Single-cell biomagnifier for optical nanoscopes and nanotweezers

Optical microscopes and optical tweezers, which were invented to image and manipulate microscale objects, have revolutionized cellular and molecular biology. However, the optical resolution is hampered by the diffraction limit; thus, optical microscopes and optical tweezers cannot be directly used to image and manipulate nano-objects. The emerging plasmonic/photonic nanoscopes and nanotweezers can achieve nanometer resolution, but the high-index material structures will easily cause mechanical and photothermal damage to biospecimens. Here, we demonstrate subdiffraction-limit imaging and manipulation of nano-objects by a noninvasive device that was constructed by trapping a cell on a fiber tip. The trapped cell, acting as a biomagnifier, could magnify nanostructures with a resolution of 100 nm ( λ /5.5) under white-light microscopy. The focus of the biomagnifier formed a nano-optical trap that allowed precise manipulation of an individual nanoparticle with a radius of 50 nm. This biomagnifier provides a high-precision tool for optical imaging, sensing, and assembly of bionanomaterials. Subwavelength imaging: Seeing smaller through cells An optical microscope system that uses living cells as tiny lenses to image and manipulate objects smaller than the wavelength of light has been demonstrated by researchers in China. Optical microscopes and laser tweezers can image and trap objects as small as a few hundred nanometers, but it is difficult to apply these tools to anything smaller than half the wavelength of light because of the so-called diffraction limit. Yuchao Li and co-workers at Jinan University demonstrated that bacteria, yeast, red blood cells or stem cells positioned beneath a microscope can focus light to resolve details smaller than a fifth of the wavelength, such as the fibrous cytoskeleton in larger cells. The team also used the subwavelength light spot focused by the “biomagnifier” cells to trap and manipulate nanoparticles just 50 nanometers in radius.