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.

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A roadmap for graphene

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.

Nanocarriers as an emerging platform for cancer therapy

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.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

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).

Determining the size and shape dependence of gold nanoparticle uptake into mammalian cells.

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)...

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Calculated Absorption and Scattering Properties of Gold Nanoparticles of Different Size, Shape, and Composition: Applications in Biological Imaging and Biomedicine

Visualization and Validation of The Microstructures in The Airway Wall in vivo Using Diffractive Optical Coherence Tomography.

The present invention is directed to a fiber optic device that enables multiphoton imaging with improved signal-to-noise ratio having a single piece of double-clad fiber (DCF). The device also includes all components for focusing, scanning and signal collection within an endomicroscope probe of 2.1 mm outer diameter (OD). The unprecedented imaging capability of this miniature endomicroscope is demonstrated herein via both ex vivo and in vivo experiments.

Fiber-optic methods and devices enabling multiphoton imaging with improved signal to-noise ratio

Objective/background: In vivo imaging and quantification of the microstructures of small airways in three dimensions (3D) allows a better understanding and management of airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD). At present, the resolution and contrast of the currently available conventional optical coherence tomography (OCT) imaging technologies operating at 1300 nm remain challenging to directly visualize the fine microstructures of small airways in vivo. Methods: We developed an ultrahigh-resolution diffractive endoscopic OCT at 800 nm to afford a resolving power of 1.7 μm (in tissue) with an improved contrast and a custom deep residual learning based image segmentation framework to perform accurate and automated 3D quantification of airway anatomy. Results: The 800-nm diffractive OCT enabled the direct delineation of the structural components in the small airway wall in vivo. We further first demonstrated the 3D anatomic quantification of critical tissue compartments of small airways in sheep using the automated segmentation method. Conclusion: The deep learning assisted diffractive OCT provides a unique ability to access the small airways, directly visualize and quantify the important tissue compartments, such as airway smooth muscle, in the airway wall in vivo in 3D. Significance: These pilot results suggest a potential technology for calculating volumetric measurements of small airways in patients in vivo.

Direct Visualization and Quantitative Imaging of Small Airway Anatomy Using Deep Learning Assisted Diffractive OCT

We present a design of a miniature fiber-optic probe capable of rapid lateral scanning. The miniature probe permits forward-looking optical coherence tomography (OCT) imaging of internal organs in real time. Fast lateral scanning also enables a new real-time image acquisition sequence, potentially permitting real-time focus tracking. To perform sensitive heterodyne detection, a sufficient Doppler frequency is achieved by using an electro-optic (EO) phase modulator. In this paper we describe an effective approach to compensate the dispersion induced by the EO crystal up to the third order. We show that an optimal axial resolution offered by the light source can be recovered through the dispersion management. Preliminary results of real-time OCT imaging of biological tissues with the lateral-priority scanning probe are presented.

Development of a fast scanning miniature probe and methods of dispersion management for high-resolution optical coherence tomography

We describe a generic method to optimize the optical spectral throughput of a pair of acousto-optic modulators (AOM) which can be used for introducing a frequency shift in ultrahigh-resolution heterodyne optical coherence tomography. Systematic and quantitative analysis of a pair of AOMs indicates that a configuration with a spectral bandwidth of more than 200 nm at a center wavelength of 825 nm (tunable) can be achieved. Using a pair of AOMs in conjunction with a broadband low coherence light source, real-time imaging of biological tissues with an axial resolution ~3 μm (in air) has been experimentally demonstrated with a high-speed OCT system.

Xingde Li

Papers

Visualization and Validation of The Microstructures in The Airway Wall in vivo Using Diffractive Optical Coherence Tomography.

Fiber-optic methods and devices enabling multiphoton imaging with improved signal to-noise ratio

Direct Visualization and Quantitative Imaging of Small Airway Anatomy Using Deep Learning Assisted Diffractive OCT

Development of a fast scanning miniature probe and methods of dispersion management for high-resolution optical coherence tomography

Optimization of optical spectral throughput of acousto-optic modulators for high-speed optical coherence tomography.