Influence of capping groups on the synthesis of γ-Fe2O3 nanocrystals

Monodisperse and uniform γ-Fe_2O_3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)_5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe_2O_3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well

Measurement Of Quasiparticle Transport In Aluminum Films Using Tungsten Transition-Edge Sensors

We report new experimental studies to understand the physics of phonon sensors which utilize quasiparticle diffusion in thin aluminum films into tungsten transition-edge-sensors (TESs) operated at 35 mK. We show that basic TES physics and a simple physical model of the overlap region between the W and Al films in our devices enables us to accurately reproduce the experimentally observed pulse shapes from x-rays absorbed in the Al films. We further estimate quasiparticle loss in Al films using a simple diffusion equation approach.Comment: 5 pages, 6 figures, PRA

Expression, purification and in vitro biological activity from human recombinant BMP-2 produced by a novel approach

Bone morphogenetic proteins have promoted great biomedical interest due to their ability in inducing new bone formation when used as powerful osteoinductive components of several late-stage bone grafting products. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is obtained from mammalian cell expressing systems in low amounts or from bacteria inclusion bodies after timeconsuming refolding methods. Thus, there is a need to establish novel approaches for producing rhBMP-2 in high yields by simple and cheap procedures.Portuguese Foundation for Science and Technolog y, FCT (PhD Grant to PC Bessa , SFRH/BD/17049/2004). This work was also partially supported by the European STREP HIPPOCRATES (NMP3 - CT - 2003 - 505758) and carried out under the scope of European NoE EXPERTISSUES (NMP3 - CT - 2004 - 500283).info:eu-repo/semantics/publishedVersio

A novel system for producing human recombinant BMP-2 and study of the growth factor stabilizing conditions

Bone tissue engineering has been an increasing field of research during the last years. The ideal approach for a regenerative application would consist in the use of cells from the patient, scaffolding materials and differentiation growth factors. Bone morphogenetic protein-2 (BMP-2) is one such growth factors with a strong ability to induce new bone and cartilage formation and has been used as a powerful osteoinductive component of several late-stage tissue engineering products for bone grafting. In this work, we aimed at obtaining high yields of human recombinant BMP-2 in a stable, pure and biologically active form by use of a new bacteria expression system that circumvents the disadvantages of conventional recombinant protein preparation methods and to perform a study of the stability conditions and the functionality of these peptides in vitro in human mesenchymal stem cells and C2C12 murine cell line.Portuguese Foundation for Science and Technology (PhD Grant to PC Bessa, SFRH/BD/17049/2004). This work was also partially supported by the European STREP HIPPOCRATES (NMP3-CT-2003-505758) and carried out under the scope of European NoE EXPERTISSUES (NMP3-CT-2004- 500283).info:eu-repo/semantics/publishedVersio

Expression, purification and in vitro biological activity from human recombinant BMP-2 produced by a novel approach

Bone tissue engineering has been an increasing field of research during the last years. The ideal approach for a regenerative application would consist in the use of cells from the patient, scaffolding materials and differentiation growth factors. Bone morphogenetic protein-2 (BMP-2) is one such growth factors with a strong ability to induce new bone and cartilage formation and has been used as a powerful osteoinductive component of several late-stage tissue engineering products for bone grafting. In this work, we aimed at obtaining high yields of human recombinant BMP-2 in a stable, pure and biologically active form by use of a new bacteria expression system that circumvents the disadvantages of conventional recombinant protein preparation methods and to perform a study of the stability conditions and functionality of these peptides in vitro in human mesenchymal stem cells and C2C12 murine cell line.Portuguese Foundation for Science and Technology, FCT (PhD Grant to PC Bessa, to PC Bessa, SFRH/BD/17049/2004 SFRH/BD/17049/2004 ). This work was ). This work was also partially supported by the European STREP HIPPOCRATES (NMP3 also partially supported by the European STREP HIPPOCRATES (NMP3--CTCT--2003 2003--505758) and carried out under the scope of 505758) and carried out under the scope of European NoE EXPERTISSUES (NMP3 European NoE EXPERTISSUES (NMP3--CTCT- -2004 2004 --500283). 500283info:eu-repo/semantics/publishedVersio

Comparison of nanoparticular hydroxyapatite pastes of different particle content and size in a novel scapula defect model

Nanocrystalline hydroxyapatite (HA) has good biocompatibility and the potential to support bone formation. It represents a promising alternative to autologous bone grafting, which is considered the current gold standard for the treatment of low weight bearing bone defects. The purpose of this study was to compare three bone substitute pastes of different HA content and particle size with autologous bone and empty defects, at two time points (6 and 12 months) in an ovine scapula drillhole model using micro-CT, histology and histomorphometry evaluation. The nHA-LC (38% HA content) paste supported bone formation with a high defect bridging-rate. Compared to nHA-LC, Ostim(®) (35% HA content) showed less and smaller particle agglomerates but also a reduced defect bridging-rate due to its fast degradation The highly concentrated nHA-HC paste (48% HA content) formed oversized particle agglomerates which supported the defect bridging but left little space for bone formation in the defect site. Interestingly, the gold standard treatment of the defect site with autologous bone tissue did not improve bone formation or defect bridging compared to the empty control. We concluded that the material resorption and bone formation was highly impacted by the particle-specific agglomeration behaviour in this study

A novel approach for the production of human recombinant BMP-2 for bone tissue engineering applications

Bone tissue engineering has been an increasing field of research during the last years. The ideal approach for a regenerative application would consist in the use of cells from the patient, scaffolding materials and differentiation growth factors. Bone morphogenetic protein-2 (BMP-2) is one such growth factors with a strong ability to induce new bone and cartilage formation and has been used as a powerful osteoinductive component of several late-stage tissue engineering products for bone grafting. In this work, we aimed at obtaining high yields of human recombinant BMP-2 in a stable, pure and biologically active form by use of a new bacteria expression system that circumvents the disadvantages of conventional recombinant protein preparation methods and to perform a study of the stability conditions and the functionality of these peptides in vitro in human mesenchymal stem cells and C2C12 murine cell line.info:eu-repo/semantics/publishedVersio

Evaluation of machine-learning methods for ligand-based virtual screening

Machine-learning methods can be used for virtual screening by analysing the structural characteristics of molecules of known (in)activity, and we here discuss the use of kernel discrimination and naive Bayesian classifier (NBC) methods for this purpose. We report a kernel method that allows the processing of molecules represented by binary, integer and real-valued descriptors, and show that it is little different in screening performance from a previously described kernel that had been developed specifically for the analysis of binary fingerprint representations of molecular structure. We then evaluate the performance of an NBC when the training-set contains only a very few active molecules. In such cases, a simpler approach based on group fusion would appear to provide superior screening performance, especially when structurally heterogeneous datasets are to be processed