Detection of biomarkers at low concentrations is essential for early diagnosis of numerous diseases. In many sensitive assays, the target molecules are tagged using fluorescently labeled probes and captured using magnetic beads. Magnetic beads facilitate washing and separation steps, are well suited for automation, and improve the assay sensitivity. Current devices rely on quantifying the target molecules by detecting the fluorescence signal from individual beads. Thus, to detect low concentrations of target molecules, these devices require sophisticated optical detectors, making them bulky and expensive. Here, we propose a compact fluorescence-based system that simply uses a small permanent magnet with a conic tip to aggregate the magnetic beads, forming a cluster of fluorescently labeled probes whose fluorescence signal is much greater than that of a single bead. Using the magnetically aggregated biosensors to detect human Interleukin-8, we demonstrated a limit of detection of 0.1 ng/l and a 4-log dynamic range performance, which is on par with the most sensitive devices but is achieved without their bulk and cost.
We present the calculations of the Curie temperature and magnetization of
doped EuO both in the absence and in the presence of external magnetic field.
The calculations were performed both for the free electrons model and for the
model with finite electron band width. Both models give similar results for the
magnetization, close to Brillouin function.Comment: PdfLatex, 7 pages, 12 Figures. Accepted for publication in Physica
Status Solidi(b
In many sensitive assays, target molecules are tagged using fluorescently labeled probes and captured using magnetic beads. Here, we introduce an optical modulation biosensing (OMB) system, which aggregates the beads into a small detection area and separates the signal from the background noise by manipulating the laser beam in and out of the cluster of beads. Using the OMB system to detect human interleukin-8, we demonstrated a limit of detection of 0.02 ng/L and a 4-log dynamic range. Using Zika-positive and healthy individuals’ serum samples, we show that the OMB-based Zika IgG serological assay has 96% sensitivity and 100% specificity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.