1
|
Vikas, Kumar R, Soni S. Measurement of anisotropy factor of nanoparticle embedded tumor phantoms for plasmonic photothermal therapeutics. JOURNAL OF BIOPHOTONICS 2024; 17:e202400007. [PMID: 38894568 DOI: 10.1002/jbio.202400007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Revised: 05/07/2024] [Accepted: 05/11/2024] [Indexed: 06/21/2024]
Abstract
Measurement of anisotropy factor (g) in the presence of nanoparticles (NPs) is important for understanding light distribution for plasmonic photothermal cancer therapeutics. Here, anisotropy factor is investigated through bilayer phantoms (epidermal and dermal) of various thicknesses incorporated with gold nanorods (GNRs) concentrations of 10-40 μg/mL by using in-house developed goniometric setup. Results show that 10 μg/mL GNRs in the phantom increase g by ~50% (g = 0.9471) w.r.t. phantom without NPs. Higher concentrations (40 μg/mL) of GNRs decrease g by ~43% (g = 0.5341) w.r.t. phantom with 10 μg/mL GNRs. For 40 μg/mL GNRs phantom, the anisotropy factor reduces by 47% for phantom thickness from 600 to 1800 μm. Anisotropy factor of GNR embedded phantom increased by 44% by using glycerol (10%-40%). Incorporation of NPs in a tumor significantly affects g, a major parameter for light distribution. These measurements provide insights for light scattering based on nanoparticle doses for plasmonic photothermal therapeutics.
Collapse
Affiliation(s)
- Vikas
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Biomedical Applications Group, CSIR-Central Scientific Instruments Organisation, Chandigarh, India
| | - Raj Kumar
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Micro and Nano Optics Centre, CSIR-Central Scientific Instruments Organisation, Chandigarh, India
| | - Sanjeev Soni
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
- Biomedical Applications Group, CSIR-Central Scientific Instruments Organisation, Chandigarh, India
| |
Collapse
|
2
|
Bradford DE, DeFalco A, Perkins ER, Carbajal I, Kwasa J, Goodman FR, Jackson F, Richardson LNS, Woodley N, Neuberger L, Sandoval JA, Huang HJ, Joyner KJ. Whose Signals Are Being Amplified? Toward a More Equitable Clinical Psychophysiology. Clin Psychol Sci 2024; 12:237-252. [PMID: 38645420 PMCID: PMC11028731 DOI: 10.1177/21677026221112117] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Research using psychophysiological methods holds great promise for refining clinical assessment, identifying risk factors, and informing treatment. Unfortunately, unique methodological features of existing approaches limit inclusive research participation and, consequently, generalizability. This brief overview and commentary provides a snapshot of the current state of representation in clinical psychophysiology, with a focus on the forms and consequences of ongoing exclusion of Black participants. We illustrate issues of inequity and exclusion that are unique to clinical psychophysiology, considering intersections among social constructions of Blackness and biased design of current technology used to measure electroencephalography, skin conductance, and other signals. We then highlight work by groups dedicated to quantifying and addressing these limitations. We discuss the need for reflection and input from a wider variety of stakeholders to develop and refine new technologies, given the risk of further widening disparities. Finally, we provide broad recommendations for clinical psychophysiology research.
Collapse
Affiliation(s)
| | | | | | - Iván Carbajal
- Oregon State University, School of Psychological Science
| | - Jasmine Kwasa
- Carnegie Mellon University, Center for the Neural Basis of Cognition
| | - Fallon R. Goodman
- George Washington University, Department of Psychological and Brain Sciences
| | | | | | | | | | | | - Helen J. Huang
- University of Central Florida, Department of Mechanical and Aerospace Engineering
| | | |
Collapse
|
3
|
Chen F, Sun M, Chen R, Li C, Shi J. Absolute Grüneisen parameter measurement in deep tissue based on X-ray-induced acoustic computed tomography. BIOMEDICAL OPTICS EXPRESS 2023; 14:1205-1215. [PMID: 36950240 PMCID: PMC10026575 DOI: 10.1364/boe.483490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/02/2023] [Accepted: 02/06/2023] [Indexed: 06/18/2023]
Abstract
The Grüneisen parameter is a primary parameter of the initial sound pressure signal in the photoacoustic effect, which can provide unique biological information and is related to the temperature change information of an object. The accurate measurement of this parameter is of great significance in biomedical research. Combining X-ray-induced acoustic tomography and conventional X-ray computed tomography, we proposed a method to obtain the absolute Grüneisen parameter. The theory development, numerical simulation, and biomedical application scenarios are discussed. The results reveal that our method not only can determine the Grüneisen parameter but can also obtain the body internal temperature distribution, presenting its potential in the diagnosis of a broad range of diseases.
Collapse
|
4
|
Vidallon MLP, Salimova E, Crawford SA, Teo BM, Tabor RF, Bishop AI. Enhanced photoacoustic imaging in tissue-mimicking phantoms using polydopamine-shelled perfluorocarbon emulsion droplets. ULTRASONICS SONOCHEMISTRY 2022; 86:106041. [PMID: 35617883 PMCID: PMC9136156 DOI: 10.1016/j.ultsonch.2022.106041] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 05/10/2022] [Accepted: 05/14/2022] [Indexed: 05/05/2023]
Abstract
The current work features process parameters for the ultrasound (25 kHz)-assisted fabrication of polydopamine-shelled perfluorocarbon (PDA/PFC) emulsion droplets with bimodal (modes at 100-600 nm and 1-6 µm) and unimodal (200-600 nm) size distributions. Initial screening of these materials revealed that only PDA/PFC emulsion droplets with bimodal distributions showed photoacoustic signal enhancement due to large size of their optically absorbing PDA shells. Performance of this particular type of emulsion droplets as photoacoustic agents were evaluated in Intralipid®-India ink media, mimicking the optical scattering and absorbanceof various tissuetypes. From these measurements, it was observed that PDA/PFC droplets with bimodal size distributions can enhance the photoacoustic signal of blood-mimicking phantom by up to five folds in various tissue-mimicking phantoms with absorption coefficients from 0.1 to 1.0 cm-1. Furthermore, using the information from enhanced photoacoustic images at 750 nm, the ultimate imaging depth was explored for polydopamine-shelled, perfluorohexane (PDA/PFH) emulsion droplets by photon trajectory simulations in 3D using a Monte Carlo approach. Based on these simulations, maximal tissue imaging depths for PDA/PFH emulsion droplets range from 10 to 40 mm, depending on the tissue type. These results demonstrate for the first time that ultrasonically fabricated PDA/PFC emulsion droplets have great potential as photoacoustic imaging agents that can be complemented with other reported characteristics of PDA/PFC emulsion droplets for extended applications in theranostics and other imaging modalities.
Collapse
Affiliation(s)
| | - Ekaterina Salimova
- Australian Regenerative Medicine Institute, Monash University, Clayton, VIC 3800, Australia; Monash Biomedical Imaging, Monash University, Clayton, VIC 3800, Australia
| | - Simon A Crawford
- Ramaciotti Centre for Cryo-Electron Microscopy, Monash University, Clayton, VIC 3800, Australia
| | - Boon Mian Teo
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia
| | - Rico F Tabor
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia.
| | - Alexis I Bishop
- School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Australia.
| |
Collapse
|
5
|
Webb EK, Etter JA, Kwasa JA. Addressing racial and phenotypic bias in human neuroscience methods. Nat Neurosci 2022; 25:410-414. [PMID: 35383334 PMCID: PMC9138180 DOI: 10.1038/s41593-022-01046-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 03/01/2022] [Indexed: 11/09/2022]
Abstract
Despite their premise of objectivity, neuroscience tools for physiological data collection, such as electroencephalography and functional near-infrared spectroscopy, introduce racial bias into studies by excluding individuals on the basis of phenotypic differences in hair type and skin pigmentation. Furthermore, at least one methodology-electrodermal activity recording (skin conductance responses)-may be influenced not only by potential phenotypic differences but also by negative psychological effects stemming from the lived experience of racism. Here we situate these issues within structural injustice, urge researchers to challenge racism in their scientific work and propose procedures and changes that may lead to more equitable science.
