Silicone catheters modified by atomic layer deposition for neurosurgical applications

Abstract

Hydrocephalus (HCP) is an incurable medical condition that is characterized by the accumulation of cerebrospinal fluid (CSF) within the cranial cavity, which causes increased intracranial pressure on the brain. This condition affects people in every stage of life, from infants to elderly, and often leads to lesions in brain tissue. Due to a several impact on the patient's health and socioeconomic burden, HCP has been considered a huge and growing medical and social issue. The treatment for HCP is surgical and performed by the insertion of a silicone device, which function is to divert the CSF flow from the cerebral ventricles to another absorption site. In Brazil, in the two-year period between 2010 and 2012, the Unified Health System ("Sistema Único de Saúde - SUS") spent more than R$14.000.000 (US$4.200.000) on the acquisition of these devices, excluding the additional costs related to hospital admission and surgeries. This high cost is explained by the absence of national - or even international - options for implantable devices for ventricular shunts. Currently in Brazil, the only available product is Bactiseal® (produced by Codman Johnson & Johnson, Boston, MA), which has high import and commercialization costs. This catheter is produced using an antibiotic impregnation technology, which has an exclusive action against gram-positive pathogens. Thus, in addition to the high cost of commercialization of this material in Brazil, other important concerns should be highlighted, such as: i) these catheters do not present antimicrobial action against fungi and gram-negative pathogens, which have been frequently associated to severe infections with high morbidity and mortality rates; ii) this impregnated catheter has a relatively short period of protection (less than 1 month) against pathogens, but the possibility of infections conditions arising from implantation extends up to 4 months. Therefore, there is a clear urgency for the development and insertion of a national implantable device for ventricular shunts in the market, which must present reduced costs and wider spectrum of antimicrobial action. In this context, the technology known as atomic layer deposition (ALD) has gained a great attention for academic and industrial pursuits. ALD allows for the covering of 3D-surfaces with metallic oxides with microbiostatic properties, therefore preventing the adherence of microorganisms on their surfaces. Furthermore, such technique also allows the impregnation of these metallic oxides in the volume of the polymeric substrate, which facilitates the adjustment of the biocidal properties. In sum, this project proposes the design and construction of a thermal cross-flow ALD reactor with capacity for flat and 3D-substrates. Thus, it is proposed the design of a new product with a high commercial potential, based on the coating of silicon catheters with nanostructured metallic oxides (TiO2 and Al2O3), aiming at the next generation of materials with excellent microbiostatic properties and adjustable biocidal properties for neurosurgical purposes. (AU)