Design and Demonstration of a Microbiaxial Optomechanical Device for Multiscale Characterization of Soft Biological Tissues with Two-Photon Microscopy

AbstractThe biomechanical response of tissues serves as a valuable marker in the prediction of disease and in understanding the related behavior of the body under various disease and age states. Alterations in the macroscopic biomechanical response of diseased tissues are well documented; however, a thorough understanding of the microstructural events that lead to these changes is poorly understood. In this article we introduce a novel microbiaxial optomechanical device that allows two-photon imaging techniques to be coupled with macromechanical stimulation in hydrated planar tissue specimens. This allows that the mechanical response of the microstructure can be quantified and related to the macroscopic response of the same tissue sample. This occurs without the need to fix tissue in strain states that could introduce a change in the microstructural configuration. We demonstrate the passive realignment of fibrous proteins under various types of loading, which demonstrates the ability of tissue microstructure to reinforce itself in periods of high stress. In addition, the collagen and elastin response of tissue during viscoelastic behavior is reported showing interstitial fluid movement and fiber realignment potentially responsible for the temporal behavior. We also demonstrate that nonhomogeneities in fiber strain exist over biaxial regions of assumed homogeneity.

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Strain-Rate Sensitive Constitutive Modeling of Anisotropic Visco-Hyperelastic Materials

Volume 8: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2012-88608 ◽

2012 ◽

Author(s):

Sahand Ahsanizadeh ◽

LePing Li

Keyword(s):

Strain Rate ◽

Evolution Equations ◽

Mechanical Response ◽

Viscoelastic Behavior ◽

Biological Tissues ◽

Internal Variables ◽

Current Configuration ◽

Hyperelastic Materials ◽

History Of ◽

Viscoelastic Constitutive Model

Integral-based formulations of viscoelasticity have been widely used to describe the mechanical behavior of soft biological tissues and polymers. However, it is suggested that they are not suitable to be used under high strain rates. On the other hand, strain-rate sensitive models with an explicit dependence on the strain-rate have been developed for a certain class of materials. They predict the viscoelastic behavior during ramp loading more accurately while fail to account for the relaxation response. In order to overcome these drawbacks, a viscoelastic constitutive model has been proposed in this study based on the concept of internal variables. While the behavior of elastic materials is uniquely determined by the current state of deformation or external variables, the mechanical response of inelastic materials are regulated also by internal variables. The internal variables are associated with the dissipative mechanisms in the material and along with the evolution equations introduce the effect of history of the deformation to the current configuration. The current study employs short-term and long-term internal variables to account for the viscoelastic response during loading and relaxation respectively.

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Synthesis and Characterization of GdVO4:Nd Near-Infrared Phosphors for Optical Time-Gated In Vivo Imaging

Materials ◽

10.3390/ma13163564 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3564

Author(s):

Ben Nimmegeers ◽

Ewoud Cosaert ◽

Tecla Carbonati ◽

Daniela Meroni ◽

Dirk Poelman

Keyword(s):

Decay Time ◽

Near Infrared ◽

Imaging Techniques ◽

Medical Personnel ◽

Biological Tissues ◽

The Body ◽

Transparency Window ◽

Optical Time ◽

Gated Imaging

Many medical imaging techniques use some form of ionizing radiation. This radiation is not only potentially harmful for the patient, but also for the medical personnel. An alternative imaging technique uses near-infrared (NIR) emitting luminescent particles as tracers. If the luminescent probes are excited inside the body, autofluorescence from the biological tissues is also induced. This problem can be circumvented by using time-gated imaging. Hereby, the light collection only starts when the fluorescence of the tissue has decayed. This requires particles showing both excitation and emission in the near-infrared and a long decay time so that they can be used in time-gated imaging. In this work, Nd-doped GdVO4 NIR emitting particles were prepared using solid state reaction. Particles could be efficiently excited at 808 nm, right in the first transparency window for biological tissues, emitted in the second transparency window at around 1064 nm, and showed a decay time of the order of 70 μs, sufficiently long for time-gating. By using a Gd-containing host, these particles could be ideally suited for multimodal optical/magnetic imaging after size reduction and surface functionalization.

