Interaction between proteins and polyphosphazene derivatives having a galactose moiety

For tissue engineering applications, it is necessary to balance the need for specific biological interactions with the need to prevent unfavorable nonspecific interactions. For this purpose, novel poly[(organo)phosphazenes] were synthesized having galactose and/or poly(ethylene glycol) (PEG) side chains. The synthesis was described previously. Here, we investigate the human serum albumin (HSA) adhesion to these polymers using surface plasmon resonance (SPR). We could conclude that the incorporation of PEG reduced the protein adsorption. The influence of the galactose moieties was investigated using SPR and a sugar-lectin binding assay. The interaction between a lectin (Peanut agglutinin, PNA or Ricinus communis-agglutinin, RCA) and the polyphosphazene derivatives was evaluated. Type IIA polymers, having aminohexyl-galactose, phenylalanine ethyl ester, and glycine ethyl ester side chains, were capable of binding with the lectin. As the amount of galactose was increased, the extent of the galactose specific lectin binding was also increased (higher RU or absorbance). PEG containing polymers failed to bind specifically with the lectin. The presence of PEG, either as a spacer or as additional chains, interfered with the establishment of contact between the galactose and the binding site on the lectin. The adsorption of PNA or RCA to these types of polymers was attributed to nonspecific interactions. SPR was also used to determine rate and equilibrium constants. In addition the effect of the addition of water soluble polyphosphazenes on the enzymatic cleavage of o-nitrophenyl-beta-D-galactopyranoside was investigated. The galactose moieties were not available as inhibitors because of the presence of PEG.