A common material for urinary catheters is a hydrophobic polymer, silicone elastomer. The properties of silicone make it well-suited for producing medical devices; it has favourable mechanical properties and is chemically inert. However, this hydrophobic surface makes it prone to the adhesion of bacteria and subsequent and rapid formation of biofilms. The bacteria that grow in biofilms tend to be resistant to antibiotic treatment, which is a serious problem. Device-associated infections present a real challenge in modern medicine, and therefore, generating materials that resist bacterial attachment and biofilm growth is a worthwhile development for reducing the number of infections. To reduce the adhesion of bacteria and the risk of infection, at BioModics, we have produced silicone catheters and medical devices that are functionalised by the inclusion of a hydrophilic hydrogel interpenetrating polymer network (IPN). The hydrophilic polymer network is introduced by treating the hydrophobic silicone with supercritical carbon dioxide (at elevated but easily accessible temperature and pressure). This expands the silicone network, and then hydrophilic monomers are introduced to react and form an IPN within the silicone network. This hydrogel not only reduces the risk of infection, but it is also has the potential to act as a drug delivery mechanism. The IPN act as a reservoir for hydrophilic small molecules that can be suspended and then controllably released at site from the IPN-impregnated silicone. The release properties are dependent on the morphology of the IPN. However, it is a challenge to get insights to the micro structure of the IPNs. Therefore, at the University of Copenhagen, we have performed small-angle scattering measurements (with both X-rays and neutrons) to investigate the distribution of the polymer molecules within the IPN. X-ray measurements are sensitive to differences in electron density, and they primarily revealed the structure of the inorganic filler in the silicone. Neutron measurements are sensitive to isotopes, and by introducing water or heavy water (D2O) to IPN, we were able to observe the distribution of water and the hydrophilic domains. We will discuss how studies on these nanostructured materials perform as promising future medical devices and how the structure-property relationships arising from scattering measurements are assisting optimisation of the materials for the future.

Small-angle scattering of interpenetrating polymer networks (IPNs) as medical devices with reduced risk of infection

256th National Meeting (2018)

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