Author
Xingde Li
Other affiliations: Kennedy Krieger Institute, Institute for Systems Biology, University of Washington ...read more
Bio: Xingde Li is an academic researcher from Johns Hopkins University. The author has contributed to research in topics: Optical coherence tomography & Endomicroscopy. The author has an hindex of 60, co-authored 280 publications receiving 17610 citations. Previous affiliations of Xingde Li include Kennedy Krieger Institute & Institute for Systems Biology.
Papers published on a yearly basis
Papers
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TL;DR: This tutorial review highlights the surface plasmon resonance peaks of gold nanostructures by comparing four typical examples: nanospheres, nanorods, nanoshells, and nanocages.
Abstract: The surface plasmon resonance peaks of gold nanostructures can be tuned from the visible to the near infrared region by controlling the shape and structure (solid vs. hollow). In this tutorial review we highlight this concept by comparing four typical examples: nanospheres, nanorods, nanoshells, and nanocages. A combination of this optical tunability with the inertness of gold makes gold nanostructures well suited for various biomedical applications.
1,579 citations
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TL;DR: To overcome depth-of-field limitations the authors perform zone focusing and image fusion to construct a tomogram with high transverse resolution throughout the image depth, which is to their knowledge the highest longitudinal resolution demonstrated to date for in vivo OCT imaging.
Abstract: Ultrahigh-resolution optical coherence tomography (OCT) by use of state of the art broad-bandwidth femtosecond laser technology is demonstrated and applied to in vivo subcellular imaging. Imaging is performed with a Kerr-lens mode-locked Ti:sapphire laser with double-chirped mirrors that emits sub-two-cycle pulses with bandwidths of up to 350 nm, centered at 800 nm. Longitudinal resolutions of ~1mum and transverse resolution of 3mum, with a 110-dB dynamic range, are achieved in biological tissue. To overcome depth-of-field limitations we perform zone focusing and image fusion to construct a tomogram with high transverse resolution throughout the image depth. To our knowledge this is the highest longitudinal resolution demonstrated to date for in vivo OCT imaging.
1,134 citations
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TL;DR: The preliminary photothermal results suggest that this new class of bioconjugated gold nanostructures, immuno gold nanocages, can potentially serve as an effective photothermal therapeutic agent for cancer treatment.
Abstract: Gold nanocages with a relatively small size (e.g., ∼45 nm in edge length) have been developed, and the structure of these nanocages was tailored to achieve strong absorption in the near-infrared (NIR) region for photothermal cancer treatment. Numerical calculations show that the nanocage has a large absorption cross section of 3.48 × 10-14 m2, facilitating conversion of NIR irradiation into heat. The gold nanocages were conjugated with monoclonal antibodies (anti-HER2) to target epidermal growth factor receptors (EGFR) that are overexpressed on the surface of breast cancer cells (SK-BR-3). Our preliminary photothermal results show that the nanocages strongly absorb light in the NIR region with an intensity threshold of 1.5 W/cm2 to induce thermal destruction to the cancer cells. In the intensity range of 1.5−4.7 W/cm2, the circular area of damaged cells increased linearly with the irradiation power density. These results suggest that this new class of bioconjugated gold nanostructures, immuno gold nanocag...
998 citations
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TL;DR: By controlling the molar ratio between Ag and HAuCl4, the gold nanocages could be tuned to display surface plasmon resonance peaks around 800 nm, a wavelength commonly used in optical coherence tomography (OCT) imaging.
Abstract: Gold nanocages of <40 nm in dimension have been synthesized using the galvanic replacement reaction between Ag nanocubes and HAuCl4 in an aqueous solution. By controlling the molar ratio between Ag and HAuCl4, the gold nanocages could be tuned to display surface plasmon resonance peaks around 800 nm, a wavelength commonly used in optical coherence tomography (OCT) imaging. OCT measurements on phantom samples indicate that these gold nanocages have a moderate scattering cross-section of ∼8.10 × 10-16 m2 but a very large absorption cross-section of ∼7.26 × 10-15 m2, suggesting their potential use as a new class of contrast agents for optical imaging. When bioconjugated with antibodies, the gold nanocages have also been demonstrated for specific targeting of breast cancer cells.
956 citations
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TL;DR: Ultrahigh-resolution optical coherence tomography (OCT) using continuum generation in an air-silica microstructure fiber as a low-coherence light source and imaging in biological tissue in vivo was demonstrated.
Abstract: We demonstrate ultrahigh-resolution optical coherence tomography (OCT) using continuum generation in an air–silica microstructure fiber as a low-coherence light source. A broadband OCT system was developed and imaging was performed with a bandwidth of 370 nm at a 1.3‐μm center wavelength. Longitudinal resolutions of 2.5 μm in air and ∼2 μm in tissue were achieved. Ultrahigh-resolution imaging in biological tissuein vivo was demonstrated.
956 citations
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TL;DR: This work reviews recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
7,987 citations
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TL;DR: The arsenal of nanocarriers and molecules available for selective tumour targeting, and the challenges in cancer treatment are detailed and emphasized.
Abstract: Nanotechnology has the potential to revolutionize cancer diagnosis and therapy. Advances in protein engineering and materials science have contributed to novel nanoscale targeting approaches that may bring new hope to cancer patients. Several therapeutic nanocarriers have been approved for clinical use. However, to date, there are only a few clinically approved nanocarriers that incorporate molecules to selectively bind and target cancer cells. This review examines some of the approved formulations and discusses the challenges in translating basic research to the clinic. We detail the arsenal of nanocarriers and molecules available for selective tumour targeting, and emphasize the challenges in cancer treatment.
7,443 citations
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TL;DR: A comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals, including a brief introduction to nucleation and growth within the context of metal Nanocrystal synthesis, followed by a discussion of the possible shapes that aMetal nanocrystal might take under different conditions.
Abstract: Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.
4,927 citations
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TL;DR: The intracellular uptake of different sized and shaped colloidal gold nanoparticles is investigated and it is shown that kinetics and saturation concentrations are highly dependent upon the physical dimensions of the nanoparticles.
Abstract: We investigated the intracellular uptake of different sized and shaped colloidal gold nanoparticles. We showed that kinetics and saturation concentrations are highly dependent upon the physical dimensions of the nanoparticles (e.g., uptake half-life of 14, 50, and 74 nm nanoparticles is 2.10, 1.90, and 2.24 h, respectively). The findings from this study will have implications in the chemical design of nanostructures for biomedical applications (e.g., tuning intracellular delivery rates and amounts by nanoscale dimensions and engineering complex, multifunctional nanostructures for imaging and therapeutics).
4,383 citations
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TL;DR: While nanorods with a higher aspect ratio along with a smaller effective radius are the best photoabsorbing nanoparticles, the highest scattering contrast for imaging applications is obtained from nanorod of high aspect ratio with a larger effective radius.
Abstract: The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica−gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range commonly employed (∼40 nm)...
4,065 citations