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Cheng Z, Zhang N, Chang L, Qi P, Zhang L, Lin L, Wang Y, Liu W. Two-photon collagen crosslinking in ex vivo human corneal lenticules induced by near-infrared femtosecond laser. JOURNAL OF BIOPHOTONICS 2023; 16:e202200160. [PMID: 36153307 DOI: 10.1002/jbio.202200160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 08/24/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
Myopia and keratoconus have become common corneal diseases that threaten the quality of human vision, and keratoconus is one of the most common indications for corneal transplantation worldwide. Collagen crosslinking (CXL) using riboflavin and ultraviolet A (UVA) light is an effective approach for treating ophthalmic disorders and has been shown clinically not only to arrest further progression of keratoconus but also to improve refractive power for cornea. However, CXL surgery irradiated by UVA has various potential risks such as surface damage and endothelial cell damage. Here, near-infrared femtosecond laser-based two-photon CXL was first applied to ex vivo human corneal stroma, operating at low photon energy with high precision and stability. After two-photon CXL, the corneal stiffness can be enhanced by 300% without significantly reducing corneal transparency. These findings illustrate the optimized direction that depositing high pulses energy in corneal focal volume (not exceeding damage threshold), and pave the way to 3D CXL of in vivo human cornea with higher safety, precision, and efficacy.
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Affiliation(s)
- Zhenzhou Cheng
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Nan Zhang
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Le Chang
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Pengfei Qi
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Lin Zhang
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Lie Lin
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
| | - Yan Wang
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Weiwei Liu
- Institute of Modern Optics, Eye Institute, Nankai University, Key Laboratory of Micro-scale Optical Information Science and Technology, Tianjin, China
- Tianjin Eye Hospital, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin, China
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Batista A, Guimarães P, Domingues JP, Quadrado MJ, Morgado AM. Two-Photon Imaging for Non-Invasive Corneal Examination. SENSORS (BASEL, SWITZERLAND) 2022; 22:9699. [PMID: 36560071 PMCID: PMC9783858 DOI: 10.3390/s22249699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/02/2022] [Accepted: 12/04/2022] [Indexed: 06/17/2023]
Abstract
Two-photon imaging (TPI) microscopy, namely, two-photon excited fluorescence (TPEF), fluorescence lifetime imaging (FLIM), and second-harmonic generation (SHG) modalities, has emerged in the past years as a powerful tool for the examination of biological tissues. These modalities rely on different contrast mechanisms and are often used simultaneously to provide complementary information on morphology, metabolism, and structural properties of the imaged tissue. The cornea, being a transparent tissue, rich in collagen and with several cellular layers, is well-suited to be imaged by TPI microscopy. In this review, we discuss the physical principles behind TPI as well as its instrumentation. We also provide an overview of the current advances in TPI instrumentation and image analysis. We describe how TPI can be leveraged to retrieve unique information on the cornea and to complement the information provided by current clinical devices. The present state of corneal TPI is outlined. Finally, we discuss the obstacles that must be overcome and offer perspectives and outlooks to make clinical TPI of the human cornea a reality.
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Affiliation(s)
- Ana Batista
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Pedro Guimarães
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
| | - José Paulo Domingues
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Maria João Quadrado
- Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, 3004-561 Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - António Miguel Morgado
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
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Chang L, Zhang L, Cheng Z, Zhang N, Wang C, Wang Y, Liu W. Effectiveness of collagen cross-linking induced by two-photon absorption properties of a femtosecond laser in ex vivo human corneal stroma. BIOMEDICAL OPTICS EXPRESS 2022; 13:5067-5081. [PMID: 36187250 PMCID: PMC9484424 DOI: 10.1364/boe.468593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 06/16/2023]
Abstract
This study aimed to investigate the effectiveness of two-photon induced collagen cross-linking (CXL) using femtosecond lasers in human corneal stroma. An 800-nm femtosecond laser optical path for CXL was established. Corneal samples that received two-photon induced CXL and ultraviolet-A (UVA) CXL underwent uniaxial stretching experiments, proteolytic resistance assays and observation of collagen fiber structure changes. Two-photon induced CXL can achieve corneal stiffening effects comparable to UVA CXL and showed better advantages at low strains. The cornea after two-photon induced CXL exhibited high enzymatic resistance and tight collagen fiber arrangement. Two-photon induced CXL promises to be a new option for keratoconus.
