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The surface characterisation of hair fibres can deliver important insights into the performance of hair care products and in the development of improved product formulations based on an understanding of the connection between product use and the resulting surface properties of the treated hair fibres. This paper reviews the range of relevant hair properties together with the use of topographical and chemical surface characterisation techniques for their determination. Non-contact white light interferometry and 3D scanning electron microscopy are used to investigate topographical consequences such as scale height and hair damage. These techniques provide statistically based metrology of hair surfaces either parametrically or as quantified 3D images. In addition we describe the application of chemical surface analysis techniques including X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) to the determination of chemical residues and natural substrates in terms of material identification, level quantification and spatial distribution. In all cases practical applications are described.
In the manufacture of healthcare products and medical materials, especially ceramic materials like zirconia (used as an implant material) and hydroxyapatite (synthetic bone replacement material), there is often a stage in the manufacturing process involving a powder suspension. The behaviour of this powder suspension will correlate strongly to (a) how well it is processed and therefore (b) final yields and product performance. Surface chemistry dominates the particle-particle interactions in suspension, with different materials having different surface charges. These interactions in turn dictate suspension rheology. Zeta potential is used to investigate and monitor the surface interactions in powder suspensions, and can also be used to optimise the processing method. In a previous white paper, 'The Applications of Zeta Potential in Process Control', the in-depth theory of zeta potential was presented and discussed. This white paper will discuss its applications for the manufacture of certain healthcare materials and how Lucideon has assisted manufacturers in this area.
Powders play a very important role in many different areas of healthcare, most importantly in dentistry and orthopaedic materials, where they become either coatings or 3D structures. As many powder materials exist as suspensions in the early stages of their manufacturing, powder surface chemistry (and associated charge) can strongly influence suspensions’ rheological properties, and so the quality of subsequent processing. This can have dramatic effects on the quality of any end products and can lead to failure of these products. Given that powder surface charge is so critical, zeta potential becomes a crucial measurement for characterising and then optimising suspension behaviour. Zeta potential is essentially the energy required to shear a particle and associated ions away from a bulk solution. From these values, the stability of the system can be established: whether the particles are well dispersed and stable, or flocculated and unstable. This paper will discuss the theory of zeta potential, and how it can be measured and controlled. The particular advantages of using the ZetaProbe® apparatus available at Lucideon will also be discussed.
Gaining and maintaining regulatory approval of medical devices and materials, such as Hydroxyapatite (HA) can be a fraught, lengthy and complex process. Submission of data to regulatory bodies, for example the FDA (Food and Drug Administration), has to be credible and fully documented in order to ensure success. Post-regulatory approval testing is also important, not only to confirm that regulatory standards are continuing to be kept but also that consistency, quality and performance are being maintained.
In this white paper we look at the case for using one supplier for regulatory approval testing, using the example of HA testing.
Due to the ageing UK population, increased dynamism of people's lives and growing life expectancy, there is an increasing clinical demand for bone replacement and repair. The main mineral component of bone tissue is a nonstoichiometric carbonated multi-substituted apatite with calcium to phosphorus ratio (Ca:P) between 1.37 and 1.87. Synthetic hydroxyapatite is a popular bone replacement material because it has a similar crystal structure (Ca:P ratio fixed at 1.67) to native bone apatite. This resemblance is the origin of the excellent compatibility that HA exhibits with hard tissue and its natural bioactive behaviour; enabling it to be incorporated into the body via the same processes active in the remodelling of healthy bone.
Although polymers have been the most widely used material in the pharmaceutical and medical devices industry for many years, they are still often the root cause of many problems, such as unexpected product failure or yield deterioration. This is usually down to the complexity of polymeric materials. Chemical and physical structure can change at any stage - during manufacturing, post treatment (e.g. during sterilization), in storage, transportation or in use. The resulting changes in structure, which can range from the nano and micro up to millimetre scales, consequently affect the performance of the product. What’s more, product failures are often due to several co-existing factors. It is important, therefore, to understand the factors that can affect a polymer’s structure and, hence, its properties.
This paper will introduce the basic concepts regarding the structure and properties of polymeric materials. It will be of particular interest to engineers, technologists, scientists, technical managers and QA/QC professionals; anyone who is involved in developing new products or finding root causes of failures.
Much research has been done into developing synthetic Hydroxyapatite (HA) as materials for bone replacement, due to the fact that natural bone comprises HA. In addition, HA powders have been used as coatings on metal implants in a bid to make them more compatible with the body and to promote stronger bone-to-implant bonding and hence increased longevity of the implant (for example, in the case of femoral hip implants). This paper explores the role of (multi-element) substitution in HA and how this can impact on behaviour of HA in aqueous physiological environments.
