A novel jet-based nano-hydroxyapatite patterning technique for osteoblast guidance

Surface topography is well known to play a crucial role in influencing cellular responses to an implant material and is therefore important in bone tissue regeneration. A novel jet-based patterning technique, template-assisted electrohydrodynamic atomization spraying, was recently devised to control precisely the surface structure as well as its dimensions. In the present study, a detailed investigation of this patterning process was carried out. A range of nano-hydroxyapatite (nHA) line-shaped patterns <20 µm in width were successfully deposited on a commercially pure Ti surface by controlling the flow of an nHA suspension in an electric field. In vitro studies showed that the nHA patterns generated are capable of regulating the human osteoblast cell attachment and orientation.     

Novel patterning of nano-bioceramics: template-assisted electrohydrodynamic atomization spraying.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.     

Application of nanotechnology to control bacterial adhesion and patterning on material surfaces

Bacterial adhesion and biofilm formation on surfaces raises health hazard issues in the medical environment. Previous studies of bacteria adhesion have focused on observations in their natural/native environments. Recently, surface science has contributed in advancing the understanding of bacterial adhesion by providing ideal platforms that attempt to mimic the bacteria's natural environments, whilst also enabling concurrent control, selectivity and spatial control of bacterial adhesion. In this review, we will look at techniques of how nanotechnology is used to control cell adhesion on a planar scale, in addition to describing the use of nanotools for cell micropatterning. Additionally, it will provide a general background of common methods for nanoscale modification enabling biologist unfamiliar with nanotechnology to enter the field.     

DNA‐Based Nanofabrication: Pathway to Applications in Surface Engineering

This Concept provides an overview of recent developments of DNA‐based nanofabrication and discusses its potential applications in the area of surface engineering. The first part of the paper discusses the strength and limitations of existing DNA‐based nanofabrication methods. The second part highlights several examples of surface engineering applications involving nano‐ and microscale surface textures. It finishes with a discussion of the opportunities and remaining challenges of applying DNA‐based nanofabrication in surface engineering applications.     

混合智能技术在激光淬火工艺优化中的应用

为探索激光淬火工艺优化设计的新方法,以GCr15激光淬火为例,首先建立神经网络模块,以提取激光淬火(多)工艺参数与(多)性能指标之间的函数映射关系,然后建立遗传算法模块,通过遗传算法的进化搜索来实现激光淬火工艺参数的优化设计.实验结果表明,本研究建立的工艺优化设计模型具有较好的可靠性;将神经网络与遗传算法的混合智能技术引入激光淬火领域,为解决激光淬火工艺优化设计问题提供了一条先进、合理的途径.     

Development of soluble glasses for biomedical use Part II: The biological response of human osteoblast cell lines to phosphate-based soluble glasses

Soluble glasses are considered to be of potential clinical value in orthopaedic and dental surgery. However, the biological response to these materials is not well understood. To determine the effects of these glasses, two human osteoblast cell lines, MG63 and HOS (TE85), were incubated in vitro in the presence of increasing concentrations of extracts of the glasses. The effects of the extracts on cell growth was measured using the MTT assay and an ELISA assay was used to measure the expression of bone sialoprotein (BSP), osteonectin (ON) and fibronectin (FN), antigens which play a fundamental part in the integrity and function of hard connective tissue. The results showed that the proliferation of the cells was adversely affected only by the more soluble glasses, which also down-regulated the expression of the bone-associated proteins. In contrast, the extract of the glass with the lowest dissolution rate, which contains relatively elevated levels of Ca²⁺, was found to enhance bone cell growth and antigen expression. These findings suggest that the compositions of these glasses at least partly determine the response of cells and thus, that the glasses could be modified to elicit a more optimal biological response and clinical efficacy.     

The response of primary rat and human osteoblasts and an immortalized rat osteoblast cell line to orthopaedic materials: comparative sensitivity of several toxicity indices

When studying the biocompatibility of orthopaedic biomaterials it isoften necessary to discriminate between responses which show mild cytotoxicity.It is therefore essential to use a very sensitive index of toxicity. We havecompared the sensitivity of four well-established indices of toxicity: totalcell protein content, leakage of lactate dehydrogenase (LDH), reducedglutathione content and the MTT assay, with that of a novel index, alkalinephosphatase (ALP) activity. Comparisons were made by detecting nickel chloridetoxicity in osteoblasts. ALP activity, the novel method, proved the mostsensitive index of toxicity and it provides a convenient automated assay forassessing the interactions of materials with osteoblasts. The responses tonickel chloride and to aqueous extracts prepared from carbon fibre reinforcedepoxy and polyetheretherketone (peek), two candidate materials for orthopaedicimplants, were compared in primary and immortalized rat osteoblasts, and !in primary human osteoblasts. Although the immortalized rat osteoblast cell line,FFC, was consistently the most sensitive cell type, the responses of the humancells and the FFC cell line were similar in terms of ALP activity throughout therange of nickel concentrations studied. Neither peek nor epoxy material extractsshowed a significant decrease in the MTT or ALP responses in any of the threecell types. Our data suggest that immortalized rat osteoblasts may provide anin vitro model system for screening the biocompatibility of orthopaedicpolymers.     

Using dual response surfaces to reduce variability in launch vehicle design: A case study

Space transportation system conceptual design is a multidisciplinary process containing considerable element of risk. Uncertainties from one engineering discipline may propagate to another through linking parameters and the final system output may have an accumulation of risk. This may lead to significant deviations from expected performance. An estimate of variability or design risk therefore becomes essential for a robust design. This study utilizes the dual response surface approach to quantify variability in critical performance characteristics during conceptual design phase of a launch vehicle. Using design of experiments methods and disciplinary design analysis codes, dual response surfaces are constructed for the mean and standard deviation to quantify variability in vehicle weight and sizing analysis. Next, an optimum solution is sought to minimize variability subject to a constraint on mean weight. In this application, the dual response surface approach lead to quantifying and minimizing variability without much increase in design effort.     

