Novel nitric oxide (NO) releasing polymers to combat thrombosis and infection
Elizabeth J. Brisbois
University of Central Florida
Blood-contacting devices, such as catheters and complex extracorporeal artificial organs, suffer from two major clinical problems: 1) platelet activation leading to thrombosis, and 2) infection. One approach to improving the hemocompatibility of blood-contacting devices is to develop materials that release nitric oxide (NO). Nitric oxide is an endogenous gas molecule produced by nitric oxide synthase (NOS) enzymes that has several key biological roles. Healthy endothelial cells exhibit a NO surface flux of 0.5 – 4.0 x10-10 mol cm-2 min-1 that inhibits platelet adhesion and activation. Macrophages also release NO that acts as a potent natural antimicrobial agent. Polymeric materials that mimic this NO release are expected to have similar antithrombotic and antimicrobial properties. In this presentation, examples of incorporating NO donor molecules such as diazeniumdiolates (NONOates) or S-nitrosothiols (RSNOs) in biomedical grade polymers will be discussed, including new methods to modify existing polymeric medical devices (e.g., catheters) with NO donor molecules via a solvent swelling technique. These new materials are used to fabricate “prototype” intravascular catheters and extracorporeal circuits, and further evaluated for the hemocompatibility and antimicrobial activity via short-term (4 h) and long-term (1-2 weeks) in vivo experiments using clinically relevant animal models.
Modular functionalization of polymeric β-ketoesters via dynamic enamine chemistry
Michael B. Sims, Jacob J. Lessard, Lian Bai, Brent S. Sumerlin
The George & Josephine Butler Polymer Research Laboratory, University of Florida
Post-polymerization modification has emerged as a powerful tool for functional polymer synthesis, complementing the suite of controlled polymerization techniques. The recent development of highly rapid, efficient, and mild functionalization reactions has greatly improved the diversity of readily accessible macromolecular structures, and there remains significant interest in further expanding the synthetic toolbox available to polymer chemists. In this work, we outline the utility of the reaction between primary amines and β-ketoesters for post-polymerization modification via the formation of robust enamine linkages. Commercially available 2-(acetoacetoxy)ethyl methacrylate (AAEMA) was polymerized under RAFT conditions to yield well-defined polymers bearing pendent β-ketoester moieties. These polymers could then rapidly functionalized with a variety of primary amines under very mild conditions, and the structure of the attached functionality was found to strongly influence the physical properties of the resultant polymers. In a representative example, the functionalization of polyAAEMA with benzylamine resulted in an increase of the glass transition temperature from 11 °C to 50 °C. As enamines are dynamic-covalent linkages, we furthermore investigated the conditions that would enable the exchange of one functionality for another, enabling dynamic modification of the polymers’ physical and chemical properties.
Synthesis and Characterization of Nature-derived Polymers with Potential to Replace Commodity Plastics
Olivier Nsengiyumva, Stephen A. Miller
George & Josephine Butler Polymer Research Laboratory, Center for Macromolecular Science & Engineering, Department of Chemistry, University of Florida, Gainesville, FL 32611, USA.
Over the last century, the commercial plastic industry burgeoned with a variety of finite resources allocated to polymer production. However, with their increased production and usage came a plethora of negative consequences to the environment, notably the inability of these polymers to degrade when disposed and only a small percentage being recycled. In addition, fossil fuel resources are dwindling, the key resource of most commercial polymers. This presentation will focus on new methods to access monomers from nature, and thus using them to synthesize renewable polymers. “Silicon acetal metathesis polymerization (SAMP)” is a methodology where silicon-based monomers and diols derived from plants are used to synthesize polysilicon acetals with glass transitions temperatures higher than that of polydimethylsiloxane (PDMS) and with relatively high melting points. SAMP also avoids the formation of deleterious byproducts such as corrosive acid (HCl). Other nature-derived monomers have also been used with the aim of replacing other non-renewable commodity plastics.