Two kinds of polyphosphazenes

that bear α-D-glucosyl side groups together with methoxyethoxy or ethyl glycinato as cosubstituent groups

have been synthesized and characterized by IR and 1H-NMR analyses.They were examined in order to investigate their possible use as matrix for glucose-sensitive insulin delivery basing on the specific interaction of glucose with lection.Briefly

the polymers were prepared via nucleophilic displacement of the reactive chlorines of polydichlorophosphazene with diisopropylidene D-glucose at first

and subsequently with methoxyethanol (polymer a) or glycine ethyl ester (polymer b) to substitute the residual P-Cl. After filtration and dialysis

the purified polymers were then treated with 90% trifluoroacetic acid to remove isopropylidene groups to get glucosyl groups. The formation of aggregates of glucosyl_substituted polyphosphazenes physically crosslinked by Concanavalin A (Con A) was studied by monitoring the transmittance at 360 nm of dilute polymeric aqueous solutions. Hydrogels were made by mixing concentrated glucosyl-substituted polyphosphazene aqueous solution with Con A aqueous solution.Different polyphosphazenes with various compositions of α-D-glucosyl side group and methoxyethoxy or ethyl glycinato side group combinations were obtained by adjusting the feeding dose of the nucleophiles. And their hydrophilicity differed from each other for the methoxyethoxy group is hydrophilic

and the ethyl glycinato group is hydrophobic

which would affect the formation of hydrogel and the drug release thereof in different way. In the deprotection reaction

the treating time needed to be prolonged to complete the hydrolysis of isopropylidene groups

however

it would cause significant cleavage of polyphosphazene backbones and degradation of cosubstituted ethyl glycinato groups (while almost no effect to methoxyethoxy) in the strong acidic condition. As a result

the deprotection ratio of glucoses was maintained at about 60% in this study to avoid remarkable decrease in molecular weight

and at the same time

the remained diisopropylidene D_glucosyl groups were considered biocompatible and might play a role in balancing polymeric hydrophilicity/hydrophobicity. Con A is one of the most widely used lectins in studying the interaction of specific saccharide with protein

particularly

for nonreducing D-mannosyl and D_glucosyl residues. For both polymers a and b

their dilute solutions rapidly turned turbid when Con A was mixed into

and turbidity increased with increasing the concentration of polymeric solutions and the content of glucosyl side groups in the polymers due to the formation of more and larger aggregates. The aggregates could be dissociated by addition of free glucose

and transmittance of the solution increased. On the other hand

it has been found that the transmittance data of solutions of polymer a mixed with Con A were much larger that those of polymer b

even if they had the similar amount of glucosyl side groups and the same polymeric concentration. One possible reason for this phenomenon was that polymer b could not dissolve well in water due to the presence of hydrophobic ethyl glycinato side groups

and the interaction between Con A and glucosyl groups was hindered. Thus

hydrogels were made from polymer a and Con A by increasing the polymeric concentration above 10 wt%.Higher concentrations of glucosyl-substituted polyphosphazene

more hydrophilic co-substituted side groups and higher amounts of glucosyl side groups would be in favor of hydrogel formation. This hydrogel can be a potential matrix for glusoce_sensitive insulin delivery.