Collapse
Affiliation(s)
- E Kate Webb
- Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
- Division of Depression and Anxiety, McLean Hospital, Belmont, MA, USA.
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
| | - J Arthur Etter
- Department of Philosophy, McGill University, Montréal, QC, Canada
| | - Jasmine A Kwasa
- Neuroscience Institute, Carnegie Mellon University, Pittsburgh, PA, USA
| |
Collapse
|
6
|
Tomanič T, Rogelj L, Milanič M. Robustness of diffuse reflectance spectra analysis by inverse adding doubling algorithm. BIOMEDICAL OPTICS EXPRESS 2022; 13:921-949. [PMID: 35284194 PMCID: PMC8884198 DOI: 10.1364/boe.443880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/12/2021] [Accepted: 12/14/2021] [Indexed: 06/14/2023]
Abstract
Analysing diffuse reflectance spectra to extract properties of biological tissue requires modelling of light transport within the tissue, considering its absorption, scattering, and geometrical properties. Due to the layered skin structure, skin tissue models are often divided into multiple layers with their associated optical properties. Typically, in the analysis, some model parameters defining these properties are fixed to values reported in the literature to speed up the fitting process and improve its performance. In the absence of consensus, various studies use different approaches in fixing the model parameters. This study aims to assess the effect of fixing various model parameters in the skin spectra fitting process on the accuracy and robustness of a GPU-accelerated two-layer inverse adding-doubling (IAD) algorithm. Specifically, the performance of the IAD method is determined for noiseless simulated skin spectra, simulated spectra with different levels of noise applied, and in-vivo measured reflectance spectra from hyperspectral images of human hands recorded before, during, and after the arterial occlusion. Our results suggest that fixing multiple parameters to a priori known values generally improves the robustness and accuracy of the IAD algorithm for simulated spectra. However, for in-vivo measured spectra, these values are unknown in advance and fixing optical parameters to incorrect values significantly deteriorates the overall performance. Therefore, we propose a method to improve the fitting performance by pre-estimating model parameters. Our findings could be considered in all future research involving the analysis of diffuse reflectance spectra to extract optical properties of skin tissue.
Collapse
Affiliation(s)
- Tadej Tomanič
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
| | - Luka Rogelj
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
| | - Matija Milanič
- Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
- Jozef Stefan Institute, Jamova cesta 39, 1000 Ljubljana, Slovenia
| |
Collapse
|
7
|
Galeb HA, Wilkinson EL, Stowell AF, Lin H, Murphy ST, Martin‐Hirsch PL, Mort RL, Taylor AM, Hardy JG. Melanins as Sustainable Resources for Advanced Biotechnological Applications. GLOBAL CHALLENGES (HOBOKEN, NJ) 2021; 5:2000102. [PMID: 33552556 PMCID: PMC7857133 DOI: 10.1002/gch2.202000102] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/04/2020] [Indexed: 05/17/2023]
Abstract
Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.
Collapse
Affiliation(s)
- Hanaa A. Galeb
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Department of ChemistryScience and Arts CollegeRabigh CampusKing Abdulaziz UniversityJeddah21577Saudi Arabia
| | - Emma L. Wilkinson
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Alison F. Stowell
- Department of Organisation, Work and TechnologyLancaster University Management SchoolLancaster UniversityLancasterLA1 4YXUK
| | - Hungyen Lin
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
| | - Samuel T. Murphy
- Department of EngineeringLancaster UniversityLancasterLA1 4YWUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
| | - Pierre L. Martin‐Hirsch
- Lancashire Teaching Hospitals NHS TrustRoyal Preston HospitalSharoe Green LanePrestonPR2 9HTUK
| | - Richard L. Mort
- Department of Biomedical and Life SciencesLancaster UniversityLancasterLA1 4YGUK
| | - Adam M. Taylor
- Lancaster Medical SchoolLancaster UniversityLancasterLA1 4YWUK
| | - John G. Hardy
- Department of ChemistryLancaster UniversityLancasterLA1 4YBUK
- Materials Science InstituteLancaster UniversityLancasterLA1 4YBUK
| |
Collapse
|
8
|
Rehman AU, Ahmad I, Qureshi SA. Biomedical Applications of Integrating Sphere: A Review. Photodiagnosis Photodyn Ther 2020; 31:101712. [DOI: 10.1016/j.pdpdt.2020.101712] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 02/05/2020] [Accepted: 03/02/2020] [Indexed: 10/24/2022]
|
9
|
Investigations of the optical properties of enamel and dentin for early caries detection. Clin Oral Investig 2020; 25:1281-1289. [PMID: 32613436 DOI: 10.1007/s00784-020-03434-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/24/2020] [Indexed: 10/23/2022]
Abstract
INTRODUCTION The aim of this study was to experimentally investigate the potential of different light wavelengths to distinguish between healthy and carious tissue using a two-circle goniometer. MATERIALS AND METHODS Tooth slices were prepared from extracted human teeth that were caries free (n = 15) or had occlusal caries lesions (n = 10). The tooth slices were irradiated with diode laser modules of different wavelengths (532, 650, 780 nm). The transmitted and scattered laser light was spatially measured with a detector rotating on a two-circle goniometer. The anisotropy factor and attenuation coefficients were calculated. RESULTS Enamel was more transparent than dentin and showed wavelength-dependent attenuation. Healthy dentin showed strong light scattering at all wavelengths, independent of the tested wavelength. The calculated attenuation coefficients of carious and healthy tooth tissue differed significantly (p < 0.05; t test). In contrast to healthy enamel, carious enamel showed lower light transmission and an increase in scattering. Differences in the light attenuation of carious versus healthy dentin were less pronounced than those for enamel. Carious dentin was slightly more transparent than healthy dentin. The light of longer wavelengths showed a better penetration of all tooth structures compared with shorter wavelengths. CONCLUSION Healthy and carious dentin and enamel exhibited distinct optical properties using laser light at different wavelengths. In dentin, changes in the optical properties caused by caries are significantly less pronounced. CLINICAL RELEVANCE The clear distinction between healthy and carious enamel makes optical caries diagnostic systems ideal tools for early caries detection.
Collapse
|
10
|
Luecking M, Brinkmann R, Ramos S, Stork W, Heussner N. Capabilities and limitations of a new thermal finite volume model for the evaluation of laser-induced thermo-mechanical retinal damage. Comput Biol Med 2020; 122:103835. [PMID: 32479348 DOI: 10.1016/j.compbiomed.2020.103835] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 10/24/2022]
Abstract
Many experimental studies focus on the physical damage mechanisms of short-term exposure to laser radiation. In the nanosecond (ns) pulse range, damage in the Retinal Pigment Epithelium (RPE) will most likely occur at threshold levels due to bubble formation at the surface of the absorbing melanosome. The energy uptake of the melanosomes is one key aspect in modeling the bubble formation and damage thresholds. This work presents a thermal finite volume model for the investigation of rising temperatures and the temperature distribution of irradiated melanosomes. The model takes the different geometries and thermal properties of melanosomes into account, such as the heat capacity and thermal conductivity of the heterogeneous absorbing melanosomes and the surrounding tissue. This is the first time the size and shape variations on the melanosomes' thermal behavior are considered. The calculations illustrate the effect of the geometry on the maximum surface temperature of the irradiated melanosome and the impact on the bubble formation threshold. A comparison between the calculated bubble formation thresholds and the RPE cell damage thresholds within a pulse range of 3 to 5000 ns leads to a mean deviation of μ=22mJ/cm2 with a standard deviation of σ=21mJ/cm2. The best results are achieved between the simulation and RPE cell damage thresholds for pulse durations close to the thermal confinement time of individual melanosomes.
