The structure and performance of collagen biomaterials : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering, Massey University, Palmerston North, New Zealand

Type I collagen materials are used in a wide range of industrial applications. Some examples include leather for shoes and upholstery, acellular dermal matrix (ADM) materials for surgical applications, and bovine pericardium for the fabrication of heart valve replacements. The structure of these materials is based on a matrix of collagen fibrils, largely responsible for the physical properties and strength of the materials. How the collagen fibrils themselves contribute to the overall bulk properties of these materials is not fully understood. The first part of this work investigates a collagen structure defect in leather, known as looseness. Looseness occurs in around 5-10% of bovine leather, and is a result of the collagen fibril layers separating during processing from raw skin to leather. A greater understanding of why looseness develops in leather and a method of detecting looseness early in processing is needed to save tanners a significant amount on wasted processing time and costs. In addition, an environmentally safe method of disposing of defect and waste leather is sort after since the current method of disposing to landfill is causing environmental concern due to the possibility of chromium leaching from leather into the soil as it biodegrades. Synchrotron based small angle X-ray scattering (SAXS) revealed that loose leather has a more aligned and layered collagen fibril arrangement, meaning there is less fibril overlap, particularly in the grain-corium boundary region. This results in larger gaps in the internal structure of loose leather compared with tight. These gaps could be detected using ultrasonic imaging in partially processed pickle and wet-blue hides as well as leather. Incorporating an ultrasound system into the leather processing line could be a viable method for identifying hides deemed to develop looseness earlier in processing, and these could be diverted down a separate processing line or removed. Disposing of waste leather by first forming biochar prior to land fill proved to be an effective way of reducing chromium from leaching into the environment. XAS revealed that heating leather to temperatures above 600°C in the absence of oxygen formed a char where chromium was bound in the stable form of chromium carbide. The stability of this structure makes chromium less available to form the toxic hexavalent form in the environment and presents a possible alternative option for environmentally safe disposal of leather. The second part to this work looks at the correlation between collagen fibril structure in a range of biomaterials in relation to material strength. Leather, ADM and pericardium are three type I collagen based materials which rely on sufficient strength to carry out their industrial and medical applications. These three materials were studied to try and identify collagen fibril characteristics that relate to high material strength. SAXS on a range of leather samples from various species revealed that collagen fibril diameter had only a small influence over material strength in bovine leather, and no correlation to strength in leather from other species. Therefore it can be said that the influence of fibril orientation on leather strength takes precedence over that of fibril diameter. Fibril diameter, d-spacing and orientation were studied in pericardium using SAXS while simultaneously applying strain. It was revealed collagen materials undergo two distinct stages of deformation when strain is applied and incrementally increased. The first stage, at low strain, involves a re-orientation of fibrils to become more aligned. When strain is increased further, the fibrils themselves take up the strain, causing fibrils to stretch and decrease in diameter. The Poisson ratio of the collagen fibrils was calculated to be 2.1 ± 0.7. This high Poisson's ratio indicates the fibrils decrease in diameter at a faster rate than they elongate with strain, and as a result the volume of the fibrils decreases. This feature of collagen could help explain some of the unique behaviours and strength of collagen based materials and could be useful for optimizing industrial applications of collagen materials. ADM materials, derived from human, porcine and bovine skin was the third collagen material studied. SAXS revealed that each species of ADM material had a slightly different collagen fibril arrangement when viewing the samples perpendicular to the surface. Human ADM was highly isotropic in arrangement, porcine was largely anisotropic, and bovine was somewhere in between the two. Bovine has a more layered fibril arrangement edge on and was the strongest material, followed by human ADM, and porcine was significantly weaker. Bovine was also the most porous material of the three. The discovery of the variations in strength, porosity and fibril arrangement between the three types of ADM materials may help medical professionals select the most suitable material for specific surgical procedures and could lead to a greater number of successful surgeries taking place

Colour, health and wellbeing: the hidden qualities and properties of natural dyes

This paper addresses the questions: Is it feasible that the chemicals present in the natural dyes of both plants and insects which in the past, man has exploited for their colour, could exhibit other properties? And; In the future will these natural colours be understood and exploited for the health and wellbeing of Mankind?Is it feasible that the chemicals present in the natural dyes and colours of both plants and insects, which in the past have been exploited for their colour, could exhibit other properties that in the future will be understood and exploited for the health and wellbeing of mankind? Historically many dye plants were once regarded to possess ‘magical properties’ with the power to heal and to keep evil away [1]. Today many of these plants that can be used for dye extraction are classified as medicinal and in recent studies have been shown to process remarkable anti-microbial, anti-fungal, anti-viral activity [2]. The cosmetic industry now employs many natural dyes due to the fact they will cause fewer side affects than the employment of synthetic dyestuffs but they can also provide extra properties such as UV protection, skin moisturising and anti-aging [3,4]. In the context of these facts, this paper asks the question: What possibilities exist within the chemical nature of certain natural dyes to help with healing and well-being and if in the future we will be wearing clothes dyed with such colours from nature that we will be able to enhance our well being as well as be fashionable?.University of Derb

Review of: 'The economist's oath: on the need for and content of professional economic ethics' by George F. DeMartino

What, if any, ethical issues arise in the practice of economics? Should advice on handling any such issues be encoded by organisations of economists, and if so how

The Path to Gun Control in America Goes through Political Philosophy

This essay argues that gun control in America is a philosophical as well as a policy debate. This explains the depth of acrimony it causes. It also explains why the technocratic public health argument favored by the gun control movement has been so unsuccessful in persuading opponents and motivating supporters. My analysis also yields some positive advice for advocates of gun control: take the political philosophy of the gun rights movement seriously and take up the challenge of showing that a society without guns is a better society, not merely a safer one

Improving translational studies: lessons from rare neuromuscular diseases

Animal models play a key role in the development of novel treatments for human disease. This is particularly true for rare diseases – defined as disorders that affect less than 1 in 2000 people in the human population – for which, very often, there are no effective methods of treatment. Pharmaceutical companies are increasingly focussing on the development of therapies for the more than 7000 rare diseases. Because the majority of these are the result of single gene disorders, the exceptional ability to manipulate the mouse genome means that many such studies will take place in the laboratory mouse. But how good are the mouse models and how useful are they in assessing the potential for translational medicine? In this Editorial, I will discuss current difficulties in translational research as well as examples of good laboratory practice and guidelines that are being implemented to improve the translational potential of animal studies in the field of neuromuscular rare diseases. This could represent a potentially useful approach for adoption by other disease fields to achieve a greater success rate in translational studies

Using Sequential Mixed Social Science Methods to Define and Measure Heritage Conservation Performance

There is no agreed-upon definition for heritage conservation performance, but it is possible to borrow ideas from the natural resource conservation field to inform this concept. Dimensions of performance can include economic, technical, and sociocultural and experiential indices. Because heritage conservation ostensibly benefits people as its primary goal, however, the values of most stakeholders ought to play a role in defining performance. Most of these values are subjective and represent sociocultural and personal meanings and tend to differ dramatically from the positivistic, fabric-centered value system of conservation experts. Measurement implies quantification, yet many sociocultural values are based on qualitative meanings that defy direct attempts at quantification. One solution for this predicament is to employ a sequential mixed-method approach where qualitative meanings are gathered from stakeholders and then these meanings are used to inform the development of a quantitative method, such as a survey instrument. In this way, while the qualitative meanings are not being directly “measured” as such, aspects of the phenomenon behind these meanings can be measured, quantified, and subjected to statistical techniques. A brief representative case study is presented as an example of how social science methodologies can help define and measure performance