Microfluidic Flow Injection Analysis with Thermal Lens Microscopic Detection for Determination of NGAL.

A combined microfluidic flow injection analysis-thermal lens microscopy ( $$\upmu $$ FIA-TLM) system was applied for determination of neutrophil gelatinase-associated lipocalin (NGAL)-a biomarker of acute kidney injury. NGAL was determined following a commercial ELISA assay and transfer of the resulting solution into the $$\upmu $$ FIA-TLM system with a 100 $$\upmu $$ m deep microchannel. At an excitation power of 100 mW, the $$\upmu $$ FIA-TLM provided about seven times lower limits of detection (1.5 pg $${\cdot }\mathrm{mL}^{-1})$$ as compared to a conventional ELISA test, and a sample throughput of six samples per minute, which compares favorably with sample throughput of the microtiter plate reader, which reads 96 wells in about 30 min. Comparison of results for NGAL in plasma samples from healthy individuals and for NGAL dynamics in patients undergoing coronary angiography measured with transmission mode spectrometry on a microtiter plate reader and with $$\upmu $$ FIA-TLM showed good agreement. In addition to improved LOD, the high sensitivity of $$\upmu $$ FIA-TLM offers possibilities of a further reduction of the total reaction time of the NGAL ELISA test by sacrificing some of the sensitivity while reducing the duration of individual incubation steps. [ABSTRACT FROM AUTHOR]