Adipose tissue engineering based on the controlled release of fibroblast growth factor-2 in a collagen matrix

Adipose tissue forms when basement membrane extract (Matrigel™) and fibroblast growth factor-2 (FGF-2) are added to our mouse tissue engineering chamber model. A mouse tumor extract, Matrigel is unsuitable for human clinical application, and finding an alternative to Matrigel is essential. In this study we generated adipose tissue in the chamber model without using Matrigel by controlled release of FGF-2 in a type I collagen matrix. FGF-2 was impregnated into biodegradable gelatin microspheres for its slow release. The chambers were filled with these microspheres suspended in 60 μL collagen gel. Injection of collagen containing free FGF-2 or collagen containing gelatin microspheres with buffer alone served as controls. When chambers were harvested 6 weeks after implantation, the volume and weight of the tissue obtained were higher in the group that received collagen and FGF-2 impregnated microspheres than in controls. Histologic analysis of tissue constructs showed the formation of de novo adipose tissue accompanied by angiogenesis. In contrast, control groups did not show extensive adipose tissue formation. In conclusion, this study has shown that de novo formation of adipose tissue can be achieved through controlled release of FGF-2 in collagen type I in the absence of Matrigel.

Endothelial precursor cells home to a vascularized tissue engineering chamber by application of the angiogenic chemokine CXCl12

Tissue engineering of vascularized constructs has great utility in reconstructive surgery. While we have been successful in generating vascularized granulation-like tissue and adipose tissue in an in vivo tissue engineering chamber, production of other differentiated tissues in a stable construct remains a challenge. One approach is to utilize potent differentiation factors, which can influence the base tissue. Endothelial precursor cells (EPCs) have the ability to both carry differentiation factors and home to developing vasculature. In this study, proof-of-principle experiments demonstrate that such cells can be recruited from the circulation into an in vivo tissue engineering chamber. CXC chemokine ligand 12 (CXCL12)/stromal cell-derived factor 1 was infused into the chamber through Alzet osmotic pumps and chamber cannulation between days 0 and 7, and facilitated recruitment of systemically inoculated exogenous human EPCs injected on day 6. CXCL12 infusion resulted in an eightfold increase in EPC recruitment, 2 (p = 0.03) and 7 days postinfusion (p = 0.008). Delivery of chemotactic/proliferation and/or differentiation factors and appropriately timed introduction of effective cells may allow us to better exploit the regenerative potential of the established chamber construct. © Copyright 2009, Mary Ann Liebert, Inc. 2009.

Molecular aspects of tissue engineering in the dental field

Tissue engineering is a multidisciplinary field with the potential to replace tissues lost as a result of trauma, cancer surgery, or organ dysfunction. The successful production, integration, and maintenance of any tissue-engineered product are a result of numerous molecular interactions inside and outside the cell. We consider the essential elements for successful tissue engineering to be a matrix scaffold, space, cells, and vasculature, each of which has a significant and distinct molecular underpinning (Fig. 1). Our approach capitalizes on these elements. Originally developed in the rat, our chamber model (Fig. 2) involves the placement of an arteriovenous loop (the vascular supply) in a polycarbonate chamber (protected space) with the addition of cells and an extracellular matrix such as Matrigel or endogenous fibrin (34, 153, 246, 247). This model has also been extended to the rabbit and pig (J. Dolderer, M. Findlay, W. Morrison, manuscript in preparation), and has been modified for the mouse to grow adipose tissue and islet cells (33, 114, 122) (Fig. 3)...

An endogenously deposited fibrin scaffold determines construct size in the surgically created arteriovenous loop chamber model of tissue engineering

Background: An arteriovenous loop (AVL) enclosed in a polycarbonate chamber in vivo, produces a fibrin exudate which acts as a provisional matrix for the development of a tissue engineered microcirculatory network. Objectives: By administering enoxaparin sodium - an inhibitor of fibrin polymerization, the significance of fibrin scaffold formation on AVL construct size (including the AVL, fibrin scaffold, and new tissue growth into the fibrin), growth, and vascularization were assessed and compared to controls. Methods: In Sprague Dawley rats, an AVL was created on femoral vessels and inserted into a polycarbonate chamber in the groin in 3 control groups (Series I) and 3 experimental groups (Series II). Two hours before surgery and 6 hours post-surgery, saline (Series I) or enoxaparin sodium (0.6 mg/kg, Series II) was administered intra-peritoneally. Thereafter, the rats were injected daily with saline (Series I) or enoxaparin sodium (1.5 mg/kg, Series II) until construct retrieval at 3, 10, or 21 days. The retrieved constructs underwent weight and volume measurements, and morphologic/morphometric analysis of new tissue components. Results: Enoxaparin sodium treatment resulted in the development of smaller AVL constructs at 3, 10, and 21 days. Construct weight and volume were significantly reduced at 10 days (control weight 0.337 ± 0.016 g [Mean ± SEM] vs treated 0.228 ± 0.048, [P < .001]: control volume 0.317 ± 0.015 mL vs treated 0.184 ± 0.039 mL [P < .01]) and 21 days (control weight 0.306 ± 0.053 g vs treated 0.198 ± 0.043 g [P < .01]: control volume 0.285 ± 0.047 mL vs treated 0.148 ± 0.041 mL, [P < .01]). Angiogenesis was delayed in the enoxaparin sodium-treated constructs with the absolute vascular volume significantly decreased at 10 days (control vascular volume 0.029 ± 0.03 mL vs treated 0.012 ± 0.002 mL [P < .05]). Conclusion: In this in vivo tissue engineering model, endogenous, extra-vascularly deposited fibrin volume determines construct size and vascular growth in the first 3 weeks and is, therefore, critical to full construct development.

