Simulating Surface Plasmon Resonance for enhanced imaging of C. elegans

This manuscript reports the application of Surface Plasmon Resonance imaging for analysing C. elegans nematodes. Our aim is to utilise this simulation to examine the effect of refractive index and geometry of C. elegans in order to gain deeper insights into the nematode's biological features. Employing Fresnel equations and the Transfer-Matrix Method, we investigated these aspects at the sensor-nematode interface, which is part of a multilayer model consisting of a 50 nm gold thin film deposited on a semi-infinite glass substrate. The nematode is immobilised on the thin film via an agarose sheet that forms a microfluidics channel filled with phosphate-buffered saline (PBS). The worm is modelled as an ellipsoidal crosssection allowing us to varying ellipse parameters and adherence profile on the gold thin film. Our findings illustrate the effects of the gap between the gold film and the worm, the geometry of the worm's body, and its refractive index on SPR imaging. Our results indicate variations in the SPR response due to the geometry of both agarose and worm tissue with no observed response beyond the penetration depth of the SPR sensor. The observed range of SPR angle change was from 0 to 7 degrees, with the most substantial changes noted in the worm area. This research highlights the potential for employing highly sensitive, label-free SPR microscopy techniques in the biological imaging of the C. elegans cuticle.