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SEM/FESEM imaging of lamellar structures in melt extruded polyethylene films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130341 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1142-1143

Author(s):

R.T. Chen ◽

M.G. Jamieson ◽

R. Callahan

Keyword(s):

Imaging Techniques ◽

Membrane Surface ◽

High Stress ◽

Extrusion Direction ◽

Polymeric Membranes ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Crystalline Polymers ◽

Lamellar Structures ◽

Resolution Imaging

“Row lamellar” structures have previously been observed when highly crystalline polymers are melt-extruded and recrystallized under high stress. With annealing to perfect the stacked lamellar superstructure and subsequent stretching in the machine (extrusion) direction, slit-like micropores form between the stacked lamellae. This process has been adopted to produce polymeric membranes on a commercial scale with controlled microporous structures. In order to produce the desired pore morphology, row lamellar structures must be established in the membrane precursors, i.e., as-extruded and annealed polymer films or hollow fibers. Due to the lack of pronounced surface topography, the lamellar structures have typically been investigated by replica-TEM, an indirect and time consuming procedure. Recently, with the availability of high resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM), the microporous structures on the membrane surface as well as lamellar structures in the precursors can be directly examined.The materials investigated are Celgard® polyethylene (PE) flat sheet membranes and their film precursors, both as-extruded and annealed, made at different extrusion rates (E.R.).

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Mathematical Modeling and Numerical Simulation of Atherosclerosis Based on a Novel Surgeon’s View

Archives of Computational Methods in Engineering ◽

10.1007/s11831-021-09623-5 ◽

2021 ◽

Author(s):

Meisam Soleimani ◽

Axel Haverich ◽

Peter Wriggers

Keyword(s):

Mathematical Modeling ◽

Inflammatory Response ◽

Phase Field ◽

Mechanical Response ◽

Type Equation ◽

The Body ◽

Vasa Vasorum ◽

Diffusion Reaction ◽

Dust Particles ◽

Driving Mechanism

AbstractThis paper deals with the mathematical modeling of atherosclerosis based on a novel hypothesis proposed by a surgeon, Prof. Dr. Axel Haverich (Circulation 135(3):205–207, 2017). Atherosclerosis is referred as the thickening of the artery walls. Currently, there are two schools of thoughts for explaining the root of such phenomenon: thickening due to substance deposition and thickening as a result of inflammatory overgrowth. The hypothesis favored here is the second paradigm stating that the atherosclerosis is nothing else than the inflammatory response of of the wall tissues as a result of disruption in wall nourishment. It is known that a network of capillaries called vasa vasorum (VV) accounts for the nourishment of the wall in addition to the natural diffusion of nutrient from the blood passing through the lumen. Disruption of nutrient flow to the wall tissues may take place due to the occlusion of vasa vasorums with viruses, bacteria and very fine dust particles such as air pollutants referred to as PM 2.5. They can enter the body through the respiratory system at the first place and then reach the circulatory system. Hence in the new hypothesis, the root of atherosclerotic vessel is perceived as the malfunction of microvessels that nourish the vessel. A large number of clinical observation support this hypothesis. Recently and highly related to this work, and after the COVID-19 pandemic, one of the most prevalent disease in the lungs are attributed to the atherosclerotic pulmonary arteries, see Boyle and Haverich (Eur J Cardio Thorac Surg 58(6):1109–1110, 2020). In this work, a general framework is developed based on a multiphysics mathematical model to capture the wall deformation, nutrient availability and the inflammatory response. For the mechanical response an anisotropic constitutive relation is invoked in order to account for the presence of collagen fibers in the artery wall. A diffusion–reaction equation governs the transport of the nutrient within the wall. The inflammation (overgrowth) is described using a phase-field type equation with a double well potential which captures a sharp interface between two regions of the tissues, namely the healthy and the overgrowing part. The kinematics of the growth is treated by classical multiplicative decomposition of the gradient deformation. The inflammation is represented by means of a phase-field variable. A novel driving mechanism for the phase field is proposed for modeling the progression of the pathology. The model is 3D and fully based on the continuum description of the problem. The numerical implementation is carried out using FEM. Predictions of the model are compared with the clinical observations. The versatility and applicability of the model and the numerical tool allow.

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Optical Microscopy and the Extracellular Matrix Structure: A Review

Cells ◽

10.3390/cells10071760 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1760

Author(s):

Joshua J. A. Poole ◽

Leila B. Mostaço-Guidolin

Keyword(s):

