LAUSR

Nanoprobes have become critical components of the many near-field imaging techniques developed over the past decade. These tools are typically constructed by integrating nanostructures on the tip of an optical fiber, for example, by coating them with an ultrathin layer of metal; etching with plasmonic nanoantennas; or attaching them with a single gold nanorod, semiconductor nanowire, metal nanoparticle, or photonic crystal nanocavity. The optical resonances of these materials enable light to be concentrated into a confined region, illuminating samples with nanometer resolution. However, these nanostructures are usually made with noble metals or semiconductors that lack biocompatibility and can easily rupture cells when interfacing with them. In addition, their preparation often requires sophisticated nanofabrication processes and electrochemical reactions. To avoid these issues, Li et al. (DOI: 10.1021/ acsnano.8b05235) created nanoprobes made of living cells. The researchers made these tools by inserting a tapered fiber light source into a mixture of yeast and Lactobacillus acidophilus cells. Using light from the fiber as an optical trap, the researchers captured a single yeast cell onto its tip. Light conducted through that cell acted as a subsequent trapping laser beam to secure a string of connected L. acidophilus cells on top of the yeast cell. Tests showed that these nanoprobes could be used for near-field scanning imaging with a subwavelength spatial resolution to illuminate leukemia cells stained with green fluorescent protein in blood. The nanoprobes also demonstrated flexibility and deformability, bending when they contacted cells instead of rupturing them. The authors suggest that these living nanoprobes could find relevant applications in biosensing and imaging.