Glucose-binding property of pegylated concanavalin A.

Abstract

Concanavalin A (Con A) has been used in the development of sol-gel phase-reversible hydrogels for modulated insulin delivery. The usefulness of Con A has suffered from its poor aqueous solubility and stability. The goal of this study was to modify Con A with poly(ethylene glycol) (PEG) and examine the water solubility and stability of the PEGylated Con A. Con A was PEGylated using monomethoxy poly(ethylene glycol) p-nitrophenol carbonates, and the extent of PEGylation was determined by the fluorescamine method. The stability of the PEGylated Con A was examined by measuring the time-dependent absorbance at 630 nm. The binding affinities of glucose and allyl glucose to native- and PEGylated-Con A were measured by the equilibrium dialysis method. The total number of PEG molecules that can be grafted to Con A was 10. As the number of grafted PEG chains per each Con A was increased up to 5, the binding affinity of glucose was gradually increased and reached the maximum. The solubility and stability of PEGylated Con A were improved significantly over those of native Con A. The binding affinity of allyl glucose to Con A was not changed much by PEGylation. When the extent of PEGylation was excessive (i.e., the number of grafted PEG chains per each Con A was larger than 5), however, the binding affinities of both glucose and allyl glucose were decreased significantly. PEGylation of Con A resulted in improved aqueous solubility and stability of Con A. The binding affinity of glucose increased and reached the maximum when the extent of PEGylation was 50%. Advantages of PEGylated Con A over native Con A are improved aqueous solubility, enhanced long-term stability, and higher glucose sensitivity.