A quartz-crystal microbalance study of adsorption behaviors of artificial glycoconjugate polymers onto chemically modified gold surfaces and their interactions with lectins

Adsorption behaviors of two different types of lactose-carrying polystyrenes, poly(p-vinylbenzamido-beta-lactose) (PNLA, 1) and poly(N-p-vinylbenzyllactonamide) (PVLA, 2), onto cast films of polystyrene and self-assembled monolayers (SAMs) of 1-octadecanethiol and cystamine were investigated by applying a quartz-crystal microbalance (QCM). The amphiphilic artificial glycoconjugate polymers were strongly adsorbed on the hydrophobic surfaces, i.e. a polystyrene cast film and a SAM of 1-octadecanethiol, from their aqueous solution according to the Langmuir adsorption isotherm (the apparent association constant: K(a)approximate to 10(7) M-1). On the other hand, they were adsorbed little on a hydrophilic SAM of cystamine. The saturated adsorption amounts of the polymers on the hydrophobic surfaces were 2-5 times larger than that calculated on the basis of an assumption of closed-packing monolayer adsorption, which suggests that the adsorbed polymers may take a loop-train-tail conformation. A SAM of 1-octadecanethiol adsorbed two times more of each polymer than a polystyrene cast film did. beta-Galactoside-specific RCA(120) and PNA lectins bound to the surfaces coated with the galactose-bearing polymers according to the Langmuir adsorption isotherm (K(a)approximate to 10(6) M-1). The binding was stronger than that observed by the inhibition of hemagglutinating activity (about 10(4) M-1).