Determination of free bilirubin and its binding capacity by HSA using a microfluidic chip-capillary electrophoresis device with a multi-segment circular-ferrofluid-driven micromixing injection

A PMMA microfluidic chip-CE device with a multi-segment circular-ferrofluid-driven micromixing injector has been developed for the determination of free bilirubin and its binding capacity by HSA at equilibrium. The design of the device and its fabrication by a low cost CO2 laser are discussed for intended applications. Under optimized conditions, the total binding capacity of HSA for bilirubin was determined as 16.3+/-1.4 mg/100 mL human serum (n = 3) and residual binding capacity for bilirubin 9.8 mg/100 mL (n = 3) in normal infants. To assess risk of hyperbilirubinemia, free bilirubin and residual binding capacity by HSA provide a better indicator than total bilirubin, as neonates with impaired bilirubin binding capacity could be detected. In addition, residual binding capacity provides an advanced indicator to predict the onset of hyperbilirubinemia before the appearance of free bilirubin. HSA down to 94 nL is used in each titration and a full assay of four titrations takes up 376 nL HSA, sufficient for newborns with HSA in microliter range. The device has shown capable to provide adequate margin of protection to detect an early rising level of bilirubin and impaired binding capacity prior to the onset of jaundice condition.