tailieunhanh - Encyclopedia of Smart Materials (Vols 1 and 2) - M. Schwartz (2002) WW Part 6

Tham khảo tài liệu 'encyclopedia of smart materials (vols 1 and 2) - m. schwartz (2002) ww part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | It was found 102 that glycosylated insulins are more stable to aggregation than commercial insulin and are also biologically active. The functionality of the intraperitoneally implanted device was tested in pancreatectomized dogs by an intravenous glucose tolerance test IVGTT . The effect of an administered 500 mg kg dextrose bolus on blood glucose level was compared with normal and pancre-atectomized dogs without an implant. The results of this study indicated that the diabetic dogs that had the implant had normal glucose levels 107 . In addition the blood glucose profile for a period of 2 days demonstrated that a diabetic dog implanted with the self-regulating insulin delivery system could maintain acceptable glucose levels 50 180 mg dL for the majority of the experiment 40 hours 104-106 . Makino et al. 101 proposed a modification based on hydrophilic nylon microcapsules that contained Con A and succinil-amidophenyl-glucopyranoside insulin. The thin wall of these microcapsules and large surface area resulted in rapid diffusion of glucose and glycosalated insulin and therefore a much shorter lag time. To limit the leakage of Con A which is toxic and allow preparation of porous microspheres Pai et al. 109 cross-linked the Con A by first blocking the sugar binding sites and then reacted it with glutaraldehyde. The porous microspheres demonstrated rapid exchange between succinil-amidophenyl-glucopyranoside insulin and glucose and had a short response time. Kokufata et al. 110 reported a gel system that swells and shrinks in response to specific saccharides. The gel consists of a covalently cross-linked polymer network of A-isopropylacrylamide in which the lectin Con A is immobilized. Con A displays selective binding affinities for certain saccharides. For example when the saccharide dextran sulphate is added to the gel it swells to a volume up to fivefold the original volume. Replacing dextran sulphate with nonionic saccharide a-methyl-D-mannopyranoside brings about