Determination of α-Fetoprotein in Human Serum by a Quartz Crystal Microbalance-based Immunosensor

Abstract

Background: Increased α-fetoprotein (AFP) in adult plasma is considered an early indication of hepatocellular carcinoma and teratoblastoma. The aim of this study was to develop a rapid method to measure AFP in human serum by use of a direct immunosensor based on a quartz crystal microbalance (QCM). Methods: A self-assembled monolayer prepared by the cystamine method was applied to immobilize anti-AFP monoclonal antibodies on the gold surface of a quartz crystal. The frequency shifts of the QCM were measured and related to AFP concentrations. The piazoimmunosensor used no labeled reagent and no pretreatment of samples. Results: Ten cycles of measurements could be performed on the gold surface of the same crystal regenerated with a solution of glycine-HCl. A linear relationship existed between the frequency shifts (Hz) and the log values of AFP concentrations from 0.1 to 100 μg/L in buffer and human serum. When used for 15 days, the frequency shifts were all >95% of those on the response at the first day. The regression equation was y = 1.03x − 0.06 (Sy|x = 3.92; r = 0.9987) for this QCM method and RIA in 29 clinical human serum samples. Conclusions: The QCM sensor can measure AFP in buffer and human serum and offers advantages of high specificity, reusability, low detection limit, no label or sample pretreatment, and low sample requirement. The assay format of the immunosensor was more rapid and simpler than conventional methods.

Development of effective QCM biosensors by cyclopropylamine plasma polymerization and antibody immobilization using cross-linking reactions

“…A sharp decrease of the QCMs resonant frequency by 40 Hz achieved during the reaction with 10 μg/ml solution of HSA in case of 1 st film type is typical for the GA method [42]. According to the literature related to conventional SAMs [43,44], stability level of the developed immunosensors was higher. Because of the better response the 1 st type of the plasma polymer film was chosen for further investigations.…”

Rapid Detection of Cadmium-Resistant Plant Growth Promotory Rhizobacteria: A Perspective of ELISA and QCM-Based Immunosensor

“…The cystamine adsorbs to the gold electrode as its disulfide bonds are broken. Cystamine-NH binds to the C=O of the IgG molecule of anti-fluorescent Pseudomonas and not to the -NH of the antigen binding sites in the IgG molecule [3,5,14].…”

“…Quartz crystal microbalance (QCM)-based immunosensors are important analytical tools for monitoring antibodyantigen reactions, allowing rapid and continuous analysis of the binding event without the requirement for added reagents or separation/washing steps [3]. Immobilization of biomolecules on gold surfaces is readily achieved by making use of self-assembled monolayers (SAMs) [1].…”

Quartz crystal microbalance with dissipation (QCM-D) as tool to exploit antigen–antibody interactions in pancreatic ductal adenocarcinomadetection

“…These piezoelectric tools were first thoroughly investigated in 1880 (Curie and Curie, 1880), but were not utilized as immunosensors until 1972 (Shons et al, 1972). In the past decade, QCM based immunosensors have drawn attention because of their ability to detect slight mass changes in biomaterials (Chou et al, 2002;Su and Li, 2004;Wu et al, 2003). Because of their sensitivity and compatibility with liquid-phase media, acoustic wave devices are believed to have the potential to become a useful tool in cancer screening modalities.…”