Direct Measurement of Interactions between Tethered Poly(ethylene glycol) Chains and Adsorbed Mucin Layers

Abstract

Direct force measurements were used to investigate the interactions between grafted poly(ethylene glycol) (PEG) (Mw 2000) and both adsorbed and soluble bovine submaxillary gland mucin. These measurements show that both soluble and adsorbed mucin adhere weakly to the grafted PEG layers. Soluble mucin mediates a concentration-dependent, bridging attraction between the PEG films. Similarly, PEG adheres to adsorbed mucin layers in both the presence and absence of 0.2 mg/mL mucin solutions. The heteropolymer attraction is pH dependent, with the adhesion being substantially higher at pH 2 than at pH 7.2. The latter suggests that hydrogen-bonding interactions are responsible for binding. The weaker mucin interactions at pH 7.2, however, allow for PEG-coated surfaces to adhere to surface-bound mucin in the presence of soluble mucin. Such characteristics are particularly desirable for coatings for oral drug carriers.