An endoscope that can provide high-resolution optical images of the interior of a single living cell, or precisely deliver genes, proteins, therapeutic drugs or other cargo without injuring or damaging the cell, has been developed by researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab). This highly versatile and mechanically robust nanowire-based optical probe can also be applied to biosensing and single-cell electrophysiology.
Yang, who also holds appointments with the University of California Berkeley's Chemistry Department and Department of Materials Science and Engineering, is the corresponding author of a paper in the journal Nature Nanotechnology describing this work titled "Nanowire-based single-cell endoscopy." Co-authoring the paper were Ruoxue Yan, Ji-Ho Park, Yeonho Choi, Chul-Joon Heo, Seung-Man Yang and Luke Lee.
Despite significant advancements in electron and scanning probe microscopy, visible light microscopy remains the workhorse for the study of biological cells. Because cells are optically transparent, they can be noninvasively imaged with visible light in three-dimensions. Also, visible light allows the fluorescent tagging and detection of cellular constituents, such as proteins, nucleic acids and lipids. The one drawback to visible light imaging in biology has been the diffraction barrier, which prevents visible light from resolving structures smaller than half the wavelength of the incident light. Recent breakthroughs in nanophotonics have made it possible to overcome this barrier and bring subcellular components into view with optical imaging systems. However, such systems are complex, expensive and, oddly enough, bulky in size.
"Previously, we had shown that subwavelength dielectric nanowire waveguides can efficiently shuttle ultraviolet and visible light in air and fluidic media," Yang says. "By incorporating one of our nanophotonic components into a simple, low-cost, bench-top fibre-optical set-up, we were able to miniaturize our endoscopic system."
To test their nanowire endoscope as a local light source for subcellular imaging, Yang and his co-authors optically coupled it to an excitation laser then waveguided blue light across the membrane and into the interiors of individual HeLa cells, the most commonly used immortalized human cell line for scientific research.
"The optical output from the endoscope emission was closely confined to the nanowire tip and thereby offered highly directional and localized illumination," Yang says. "The insertion of our tin oxide nanowire into the cell cytoplasm did not induce cell death, apoptosis, significant cellular stress, or membrane rupture. Moreover, illuminating the intracellular environment of HeLa cells with blue light using the nanoprobe did not harm the cells because the illumination volume was so small, down to the picolitre-scale."
Having demonstrated the biocompatibility of their nanowire endoscope, Yang and his co-authors next tested its capabilities for delivering payloads to specific sites inside a cell. While carbon and boron nitride nanotube-based single-cell delivery systems have been reported, these systems suffer from delivery times that range from 20-to-30 minutes, plus a lack of temporal control over the delivery process. To overcome these limitations, Yang and his co-authors attached quantum dots to the tin oxide nanowire tip of their endoscope using photo-activated linkers that can be cleaved by low-power ultraviolet radiation. Within one minute, their functionalized nanowire endoscope was able to release its quantum dot cargo into the targeted intracellular sites.
"Confocal microscopy scanning of the cell confirmed that the quantum dots were successfully delivered past the fluorescently labeled membrane and into the cytoplasm," Yang says. "Photoactivation to release the dots had no significant effect on cell viability."
The highly directional blue laser light was used to excite one of two quantum dot clusters that were located only two micrometers apart. With the tight illumination area and small separation between the light source and the dots, low background fluorescence and high imaging contrast were ensured.
"In the future, in addition to optical imaging and cargo delivery, we could also use this nanowire endoscope to electrically or optically stimulate a living cell," Yang says.
The nanowires used in these experiments were originally developed to study size-dependent novel electronic and optical properties for energy applications.
This research was supported by the DOE Office of Science and a grant from the National Institutes of Health.
Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov.
DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the Unites States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov.
Lynn Yarris | EurekAlert!
What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering