Nanoporous Polymeric Grating-based Optical Biosensors (preprint)

This paper demonstrates a label-free biological sensing method usmg nanoporous polymer gratings. The high index modulation (0.07) of the nanoporous polymer grating structure generates a high signal-to-noise ratio, making the structure an ideal label-free biodetection platform. The fabrication process of the nanoporous polymeric grating involves holographic interference patterning and a functionalized pre-polymer syrup that facilitates the immobilization of biomolecules onto the polymeric sensor surface. The performance of the nanoporous polymeric sensor is evaluated by sequentially capturing biomolecules (biotin, steptavidin, biotinylated anti-rabbit IgG, and rabbit-IgG) onto the nanoporous regions and monitoring the changes in diffraction and transmission intensity. We have observed that diffraction intensity decreases and transmission intensity increases as biomolecules bind to the polymer structures, an observation consistent with our theoretical analysis. Furthermore, high molecular selectivity is demonstrated within this assay by immobilizing anti-rabbit IgG within the nanoporous polymer and observing the changes in the transmission and diffraction intensities upon the grating's exposure to rabbit and goat IgG (control). The two optical responses are profoundly different for each biomolecule and the selective binding of rabbit IgG is clearly evident. The nanoporous polymer grating-based biosensing method described in this paper is inexpensive, labelfree, and amenable as a high-throughput assay, characteristics pertinent in many biomedical research and clinical applications.