Densities and orientations of antibodies on nano-textured silicon surfaces

High surface densities of properly oriented antibodies are desired for enhancing the sensitivity of immunosensors. A systematic investigation of the densities and orientations of antibodies, immobilized without and with intermediate protein molecules (protein-A and streptavidin) on nano-textured silicon surfaces (RMS roughness < 100 nm) was performed and the results were compared to those obtained from non-textured surfaces. The primary antibody densities and orientations (through densities of secondary antibodies) were quantitatively measured for the different cases. Higher densities were obtained for all nano-textured surfaces compared to non-textured ones. It was observed that higher primary antibody densities were obtained when no intermediate proteins were used. The different nano-texturing conditions did not have a significant effect on the densities with no intermediate proteins and with protein-A, but had an effect with streptavidin. The densities of the properly oriented primary antibodies increased on most of the nano-textured surfaces used as compared to the non-textured samples. The effect of the texturing on the densities was observed for several of the surfaces studied. Design nano-texturing could be used to maximize as well as tune the densities of the properly oriented antibodies on the substrate surface.     

Evaluation of reinforced strength and remineralized potential of resins with nanocrystallites and silica modified filler surfaces

Surface-modified dicalcium phosphate anhydrous particles that were treated with an ion-rich solution and a silane-coupling agent were evaluated as fillers for resin composites. The physiochemical properties of these composites were characterized. The properties of the specimens as reinforcements, which were modified using various surface conditions and 30% and 50% filler to composite mass ratios (30% and 50%) were measured before and after they were immersed in water for 24 h. All groups were of the same strength and showed no significant changes after immersion. However, the groups showed a significant increase in the modulus after 24 h of immersion. The filler surfaces with nanocrystallites had the highest modulus, whereas the fillers treated with silanization had the lowest ion concentration in the solution and highest remineralization ability after immersion. The strength and brittleness were increased by the modified fillers with nanocrystallites on the surfaces and by the increased amount of fillers in the resin composites. Filler surfaces that were modified with silica hindered interfacial interactions and consequently had better flexibility and less brittleness during the light-curing process. Surface modifications of reinforced particles using nanocrystallites and silica films have superior potential applications in restorative medicine.     

Microstructure and nanomechanical properties of enamel remineralized with asparagine–serine–serine peptide

A highly biocompatible peptide, triplet repeats of asparagine–serine–serine (3NSS) was designed to regulate mineral deposition from aqueous ions in saliva for the reconstruction of enamel lesions. Healthy human enamel was sectioned and acid demineralized to create lesions, then exposed to the 3NSS peptide solution, and finally immersed in artificial saliva for 24 h. The surface morphology and roughness were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. X-ray diffraction (XRD) was used to identify the phases and crystallinity of the deposited minerals observed on the enamel surface. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to quantitatively analyze the mineral variation by calculating the relative integrated-area of characteristic bands. Nanohardness and elastic modulus measured by nanoindentation at various treatment stages were utilized to evaluate the degree of recovery. Biomimetic effects were accessed according to the degree of nanohardness recovery and the amount of hydroxyapatite deposition. The charged segments in the 3NSS peptide greatly attracted aqueous ions from artificial saliva to form hydroxyapatite crystals to fill enamel caries, in particular the interrod areas, resulting in a slight reduction in overall surface roughness. Additionally, the deposited hydroxyapatites were of a small crystalline size in the presence of the 3NSS peptide, which effectively restrained the plastic deformations and thus resulted in greater improvements in nanohardness and elastic modulus. The degree of nanohardness recovery was 5 times greater for remineralized enamel samples treated with the 3NSS peptide compared to samples without peptide treatment.     

Effects of sodium hypochlorite solution on root dentine composition

Sodium hypochlorite (NaOCl) solution,5% w/v available chlorine (abbreviated subsequently to %), is widely used as an irrigant in root canal treatment of teeth, so its effects on dentine are of clinical importance. The effects of 0.5%, 3% and 5% NaOCl solution on the composition of root dentine were studied at ambient temperature. For dentine powder treated for 30 min, depletion of the organic phase was confirmed by infrared spectroscopy. Apatite lattice parameters showed no significant change, but NaCl was also detected by X-ray powder diffraction. The low solubility of apatite mineral in the NaOCl solutions was demonstrated by the constant weight of bulk enamel specimens immersed for seven days. The stability of the mineral phase was confirmed by scanning microradiography (SMR), an X-ray attenuation method employing photon counting. Repeated SMR measurements of the local mineral content of bulk samples of root dentine and a synthetic hydroxyapatite aggregate during exposure to pumped NaOCl solutions for 100 h showed no mineral loss. As predicted from apatite chemistry, reaction of NaOCl with the mineral phase can be excluded as a primary factor in changes in mechanical properties of treated dentine. Effects of retention of NaCl on endodontic sealants requires further investigation.     

