Synthesis and preliminary investigations into norbornane-based amphiphiles and their self-assembly

A range of norbornane based amphiphiles, which possess a rigid 'kink' in the centre of amphiphiles, were accessed via a concise four step synthesis. The self-assembly properties of these novel compounds were then investigated and the critical aggregation concentration (CAC), hydrodynamic diameter (DH) by dynamic light scattering (DLS) and their morphology by cryogenic transmission electron microscopy (cryoTEM) and negatively stained transmission electron microscopy (TEM) were determined. These compounds while possessing similar CAC values (50-70 μM) exhibited a wide variety of particle size (60-140 nm) and morphologies, including vesicles, cigar-shaped aggregates and rod-like micelles. Considering the similarities in molecular structure we have proposed that the unique nature of the molecular 'kink' is affecting molecular assembly in which subtle changes in molecular structure have large ramifications on aggregate size and morphology.

Synthesis of norbornane bisether antibiotics via silver-mediated alkylation

A small series of norbornane bisether diguanidines have been synthesized and evaluated as antibacterial agents. The key transformation-bisalkylation of norbornane diol 6-was not successful using Williamson methodology but has been accomplished using Ag2O mediated alkylation. Further functionalization to incorporate two guanidinium groups gave rise to a series of structurally rigid cationic amphiphiles; several of which (16d, 16g and 16h) exhibited antibiotic activity. For example, compound 16d was active against a broad range of bacteria including Pseudomonas aeruginosa (MIC = 8 µg/mL), Escherichia coli (MIC = 8 µg/mL) and methicillin-resistant Staphylococcus aureus (MIC = 8 µg/mL).

Norbornane-based peptidomimetics as antibacterial agents

 A library of norbornane-based peptide mimetics have been synthesised and shown to exhibit antibacterial activity against a range of troublesome Gram-positive and Gram-negative bacterial pathogens.

Compressibility of porous magnesium foam: dependency on porosity and pore size

Mechanical properties of porous magnesium with the porosity of 35–55% and the pore size of about 70–400 μm are investigated by compressive tests focusing on the effects of the porosity and pore size on the Young's modulus and strength. Results indicated that the Young's modulus and peak stress increase with decreasing porosity and pore size. The mechanical properties of the porous magnesium were in a range of those of cancellous bone. Therefore, it is suggested that the porous magnesium is one of promising scaffold materials for hard tissue regeneration.

Molecular recognition of DNA by rigid [n]-polynorbornane-derived bifunctional intercalators: synthesis and evaluation of their binding properties

We have exploited the concept of multivalency in the context of DNA recognition, using novel chemistry to synthesize a new type of bis-intercalator with unusual sequence-selectivity. Bis-intercalation has been observed previously, but design principles for de novo construction of such molecules are not known. Our compounds feature two aromatic moieties projecting from a rigid, polynorbornane-based scaffold. The length and character of the backbone as well as the identity of the intercalators were varied, resulting in mono- or divalent recognition of the double helix with varying affinity. Our lead compound proved to be a moderately sequence-selective bis-intercalator with an unwinding angle of 27 and a binding constant of about 8 M. 9-Aminoacridine rings were preferred over acridine carboxamides or naphthalimides, and a rigid [3]-polynorbornane scaffold was superior to a [5]-polynorbornane. The flexibility of the linker connecting the rings to the scaffold, although less influential, could affect the strength and character of the DNA binding.

syn-Facial hetero-bridged [n]polynorbornanes : a new class of polarofacial framework molecules composed of fused 7-oxa- and 7-azanorbornanes

New oxygen-bridged norbornane-fused cyclobutene epoxides and bis-(cyclobutene epoxides) are described and shown to react stereoselectively with 7-azanorbornenes to produce syn-facial N,O-bridged polynorbornanes and stereorandomly with 7-oxanorbornenes to produce O,O-bridged polynorbornanes as mixtures of syn-facial and anti-facial products.[1] Polarofacial systems containing up to six syn-facial norbornane bridges are described, while systems with seven co-facial oxygen atoms have been prepared by incorporating terminal epoxide rings to O5-[5]polynorbornanes. Ester-substituted 1,3,4-oxadiazoles are shown to be useful reagents for coupling 7-oxanorbornanes and produce predominantly syn-facial O-bridged polarofacial systems together with their anti-facial isomers.

