PEO grafting on biomaterial surfaces using gamma-irradiation
Abstract
Surface grafted poly (ethylene oxide) (PEO) chains are known to minimize protein adsorption and platelet adhesion. We used gamma-irradiation technique to graft PEO on material surfaces. We examined the effect of PEO chain length on the prevention of protein adsorption on hydrophobic surfaces. PEO grafted surfaces were examined by electron spectroscopy for chemical analysis (ESCA), and atomic force microscope (AFM). Also, the surface concentration of PEO chains was determined by using radio-iodinated Pluronic® surfactants molecules. A single chain mean field theory was used to theoretically predict protein adsorption isotherms on PEO grafted surfaces and the results were compared with the experimental observations. PEO grafted surfaces were examined for complement activation. PEO grafted vascular grafts were evaluated in canine ex vivo shunt model. We have shown that PEO grafting on hydrophobic surfaces using gamma-irradiation resulted in significant reduction of protein adsorption and platelet adhesion. The success of PEO grafting was confirmed by ESCA. Reduction of protein adsorption by grafted PEO on hydrophobic surface is found to be independent of PEO chain length at high surface coverage. At low surface coverage, however, longer PEO chains were more effective. PEO grafted surfaces showed a surface PEO concentration dependent activation of the complement system. This is thought to be due to the hydroxyl functional group on PEO chains. When evaluated in ex vivo canine shunt model, PEO grafted surfaces were found not to be very effective in preventing platelet adhesion and thrombosis. The discrepancy between the in vitro and ex vivo results is intriguing. However, there are various explanations for this discrepancy. (1) The use of anticoagulated blood in vitro where as non-anticoagulated blood in ex vivo. (2) The presence of shear that may affect platelet reactivity towards surfaces. (3) Effect of temperature. (4) Effect of number of platelets. Over all, we were able to successfully graft PEO chains on hydrophobic surfaces. Surface coverage is an important variable determining the success of PEO grafting in the prevention of protein adsorption and cellular adhesion.
Degree
Ph.D.
Advisors
Park, Purdue University.
Subject Area
Pharmaceuticals|Pharmacology|Biomedical research
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