Abstract
Over the past few decades, cancer and other fatal diseases have become more prevalent affecting large populations around the world. Earlier detection could improve prognosis for the patient. A possible solution includes using photonic crystal-based sensors to detect biomarkers in exosomes shed by cancerous cells. Photonic crystals have become increasingly important for biosensor applications due to the need for a label-free alternative to detect biomarkers. Surface enhanced Raman scattering (SERS) using gold nanoparticles is a sensitive analytical technique, which has been exploited in chemical, molecule and environmental monitoring. In this study, a photonic crystal SERS substrate was designed and synthesized for the early detection of changes which occur in the exosomes shed by the cancerous cells. Optical signal amplification due to gold nanoparticles and photonic components, leads to the enhanced interactions between the analyte and the sensor. Electromagnetic enhancement using a photonic crystal substrate can greatly enhance the SERS detection when compared to traditional methods. The two-dimensional photonic structural organization in the comb structures of the ctenophore species, Mnemiopsis Leidyi and Beroe Cucumis was used as the inspiration to design the photonic crystal substrate used in this study. The structural organization of the cilia in the comb rows consists of arrays of hexagonally packed cilia with a central microtubule pair. Transmission electron microscopy was used to study the arrangements of the comb structures as reverse engineering of these submicron structures aids in designing a novel photonic template. The design of the comb structures was recreated using AutoCAD and Raith software. Photonic nanostructures were synthesized using the direct-write e-beam lithography technique. The structures were characterized using scanning electron microscope (SEM). Gold nanoparticles will be used in conjugation with the photonic crystal structure and Raman signatures will be analyzed both with and without gold molecules in the future. Finally, the gold coated photonic templates will be utilized as a SERS active surface for exosomal detection. Some advantages of utilizing photonic crystals include point of care diagnostics and their response to a multitude of external stimuli including light.