title: Calcium-Mediated Control of Polydopamine Film Oxidation and Iron Chelation.
abstract: The facile preparation of conformal polydopamine (PDA) films on broad classes of materials has prompted extensive research into a wide variety of potential applications for PDA. The constituent molecular species in PDA exhibit diverse chemical moieties, and therefore highly variable properties of PDA-based devices may evolve with post-processing conditions. Here we report the use of redox-inactive cations for oxidative post-processing of deposited PDA films. PDA films incubated in alkaline CaCl₂ solutions exhibit accelerated oxidative evolution in a dose-dependent manner. PDA films incubated in CaCl₂ solutions exhibit 53% of the oxidative charge transfer compared to pristine PDA films. Carboxylic acid groups generated from the oxidation process lower the isoelectric point of PDA films from pH = 4.0 ± 0.2 to pH = 3.1 ± 0.3. PDA films exposed to CaCl₂ solutions during post-processing also enhance Fe2+/Fe3+chelation compared to pristine PDA films. These data illustrate that the molecular heterogeneity and non-equilibrium character of as-deposited PDA films afford control over the final composition by choosing post-processing conditions, but also demands forethought into how the performance of PDA-incorporated devices may change over time in salt solutions.
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA. lkloster@andrew.cmu.edu.
authors.forename: Luke
authors.initials: L
authors.lastname: Klosterman
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA. cbetting@andrew.cmu.edu.|Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA. cbetting@andrew.cmu.edu.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Bettinger
mesh_terms: D002118:Calcium / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007502:Iron Chelating Agents / Q000737:chemistry*; D010084:Oxidation-Reduction; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D007211:Indoles; D007502:Iron Chelating Agents; D011108:Polymers; C568283:polydopamine; D007501:Iron; D002118:Calcium
keywords: dopamine oxidation; melanin; metal cation; polydopamine; thin film