Collapse
Affiliation(s)
- Markus Luecking
- FZI Research Center for Information Technology Karlsruhe, Haid-und-Neu-Str. 10, 76131 Karlsruhe, Germany.
| | - Ralf Brinkmann
- Institute of Biomedical Optics, University of Luebeck, Peter-Monnik-Weg 4, 23562 Luebeck, Germany; Medical Laser Center Luebeck, Peter-Monnik-Weg 4, 23562 Luebeck, Germany
| | - Scarlett Ramos
- Robert Bosch GmbH, Herrenwiesenweg 24, 71701 Schwieberdingen, Germany
| | - Wilhelm Stork
- Institute for Information Processing Technologies, Karlsruhe Institute of Technology, Engesserstrasse 5, 76131 Karlsruhe, Germany
| | - Nico Heussner
- Robert Bosch GmbH, Herrenwiesenweg 24, 71701 Schwieberdingen, Germany
| |
Collapse
|
11
|
Ionescu AM, Chato-Astrain J, Cardona JDLC, Campos F, Pérez MM, Alaminos M, Garzón I. Evaluation of the optical and biomechanical properties of bioengineered human skin generated with fibrin-agarose biomaterials. JOURNAL OF BIOMEDICAL OPTICS 2020; 25:1-16. [PMID: 32383372 PMCID: PMC7203517 DOI: 10.1117/1.jbo.25.5.055002] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/24/2020] [Indexed: 05/21/2023]
Abstract
SIGNIFICANCE Recent generation of bioengineered human skin allowed the efficient treatment of patients with severe skin defects. However, the optical and biomechanical properties of these models are not known. AIM Three models of bioengineered human skin based on fibrin-agarose biomaterials (acellular, dermal skin substitutes, and complete dermoepidermal skin substitutes) were generated and analyzed. APPROACH Optical and biomechanical properties of these artificial human skin substitutes were investigated using the inverse adding-doubling method and tensile tests, respectively. RESULTS The analysis of the optical properties revealed that the model that most resembled the optical behavior of the native human skin in terms of absorption and scattering properties was the dermoepidermal human skin substitutes after 7 to 14 days in culture. The time-course evaluation of the biomechanical parameters showed that the dermoepidermal substitutes displayed significant higher values than acellular and dermal skin substitutes for all parameters analyzed and did not differ from the control skin for traction deformation, stress, and strain at fracture break. CONCLUSIONS We demonstrate the crucial role of the cells from a physical point of view, confirming that a bioengineered dermoepidermal human skin substitute based on fibrin-agarose biomaterials is able to fulfill the minimal requirements for skin transplants for future clinical use at early stages of in vitro development.
Collapse
Affiliation(s)
- Ana Maria Ionescu
- University of Granada, Laboratory of Biomaterials Optics, Department of Optics, Faculty of Sciences, Granada, Spain
- Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain
| | - Jesus Chato-Astrain
- University of Granada, Department of Histology, Faculty of Medicine, Tissue Engineering Group, Granada, Spain
| | - Juan de la Cruz Cardona
- University of Granada, Laboratory of Biomaterials Optics, Department of Optics, Faculty of Sciences, Granada, Spain
- Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain
| | - Fernando Campos
- University of Granada, Department of Histology, Faculty of Medicine, Tissue Engineering Group, Granada, Spain
| | - Maria M. Pérez
- University of Granada, Laboratory of Biomaterials Optics, Department of Optics, Faculty of Sciences, Granada, Spain
- Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain
| | - Miguel Alaminos
- Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain
- University of Granada, Department of Histology, Faculty of Medicine, Tissue Engineering Group, Granada, Spain
| | - Ingrid Garzón
- Instituto de Investigación Biosanitaria ibs.GRANADA, Granada, Spain
- University of Granada, Department of Histology, Faculty of Medicine, Tissue Engineering Group, Granada, Spain
| |
Collapse
|
12
|
Modeling the Reflectance Changes Induced by Vapor Condensation in Lycaenid Butterfly Wing Scales Colored by Photonic Nanoarchitectures. NANOMATERIALS 2019; 9:nano9050759. [PMID: 31108971 PMCID: PMC6566255 DOI: 10.3390/nano9050759] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/09/2019] [Accepted: 05/10/2019] [Indexed: 11/17/2022]
Abstract
Gas/vapor sensors based on photonic band gap-type materials are attractive as they allow a quick optical readout. The photonic nanoarchitectures responsible for the coloration of the wing scales of many butterfly species possessing structural color exhibit chemical selectivity, i.e., give vapor-specific optical response signals. Modeling this complex physical-chemical process is very important to be able to exploit the possibilities of these photonic nanoarchitectures. We performed measurements of the ethanol vapor concentration-dependent reflectance spectra of the Albulina metallica butterfly, which exhibits structural color on both the dorsal (blue) and ventral (gold-green) wing sides. Using a numerical analysis of transmission electron microscopy (TEM) images, we revealed the details of the photonic nanoarchitecture inside the wing scales. On both sides, it is a 1D + 2D structure, a stack of layers, where the layers contain a quasi-ordered arrangement of air voids embedded in chitin. Next, we built a parametric simulation model that matched the measured spectra. The reflectance spectra were calculated by ab-initio methods by assuming variable amounts of vapor condensed to liquid in the air voids, as well as vapor concentration-dependent swelling of the chitin. From fitting the simulated results to the measured spectra, we found a similar swelling on both wing surfaces, but more liquid was found to concentrate in the smaller air voids for each vapor concentration value measured.
Collapse
|
13
|
Ribera J, Panzarasa G, Stobbe A, Osypova A, Rupper P, Klose D, Schwarze FWMR. Scalable Biosynthesis of Melanin by the Basidiomycete Armillaria cepistipes. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2019; 67:132-139. [PMID: 30541276 DOI: 10.1021/acs.jafc.8b05071] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Natural melanin features many interesting properties, including the ability to shield electromagnetic radiation, the ability to act as scavenger for radical and reactive oxygen species and the capacity to chelate different metal ions. For these reasons, melanin is becoming increasingly relevant for the development of functional materials with potential applications in cosmetics, drug delivery, and water purification. However, the extraction and purification of melanin from conventional sources (e.g., sepia ink, hair, and wool) is inefficient and not easily scalable, hence diverting its technological applications. Some fungal species, especially wood-decay basidiomycetes, can be regarded as promising sources of melanin. In the present study, we screened different fungi in regard to their melanin-biosynthesis abilities using l-tyrosine as a precursor, and we found that an Armillaria cepistipes strain (Empa 655) produced the highest yield of melanin (27.98 g L-1). Physicochemical characterization of the obtained fungal melanin revealed a typical eumelanin structure. The method for the biosynthesis of fungal melanin we propose is efficient, scalable, and sustainable and has the potential to provide support for further technological exploitation.