Defects on surfaces

A brief review of various types of defects on surfaces and their role in surface reactions is presented. Particular emphasis is given on defects like steps/kinks and additives (promoters and poison).     

Remineralization of partially demineralized dentine substrate based on a biomimetic strategy

Dentine remineralization is clinically significant for prevention and treatment of dentine caries, root caries, and dentine hypersensitivity. However, dentine remineralization is more difficult than enamel remineralization due to the abundant presence of organic matrix in dentine. The objective of this study was to develop a biomimetic method to facilitate remineralization of demineralized dentine through phosphorylation of type I collagen in demineralized dentine using sodium trimetaphosphate. The experimental results indicated that the effect of fluoride on remineralizing dentine was limited when residual mineral crystals were lacking on the surface of demineralized dentine, whereas the phosphorylation and Ca(OH)₂ pretreatment enhanced surface remineralization of the partially demineralized dentine. This biomimetic methodology resulted in favorable surface properties (i.e. highly negative charge and low interfacial free energy between substrate and aqueous medium) for crystal nucleation, and thus could be a promising method to remineralize superficially demineralized dentine lesions.     

The influence of grains’ crystallographic orientations on advancing short crack

A model of microstructurally short cracks that accounts for random grain geometry and crystallographic orientations is coupled with crystal plasticity constitutive model. A short crack is then inserted in the slip plane in one of the grains at the model top boundary and extended into one of the available slip planes of the neighboring grain at monotonic remote load of 0.96R_p0.2. Crack tip opening (CTOD) and sliding (CTSD) displacements are then calculated for several different crystallographic orientations and crack lengths. As the crack is contained in a single grain the crystallographic orientation of the neighboring grain can change the crack tip displacements by up to 26%, however, the displacements change by up to a factor of 10, once the crack is extended beyond the grain boundary into the next grain. Significant CTSD values were observed in all the analyzed cases pointing to mixed mode loading. Another important observation is that the random crystallographic orientations of grains beyond the first two crack-containing grains affect the CTOD by a factor of up to 4.4. This effect decreases slightly with increased crack length.     

Photoluminescence of GaN nanowires of different crystallographic orientations

We utilized time-integrated and time-resolved photoluminescence of a-axis and c-axis gallium nitride nanowires to elucidate the origin of the blue-shifted ultraviolet photoluminescence in a-axis GaN nanowires relative to c-axis GaN nanowires. We attribute this blue-shifted ultraviolet photoluminescence to emission from surface trap states as opposed to previously proposed causes such as strain effects or built-in polarization. These results demonstrate the importance of accounting for surface effects when considering ultraviolet optoelectronic devices based on GaN nanowires.     

The formation of coincidence orientations on the interphase boundary in oriented crystallization

In the systems AuSi and AuCaF₂ the formation of coincidence orientations on the interpahse boundary in oriented crystallization has been experimentally proved. It is shown that the misfit characterizing the interphase coincidence boundary determines the additional energy of the boundary. When this energy is taken into account some peculiarities of the formation of coincidence orientations can be explained.     

Investigations on grinding process of woven ceramic matrix composite based on reinforced fiber orientations

Fiber orientations play the decisive role in grinding process of woven ceramic matrix composites, but the influence of woven fibers in grinding process is not clear. This paper studies the surface quality and grinding force by comparing different woven surfaces. Through a series of experiments in optimized sampling conditions, we analyze characteristics of the material surface topography height, wave distribution and surface support properties in details. And we find some outstanding characteristics of the surface microstructure. We also study the influence of grinding processing parameters on surface microstructure. The results show that machining surface which contains more parallel fibers is rougher and more keenness than gauss surface. Grinding wheel speed and depth of cut have great influence on surface topography and surface support properties. And it is discovered that grinding forces are also highly dependent on fiber orientations. The mechanism of the grinding phenomena is also analyzed in this paper according to knowledge of fracture mechanics and mechanical damage phenomenology. The research obtained will be an important technical support on improving the processing quality of woven ceramic matrix composites.     

