Present optical nanoscopy techniques use a complex microscope for imaging and a simple glass slide to hold the sample. Here, we demonstrate the inverse: the use of a complex, but mass-producible ...optical chip, which hosts the sample and provides a waveguide for the illumination source, and a standard low-cost microscope to acquire super-resolved images via two different approaches. Waveguides composed of a material with high refractive-index contrast provide a strong evanescent field that is used for single-molecule switching and fluorescence excitation, thus enabling chip-based single-molecule localization microscopy. Additionally, multimode interference patterns induce spatial fluorescence intensity variations that enable fluctuation-based super-resolution imaging. As chip-based nanoscopy separates the illumination and detection light paths, total-internal-reflection fluorescence excitation is possible over a large field of view, with up to 0.5 mm × 0.5 mm being demonstrated. Using multicolour chip-based nanoscopy, we visualize fenestrations in liver sinusoidal endothelial cells.
An approximate two-dimensional analytical model is proposed for description of a stationary monochromatic field arising at the Gaussian light beam refraction into a transparent or weakly absorbing ...homogeneous medium. Its formulae describe the spatial structure of a refracted field in a wide range of variation of incidence angles, when this field is characterized by free propagation, total internal reflection, or exponential decay. The model is based on the asymptotic calculation of the Fourier integral, taking into account possible diffraction effects of the first and the second order.
•Analytical model is proposed for the Gaussian light beam refraction.•Model describes approximately the spatial pattern of the refracted field.•Model is applicable in a wide range of variation of beam incidence angles.•This range coves free propagation, total internal reflection and exponential decay.
The concept of a nonlocal elastic metasurface has been recently proposed and experimentally demonstrated in Zhu et al. (2020). When implemented in the form of a total-internal-reflection (TIR) ...interface, the metasurface can act as an elastic wave barrier that is impenetrable to deep subwavelength waves over an exceptionally wide frequency band. The underlying physical mechanism capable of delivering this broadband subwavelength performance relies on an intentionally nonlocal design that leverages long-range connections between the units forming the fundamental supercell. This paper explores the design and application of a nonlocal TIR metasurface to achieve broadband passive vibration isolation in a structural assembly made of multiple dissimilar elastic waveguides. The specific structural system comprises shell, plate, and beam waveguides, and can be seen as a prototypical structure emulating mechanical assemblies of practical interest for many engineering applications. The study also reports the results of an experimental investigation that confirms the significant vibration isolation capabilities afforded by the embedded nonlocal TIR metasurface. We report these results are particularly remarkable because they show that the performance of the nonlocal metasurface is preserved when applied to a complex structural assembly and under non-ideal incidence conditions of the incoming wave, hence significantly extending the validity of the results presented in Zhu et al. (2020). Results also confirm that, under proper conditions, the original concept of a planar metasurface can be morphed into a curved interface while still preserving full wave control capabilities.
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•Sandwich-type electrochemical immunosensor was developed based on Ag/MoS2@Fe3O4.•The analogous ELISA method was applied for detecting CEA.•TIRF was firstly employed to fabricate the ...immunosensor.•The immunosensor displayed low detection limit of 0.03 pg/mL for CEA.
In this work, an ultrasensitive electrochemical immunosensor was developed for detecting carcinoembryonic antigen (CEA) based on Ag/MoS2@Fe3O4 and an analogous enzyme linked immunosorbent assay (ELISA) method. The fabrication process was conducted by using 96-well microplate and the detection process was executed on magnetic glassy carbon electrode (MGCE), which was named analogous ELISA method. The technique of total internal reflection fluorescence (TIRF) was firstly employed to verify the feasibility of the proposed method. A sandwich-type strategy was applied for the fabrication of the immunosensor and Ag/MoS2@Fe3O4 was used as label. Simultaneously, Ag nanoparticles (Ag NPs) were applied for modifying the MGCE as sensing platform due to its excellent electroconductivity. Ag/MoS2@Fe3O4 could firmly attached on the surface of MGCE thanks to the magnetic property of Fe3O4. Differential pulse voltammetry (DPV) was applied for the detection of CEA and electrochemical impedance spectroscopy (EIS) confirmed the successful fabrication of the immunosensor. Under optimal experimental conditions, a linear response was achieved in the range of 0.0001–20 ng/mL with a low detection limit of 0.03 pg/mL. Furthermore, the proposed immunosensor exhibited good stability, excellent selectivity and fine reproducibility. This proposed strategy provides a new thought and a potential approach for clinical diagnosis of other tumor markers.
