Self-regulating insulin delivery systems: I. Synthesis and characterization of glycosylated insulin

A design for a self-regulating insulin delivery system based on the competitive binding of glucose and glycosylated insulin to the lectin Concanavalin A is proposed. A differnt approach to diabetes therapy is the attempt to effect a permanent cure of the disease by supplementing the patient's defective pancreas with a normally functioning transplant. However, pancreatic transplantation in humans is still in its early stage, and the major problems including rejection of the transplants still remain unsolved. In phas one, eight glycosylated insulin derivatives were synthesized. Maltose was directly coupled to bovine insulin by reductive amination. Succinyl- and giutaryl-glucosamine derivatized insulins were synthesized by a mixed anhydride method using the appropriate substituted glucosamines. Monosaccharide derivatives p-aminophenyl-α-D-glucopyranoside and p-aminophenyl-α-D-mannopyranoside were also coupled to insulin via succinate and glutarate spacers p-D-(α-D-glucopyranosyloxy)-phenyl-thiocarbawoyl insulin was obtained by reacting insulin with p-isothiocyanatophenyl-α-D-glucopyranoside, which was obtained through conversion of p-aminophenyl-α-D-glucopyranoside with thiophosgene. Unreacted maltose and other carbohydrate derivatives were removed by gel permeation chromatography or dialysis unmodified insulin was removed by affinity chromatography. The yield and purity of the carbohydrate derivatives were determined by IR, NMR and MS/GC.