Applications In Super-resolution Imaging Research Articles

Terahertz metalenses for evanescent wave focusing and super-resolution imaging

Super-resolution focusing in the metamaterials for both the propagating and evanescent wave emerging from free space is demonstrated based on the gradient-index (GRIN) metalenses. The theoretical investigation reveals that the evanescent wave in free space can be transformed into propagating wave in the metamaterial due to the specific dispersion of the metamaterial. So spatial Fourier transform (FT) with broad input angular spectrum are achieved when the metamaterials are designed with GRIN. Furthermore, the application of super-resolution imaging based on the spatial FT is also presented.

Single-molecule microscopy of molecules tagged with GFP or RFP derivatives in mammalian cells using nanobody binders

With the recent development of single-molecule localization-based superresolution microscopy, the imaging of cellular structures at a resolution below the diffraction-limit of light has become a widespread technique. While single fluorescent molecules can be resolved in the nanometer range, the delivery of these molecules to the authentic structure in the cell via traditional antibody-mediated techniques can add substantial error due to the size of the antibodies. Accurate and quantitative labeling of cellular molecules has thus become one of the bottlenecks in the race for highest resolution of target structures. Here we illustrate in detail how to use small, high affinity nanobody binders against GFP and RFP family proteins for highly generic labeling of fusion constructs with bright organic dyes. We provide detailed protocols and examples for their application in superresolution imaging and single particle tracking and demonstrate advantages over conventional labeling approaches.

Advancing Applications of Super-Resolution Imaging: 10 November 2014, Charles Darwin House, London, UK

Advancing Applications of Super-Resolution Imaging: 10 November 2014, Charles Darwin House, London, UK

Photoswitchable fluorescent nanoparticles and their emerging applications

Although fluorescence offers ultrasensitivity, real-world applications of fluorescence techniques encounter many practical problems. As a noninvasive means to investigate biomolecular mechanisms, pathways, and regulations in living cells, the intrinsic heterogeneity and inherent complexity of biological samples always generates optical interferences such as autofluorescence. Therefore, innovative fluorescence technologies are needed to enhance measurement reliability while not compromising sensitivity. In this review, we present current strategies that use photoswitchable nanoparticles to address these real-world challenges. The unique feature in these photoswitchable nanoparticles is that fundamental molecular photoswitches are playing the critical role of fluorescence modulation rather than traditional methods like modulating the light source. As a result, new innovative technologies that have recently emerged include super-resolution imaging, frequency-domain imaging, antiphase dual-color correlation, etc. Some of these methods improve imaging resolution down to the nanometer level, while others boost the detection sensitivity by orders of magnitude and confirm the nanoparticle probes unambiguously. These enhancements, which are not possible with non-photoswitching molecular probes, are the central topics of this review.

Micelle-templated composite quantum dots for super-resolution imaging

Quantum dots (QDs) have tremendous potential for biomedical imaging, including super-resolution techniques that permit imaging below the diffraction limit. However, most QDs are produced via organic methods, and hence require surface treatment to render them water-soluble for biological applications. Previously, we reported a micelle-templating method that yields nanocomposites containing multiple core/shell ZnS–CdSe QDs within the same nanocarrier, increasing overall particle brightness and virtually eliminating QD blinking. Here, this technique is extended to the encapsulation of Mn-doped ZnSe QDs (Mn–ZnSe QDs), which have potential applications in super-resolution imaging as a result of the introduction of Mn2+ dopant energy levels. The size, shape and fluorescence characteristics of these doped QD-micelles were compared to those of micelles created using core/shell ZnS–CdSe QDs (ZnS–CdSe QD-micelles). Additionally, the stability of both types of particles to photo-oxidation was investigated. Compared to commercial QDs, micelle-templated QDs demonstrated superior fluorescence intensity, higher signal-to-noise ratios, and greater stability against photo-oxidization,while reducing blinking. Additionally, the fluorescence of doped QD-micelles could be modulated from a bright ‘on’ state to a dark ‘off’ state, with a modulation depth of up to 76%, suggesting the potential of doped QD-micelles for applications in super-resolution imaging.