Investment or 'lost wax' casting is a key process in the manufacture of high quality engineering components such as orthopaedic implants. The process may be applied to a wide range of metals and alloys and can be used to produce both large and small castings. The application of investment casting has seen significant growth in the last 5 years with estimates placing the current market size at $US 8.6 billion and whilst US remains the largest single producer, Asian markets account for approx 35% of this value.
This white paper examines the major issues involved with the investment casting process. The problems that can occur during pattern manufacture, shell moulding, de-waxing and casting are discussed and solutions to these problems are identified. The white paper also looks at some of the non-technical issues facing investment casting in 2011 and the future.
Stents are expandable meshed tubes used either to reinforce body vessels possessing weak walls or to increase the internal diameter of a body vessel to allow an improved flow of fluids such as blood or urine. The use of arterial stents in particular has grown significantly over the last 20 years due to an ageing population and to a change in diet which has led to an increase in cardiovascular illness. Estimates vary, but it is predicted that coronary stents will have a market value of $7.2bn by 2012 and will continue to grow at a rate of 6% per annum thereafter. In 2009 over a million US citizens received angioplasty/stent interventions.
In this paper we will review some of the technology being used in the development of new stents and how, in particular, computational modelling and material characterisation are helping to improve clinical outcomes. Finally we will look at the future perspectives for next generation stent technology.
Residues on the surface of medical devices can cause implant failure and poor device performance. The main source of these residues is from materials used in the manufacture of the device, although contamination during the storage, cleaning and handling of the device is also known to occur. Small amounts of these surface residues can cause deleterious effects in patients, because the residues are in direct contact with body tissues and patients often have compromised immune systems. In addition, residues may often alter the surface chemistry and geometry of the device, so even inert residues can be a problem. For example, small amounts of non-toxic cutting fluid on an implant limit the ability of surrounding tissues to attach to the implant.
In order to minimise contamination, the Federal Drug Administration (FDA) stipulates that medical device manufacturers follow specific cleanliness validation procedures. Firstly, they must identify all possible residues present on the device and set an acceptable residue limit. Then, they must use a cleaning regime that reduces residue levels below this limit, without leaving significant levels of cleaning agent behind. Finally documentation to verify that residue limits are not exceeded must be submitted to the FDA before the device can go on the market.
Despite these procedures being in place, some medical devices are failing to meet FDA requirements for cleanliness verification and validation. Since 2001, 173 medical devices have been recalled, some due to contamination issues. In just one year of sterility inspections, more than 483 FDA observations related to validation deficiencies - more than any other deficiency.
Surface Analysis is assisting the pharmaceutical industry in a number of ways, including for example the optimisation and acceleration of new product development, evaluation of product and packaging stability, rapid identification of trace contamination and quality assessment of new manufacturing processes. And it is certain that Surface Analysis can illuminate much more about processes, and even origins, in this sophisticated marketplace - including by helping detect counterfeits. Developments at the forefront of Surface Analysis technology are so powerful that it is enabling an independent UK research centre to materially assist pharmaceutical companies in their battle against counterfeit drugs.
Not only does this technology - the latest in X-ray Photoelectron Spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToFSIMS) in particular - afford a means of analysing the composition of various pharmaceuticals, recent work has also shown that it can even determine differences in the manufacturing processes involved, enabling the identification of previously undetectable chemical copies.
Traditionally, one thinks of Surface Analysis as being concerned principally with the physical properties of surfaces - flatness, roughness, colour, reflectivity and so on. The state-of-theart in this area is '3D non-contact profiling', where white light interferometry techniques allow examination of ‘microfeatures’. Areas from a few square microns up to the centimetre scale can be analysed with nanometre resolution.
ISO 13356 "Implants for surgery – Ceramic materials based on yttria-stabilised tetragonal zirconia (Y-TZP)" is a standard created to ensure consistent performance of Yttria- Stabilised Zirconia (YSZ) ceramics in implants for surgery. The pass limits set can already meet or be exceeded using existing, mainstream processing routes. However, with the average age of humans increasing (resulting in over-65s making up a higher percentage of the population), there is a challenge to increase the lifetime of zirconia implants towards 30 years or more. This white paper highlights some of the testing involved in ISO 13356 and discusses how recent and on-going research into ceramic processing provides opportunities to meet the challenge.