowledge is crucial for the fabrication of truly biomimetic tissue‐like materials. We have tested the idea that fibril diameter can be regulated directly without cell involvement, using cyclical mechanical loading to promote fibril fusion. Specific loading regimes increased collagen fibril diameter (> 2 fold) in direct relation to cycle number, whilst thin fibrils disappeared. Tensile properties increased, producing a 4.5 fold rise in break strength. This represents the first demonstration of direct cyclical load‐promoted fibril fusion and provides a direct relation with material properties. The ability to control material properties in this way makes it possible to fabricate truly biomimetic collagen materials without cells.     

In situ and minimally invasive breast cancer: morphologic and kinetic features on contrast-enhanced MR imaging

Purpose: This retrospective study was undertaken to investigate the morphologic and dynamic features of in situ and minimally invasive breast cancer on contrast-enhanced (c.-e.) MR imaging and to examine possible associations to pathology features. Material and methods: A total of 71 patients underwent MR imaging. T1-weighted FLASH-3D images were obtained before and after intravenous administration of Gd-DTPA. Histopathologic analysis of 78 lesions revealed ductal carcinoma in situ (DCIS)n=50 and DCIS with microinvasionn=28. MR features were correlated with histopathologic findings. Results: Enhancement in DCIS was focal (73%), diffuse (10%) or ductal (17%). No enhancement occurred in two cases (4%). In 65% enhancement speed was classified as delayed. There was a tendency toward a more ill-defined (83 vs. 43%) enhancement pattern in high grade DCIS and a more ductal (29 vs. 12%) and faster (50 vs. 29%) enhancement in comedo type DCIS. However, significant differences in the enhancement behaviour could neither be demonstrated between high grade and non high grade DCIS nor between comedo and non comedo type DCIS. No significant differences were noted between pure and microinvasive DCIS. Conclusion: In this retrospective analysis the majority (96%) of DCIS lesions show contrast enhancement. However, in only about 50% of DCIS the criteria of a so-called ‘typical’ enhancement behaviour was fulfilled, that means strong, early, focal ill-circumscribed or ductal. Enhancement that follows a duct is often associated with malignancy, however this feature was only present in 17% of the cases. c.-e. MR imaging allowed the detection of 25 additional foci of DCIS. Therefore malignant in situ lesions can be present with atypical enhancement, and should be taken into consideration in high-risk patients in particular.     

Application of multivariate curve resolution to the analysis of yeast genome-wide screens

In this work, the application of Multivariate Curve Resolution to the analysis of yeast genome-wide screens obtained by means of DNA microarray technology is shown. In order to perform the analysis of this type of data, two algorithms based on Alternating Least Squares (MCR-ALS) and on its maximum likelihood weighted projection (MCR-WALS) variant are compared. The utilization of the modified weighted alternating least (WALS) squares algorithm is motivated by the rather poor quality, uncertainties and experimental noise associated to DNA microarray data. Moreover, a large number of missing values are usually present in these data sets and the weighted WALS approach allowed circumventing this problem. Two different experimental datasets were used for this comparison. In the first dataset, gene expression values in budding yeast were monitored in-response to glucose limitation. In the second dataset, the changes in the gene expression caused by the daunorubicin drug were monitored as a function of time. Results obtained by application of Multivariate Curve Resolution in the two cases allowed a good recovery of the evolving gene expression profiles and the identification of metabolic pathways and individual genes involved in these gene expression changes.     

Treatment of tissue paper containing radioactive waste and electrochemical recovery of valuables using ionic liquids

Dissolution of tissue paper waste containing valuable contaminants such as uranium and palladium in 1-butyl-3-methylimidazolium chloride (bmimCl) has been studied. Dissolution of 5-7 wt.% tissue paper in bmimCl is complete within 60 min at 373 K and the time required for dissolution increases with increase of loading. It is difficult to dissolve more than 10 wt.% tissue paper in bmimCl and the limiting solubility of tissue paper is 15-17 wt.% at 373 K. Uranium(VI) and Pd(II) in chloride/nitrate form dissolve in bmimCl along with tissue paper. The electrochemical behaviour of uranium(VI) and palladium(II) in the resultant solution in the presence and absence of a co-solvent, DMSO, has been investigated by transient voltammetric techniques at glassy carbon working electrode and the diffusion coefficients have been determined. Electrolysis of a solution of uranium(VI) and palladium(II) loaded tissue paper in bmimCl results in deposition of uranium oxide (UO₂) and metallic palladium, respectively, which were characterized by X-ray diffraction and scanning electron microscopy. The study established the possibility of dissolving tissue paper and other cellulose based materials containing soluble uranium(VI) and Pd(II) compounds in bmimCl, and their recovery from the resultant solution. Cellulose pulp can be regenerated by adding surplus water after the recovery of valuables and the ionic liquid, bmimCl, can be regenerated for further use by vacuum distillation of DMSO and water.     

Key factors in tissue engineering

Tissue engineering is an emerging biomedical form of engineering aiming at regeneration of natural tissues or creation of biological substitutes for defective or lost tissues and organs using cells of different species. It is essential for the tissue self-regeneration, for instance, to provide a space necessary for regeneration with certain materials and technologies. This article overviews such key factors required for tissue engineering.     

Michael Cole: Award for distinguished contributions of applications of psychology to education and training.

The American Psychological Association 2010 Award for Distinguished Contributions of Applications of Psychology to Education and Training was awarded to Michael Cole, for his study of the role of education in the learning and development of people from different cultures. His research combines experimental and ethnographic methods with Russian and American theories of the educational process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fabrication of 3D chitosan–hydroxyapatite scaffolds using a robotic dispensing system

A new robotic desktop rapid prototyping (RP) system was designed to fabricate scaffolds for tissue engineering applications. The experimental setup consists of a computer-guided desktop robot and a one-component pneumatic dispenser. The dispensing material (chitosan and chitosan–hydroxyapatite (HA) dissolved in acetic acid) was stored in a 30-ml barrel and forced out through a small Teflon-lined nozzle into a dispensing medium (sodium hydroxide–ethanol in ratio of 7:3). Layer-by-layer, the chitosan was fabricated with a preprogramed lay-down pattern. Neutralization of the chitosan forms a gel-like precipitate, and the hydrostatic pressure in the sodium hydroxide (NaOH) solution keeps the cuboid scaffold in shape. Comparison of the freeze-dried scaffold to the wet one showed linear and volumetric shrinkage of about 31% and 62%, respectively. A good attachment between layers allowed the chitosan matrix to form a fully interconnected channel architecture. Results of in vitro cell culture studies revealed the scaffold biocompatibility. The results of this preliminary study using the rapid prototyping robotic dispensing (RPBOD) system demonstrated its potential in fabricating three-dimensional (3D) scaffolds with regular and reproducible macropore architecture.