title: Controlled drug release through a plasma polymerized tetramethylcyclo-tetrasiloxane coating barrier.
abstract: A plasma polymerized tetramethylcyclo-tetrasiloxane (TMCTS) coating was deposited onto a metallic biomaterial, 316 stainless steel, to control the release rate of drugs, including daunomycin, rapamycin and NPC-15199 (N-(9-fluorenylmethoxy-carbonyl)-leucine), from the substrate surface.  The plasma-state polymerized TMCTS thin film was deposited in a vacuum plasma reactor operated at a radio-frequency of 13.56 MHz, and was highly adhesive to the stainless steel, providing a smooth and hard coating layer for drugs coated on the substrate. To investigate the influence of plasma  coating thickness on the drug diffusion profile, coatings were deposited at various time lengths from 20 s to 6 min, depending on the type of drug. Atomic force spectroscopy (AFM) was utilized to characterize coating thickness. Drug elution was measured using a spectrophotometer or high-performance  liquid chromatography (HPLC) system. The experimental results indicate that plasma polymerized TMCTS can be used as an over-coating to control drug elution at the desired release rate. The drug-release rate was also found to be dependent on the molecular weight of the drug with plasma coating  barrier on top of it. The in vitro cytotoxicity test result suggested that the TMCTS plasma coatings did not produce a cytotoxic response to mammalian cells. The non-cytotoxicity of TMCTS coating plus its high thrombo-resistance and biocompatibility are very beneficial to drug-eluting  devices that contact blood.
authors.affiliation: BioSurface Engineering Technologies (BioSET), Inc., 9430 Key West Avenue, Rockville, MD 20850, USA.
authors.forename: Shigemasa
authors.initials: S
authors.lastname: Osaki
authors.forename: Meng
authors.initials: M
authors.lastname: Chen
authors.forename: Paul O
authors.initials: PO
authors.lastname: Zamora
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D020099:Coated Materials, Biocompatible / Q000737:chemistry* / Q000633:toxicity; D003692:Delayed-Action Preparations; D004058:Diffusion; D004337:Drug Carriers / Q000737:chemistry*; D051379:Mice; D058626:Plasma Gases / Q000737:chemistry*; D058105:Polymerization; D011312:Pressure; D012833:Siloxanes / Q000737:chemistry*
chemical_list: C505111:1,3,5,7-tetramethylcycloterasiloxane; D020099:Coated Materials, Biocompatible; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D058626:Plasma Gases; D012833:Siloxanes