Rethinking doctoral publication practices : writing from and beyond the thesis

This article addresses the importance of giving greater pedagogical attention to writing for publication in higher education. It recognizes that, while doctoral research is a major source of new knowledge production in universities, most doctoral students do not receive adequate mentoring or structural support to publish from their research, with poor results. Data from a case study of graduates in science and education are examined to show how the different disciplinary and pedagogic practices of each discourse community impact on student publication. It is argued that co-authorship with supervisors is a significant pedagogic practice that can enhance the robustness and know-how of emergent scholars as well as their publication output. There is a need, however, to rethink co-authorship more explicitly as a pedagogic practice, and create more deliberate structures in subject disciplines to scaffold doctoral publication - as it is these structures that influence whether graduates publish as informed professionals in their chosen fields of practice.

Bone formation following implantation of titanium sponge rods into humeral osteotomies in dogs : a histological and histometrical study

Background: Titanium (Ti) is widely proven to enhance bone contact and growth on its surface. It is expected that bone defects could benefit from Ti to promote healing and to increase strength of the implanted area.

Purpose: The present study aimed at comparing the potential of porous Ti sponge rods with synthetic hydroxyapatite (HA) for the healing of bone defects in a canine model.

Material and Methods: Six mongrel dogs were submitted to three trephined osteotomies of 6.0 × 4.0 mm in one humerus and after 2 months another three osteotomies were performed in the contralateral humerus. A total of 36 defects were randomly filled either with Ti foam, particulate HA, or coagulum (control). The six animals were killed 4 months after the first surgery for histological and histometrical analysis.

Results: The Ti-foam surface was frequently found in intimate contact with new bone especially at the defect walls. Control sites showed higher amounts of newly formed bone at 2 months – Ti (p = 0.000) and HA (p = 0.009) – and 4 months when compared with Ti (p = 0.001). Differently from HA, the Ti foam was densely distributed across the defect area which rendered less space for bone growth in the latter's sites. The use of Ti foams or HA resulted in similar amounts of bone formation in both time intervals. Nevertheless, the presence of a Ti-foam rod preserved defect's marginal bone height as compared with control groups. Also, the Ti-foam group showed a more mature bone pattern at 4 months than HA sites.

Conclusion: The Ti foam exhibited good biocompatibility, and its application resulted in improved maintenance of bone height compared with control sites. The Ti foam in a rod design exhibited bone ingrowth properties suitable for further exploration in other experimental situations.

Current developments and future challenges for the creation of aortic heart valve

The concept of tissue-engineered heart valves offers an alternative to current heart valve replacements that is capable of addressing shortcomings such as life-long administration of anticoagulants, inadequate durability, and inability to grow. Since tissue engineering is a multifaceted area, studies conducted have focused on different aspects such as hemodynamics, cellular interactions and mechanisms, scaffold designs, and mechanical characteristics in the form of both in vitro and in vivo investigations. This review concentrates on the advancements of scaffold materials and manufacturing processes, and on cell–scaffold interactions. Aside from the commonly used materials, polyglycolic acid and polylactic acid, novel polymers such as hydrogels and trimethylene carbonate-based polymers are being developed to simulate the natural mechanical characteristics of heart valves. Electrospinning has been examined as a new manufacturing technique that has the potential to facilitate tissue formation via increased surface area. The type of cells utilized for seeding onto the scaffolds is another factor to take into consideration; currently, stem cells are of great interest because of their potential to differentiate into various types of cells. Although extensive studies have been conducted, the creation of a fully functional heart valve that is clinically applicable still requires further investigation due to the complexity and intricacies of the heart valve.

Shifting shadows in postmodern communities

Postmodern society frequently presents new technologies and ways of doing things. The definition of community has been reshaped by the impact of globalisation. Distances have been reduced by people’s ability to access various types of technology. Many nations foster Lifelong Learning because education is believed to be ‘one of the principal means available to foster a deeper and more harmonious form of human development’ (Delors 1996: un). Networking among communities and/or stakeholders links social and educational resources. In Victoria, initiatives such as the Local Learning and Employment Network (LLEN) have resulted in networks of local stakeholders to scaffold the school to work transition. Schools, Adult Community Education (ACE) providers and Technical and Further Education (TAFE) providers have networked to provide alternative pathways to further education or work for young people in years 11 and 12. However, despite the intent of lifelong learning to overcome exclusion and increase social capital, Bauman (1998) indicates that the freedoms of postmodernity may result in feelings of powerlessness, as previously secure spaces become destabilised. This paper, drawing on the theories of Bauman, discusses some consequences that the shifting of local and global boundaries has on communities and asks if lifelong learning meets the challenges of postmodernity.

Understanding quality and equity of schooling in Scotland : locating educational traditions globally

This paper provides a descriptive analysis of the OECD’s (2007) national report on Scottish education, Quality and equity of schooling in Scotland, while also briefly considering the Scottish government’s Diagnostic Report, prepared for the review. The national report is situated against Scottish traditions of schooling, particularly the view that access to academic curricula for all is a democratic and egalitarian approach, and also set against the changing role of the OECD. On the latter, the paper argues that the OECD, in the context of globalisation, has become more of a policy actor in its own right, in addition to its more traditional think-tank function. The OECD is a now significant transnational policy actor in education, contributing to the emergent global education policy field. The overarching argument proffered is that debates provoked by the OECD’s report, for example the David Raffe/Richard Teese exchange in the Scottish Educational Review, 40(1), 2008, stem from tensions between the new supranational expression of political and policy authority as articulated in the OECD’s report and that located more traditionally within the nation. The academic curricula for all, the Scottish tradition, is challenged by the OECD report, which supports more diverse curricula provision, including more vocational education in schools, particularly at the post-compulsory phase. We note, drawing on theoretical and empirical insights of Bourdieu, that the success of the former demands pedagogies which scaffold for those students not possessing the requisite cultural capitals for success with academic curricula, while the latter demands a strategic effort to ensure parity of esteem between different curricular provisions.

Ti6Ta4Sn alloy and subsequent scaffolding for bone tissue engineering

Porous titanium (Ti) and titanium alloys are promising scaffold biomaterials for bone tissue engineering, because they have the potential to provide new bone tissue ingrowth abilities and low elastic modulus to match that of
natural bone. In the present study, a new highly porous Ti6Ta4Sn alloy scaffold with the addition of biocompatible alloying elements (tantalum (Ta) and tin (Sn)) was prepared using a space-holder sintering method. The
strength of the Ti6Ta4Sn scaffold with a porosity of 75% was found to be significantly higher than that of a pure Ti scaffold with the same porosity. The elastic modulus of the porous alloy can be customized to match that of
human bone by adjusting its porosity. In addition, the porous Ti6Ta4Sn alloy exhibited an interconnected porous structure, which enabled the ingrowth of new bone tissues. Cell culture results revealed that human SaOS₂
osteoblast-like cells grew and spread well on the surfaces of the solid alloy, and throughout the porous scaffold. The surface roughness of the alloy showed a significant effect on the cell behavior, and the optimum surface
roughness range for the adhesion of the SaOS2 cell on the alloy was 0.15 to 0.35 mm. The present study illustrated the feasibility of using the porous Ti6Ta4Sn alloy scaffold as an orthopedic implant material with a special
emphasis on its excellent biomechanical properties and in vitro biocompatibility with a high preference by osteoblast-like cells.

Electrospinning of nanofibres for construction of vital organ replacements

This paper described the production of a novel biosynthetic material using the manufacturing technique of electro spinning for the construction of scaffold for organ replacement. This electrostatic technique uses an electric field to control the deposition of polymer fibres onto a specific substrate to fabricate fibrous polymer constructs composed of fibre diameters ranging from several microns down to 100 nm or less. Two areas of research, in particular, heart valve leaflets and blood vessel will be discussed. Here, a sandwich structure nanofibre mesh was used to construct materials for leaflets of heart valve and blood vessel. In the case of heart valve leaflet, the randomly oriented polyurethane nanofibres were prepared as the first layer, followed by gelatin-chitosan complex layer. Complex nanofibres were initially used to spin on the PU layer with cross orientation to mimic the fibrosa layer. A gelatin and chitosan complex was then spun onto the other side of PU nanofibre mesh to mimic the ventricularis layer. This particular sandwich structure using the PU layer was designed to simulate the mechanical properties of natural tissue. In addition, this design was aimed to provide good biocompatibility and improved cellular environment to assist in adhesion and proliferation. Smooth muscle cells adhered and flattened out onto the surface of the gelatin-chitosan complex as early as 1 day post seeding. There is great potential for this biosynthetic biocompatible nanofibrous material to be developed for various clinical applications.