title: Aging of plasma-polymerized allylamine nanofilms and the maintenance of their cell adhesion capacity.
abstract: The long-term stability and γ-sterilisability of bioactive layers is the precondition for the application of implants. Thus, aging processes of a microwave deposited, plasma polymerized allylamine nanofilm (PPAAm) with positively charged amino groups were evaluated concerning physicochemical characteristics and cell adhesion capacity over the course of one year. XPS, FT-IR, surface free energy, and water contact angle measurements elucidated not only the oxidation of the PPAAm film due to atmospheric oxygen reacting with surface free radicals but also the influence of atmospheric moisture during sample storage in ambient air. Surprisingly, within 7 days 70% of the primary amino groups are lost and mostly converted into amides. A positive zeta-potential was verified for half a year and longer. Increasing polar surface groups and a water contact angle shift from 60° to 40° are further indications of altered surface properties. Nevertheless, MG-63 human osteoblastic cells adhered and spread out considerably on aged and additionally γ-sterilized PPAAm layers deposited on polished titanium alloys (Ti-6Al-4V_P). These cell-relevant characteristics were highly significant over the whole period of one year and may not be related to the existence of primary amino groups. Rather, the oxidation products, the chemical amide group, that is, seem to support the attachment of osteoblasts at all times up to one year.
authors.affiliation: Leibniz-Institute for Plasma Science and Technology (INP) , Felix-Hausdorff-Straße 2, D-17489 Greifswald, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Finke
authors.forename: Henrike
authors.initials: H
authors.lastname: Rebl
authors.forename: Frank
authors.initials: F
authors.lastname: Hempel
authors.forename: Jan
authors.initials: J
authors.lastname: Schäfer
authors.forename: Klaus
authors.initials: K
authors.lastname: Liefeith
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Weltmann
authors.forename: J Barbara
authors.initials: JB
authors.lastname: Nebe
mesh_terms: D000497:Alloys; D000499:Allylamine / Q000737:chemistry / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D020099:Coated Materials, Biocompatible / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008422:Materials Testing; D008567:Membranes, Artificial; D049329:Nanostructures / Q000737:chemistry*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010084:Oxidation-Reduction; D058626:Plasma Gases; D013997:Time Factors; D014025:Titanium / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000497:Alloys; D020099:Coated Materials, Biocompatible; D008567:Membranes, Artificial; D058626:Plasma Gases; C031462:titanium alloy (TiAl6V4); D000499:Allylamine; D014025:Titanium