Evaluation of Insulin Stability in the Presence of Nonionic Surface Active Agents (Polysorbate Groups) by Circular Dichroism and Fluorescence Spectroscopy

摘要

In this study, the possibility interactions of insulin with four non-ionic surfactants of polysorbates group using circular dichroism and fluorescence spectroscopy was investigated. The results showed that insulin structure is changed at pH 3 and 10 partially in comparison with pH 7. It was also was shown that polysorbates may cause a red shift of maximum emission fluorescence at all of the above pH values. Thermodynamic stability of insulin was determined in the presence of polysorbate group surfactants. The a-helix content of insulin exhibits a slight rising and thereby it causes an increasing in its free energy change (?G) and stability. The ?G (H_20) of insulin was about 65.6 kj mol~(-1) in the presence of polysorbate 80 at pH 7. It was shown that polysorbate 80 increased the free energy and the a-helix content of insulin structure more than the others, so they could be considered as stabilizer in the formulations of protein drugs.