Fluorescein isothiocyanate-labeled insulin (FITC-insulin) has been widely used for bioanalytical applications. Due to the high cost of commercial FITC-insulin and tedious labeling procedures described in the literature, there is still a need to develop a cost effective, reliable and quick labeling method for insulin. The purpose of the present work was to develop a quick and affordable method for FITC labeling of human insulin and to determine the effect of different conjugations of FITC to human insulin on its permeability through the MDCK cell monolayer. FITC labeling of insulin gives mono-, di- or tri-conjugates depending on the reaction time and the molar ratio of FITC:insulin. Mono-conjugate with unlabeled insulin, mixture of di- and tri-conjugate, and tri-conjugate with very little amount of di-conjugate were synthesized in less than 4 h. Degree of conjugation had an effect on the permeability of insulin through the MDCK cell monolayer. Mono-conjugate had higher permeability than the unlabeled insulin due to increase in partition coefficient. However, tri-conjugate showed lower permeability than the unlabeled insulin due to the increase in molecular weight.

异硫氰酸荧光素标记的胰岛素（FITC-胰岛素）已被广泛用于生物分析应用。由于商业FITC-胰岛素的高成本和文献中描述的繁琐的标记程序，仍然需要开发一种成本有效，可靠和快速的胰岛素标记方法。本工作的目的是开发一种快速且可负担的FITC标记人胰岛素的方法，并确定FITC与人胰岛素的不同缀合对其通过MDCK细胞单层渗透性的影响。胰岛素的FITC标记根据反应时间和FITC：胰岛素的摩尔比产生单，二或三缀合物。在不到4小时的时间内，合成了未标记胰岛素的单结合物，二结合物和三结合物的混合物以及三结合物的量很少。共轭程度对胰岛素通过MDCK细胞单层的通透性有影响。由于分配系数的增加，单结合物比未标记的胰岛素具有更高的渗透性。然而，由于分子量的增加，三结合物显示出比未标记的胰岛素更低的渗透性。