Biomimetic Photonic Crystal based SERS substrates for Biomolecule Detection

P. Macha, M.C. Vasudev
University of Massachusetts Dartmouth,
United States

Keywords: biomimetic, nanostructures, lithography


Nature has perfected the design of photonic structures, resulting in brilliant structural coloration such as the ones seen in the Morpho butterfly wings and the elytra of beetle species such Chrysochroa. Two-dimensional (2D) photonic crystals such as the eye spots on peacock feathers and ctenophore species such as Bereo Cucumis and Mnemiopsis Leidyi, occur relatively less frequently in nature. Photonic crystals have gained great interest in the field of biosensors specifically for point of care diagnostics, which can benefit from label-free and highly sensitive detection. The traditional analytical systems are time-consuming, labor-intensive and expensive. Replacing these methods with simple but advanced detection mechanisms could be cost effective with reduced assay time for early stage detection. The 2D photonic crystals structure in the comb jellies were studied using the embedded cross-sections of the ciliary structure imaged using a high-resolution transmission electron microscope (HR-TEM). These structures were used as a template for the fabrication of photonic crystal structures using two different approaches, two-photon lithography, and e-beam lithography, to replicate the ciliary arrangements. Hard stamps were created from the EBL generated structures and used for nanoimprinting of polymers. The morphology of the synthesized polymeric structures was observed using scanning electron microscopy and their reflectivity spectra was analyzed. Polymer composition was modified to bind peptides which reduce gold nanoparticles from the auric chloride solution. Surface-enhanced Raman scattering (SERS) active surface were created due to the controlled spacing between the nanoparticles leading to the formation of ‘hotspots’ for analyte detection. Tumor markers in blood plasma were detected using the photonic crystal substrate coated with gold nanoparticles leading to plasmonic band-gap enhancement and hence enhancement of the biomolecular signature. This could lead to detection of low levels of protein or metabolite markers in serum hitherto unidentified.