Subbiyan Rajendran

Medical Textiles and Biomaterials for Healthcare

Basic biomaterials Healthcare and hygiene products Infection control and barrier materials Bandaging and pressure garments Woundcare materials Implantable devices Medical devices Smart technologies.

A study of the structure and properties of novel fabrics for knee braces

The knee is the most used joint in the human body and is also most prone to injuries. Knee braces are medical devices used in the treatment of some form of injuries providing compression and warmth to the joint thus promoting healing. They can also be used for protection in several contact sports. At the moment there are no regulations governing the textile materials used in braces. The authors believe that knitted spacer fabrics have the desirable mechanical and comfort properties which could make these materials suitable for some medical applications. Commercially available knee braces have been tested and analyzed for their mechanical as well as thermophysiological properties. A range of novel spacer fabrics have been designed, developed, and characterized for comparison with commercial products. It has been found that knitted spacers can be engineered in terms of yarn type and structure used in each of the three layers in order to match and even outperform the properties exhibited by commercially available products, such as neoprene and other knitted fabrics, including composite materials. The test results obtained for a range of existing and novel products studied in this work have been explained in terms of their raw material, structure, and finishing treatments applied to them.

Effect of Process Parameters on Layer-by-layer Self-assembly of Polyelectrolytes on Cotton Substrate

To our knowledge, the present study is the first attempt to evaluate the effect of different process parameters on the amount of polyelectrolyte adsorbed on a cotton textile substrate via sequential adsorption of negatively charged poly (styrene sulfonate) (PSS) and positively charged poly (allylamine hydrochloride) (PAH) using layer-by-layer (LBL) self-assembly nanocoating process. A considerably different polymer adsorption behaviour was observed from thick adsorbed layers to thin adsorbed layer with different degree of layer penetration and ionic pair formation over the pH range (2.5 – 9.0) studied. The amount of polyelectrolyte adsorption on cotton fabric was evaluated by measuring the colour value (K/S) of methylene blue absorbed cotton surface. Contact angle measurement revealed that the extent of binding of the oppositely charged polyions on the fabric depends on the pH of the polyelectrolyte solution and ‘zipped-up’ structure with more ion pair formation was observed at the pH range 4.5 – 6.5. At higher temperature, the amount of polyelectrolyte adsorbed within the multilayers was higher. An increased deposition of PSS and PAH was observed with increase in electrolyte (NaCl) concentration. The amount of PSS and PAH adsorption increased up to 0.03 (M) of PSS and 0.01 (M) of PAH concentrations, respectively. A dipping time of 5 min was sufficient to have a maximum deposition of the polyelectrolyte multilayers.

Development of Advanced Personal Protective Equipment Fabrics for Protection Against Slashes and Pathogenic Bacteria Part 1: Development and Evaluation of Slash-resistant Garments

Knife is the most commonly used single weapon in the UK, being 32% of the weapons used in violent incidents. Studies reveal that the majority (63.3%) of the knife-inflicted wounds were slash-type and could be disfiguring or life threatening if the blood vessels are ruptured. The stab-resistant armors currently available do not protect the arms, neck, and face as they are very rigid to be worn comfortably and are expensive and heavy for everyday use by the civilian population. The main objectives of this research program are to (a) develop and characterize a novel cut-resistant and slashproof material that is lightweight, comfortable, and efficient and (b) integrate barrier properties in such garments that would incorporate suitable antimicrobial and other suitable chemicals to provide protection against a range of microorganisms. During this research program, various composite yarns were thoroughly investigated, at different proportions, to determine the most appropriate yarn for the slashproof material. The slashproof fabric structures were developed by using knitting technology as it offers significant advantages in terms of cost, design flexibility, and versatility. The fabrics were characterized by using Home Office Scientific Development Branch (HOSDB) Slash Resistance Standard for UK Police (2006), Publication No. 48/05. The results indicate that the developed fabric meets the criteria required by the HOSDB. The article discusses the results obtained during the development of the novel slashproof material for the police, armed forces, children, and the public, that is lightweight, comfortable, and efficient, and can be utilized for long periods.

SYNTHESIS AND CHARACTERIZATION OF CHITOSAN NANOPARTICLES WITH ENHANCED ANTIMICROBIAL ACTIVITY

The present paper demonstrates how the antimicrobial properties of chitosan can be enhanced by converting it into nanoparticles of desired size and surface charge using TPP (tripolyphosphate) initiated gelation process. It has been investigated and found that ionic gelation of cationic chitosan macromolecules offers a flexible and easily controllable process for systematically and predictably manipulating the particle size and surface charge of chitosan nano-particles which is an important property for antimicrobial effect. Variations in chitosan to TPP weight ratio, pH of chitosan solution and chitosan solution concentration during nanoparticle formation were examined systematically for their effects on nanoparticle size, intensity of surface charge, so as to enable faster synthesis of chitosan nanoparticles with desired properties to have optimum antimicrobial property. The data on particle size and zeta potential was obtained by dynamic light scattering (DLS) and electrophoretic mobility measurement of the chitosan nanoparticles respectively. UV-VIS absorption of bacterial suspension was measured at 610 nm to evaluate the bacterial reduction. Solution pH of chitosan was demonstrated to be the most critical factor in controlling particle size and surface charge. At very strong acidic condition of chitosan solution, cross-linking was less resulting in lower conversion of chitosan to chitosan nanoparticles which was reaffirmed by colloidal titration of the surface groups of the chitosan nanoparticles with negatively charged polyelectrolytes poly(vinyl sulfate kalium salt). It was found that variation in size and surface charge of chitosan nanoparticles could be achieved by changing all the above mentioned process parameters and resulted in significant variation in their antimicrobial activity.

