(194b) Invited: “Multilayered” Approaches to the Design of Stable, Unstable, and Reactive Biointerfaces

Methods for the stepwise, layer-by-layer deposition of polymers on surfaces have had an enormous impact on the design of nanostructured surfaces and interfaces for biomedical and biotechnological applications. Most conventional approaches to layer-by-layer assembly exploit interactions between oppositely charged polymers to design thin polyelectrolyte-based films (‘polyelectrolyte multilayers’) held together by multivalent weak interactions. This approach allows the fabrication of polymer-based films on an incredibly varied range of surfaces (including the topographically complex surfaces of common biomedical devices), and it provides precise, nanometer-scale control over both film thickness and composition. These methods are also particularly well suited for the incorporation of bioactive species (such as proteins, peptides, and DNA) and, thus, also provide opportunities to design functional biointerfaces that provide new levels of control over the immobilization, presentation, and release of these agents from surfaces. The first part of this presentation will describe our work on the design and fabrication of nanostructured and ultrathin coatings useful for the delivery of DNA, with a focus on (i) fundamental aspects related to the design and characterization of films that erode and disintegrate in physiological media, and (ii) the ability of these ultrathin coatings to release or locally transfer therapeutic DNA constructs from the surfaces of interventional devices and promote beneficial physiological responses in vivo. We have also developed new methods for the “reactive” or “covalent” layer-by-layer assembly of polymer multilayers. These methods exploit interfacial reactions between mutually reactive polymers (as opposed to electrostatic interactions between oppositely charged polymers) and, thus, lead to polymer multilayers that are covalently crosslinked and physically stable. These methods preserve many of the key practical advantages of layer-by-layer assembly but, importantly, also result in films containing reactive groups that can be used to further decorate or pattern surfaces with chemical or biological functionality. The second part of this presentation will describe our work on the design of azlactone-functionalized multilayers as reactive platforms for the design, fabrication, and selective functionalization of new nano-biointerfaces that control, confine, and manipulate cell growth, provide new substrates for the automated and multi-step synthesis of complex biomolecules, and enable the design of reactive superhydrophobic surfaces that open new opportunities for the application of these extremely non-wetting materials in biotechnological contexts.