探索宇宙首部曲 — 臺大和清大天文學家參與 DESI 暗能量光譜儀計畫 首次公開近200萬筆天體光譜數據
The SELEX method selects DNA aptamers that bind to the glycated peptide of HbA1c via magnetic beads.
Selected by the SELEX method, the DNA aptamer (AptGP) that binds to the glycated peptide of HbA1c is a 40-base, single-stranded DNA.
Molecular dynamics simulation was used in calculations for the interaction between the glycated peptide of HbA1c and the DNA aptamer (AptGP), and the three-dimensional structure of the complex after docking.
In the process of preparing the PEG:AptGP/SiNW-FET biosensor for detecting HbA1c, a nanowire field-effect transistor device was chemically modified. This biosensor was then connected to a lock-in amplifier to detect the concentration of HbA1c in blood samples.
Diabetes mellitus is a common metabolic disorder that has a major impact on the quality of life for patients. Early detection and effective therapy are critical in treating diabetes. Professor Yit-Tsong Chen from the Department of Chemistry of the National Taiwan University, together with two physicians from the Mackay Memorial Hospital, Dr. Chih-Yang Chen and Dr. Tse-Hao Chen, in collaboration with the theoretical calculation team led by Professor Sheh-Yi Sheu from the National Yang Ming Chiao Tung University, used the SELEX (systematic evolution of ligands by exponential enrichment) method (Figure 1) to screen and identify a novel 40-base, single-stranded DNA aptamer (AptGP, Figure 2), with high binding affinity to glycated hemoglobin A1c (HbA1c) in human blood. AptGP bound to the glycated N-terminus of the hemoglobin β-chain (i.e. Fru-Val-His-Leu-Thr-Pro-Glu-COOH, denoted by GP) to form the GP-AptGP complex. The dissociation constant in phosphate buffered saline (PBS) was Kd = 1.1 ± 0.1 nM. The team led by Professor Sheh-Yi Sheu used molecular dynamics simulation in calculations to further construct the three-dimensional structure of the GP-AptGP complex (Figure 3).
The aptamer was modified onto a silicon nanowire field-effect transistor (SiNW-FET) to make a biosensor, which could detect HbA1c level in blood very sensitively, quickly and accurately. The team designed a SiNW-FET device that was highly sensitive and responsive to external electric field. The SiNW-FET was composed of hundreds of silicon nanowires as semiconducting channels (the diameter of each silicon nanowire was only ~20 nm), which were aligned almost parallel to each other and connected between interdigitated electrodes (Figure 4, the distance between adjacent source-drain electrodes was 3 μm). A selected concentration ratio of the above-mentioned AptGP and polyethylene glycol (PEG) was modified on the SiNW-FET surface (PEG:AptGP/SiNW-FET) via chemical bonds. The HbA1c in human blood samples could be then measured. The results were not only consistent with those obtained by the traditional capillary electrophoresis method, but also showed the advantages of sensitive, rapid, and cost-effective performance for making portable PEG:AptGP/SiNW-FET biosensors amenable to point-of-care diagnostics.
PEG:AptGP/SiNW-FET detects the concentration of HbA1c in blood, without the need for pretreatment such as desalting. Furthermore, PEG:AptGP/SiNW-FET has a very sensitive linear response regime (1 μM to 10 nM) in detecting HbA1c concentration, so blood samples need to be diluted 100 to 10,000 times with PBS. In other words, testing can be done with a very small amount of blood sample. A drop of blood (about 0.01 cc) diluted 10,000 times will be 100 cc in volume, and only 1 cc of it will be needed to measure the HbA1c concentration. Similarly, if different probe molecules are modified on SiNW-FET to detect biomarkers of different diseases, the use of such nanoscale biosensors can truly achieve the goal of detecting numerous diseases with one drop of blood.
The full text of “Detecting glycated hemoglobin in human blood samples using a transistor-based nanoelectronic aptasensor” will be published December 2021 in Nano Today. https://doi.org/10.1016/j.nantod.2021.101294
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