Attenuated Total Reflection (ATR) Fourier Transform Infrared (FTIR) spectroscopy is a label-free, non-destructive analytical technique that can be used extensively to study a wide variety of ...different molecules in a range of different conditions. The aim of this review is to discuss and highlight the recent advances in the applications of ATR FTIR spectroscopic imaging to proteins. It briefly covers the basic principles of ATR FTIR spectroscopy and ATR FTIR spectroscopic imaging as well as their advantages to the study of proteins compared to other techniques and other forms of FTIR spectroscopy. It will then go on to examine the advances that have been made within the field over the last several years, particularly the use of ATR FTIR spectroscopy for the understanding and development of protein interaction with surfaces. Additionally, the growing potential of Surface Enhanced Infrared Spectroscopy (SEIRAS) within this area of applications will be discussed. The review includes the applications of ATR FTIR imaging to protein crystallisation and for high-throughput studies, highlighting the future potential of the technology within the field of protein structural studies and beyond.
•Highlighting recent applications of ATR FTIR spectroscopy to protein analysis.•Presenting ATR FTIR spectroscopic imaging as a powerful tool to study proteins.•Applications of FTIR imaging to high-throughput protein studies are reviewed.•Potential of Surface Enhanced Infrared spectroscopy for protein analysis presented.
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Structural color materials have tremendous applications and been extensively investigated in the past decades. Most of them involve either nanoscale periodic photonic crystal ...structure or film interference mechanisms. Herein, we report a novel retroreflective structural color film (RSCF) based on a combined effect of interference and total internal reflection (TIR). The RSCF is consisted of a microscale polymer hemisphere array formed on the same polymer matrix. When exposed to white light illumination, the non-hemisphere-side of the film exhibits non-iridescent color under coaxial illumination and observation, and iridescent color under noncoaxial illumination and observation. In contrary, the hemisphere-side of the film does not show any colors regardless of coaxial or noncoaxial illumination and observation. Furthermore, an elastic polyurethane-based RSCF can exhibit dynamically and reversibly changing colors during uniaxial tensile/compressive deformation.
Nonlocal elastic metasurfaces Zhu, Hongfei; Patnaik, Sansit; Walsh, Timothy F. ...
Proceedings of the National Academy of Sciences - PNAS,
10/2020, Volume:
117, Issue:
42
Journal Article
Peer reviewed
Open access
While elastic metasurfaces offer a remarkable and very effective approach to the subwavelength control of stress waves, their use in practical applications is severely hindered by intrinsically ...narrow band performance. In applications to electromagnetic and photonic metamaterials, some success in extending the operating dynamic range was obtained by using nonlocality. However, while electronic properties in natural materials can show significant nonlocal effects, even at the macroscales, in mechanics, nonlocality is a higher-order effect that becomes appreciable only at the microscales. This study introduces the concept of intentional nonlocality as a fundamental mechanism to design passive elastic metasurfaces capable of an exceptionally broadband operating range. The nonlocal behavior is achieved by exploiting nonlocal forces, conceptually akin to long-range interactions in nonlocal material microstructures, between subsets of resonant unit cells forming the metasurface. These long-range forces are obtained via carefully crafted flexible elements, whose specific geometry and local dynamics are designed to create remarkably complex transfer functions between multiple units. The resulting nonlocal coupling forces enable achieving phase-gradient profiles that are functions of the wavenumber of the incident wave. The identification of relevant design parameters and the assessment of their impact on performance are explored via a combination of semianalytical and numerical models. The nonlocal metasurface concept is tested, both numerically and experimentally, by embedding a total-internal-reflection design in a thin-plate waveguide. Results confirm the feasibility of the intentionally nonlocal design concept and its ability to achieve a fully passive and broadband wave control
