Seeing Elastin: A Near-Infrared Zwitterionic Fluorescent Probe for In Vivo Elastin Imaging

Elastic fibers are present in a variety of tissues and are responsible for their resilience. Until now, no optical contrast agent in the near-infrared (NIR) wavelength range of 700-900 nm has been reported for the imaging of elastic fibers. Here, we report the discovery of a NIR zwitterionic elastin probe ElaNIR (elastin NIR) through fluorescent-image-based screening. The probe was successfully applied for in vitro, ex vivo, and in vivo imaging by various imaging modalities. Age-related elastin differences shown by in vivo fluorescent and photoacoustic imaging indicated that ElaNIR can be a potentially convenient tool for uncovering changes of elastin in live models.11Ysciescopu

Application of coherent light in measuring optical property and blood perfusion

Coherent light source is widely utilized in biomedical study. In this thesis, the coherent light is mainly applied for measuring the optical property and in vivo blood perfusion. An interesting physiological phenomenon, coherent backscattering (CBS) is introduced. People have found many biomedical applications of CBS related technologies. Through our study, the illumination beam size on the sample is shown to affect the CBS phenomenon significantly when its diameter is small. The coherent light source is highly auto-correlated in time domain. The electric field temporal autocorrelation function of the light will decay faster when the photons are collided with moving particles, such as the in vivo red blood cells. This is the foundation of many optical modalities for blood perfusion measurement, such as diffuse correlation spectroscopy (DCS). A software correlator based DCS system is introduced in this thesis. We validate its performance by a flow-controlled phantom. Interesting in vivo data is also demonstrated. To simplify DCS system, a novel optical modality for deep tissue blood perfusion measurement, diffuse speckle contrast analysis (DSCA) is introduced for the first time by the author. DSCA brings several advantages in instrumentation and data processing, which may find significant clinical applications. Relative validation results against our home made DCS system are demonstrated. There are already several existing optical modalities for blood perfusion measurement in the market, such as laser Doppler Flowmetry and laser speckle contrast imaging. In this thesis, the working principles of these existing optical blood perfusion monitoring technologies are studied and compared in details. The relationship and comparison among these optical technologies are discussed in details. In summary, this dissertation introduces some biomedical applications of the coherent light, especially in optical property measurement and blood perfusion mornitoring.Doctor of Philosophy (SCBE

Deep tissue flowmetry based on diffuse speckle contrast analysis

Diffuse correlation spectroscopy (DCS) is an emerging modality for noninvasive deep tissue blood flow monitoring that is becoming increasingly popular; it conducts an autocorrelation analysis of fast fluctuating photon count signals from a single speckle. In this Letter, we show that the same level of deep tissue flow information can be obtained from a much simpler analysis on the spatial distribution of the speckles that is obtained by a CCD camera, which we named diffuse speckle contrast analysis (DSCA). Both the flow phantom experiment and in vivo cuff occlusion data are presented. DSCA can be considered a new optical modality that combines DCS and laser speckle contrast imaging (LSCI), which exploits simple instrumentation and analysis and yet is sensitive to deep tissue flow.Published versio

Multi-channel deep tissue flowmetry based on temporal diffuse speckle contrast analysis

Recently, diffuse speckle contrast analysis (DSCA) was introduced as a competent modality for deep tissue blood flow measurement, where the speckle contrast is calculated over spatial domain on the CCD image of diffuse reflectance. In this paper, we introduce time-domain DSCA where temporal statistics are used for speckle contrast calculation and results in the same deep tissue flow measurement. This new modality is especially suitable for multi-channel real-time flowmetry, and we demonstrate its performance on human arm during cuff occlusion test. Independent component analysis (ICA) study on multi-channel data shows promising results about underlying physiology.Published versio

Coherent backscattering cone shape depends on the beam size

Coherent backscattering (CBS) is a beautiful physical phenomenon that takes place in a highly scattering medium, which has potential application in noninvasive optical property measurement. The current model that explains the CBS cone shape, however, assumes the incoming beam diameter is infinitely large compared to the transport length. In this paper, we evaluate the effect of a finite scalar light illumination area on the CBS cone, both theoretically and experimentally. The quantitative relationship between laser beam size and the CBS cone shape is established by using two different finite beam models (uniform top hat and Gaussian distribution). A series of experimental data with varying beam diameters is obtained for comparison with the theory. Our study shows the CBS cone shape begins to show distortion when beam size becomes submillimeter, and this effect should not be ignored in general. In biological tissue where a normal large beam CBS cone is too narrow for detection, this small beam CBS may be more advantageous for more accurate and higher resolution tissue characterization.Published versio

