The effect of water-miscible organic solvents on the stability of filamentous phages displaying a random peptide library was investigated. A kinetic analysis of the time course of viral infectivity indicated that the transition between the noninfectious and infectious form was directly related to the concentration of organic solvent.
We present a modification of the weighted K-nearest neighbours imputation method (KNNimpute) for missing values (MVs) estimation in microarray data based on the reuse of estimated data. The method was called iterative KNN imputation (IKNNimpute) as the estimation is performed iteratively using the recently estimated values.
The estimation efficiency of IKNNimpute was assessed under different conditions (data type, fraction and structure of missing data) by the normalized root mean squared error (NRMSE) and the correlation coefficients between estimated and true values, and compared with that of other cluster-based estimation methods (KNNimpute and sequential KNN). We further investigated the influence of imputation on the detection of differentially expressed genes using SAM by examining the differentially expressed genes that are lost after MV estimation.
The performance measures give consistent results, indicating that the iterative procedure of IKNNimpute can enhance the prediction ability of cluster-based methods in the presence of high missing rates, in non-time series experiments and in data sets comprising both time series and non-time series data, because the information of the genes having MVs is used more efficiently and the iterative procedure allows refining the MV estimates. More importantly, IKNN has a smaller detrimental effect on the detection of differentially expressed genes.
The departments, indeed the laboratories of the public research institutions, no longer are satisfied with displaying a certain number of annual scientific publications meant to highlight their expertise and know-how. In effect, for some years now, a new trend has been in vogue: stimulated by all the national and international public bodies, they are calling increasingly on the “patent pending” solution to make optimum use of the results of specific researches on the one hand and, on the other hand, to assert their excellence vis-à-vis the Ministry of Research of their country which is supposed to finance them.
However, caught up in the euphoria of the research results, and lost in their formulae and practices, these researchers lose sight of the basis for a patent and its real reason for being (patent charter). A patent necessarily must be of service to the community, that is to say that essentially it must contribute to the improvement of the quality of life of the population. To achieve this goal, going through certain stages is a must, namely that to start with a patent must be absolutely profitable to industry in order that, subsequently, it be consistent with its being of service to the community. In this context, its validity is set at 10 years renewable for another 10 years based on specific parameters as stipulated by the national and international patent institutions, indeed by the EPO (European Patent Office) the headquarters of which is in Munich. Its use by industry ensures proceeds for 10, even 20 years and must represent the material fruit of the applicant's effort. Beyond this period, the patent becomes public and therefore available to everyone. But the crucial problem is this: when can a patent really be used and how to do so as best as possible to guarantee profits for both parties involved and thus justify its reason for being?
The purpose of this work thus is to incite university researchers to think about the real usefulness of a patent on the one hand and, on the other hand, to ponder over the best way of using, in close cooperation with industry, the fruit of the research and the registering of the patent, both financed by public funds. For the latter, owing to their nature, demand that there be no wastage and cautious management thereof.
Cell adhesion on biomaterial surfaces and the vitality of anchorage dependent cells is affected by several parameters of an adsorbate layer which is intentionally or spontaneously formed. Surface pre-treatments and several conditioning steps prior and during to the cell/biomaterial contact affect the composition, orientation, quantity and viscoelasticity of the interfacing layer between cells and biomaterial. This work was performed to elucidate the response of cells on two modified biomaterial surfaces based on protein or carbohydrate adsorbates:
Masked UV irradiations opened a simple route to obtain chemically patterned substrates controlling serum protein adsorption and cell adhesion. It is possible to achieve structures of subcellular size and to produce immobilized gradients. In order to examine the protein matrix deposited on these substrates we applied a quartz microbalance technique (QCM-D) capable to extract viscoelastic data in addition to the mass uptake during plasma protein deposition. It was found that the quantity and viscosity of surface bound albumin is lowered when the surface is modified (patterned) by UV exposure. Hence, the UV modification promotes the competitive adsorption of cell adhesion proteins from the media or upon secretion by the cells and yields to the observed cell patterns.
Another tissue engineering technique, using immobilized, modified and/or cross linked hyaluronic acid (HA), an important extra cellular matrix component in vivo, is also examined by QCM-D. Our data demonstrate that HA can be modified by an activation with a carbodiimide, followed by the application of an α,ω-bisamino polyethyleneglycol. The QCM-D data can be interpreted as a stiffening of the HA layer combined with the release of hydration water. Further, the hydration state and the viscoelastic behaviour of surface bound ultrathin HA hydrogels was examined.
Quantification of viscoelastic parameters of thin films of ECM by QCM-D is valuable for the interpretation of durotaxis, describing effects of mechanical substrate parameters on the adhesion and motility of cells.
In recent years, considerable effort has been devoted to the design and controlled fabrication of structured materials with functional properties. The layer by layer buildup of polyelectrolyte multilayer films (PEM films) from oppositely charged polyelectrolytes offers new opportunities for the preparation of functionalized biomaterial coatings. This technique allows the preparation of supramolecular nano-architectures exhibiting specific properties in terms of control of cell activation and may also play a role in the development of local drug delivery systems. Peptides, proteins, chemically bound to polyelectrolytes, adsorbed or embedded in PEM films, have been shown to retain their biological activities.
