Picosecond Laser Ablation of Polyhydroxyalkanoates (PHAs): Comparative Study of Neat and Blended Material Response

Polyhydroxyalkanoates (PHAs) have emerged as a promising biodegradable and biocompatible material for scaffold manufacturing in the tissue engineering field and food packaging. Surface modification is usually required to improve cell biocompatibility and/or reduce bacteria proliferation. Picosecond laser ablation was applied for surface micro structuring of short- and medium-chain length-PHAs and its blend. The response of each material as a function of laser energy and wavelength was analyzed. Picosecond pulsed laser modified the surface topography without affecting the material properties. UV wavelength irradiation showed halved ablation thresholds compared to visible (VIS) wavelength, revealing a greater photochemical nature of the ablation process at ultraviolet (UV) wavelength. Nevertheless, the ablation rate and, therefore, ablation efficiency did not show a clear dependence on beam wavelength. The different mechanical behavior of the considered PHAs did not lead to different ablation thresholds on each polymer at a constant wavelength, suggesting the interplay of the material mechanical parameters to equalize ablation thresholds. Blended-PHA showed a significant reduction in the ablation threshold under VIS irradiation respect to the neat PHAs. Picosecond ablation was proved to be a convenient technique for micro structuring of PHAs to generate surface microfeatures appropriate to influence cell behavior and improve the biocompatibility of scaffolds in tissue engineerin

Rhododendrons Beyond just beautiful flowers

The alarm went off, as always, at 4 a.m. The first thing I did was to head for the door to check out the day’s weather so I could plan my schedule, which would inevitably be determined by the nature of the clouds. In Sikkim, a small region in the Eastern Himalaya, everyone’s life had to be adjusted to unpredictable weather. In my case, I quickly discovered that at high-altitudes, a field researcher had to take advantage of every sunny day, particularly if she was studying plant-pollinator interaction involving Rhododendrons, possibly the most exquisite flowers on the plane

Characterisation of Resistance to Everolimus in Acute Lymphoblastic Leukemia

Acute Lymphoblastic Leukemia (ALL) is the most common childhood cancer. Disease relapse following treatment still occurs in a significant minority of children and the majority of adult patients. The inability to further intensify current treatments due to dose limiting toxicities of chemotherapeutic agents demands the development of new agents. One exciting new treatment, is the mTOR inhibitor everolimus. Preclinical studies using everolimus, while promising, revealed that resistance can emerge following prolonged treatment in vivo. This study uses ALL xenografts that have developed resistance to everolimus by long-term exposure ¬in vivo. This unique resource, combined with proteomic and transcriptome sequencing technology, allows a global approach to analyse the complex biological mechanisms behind the development of resistance to everolimus in ALL. The expression of RNA and protein, the cell cycle distribution of everolimus resistant xenografts as well as the Kaplan Meier survival curves was vastly different between the two ALL xenografts analysed in this study. This indicates that resistance to everolimus is likely to have developed through different mechanisms. The cell cycle distribution of everolimus resistant ALL xenografts also differed depending on the tissues from which they were isolated. Leukemia cells may home to different tissue specific microenvironments that express specific factors that support ALL growth and survival to varying degrees. Furthermore, while individual genes were dissimilar between the two xenografts, there was a common regulation in pathways involved in cellular adhesion and the cytoskeleton. Proteomic sequencing identified 3 proteins possibly involved in everolimus resistance; PDLIM1, Vimentin and Stathmin-1. These proteins are involved with the cytoskeleton and may have a role in the adhesion, migration and cell cycle, yet their exact role in the development of resistance to everolimus is yet to be confirmed. We were unable to correlate the possible mechanisms of resistance identified in the murine model to ALL patients after acute everolimus exposure. We identified a decrease in the expression of the oncogenic micro-RNA, miR-21, though, this was likely due to the immunosuppressive effects of everolimus and did not correlate to patient outcome

A critical analysis of the concept and extent of base erosion and profit shifting, and its impact on South Africa versus Australia

