OCE-PRF: Lighting up the ocean: resonant nanophotonic metasurfaces for autonomous in situ measurement of aquatic phycotoxins

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OCE-PRF: Lighting up the Ocean: resonant nanophotonic metasurfaces for autonomous in situ measurement of aquatic biotoxins The changing climate is driving fundamental shifts in marine and freshwater ecosystems. Phytoplankton are microscopic organisms responsible for half of the global photosynthetic carbon fixation and at least half of the world’s oxygen production. However, certain kinds of phytoplankton can produce powerful biotoxins that harm humans and wildlife, contaminate water sources, and damage local economies. Sensors for phytoplankton toxin production are a critical infrastructure needed to advance both fundamental research and climate resilience. However, current methods of studying phytoplankton toxins and their genes are based on methods that are costly, require sophisticated infrastructure, and lack remote, real-time detection capabilities central to understanding the dynamics of the coupled water/climate ecosystem. This project addresses this gap by developing a new optical measurement technique that uses nanostructured silicon surfaces to amplify light for sensitive detection of target molecules. This project will support the postdoctoral research fellow, includes training of undergraduates from primarily undergraduate institutions, and seeks to contribute key resources and data for better resource management and public water stewardship.Microscopic photosynthetic organisms, phytoplankton, are an essential part of the earth’s carbon cycle and are critical to driving biogeochemical cycles. But under certain conditions, phytoplankton can undergo explosive growth forming dense blooms called harmful algal blooms (HABs) that can cover hundreds of square kilometers and produce powerful biotoxins. Understanding how environmental drivers impact plankton nutrient cycling and toxin production is key to advancing climate resilience but remains an outstanding measurement challenge. Methods of monitoring HABs and understanding toxin dynamics are largely based on microscopy, mass spectroscopy, and PCR; techniques that are time consuming, require sophisticated infrastructure, and lack the real-time in situ detection capabilities necessary to understand how the physicochemical environment drives phytoplankton metabolic dynamics in a changing ecosystem. This postdoctoral fellowship aims to address this gap by developing high quality factor (high-Q) nanophotonics for sensitive, quantitative, amplification-free, and label-free detection of aquatic phycotoxins in near real-time and in situ. Rather than amplifying a biomolecule to successfully detect it, high-Q metasurfaces use nanostructured silicon to strongly amplify laser light at molecular binding sites to enable sensitive detection of target molecules in a scalable, highly multiplexed, all-optical platform with a compact footprint. This postdoctoral fellowship will focus on two phycotoxins: domoic acid, a neurotoxin produced by the marine diatoms, Pseudo-nitzschia spp., that is responsible for human and wildlife mortalities, and microcystin, a liver toxin produced by cyanobacteria and that poses a major threat to drinking, recreational, and agricultural water supplies. While domoic acid is a low molecular weight L- proline derivative, microcystin is a relatively large cyclic peptide; together these two prevalent phycotoxins will demonstrate the broad applicability of this technique across marine metabolites and diverse environments. Together, this research will enable real-time quantitative detection of phycotoxins over a large range of concentrations and environmental conditions. The outputs of this work will be an avenue for real-time measurements of phycotoxins, which can be combined with and interpreted in the context of correlative measurements of temperature, pH, and chlorophyll fluorescence, deepening our fundamental understanding of how changing climate conditions drive phytoplankton productivity and toxin production.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.