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Affiliation(s)
- Le Chang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
| | - Lin Zhang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, No. 4 Gansu Road, Heping District, Tianjin 300020, China
| | - Zhenzhou Cheng
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
| | - Nan Zhang
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
| | - Congzheng Wang
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, No. 22 Meteorological Terrace Road, Heping District, Tianjin 300070, China
- Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, No. 4 Gansu Road, Heping District, Tianjin 300020, China
| | - Weiwei Liu
- Institute of Modern Optics, Nankai University, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
- Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, No. 94 Weijin Road, Nankai District, Tianjin 300071, China
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Chalimeswamy A, Thanuja MY, Ranganath SH, Pandya K, Kompella UB, Srinivas SP. Oxidative Stress Induces a Breakdown of the Cytoskeleton and Tight Junctions of the Corneal Endothelial Cells. J Ocul Pharmacol Ther 2021; 38:74-84. [PMID: 34818079 DOI: 10.1089/jop.2021.0037] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Purpose: To investigate the impact of oxidative stress, which is a hallmark of Fuchs dystrophy, on the barrier function of the corneal endothelial cells. Methods: Experiments were carried out with cultured bovine and porcine corneal endothelial cells. For oxidative stress, cells were supplemented with riboflavin (Rf) and exposed to UV-A (15-30 min) to induce Type-1 photochemical reactions that release H2O2. The effect of the stress on the barrier function was assayed by transendothelial electrical resistance (TER) measurement. In addition, the associated changes in the organization of the microtubules, perijunctional actomyosin ring (PAMR), and ZO-1 were evaluated by immunocytochemistry, which was also repeated after direct exposure to H2O2 (100 μM, 1 h). Results: Exposure to H2O2 led to the disassembly of microtubules and the destruction of PAMR. In parallel, the contiguous locus of ZO-1 was disrupted, marking a loss of barrier integrity. Accordingly, a sustained loss in TER was induced when cells in the Rf-supplemented medium were exposed to UV-A. However, the addition of catalase (7,000 U/mL) to rapidly decompose H2O2 limited the loss in TER. Furthermore, the adverse effects on microtubules, PAMR, and ZO-1 were suppressed by including catalase, ascorbic acid (1 mM; 30 min), or pretreatment with p38 MAP kinase inhibitor (SB-203580; 10 μM, 1 h). Conclusions: Acute oxidative stress induces microtubule disassembly by a p38 MAP kinase-dependent mechanism, leading to the destruction of PAMR and loss of barrier function. The response to oxidative stress is reminiscent of the (TNF-α)-induced breakdown of barrier failure in the corneal endothelium.
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Affiliation(s)
- Anupama Chalimeswamy
- Department of Biotechnology, Siddaganga Institute of Technology, Tumakuru, India.,Bio-INvENT Lab, Department of Chemical Engineering, Siddaganga Institute of Technology, Tumakuru, India
| | | | - Sudhir H Ranganath
- Bio-INvENT Lab, Department of Chemical Engineering, Siddaganga Institute of Technology, Tumakuru, India
| | - Kaveet Pandya
- School of Optometry, Indiana University, Bloomington, Indiana, USA
| | - Uday B Kompella
- Pharmaceutical Sciences, University of Colorado, Aurora, Colorado, USA
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Nonlinear optical crosslinking (NLO CXL) for correcting refractive errors. Exp Eye Res 2020; 199:108199. [PMID: 32846150 DOI: 10.1016/j.exer.2020.108199] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 11/21/2022]
Abstract
Ultraviolet A (UVA) light-based photoactivation of riboflavin (Rf) to induce corneal crosslinking (CXL) and mechanical stiffening is now a well-known treatment for corneal ectasia and Keratoconus that is being used in a topographically guided photorefractive intrastromal CXL (PiXL) procedure to treat low degrees of refractive errors. Alternative approaches for non-invasive treatment of refractive errors have also been proposed that use femtosecond lasers (FS) that provide much faster, more precise, and safer results than UVA CXL. One such treatment, nonlinear optical crosslinking (NLO CXL), has been able to replicate the effects of UVA CXL, while producing a smaller area of cellular damage and requiring a shorter procedure time. Unlike UVA CXL, the treatment volume of NLO CXL only occurs within the focal volume of the laser, which can be placed at any depth and scanned into any pattern for true topographically guided refractive correction. This review presents our experience with using FS lasers to photoactivate Rf and perform highly controlled corneal CXL that leads to mechanical stiffening and changes in corneal shape.