Tax avoidance by multinational enterprises is the focus of much media and political scrutiny. It is also the subject of a major Organisation for Economic Co-operation and Development (OECD) project called Base Erosion and Profit Shifting (BEPS). The objective of this thesis was to gain a greater understanding of BEPS, particularly in a South African and Australian context, and to determine whether BEPS is as great a problem as the OECD portrays. A detailed analysis of the OECD BEPS Report and Action Plan was undertaken to understand what the term BEPS means. A review of current BEPS literature was then performed toassess the extent of BEPS. This was followed by a comparative analysis of South Africa and Australia, including a comparison of their tax systems and various economic indicators. It was found that there is no simple definition of BEPS. It encompasses the spectrum of international tax planning strategies used by multinational enterprises. Furthermore, these tax strategies are usually legal, which makes measuring the extent of BEPS conceptually difficult. Despite being legal, many observers believe that BEPS behaviour by multinational enterprises is ethically unacceptable. This thesis also discussed the ethics of tax avoidance, and argued that countries should assess BEPS with reference to the many benefits which multinationals bring to a country. The benefits of multinational enterprise activity are especially important to developing countries like South Africa. Despite similar tax systems, South Africa and Australia vary greatly in terms of their economic and social position. This thesis concluded that South Africa, as a developing country, is more likely than Australia to tolerate BEPS behaviour in order to maintain or even attract foreign investment. The OECD Action Plan calls for urgent internationally coordinated actions against BEPS. It appears, however, that much more research is needed on the nature and extent of BEPS before countries formulate their response. This thesis acknowledges that aggressive tax planning by multinational enterprises does exist, but suggests that countries approach BEPS, and any estimates of its extent, with a degree of caution

The Gender Equality in Research Scale: A tool for monitoring and encouraging progress on gender integration in research for and in development.

This brief discusses a monitoring and learning tool – the Gender Equality in Research Scale (GEIRS) – designed to assess the level of gender integration across a CRP’s research portfolio and at different stages of the research and development cycle

Biosynthesis of polyhydroxyalkanoates, their novel blends and composites for biomedical applications

