Abstract
The rapid, sensitive and low-cost detection of macromolecular biomarkers is critical in clinical diagnostics, environmental monitoring, research, etc. Conventional assay methods usually require bulky, expensive and designated instruments and relative long assay time. For hospitals and laboratories that lack immediate access to analytical instruments, fast and low-cost assay methods for the detection of macromolecular biomarkers are urgently needed. In this work, we developed a versatile microparticle (MP)-based immunoaggregation method for the detection and quantification of macromolecular biomarkers. Antibodies (Abs) were firstly conjugated to MP through streptavidin-biotin interaction; the addition of macromolecular biomarkers caused the aggregation of Ab-MPs, which were subsequently detected by an optical microscope or optical particle sizer. The invisible nanometer-scale macromolecular biomarkers caused detectable change of micrometer-scale particle size distributions. Goat anti-rabbit immunoglobulin and human ferritin were used as model biomarkers to demonstrate MP-based immunoaggregation assay in PBS and 10% FBS to mimic real biomarker assay in the complex medium. It was found that both the number ratio and the volume ratio of Ab-MP aggregates caused by biomarker to all particles were directly correlated to the biomarker concentration. In addition, we found that the detection range could be tuned by adjusting the Ab-MP concentration. We envision that this novel MP-based immunoaggregation assay can be combined with multiple detection methods to detect and quantify macromolecular biomarkers at the nanogram per milliliter level.
Highlights
The quantitative detection of biomarker(s) is very important in clinical diagnostics [1, 2] environmental monitoring [3, 4] and a variety of other biological research [5]
Goat anti-human ferritin polyclonal antibody and human ferritin were purchased from United States Biological (Salem, MA, USA)
Different concentrations of goat IgG, which was used as model biomarker, were prepared with a range from 0.1 ng/mL to 320 ng/mL. 333.4 μL of Ab-MP solution was mixed with 166.7 μL of goat IgG solutions at different concentrations for 30 min on a thermal mixer at 650 rpm at room temperature
Summary
The quantitative detection of biomarker(s) is very important in clinical diagnostics [1, 2] environmental monitoring [3, 4] and a variety of other biological research [5]. Immunoassay is a prevalent method due to its high specificity Conventional immunoassays, such as enzyme-linked immunosorbent assay (ELISA) [8], surface plasmon resonance (SPR) [9, 10], and quartz crystal microbalance (QCM) [11] require relative long assay times, and typically employ bulky and complicated detection instruments. These methods require either enzyme or fluorescence labeling of antibodies [12] or the modifications of sensing surfaces [13]. This immunoassay method should be compatible with commonly used analytical lab instruments
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