Collapse
Affiliation(s)
- Javier Ribera
- Laboratory for Applied Wood Materials , Empa , Lerchenfeldstrasse 5 , St. Gallen 9014 , Switzerland
| | - Guido Panzarasa
- Laboratory for Soft and Living Materials, Department of Materials , ETH Zürich , Vladimir-Prelog-Weg 5 , Zürich 8093 , Switzerland
| | - Annika Stobbe
- Laboratory for Applied Wood Materials , Empa , Lerchenfeldstrasse 5 , St. Gallen 9014 , Switzerland
| | - Alina Osypova
- Innovative Sensor Technology, IST AG , Stegrütistrasse 14 , Ebnat-Kappel 9642 , Switzerland
| | - Patrick Rupper
- Laboratory for Advanced Fibers , Empa , Lerchenfeldstrase 5 , St. Gallen 9014 , Switzerland
| | - Daniel Klose
- Laboratory for Physical Chemistry, Department of Chemistry and Applied Biosciences , ETH Zürich , Vladimir-Prelog-Weg 5 , Zürich 8093 , Switzerland
| | - Francis W M R Schwarze
- Laboratory for Applied Wood Materials , Empa , Lerchenfeldstrasse 5 , St. Gallen 9014 , Switzerland
| |
Collapse
|
14
|
Jonasson H, Fredriksson I, Bergstrand S, Östgren CJ, Larsson M, Strömberg T. In vivo characterization of light scattering properties of human skin in the 475- to 850-nm wavelength range in a Swedish cohort. JOURNAL OF BIOMEDICAL OPTICS 2018; 23:1-6. [PMID: 30267487 DOI: 10.1117/1.jbo.23.12.121608] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 08/31/2018] [Indexed: 05/04/2023]
Abstract
We have determined in vivo optical scattering properties of normal human skin in 1734 subjects, mostly with fair skin type, within the Swedish CArdioPulmonary bioImage Study. The measurements were performed with a noninvasive system, integrating spatially resolved diffuse reflectance spectroscopy and laser Doppler flowmetry. Data were analyzed with an inverse Monte Carlo algorithm, accounting for both scattering, geometrical, and absorbing properties of the tissue. The reduced scattering coefficient was found to decrease from 3.16 ± 0.72 to 1.13 ± 0.27 mm-1 (mean ± SD) in the 475- to 850-nm wavelength range. There was a negative correlation between the reduced scattering coefficient and age, and a significant difference between men and women in the reduced scattering coefficient as well as in the fraction of small scattering particles. This large study on tissue scattering with mean values and normal variation can serve as a reference when designing diagnostic techniques or when evaluating the effect of therapeutic optical systems.
Collapse
Affiliation(s)
- Hanna Jonasson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
- Linköping University, Department of Medical and Health Sciences, Linköping, Sweden
| | - Ingemar Fredriksson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
- Perimed AB, Järfälla, Stockholm, Sweden
| | - Sara Bergstrand
- Linköping University, Department of Medical and Health Sciences, Linköping, Sweden
| | - Carl Johan Östgren
- Linköping University, Department of Medical and Health Sciences, Linköping, Sweden
| | - Marcus Larsson
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| | - Tomas Strömberg
- Linköping University, Department of Biomedical Engineering, Linköping, Sweden
| |
Collapse
|
15
|
Comparison of light propagation in dental tissues and nano-filled resin-based composite. Clin Oral Investig 2018; 23:423-433. [DOI: 10.1007/s00784-018-2451-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Accepted: 04/16/2018] [Indexed: 11/27/2022]
|
16
|
Stanciu SG, Tranca DE, Hristu R, Stanciu GA. Correlative imaging of biological tissues with apertureless scanning near-field optical microscopy and confocal laser scanning microscopy. BIOMEDICAL OPTICS EXPRESS 2017; 8:5374-5383. [PMID: 29296474 PMCID: PMC5745089 DOI: 10.1364/boe.8.005374] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 11/01/2017] [Accepted: 11/01/2017] [Indexed: 05/27/2023]
Abstract
Apertureless scanning near-field optical microscopy (ASNOM) has attracted considerable interest over the past years as a result of its valuable contrast mechanisms and capabilities for optical resolutions in the nanoscale range. However, at this moment the intersections between ASNOM and the realm of bioimaging are scarce, mainly due to data interpretation difficulties linked to the limited body of work performed so far in this field and hence the reduced volume of supporting information. We propose an imaging approach that holds significant potential for alleviating this issue, consisting of correlative imaging of biological specimens using a multimodal system that incorporates ASNOM and confocal laser scanning microscopy (CLSM), which allows placing near-field data into a well understood context of anatomical relevance. We demonstrate this approach on zebrafish retinal tissue. The proposed method holds important implications for the in-depth understanding of biological items through the prism of ASNOM and CLSM data complementarity.
Collapse
Affiliation(s)
- Stefan G. Stanciu
- Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Bucharest, 060042, Romania
| | - Denis E. Tranca
- Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Bucharest, 060042, Romania
| | - Radu Hristu
- Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Bucharest, 060042, Romania
| | - George A. Stanciu
- Center for Microscopy-Microanalysis and Information Processing, University Politehnica of Bucharest, Bucharest, 060042, Romania
| |
Collapse
|
17
|
Singh R, Rajaraman S, Balasubramanian M. A Novel Nanoparticle Mediated Selective Inner Retinal Photocoagulation for Diseases of the Inner Retina. IEEE Trans Nanobioscience 2017; 16:542-554. [PMID: 28829313 PMCID: PMC5926191 DOI: 10.1109/tnb.2017.2741490] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A novel nanoparticle mediated methodology for laser photocoagulation of the inner retina to achieve tissue selective treatment is presented. METHODS Transport of 527, 577, and 810 nm laser, heat deposition, and eventual thermal damage in vitreous, retina, RPE, choroid, and sclera were modeled using Bouguer-Beer-Lambert law of absorption and solved numerically using the finite volume method. Nanoparticles were designed using Mie theory of scattering. Performance of the new photocoagulation strategy using gold nanospheres and gold-silica nanoshells was compared with that of conventional methods without nanoparticles. For experimental validation, vitreous cavity of ex vivo porcine eyes was infused with gold nanospheres. After ~6 h of nanoparticle diffusion, the porcine retina was irradiated with a green laser and imaged simultaneously using a spectral domain optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering). RESULTS Our computational model predicted a significant spatial shift in the peak temperature from RPE to the inner retinal region when infused with nanoparticles. Arrhenius thermal damage in the mid-retinal location was achieved in ~14 ms for 527 nm laser thereby reducing the irradiation duration by ~30 ms compared with the treatment without nanoparticles. In ex vivo porcine eyes infused with gold nanospheres, SD-OCT retinal images revealed a lower thermal damage and expansion at RPE due to laser photocoagulation. CONCLUSION Nanoparticle infused laser photocoagulation strategy provided a selective inner retinal thermal damage with significant decrease in laser power and laser exposure time. SIGNIFICANCE The proposed treatment strategy shows possibilities for an efficient and highly selective inner retinal laser treatment.
Collapse
|
18
|
Effects of Depilation-Induced Skin Pigmentation and Diet-Induced Fluorescence on In Vivo Fluorescence Imaging. CONTRAST MEDIA & MOLECULAR IMAGING 2017; 2017:7659242. [PMID: 29097937 PMCID: PMC5612701 DOI: 10.1155/2017/7659242] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 05/17/2017] [Accepted: 05/21/2017] [Indexed: 01/24/2023]
Abstract
Near-infrared fluorescence imaging (NIRFI) and far-red fluorescence imaging (FRFI) were used to investigate effects of depilation-induced skin pigmentation and diet-induced background fluorescence on fluorescent signal amplitude and lymphatic contraction frequency in C57BL6 mice. Far-red fluorescent signal amplitude, but not frequency, was affected by diet-induced fluorescence, which was removed by feeding the mice an alfalfa-free diet, and skin pigmentation further impacted the amplitude measurement. NIRFI showed minimal background fluorescence; however, skin pigmentation reduced the amplitude of fluorescent signal changes. Therefore, these effects should be taken into account when imaging mice with different states of skin pigmentation and diet-induced background fluorescence in vivo.
