Microchip capillary electrophoresis for frontal analysis of free bilirubin and study of its interaction with human serum albumin

Abstract

To meet the need for bedside monitoring of free bilirubin for neonates under critical conditions, a microfluidic chip was fabricated and tested for its coupling with CE/frontal analysis (FA) to determine free bilirubin and study of its binding interaction with HSA, which regulated its concentration in plasma. The poly(methyl methacrylate) (PMMA) multichannel chip was fabricated by CO2 laser ablation and bonded with a fused-silica separation capillary for CE/FA separation with UV detection. The chip was designed to allow a complete assay of four electrophoretic runs using preconditioned channels to speed up the determination of free bilirubin and to deliver quick results for bedside monitoring. Under optimized conditions, the linear working range for free bilirubin was from 10 to 200 μmol with RSDs from 2.1 to 5.0% for n = 3, and the LOD at 9 μmol for S/N = 3. From a binding study between bilirubin and HSA under FA condition, the second binding constant for bilirubin-HSA was determined as 1.07 × 105 L/mol and the number of binding sites per HSA as 3.46. The results enabled the calculation of free bilirubin for jaundiced infants based on the clinically significant level of total bilirubin, producing a range of 118.3-119.4 μmol/L. The developed method is shown to meet the clinical requirement with additional margin of protection to detect the early rising level of free bilirubin prior to jaundice condition. The low-cost microchip CE/FA device is shown to produce quick results with high potential to deliver a suitable bed-side monitoring method for bilirubin management in neonates. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.