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Background: The initial diagnosis of ectopic pregnancy depends on physical examination, ultrasound, and serial measurements of total β-subunit of human chorionic gonadotropin (hCGβ) concentrations in serum. The aim of this study was to explore the possibility of using quantitative analysis of total hCGβ in urine rather than in serum by immunomagnetic reduction (IMR) assay as an alternative method to diagnose an ectopic pregnancy., Methods: We established a standard calibration curve of IMR intensity against total hCGβ concentration based on standard hCGβ samples, and used an IMR assay to detect total hCGβ concentrations in the urine of pregnant women with lower abdominal pain and/or vaginal bleeding. The final diagnosis of ectopic pregnancy was based on ultrasound scans, operative findings, and pathology reports. In this prospective study, ten clinical samples were used to analyze the relationship of total hCGβ IMR signals between urine and serum. Furthermore, 20 clinical samples were used to analyze the relationship between urine IMR signals and serum levels of total hCGβ., Results: The calibration curve extended from 0.01 ng/mL to 10,000 ng/mL with an excellent correlation (R(2)=0.999). In addition, an excellent correlation of total hCGβ IMR signals between urine and serum was noted (R(2)=0.994). Furthermore, a high correlation between urine IMR signals and serum levels of total hCGβ was noted (R(2)=0.862)., Conclusion: An IMR assay can quantitatively analyze total hCGβ concentrations in urine, and is a potential candidate for point-of-care testing to assist in the diagnosis of ectopic pregnancy.

Some previous reports have already shown the characterizations of immunomagnetic reduction (IMR). The assay technology involves the utilities of biofunctionalized magnetic nanoparticles to label target biomolecules. However, the detection threshold and interference tests for IMR have not been investigated in detail. In this study, alpha-fetoprotein (AFP) was used as a target biomolecule. The signals for AFP solutions of various concentrations, or with interfering materials, were detected via IMR. These samples were also used for characterizing the detection threshold and interference with enzyme-linked immunosorbent assay (ELISA). The results of assaying AFP level with IMR and ELISA were compared. The detection threshold for assaying AFP with IMR was found to be 3 ng/mL, which is 15 times lower than that of ELISA, and definitely suppresses false negative. For the interfering materials noted commonly in serum such as hemoglobin, bilirubin, triglyceride, and vascular endothelial growth factor, there was no detectable interfering effect when assaying AFP with IMR. Several serum samples from normal people and liver-tumor-bearing patients were used for the detections of AFP concentration via IMR. These results reveal the feasibilities of assaying AFP in blood using IMR, as well as achieving high-sensitive and high-specific assay for AFP.

Background: Magnetic nanoparticles biofunctionalized with antibodies are able to recognize and bind to the corresponding antigens. In this work, anti-C-reactive protein (CRP) antibody was covalently conjugated onto the surface of magnetic nanoparticles to label CRP specifically in serum., Methods: The level of serum CRP was detected by immunomagnetic reduction (IMR) assay, which identifies the changes in the magnetic signal representing the level of interaction between antibody-conjugated magnetic nanoparticles and CRP proteins. To investigate the feasibility of IMR for clinical application, pure CRP solutions and 40 human serum samples were tested for IMR detection of CRP to characterize sensitivity, specificity, and interference., Results: In comparison with the immunoturbidimetry assay, the results of the IMR assay indicated higher sensitivity and had a high correlation with those of the current immunoturbidimetry assay., Conclusion: We have developed a novel and promising way to assay CRP in human serum using immunomagnetic reduction in clinical diagnosis.

Magnetic nanoparticles biofunctionalized with antibodies against β-amyloid-40 (Aβ-40) and Aβ-42, which are promising biomarkers related to Alzheimer's disease (AD), were synthesized. We characterized the size distribution, saturated magnetizations, and stability of the magnetic nanoparticles conjugated with anti-Aβ antibody. In combination with immunomagnetic reduction technology, it is demonstrated such biofunctionalized magnetic nanoparticles are able to label Aβs specifically. The ultralow-detection limits of assaying Aβs in vitro using the magnetic nanoparticles via immunomagnetic reduction are determined to a concentration of ∼10 ppt (10 pg/mL). Further, immunomagnetic reduction signals of Aβ-40 and Aβ-42 in human plasma from normal samples and AD patients were analyzed, and the results showed a significant difference between these two groups. These results show the feasibility of using magnetic nanoparticles with Aβs as reagents for assaying low-concentration Aβs through immunomagnetic reduction, and also provide a promising new method for early diagnosis of Alzheimer's disease from human blood plasma.