Nanophotonic materials promise to make a splash in biomedical imaging and diagnostics, provided they can ‘shine’ in dynamic aqueous environments. Here we present our research developing nanophotonic imaging tools for bacterial identification, cellular mapping, and inter-cellular force visualization. First, we combine Raman spectroscopy and deep learning to accurately classify bacteria by both species and antibiotic resistance in a single step. We design a convolutional neural network (CNN) for spectral data and train it to identify 30 of the most common bacterial strains from single-cell Raman spectra, achieving antibiotic treatment identification accuracies exceeding 99% and species identification accuracies similar to leading mass spectrometry identification techniques. Our combined Raman-CNN system represents a proof-of-concept for rapid, culture-free identification of bacterial isolates and antibiotic resistance. Second, we describe a new technique for high-resolution vibrational spectroscopy in the TEM: electron-and-light-induced stimulated Raman scattering (ELISR). Unlike conventional stimulated Raman measurements, our technique uses a laser source as the pump and the electron beam as the broadband Stokes excitation. A small plasmonic nanoparticle amplifies the local Raman signature, with the spatial resolution determined by the electron beam spot size and the nanoparticle size. We show how this technique can enable molecular mapping at the nanoscale, en-route to an “atlas” of cellular receptors. Finally, we introduce a new class of in vivo optical probes to monitor biological forces with high spatial and temporal resolution. Our design is based on upconverting nanoparticles that, when excited in the near-infrared, emit light of a different color and intensity in response to microNewton forces. The nanoparticles are sub-30nm in size, do not bleach or photoblink, and can enable deep tissue imaging with minimal tissue autofluorescence. We present the design, synthesis, and characterization of these nanoparticles both in vitro and in vivo, focusing on the forces generated by the roundworm C. elegans as it feeds and digests its bacterial food. Chronic cytotoxicity assays are used to confirm biocompatibility. Our force measurements are coupled with electrical measurements of muscle contractions in both wild-type and mutant animals, providing insight into the interplay between mechanical, electrical, and chemical signaling in vivo.

Aqueous-phase nanophotonic materials to probe molecular and cellular processes

2019 Fall National Meeting

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