Polyhydroxyalkanoates (PHAs) are a family of polyhydroxyesters of 3-, 4-, 5- and 6- hydroxyalkanoic acids produced by bacterial fermentation in a nutrient limiting conditions with excess carbon. They can be produced easily using renewable carbon sources. They are biodegradable and biocompatible in nature. Their physical properties are highly tailorable and a range of desired properties can be achieved based on the type of application. Owing to these properties, there has been a considerable interest in the commercial exploitation of PHAs, particularly for biomedical applications. The main aim of this research project was to produce MCL-PHAs from Pseudomonas mendocina and use them for biomedical applications. In this study, an economical production of MCL-PHAs using renewable and cheap carbon sources such as sugarcane molasses, biodiesel waste and pure glycerol was carried out. Maximum PHA yield of 43.2% dcw was obtained in the media containing biodiesel waste. The results demonstrated the successful utilisation of these cheap carbon sources by P. mendocina for the economical production of MCL-PHAs. One of the main objectives of this project was to utilize the PHAs produced for biomedical applications. Multifunctional novel 2D P(3HO)/bacterial cellulose composite films were developed for their potential use in tissue engineering applications. Chemically modified bacterial cellulose microcrystals were used as the reinforcing agent to improve the properties of P(3HO). Mechanical properties such as the Young’s modulus and tensile strength values of the P(3HO)/bacterial cellulose composite films were significantly higher in comparison to the neat P(3HO) film. Also, the composite film had a rougher and more hydrophilic surface compared to the neat P(3HO) film. It is known from literature that surface roughness and hydrophilicity affects protein adsorption on the surface of the biomaterial. Protein adsorption, in turn, plays an important role in determining the biocompatibility of a material being used for medical applications (Das et al., 2007). In this study, protein adsorption was higher in the P(3HO)/25% bacterial cellulose composite film compared to the neat P(3HO) film. In vitro biocompatibility studies using Human microvascular endothelial cells (HMEC-1) was carried out. Both neat and composite films were able to support the proliferation of HMEC-1 cells. However, the biocompatibility of the P(3HO)/25% bacterial cellulose composite films had increased. The cell proliferation significantly higher on the P(3HO)/25% bacterial cellulose composite film as compared to the neat P(3HO) film on day 7. In addition, multifunctional 2D P(3HO)/P(3HB) blend films with varying percentages of P(3HO) and P(3HB) were developed and assessed for their suitability in the development of biodegradable stents. Mechanical, thermal and microstructural properties of the P(3HO)/P(3HB) blends were characterised. The results highlighted the role of P(3HB) in enhancing the mechanical properties and thermal stability of the blend films compared to the neat P(3HO) films. However, the results suggested that the mechanical properties of the P(3HO)/P(3HB) had to be further improved to meet the desired values required for the development of a biodegradable stent. The overall protein adsorption and % cell viability was significantly higher in the blend films compared to the neat P(3HO) film. Hydrolytic degradation was faster in the blend films and the degradation rate could potentially be tailored to achieve the optimum rate required for a particular medical application. From the literature, it is known that the surface topography determines the compatibility of a biomaterial by governing important processes such as wettability, protein adsorption, cell adhesion and proliferation (Duncan et al., 2007). In this part of the study, P(3HO)/P(3HB) 50:50 blend films were micropatterned using the laser micropatterning technique to improve their biocompatibility. The results demonstrated an increase in hydrophilicity and protein adsorption on the micropatterned blend films compared to the plain P(3HO)/P(3HB) 50:50 blend films. Cell attachment, proliferation and alignment was significantly higher on the micropatterned blend films compared to the P(3HO)/P(3HB) 50:50 blend films which was a desirable outcome. Furthermore, an investigation of the P(3HO)/P(3HB) 50:50 2D films as the base material for the development of a drug eluting biodegradable stent was carried out by incorporating aspirin within the film. The percentage viability of the HMEC-1 cells was higher in the blend films with aspirin compared to the blend films without aspirin indicating an increased biocompatibility of the P(3HO)/P(3HB) 50:50 blend film containing aspirin. Controlled release of aspirin was observed without any burst release and 96.6% release was achieved within 25 days, ideal for the development of biodegradable drug eluting stents. Finally, a drug delivery system for the controlled delivery of aspirin was successfully developed. In this part of the study, 2D solvent cast films and microspheres (average size=30 μm) were developed using P(3HB). Drug release pattern from P(3HB) films as well as P(3HB) microspheres were monitored. The results demonstrated that the P(3HB) films with aspirin were suitable for sustained long term drug release whereas P(3HB) microspheres with aspirin were more suitable for fast release. In conclusion, this project has led to the successful production of PHAs, and their utilisation in the development of a range of composites, blends and drug elution structures with promising potential medical applications

Beyond dichotomies: Gender and intersecting inequalities in climate change studies

Climate change and related adaptation strategies have gender-differentiated impacts. This paper reviews how gender is framed in 41 papers on climate change adaptation through an intersectionality lens. The main findings show that while intersectional analysis has demonstrated many advantages for a comprehensive study of gender, it has not yet entered the field of climate change and gender. In climate change studies, gender is mostly handled in a men-versus-women dichotomy and little or no attention has been paid to power and social and political relations. These gaps which are echoed in other domains of development and gender research depict a ‘feminization of vulnerability’ and reinforce a ‘victimization’ discourse within climate change studies. We argue that a critical intersectional assessment would contribute to unveil agency and emancipatory pathways in the adaptation process by providing a better understanding of how the differential impacts of climate change shape, and are shaped by, the complex power dynamics of existing social and political relations

The Cavendish Living lab - a multidisciplinary, vertically integrated project focused on sustainability

Colleagues from the School of Life Sciences will present findings from The Cavendish Living Lab’: a 2 year vertically integrated project (VIP) that focuses on co-creating sustainable solutions with the student participants from various disciplines and levels. Through applied research and learning within an authentic setting, the ‘Living Lab’ approach uses our university campus as the laboratory, and a platform for the students to partner with various stakeholders to address real world issues and develop innovative, sustainable solutions to problems such as food waste, plastic waste, and waste water