Collapse
|
19
|
Fabrication and characterization of PVCP human breast tissue-mimicking phantom for photoacoustic imaging. BIOCHIP JOURNAL 2016. [DOI: 10.1007/s13206-016-1109-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
20
|
Kholodtsova MN, Daul C, Loschenov VB, Blondel WCPM. Spatially and spectrally resolved particle swarm optimization for precise optical property estimation using diffuse-reflectance spectroscopy. OPTICS EXPRESS 2016; 24:12682-12700. [PMID: 27410289 DOI: 10.1364/oe.24.012682] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
This paper presents a new approach to estimate optical properties (absorption and scattering coefficients µa and µs) of biological tissues from spatially-resolved spectroscopy measurements. A Particle Swarm Optimization (PSO)-based algorithm was implemented and firstly modified to deal with spatial and spectral resolutions of the data, and to solve the corresponding inverse problem. Secondly, the optimization was improved by fitting exponential decays to the two best points among all clusters of the "particles" randomly distributed all over the parameter space (µs, µa) of possible solutions. The consequent acceleration of all the groups of particles to the "best" curve leads to significant error decrease in the optical property estimation. The study analyzes the estimated optical property error as a function of the various PSO parameter combinations, and several performance criteria such as the cost-function error and the number of iterations in the algorithms proposed. The final one led to error values between ground truth and estimated values of µs and µa less than 6%.
Collapse
|
21
|
Zhu C, Ninh C, Bettinger CJ. Photoreconfigurable polymers for biomedical applications: chemistry and macromolecular engineering. Biomacromolecules 2014; 15:3474-94. [PMID: 25226507 DOI: 10.1021/bm500990z] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Stimuli-responsive polymers play an important role in many biomedical technologies. Light responsive polymers are particularly desirable because the parameters of irradiated light and diverse photoactive chemistries produce a large number of combinations between functional materials and associated stimuli. This Review summarizes recent advances in utilizing photoactive chemistries in macromolecules for prospective use in biomedical applications. Special focus is granted to selection criterion when choosing photofunctional groups. Synthetic strategies to incorporate these functionalities into polymers and networks with different topologies are also highlighted herein. Prospective applications of these materials are discussed including programmable matrices for controlled release, dynamic scaffolds for tissue engineering, and functional coatings for medical devices. The article concludes by summarizing the state of the art in photoresponsive polymers for biomedical applications including current challenges and future opportunities.
Collapse
Affiliation(s)
- Congcong Zhu
- Department of Materials Science and Engineering and ‡Department of Biomedical Engineering Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | | | | |
Collapse
|
22
|
Ninh C, Cramer M, Bettinger CJ. Photoresponsive hydrogel networks using melanin nanoparticle photothermal sensitizers. Biomater Sci 2014; 2:766-74. [PMID: 26828866 PMCID: PMC5877794 DOI: 10.1039/c3bm60321k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoreconfigurable and photodegradable polymeric networks have broad utility as functional biomaterials for many applications in medicine and biotechnology. The vast majority of these functional polymers are synthesized using chemical moieties that may be cytotoxic in vivo. Materials synthesized from these substituents also pose unknown risk upon implantation and thus will encounter significant regulatory challenges prior to use in vivo. This work describes a strategy to prepare photodegradable hydrogel networks that are composed of well-characterized synthetic polymers and natural melanin pigments found within the human body. Self-assembled networks of poly(l-lactide-co-glycolide)-poly(ethylene glycol) ABA triblock copolymers are doped with melanin nanoparticles to produce reconfigurable networks based on photothermal phase transitions. Self-assembled hydrogel networks with melanin nanoparticles exhibit a storage modulus ranging from 1.5 ± 0.6 kPa to 8.0 ± 7.5 kPa as measured by rheology. The rate of UV-induced photothermal heating was non-monotonic and varied as a function of melanin nanoparticle loading. A maximum steady state temperature increase of 20.5 ± 0.30 °C was measured. Experimental heating rates were in close agreement with predictions based on attenuation of light in melanins via photothermal absorption and Mie scattering. The implications of melanin nanoparticles on hydrogel network formation and light-induced disintegration were also characterized by rheology and dynamic light scattering. Taken together, this class of photoreconfigurable hydrogels represents a potential strategy for photodegradable polymers with increased likelihood for clinical translation.
Collapse
Affiliation(s)
- Chi Ninh
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Madeline Cramer
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA and Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Christopher J Bettinger
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA and Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA and McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
| |
Collapse
|
23
|
Optical and spectroscopic properties of human whole blood and plasma with and without Y₂O₃ and Nd³⁺:Y₂O₃ nanoparticles. Lasers Med Sci 2013; 28:1559-66. [PMID: 23380906 DOI: 10.1007/s10103-013-1268-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Accepted: 01/08/2013] [Indexed: 10/27/2022]
Abstract
The optical properties of human whole blood and blood plasma with and without Y₂O₃ and Nd³⁺:Y₂O₃ nanoparticles are characterized in the near infrared region at 808 nm using a double integrating sphere technique. Using experimentally measured quantities of diffuse reflectance and diffuse transmittance, a computational analysis was conducted utilizing the Kubelka-Munk, the Inverse Adding Doubling, and Magic Light Kubelka-Munk and Monte Carlo Methods to determine optical properties of the absorption and scattering coefficients. Room temperature absorption and emission spectra were also acquired of Nd³⁺:Y₂O₃ nanoparticles elucidating their utility as biological markers. The emission spectra of Nd³⁺:Y₂O₃ were taken by exciting the nanoparticles before and after entering the whole blood sample. The emission from the ⁴F(3/2) → ⁴I(11/2) manifold transition of Nd³⁺:Y₂O₃ nanoparticles readily propagates through the blood sample at excitation of 808 nm and exhibits a shift in relative intensities of the peaks due to differences in scattering. At 808 nm, in both whole blood and plasma samples, a direct relationship was found with absorption coefficient and Y₂O₃ nanoparticle concentration. Results for the whole blood indicate a small inverse relationship with Y₂O₃ nanoparticle concentration and scattering coefficient and in contrast a direct relation for the plasma.
Collapse
|
24
|
Peles DN, Simon JD. UV-absorption spectra of melanosomes containing varying 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid content. J Phys Chem B 2011; 115:12624-31. [PMID: 21923179 DOI: 10.1021/jp2060624] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Central to understanding the photochemical properties of melanosomes is a direct measurement of their absorption coefficients. Herein, the absorption spectra of intact melanosomes of varying molecular compositions and embryonic origins were measured and compared over the spectral range from 245 to 310 nm. The absorption spectra of melanosomes predominately comprised of the eumelanin pigment were found to differ significantly from their constituent precursor molecules, 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). This difference was most notable in the UV-A region and indicates that the electronic structures of the monomeric building blocks, DHICA in particular, are significantly modified upon polymerization to the melanin pigment. Furthermore, in comparing embryonic differences, the absorption coefficients of melanosomes isolated from bovine retinal pigment epithelial (RPE) cells (originating from the primitive forebrain) were greater than those for bovine choroid or iris melanosomes (originating from the neural crest). This difference suggests that either the pigment is present in greater density in RPE melanosomes or that there is an underlying difference in molecular structure.
Collapse
Affiliation(s)
- Dana N Peles
- Department of Chemistry, Duke University, Durham, North Carolina 27708, United States
| | | |
Collapse
|
25
|
Yust BG, Mimun LC, Sardar DK. Optical absorption and scattering of bovine cornea, lens, and retina in the near-infrared region. Lasers Med Sci 2011; 27:413-22. [PMID: 21556925 DOI: 10.1007/s10103-011-0927-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 04/11/2011] [Indexed: 11/30/2022]
Abstract
The optical properties of bovine ocular tissues have been determined at laser wavelengths in the near-infrared (NIR) region. The inverse adding doubling (IAD), Kubelka-Munk (KM), and inverse Monte Carlo (IMC) methods were applied to the measured values of the total diffuse transmission, total diffuse reflection, and collimated transmission to determine the optical absorption and scattering coefficients of the bovine cornea, lens and retina from 750 to 1,000 nm using a CW Ti:sapphire laser. The optical properties obtained from these three methods have been compared and are discussed.
