J. Eur. Opt. Society-Rapid Publ. 2026, 22, 34 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026039 Available online at: https:// jeos. edpsciences. org
EOSAM 2025 Guest editors: Omar El Gawhary, Stefan Witte, Ignacio Moreno
Journal of the European Optical Society-Rapid Publications
SHORT COMMUNICATION
Monkeypox virus( MPXV) neutralizing antibodies diagnosis with spectral-phase surface plasmon resonance 3D imaging biosensor Chi Lok Wong * Department of Electrical Engineering, Chang Gung University, Taiwan R. O. C
Received 9 December 2025 / Accepted 12 April 2026
Abstract. 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 / lL with detection time of less than 16 min. This value is significantly lower than the neutralizing antibodies level( 3.0 ng / lL) stimulated by MPXV vaccine reported in previous study.
Keywords: Monkeypox virus, MPXV, Neutralizing antibodies, SPR imaging, Biosensor, Spectral-phase.
1 Introduction
According to World Health Organization( WHO), an outbreak of Monkeypox happened in May 2022 and rapidly spread across Africa countries, Europe, the Americas and Southeast Asia. Monkeypox cases have been reported in over 120 countries worldwide. Between January 2022 to August 2024, cumulative infection cases reached 1 million and 220 deaths was reported. The Monkeypox virus( MPXV) belongs to the orthopoxvirus genus within the poxviridae family of vaccinia virus, variola virus and cowpox virus [ 1 ]. The diagnosis of MPXV neutralizing antibodies in patients contributes not only to vaccination development and efficacy evaluation, but also to governmental public health planning during outbreak. Current detection methods include Plaque-Reduction Neutralization Test( PRNT), Focus Reduction Neutralization Test( FRNT) and Enzyme-Linked Immunosorbent Assay( ELISA) [ 2 ]. However, PRNT and FRNT suffer from long detection time of 3 – 5 days and 1 – 2 days, respectively, while ELISA involves complex labeling and sandwich detection
* Corresponding author: clwong @ mail. cgu. edu. tw; davewongastar @ gmail. com process [ 2 ]. Furthermore, trained staffs and centralized laboratory facilities are required, which are often lacking in Monkeypox outbreak areas, such as The Democratic Republic of the Congo and other Africa countries.
In this paper, we propose a spectral-phase surface plasmon resonance( SPR) 3D imaging biosensor for rapid MPXV neutralizing antibodies diagnosis. The biosensor provides rapid detection results in 16 min without requiring any labeling process. Furthermore, it is a potential point-ofcare diagnostic tool, which contributes to patient care in developing countries experiencing Monkeypox outbreaks. In the optical design, the plasmonic sensor head is placed between two crossed polarizers for light blocking. At plasmonic resonance wavelength, a differential phase response is introduced between p- and s-polarized light [ 3 ], which rotates the polarization ellipse and allows light at resonance wavelengths [ 4 ] to pass through, resulting in a spectralphase plasmonic color image. In addition, the excitation beam is expanded to cover a two-dimensional( 2D) gold sensor spots array( 4 4 elements). As video data are captured over the sensor surface, the biosensor can provide three-dimensional( 3D) molecular binding information in the x-, y- and time dimensions, which enables real-time acquisition of multiplex molecular binding curves for
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