Lateral flow immunoassay based on gold magnetic nanoparticles for the protein quantitative detection: Prostate-specific antigen.

Point-of-care testing (POCT) demands for rapidly obtaining test results by means of portable analytical instruments and auxiliary reagents at the sampling site. It's important for tumor marker to be recognized and detected in early clinical diagnosis. Many studies focused on producing small portable devices that would allow fast, accurate, and on-site detection. This study aimed to report a magnetic quantitative lateral flow immunoassay (LFIA) system based on poly (acrylic acid) (PAA)-modified gold magnetic nanoparticles (PGMNs) for detecting prostate-specific antigen (PSA) qualitatively and quantitatively. The result was easily achievable with a portable magnetic reader within 15 min. Under optimal conditions, as low as 0.17 ng/mL PSA could be detected. The method was validated using a well-established Solin electrochemiluminescence immunoassay and showed high consistency in detecting 84 serum samples (R2 = 0.98). The quantitative LFIA based on PGMNs established in this study was proven to be rapid, accurate, sensitive, and inexpensive. As a POCT, it can be potentially developed for the quantitative diagnosis of other disease-related protein biomarkers.

Polyelectrolyte-coated gold magnetic nanoparticles for immunoassay development: toward point of care diagnostics for syphilis screening.

Immediate response for disease control relies on simple, inexpensive, and sensitive diagnostic tests, highly sought after for timely and accurate test of various diseases, including infectious diseases. Composite Fe3O4/Au nanoparticles have attracted considerable interest in diagnostic applications due to their unique physical and chemical properties. Here, we developed a simple coating procedure for gold magnetic nanoparticles (GMNs) with poly(acrylic acid) (PAA). PAA-coated GMNs (PGMNs) were stable and monodispersed and characterized by Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy, UV-visible scanning spectrophotometry, thermogravimetric analysis, and Zetasizer methodologies. For diagnostic application, we established a novel lateral flow immunoassay (LFIA) strip test system where recombinant Treponema pallidum antigens (r-Tp) were conjugated with PGMNs to construct a particle probe for detection of anti-Tp antibodies. Intriguingly, the particle probes specifically identified Tp antibodies with a detection limitation as low as 1 national clinical unit/mL (NCU/mL). An ample pool of 1020 sera samples from three independent hospitals were obtained to assess our PGMNs-based LFIA strips, which exhibited substantially high values of sensitivity and specificity for all clinical tests (higher than 97%) and, therefore, proved to be a suitable approach for syphilis screening at a point-of-care test manner.