GEL-PERMEATION CHROMATOGRAPHY USED TO DETERMINE THE STABILITY OF FITC-DEXTRANS IN HUMAN SALIVA AND PORCINE SMALL INTESTINAL MUCUS

Fluorescein isothiocyante dextrans (FITC-Dextrans) have been used extensively as high molecular weight markers. The stability of FITC-Dextrans has been demonstrated in many situations, but there are instances where dextrans have not been stable. A gel permeation chromatography (GPC) method has been established that can be used to monitor molecular weight, concentration, polydispersity and free label in FITC-Dextrans. This has been applied to stability studies of FITC-Dextrans in human saliva, porcine small intestinal mucus and with human alpha-amylase. The molecular weight of FITC-Dextran was reduced in human saliva with a half-life of 5 h. The reduction in molecular weight was less rapid in porcine small intestinal mucus and non-existent with human alpha-amylase; sodium azide helped reduce degradation but did not eliminate it. The degradation of FITC-Dextrans is thought to be mediated by dextranase-producing micro-organisms. The successful use of FITC-Dextrans as high molecular weight markers must be accompanied by careful quality control of FITC-Dextrans, particularly when incubation times are long and microbiological spoilage is a possibility.