Chemical, structural and thermal changes in PET caused by solvent induced polymer crystallisation

The structural and thermal properties of solvent-induced poly(ethylene terephthalate) (PET) polyester have been investigated. Flat, high twist and spun yarns were treated with trichloroacetic acid-methylene chloride (TCAMC) mixed solvent for 5 min at about 25 °C. The treatment influenced the solvent- induced crystallisation in PET, and the high interacting power of TCAMC with PET was substantiated. An increase in X-ray crystallinity was observed in the treated flat yarn but the orientation was reduced. The variation in crystallinity was measured by X-ray and DSC techniques and is discussed. The melting and recrystallisation behaviour of the crystallites were indicated by DSC measurements. The treatment improved the crystallite stability and perfection. Flat yarn exhibited a distribution of the more stable crystals with higher heat of fusion than the respective spun and high twist yarns. The study shows that the crystalline structure reorganises to a more stable and uniform form as a result of the treatment. Double melting peaks were seen in the DSC of the high twist treated samples.

Development of a Versatile Antimicrobial Finish for Textile Materials for Healthcare and Hygiene Applications

SUMMARY This paper discusses the treatment of textile materials with a synergistic system of chemical formulation to render them antimicrobial. The recipe comprises of inorganic chemicals known to be non-toxic to human beings. The treated materials possess excellent bactericidal activity against various Gram positive and Gram negative non-spore bearing and spore bearing bacteria and the full effect has been observed upto 50 launderings. Hospital field trials using the treated bed linen, patients’ gowns and staff aprons in post-operative, gynaecology and labour wards further substantiated the antibacterial effect and the durability of the finish and the users did not experience any discomfort in using the finished materials. The dermatological patch test carried out on patients and medical staff revealed that the treated materials are safe to use and do not produce any dermatological problems such as irritation or allergy. The treatment reduces the chances of severity and propagation of ailments conveyed through fabrics and garments. It does not alter the physical properties and of course increases the tear strength and wear life of the textile materials. Besides, it protects the cellulosic fibres from microbial attack on storage. The fastness properties of the dyed items are unaffected by this treatment. In addition to healthcare and hygiene applications, the formulation can also be used as an effective antimildew agent in protecting the growth of mildew in sizing recipes and is an alternative to banned pentachlorophenol. It can also serve as a good antifungal agent against cloth damage and plant pathogenic fungi.

Studies on dyeing and structural behavior of chemically treated polyester yarns

The dyeing behavior of poly(ethylene terephthalate) based flat, high twist, and spun yarns pretreated with trichloroacetic acid-methylene chloride (TCAMC) reagent was studied. Disperse dyes having two different energy levels were employed for the dyeing work. The effect of time, temperature, and dye diffusion transition temperature (T D ) on dye uptake was analyzed. A considerable increase in equilibrium dye uptake and decrease in T D of all the treated yarns were observed. The variations in dye diffusion behavior of higher and lower molecular weight dyes and the difficulties encountered in calculating the diffusion coefficient of the dyes are discussed. The structural and morphological changes effected by the pretreatment were also investigated using XRD and SEM, respectively. The increase in lateral order of the treated yarns was noted. The possible reason for an unusual relationship between the increase in lateral order and increase in dye uptake was explained. The cross-sectional shape and swelling and the smoothening out of the fiber surface were evidenced by SEM.

Hi-tech textiles for interactive wound therapies

Abstract: The chapter discusses the physiology of wounds and their management. The classification of wounds and appropriate dressing selection for a successful wound management are outlined. High-tech wound dressings and the current state of the art novel dressings such as odour adsorbent and antimicrobial dressings are critically reviewed. The role of compression therapy in the treatment and prevention of venous leg ulceration is discussed. The merits and limitations of the current compression therapy regime and the research into the development of novel orthopaedic padding and compression bandages are highlighted.

Effect of Fibre Type and Structure in Designing Orthopaedic Wadding for the Treatment of Venous Leg Ulcers

ABSTRACT There is an urgent need to focus research and development work towards the treatment of venous leg ulcers because about 1% of the adult population suffers from active ulceration during their lifetime in the UK alone and costs the National Health Service (NHS) £600 million per annum. Similarly, venous ulceration is a common disease affecting around 1% of adult population in Australia. The direct and indirect cost of the treatment for this condition in Germany is more than DM 1 billion. In the US about 2 million working days are lost each year because of leg ulcer problems and the treatment cost is enormous. The Centre for Materials Research and Innovation (CMRI) at The University of Bolton has recognised the problem and is carrying out research with an ultimate aim of developing superior novel padding and compression bandages as well as bandaging techniques. These not only enhance the healing of venous leg ulcers but also replace the cumbersome and costly conventional four-layer bandage technique by a simple two-layer system. The paper discusses the development of padding bandages that have excellent performance and properties such as fluid absorption, wicking and uniform pressure distribution around the leg over the conventional commercial bandages. The influence of fibre type and fabric structure in enhancing the absorption, wicking and pressure distribution will also be analysed. The paper also critically appraises the testing and characterisation of existing padding bandages. The morphology of leg ulceration and the current compression therapy treatment are also discussed. Overall the paper will carry, among others, two important messages to delegates: 1) the lack of desired properties of existing commercial padding bandages; and 2) the superior properties of developed bandages that are necessary for the treatment of venous leg ulcers.