Poly(N-isopropylacrylamide) oligomer was immobilized onto a silica gel surface. The gel adsorbed a hydrophobic protein y-globulin (IgG) at 37"C, however, did not adsorb IgG at 24°C. The adsorbed lgG at 37°C was desorbed by lowering the temperature. No adsorption of a hydrophilic protein bovine serum albumin (BSA) onto this matrix was observed at 37°C nor 24°C.~

We have successfully developed a novel method to stably immobilize bioactive substances that have anionic groups, such as heparin and succinylated collagen (SC), on hydrophobic surfaces through ionic complexation using a polymerizable cationic lipid, diallyl(dioleyl)ammonium bromide (DADOA). It is composed of a hydrophobic part consisting of long hydrocarbon chains and a hydrophilic head with double bonds which render it polymerizable. Analysis of the modification with DADOA and heparin suggested that the modification formed a thin layer, roughly 60 nm in thickness, as a result of the spontaneous deposition of DADOA and heparin dissolved in water, through the hydrophobic interaction between DADOA and the surface and the ionic complexation between DADOA and heparin. The heparin deposition and its rate of release in plasma were 1.5 microg/cm2 and 0.0017 U/cm2/min, respectively. Cytotoxicity test results showed that the polymerization of the deposited DADOA rendered the modified surface stable and noncytotoxic. Further, antithrombogenicity and cell attachability test results demonstrated that heparin and SC were effectively immobilized on hydrophobic surfaces through ionic complexation. This method has proved useful for the modification of the hydrophobic surfaces of medical devices because the modification process can be performed under aqueous conditions without the use of organic solvents which induce crazing/cracking of plastic casings.

Poly(N-isopropylacrylamide) with pendent p-cyclodextrin (PNI-PAAm-CD) was prepared by copolymerization of acyloyl-p-CD and NlPAAm. During the temperature-induced phase separation of an aqueous solution of PNlPAAm-CD, Toluidine Blue dye in the solution was separated into the precipitate of PNlPAAm-CD by way of inclusion complex formation.