A Camera Phone Localised Surface Plasmon Biosensing Platform Towards Low-Cost Label-Free Diagnostic Testing

Developmental work towards a camera phone diagnostic platform applying localized surface plasmon resonance (LSPR) labelfree sensing is presented. The application of spherical gold nanoparticles and nanorods are considered and assessed against ease of application, sensitivity, and practicality for a sensor for the detection of CCL2 (chemokine ligand 2). The sensitivity of the platform is compared with that of a commercial UV/Vis spectrometer. The sensitivity of the camera phone platform is found to be 30% less than that of the commercial system for an equivalent incubation time, but approaches that of the commercial system as incubation time increases. This suggests that the application of LSPR sensing on a portable camera phone devices may be a highly effective label-free approach for point-of-care use as a low-cost diagnostic sensing tool in environments where dedicated equipment is not available

Spectro-angular optical biosensor based on surface plasmon resonance operating in the visible spectrum

Surface plasmon resonance (SPR) is one of the most widely used methods to implement biosensors because of its label-free and sensitive detection. Surface plasmon resonance allows the change in the refractive index of a sample to be measured accurately by the analysis of the light reflecting at a metal-dielectric interface. A way to increase the sensitivity of SPR biosensors was found in fabricating a spectro-angular SPR biosensor and using of a newly developed data processing method called the Double Projection Method. The objective of the work presented in this thesis is to improve further the detection limit of the spectro-angular biosensor by upgrading the cameras used for the data acquisition. Simulations have shown that the spatial resolution and the data precision have a significant impact on the accuracy of the refractive index change measurement. In this thesis, simulation results are presented to justify the modifications of the experimental system and to estimate the expected improvement in the detection limit of the spectro-angular biosensor by the use of higher spatial resolution and higher data precision cameras. The new design as well as the components purchased for the experimental set-up are detailed.La résonance plasmonique de surface (SPR) est une méthode très utilisée pour la réalisation de biocapteurs grâce à sa détection très sensible et sans marqueur. La résonance plasmonique de surface permet une mesure précise du changement de l'indice de réfraction d'un échantillon par l'analyse de la lumière reflétant sur l'interface entre un métal et un diélectrique. Il a été démontré que la sensibilité des biocapteurs SPR puisse être accrue par la fabrication d'un biocapteur SPR spectro-angulaire utilisant une nouvelle méthode de traitement des données appelée Double Projection Method (la méthode par double projection). L'objectif du travail présenté dans cette thèse est d'améliorer la limite de détection du biocapteur spectro-angulaire grâce à l'utilisation de caméras plus performantes pour la cueillette de données. Des simulations ont démontré que la résolution spatiale et la précision des données ont un impact significatif sur la précision de la mesure du changement dans l'indice de réfraction. Dans cette thèse, des résultats de simulations seront présentés afin de justifier les modifications à apporter au système expérimental et de démontrer l'amélioration prévue de la limite de détection du biocapteur spectro-angulaire par l'utilisation de caméras plus performantes. La nouvelle conception ainsi que les composantes choisis pour le système expérimental seront détaillées

Design and analysis of a spectro-angular surface plasmon resonance biosensor operating in the visible spectrum

Surface plasmon resonance (SPR) sensing is one of the most widely used methods to implement biosensing due to its sensitivity and capacity for label-free detection. Whilst most commercial SPR sensors operate in the angular regime, it has recently been shown that an increase in sensitivity and a greater robustness against noise can be achieved by measuring the reflectivity when varying both the angle and wavelength simultaneously, in a so-called spectro-angular SPR biosensor. A single value decomposition method is used to project the two-dimensional spectro-angular reflection signal onto a basis set and allow the image obtained from an unknown refractive index sample to be compared very accurately with a pre-calculated reference set. Herein we demonstrate that a previously reported system operated in the near infra-red has a lower detection limit when operating in the visible spectrum due to the improved spatial resolution and numerical precision of the image sensor. The SPR biosensor presented here has an experimental detection limit of 9.8 × 10−7 refractive index unit. To validate the system as a biosensor, we also performed the detection of synthetic RNA from pathogenic Legionella pneumophila with the developed biosensing platform

A Camera Phone Localised Surface Plasmon Biosensing Platform towards Low-Cost Label-Free Diagnostic Testing

Developmental work towards a camera phone diagnostic platform applying localized surface plasmon resonance (LSPR) label-free sensing is presented. The application of spherical gold nanoparticles and nanorods are considered and assessed against ease of application, sensitivity, and practicality for a sensor for the detection of CCL2 (chemokine ligand 2). The sensitivity of the platform is compared with that of a commercial UV/Vis spectrometer. The sensitivity of the camera phone platform is found to be 30% less than that of the commercial system for an equivalent incubation time, but approaches that of the commercial system as incubation time increases. This suggests that the application of LSPR sensing on a portable camera phone devices may be a highly effective label-free approach for point-of-care use as a low-cost diagnostic sensing tool in environments where dedicated equipment is not available