Collapse
Affiliation(s)
- Brian G Yust
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249-0697, USA
| | | | | |
Collapse
|
26
|
Silverman RH, Kong F, Chen YC, Lloyd HO, Kim HH, Cannata JM, Shung KK, Coleman DJ. High-resolution photoacoustic imaging of ocular tissues. ULTRASOUND IN MEDICINE & BIOLOGY 2010; 36:733-42. [PMID: 20420969 PMCID: PMC2881573 DOI: 10.1016/j.ultrasmedbio.2010.02.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2009] [Revised: 01/28/2010] [Accepted: 02/11/2010] [Indexed: 05/04/2023]
Abstract
Optical coherence tomography (OCT) and ultrasound (US) are methods widely used for diagnostic imaging of the eye. These techniques detect discontinuities in optical refractive index and acoustic impedance, respectively. Because these both relate to variations in tissue density or composition, OCT and US images share a qualitatively similar appearance. In photoacoustic imaging (PAI), short light pulses are directed at tissues, pressure is generated due to a rapid energy deposition in the tissue volume and thermoelastic expansion results in generation of broadband US. PAI thus depicts optical absorption, which is independent of the tissue characteristics imaged by OCT or US. Our aim was to demonstrate the application of PAI in ocular tissues and to do so with lateral resolution comparable to OCT. We developed two PAI assemblies, both of which used single-element US transducers and lasers sharing a common focus. The first assembly had optical and 35-MHz US axes offset by a 30 degrees angle. The second assembly consisted of a 20-MHz ring transducer with a coaxial optics. The laser emitted 5-ns pulses at either 532 nm or 1064 nm, with spot sizes at the focus of 35 microm for the angled probe and 20 microm for the coaxial probe. We compared lateral resolution by scanning 12.5 microm diameter wire targets with pulse/echo US and PAI at each wavelength. We then imaged the anterior segment in whole ex vivo pig eyes and the choroid and ciliary body region in sectioned eyes. PAI data obtained at 1064 nm in the near infrared had higher penetration but reduced signal amplitude compared to that obtained using the 532 nm green wavelength. Images were obtained of the iris, choroid and ciliary processes. The zonules and anterior cornea and lens surfaces were seen at 532 nm. Because the laser spot size was significantly smaller than the US beamwidth at the focus, PAI images had superior resolution than those obtained using conventional US.
Collapse
Affiliation(s)
- Ronald H Silverman
- Department of Ophthalmology, Weill Cornell Medical College, New York, NY 10065, USA.
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Park J, Mroz P, Hamblin MR, Yaroslavsky AN. Dye-enhanced multimodal confocal microscopy for noninvasive detection of skin cancers in mouse models. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:026023. [PMID: 20459268 PMCID: PMC2866259 DOI: 10.1117/1.3394301] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Skin cancer is the most common form of human cancer. Its early diagnosis and timely treatment is of paramount importance for dermatology and surgical oncology. In this study, we evaluate the use of reflectance and fluorescence confocal microscopy for detecting skin cancers in an in-vivo trial with B16F10 melanoma and SCCVII squamous cell carcinoma in mice. For the experiments, the mice are anesthetized, then the tumors are infiltrated with aqueous solution of methylene blue and imaged. Reflectance images are acquired at 658 nm. Fluorescence is excited at 658 nm and registered in the range between 690 and 710 nm. After imaging, the mice are sacrificed. The tumors are excised and processed for hematoxylin and eosin histopathology, which is compared to the optical images. The results of the study indicate that in-vivo reflectance images provide valuable information on vascularization of the tumor, whereas the fluorescence images mimic the structural features seen in histopathology. Simultaneous dye-enhanced reflectance and fluorescence confocal microscopy shows promise for the detection, demarcation, and noninvasive monitoring of skin cancer development.
Collapse
Affiliation(s)
- Jesung Park
- Harvard Medical School, Massachusetts General Hospital, Wellman Center for Photomedicine, 55 Fruit Street, BAR314B, Boston, Massachusetts 02114, USA
| | | | | | | |
Collapse
|
28
|
Optical absorption and scattering of bovine cornea, lens and retina in the visible region. Lasers Med Sci 2009; 24:839-47. [PMID: 19495828 DOI: 10.1007/s10103-009-0677-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Accepted: 04/21/2009] [Indexed: 10/20/2022]
Abstract
Optical properties of bovine ocular tissues were determined at laser wavelengths in the visible region. The inverse adding doubling (IAD), Kubelka-Munk (KM), and inverse Monte Carlo (IMC) methods were applied to the measured values of the total diffuse transmission, total diffuse reflection, and collimated transmission to determine the optical absorption and scattering coefficients of the bovine cornea, lens and retina at 457.9 nm, 488 nm, and 514.5 nm laser lines from an argon ion laser. The optical properties obtained from these three methods were compared, and their validity is discussed.
Collapse
|
29
|
Li Q, Lee BJ, Zhang ZM, Allen DW. Light scattering of semitransparent sintered polytetrafluoroethylene films. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:054064. [PMID: 19021442 DOI: 10.1117/1.2992485] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Polytetrafluoroethylene (PTFE) is a strongly scattering material and has been regarded to have optical properties similar to biological tissues. In the present study, the bidirectional reflectance distribution function (BRDF) and the bidirectional transmittance distribution function (BTDF) of several PTFE films, with thicknesses from 0.11 to 10 mm, are measured using a laser scatterometer at the wavelength of 635 nm. The directional-hemispherical reflectance (R) and transmittance (T) were obtained by integrating BRDF and BTDF for normal incidence. Comparison of the ratio of the measured R and T with that calculated from the adding-doubling method allows the determination of the reduced scattering coefficient. Furthermore, the effect of surface scattering is investigated by measuring the polarization-dependent BRDF and BTDF at oblique incidence. By analyzing the measurement uncertainty of BTDF in the near-normal observation angles at normal incidence, the present authors found that the scattering coefficient of PTFE should exceed 1200 cm(-1), which is much greater than that of biological tissues. On the other hand, the absorption coefficient of PTFE must be less than 0.01 cm(-1), much smaller than that of biological tissues, a necessary condition to achieve R > or =0.98 with a 10-mm-thick slab.
Collapse
Affiliation(s)
- Qinghe Li
- Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, Georgia 30332, USA
| | | | | | | |
Collapse
|
30
|
Brown JS, Flitcroft DI, Ying GS, Francis EL, Schmid GF, Quinn GE, Stone RA. In vivo human choroidal thickness measurements: evidence for diurnal fluctuations. Invest Ophthalmol Vis Sci 2008; 50:5-12. [PMID: 18719079 DOI: 10.1167/iovs.08-1779] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The authors applied partial coherence interferometry (PCI) to estimate the thickness of the human choroid in vivo and to learn whether it fluctuates during the day. METHODS By applying signal processing techniques to existing PCI tracings of human ocular axial length measurements, a signal modeling algorithm was developed and validated to determine the position and variability of a postretinal peak that, by analogy to animal studies, likely corresponds to the choroidal/scleral interface. The algorithm then was applied to diurnal axial eye length datasets. RESULTS The postretinal peak was identified in 28% of subjects in the development and validation datasets, with mean subfoveal choroidal thicknesses of 307 and 293 microm, respectively. Twenty-eight of 40 diurnal PCI datasets had at least two time points with identifiable postretinal peaks, yielding a mean choroidal thickness of 426 microm and a mean high-low difference in choroidal thickness of 59.5 +/- 24.2 microm (range, 25.9-103 microm). The diurnal choroidal thickness fluctuation was larger than twice the SE of measurement (24.5 microm) in 16 of these 28 datasets. Axial length and choroidal thickness tended to fluctuate in antiphase. CONCLUSIONS Signal processing techniques provide choroidal thickness estimates in many, but not all, PCI datasets of axial eye measurements. Based on eyes with identifiable postretinal peaks at more than one time in a day, choroidal thickness varied over the day. Because of the established role of the choroid in retinal function and its possible role in regulating eye growth, further development and refinement of clinical methods to measure its thickness are warranted.