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Bradford S, Mikula E, Kim SW, Xie Y, Juhasz T, Brown DJ, Jester JV. Nonlinear Optical Corneal Crosslinking, Mechanical Stiffening, and Corneal Flattening Using Amplified Femtosecond Pulses. Transl Vis Sci Technol 2019; 8:35. [PMID: 31890347 PMCID: PMC6917096 DOI: 10.1167/tvst.8.6.35] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 10/06/2019] [Indexed: 12/14/2022] Open
Abstract
PURPOSE We have shown that nonlinear optical corneal crosslinking (NLO CXL) and stiffening can be achieved in ex vivo rabbit corneas using an 80-MHz, 760-nm femtosecond (FS) laser, however the required power was beyond the American National Standard Institute limit. The purpose of this study was to test the efficacy of amplified FS pulses to perform CXL to reduce power by increasing pulse energy. METHODS A variable numerical aperture laser scanning delivery system was coupled to a 1030-nm laser with a noncollinear optical parametric amplifier to generate 760 nm, 50 to 150 kHz amplified FS pulses with 79.5-μm axial and 2.9-μm lateral two-photon focal volume. Ex vivo rabbit corneas received NLO CXL, and effectiveness was assessed by measuring collagen autofluorescence (CAF) and mechanical stiffening. NLO CXL was also performed in 14 live rabbits, and changes in corneal topography were measured using an Orbscan. RESULTS Amplified pulses (0.3 μJ) generated significant CAF that increased logarithmically with decreasing scan speed; achieving equivalent CAF to UVA CXL at 15.5 mm/s. Indentation testing detected a 62% increase in stiffness compared to control, and corneal topography measurements revealed a significant decrease of 1.0 ± 0.8 diopter by 1 month (P < 0.05). CONCLUSIONS These results show that NLO CXL using amplified pulses can produce corneal collagen CXL comparable to UVA CXL. TRANSLATIONAL RELEVANCE NLO CXL using amplified pulses can produce corneal CXL comparable to UVA CXL, suggesting a potential clinical application in which NLO CXL can be used to perform personalized crosslinking for treatment of refractive errors and keratoconus.
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Affiliation(s)
- Samantha Bradford
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Eric Mikula
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Sun Woong Kim
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
- Yonsei University, Wonju College of Medicine, Department of Ophthalmology, Wonju, South Korea
| | - Yilu Xie
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Tibor Juhasz
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - Donald J. Brown
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
| | - James V. Jester
- University of California, Irvine, Department of Ophthalmology and Biomedical Engineering, Irvine, CA, USA
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7
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Khurana B, Gierlich P, Meindl A, Gomes-da-Silva LC, Senge MO. Hydrogels: soft matters in photomedicine. Photochem Photobiol Sci 2019; 18:2613-2656. [PMID: 31460568 DOI: 10.1039/c9pp00221a] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Photodynamic therapy (PDT), a shining beacon in the realm of photomedicine, is a non-invasive technique that utilizes dye-based photosensitizers (PSs) in conjunction with light and oxygen to produce reactive oxygen species to combat malignant tissues and infectious microorganisms. Yet, for PDT to become a common, routine therapy, it is still necessary to overcome limitations such as photosensitizer solubility, long-term side effects (e.g., photosensitivity) and to develop safe, biocompatible and target-specific formulations. Polymer based drug delivery platforms are an effective strategy for the delivery of PSs for PDT applications. Among them, hydrogels and 3D polymer scaffolds with the ability to swell in aqueous media have been deeply investigated. Particularly, hydrogel-based formulations present real potential to fulfill all requirements of an ideal PDT platform by overcoming the solubility issues, while improving the selectivity and targeting drawbacks of the PSs alone. In this perspective, we summarize the use of hydrogels as carrier systems of PSs to enhance the effectiveness of PDT against infections and cancer. Their potential in environmental and biomedical applications, such as tissue engineering photoremediation and photochemistry, is also discussed.