The role of vascularization in 3-D tissue engineering

The role of vascularization in 3-D tissue engineering was studied. Mouse fat, angiogenic growth factors, adult human stem cells and fat tissue have been inserted and subsequent tissue growth was monitored. Human fat grafts or human lipoaspirates in SCID mouse chambers induced mouse fat generation at 6 weeks. Tissue engineering models utilizing intrinsic vascularization have major advantages including rapid and appropriate vascularization of new tissues.

Engineering salinity tolerance in rice by exogenous expression of cell death regulators

Rice, an important crop that feeds more than half of the world's population is very sensitive to salinity stress – a growing problem affecting crop production globally. This PhD study addressed this problem by manipulating the programmed cell death pathways in rice resulting in significant enhancement of salinity stress tolerance. The impact of this work is that farmers would be in a position to grow rice containing such a trait in environments where salinisation of the soil exists, thereby addressing food security needs.

The role of core protest group members in sustaining protest against controversial construction and engineering projects

Community-based protests against major construction and engineering projects are becoming increasingly common as concerns over issues such as corporate social accountability, climate change and corruption become more prominent in the public's mind. Public perceptions of risk associated with these projects can have a contagious effect, which mismanaged can escalate into long-term and sometimes acrimonious protest stand-offs that have negative implications for the community, firms involved and the construction industry as a whole. This paper investigates the role of core group members in sustaining community-based protest against construction and engineering projects. Using a thematic story telling approach which draws on ethnographic method and social contagion theories, it presents an in-depth analysis of a single case study - one of Australia's longest standing community protests against a construction project. It concludes that core group members play a critical role, within anarchic structures which provide a high degree of spontaneity and improvisation, in sustaining movement continuity by building collective identity, mobilising resources and a moving interface which developers find hard to communicate with.

Characterisation of the micro-architecture of direct writing melt electrospun tissue engineering scaffolds using diffusion tensor and computed tomography microimaging

This article describes the first steps toward comprehensive characterization of molecular transport within scaffolds for tissue engineering. The scaffolds were fabricated using a novel melt electrospinning technique capable of constructing 3D lattices of layered polymer fibers with well - defined internal microarchitectures. The general morphology and structure order was then determined using T 2 - weighted magnetic resonance imaging and X - ray microcomputed tomography. Diffusion tensor microimaging was used to measure the time - dependent diffusivity and diffusion anisotropy within the scaffolds. The measured diffusion tensors were anisotropic and consistent with the cross - hatched geometry of the scaffolds: diffusion was least restricted in the direction perpendicular to the fiber layers. The results demonstrate that the cross - hatched scaffold structure preferentially promotes molecular transport vertically through the layers ( z - axis), with more restricted diffusion in the directions of the fiber layers ( x – y plane). Diffusivity in the x – y plane was observed to be invariant to the fiber thickness. The characteristic pore size of the fiber scaffolds can be probed by sampling the diffusion tensor at multiple diffusion times. Prospective application of diffusion tensor imaging for the real - time monitoring of tissue maturation and nutrient transport pathways within tissue engineering scaffolds is discussed.

Social engineering in social networking sites : how good becomes evil

Social Engineering (ES) is now considered the great security threat to people and organizations. Ever since the existence of human beings, fraudulent and deceptive people have used social engineering tricks and tactics to trick victims into obeying them. There are a number of social engineering techniques that are used in information technology to compromise security defences and attack people or organizations such as phishing, identity theft, spamming, impersonation, and spaying. Recently, researchers have suggested that social networking sites (SNSs) are the most common source and best breeding grounds for exploiting the vulnerabilities of people and launching a variety of social engineering based attacks. However, the literature shows a lack of information about what types of social engineering threats exist on SNSs. This study is part of a project that attempts to predict a persons’ vulnerability to SE based on demographic factors. In this paper, we demonstrate the different types of social engineering based attacks that exist on SNSs, the purposes of these attacks, reasons why people fell (or did not fall) for these attacks, based on users’ opinions. A qualitative questionnaire-based survey was conducted to collect and analyse people’s experiences with social engineering tricks, deceptions, or attacks on SNSs.

