Janus Emulsion Biosensors for Anti-SARS-CoV-2 Spike Antibody

Abstract

The spread of the COVID-19 pandemic around the world has revealed that it is urgently important to develop rapid and inexpensive assays for antibodies in general and anti-SARS-CoV-2 IgG antibody (anti-SARS-CoV-2 spike glycoprotein S1 antibody) in particular. Herein we report a method to detect the anti-SARS-CoV-2 spike antibody level by using Janus emulsions or Janus particles as biosensors. Janus emulsions are composed of two immiscible hydrocarbon and fluorocarbon oils. The hydrocarbon/water interfaces are functionalized with a secondary antibody of IgG protein and SARS-CoV-2 spike receptor binding domain (RBD), to produce two different Janus emulsions. Mixtures of these Janus droplets enable the detection of the anti-SARS-CoV-2 spike IgG antibody in an agglutination assay caused by the antibody’s binding to both the secondary antibody of IgG antibody and SARS-CoV-2 spike protein RBD. Both qualitative optical images and quantitative fluorescence spectra are able to detect the level of anti-SARS-CoV-2 spike antibody at concentrations as low as 0.2 μg/mL in 2 h. The detection results of clinical human serum samples using this agglutination assay confirm that this method is applicable to clinical samples with good sensitivity and specificity. The reported method is generalizable and can be used to detect other analytes by attaching different biomolecular recognition elements to the surface of the Janus droplets.

Detection of PFAS and Fluorinated Surfactants Using Differential Behaviors at Interfaces of Complex Droplets

“…Previous work by Swager, Zarzar, and Zeininger has demonstrated the various methods of leveraging complex droplets for selective detection of analytes. − A key strategy used in this work relies on the coupling between their dynamic morphology and emission intensity as the result of the changing interfacial tensions. That is, depending on the morphology of the droplets, the emission intensity of the embedded fluorescent dye varies significantly.…”

“…Of particular interest to sensing applications, this dynamic physical transformation can be visualized via an optical microscope or by a measurement of transmitted or emissive light. For example, droplet-based sensors have leveraged the change in transparency, , scattering efficiency, − and emission intensity , to detect enzyme activities, , foodborne pathogens, ,,, viruses, , and trace chemicals. ,, In these examples, the minute changes in interfacial behavior produce easily detectable signals and provide a novel and rapid alternative to a conventional tensiometer.…”

Multifunctional Photonic Janus Particles

“…Janus particles are promising candidates for biosensing applications with spatial functionalization allowing for sensing mechanisms based on the orientation of particles. − Herein, we utilize the angle-dependent reflection of den -BBCP/P4VP- r -PS particles to develop a novel photonic sensor for Salmonella bacteria, a food pathogen that causes a gastrointestinal infection. Our sensing scheme involves the functionalization of Fe 3 O 4 -coated photonic Janus particles with anti- Salmonella antibody and the agglutination of antibody-modified particles triggered by Salmonella (Figure a).…”

Application of Janus Particles in Point-of-Care Testing

“…Additionally, the SARS-CoV-2 spike receptor-binding domain (RBD) [ 194 ] and IgG protein secondary antibody were used to functionalize the hydrocarbon/water interface, resulting in two distinct Janus emulsions [ 121 ]. A mixture of these Janus droplets could be detected in an agglutination test against SARS-CoV-2 spike IgG antibodies, which were caused by the binding of this antibody to the secondary antibody of the IgG antibody and the SARS-CoV-2 spike protein RBD.…”