An advanced light scattering model for Total Internal Reflection Microscopy (TIRM) is presented. The model considers the specific TIRM geometry and deals with the scattering by an axisymmetric ...particle of arbitrary orientation placed in a stratified medium and the imaging of the scattered field. The scattered field is computed by truncating the scattered and internal field expansions and by using spherical and plane wave expansions for the free-space dyadic Green’s function. While the first expansion is valid outside a sphere enclosing the particle, the second one is valid outside the tangent planes bounding the particle from above and below. We demonstrate that in both cases, the results are the same, and thus, that the restrictive condition according to which the interface should not intersect the particle’s circumscribed sphere is not relevant. The image of the scattered field is computed by using the Debye diffraction integral and fast Fourier transform, while for a better reconstruction of the particle orientation, an image processing step consisting in a contour extraction and ellipse fitting is considered. The numerical simulations dealing with scattering by a prolate spheroid provide evidence of the remarkably sensitivity of the geometric parameters of the image ellipse to the particle orientation angles, as well as, of the integral response of the detector to the distance between the particle and the interface.
•Novel TIRM model for arbitrary particle orientation in stratified media.•High sensitivity of image ellipse in TIRM to particle orientation in simulations.•Contour extraction and ellipse fitting improve particle orientation accuracy.•Comprehensive scattering model for arbitrary particle orientation in stratified media.
The establishment of apicobasal or planar cell polarity involves many events that occur at or near the plasma membrane including focal adhesion dynamics, endocytosis, exocytosis, and cytoskeletal ...reorganization. It is desirable to visualize these events without interference from other regions deeper within the cell. Total internal reflection fluorescence (TIRF) microscopy utilizes an elegant optical sectioning approach to visualize fluorophores near the sample-coverslip interface. TIRF provides high-contrast fluorescence images with limited background and virtually no out-of-focus light, ideal for visualizing and tracking dynamics near the plasma membrane. In this chapter, we present a general experimental and analysis TIRF pipeline for studying cell surface receptor endocytosis. The approach presented can be easily applied to study other dynamic biological processes at or near the plasma membrane using TIRF microscopy.
The objective of this critical review is to provide an overview of how emerging bioanalytical techniques are expanding our understanding of the complex physicochemical nature of virus interactions ...with host cell surfaces. Herein, selected model viruses representing both non-enveloped (simian virus 40 and human norovirus) and enveloped (influenza A virus, human herpes simplex virus, and human immunodeficiency virus type 1) viruses are highlighted. The technologies covered utilize a wide range of cell membrane mimics, from supported lipid bilayers (SLBs) containing a single purified host membrane component to SLBs derived from the plasma membrane of a target cell, which can be compared with live-cell experiments to better understand the role of individual interaction pairs in virus attachment and entry. These platforms are used to quantify binding strengths, residence times, diffusion characteristics, and binding kinetics down to the single virus particle and single receptor, and even to provide assessments of multivalent interactions. The technologies covered herein are surface plasmon resonance (SPR), quartz crystal microbalance with dissipation (QCM-D), dynamic force spectroscopy (DFS), total internal reflection fluorescence (TIRF) microscopy combined with equilibrium fluctuation analysis (EFA) and single particle tracking (SPT), and finally confocal microscopy using multi-labeling techniques to visualize entry of individual virus particles in live cells. Considering the growing scientific and societal needs for untangling, and interfering with, the complex mechanisms of virus binding and entry, we hope that this review will stimulate the community to implement these emerging tools and strategies in conjunction with more traditional methods. The gained knowledge will not only contribute to a better understanding of the virus biology, but may also facilitate the design of effective inhibitors to block virus entry.
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