Accelerated detection of viral particles by combining AC electric field effects and micro-Raman spectroscopy

Abstract

A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the "fingerprinting" capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres) captured by an AC electric field between planar microelectrodes is presented with a methodology for analyzing the resulting spectra by comparing relative peak intensities. The same principle is applied to dielectrophoretically captured M13 phage particles whose presence is indirectly confirmed with micro-Raman spectroscopy using NeutrAvidin-Cy3 as a labeling molecule. It is concluded that the combination of electrokinetically driven virus sampling and micro-Raman based signal transduction provides a promising approach for time-efficient and in situ detection of viruses.

Figure 1.

Quadrupolar microelectrodes with (a) 10 µm tip to tip spacing between opposite electrodes used for the collection of NAVDY particles and (b) 4 µm tip to tip spacing used for the collection of M13 phage.

Figure 2.

Micro-Raman Spectra of a cleaned silicon surface (black dashed line, left y-axis) and a dried, densely packed, photobleached layer NAVDY particles on a glass slide (red solid line, right y-axis).

Figure 3.

Micro-Raman mapping for the identification of NAVDY particles. (a) UV-light image of NAVDY particles captured in the center of microelectrodes; (b) Magnified view of the area outlined with a white box in (a) as appears under visible light; (c) SEM image of NAVDY particles captured on an anti-avidin functionalized surface; (d) Micro-Raman mapping of a portion of the SEM image as indicated by the dashed lines.

Figure 4.

Demonstration of M13 capture using triangular electrodes with a gap spacing of 4 μm. Left: Visible light (top) and UV light (bottom) images of anti-fd functionalized electrodes. Right: Visible light (top) and UV light (bottom) images of anti-fd functionalized electrodes with dielectrophoretically captured M13 phage. Conditions: V_pp = 15 V, f = 1 MHz, capture time: 30 min.

Figure 5.

Micro-Raman spectra collected from an anti-fd functionalized microelectrode with captured M13 phages bound to biotinylated-anti-fd reacted with ExtrAvidin-Cy3 prior to photobleaching. The inset in the top right is a magnified image of the collection presented in Figure 4. Black line (positive shifted by 1000 A.U.): a photobleached sample of ExtrAvidin-Cy3 on Silicon. Purple line (positive shifted by 800 A.U.): a scan from the top left point in the inset (indicated by the purple dot). Yellow line (positive shifted by 250 A.U.): a scan from the bottom left point in the inset (indicated by the yellow dot). Green line: a scan from the bottom right point in the inset (indicated by the green dot).