Collapse
Affiliation(s)
- Jamin S Brown
- Kresge Eye Institute, Wayne State University, Detroit, Michigan 48236, USA.
| | | | | | | | | | | | | |
Collapse
|
31
|
Zhu D, Lu W, Zeng S, Luo Q. Effect of light losses of sample between two integrating spheres on optical properties estimation. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:064004. [PMID: 18163820 DOI: 10.1117/1.2815691] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A Monte Carlo algorithm is applied to simulate the measurements of a sample with glass slides sandwiched between the double integrating sphere (DIS) setup. The effects caused by various parameters, such as the sample port of integrating sphere, thicknesses, and optical properties of the sample, on light losses and optical properties estimated by the inverse adding-doubling method (IAD) have been investigated. The results show that the light loss greatly increases the estimated error of absorption coefficient and slightly affects the estimated scattering coefficient. When the increase of apparent absorption of the sample induced by the light loss is 59%, the relative error of the scattering coefficient is less than 2% and that of the absorption coefficient reaches 28%. Enhancing the sample port diameter or decreasing the thickness of the sample can reduce the error effectively, and the effect of the former is much greater than that of the latter. In addition, the IAD method is proved to be valid for estimating the optical properties of a highly scattering or highly absorbing sample. This study can not only evaluate the error of optical properties estimation, but also provide optimal ways for the design of DIS and a scheme for acquiring accurate optical properties of tissue.
Collapse
Affiliation(s)
- Dan Zhu
- Huazhong University of Science and Technology, Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Wuhan, 430074, China
| | | | | | | |
Collapse
|
32
|
Bashkatov AN, Genina EA, Kochubey VI, Gavrilova AA, Kapralov SV, Grishaev VA, Tuchin VV. Optical properties of human stomach mucosa in the spectral range from 400 to 2000nm: Prognosis for gastroenterology. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.mla.2007.07.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
33
|
Cracknell KPB, Farnell DJJ, Grierson I. Monte Carlo simulation of latanoprost induced iris darkening. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2007; 87:93-103. [PMID: 17576020 DOI: 10.1016/j.cmpb.2007.04.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2006] [Revised: 04/24/2007] [Accepted: 04/27/2007] [Indexed: 05/15/2023]
Abstract
The aim of this study was to provide numerical evidence that latanoprost induced iris darkening (LIID) can be caused by changes to the melanin granule size distribution in the anterior segment of the iris. Iridectomies from two patients were used, where both had undergone unilateral treatment with latanoprost and had exhibited LIID. The untreated eye provided the comparative control. Micrographs from the iris samples were analysed to determine the number and size of the mature melanin granules. Monte Carlo (MC) simulation of light propagation in the iris was performed to examine the changes in reflectance and absorption with varying particle size and density. The reflected intensity of light was obtained as a function of wavelength. CIE colour theory was employed in order to estimate a perceived colour from the reflectance data. MC simulations showed that the reflectance was reduced for the LIID irises compared to the control irises for both subjects and for all wavelengths of light. The MC simulated colours were in good agreement with the in vivo photography of the eye colour. Hence, we have demonstrated that increases in melanin granule size causes iris darkening, and can explain LIID.
Collapse
Affiliation(s)
- K P B Cracknell
- Unit of Ophthalmology, Department of Medicine, University of Liverpool, Liverpool L69 3GA, United Kingdom.
| | | | | |
Collapse
|
34
|
Abstract
In this article, we review the current state of knowledge concerning the physical and chemical properties of the eumelanin pigment. We examine properties related to its photoprotective functionality, and draw the crucial link between fundamental molecular structure and observable macroscopic behaviour. Where necessary, we also briefly review certain aspects of the pheomelanin literature to draw relevant comparison. A full understanding of melanin function, and indeed its role in retarding or promoting the disease state, can only be obtained through a full mapping of key structure-property relationships in the main pigment types. We are engaged in such an endeavor for the case of eumelanin.
Collapse
Affiliation(s)
- Paul Meredith
- Soft Condensed Matter Physics Group, School of Physical Sciences, University of Queensland, Brisbane, Australia
| | | |
Collapse
|
35
|
Riesz J, Gilmore J, Meredith P. Quantitative scattering of melanin solutions. Biophys J 2006; 90:4137-44. [PMID: 16565050 PMCID: PMC1459487 DOI: 10.1529/biophysj.105.075713] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Accepted: 02/15/2006] [Indexed: 11/18/2022] Open
Abstract
The optical scattering coefficient of a dilute, well-solubilized eumelanin solution has been accurately measured as a function of incident wavelength, and found to contribute <6% of the total optical attenuation between 210 and 325 nm. At longer wavelengths (325-800 nm), the scattering was less than the minimum sensitivity of our instrument. This indicates that ultraviolet and visible optical density spectra can be interpreted as true absorption with a high degree of confidence. The scattering coefficient versus wavelength was found to be consistent with Rayleigh theory for a particle radius of 38 +/- 1 nm. Our results shed important light on the role of melanins as photoprotectants.
Collapse
Affiliation(s)
- Jennifer Riesz
- Soft Condensed Matter Physics Group, Condensed Matter Theory Group, Physics Department, University of Queensland, St. Lucia, Brisbane, Australia, QLD 4072.
| | | | | |
Collapse
|
36
|
Tran ML, Powell BJ, Meredith P. Chemical and structural disorder in eumelanins: a possible explanation for broadband absorbance. Biophys J 2006; 90:743-52. [PMID: 16284264 PMCID: PMC1367100 DOI: 10.1529/biophysj.105.069096] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2005] [Accepted: 09/26/2005] [Indexed: 11/18/2022] Open
Abstract
We report the results of an experimental and theoretical study of the electronic and structural properties of a key eumelanin precursor-5,6,-dihydroxyindole-2-carboxylic acid (DHICA)-and its dimeric forms. We have used optical spectroscopy to follow the oxidative polymerization of DHICA to eumelanin and observe red shifting and broadening of the absorption spectrum as the reaction proceeds. First principles density functional theory calculations indicate that DHICA oligomers (possible reaction products of oxidative polymerization) have the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital red-shifted gaps with respect to the monomer. Furthermore, different bonding configurations (leading to oligomers with different structures) produce a range of gaps. These experimental and theoretical results lend support to the chemical disorder model where the broadband monotonic absorption characteristic of all melanins is a consequence of the superposition of a large number of nonhomogeneously broadened Gaussian transitions associated with each of the components of a melanin ensemble. These results suggest that the traditional model of eumelanin as an amorphous organic semiconductor is not required to explain its optical properties and should be thoroughly reexamined. These results have significant implications for our understanding of the physics, chemistry, and biological function of these important biological macromolecules. Indeed, one may speculate that the robust functionality of melanins in vitro is a direct consequence of its heterogeneity, i.e., chemical disorder is a "low cost" natural resource in these systems.
Collapse
Affiliation(s)
- M Linh Tran
- Soft Condensed Matter Physics Group, and Theoretical Condensed Matter Physics Group, School of Physical Sciences, University of Queensland, Brisbane, QLD 4072, Australia
| | | | | |
Collapse
|
37
|
Nighswander-Rempel SP, Riesz J, Gilmore J, Meredith P. A quantum yield map for synthetic eumelanin. J Chem Phys 2005; 123:194901. [PMID: 16321107 DOI: 10.1063/1.2075147] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The quantum yield of synthetic eumelanin is known to be extremely low and it has recently been reported to be dependent on excitation wavelength. In this paper, we present quantum yield as a function of excitation wavelength between 250 and 500 nm, showing it to be a factor of 4 higher at 250 nm than at 500 nm. In addition, we present a definitive map of the steady-state fluorescence as a function of excitation and emission wavelengths, and significantly, a three-dimensional map of the "specific quantum yield": the fraction of photons absorbed at each wavelength that are subsequently radiated at each emission wavelength. This map contains clear features, which we attribute to certain structural models, and shows that radiative emission and specific quantum yield are negligible at emission wavelengths outside the range of 585 and 385 nm (2.2 and 3.2 eV), regardless of excitation wavelength. This information is important in the context of understanding melanin biofunctionality, and the quantum molecular biophysics therein.