Effect of crystallographic orientations on electrical properties of sputter-deposited nickel oxide thin films

Nickel oxide thin films of various preferred orientations were deposited by radio-frequency (RF) magnetron sputtering process in different gas ratios of oxygen atmosphere at RF power 200 W on unheated and heated for (673 K) substrates. The relationships among substrate temperature, preferred orientation and electrical properties of the NiO films were investigated. The resulting films were analyzed by grazing-incidence X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), and ultrahigh resolution scanning electron microscopy (HR-SEM). The electrical properties were measured using four probe and Hall effects measurements. The results show that films deposited at room temperature with the ratio of oxygen varying from 0 to 100% develop a (111) preferred orientation. At temperature of 673 K, while the (111)-orientated film was obtained under a low ratio of oxygen (<50% O₂), a (200) preferred orientation was developed under 100% oxygen. The lowest sheet resistance 0.01 MΩ/□, resistivity 0.83 Ω-cm and higher carrier density 7.35 × 10¹⁸ cm⁻³ could be obtained on (111) preferred orientation samples prepared on unheated substrates in pure oxygen atmosphere. The relationship between preferred orientation and electrical properties was proposed in this paper.     

Study on the potential inhibition of root dentine wear adjacent to fluoride-containing restorations

The purpose of this in vitro study was to determine whether the vicinity of root dentine that had been restored with fluoride-releasing materials was at reduced risk for erosive/abrasive wear compared to root dentine restored with a non-fluoride-containing material. According to a randomized complete block design, standardized cavities prepared on the surface of 150 bovine root dentine slabs were restored with glass-ionomer cement, resin-modified glass ionomer, polyacid-modified resin composite, fluoride-containing or conventional composite. Specimens were coated with two layers of an acid-resistant nail varnish exposing half of the dentine surface and half of the restoration. Subsequently, specimens were either eroded in an acidic drink or left uneroded, then exposed to artificial saliva and abraded in a toothbrushing machine. Wear depth in the vicinity of restorations was quantified by a stylus profilometer, based on the nonabraded areas surrounding the erosion/abrasion region. Two-way ANOVA did not demonstrate significant interaction between restoratives and eroded-uneroded dentine (p = 0.5549) nor significant difference among restorative materials (p = 0.8639). Tukey’s test ascertained that the wear depth was higher for eroded than for uneroded groups. Fluoride-releasing materials seemed to negligibly inhibit wear in the vicinity of restored root dentine subjected to erosive/abrasive challenges.     

The spatial arrangement of tubules in human dentin

We applied two-dimensional numerical methods to describe the spatial arrangement of tubules in human dentin. The methods considered were two-point correlation functions, entropy-like measures, and angular distributions between nearest neighbors. The correlation functions were based on Fourier transform methods. The latter two approaches were based on stochastic geometry, and involved developing the Delaunay tessellations of the tubule patterns and their dual Voronoi diagrams. We discovered that for analyzing the distribution of tubules the geometric methods of lattice tessellations were more sensitive to structural order of the tubules than were Fourier-based schemes. Analysis of the data indicated that dentinal tubules are highly ordered in normal dentin. © 2001 Kluwer Academic Publishers     

Buckling of lipid tubules in shrinking liquid droplets

Self-assembled hollow lipid tubules are interesting and potentially useful supramolecular structures. Here, we study the deformation of lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) trapped inside liquid droplets on glass substrates. The interface tension of the shrinking liquid droplets exerts a compression force on the ends of the trapped lipid tubules, and causes them to buckle. This provides a method to measure their mechanical properties. The Young's modulus of the DC8,9PC lipid tubules is estimated to approximately 1.07 GPa. As the strain energy of the buckled tubules builds up, they poke through the interface of shrinking liquid droplets and then adhere onto glass substrates to form looplike shapes.     

The role of Cu crystallographic orientations towards growing superclean graphene on meter-sized scale

Chemical vapor deposition(CVD)-grown graphene films on Cu foils,exhibiting fine scalability and high quality,are still suffering from the adverse impact of surf...