An electrochemical technique was used to modify a biomedical-grade 316LVM stainless steel surface... more An electrochemical technique was used to modify a biomedical-grade 316LVM stainless steel surface in order to improve its biocompatibility. A significant improvement in general and pitting corrosion resistance of 316LVM was achieved ; 97% protection efficiency against general corrosion, and 100% efficiency against pitting corrosion in physiological solutions. A significant improvement in cell/surface interactions was achieved. The electrochemically treated surface also demonstrated a significantly lower thrombogenicity. A change in dielectric properties of the passive film and its increase in thickness were found to be the major factors responsible for the observed improvement in the corrosion resistance, while the cell/surface interactions were controlled by surface topography, physico-chemical properties, and kinetics, surface concentration and conformation of adsorbed fibronectin.
Ultra fine grained (UFG) pure titanium fabricated by severe plastic deformation techniques has be... more Ultra fine grained (UFG) pure titanium fabricated by severe plastic deformation techniques has been recently considered for biomedical applications. In this study, the effects of grain size and crystallographic orientation on the biocompatibility of commercially pure titanium have been evaluated. Samples having significant differences in terms of average grain size (from 0.4 to 20 mm) and crystallographic textures have been produced using equal channel angular pressing (ECAP) and compared. X-ray diffraction and electron back scattered diffraction (EBSD) were used to document the texture and microstructural properties. Cell attachment tests were done to study the biocompatibility of the samples using MC3T3 pre-osteoblast cells. The number of attached cells was found to be higher on the samples having more (0002) plane parallel to the surface regardless of their grain sizes. It was concluded that the texture plays a more significant role than the grain size in the biocompatibility of ...
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Bacterial membranes serve as selective environmental barriers and contain determinants required f... more Bacterial membranes serve as selective environmental barriers and contain determinants required for bacterial colonization and survival. Cell envelopes of Gram-negative bacteria consist of an outer and an inner membrane separated by a periplasmic space. Most Gram-negative bacteria display a smooth outer surface (e.g., Enterobacteriaceae ), whereas members of the Pasteurellaceae and Moraxellaceae families show convoluted surfaces. Aggregatibacter actinomycetemcomitans , an oral pathogen representative of the Pasteurellaceae family, displays a convoluted membrane morphology. This phenotype is associated with the presence of morphogenesis protein C (MorC). Inactivation of the morC gene results in a smooth membrane appearance when visualized by two-dimensional (2D) electron microscopy. In this study, 3D electron microscopy and atomic force microscopy of whole-mount bacterial preparations as well as 3D electron microscopy of ultrathin sections of high-pressure frozen and freeze-substitut...
Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.
Bacterial adhesion to host tissues is considered the first and critical step of microbial infecti... more Bacterial adhesion to host tissues is considered the first and critical step of microbial infection. The extracellular matrix protein adhesin A (EmaA) is a collagen-binding adhesin of the periodontal pathogen, Aggregatibacter actinomycetemcomitans. Three 202 kDa EmaA monomers form antenna-like structures on the bacterial surface with the functional domain located at the apical end. The structure of the 30 nm functional domain has been determined by 3D electron tomography and subvolume averaging. The region exhibits a complex architecture composed of three subdomains (SI-SIII) and a linker between subdomains SII and SIII. However, the molecular interaction between the adhesin receptor complex has yet to be revealed. This study provides the first detailed 3D structure of reconstituted EmaA/collagen complexes obtained using 3D electron tomography and image processing techniques. The observed interactions of EmaA with collagen were not to whole, intact fibrils, but rather to individual ...
Palmityl-substituted sepharose 4B has been used for adsorptive immobilization of heat-denatured c... more Palmityl-substituted sepharose 4B has been used for adsorptive immobilization of heat-denatured carbonic anhydrase. The native form of this enzyme does not show any affinity for binding to this hydrophobic support. However, through the process of denaturation-renaturation performed by heating and subsequent cooling of an enzyme solution in the presence of the matrix, it was possible to obtain a catalytically active immobilized preparation, which was used successfully in continuous catalytic transformations. It is suggested that this simple procedure may provide a convenient method of immobilization for proteins, which are not normally adsorbed on hydrophobic supports.
