C O M M U N I C A T I O N S
ether as a novel biomaterial exhibiting excellent protein resistance.
The polymer was synthesized through step-growth polymerization
with carbohydrate-derived monomers. The ester linkage in the
polymer renders it biodegradable. We are currently investigating
the influences of various structural permutations on the biocom-
patibility and biodegradability of this family of polymers. Through
the design of monomer structure and copolymerization, polymers
with desired structures and properties will be constructed to meet
various biomedical applications. This introduces a novel biomaterial
that combines excellent protein resistance, biodegradability, and
functionalizability.
Acknowledgment. We thank the Arnold and Mabel Beckman
Foundation and the University of California at Irvine (UCI) for
partial financial support. We thank Prof. Larry Marsh and Ms.
Adeela Syed at the Department of Developmental and Cell Biology
of UCI for their assistance in the SPR study. Z.G. gratefully
acknowledges a Beckman Young Investigator Award, a DuPont
Young Faculty Award, a NSF CAREER Award, and a 3M Non-
Tenured Faculty Award.
Figure 1. SPR data for the adsorption of fibrinogen onto polymer 1 and
control surfaces.
of 3 and 4 in dichloromethane using triethylamine as base gave
the best results, affording polymer 1 with a number-averaged
molecular weight (Mn) of 29 000 g/mol and a weight-averaged
molecular weight Mw of 44 000 g/mol. The monomodal GPC trace
and the relatively narrow polydispersity (Mw/Mn ) 1.5) indicate
that the polymerization follows the standard step-growth mecha-
nism. Polymer 1 is shown without specification of stereochemistry
because there exists a combination of enantiomeric and diastere-
omeric repeating units in the polymer.15
After the successful synthesis of the side-chain polyether 1, its
protein resistant ability was measured by surface plasmon resonance
(SPR) spectroscopy. Following Whitesides and Mrksich’s stud-
ies,11,12 we measured the adsorption of two proteins: fibrinogen, a
large (340 kD) blood plasma protein that adsorbs strongly to
hydrophobic surfaces, and lysozyme, a small protein (14 kD, PI )
12) that is positively charged under the conditions of our experiment
(phosphate buffered saline, PBS, pH 7.4). Fibrinogen is used as a
model for “sticky” serum proteins,16 and lysozyme is used as a
model for electrostatic adsorption of proteins to surfaces.17 Because
of the good water solubility of polymer 1, a terminal thiol-
functionalized polymer 1 was prepared and chemisorbed onto a
gold slide for the SPR studies (Supporting Information). SAMs of
1-decanethiol and a tri(ethylene glycol) functionalized alkylthiol
(TEG-SH) on gold were used for positive and negative control
studies.
The SPR data for adsorption of fibrinogen in Figure 1 show that
polymer 1 has excellent protein resistance. The amount of protein
adsorbed (∆RU ) change in response units) as measured by SPR
was determined by subtracting the value of RU prior to the injection
of protein from the value of RU measured 10 min after the
completion of the protein injection. Like the TEG model SAM,
the polymer 1 surface showed minimum adsorption of fibrinogen.
Within the experimental error, the amount of protein adsorbed onto
the polymer 1 surface is about the same as the amount adsorbed
onto the model PEG SAM, which is about 1% of the amount
adsorbed onto the hydrophobic 1-decanethiol SAM. The lysozyme
adsorption data also showed that polymer 1 has the same protein
resistance as the model TEG SAM (Supporting Information). The
mechanism for protein resistance may operate differently between
the polymer 1 film and TEG SAM. While the interaction of water
with the SAM surface plays a critical role in TEG SAM, for the
polymer 1 film, the entropic penalty associated with displacing the
polymer chains by proteins may play an important role in preventing
protein adsorption.18
Supporting Information Available: Experimental details for the
synthesis, polymerization, characterization, and SPR studies (PDF). This
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1
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In summary, we report a carbohydrate-derived side-chain poly-
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