The ability to stimulate, track, and record biological processes with as many data channels as possible is central to decoding complex phenomena in the body. For example, many biological processes involve small mechanical cues that can help drive chemical reactions and/or initiate responses to external stimuli. However, to measure these nanomechanical events, specialized tools are required that can not only achieve piconewton force resolution, but be able to record from multiple sites while maintaining a small footprint to allow embedded or intracellular measurements. This is challenging for state-of-the-art instruments such as atomic force microscopes or optical traps due to the difficulty in multiplexing, their size, and feedback mechanisms. Here we describe a new nanofiber-optic platform that can detect sub-piconewton forces by monitoring far-field scattering signals of plasmonic nanoparticles moving within the near-field. To provide mechanical resistance to the nanoparticles, and allow quantitative forces to be extracted, compressible polymer claddings have been designed that have tunable spring constants and chemical compositions. The transduction mechanism is demonstrated both on detecting local contact forces acting on the nanoparticles as well as acoustic waves propagating in the medium. Because of the small cross-sectional areas (< 1 um2) and long lengths (> 1 mm), these nanofibers can also be inserted deep into tissue to locally excite and collect signals from single cells (e.g., neurons) with minimal invasiveness. Experiments focused on stimulating and recording from brain tissue will be discussed.
Donald J. Sirbuly, Qian Huang, and Josh Villanueva, "Nanoengineering of optical probes for in situ nanomechanical studies and biological interrogation (Conference Presentation)," Proc. SPIE 9927, Nanoengineering: Fabrication, Properties, Optics, and Devices XIII, 99270Y (Presented at SPIE Nanoscience + Engineering: August 31, 2016; Published: 3 November 2016); https://doi.org/10.1117/12.2238114.5163995443001.
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