Complications and facets: Innovating polymer coatings to improve medical devices

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 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 insertion-related 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.

Multi-faceted solutions reduce challenges

The complications experienced by biomaterials requires a multi-faceted approach which considers all the factors in order to provide an ideal surface which prevents the biological responses.

BioInteractions innovates high-performance biocompatible coating technologies such as Astute Antithrombogenic Coating, AvertPlus Antimicrobial Coating and Assist Lubricious Coating. Through our commitment of advancing healthcare through innovation, we have a range of proprietary polymer coatings to target the specific complications of biocompatibility. Our coatings enable medical devices to perform their intended function, as well as reduce the patient's complications throughout their therapy.

Astute Antithrombogenic Coating prevents thrombosis formation using a multi-layered approach. We have developed the coating to use an active antithrombogenic agent heparin and combined this with additional passive components to provide a high-performance, non-leaching antithrombogenic coating. Active functionalised heparin actively prevents blood activation and hinders thrombosis. The prevention of blood activation reduces the risks of a thrombus forming downstream. The additional passive components physically prevent blood components from interacting with the surface to provide an additional level of protection.

This multi-faceted approach mimics the endothelial layer to give an active antithrombogenic coating. The Astute antithrombogenic coating also prevents platelet adhesion without leaching to enhance the long-term effect. Our Astute antithrombogenic coating provides high-performance of biocompatibility whilst reducing risks and complications to the patient.

AvertPlus is a non-leaching, active antimicrobial coating, which targets a comprehensive spectrum of bacteria and prevents biofilm formation. It uses a combination of active agents and passive components to provide a contact-kill mechanism which causes cell lysis and prevents bacterial colonisation. The multi-faceted approach significantly reduces the bacterial presence and stops proteins from depositing onto the service. Our non-leaching AvertPlus coating provides a prolonged antimicrobial effect without any degradation of effect over time.

Our coating provides high-performance antimicrobial activity on a surface and has achieved a five-log reduction activity, without the use of leaching toxic compounds or anti-biotics. Our AvertPlus coating reduces the risk of device related infections without introducing the risks of toxic components to the patient.

Assist Hydrophilic Coating reduces the friction coefficient of a surface, as well as provides complementary non-thrombogenic effects. The technology is available in both UltraViolet (UV) cured and heat cured forms. This enables us to apply our technology to a variety of surfaces and geometries. The coating is thin and flexible, which enhances the coating’s stability on a device such as balloon catheters. The coating reduces friction resistance as well as preventing proteins and cells interacting with the surface to improve biocompatibility. The complementary non-thrombogenic properties provides support to the surface, enabling the coated device to remain implanted and perform for extended periods.

We can achieve a high-performance lubricious coating without leaching or the use of cytotoxic and toxic components. The technology is also available in both UV and heat-cured variants, which allows us to coat a variety of devices internally and externally to improve function. The coating activates instantly through wetting, removing the need to pre-soak the surface and reduces the preparation time. Our expertise in coating a variety of substrates and geometries allows application of the coating technology in a range of areas. Assist Hydrophilic Coating significantly reduces the friction, and instantly activates and provides complementary benefits to improve its biocompatibility.

BioInteractions innovates all its coating technologies in-house, provides optimised application processes, coating services and in-house testing services. We have combined our expertise to help our partners through the development process, and our complete coating service focuses on the main biocompatible challenges faced by the devices and the development process, resulting in the organisation providing an all-inclusive coating service.