Collapse
Affiliation(s)
- Stephen P Nighswander-Rempel
- Centre for Biophotonics and Laser Science, School of Physical Sciences, University of Queensland, St. Lucia, Queensland 4072, Australia.
| | | | | | | |
Collapse
|
38
|
Faraggi E, Gerstman BS, Sun J. Biophysical effects of pulsed lasers in the retina and other tissues containing strongly absorbing particles: shockwave and explosive bubble generation. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:064029. [PMID: 16409094 DOI: 10.1117/1.2139970] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Damage by pulsed lasers to the retina or other tissues containing strongly absorbing particles may occur through biophysical mechanisms other than simple heating. Shockwaves and bubbles have been observed experimentally, and depending on pulse duration, may be the cause of retinal damage at threshold fluence levels. We perform detailed calculations on the shockwave and bubble generation expected from pulsed lasers. For a variety of different laser pulse durations and fluences, we tabulate the expected strength of the shockwave and size of the bubble that will be generated. We also explain how these results will change for absorbing particles with different physical properties such as absorption coefficient, bulk modulus, or thermal expansion coefficient. This enables the assessment of biological danger, and possible medical benefits, for lasers of a wide range of pulse durations and energies, incident on tissues with absorbing particles with a variety of thermomechanical characteristics.
Collapse
Affiliation(s)
- Eshel Faraggi
- Florida International University, Physics Department, Miami, Florida 33199, USA.
| | | | | |
Collapse
|
39
|
Sardar DK, Yow RM, Tsin ATC, Sardar R. Optical scattering, absorption, and polarization of healthy and neovascularized human retinal tissues. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:051501. [PMID: 16292945 DOI: 10.1117/1.2065867] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The optical scattering, absorption, and polarization properties of human retinal tissues are investigated for a number of laser wavelengths in the visible range. The indices of refraction of these tissues are determined by applying Brewster's law. The inverse adding doubling method based on the diffusion approximation and radiative transport theory is applied to the measured values of total diffuse transmission, total diffuse reflection, and index of refraction to determine the optical absorption, scattering, and scattering anisotropy coefficients of the intact retinal tissues from healthy and diseased (neovascularized) human eyes. The polarization studies show that the retinal tissues possess significant intrinsic polarization characteristics, that are more pronounced in diseased tissues than in healthy tissues.
Collapse
Affiliation(s)
- Dhiraj K Sardar
- University of Texas at San Antonio, Department of Physics and Astronomy, San Antonio, Texas 78249-0697, USA.
| | | | | | | |
Collapse
|
40
|
Maswadi SM, Dodd SJ, Gao JH, Glickman RD. Temperature mapping of laser-induced hyperthermia in an ocular phantom using magnetic resonance thermography. JOURNAL OF BIOMEDICAL OPTICS 2004; 9:711-8. [PMID: 15250757 DOI: 10.1117/1.1751399] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Laser-induced heating in an ocular phantom is measured with magnetic resonance thermography (MRT) using temperature-dependent phase changes in proton resonance frequency. The ocular phantom contains a layer of melanosomes isolated from bovine retinal pigment epithelium. The phantom is heated by the 806-nm output of a continuous wave diode laser with an irradiance of 2.4 to 21.6 W/cm2 in a beam radius of 0.8 or 2.4 mm, depending on the experiment. MRT is performed with a 2 T magnet, and a two-turn, 6-cm-diam, circular radio frequency coil. Two-dimensional temperature gradients are measured within the plane of the melanin layer, as well as normal to it, with a temperature resolution of 1 degrees C or better. The temperature gradients extending within the melanin layer are broader than those orthogonal to the layer, consistent with the higher optical absorption and consequent heating in the melanin. The temperature gradients in the phantom measured by MRT closely approximate the predictions of a classical heat diffusion model. Three-dimensional temperature maps with a spatial resolution of 0.25 mm in all directions are also made. Although the temporal resolution is limited in the prototype system (22.9 s for a single image "slice"), improvements in future implementations are likely. These results indicate that MRT has sufficient spatial and temperature resolution to monitor target tissue temperature during transpupillary thermotherapy in the human eye.
Collapse
Affiliation(s)
- Saher M Maswadi
- University of Texas Health Science Center, Department of Ophthalmology, San Antonio, Texas 78229, USA
| | | | | | | |
Collapse
|
41
|
Sardar DK, Salinas FS, Perez JJ, Tsin ATC. Optical characterization of bovine retinal tissues. JOURNAL OF BIOMEDICAL OPTICS 2004; 9:624-631. [PMID: 15189102 DOI: 10.1117/1.1688813] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
An in-depth characterization of the optical properties of bovine retinal and retinal pigment epithelium-choroidal tissues has been performed. The indices of refraction of these ocular tissues were determined by applying Brewster's law. The inverse adding doubling method based on the diffusion approximation and radiative transport theory is applied to the measured values of the total diffuse transmission, total diffuse reflection, and collimated transmission to calculate the optical absorption, scattering, and scattering anisotropy coefficients of the bovine retinal and retinal pigment epithelium-choroidal tissues. The values of the optical properties obtained from the inverse adding doubling method are compared with those generated by the Monte Carlo simulation technique. Optical polarization measurements are also performed on bovine retinal tissues. Our studies show that both retina and retinal pigment epithelium-choroid possess strong polarization characteristics.
Collapse
Affiliation(s)
- Dhiraj K Sardar
- Department of Physics and Astronomy, The University of Texas at San Antonio, San Antonio, TX 78249-0697, USA.
| | | | | | | |
Collapse
|
42
|
Affiliation(s)
- Alfred Vogel
- Medical Laser Center Lübeck, Peter-Monnik-Weg 4, D-23562 Lübeck, Germany.
| | | |
Collapse
|
43
|
Abstract
Light damage to the retina occurs through three general mechanisms involving thermal, mechanical, or photochemical effects. The particular mechanism activated depends on the wavelength and exposure duration of the injuring light. The transitions between the various light damage mechanism may overlap to some extent. Energy confinement is a key concept in understanding or predicting the type of damage mechanism produced by a given light exposure. As light energy (either from a laser or an incoherent source) is deposited in the retina, its penetration through, and its absorption in, various tissue compartments is determined by its wavelength. Strongly absorbing tissue components will tend to "concentrate" the light energy. The effect of absorbed light energy largely depends on the rate of energy deposition, which is correlated with the exposure duration. If the rate of energy deposition is too low to produce an appreciable temperature increase in the tissue, then any resulting tissue damage necessarily occurs because of chemical (oxidative) reactions induced by absorption of energetic photons (photochemical damage). If the rate of energy deposition is faster than the rate of thermal diffusion (thermal confinement), then the temperature of the exposed tissue rises. If a critical temperature is reached (typically about 10 degrees C above basal), then thermal damage occurs. If the light energy is deposited faster than mechanical relaxation can occur (stress confinement), then a thermoelastic pressure wave is produced, and tissue is disrupted by shear forces or by cavitation-nonlinear effects. Very recent evidence suggests that ultrashort laser pulses can produce tissue damage through nonlinear and photochemical mechanisms; the latter because of two-photon excitation of cellular chromophores. In addition to tissue damage caused directly by light absorption, light toxicity can be produced by the presence of photosensitizing agents. Drugs excited to reactive states by ultraviolet (UV) or visible light produce damage by type I (free radical) and type II (oxygen dependent) mechanisms. Some commonly used drugs, such as certain antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), and psychotherapeutic agents, as well as some popular herbal medicines, can produce ocular phototoxicity. Specific cellular effects and damage end points characteristic of light damage mechanisms are described.
Collapse
Affiliation(s)
- Randolph D Glickman
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
| |
Collapse
|