Rapid detection of glycosylated hemoglobin levels by a microchip liquid chromatography system in gradient elution mode

Background: The determination of glycosylated hemoglobin (HbA(1c)) is crucial for diabetes diagnosis and can provide more substantial results than the simple measurement of glycemia. While there is a lack of simple methods for the determination of HbA(1c) using a point-of-care test (POCT) compared to glycemia measurement. In particular, high-performance liquid chromatography (HPLC) is considered the current gold standard for determining HbA(1c) levels. However, commercial HPLC systems usually have some sort of disadvantages such as bulky size, high-cost and need for qualified operators. Therefore, there is an urgent demand to develop a portable, and fast HbA1c detection system consuming fewer reagents. Results: We present a novel microchip that integrates a micromixer, passive injector, packed column and detection cell. The integrated microchip, in which all the microstructures were formed in the CNC machining center through micro-milling, is small in size (30 mm x 70 mm x 10 mm), and can withstand 1600 psi of liquidpressure. The integrated design is beneficial to reduce the band broadening caused by dead volume. Based on the microchip, a microchip liquid chromatography (LC) system was built and applied to the analysis of HbA(1c). The separation conditions of HbA(1c) in blood calibrator samples were optimized using the microchip LC system. Samples containing four levels of HbA(1c) were completely separated within 2 min in optimal gradient conditions, with an inaccuracy (<3.2 %), a coefficient of variation (c.v. < 2.1 %) and a correlation coefficient (R-2 = 0.993), indicating excellent separation efficiency and reproducibility. Significance: The POCT of HbA(1c) is critical for diabetes diagnosis. The microchip chromatography system was developed for HbA(1c) determination, which contains an integrated microchip and works under a gradient elution. It surpasses existing chip technology in terms of separation performance and detection speed, providing a competitive advantage for POCT of HbA(1c). It is considered one important step for realizing efficient portable systems for timely and accurate diabetes diagnosis.