IP‐MRSO: An iterative posterior preference articulation method to multiple response surface optimization

One of the most important issues in multiple response surface optimization (MRSO) is obtaining a satisfactory “compromise” solution considering a decision maker (DM)'s preference information on the tradeoffs among multiple responses. A promising alternative to incorporate the DM's preference information into the problem is the posterior preference articulation approach, which first generates all (or most) of the nondominated solutions and then makes the DM select the best one from the set of nondominated solutions a posteriori. However, it has an inefficiency problem in that it generates an excessive number of nondominated solutions in which almost all are not used for the DM's selection. This paper proposes a new posterior method called “IP‐MRSO” to overcome the limitation of the existing posterior method. The proposed IP‐MRSO is illustrated through a well‐known MRSO case problem.     

Water Affinity to Epitaxial Graphene: The Impact of Layer Thickness

The sensitivity to water vapour of one‐, two‐, and three‐layer epitaxial graphene (1, 2, and 3LG) is examined in this study. It is unambiguously shown that graphene's response to water, as measured by changes in work function and carrier density, is dependent on its thickness, with 1LG being the most sensitive to water adsorption and environmental concentration changes. This is furthermore substantiated by surface adhesion measurements, which bring evidence that 1LG is less hydrophobic than 2LG. Yet, surprisingly, it is found that other contaminants commonly present in ambient air have a greater impact on graphene response than water vapor alone. This study indicates that graphene sensor design and calibration to minimize or discriminate the effect of the ambient, in which it is intended to operate, are necessary to insure the desired sensitivity and reliability of sensors. The present work will aid in developing models for realistic graphene sensors and establishing protocols for molecular sensor design and development.     

The chemistry of stratospheric ozone: its response to natural and anthropogenic influences

The current rapid changes in the composition of the atmosphere reflect both the metabolism of the biosphere and the broad range of influencing human activities. However, the only known sources of CFCs are industrial. In predicting future changes in ozone depletion and global warming it is necessary to understand the role of the biosphere in regulating emissions as well as future industrial emissions. This paper discusses theoretical predictions and trends in global ozone concentrations from 1969–1986. Antarctic and Arctic ozone trends and the global implications of the Antarctic ozone hole are described in detail. It is concluded that even if the control measures of the Montreal Protocol are implemented by all nations, the atmospheric abundance of chlorine will at least double during the next few decades. Future global ozone depletion could be larger than originally predicted because the PSC-induced chemical reactions that cause ozone depletion were not included in the stratospheric ozone assessment models on which the Montreal Protocol was based. To return the Antarctic ozone layer to its natural state will require very strong measures, including a complere phase out of all fully halogenated CFCs, halons, carbon tetrachloride and methyl chloroform, as well as careful use of HCFC substitutes.     

Categorization of the hemodynamic response to hemodialysis: The importance of baroreflex sensitivity

Intradialytic hypotension (IDH) remains an important cause of morbidity and mortality in hemodialysis (HD) patients. The baroreflex arc is under autonomic control and regulates blood pressure. This study aimed to investigate the contribution of impaired baroreflex sensitivity (BRS) to the pathophysiology of IDH. Thirty-four chronic HD (12 IDH-prone, 22 IDH-resistant) patients underwent BRS measurement during HD with relative blood volume monitoring. During analysis, patients were separated into four age-matched groups according to resting BRS≥4.5 ms/mmHg and hemodynamic stability. Resting BRS was extremely heterogenous (geometric mean BRS 5.78±1.41 [range 1.76–41.41] ms/mmHg). Relative blood volume reduction was well matched in all groups (mean reduction in relative blood volume for all patients −6.74%±0.86%, P>0.05). Thirty-seven episodes of IDH occurred in the IDH prone, reduced BRS group. Patients with impaired resting BRS and prone to IDH had markedly different responses to HD as compared to the preserved BRS group, but the total peripheral resistance response was significantly lower than in the IDH-resistant patients (15.9%±2.1% vs. 42.4%±3.0%, respectively, P<0.001). In those patients prone to IDH and with impaired resting BRS, percentage reduction in cardiac output at the end of HD highly correlated with reduction in relative blood volume (r=0.94, P=0.006). Hypotension during dialysis may be an important source of recurrent cardiac injury and early recognition of those patients prone to relative symptomatic and asymptomatic hypotension remains important. Impaired resting BRS and recognition of a suboptimal peripheral pressor response, appear to predict those patients most likely to undergo hemodynamic instability and may assist in the pursuit of this elusive goal.     

The relationship between radiating body forces and equivalent surface stresses: Analysis and application to EMAT design

An analysis of the radiation from a body force shows that it is equivalent to the radiation from a series of surface stresses defined by the moments of the body force taken with respect to the depth coordinate. As the body force becomes localized near the surface, the zeroth moment of the force dominates the radiation and is often thought of as an equivalent surface stress. However, under certain conditions, this can vanish, and the other moments must be considered. It is found that, as the order of the moment of a particular force component increases, the resulting radiation patterns alternate between those characteristic of a compressive surface stress and those characteristic of a shear surface stress, which have considerably different angular variations. Results of experiments in the development of EMAT transducers for nondestructive testing that support these results are cited, and important consequences in the design of inspection systems are indicated.