Label-Free Detection of C-Reactive Protein Using ZnO Tetrapods Modified Quartz Crystal Microbalance System

A novel horseradish peroxidase- (HPR-) doped magnetic core-shell Fe3O4@SiO2@Au nanocomposites (Fe-Au MNPs) were employed on immunoassay for the determination of C-reactive protein (CRP) based on a electrochemical quartz crystal microbalance detector (EQCM). Firstly, the secondary CRP antibody and HRP were both immobilized on the Fe-Au MNPs (Fe-Au MNPs-anti-CRP2/HRP) as a signal tag. Secondly, the above tag and the primary antibody (anti-CRP1) in the bottom of 96-well microtiter plate were employed to conjugate with a serial of CRP concentrations to produce a sandwich immunocomplex. Thirdly, the immunocomplex solution was subsequently exposed to3,3′-diaminobenzidine (DAB) in the presence of H2O2, resulting in an insoluble product. When the precipitation solution was dripped on EQCM, it can achieve a decrease of frequency of crystal (Δf). The amount ofΔfwas proportional to (CRP) from 0.003 to 200 ng mL−1with a low detection limit of 1 pg mL−1. Compared with the enzyme-linked immunosorbent assay (ELISA), the immunoassay shows greatly improved sensitivity due to the significant amount of HRP labeled on signal tag. It also has good specificity and low sample consumption, which is expected to be a benefit for the CRP screening in early diagnosis of cardiovascular disease.

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Magnetic Imprinted Polymer-Based Quartz Crystal Microbalance Sensor for Sensitive Label-Free Detection of Methylene Blue in Groundwater

Sensors ◽

10.3390/s20195506 ◽

2020 ◽

Vol 20 (19) ◽

pp. 5506

Author(s):

Yufeng Hu ◽

Hanwen Xing ◽

Gang Li ◽

Minghuo Wu

Keyword(s):

Methylene Blue ◽

Quartz Crystal Microbalance ◽

Quartz Crystal ◽

Sodium Dodecyl ◽

Sodium Dodecyl Benzene Sulfonate ◽

Intrinsic Property ◽

Label Free ◽

Target Species ◽

Label Free Detection ◽

Seawater Samples

Tiny changes in the mass of the sensor in a quartz crystal microbalance with dissipation monitoring (QCM-D) can be observed. However, the lack of specificity for target species has hindered the use of QCM-D. Here, molecularly imprinted polymers (MIPs) were used to modify a QCM-D sensor to provide specificity. The MIPs were formed in the presence of sodium dodecyl benzene sulfonate. Imprinted layers on Fe3O4 nanoparticles were formed using pyrrole as the functional monomer and cross-linker and methylene blue (MB) as a template. The MIPs produced were then attached to the surface of a QCM-D sensor. The MIPs-coated QCM-D sensor could recognize MB and gave a linear response in the concentration range 25 to 1.5 × 102 µg/L and a detection limit of 1.4 µg/L. The QCM-D sensor was selective for MB over structural analogs. The MIPs-coated QCM-D sensor was successfully used to detect MB in river water and seawater samples, and the recoveries were good. This is the first time MB has been detected using a QCM-D sensor. Mass is an intrinsic property of matter, so this method could easily be extended to other target species by using different MIPs.

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