Abstract
Objective: The purpose of this study was to ascertain the applicability of degradable materials for fabrication of an insulin release system.Methods: Insulin implants were prepared by using poly (vinyl alcohol) (PVA), gellan and chitosan by solution casting method. The prepared implants were evaluated for swellability, content uniformity, potency and purity of insulin in implants, scanning electron microscopy studies, in vitro release studies, in vitro degradation studies using lysozyme, stability studies and circular dichroism spectroscopy.Results: The swelling degree of the implants was found to be in the range of 1.07-1.56. The diffusion coefficient of water through the implant was found to depend on the calcium chloride (CaCl2) concentration. The diffusion coefficient of insulin through the chitosan-PVA-gellan in the early stages was found to be in the range of 1.99´10-5 cm2/sec to 5.24´10-5 cm2/sec and at later stages in the range of 6.9´10-6 cm2/sec to 1.10´10-5 cm2/sec. The weight of the implants was 48±0.58 mg. The insulin content in the implants was 9.86±0.10 mg. The potency of insulin extracted from the implants was 27.11±0.75 U/mg or 95.12±2.61 % of the control insulin. The in vitro release studies showed that insulin was released completely in a period of 13-19 d depending on the composition of the implant. The increase in CaCl2 retarded the rate of insulin release whereas the increase in PVA content leads to the rapid release of insulin. The device was found to undergo significant weight loss due to enzyme mediated degradation.Conclusion: These studies provide validity for the potential utility of chitosan-PVA-gellan implant systems for the delivery of insulin. The studies also demonstrate that insulin maintained its integrity within the implant system. Implants showed the complete release of insulin in 19 d and the release of insulin from the implants depended on the amount of CaCl2.
Highlights
Diabetes mellitus refers to a group of metabolic diseases characterised by chronic hyperglycemia, due to defects in insulin secretion
Chitosan forms a polyionic complex with gellan and this property was used in the current work to prepare an insulin implant of chitosan-Polyvinyl alcohol (PVA)-gellan for maintenance of prolonged therapeutic levels of insulin
Three mechanisms could be responsible for the release of drugs from the hydrogels: swelling, diffusion and degradation
Summary
Diabetes mellitus refers to a group of metabolic diseases characterised by chronic hyperglycemia, due to defects in insulin secretion. The treatment of diabetes by insulin injection provides only a poor approximation of normal glucose homoeostasis, especially for insulindependent diabetes where blood glucose concentrations vary widely despite insulin therapy [1, 2] This is because the pharmacokinetics of insulin following subcutaneous injection does not match the profiles of physiological insulin secretion [3, 4]. Subcutaneous injections result in localized insulin deposits that lead to local hypertrophy and fat deposits under the skin Together these disadvantages lead to suboptimal pharmacodynamics properties of the applied insulin, which does not allow mimicking the complex physiological insulin secretion pattern [5]. Its ingestion has never produced reported adverse dietary, physiological or toxic effects in animals and humans These properties make this polysaccharide suitable for several commercial applications, such as in the food industry and in drug delivery [8]. Chitosan forms a polyionic complex with gellan and this property was used in the current work to prepare an insulin implant of chitosan-PVA-gellan for maintenance of prolonged therapeutic levels of insulin
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