Live, Video-Rate Super-Resolution Microscopy Using Structured Illumination and Rapid GPU-Based Parallel Processing

Structured illumination fluorescence microscopy is a powerful super-resolution method that is capable of achieving a resolution below 100 nm. Each super-resolution image is computationally constructed from a set of differentially illuminated images. However, real-time application of structured illumination microscopy (SIM) has generally been limited due to the computational overhead needed to generate super-resolution images. Here, we have developed a real-time SIM system that incorporates graphic processing unit (GPU) based in-line parallel processing of raw/differentially illuminated images. By using GPU processing, the system has achieved a 90-fold increase in processing speed compared to performing equivalent operations on a multiprocessor computer--the total throughput of the system is limited by data acquisition speed, but not by image processing. Overall, more than 350 raw images (16-bit depth, 512 × 512 pixels) can be processed per second, resulting in a maximum frame rate of 39 super-resolution images per second. This ultrafast processing capability is used to provide immediate feedback of super-resolution images for real-time display. These developments are increasing the potential for sophisticated super-resolution imaging applications.

Metal-dielectric composites for beam splitting and far-field deep sub-wavelength resolution for visible wavelengths

We report beam splitting in a metamaterial composed of a silver-alumina composite covered by a layer of chromium containing one slit. By simulating distributions of energy flow in the metamaterial for H-polarized waves, we find that the beam splitting occurs when the width of the slit is shorter than the wavelength, which is conducive to making a beam splitter in sub-wavelength photonic devices. We also find that the metamaterial possesses deep sub-wavelength resolution capabilities in the far field when there are two slits and the central silver layer is at least 36 nm in thickness, which has potential applications in superresolution imaging.

Superresolution Imaging using Single-Molecule Localization

Superresolution imaging is a rapidly emerging new field of microscopy that dramatically improves the spatial resolution of light microscopy by over an order of magnitude (approximately 10-20-nm resolution), allowing biological processes to be described at the molecular scale. Here, we discuss a form of superresolution microscopy based on the controlled activation and sampling of sparse subsets of photoconvertible fluorescent molecules. In this single-molecule-based imaging approach, a wide variety of probes have proved valuable, ranging from genetically encodable photoactivatable fluorescent proteins to photoswitchable cyanine dyes. These have been used in diverse applications of superresolution imaging: from three-dimensional, multicolor molecule localization to tracking of nanometric structures and molecules in living cells. Single-molecule-based superresolution imaging thus offers exciting possibilities for obtaining molecular-scale information on biological events occurring at variable timescales.

Superresolution imaging: Theory, Algorithms and Applications

The International Conference on Superresolution Imaging was held from 29 August to 31 August, 2005 at the University of Hong Kong. The conference had two major objectives: (1) to improve the dialogue and collaboration between mathematicians, engineers and computer scientists working in superresolution imaging, and (2) to stimulate new theoretical research and emerging applications in superresolution imaging. This proceeding contain six papers from invited speakers of the conference. The contributions cover different aspects in the superresolution imaging research. The first article, “Region-based Super-resolution for Compression”, addresses the problem of synthesizing a high-resolution image from a compressed low-resolution video sequence using region-based information. The second article, “Super-resolution Reconstruction in a Computational Compound-eye Imaging System”, discusses a novel and effective multiple-design parameter approach for high-resolution image reconstruction. The third article, “Example-based Single Image Super-resolution: A Global MAP Approach with Outlier Rejection” proposes an efficient scheme for using image examples as driving a powerful regularization scheme for superresolution imaging. The fourth article, “Super-resolution: Should We Process Locally or Globally?” studies the usefulness of different local and global learning-based, single-frame image super-resolution reconstruction techniques in handling deblurring, denoising and alias removal. The fifth article, “SuperResolutionReconstruction based onWavelet Estimation”, uses linear interpolation to build up an image reconstruction algorithm to obtain the relationship between the detail coefficients in wavelet subbands and the set of low-resolution images. The sixth article, “An Efficient Algorithm for Superresolution in Medium Field Imaging”, applies the preconditioned conjugate

Single-shot subpixel response measurement with an aperture array pixel mask

We first point out that the subpixel response function is another kernel function in digital imaging. Then we show that the subpixel response function of CMOS imaging sensor pixels can be measured with an aperture array pixel mask in a single-shot image capture. Our technique permits high-resolution subpixel response function measurement of imaging pixels for superresolution imaging applications.

Generalized interpolation and its application in super-resolution imaging

In this paper, we present a generalized interpolation scheme for image expansion and generation of super-resolution images. This is done by decomposing the image into appropriate subspaces, carrying out interpolation in individual subspaces and subsequently transforming the interpolated values back to the image domain. Various optical and structural properties of the image, such as 3-D shape of an object, regional homogeneity, local variations in scene reflectivity, etc., can be better preserved during the interpolation process. The motivation for doing so has also been explained theoretically. The generalized interpolation scheme is also shown to be useful in perceptually based high-resolution representation of images where interpolation is done on individual groups as per the perceptual necessity. Further, this scheme is also applied to generation of high-resolution transparencies from low resolution transparencies.