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Affiliation(s)
- Bhavya Khurana
- Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, Trinity College Dublin, The University of Dublin, St James's Hospital, Dublin 8, Ireland.
| | - Piotr Gierlich
- Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, Trinity College Dublin, The University of Dublin, St James's Hospital, Dublin 8, Ireland. and CQC, Coimbra Chemistry Department, University of Coimbra, Coimbra, Portugal
| | - Alina Meindl
- Physik Department E20, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany
| | | | - Mathias O Senge
- Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, Trinity College Dublin, The University of Dublin, St James's Hospital, Dublin 8, Ireland. and Physik Department E20, Technische Universität München, James-Franck-Str. 1, 85748 Garching, Germany and Institute for Advanced Study (TUM-IAS), Technische Universität München, Lichtenberg-Str. 2a, 85748 Garching, Germany
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8
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Magill BA, Guo X, Peck CL, Reyes RL, See EM, Santos WL, Robinson HD. Multi-photon patterning of photoactive o-nitrobenzyl ligands bound to gold surfaces. Photochem Photobiol Sci 2019; 18:30-44. [PMID: 30346005 DOI: 10.1039/c8pp00346g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
We quantitatively investigate lithographic patterning of a thiol-anchored self-assembled monolayer (SAM) of photocleavable o-nitrobenzyl ligands on gold through a multi-photon absorption process at 1.7 eV (730 nm wavelength). The photocleaving rate increases faster than the square of the incident light intensity, indicating a process more complex than simple two-photon absorption. We tentatively ascribe this observation to two-photon absorption that triggers the formation of a long-lived intermediate aci-nitro species whose decomposition yield is partially determined either by absorption of additional photons or by a local temperature that is elevated by the incident light. At the highest light intensities, thermal processes compete with photoactivation and lead to damage of the SAM. The threshold is high enough that this destructive process can largely be avoided, even while power densities are kept sufficiently large that complete photoactivation takes place on time scales of tens of seconds to a few minutes. This means that this type of ligand can be activated at visible and near infrared wavelengths where plasmonic resonances can easily be engineered in metal nanostructures, even though their single-photon reactivity at these wavelengths is negligible. This will allow selective functionalization of plasmon hotspots, which in addition to high resolution lithographic applications would be of benefit to applications such as Surface Enhanced Raman Spectroscopy and plasmonic photocatalysis as well as directed bottom-up nanoassembly.
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Affiliation(s)
- Brenden A Magill
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Xi Guo
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Cheryl L Peck
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Roberto L Reyes
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Erich M See
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Webster L Santos
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, USA
| | - Hans D Robinson
- Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA
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Bradford SM, Brown DJ, Juhasz T, Mikula E, Jester JV. Nonlinear optical corneal collagen crosslinking of ex vivo rabbit eyes. J Cataract Refract Surg 2018; 42:1660-1665. [PMID: 27956294 DOI: 10.1016/j.jcrs.2016.06.040] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Revised: 06/24/2016] [Accepted: 06/29/2016] [Indexed: 02/02/2023]
Abstract
