Monkeypox virus (MPXV) neutralizing antibodies diagnosis with spectral-phase surface plasmon resonance 3D imaging biosensor

In this paper, we present the detection of Monkeypox virus (MPXV) neutralizing antibodies with a spectral-phase surface plasmon resonance (SPR) 3D imaging biosensor. To the best of our knowledge, this is the first demonstration of SPR imaging for MPXV neutralizing antibodies detection in the literature. The imaging biosensor provides three-dimensional molecular binding information in the x-, y- and time dimensions, enables real-time multiplex molecular bindings detection. In the optical design, a plasmonic sensing surface is placed in between a pair of polarizers with perpendicular orientation to block light transmission. At plasmonic resonance, an additional phase value is introduced for p-polarized light, while s-polarized light remains unchanged. This rotates the polarization ellipse and enables light transmission at specific plasmonic resonance wavelengths, generating the spectral-phase SPR image. In refractive index (RI) measurements, the sensor RI sensitivity was calculated to be 1191.2 Hue units/RIU. The biosensor was further applied to detect MPXV neutralizing antibodies with a 4 × 4 gold biosensor array immobilized with specific MPXV proteins and bovine serum albumin as control. The limit of detection was found to be 0.27 ng/μL with detection time of less than 16 min. This value is significantly lower than the neutralizing antibodies level (3.0 ng/μL) stimulated by MPXV vaccine reported in previous study.