The aim of this study is to investigate the effects of grain orientation in polycrystalline mater... more The aim of this study is to investigate the effects of grain orientation in polycrystalline materials on cell-substrate interactions. Samples are prepared from rods and sheets of Ti-6Al-4V substrates with predominately two distinct crystallographic orientations. X-ray diffraction analysis indicates that 36% of the surfaces of rod samples consist of (1010) plane, while the predominant orientation in the surface of the sheet samples is (1120) plane (29%). Morphological studies and cell biological experiments including cell attachment, proliferation and differentiation are conducted using MC3T3 pre-osteoblast cells cultured on these two different samples. The number of attached cells on the rod Ti-(1010) samples (70% after 1 h and 50% after 2 h) is higher than on the sheet Ti-(1120) samples. Cell proliferation after 3 days is also significantly higher on the Ti-(1010) samples. Alkaline phosphatase activity, however, shows no significant difference between the two samples. Scanning electron microscopy (SEM) analysis of MC3T3 cells grown on samples with different crystallographic texture demonstrate significant differences in morphology with respect to attachment and growth pattern. This study shows that crystal orientation of the substrate can influence cell responses and, therefore, substrate engineering can be used to improve and control cell-substrate interactions.
The influence of an electrochemical surface passivation technique (cyclic potentiodynamic polariz... more The influence of an electrochemical surface passivation technique (cyclic potentiodynamic polarization, CPP) on the physico-chemical surface properties of SS316LS and its subsequent response to fibronectin (Fn) and pre-osteoblasts were investigated. Contact angle and zeta-potential measurements showed that the CPP-modified surface is more hydrophilic and more positively charged than the unmodified surface. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to investigate the interaction of Fn with both surfaces. The saturated surface concentration of adsorbed Fn was higher on the CPP-modified surface. As well, significant changes were identified in the secondary structure of Fn adsorbed on both surfaces, in comparison to its native state. This data also indicated a higher degree of Fn unfolding on the CPP-modified surface. Cell studies indicated that the attachment, proliferation and morphology of pre-osteoblasts were significantly improved on the CPP-modified surface, which was attributed to the more open conformation of Fn on the CPP-modified surface. Thus, the CPP surface passivation method was demonstrated to yield a SS316LS surface of enhanced biocompatibility.
An electrochemical technique was used to modify a biomedical-grade 316LVM stainless steel surface... more An electrochemical technique was used to modify a biomedical-grade 316LVM stainless steel surface in order to improve its biocompatibility. A significant improvement in general and pitting corrosion resistance of 316LVM was achieved ; 97% protection efficiency against general corrosion, and 100% efficiency against pitting corrosion in physiological solutions. A significant improvement in cell/surface interactions was achieved. The electrochemically treated surface also demonstrated a significantly lower thrombogenicity. A change in dielectric properties of the passive film and its increase in thickness were found to be the major factors responsible for the observed improvement in the corrosion resistance, while the cell/surface interactions were controlled by surface topography, physico-chemical properties, and kinetics, surface concentration and conformation of adsorbed fibronectin.
Ultra fine grained (UFG) pure titanium fabricated by severe plastic deformation techniques has be... more Ultra fine grained (UFG) pure titanium fabricated by severe plastic deformation techniques has been recently considered for biomedical applications. In this study, the effects of grain size and crystallographic orientation on the biocompatibility of commercially pure titanium have been evaluated. Samples having significant differences in terms of average grain size (from 0.4 to 20 mm) and crystallographic textures have been produced using equal channel angular pressing (ECAP) and compared. X-ray diffraction and electron back scattered diffraction (EBSD) were used to document the texture and microstructural properties. Cell attachment tests were done to study the biocompatibility of the samples using MC3T3 pre-osteoblast cells. The number of attached cells was found to be higher on the samples having more (0002) plane parallel to the surface regardless of their grain sizes. It was concluded that the texture plays a more significant role than the grain size in the biocompatibility of ...
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.
Bacterial membranes serve as selective environmental barriers and contain determinants required f... more Bacterial membranes serve as selective environmental barriers and contain determinants required for bacterial colonization and survival. Cell envelopes of Gram-negative bacteria consist of an outer and an inner membrane separated by a periplasmic space. Most Gram-negative bacteria display a smooth outer surface (e.g., Enterobacteriaceae ), whereas members of the Pasteurellaceae and Moraxellaceae families show convoluted surfaces. Aggregatibacter actinomycetemcomitans , an oral pathogen representative of the Pasteurellaceae family, displays a convoluted membrane morphology. This phenotype is associated with the presence of morphogenesis protein C (MorC). Inactivation of the morC gene results in a smooth membrane appearance when visualized by two-dimensional (2D) electron microscopy. In this study, 3D electron microscopy and atomic force microscopy of whole-mount bacterial preparations as well as 3D electron microscopy of ultrathin sections of high-pressure frozen and freeze-substitut...
Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, ... more Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.
Bacterial adhesion to host tissues is considered the first and critical step of microbial infecti... more Bacterial adhesion to host tissues is considered the first and critical step of microbial infection. The extracellular matrix protein adhesin A (EmaA) is a collagen-binding adhesin of the periodontal pathogen, Aggregatibacter actinomycetemcomitans. Three 202 kDa EmaA monomers form antenna-like structures on the bacterial surface with the functional domain located at the apical end. The structure of the 30 nm functional domain has been determined by 3D electron tomography and subvolume averaging. The region exhibits a complex architecture composed of three subdomains (SI-SIII) and a linker between subdomains SII and SIII. However, the molecular interaction between the adhesin receptor complex has yet to be revealed. This study provides the first detailed 3D structure of reconstituted EmaA/collagen complexes obtained using 3D electron tomography and image processing techniques. The observed interactions of EmaA with collagen were not to whole, intact fibrils, but rather to individual ...
Palmityl-substituted sepharose 4B has been used for adsorptive immobilization of heat-denatured c... more Palmityl-substituted sepharose 4B has been used for adsorptive immobilization of heat-denatured carbonic anhydrase. The native form of this enzyme does not show any affinity for binding to this hydrophobic support. However, through the process of denaturation-renaturation performed by heating and subsequent cooling of an enzyme solution in the presence of the matrix, it was possible to obtain a catalytically active immobilized preparation, which was used successfully in continuous catalytic transformations. It is suggested that this simple procedure may provide a convenient method of immobilization for proteins, which are not normally adsorbed on hydrophobic supports.
The aim of this study is to investigate the effects of grain orientation in polycrystalline mater... more The aim of this study is to investigate the effects of grain orientation in polycrystalline materials on cell-substrate interactions. Samples are prepared from rods and sheets of Ti-6Al-4V substrates with predominately two distinct crystallographic orientations. X-ray diffraction analysis indicates that 36% of the surfaces of rod samples consist of (1010) plane, while the predominant orientation in the surface of the sheet samples is (1120) plane (29%). Morphological studies and cell biological experiments including cell attachment, proliferation and differentiation are conducted using MC3T3 pre-osteoblast cells cultured on these two different samples. The number of attached cells on the rod Ti-(1010) samples (70% after 1 h and 50% after 2 h) is higher than on the sheet Ti-(1120) samples. Cell proliferation after 3 days is also significantly higher on the Ti-(1010) samples. Alkaline phosphatase activity, however, shows no significant difference between the two samples. Scanning electron microscopy (SEM) analysis of MC3T3 cells grown on samples with different crystallographic texture demonstrate significant differences in morphology with respect to attachment and growth pattern. This study shows that crystal orientation of the substrate can influence cell responses and, therefore, substrate engineering can be used to improve and control cell-substrate interactions.
The influence of an electrochemical surface passivation technique (cyclic potentiodynamic polariz... more The influence of an electrochemical surface passivation technique (cyclic potentiodynamic polarization, CPP) on the physico-chemical surface properties of SS316LS and its subsequent response to fibronectin (Fn) and pre-osteoblasts were investigated. Contact angle and zeta-potential measurements showed that the CPP-modified surface is more hydrophilic and more positively charged than the unmodified surface. Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to investigate the interaction of Fn with both surfaces. The saturated surface concentration of adsorbed Fn was higher on the CPP-modified surface. As well, significant changes were identified in the secondary structure of Fn adsorbed on both surfaces, in comparison to its native state. This data also indicated a higher degree of Fn unfolding on the CPP-modified surface. Cell studies indicated that the attachment, proliferation and morphology of pre-osteoblasts were significantly improved on the CPP-modified surface, which was attributed to the more open conformation of Fn on the CPP-modified surface. Thus, the CPP surface passivation method was demonstrated to yield a SS316LS surface of enhanced biocompatibility.
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Papers by Fereshteh Azari