Extracellular Matrix ◽

Confocal Microscopy ◽

Laser Scanning ◽

Biological Tissues ◽

The Body ◽

Stimulated Emission ◽

Substantial Part ◽

Fluorescence Lifetime Imaging ◽

Structured Illumination ◽

Structured Illumination Microscopy

Biological tissues are not uniquely composed of cells. A substantial part of their volume is extracellular space, which is primarily filled by an intricate network of macromolecules constituting the extracellular matrix (ECM). The ECM serves as the scaffolding for tissues and organs throughout the body, playing an essential role in their structural and functional integrity. Understanding the intimate interaction between the cells and their structural microenvironment is central to our understanding of the factors driving the formation of normal versus remodelled tissue, including the processes involved in chronic fibrotic diseases. The visualization of the ECM is a key factor to track such changes successfully. This review is focused on presenting several optical imaging microscopy modalities used to characterize different ECM components. In this review, we describe and provide examples of applications of a vast gamut of microscopy techniques, such as widefield fluorescence, total internal reflection fluorescence, laser scanning confocal microscopy, multipoint/slit confocal microscopy, two-photon excited fluorescence (TPEF), second and third harmonic generation (SHG, THG), coherent anti-Stokes Raman scattering (CARS), fluorescence lifetime imaging microscopy (FLIM), structured illumination microscopy (SIM), stimulated emission depletion microscopy (STED), ground-state depletion microscopy (GSD), and photoactivated localization microscopy (PALM/fPALM), as well as their main advantages, limitations.

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Multiphoton Microscopy for Ophthalmic Imaging

Journal of Ophthalmology ◽

10.1155/2011/870879 ◽

2011 ◽

Vol 2011 ◽

pp. 1-11 ◽

Cited By ~ 28

Author(s):

Emily A. Gibson ◽

Omid Masihzadeh ◽

Tim C. Lei ◽

David A. Ammar ◽

Malik Y. Kahook

Keyword(s):

Harmonic Generation ◽

Second Harmonic ◽

Imaging Techniques ◽

Multiphoton Microscopy ◽

Tissue Imaging ◽

Third Harmonic ◽

Two Photon ◽

Disease Mechanisms ◽

Ophthalmic Imaging ◽

Anti Stokes

We review multiphoton microscopy (MPM) including two-photon autofluorescence (2PAF), second harmonic generation (SHG), third harmonic generation (THG), fluorescence lifetime (FLIM), and coherent anti-Stokes Raman Scattering (CARS) with relevance to clinical applications in ophthalmology. The different imaging modalities are discussed highlighting the particular strength that each has for functional tissue imaging. MPM is compared with current clinical ophthalmological imaging techniques such as reflectance confocal microscopy, optical coherence tomography, and fluorescence imaging. In addition, we discuss the future prospects for MPM in disease detection and clinical monitoring of disease progression, understanding fundamental disease mechanisms, and real-time monitoring of drug delivery.

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Role of smooth muscle activation in the static and dynamic mechanical characterization of human aortas

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2117232119 ◽

2022 ◽

Vol 119 (3) ◽

pp. e2117232119

Author(s):

Giulio Franchini ◽

Ivan D. Breslavsky ◽

Francesco Giovanniello ◽

Ali Kassab ◽

Gerhard A. Holzapfel ◽

...

Keyword(s):

Experimental Data ◽

Smooth Muscle ◽

Muscle Activation ◽

Mechanical Response ◽

Mechanical Characterization ◽

Viscoelastic Behavior ◽

Material Model ◽

Suitable Material ◽

Dynamic Mechanical

Experimental data and a suitable material model for human aortas with smooth muscle activation are not available in the literature despite the need for developing advanced grafts; the present study closes this gap. Mechanical characterization of human descending thoracic aortas was performed with and without vascular smooth muscle (VSM) activation. Specimens were taken from 13 heart-beating donors. The aortic segments were cooled in Belzer UW solution during transport and tested within a few hours after explantation. VSM activation was achieved through the use of potassium depolarization and noradrenaline as vasoactive agents. In addition to isometric activation experiments, the quasistatic passive and active stress–strain curves were obtained for circumferential and longitudinal strips of the aortic material. This characterization made it possible to create an original mechanical model of the active aortic material that accurately fits the experimental data. The dynamic mechanical characterization was executed using cyclic strain at different frequencies of physiological interest. An initial prestretch, which corresponded to the physiological conditions, was applied before cyclic loading. Dynamic tests made it possible to identify the differences in the viscoelastic behavior of the passive and active tissue. This work illustrates the importance of VSM activation for the static and dynamic mechanical response of human aortas. Most importantly, this study provides material data and a material model for the development of a future generation of active aortic grafts that mimic natural behavior and help regulate blood pressure.

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External and Internal Loads in Sports Science: Time to Rethink?

10.20944/preprints202111.0207.v1 ◽

2021 ◽

Author(s):

Bernardo Ide ◽

Amanda Silvatti ◽

Craig Staunton ◽

Moacir Marocolo ◽

Dustin Oranchuk ◽

...

