The ultimate goal of this dissertation research is to enhance the protein resistant
nature of poly(ethylene oxide) (PEO) or poly(ethylene glycol) by introduction of a
siloxane linker and to subsequently prepare coatings which prevent surface-induced
thrombosis. The hydrophobicity and flexibility of the siloxane tether should impart both
amphiphilicity and conformational mobility to the PEO chain to further decrease protein
adhesion. Because adsorption of plasma (blood) proteins initiates the clotting process,
coating surfaces based on these new PEO-silanes should prevent or significantly
diminish thrombosis. Thus, these coatings would be extremely useful for bloodcontacting
medical devices such as stents, grafts, arteriorintravenous shunts, and
biosensors.
Novel amphiphilic PEO-silanes were prepared with systematic variations to
several key structural features, including: siloxane tether length, PEO segment length,
and PEO architecture. Thus, PEO-silanes were prepared having the general formulas:
a-(EtO)3Si(CH2)2-oligodimethylsiloxanen-block-[PEO8-OCH3] (n = 0, 4, and 13; linear
architecture) and a-(EtO)3Si(CH2)2-oligodimethylsiloxanen-block-[PEOm-OCH3]2 (n = 0, 4, and 13; m = 6 and 12 branched architecture). The reactive triethoxysilane [(EtO)3Si-]
group serves as the crosslinking or grafting moiety. The PEO segment is distanced from
the (EtO)3Si- group by an oligodimethylsiloxane tether which is both hydrophobic and
exhibits a high degree of chain flexibility. Crosslinked silicone coatings and surfacegrafted
coatings were prepared with amphiphilic linear PEO-silanes (a-c). Crosslinked
silicone coatings were also prepared with branched PEO-silanes (1a-3a and 1b-3b). All
coatings showed improved resistance to common plasma proteins compared to silicone
coatings. Furthermore, protein adsorption generally decreased with siloxane tether
length.
For crosslinked PEO-modified silicone coating systems based on linear (a-c) and
branched PEO-silanes (1a-3a and 1b-3b), longer tethers enhanced PEO reorganization
to the film-water interface to enhance protein resistance. In the absence of surface
reorganization for surface grafted coatings prepared with linear PEO-silanes, longer
siloxane tethers better inhibited protein adsorption despite a moderate decrease in graft
density (sigma) and decrease in surface hydrophilicity. This indicates that longer siloxane
tethers enhance the configurational mobility of the PEO segments to better repel
proteins.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-513 |
| Date | 16 January 2010 |
| Creators | Murthy, Ranjini |
| Contributors | Grunlan, Melissa A. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation |
| Format | application/pdf |
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