Applications of Optical Fiber in Label-Free Biosensors and Bioimaging: A Review

Biosensing and bioimaging are essential in understanding biological and pathological processes in a living system, for example, in detecting and understanding certain diseases. Optical fiber has made remarkable contributions to the biosensing and bioimaging areas due to its unique advantages of compact size, immunity to electromagnetic interference, biocompatibility, fast response, etc. This review paper will present an overview of seven common types of optical fiber biosensors and optical fiber-based ultrasound detection in photoacoustic imaging (PAI) and the applications of these technologies in biosensing and bioimaging areas. Of course, there are many types of optical fiber biosensors. Still, this paper will review the most common ones: optical fiber grating, surface plasmon resonance, Sagnac interferometer, Mach–Zehnder interferometer, Michelson interferometer, Fabry–Perot Interferometer, lossy mode resonance, and surface-enhanced Raman scattering. Furthermore, different optical fiber techniques for detecting ultrasound in PAI are summarized. Finally, the main challenges and future development direction are briefly discussed

Chapter 5. Deep Tissue Hemodynamic Monitoring Using Diffuse Optical Probes

Olivo Malini(Editor)Dinish U. S.(Editor)Fluorescence Lifetime Spectroscopy and Imaging Techniques in Medical Applications -- Translational Photoacoustic Microscopy -- Advances in Optoacoustic Imaging: From Benchside to Clinic -- Raman Spectroscopy Techniques: Developments and Applications in Translational Medicine -- Deep Tissue Hemodynamic Monitoring Using Diffuse Optical Probes -- High Resolution Optical Coherence Tomography for Bio-imaging -- Handheld Probe-based Dual Mode Ultrasound/Photoacoustics for Biomedical Imaging -- Plasmonic Exosome Biosensors for Medical Diagnostics -- Nanoparticle-enabled Endoscopy: Extending the Frontiers of Diagnosis and Treatment -- Monitoring Free Gas In-situ for Medical Diagnostics Using Laser Spectroscopic Techniques -- Next Frontier in Optical Imaging Techniques for Laparoscopic Surgery: An Industry Perspective

Optical methods for blood perfusion measurement-theoretical comparison among four different modalities

Blood perfusion in human tissue can be measured in vivo by means of various optical methods, which seem to be very different from one another. The most prominent examples of them are laser Doppler flowmetry, laser speckle contrast imaging, diffuse correlation spectroscopy, and the most recently developed diffuse speckle contrast analysis. In this paper, we claim that these four seemingly different modalities are examining different aspects of the same entity - the temporal autocorrelation function of scattered photons. We will show how the observables in each modality can be theoretically derived from the temporal autocorrelation function, and will discuss the merits and drawbacks of each modality in its practical use. © 2015 Optical Society of America.1

Metasurfaces for biomedical applications : imaging and sensing from a nanophotonics perspective

The research is supported by the Agency of Science, Technology and Research (A*STAR), under its Industry alignment fund prepositioning program, Award H19H6a0025. K. D. thanks the UK Engineering and Physical Sciences Research Council through grant EP/P030017/1.Metasurface is a recently developed nanophotonics concept to manipulate the properties of light by replacing conventional bulky optical components with ultrathin (more than 104 times thinner) flat optical components. Since the first demonstration of metasurfaces in 2011, they have attracted tremendous interest in the consumer optics and electronics industries. Recently, metasurface-empowered novel bioimaging and biosensing tools have emerged and been reported. Given the recent advances in metasurfaces in biomedical engineering, this review article covers the state of the art for this technology and provides a comprehensive interdisciplinary perspective on this field. The topics that we have covered include metasurfaces for chiral imaging, endoscopic optical coherence tomography, fluorescent imaging, super-resolution imaging, magnetic resonance imaging, quantitative phase imaging, sensing of antibodies, proteins, DNAs, cells, and cancer biomarkers. Future directions are discussed in twofold: Application-specific biomedical metasurfaces and bioinspired metasurface devices. Perspectives on challenges and opportunities of metasurfaces, biophotonics, and translational biomedical devices are also provided. The objective of this review article is to inform and stimulate interdisciplinary research: Firstly, by introducing the metasurface concept to the biomedical community; and secondly by assisting the metasurface community to understand the needs and realize the opportunities in the medical fields. In addition, this article provides two knowledge boxes describing the design process of a metasurface lens and the performance matrix of a biosensor, which serve as a "crash-course"introduction to those new to both fields.Publisher PDFPeer reviewe