Atomic Force Microscope (AFM) as a surface characterization technique has offered a great impulse in the advance of biocompatible materials. In this study AFM was implemented for the investigation of the early stages of adsorption of two human plasma proteins on titanium and hydrogenated carbon biocompatible thin films. The plasma proteins that were used were Human Serum Albumin and Fibrinogen, two of the most important proteins in human plasma. The concentration of the protein solutions was the same as that in human plasma. As the examined samples were soft, non-contact AFM mode was used to avoid their destruction. In order for the early stages of protein adsorption to be assessed, small incubation times were applied. AFM measurements in liquid buffer were also carried out, allowing the observation of the protein behaviour in an environment much closer to their native one. In addition, there was an assessment of the adsorption mechanism of the proteins on the above-mentioned biomaterials.
Haemocompatibility is one of the most important properties, together with the tissue compatibility and corrosion and wear resistance that determine the biocompatibility of the artificial implants. Carbon-based thin films, such as amorphous carbon (a-C) and amorphous hydrogenated diamond-like carbon (a-C:H or DLC) are considered as excellent candidates for use as biocompatible coatings on biomedical implants. The aim of this work is the comparative study of the haemocompatibility of the a-C:H thin films developed by magnetron sputtering under various deposition conditions, the development of a methodology in order to study the haemocompatibility of thin films, the optical properties of the adsorbed proteins (human serum albumin and fibrinogen) and their adsorption mechanisms. Haemocompatibility and the optical properties of a-C:H thin films and the adsorbed proteins were studied by spectroscopic ellipsometry (SE). The films grown under floating conditions performed better haemocompatibility compared with those deposited under application of bias voltage. In the range of vis–UV, proteins are transparent, while they present an absorption peak at higher energies, but except these characteristics, their optical functions are rather featureless. Adsorption mechanisms were studied through AFM technique too. AFM results are in accordance with those derived by SE. Combination of the two techniques gives us a more accurate description of protein adsorption mechanisms.
A possibility of poly-d,l-lactide modification by multiwall carbon nanotubes (MWCNT) has been shown. MWCNT were prepared from methane-air mixture upon atmospheric pressure without catalyst on high voltage atmospheric pressure discharge plasma set-up. According to scanning and transmission electronic microscope data carbon nanotubes diameters were within 12–60 nm. Quantities of MWCNT incorporated did not exceed 0.5%. Nanocomposites were obtained by sonification of mixture of a poly-d,l-lactide solution in chloroform and MWCNT followed by film casting on glass substrates. Tensile strength and thermomechanical properties of the dried composite films were investigated.
Introduction of MWCNT into poly-d,l-lactide has been shown to cause the enhanced polymer stability to thermal oxidative destruction. Taking into account the results obtained one could anticipate that implants from nanocomposites of poly-d,l-lactide with MWCNT would be dispersed in a living organism more slowly as compared to implants from pure poly-d,l-lactide without additives.
Biomaterials and tissue engineering technologies are becoming increasingly important in biomedical practice, particularly as the population ages. Cellular responses depend on topographical properties of the biomaterial at the nanometer scale. Structures on biomaterial surfaces are used as powerful tools to influence or even control interactions between implants and the biological system [Kawahara, H., Soeda, Y., Niwa, K., Takahashi, M., Kawahara, D., Araki, N., 2004. J. Mater. Sci. Mater. Med. 15 (12), 1297–1307; Winkelmann, M., Gold, J., Hauert, R., Kasemo, B., Spencer, N.D., Brunette, D.M., Textor, M., 2003. Biomaterials 24 (7), 1133–1145]. The influence of nanometer sized surface structures on osteoblastlike cell interactions was tested with niobium oxide coatings on polished titanium slices (cp-Ti grade 2). The aim of the study was to investigate the influence of nanoscopic surface structures on osteoblast interactions in order to support collagen I production and cell adhesion. The coatings were done by means of the sol–gel process. The surface structure was adjusted by annealing of the metaloxide ceramic coatings due to temperature depended crystal growth. The applied annealing temperatures were 450, 550 and 700 °C for 1 h, corresponding to Ra-numbers of 7, 15 and 40 nm. The surfaces were characterized by means of AFM, DTA/TG, diffractometry and white light interferometry. The cell reactions were investigated concerning adhesion kinetics, migration, spreading, cell adhesion, and collagen I synthesis. The smooth surface (Ra = 7 nm) resulted in the fastest cell anchorage and cell migration. The closest cell adhesion was reached with the surface structure of Ra = 15 nm. The roughest surface (Ra = 40 nm) impedes the cell migration as well as a proper spreading of the cells. The best results concerning cell adhesion and spreading was reached with an intermediate surface roughness of Ra = 15 nm of the niobium oxide coating on cp-titanium slices.
A plasma process for the surface modification of HA powders has been developed. Acrylic acid and acrylic acid/octadiene plasma deposited films onto HA particles have demonstrated to interact with SBF allowing the calcium dissolution–precipitation mechanism. Therefore, a nanostructured composite between HA and a self-assembling peptide scaffold (RAD16-I) has been developed. The differentiation of mESC in this scaffold has been studied, in order to test the osteogenic capacity of the new composite material. We have observed that the mESC can be iduced to produce Ca salts (mineralization) in a 3D-microenvironment and moreover, this activity can be enhanced by the presence of HA particules into the nanofiber scaffold.
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