PURPOSE To determine whether riboflavin-induced collagen crosslinking (CXL) could be precisely achieved in the corneal stroma of ex vivo rabbit eyes using nonlinear optical excitation with a low numerical aperture lens and enlarged focal volume. SETTING Gavin Herbert Eye Institute, University of California Irvine, Irvine, California, USA. DESIGN Experimental study. METHODS The corneal epithelium was removed and the corneas were soaked in 0.5% riboflavin solution. Using a 0.1 numerical aperture objective, a theoretical excitation volume of 150 μm × 3 μm was generated using 1 W of 760 nm femtosecond laser light and raster scanned with 4.4 μm line separation at varying effective speeds over a 4.50 mm × 2.25 mm area. Corneal sections were examined for collagen autofluorescence. RESULTS Collagen autofluorescence was enhanced 2.9 times compared with ultraviolet-A (UVA) CXL. Also, increasing speed was linearly associated with decreasing autofluorescence intensity. The slowest speed of 2.69 mm/s showed a mean of 182.97 μm ± 52.35 (SD) long autofluorescent scan lines axially in the central cornea compared with 147.84 ± 4.35 μm for UVA CXL. CONCLUSIONS Decreasing dwell time was linearly associated with decreasing autofluorescence intensity, approaching that of UVA CXL at a speed of 8.9 mm/s. Using an effective speed of 8.9 mm/s, nonlinear optical CXL could be achieved over a 3.0 mm diameter area in fewer than 4 minutes. Further development of nonlinear optical CXL might result in safer, faster, and more effective CXL treatments. FINANCIAL DISCLOSURE None of the authors has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Samantha M Bradford
- From the Department of Biomedical Engineering (Bradford, Brown, Juhasz, Jester) and the Department of Ophthalmology (Brown, Juhasz, Mikula, Jester), University of California, Irvine, California, USA
| | - Donald J Brown
- From the Department of Biomedical Engineering (Bradford, Brown, Juhasz, Jester) and the Department of Ophthalmology (Brown, Juhasz, Mikula, Jester), University of California, Irvine, California, USA
| | - Tibor Juhasz
- From the Department of Biomedical Engineering (Bradford, Brown, Juhasz, Jester) and the Department of Ophthalmology (Brown, Juhasz, Mikula, Jester), University of California, Irvine, California, USA
| | - Eric Mikula
- From the Department of Biomedical Engineering (Bradford, Brown, Juhasz, Jester) and the Department of Ophthalmology (Brown, Juhasz, Mikula, Jester), University of California, Irvine, California, USA
| | - James V Jester
- From the Department of Biomedical Engineering (Bradford, Brown, Juhasz, Jester) and the Department of Ophthalmology (Brown, Juhasz, Mikula, Jester), University of California, Irvine, California, USA.
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10
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Bradford SM, Mikula ER, Chai D, Brown DJ, Juhasz T, Jester JV. Custom built nonlinear optical crosslinking (NLO CXL) device capable of producing mechanical stiffening in ex vivo rabbit corneas. BIOMEDICAL OPTICS EXPRESS 2017; 8:4788-4797. [PMID: 29082102 PMCID: PMC5654817 DOI: 10.1364/boe.8.004788] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 09/22/2017] [Accepted: 09/25/2017] [Indexed: 06/07/2023]
Abstract
The purpose of this study was to develop and test a nonlinear optical device to photoactivate riboflavin to produce spatially controlled collagen crosslinking and mechanical stiffening within the cornea. A nonlinear optical device using a variable numerical aperture objective was built and coupled to a Chameleon femtosecond laser. Ex vivo rabbit eyes were then saturated with riboflavin and scanned with various scanning parameters over a 4 mm area in the central cornea. Effectiveness of NLO CXL was assessed by evaluating corneal collagen auto fluorescence (CAF). To determine mechanical stiffening effects, corneas were removed from the eye and subjected to indentation testing using a 1 mm diameter probe and force transducer. NLO CXL was also compared to standard UVA CXL. The NLO CXL delivery device was able to induce a significant increase in corneal stiffness, comparable to the increase produced by standard UVA CXL.
