Novel amphiphilic block copolymers composed of hydrophobic (poly(2-methoxyethyl acrylate): M) and hydrophilic (poly(N,N-dimethylacrylamide): D) segments were synthesized by living radical polymerization: a reversible addition-fragmentation chain-transfer polymerization. Two types of amphiphilic block copolymers, triblock (MDM) and 4-arm block ((MD)4) copolymers with specific compositions (D/M = (750-1500)/250), were prepared by a versatile one-pot synthesis. These copolymers show good adhesion to various types of substrates (e.g., polystyrene, polycarbonate, polypropylene, Ti, and glass), and the surface coating showed high protein repellency and a low contact angle for water, regardless of the substrate. The two opposing characteristics of high protein repellency and good substrate adhesion were achieved by the combined effects of the molecular architecture of the block copolymers, the high molecular weight, and the characteristics of each segment, that is, low protein adsorption capability of both segments and low glass transition temperature of the hydrophobic segment. Further, a polystyrene dish coated with the MDM block copolymer could be sterilized by γ-ray irradiation and used as a good substrate for a suspension cell culture that exhibits low cell adhesion and good cell growth.
Antithrombogenicity is one of the
most critical properties required
for materials used in biomedical devices, particularly in devices
that contact blood. The antithrombogenicity of surfaces coated with
amphiphilic block copolymers composed of hydrophobic poly(2-methoxyethyl
acrylate) (M) and hydrophilic poly(N,N-dimethylacrylamide) (D) segments was investigated using plasma protein
and whole blood with regard to protein adsorption, thrombus formation,
platelet activation, and clotting kinetics. Three types of block copolymers
and a random copolymer were synthesized using one-pot reversible addition–fragmentation
chain-transfer (RAFT) polymerization under conditions of high yield
and high molecular weight. Triblock and 4-arm block copolymers with
MDM and (MD)4 architecture, respectively, showed good adhesion
to both organic and inorganic substrates, including polyvinyl chloride
(PVC) tubes, and the resulting coated surfaces showed superior protein
repellency and hemocompatibility compared to the diblock or random
copolymer coatings and noncoated control. In a Chandler-loop method
with whole blood, PVC tubes coated with MDM and (MD)4 showed
improved thromboresistance and adsorption resistance to blood-derived
proteins. This high hemocompatibility was also confirmed with human
whole blood by thrombelastography (suppression of blood-clotting behavior
in both intrinsic and extrinsic coagulation pathways) and platelet
function analyses (significant reductions in the aggregation activity
of platelets under two types of stimulation). The antithrombogenicity
has been discussed based on the structural analyses of the MDM-coated
surface. The results of this study will enable the development of
more effective biomedical and analytical devices with excellent antithrombogenic
characteristics by using a simple and environmentally friendly approach.
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