Advances in Nanomaterial-Based Biosensors for Determination of Glycated Hemoglobin

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

BACKGROUND

The determination of glycosylated hemoglobin (HbA1c) 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 HbA1c 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 HbA1c 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 × 70 mm × 10 mm), and can withstand 1600 psi of liquid pressure. 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 HbA1c. The separation conditions of HbA1c in blood calibrator samples were optimized using the microchip LC system. Samples containing four levels of HbA1c 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 (R2 = 0.993), indicating excellent separation efficiency and reproducibility.

SIGNIFICANCE

The POCT of HbA1c is critical for diabetes diagnosis. The microchip chromatography system was developed for HbA1c 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 HbA1c. It is considered one important step for realizing efficient portable systems for timely and accurate diabetes diagnosis.

Nanomaterials for Fluorescent Detection of Hemoglobin

Hemoglobin plays a vital role in a series of biological activities. Abnormal levels of hemoglobin in blood are associated with many clinical diseases. Therefore, development of simple and accurate methods for sensing hemoglobin is of considerable significance. The blowout advancement in nanotechnology has urged the use of different types of fluorescent nanomaterials for hemoglobin assay. The past decades have witnessed the rapid progress of fluorescent nanosensors for hemoglobin assay. In the review, the sensing principles of fluorescent nanomaterials for sensing hemoglobin were briefly discussed. The advances of fluorescent nanosensors for detection of hemoglobin were further highlighted. And the sensing performance of fluorescent nanosensors versus traditional detection approaches was compared. Finally, the challenges and future directions of fluorescent nanomaterials for detection of hemoglobin are discussed. The review will arouse much more attention to the construction of hemoglobin sensors and facilitate rapid development of fluorescent nanosensors of hemoglobin.

WaveFlex biosensor based on S-tapered and waist-expanded technique for detection of glycosylated hemoglobin

Glycosylated hemoglobin (HbA1c) is considered a new standard for the detection of diabetes mellitus because it is more accurate than regular blood sugar tests and there is no need to take blood on an empty stomach or at a specific time. In this work, we have developed a novel optical fiber biosensor, referred to as the "WaveFlex biosensor," which operates on the principles of localized surface plasmon resonance (LSPR) plasmonic wave. The sensor is fabricated using an innovative S-tapered and waist-expanded technique, enabling it to effectively detect HbA1c. Compared to the HbA1c sensors currently in use, HbA1c optical fiber sensors possess the characteristics of high sensitivity, low cost, and strong anti-interference ability. The gold nanoparticles (AuNPs), cerium oxide (CeO2) nanorods (NRs), and tungsten disulfide (WS2) nanosheets (NSs) are functionalized to improve the effectiveness of the fiber sensor on the probe surface. AuNPs are utilized to generate LSPR by the excitation of evanescent waves to amplify the sensing signal. The CeO2-NRs can have a strong metal-carrier interaction with AuNPs, enhancing the cascade of CeO2-NRs and AuNPs. The WS2-NSs with layered fold structure have a large specific surface area. Therefore, the combination of CeO2-NRs and WS2-NSs is conducive to the binding of antibodies and the addition of sites. The functionalized antibodies on the fiber make the sensor probe capable of specific selection. The developed probe is applied to test the HbA1c solution over concentrations of 0-1000 µg/mL, and the sensitivity and limits of detection of 1.195×10-5 a.u./(µg/mL) and 1.66 µg/mL are obtained, respectively. The sensor probe is also evaluated using assays for reproducibility, reusability, selectivity, and pH. According to the findings, a novel method for detecting blood glucose based on a plasmonic biosensor is proposed.