Keyword(s):

Perceived Exertion ◽

Biological Tissues ◽

The Body ◽

Rating Of Perceived Exertion ◽

Measuring System ◽

Internal Load ◽

Sports Science ◽

System Of Units ◽

Time Distance ◽

Displacement Speed

The International System of Units (SI) was adopted in 1960 as a universal measuring system to be used for all areas of science. Sports Science papers have shown lots of inaccurate and inappropriate terms for quantification of athletes’ performance and the psychobiological responses to exercise (e.g., internal load). In biomechanics, external and internal loads are forces acting externally and internally, inducing stress and strain in the biological tissues. Therefore, the current review present simple proposals to correct the inappropriate terms: 1) do not use the term external load when referring to the assessment of exercise time, distance, displacement, speed, velocity, acceleration, torque, work, power, impulse, etc.; 2) do not use the term internal load when referring to the assessment of psychobiological stress markers (i.e., session rating of perceived exertion, heart rate, blood lactate, oxygen consumption, etc.); 3) do not use the term impulse when expressing other calculus than integrating force with respect to time, and neither strain, when expressing other phenomena than the body deformation. Instead, the term exercise intensity is universal and can be used to describe all forms of exercise. Finally, duration should precisely be described according to physical quantities (e.g., time, distance, displacement, speed, velocity, acceleration, force, torque, work, power, impulse, etc.) and the units accomplish by use of the SI. These simple quantifications can be performed for the exercises, sessions, microcycles, mesocycles and macrocycles of the athletes. Such standardization will provide a consistent and clear communication among sports scientists and all areas of science.

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The creation and trial of a serious game to support teaching and learning of professional psychology competencies in postgraduate programs

Australasian Journal of Educational Technology ◽

10.14742/ajet.4237 ◽

2019 ◽

Author(s):

Gillian McGregor ◽

Emma Bartle

Keyword(s):

Game Design ◽

Design Theory ◽

Teaching And Learning ◽

High Stress ◽

Psychology Students ◽

Professional Psychology ◽

The Body ◽

Serious Game ◽

Safe Delivery ◽

Stage Of Development

The education of healthcare professionals is critical for the safe delivery of services to patients (Ricciardi & de Paolis, 2014). Postgraduate psychology students undertaking a professional degree encounter a steep learning curve when transitioning from theoretical knowledge to professional practice. This beginning student stage of development is fraught with anxiety and high-stress levels, and has implications for both student and client wellbeing (Skovholt & Ronnestad, 2003). Successful navigation of this phase is critical to psychology graduate competence and employability, with potentially lasting consequences for psychologists’ perceptions of self-efficacy and career trajectory (De Stefano et al., 2007; Skovholt & Ronnestad, 2003). Serious games in health provide the potential for safe practice opportunities in an engaging and entertaining manner (Hawn, 2009; Knight et al., 2010). The author developed a serious game with the intention of providing postgraduate professional psychology students with increased and more convenient opportunity to practice psychological competencies. This paper synthesises game design theory into a prototype for educators to provide innovative solutions in a health context. It contributes to the body of research determining the efficacy of games in educational contexts and advances knowledge in the use of simulation pedagogies.

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Non hormonal management options for menstrual cycle irregularities

Medical Council ◽

10.21518/2079-701x-2019-13-16-27 ◽

2019 ◽

pp. 16-27 ◽

Cited By ~ 2

Author(s):

I. V. Kuznetsova

Keyword(s):

Menstrual Cycle ◽

High Stress ◽

The Body ◽

Stress Factors ◽

Organic Substrates ◽

Functional Disorders ◽

Management Options ◽

Menstrual Irregularities ◽

Menstrual Rhythm

Menstrual rhythm disorders and symptoms associated with the menstrual cycle are one of the main reasons for women to make an appointment with a gynecologist. After the endocrinopathies and organic substrates of menstrual irregularities are excluded, the doctor is faced with the difficult task to treat conditions that reflect the functional dysfunction of the body and its adaptation to high stress load. It is beyond argument that hormone therapy is the main resource of a gynecologist, but it is not always acceptable and does not solve all the problems of normalizing psychoneuroendocrine status. The dependence of functional disorders on environmental stress factors allows a doctor to use lifestyle correction, including rational nutrition and adding various micronutrients, in a program to improve the quality of life, eliminate psychoemotional symptoms and symptoms of autonomic dysfunction. In turn, the restoration of the adaptive reserve of the body becomes key to the recovery of menstrual function.

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