The development of a near infrared inulin optical probe for measuring glomerular filtration rate

The polysaccharide, inulin, is considered the clinical gold standard for measuring glomerular filtration rate (GFR), an assessment of kidney filtering capacity and renal function, and therefore, is a prognostic indicator of chronic kidney disease (CKD). The classic method of measuring GFR is laborious, tedious and invasive. Therefore, estimated GFR (eGFR) has become the favoured measurement, but unfortunately suffers in its accuracy. Here, we describe the development of a near infrared dye-labeled inulin, Cy7.5-inulin conjugate, for use as an optical probe to accurately and non-invasively measure GFR in patients by transcutaneous pulse dye densitometer (TPDD). We have characterized the modifications made to inulin and the dye-polysaccharide conjugate by a number of analytical techniques and demonstrated that it is stable under experimental in vivo conditions. To this end, the probe has been successfully used in a pig model to accurately measure GFR non-invasively.