Depositing Highly Uniform Au Nanoparticles on the Surface of High-Curvature Nanofibers for SERS Optophysiology

Abstract

Nanofibers as biosensors have attracted great attention due to its facile removal from the biosystem after a period of intra- or extracellular measurements and site-specific measurement among others. The application of nanofibers covered with Au nanoparticles as SERS sensor circumvents the aggregation and accumulation of Au nanoparticles in vitro or in vivo, in addition to the greater Raman enhancement of signal than on planar surface. To achieve this, our group has reported a block copolymer-template method to deposit Au nanoparticles on the highly curved surface of nanofibers.[1] Here the versatility of this strategy is demonstrated by depositing nanoparticles with the different dimensions or shapes and varying the density of Au nanoparticles on the surface of the nanofibers. To the best of our knowledge, we believe this is the first work to show how to obtain such highly uniform distribution of anistropic nanoparticles on the surface of high-curvature nanofibers. Among all the nanosensors studied in this work, the label-free nanofibers covered with Au nanostars with shorter branches shows the biggest enhancement, which could detect neurotransmitter secretion such as dopamine with moderate laser power and low integration time. Furthermore, measurement of pH in the cell microenvironment and pH gradient in the cell medium can be realized by our biosensors as well. The rapid pH response to the external environment makes it very promising for the application of the dynamic pH measurement in vitro or in vivo. In addition to SERS sensing, these highly uniform nanosensors have other far-reaching implications, including medical diagnostics, therapeutics and so on.[1] Zhu, H., Lussier, F., Ducrot, C., Bourque, M. J., Spatz, J. P., Cui, W., Yu, L., Peng, W., Trudeau, L. E., Bazuin, C. G. and Masson, J. F., ACS Appl. Mater. Interfaces, 2019, DOI: 10.1021/acsami.8b19161. Figure 1