A Readily Scalable, Clinically Demonstrated, Antibiofouling Zwitterionic Surface Treatment for Implantable Medical Devices

Abstract

conditions to maintain the scale of medical device manufacturing; and 4) the treatment must not incorporate antibiotics to maintain global antimicrobial stewardship efforts. The zwitterionic polymer polysulfobetaine (PSB) was selected as the antifouling component of the surface modification to benefit from its biocompatibility, ultralow-fouling properties, and oxidative stability. By adsorbing water electrostatically, PSB coatings form a thin hydration barrier that prevents organic materials from adhering to surfaces. [22] Commonly used approaches to attach PSB coatings to surfaces, such as radical-initiated graft polymerizations of PSB-methacrylate necessitate the use of oxygen-free conditions, [23] preconditioning steps, [24] or long reaction times [25] that do not meet scalability requirements. To circumvent the use of air-free graft polymerizations, we employ perfluorophenylazide (PFPA) chemistry as a molecular anchor to link the PSB coatings onto the surfaces of polymeric materials under ambient conditions. When triggered with UV-light, PFPA moieties generate a highly reactive nitrene that forms covalent bonds with materials containing amines, CC double bonds, and CH bonds. [26,27] With this method, PSB is rapidly coated onto a broad range of substrates using UV light under ambient conditions with no preconditioning steps. Thus, many different medical devices may be quickly and conveniently treated on the manufacturing level.We first demonstrate the effect of the treatment on polydimethylsiloxane (PDMS) as an exemplary, extremely difficultto-modify model for a common elastomer used in implantable medical devices. [28] Commonly known as silicone, PDMS is widely used for its biocompatibility, good chemical stability, ease of fabrication using injection molding or extrusion, and low cost. [29][30][31] Many implantable device makers have moved away from classical medical elastomers and plastics such as latex and polyvinyl chloride due to allergens [32] or plasticizers [33] in these materials that leach out and often lead to irritation or complications. PDMS-based devices do not require plasticizers and have been shown to lead to fewer complications than latex and polyurethane-based devices. [34] Despite its ideal properties, the nonpolar nature of PDMS facilitates the adhesion of organic materials. Bacteria, platelets, proteins, and other biomolecules bind strongly to the hydrophobic surfaces of PDMS elastomers, leading to the colonization and proliferation of biofilms. [22] When common hydrophilic surface treatments are performed on PDMS, such as plasma oxidation, [35] UV-ozone, [36] or corona discharge, [37] the effects are short-term due to rapid hydrophobic recovery. The highly mobile chains of PDMS (glass transition temperature ≈ −120 °C) can reorient themselves to "hide" the surface modified elastomers, when exposed to air, within hours. [38] Other methods seeking long-lasting hydrophilic PDMS surfaces typically require preconditioning steps with silane [39][40][41] chemistry or radical polymerization. [...

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“…In general, cell adhesion to hydrophobic surfaces has been previously described by McVerry et al as due to the nonpolar nature of PDMS and the significant increase in antibacterial effect when its surface is modified to hydrophilic 15 . As the surface of PUR is naturally hydrophobic 34 but less hydrophobic than silicone, bacterial adhesion and growth in the surrounding medium are expected when there is a possibility to use the material's surface for attachment and multiplication.…”

“…Also, grafting acrylates 7 to silicone rubber (Pseudomonas, catheter) effectively suppresses non-specific protein adsorption and cell adhesion, suppressing hydrophobic recovery of the surface. One of the most recent works by McVerry et al shows a successful one-step hydrophilic surface modification in ambient conditions and under UV light to create a zwitterionic polymer polysulfobetaine and perfluorophenylazide network onto silicone surface 15 . The reported antibacterial activity was due to the formation of the surface hydration layer in the presence of the hydrophilic coating.…”

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