COVER STORY
ARJUN LUTHRA, COMMERCIAL DIRECTOR, BIOINTERACTIONS, EXPLAINS HOW THE COMPANY IS INNOVATING POLYMER COATINGS TO IMPROVE MEDICAL DEVICES. COMPLICATIONS OF BIOMATERIAL RESPONSE Innovations in the field of medicine and surgery are in constant demand for new and improved materials to enhance the quality of the therapy. Biomaterials play a critical role in improving the biocompatibility of surfaces which improves the quality of the therapy. Biocompatibility of materials involves critical complications such as inflammation, fibrosis, infection and thrombosis. The successes of applications are dependent on a variety of biological events occurring on the surfaces and these events intensify the complications which have to be addressed during innovation. The challenges of infection and thrombosis are two significant factors which hinder long-term applications, as these biological events are potentially linked to each other and are critical to improving the performance of biomaterials. Biological responses are complex processes which are governed by a variety of factors. These factors range from surface properties which include the chemistry, topography, wettability and composition of a surface to the biological entities present at the interface. Materials used in medical devices are likely to interact with blood first, and this interaction is in itself highly complex. The contact of biomaterials and blood induce protein adsorption, platelet activation, platelet adhesion, coagulation and thrombosis. Plasma proteins adsorb onto the surface initially which leads to activation of the blood and subsequently causes additional biological responses. These responses lead to complications which impede the performance of medical devices, reduce the efficacy of therapies and
12
can cause harm to patients. Catheter thrombosis can be seen in the form of venous thrombosis or the formation of fibrin sheath which accounts for up to 40% of catheter failures. These challenges interrupt strict dialysis schedules, reduce the flow rates of catheters and can result in the use of costly measures. The reduction of flow rates has been a consistent complaint when delivering blood for dialysis. Central venous stenosis can be a devastating complication resulting in pain and disfiguring arm swelling and treatments can be used to temporarily relieve the issues; however viable surgical options are still required. Infection is likely to be the most significant challenge which impedes long-term applications. A variety of preventative techniques have proven not to be significantly effective. It has been seen in a randomised study of surface treatments to prevent infections that silver surface treatments have failed to reduce infection rates. It has also been seen that the use of silver-impregnated collagen cuffs may impede catheter fixation due to the killing of fibroblasts which can cause the catheter to dislodge. Furthermore, it has been recommended that any catheter which has caused bacteraemia should be immediately removed and only replaced once results of blood cultures are normalised. Although, there has been progress with this therapy as newly emerging strategies to treat these complications allow for medical treatment whilst the device remains in place. This approach has had limited success, requiring the use of antibiotics, and is still seen as a sceptical approach by many nephrologists. The interactions mentioned above are only a few of the many complications seen when biomaterials are used within the human body e.g. thrombosis, infection, reduced efficacy of the intended use of the device and insertionrelated complications. The complications and the biological responses are influenced by critical factors such as surface chemistry, surface energy and surface topography. Hence, the biological events which occur on a surface are complex and are a result of interactions between the surface, the proteins and cells which are present at the device-body interface
