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A prototype medical device for monitoring kidney function by transdermal measurement of the clearance rate of the exogenous fluorescent tracer agent MB-102 (administered intravenously) was developed. Verification of the device with an in vitro protocol is described. The expected renal clearance of the agent was mimicked by preparing a dilution series of MB-102 in the presence of a scattering agent. The slope of a linear fit to the logarithm of fluorescence intensity as a function of dilution step agreed with predictions within 5%, a level of accuracy that would be adequate in assessment of GFR to prevent misdiagnosis of kidney disease. Transdermal measurement was validated using a rat model. A two-compartment pharmacokinetic dependence was observed, with equilibration of the fluorescent agent between the vascular space into which it was injected and the extracellular space into which it subsequently diffused. The best observed signal-to-noise ratios were about 150, allowing determination of the renal clearance time with 5% precision using a 10-min fitting window. Based on the verification and validation methods for transdermal fluorescence detection described herein, the instrument has been approved by the FDA for a first-in-human clinical study, and a first transdermal clearance curve in a human is presented herein.
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