Social engineering in social networking sites : the art of impersonation

Social networking sites (SNSs), with their large number of users and large information base, seem to be the perfect breeding ground for exploiting the vulnerabilities of people, who are considered the weakest link in security. Deceiving, persuading, or influencing people to provide information or to perform an action that will benefit the attacker is known as “social engineering.” Fraudulent and deceptive people use social engineering traps and tactics through SNSs to trick users into obeying them, accepting threats, and falling victim to various crimes such as phishing, sexual abuse, financial abuse, identity theft, and physical crime. Although organizations, researchers, and practitioners recognize the serious risks of social engineering, there is a severe lack of understanding and control of such threats. This may be partly due to the complexity of human behaviors in approaching, accepting, and failing to recognize social engineering tricks. This research aims to investigate the impact of source characteristics on users’ susceptibility to social engineering victimization in SNSs, particularly Facebook. Using grounded theory method, we develop a model that explains what and how source characteristics influence Facebook users to judge the attacker as credible.

Multivariate statistical analysis of hydrochemical data to assess alluvial aquifer–stream connectivity during drought and flood : Cressbrook Creek, southeast Queensland, Australia

A catchment-scale multivariate statistical analysis of hydrochemistry enabled assessment of interactions between alluvial groundwater and Cressbrook Creek, an intermittent drainage system in southeast Queensland, Australia. Hierarchical cluster analyses and principal component analysis were applied to time-series data to evaluate the hydrochemical evolution of groundwater during periods of extreme drought and severe flooding. A simple three-dimensional geological model was developed to conceptualise the catchment morphology and the stratigraphic framework of the alluvium. The alluvium forms a two-layer system with a basal coarse-grained layer overlain by a clay-rich low-permeability unit. In the upper and middle catchment, alluvial groundwater is chemically similar to streamwater, particularly near the creek (reflected by high HCO3/Cl and K/Na ratios and low salinities), indicating a high degree of connectivity. In the lower catchment, groundwater is more saline with lower HCO3/Cl and K/Na ratios, notably during dry periods. Groundwater salinity substantially decreased following severe flooding in 2011, notably in the lower catchment, confirming that flooding is an important mechanism for both recharge and maintaining groundwater quality. The integrated approach used in this study enabled effective interpretation of hydrological processes and can be applied to a variety of hydrological settings to synthesise and evaluate large hydrochemical datasets.

Designing atmospheric-pressure plasma sources for surface engineering of nanomaterials

Atmospheric-pressure plasma processing techniques emerge as efficient and convenient tools to engineer a variety of nanomaterials for advanced applications in nanoscience and nanotechnology. This work presents different methods, including using a quasi-sinusoidal high-voltage generator, a radio-frequency power supply, and a uni-polar pulse generator, to generate atmospheric-pressure plasmas in the jet or dielectric barrier discharge configurations. The applicability of the atmospheric-pressure plasma is exemplified by the surface modification of nanoparticles for polymeric nanocomposites. Dielectric measurements reveal that representative nanocomposites with plasma modified nanoparticles exhibit notably higher dielectric breakdown strength and a significantly extended lifetime.

Carbon nanostructures for hard tissue engineering

The primary goal in hard tissue engineering is to combine high-performance scaffold materials with living cells to develop biologically active substitutes that can restore tissue functions. This requires relevant knowledge in multidisciplinary fields encompassing chemical engineering, material science, chemistry, biology and nanotechnology. Here we present an overview on the recent progress of how two representative carbon nanostructures, namely, carbon nanotubes and graphene, aid and advance the research in hard tissue engineering. The article focuses on the advantages and challenges of integrating these carbon nanostructures into functional scaffolds for repairing and regenerative purposes. It includes, but is not limited to, the critical physico-chemical properties of carbon nanomaterials for enhanced cell interactions such as adhesion, morphogenesis, proliferation and differentiation; the novel designs of two- and three-dimensional nanostructured scaffolds; multifunctional hybrid materials; and the biocompatible aspects of carbon nanotubes and graphene. Perspectives on the future research directions are also given, in an attempt to shed light on the innovative and rational design of more effective biomedical devices in hard tissue engineering.

Nanoscale surface and interface engineering : why plasma-aided?

This contribution provides arguments why and in which cases low-temperature plasmas should be used for nanoscale surface and interface engineering and discusses several advantages offered by plasma-based processes and tools compared to neutral gas fabrication routes. Relevant processes involve nanotexturing (etching, sputtering, nanostructuring, pre-patterning, etc.) and composition/structure control at nanoscales (phases, layering, elemental presence, doping, functionalization, etc.) and complex combinations thereof. A case study in p-Si/n-Si solar cell junction exemplifies a successful use of inductively coupled plasma-assisted RF magnetron sputtering for nanoscale fabrication of a bi-layered stack of unconventionally doped highly-crystalline silicon nanofilms with engineered high-quality interfaces.