Abstract
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.
Highlights
Optical imaging and manipulation of small objects is crucial in the fields of medical diagnosis[1,2], biological sensing[3,4], cellular exploration[5,6], molecular tracking[7,8], and material assembly[9,10]
All the experiments were carried out under a reflection-mode optical microscope coupled with a charge-coupled device (CCD) camera and objective lens (NA = 0.95)
The optical image could be considered as the convolution between the point-spread function (PSF) of the optical system and the intensity distribution function of the samples
Summary
Optical imaging and manipulation of small objects is crucial in the fields of medical diagnosis[1,2], biological sensing[3,4], cellular exploration[5,6], molecular tracking[7,8], and material assembly[9,10]. The past few decades have witnessed dramatic progress of near-field nanoscopes and nanotweezers that achieve optical imaging and manipulation with nanometer resolution[16,17]. 50-nm imaging resolution using microsphere nanoscopy for plasmonic samples with white-light illumination. By using high-index immersed microspheres in aqueous environments, this technique has achieved rapid development in biological applications[29,30], such as superresolution imaging of adenoviruses and subcellular structures. This microsphere-assisted imaging scheme is label-free; the current microspheres are commonly formed by artificially inorganic materials, such as silicon dioxide (SiO2), titanium dioxide (TiO2), and barium titanate (BaTiO3). A natural biomaterial is highly desired for the construction of a biocompatible and harmless device to achieve both imaging and manipulation with nanoscale spatial resolution
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