Surface modification of biomaterials with water-soluble polymers: A steric repulsion approach
Abstract
Blood compatibility of biomaterials can be improved by surface modification with water-soluble polymers such as albumin and poly(ethylene oxide) (PEO). On dimethyldichlorosilane-treated glass (DDS-glass), albumin was effective in preventing platelet activation when adsorbed tightly to the surface, remained flexible, and covered the surface completely. This suggests that the adsorbed albumin prevents platelet adhesion and activation by the steric repulsion mechanism. PEO-rich surfaces were prepared by physical adsorption and covalent grafting of PEO/poly(propylene oxide) (PPO)/PEO triblock copolymers (Pluronics$\sp\circler$). Physically adsorbed Pluronics were effective in preventing protein adsorption and platelet adhesion when tightly bound to the surface with 56 or more propylene oxide (PO) residues. When adsorbed tightly to the surface, 19 ethylene oxide (EO) residues in Pluronics were as effective as 129 EO residues. Tight surface binding of Pluronic F-68 (76/30/76) to DDS-glass was achieved by covalent to the surface through $\gamma$-irradiation. When grafted in bulk solution, a crosslinked Pluronic hydrogel formed after 2.3 Mrads of irradiation. Platelet adhesion and activation was minimum on the Pluronic F-68-grafted DDS-glass. $\sp{125}$I-labeled Pluronic F-68 and F-108 were adsorbed on DDS-glass as a function of bulk Pluronic concentration. When adsorbed at room temperature, the surface Pluronic F-68 concentration increased to a maximum of 0.30 $\mu$g/cm$\sp2$ and then decreased. The surface Pluronic F-108 concentration, however, increased up to a plateau of about 4.0 $\mu$g/cm$\sp2$. Peak III/I and excimer/monomer ratios of pyrene suggested that Pluronics self-associated at higher bulk concentration. Pluronic F-68 aggregates had poor affinity for DDS-glass. At 37$\sp\circ$C and 50$\sp\circ$C, however, Pluronic F-68 adsorption increased to 0.5 $\mu$g/cm$\sp2$. It is thought that Pluronic aggregates were able to adsorb onto DDS-glass due to increased hydrophobic interactions at higher temperatures. In addition to improving blood compatibility, surface modification can also be used in other applications such as prevention of protein adsorption in purification, packaging, and administration of protein drugs.
Degree
Ph.D.
Advisors
Park, Purdue University.
Subject Area
Pharmaceuticals|Polymers|Biomedical research
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