Zhihao Xu,Hezhong Ouyang,Haoda Zhang,Lei Sun,Shasha Li,Ruijiang Liu
A highly sensitive label-free electrochemical aptamer biosensor with magnetically induced self-assembly had been developed to detect gastrin-releasing peptide precursor (ProGRP), which is not only a highly specific tumour marker for small-cell lung cancer (SCLC), but also very stable in serum, and thus had robust clinical utility. Based on the advantages of high specific surface area and facile separation and recycling, magnetic α-Fe 2 O 3 /Fe 3 O 4 nanorods with the average length of 175 nm, the average diameter of 28 nm, and the saturation magnetization of 66.9 emu/g were used as the matrix, and Au nanoparticles (AuNPs) were loaded on the surfaces of the nanorods to enhance the electrochemical signal. The aptamer double-stranded probe with high specificity to the target protein was bound to the surface of α-Fe 2 O 3 /Fe 3 O 4 @Au. The thiol-modified oligonucleotides could quickly and stably bind to AuNPs to form Au-S, which provided a guarantee for the immobilization of the probe and the controllable self-assembled molecular layer. Then, the sensor after capturing the target was self-assembled on the surface of the magnetic glassy carbon electrode (MGCE) by liquid phase incubation for electrochemical detection. The construction and detection performance of the sensor were evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Under the optimized conditions, the sensor had remarkable linearity in the range of 0.1 pg/mL - 100 ng/mL (R 2 = 0.998), the limit of detection (LOD) was 17.51 fg/mL, while the limit of quantitation (LOQ) was 58.39 fg/mL. Additionally, the biosensor had excellent stability, reproducibility and anti-interference ability, as well as satisfactory recovery in spiked serum samples (99.46 %–103.32 %).
Yeru Liu,Sisi Si,Shengyi Dong,Bozhi Ji,Huimin Li,Song Liu
In this work, an ultrasensitive and low-cost electrochemical immunosensor has been constructed for ProGRP detection. The prepared three-dimensional reduced graphene oxide-gold nanoparticles (3D-rGO@Au) composite as substrate materials were applied for electrode modification, which can enhance electrical conductivity and enlarge the effective surface area for immobilizing capture antibody. Detection antibody-coated non-conductive SiO 2 nanospheres were used for specifically recognize ProGRP and form a sandwich structure. The electrochemical response signal of the sandwich-type immunosensor was based on the electron transferability between the electrode and [Fe(CN) 6 ] 3−/4− . 3D-rGO@Au can significantly increase the initial current, while SiO 2 can greatly reduce the response current. The combined effects of these nanomaterials can thus effectively enhance the sensitivity. Under optimal conditions, the constructed immunosensor exhibited a wide linear range (1 fg/mL to 10 ng/mL) with a low limit of detection (0.14 fg/mL). Moreover, the immunosensor exhibited superior stability, good reproducibility, favorable selectivity, and high sensitivity. Meanwhile, the concentration of ProGRP in human serum samples was measured with satisfactory results. This device is promising in the early screening of lung cancer, which can be applied as an over-the-counter test at home or in the community.
Xuwen Gao,Xiaoxuan Ren,Yaojia Ai,Mengwei Li,Bin Zhang,Guizheng Zou
Coreactant-free electrochemiluminescence (ECL) is promising for removing the exogenous effects of coreactant and simplify the operation procedures and setups of commercialized ECL bioassays. Herein, an electrosterically involved strategy for achieving a low-triggering-potential (+0.21 V vs Ag/AgCl) and coreactant-free ECL from dual-stabilizer-capped CdTe nanocrystals (NCs) is proposed with mercaptopropionic acid (MPA) and hexametaphosphate (HMP) as the capping agents of luminophores. Upon employing the CdTe NCs as the ECL tag for the immunoassay, all the tags in the bioconjugates of the CdTe NCs and the secondary antibody (Ab2|CdTe) as well as in the final achieved sandwich-type immunocomplexes can exhibit efficient coreactant-free ECL with an electrosterically involved triggering potential nature. The bioconjugates of Ab2|CdTe with Ab2 no more than 30 kDa, such as the thyroid stimulating hormone (30 kDa) and the recombinant pro-gastrin releasing peptide (ProGRP, 14 kDa), merely exhibit coreactant-free ECL around +0.24 V, while bioconjugates of Ab2|CdTe with an Ab2 beyond 30 kDa only give off coreactant-free ECL around +0.82 V. Due to the further enhanced electrosteric effect in sandwich-type immunocomplexes, only the ECL immunosensor with ProGRP as the target can give off coreactant-free ECL around +0.24 V. The electrosterically involved and coreactant-free ECL of CdTe NCs is consequently utilized to sensitively and selectively determine the molecular protein ProGRP, which demonstrates a wide linearity range from 0.1 to 2000 pg/mL and a low limit of detection at 0.05 pg/mL (S/N = 3). This low-triggering-potential and coreactant-free combined ECL platform indicates that engineering the surface of CdTe NCs with a protein can improve the performance of ECL tags in a protein-weight-involved electrosterical way.
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