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Affiliation(s)
- Samantha M. Bradford
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Eric R. Mikula
- Department of Ophthalmology, 843 Health Sciences Road, University of California, Irvine, CA, 92697-4390, USA
| | - Dongyul Chai
- Department of Ophthalmology, 843 Health Sciences Road, University of California, Irvine, CA, 92697-4390, USA
| | - Donald J. Brown
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
- Department of Ophthalmology, 843 Health Sciences Road, University of California, Irvine, CA, 92697-4390, USA
| | - Tibor Juhasz
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
- Department of Ophthalmology, 843 Health Sciences Road, University of California, Irvine, CA, 92697-4390, USA
| | - James V. Jester
- Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
- Department of Ophthalmology, 843 Health Sciences Road, University of California, Irvine, CA, 92697-4390, USA
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Potential Effects of Corneal Cross-Linking upon the Limbus. BIOMED RESEARCH INTERNATIONAL 2016; 2016:5062064. [PMID: 27689081 PMCID: PMC5027324 DOI: 10.1155/2016/5062064] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 07/10/2016] [Indexed: 12/13/2022]
Abstract
Corneal cross-linking is nowadays the most used strategy for the treatment of keratoconus and recently it has been exploited for an increasing number of different corneal pathologies, from other ectatic disorders to keratitis. The safety of this technique has been widely assessed, but clinical complications still occur. The potential effects of cross-linking treatment upon the limbus are incompletely understood; it is important therefore to investigate the effect of UV exposure upon the limbal niche, particularly as UV is known to be mutagenic to cellular DNA and the limbus is where ocular surface tumors can develop. The risk of early induction of ocular surface cancer is undoubtedly rare and has to date not been published other than in one case after cross-linking. Nevertheless it is important to further assess, understand, and reduce where possible any potential risk. The aim of this review is to summarize all the reported cases of a pathological consequence for the limbal cells, possibly induced by cross-linking UV exposure, the studies done in vitro or ex vivo, the theoretical bases for the risks due to UV exposure, and which aspects of the clinical treatment may produce higher risk, along with what possible mechanisms could be utilized to protect the limbus and the delicate stem cells present within it.
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12
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Keratoconus and Other Corneal Diseases: Pharmacologic Cross-Linking and Future Therapy. Handb Exp Pharmacol 2016; 242:137-161. [PMID: 27815790 DOI: 10.1007/164_2016_23] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability to cross-link collagen fibers and use this technique to strengthen the cornea has become of great interest to ophthalmologists in the last decade. For progressive diseases such as keratoconus, collagen cross-linking confers the possibility of halting progression and stabilizing the cornea, a benefit that is not observed with any other current treatment. Collagen cross-linking uses riboflavin combined with ultraviolet A light to induce the formation of bonds between collagen fibrils that strengthen the cornea. This chapter will discuss the theory, technique, indications, and complications of corneal cross-linking. Much of what will be discussed is in areas of active research that will likely be further clarified as more experience is gained with this procedure.
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Kwok SJ, Kuznetsov IA, Kim M, Choi M, Scarcelli G, Yun SH. Selective two-photon collagen crosslinking in situ measured by Brillouin microscopy. OPTICA 2016; 3:469-472. [PMID: 28983498 PMCID: PMC5626012 DOI: 10.1364/optica.3.000469] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Two-photon polymerization has enabled precise microfabrication of three-dimensional structures with applications spanning from photonic microdevices, drug delivery systems, and cellular scaffolds. We present two-photon collagen crosslinking (2P-CXL) of intact corneal tissue using riboflavin and femtosecond laser irradiation. Collagen fiber orientations and photobleaching were characterized by second harmonic generation and two-photon fluorescence imaging, respectively. Measurement of local changes in longitudinal mechanical moduli with confocal Brillouin microscopy enabled the visualization of the cross-linked pattern without perturbation of the surrounding non-irradiated regions. 2P-CXL induced stiffening was comparable to that achieved with conventional one-photon CXL. Our results demonstrate the ability to selectively stiffen biological tissue in situ at high resolution with broad implications in ophthalmology, laser surgery, and tissue engineering.
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Affiliation(s)
- Sheldon J.J. Kwok
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
| | - Ivan A. Kuznetsov
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
- Department of Biomedical Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore MD 21218
| | - Moonseok Kim
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
| | - Myunghwan Choi
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon 16419, Korea
- Center for Neuroscience and Imaging Research, Institute for Basic Science (IBS), Suwon 16419, Korea
| | - Giuliano Scarcelli
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
- Fischell Department of Bioengineering, University of Maryland, College Park, MD 20742
| | - Seok Hyun Yun
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
- Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston MA 02114
- Corresponding author:
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Sorkin N, Varssano D. Corneal Collagen Crosslinking: A Systematic Review. Ophthalmologica 2014; 232:10-27. [DOI: 10.1159/000357979] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/10/2013] [Indexed: 11/19/2022]
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