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Wu J, Qiao H. Medical Imaging Technology and Imaging Agents. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1199:15-38. [PMID: 37460725 DOI: 10.1007/978-981-32-9902-3_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
Medical imaging is a technology that studies the interaction between human body and irradiations of X-ray, ultrasound, magnetic field, etc. and represents anatomical structures of human organs/tissues with the implication of irradiation attenuation in the form of grayscales. With these medical images, detailed information on health status and disease diagnosis may be judged by clinical physicians to determine an appropriate therapy approach. This chapter will give a systematic introduction on the modalities, classifications, basic principles, and biomedical applications of traditional medical imaging along with the types, construction, and major features of the corresponding contrast agents or imaging probes.
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Affiliation(s)
- Jieting Wu
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China
| | - Huanhuan Qiao
- Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin, China.
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2
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Monitoring New Long-Lasting Intravitreal Formulation for Glaucoma with Vitreous Images Using Optical Coherence Tomography. Pharmaceutics 2021; 13:pharmaceutics13020217. [PMID: 33562488 PMCID: PMC7915309 DOI: 10.3390/pharmaceutics13020217] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/27/2021] [Accepted: 02/02/2021] [Indexed: 01/07/2023] Open
Abstract
Intravitreal injection is the gold standard therapeutic option for posterior segment pathologies, and long-lasting release is necessary to avoid reinjections. There is no effective intravitreal treatment for glaucoma or other optic neuropathies in daily practice, nor is there a non-invasive method to monitor drug levels in the vitreous. Here we show that a glaucoma treatment combining a hypotensive and neuroprotective intravitreal formulation (IF) of brimonidine–Laponite (BRI/LAP) can be monitored non-invasively using vitreoretinal interface imaging captured with optical coherence tomography (OCT) over 24 weeks of follow-up. Qualitative and quantitative characterisation was achieved by analysing the changes in vitreous (VIT) signal intensity, expressed as a ratio of retinal pigment epithelium (RPE) intensity. Vitreous hyperreflective aggregates mixed in the vitreous and tended to settle on the retinal surface. Relative intensity and aggregate size progressively decreased over 24 weeks in treated rat eyes as the BRI/LAP IF degraded. VIT/RPE relative intensity and total aggregate area correlated with brimonidine levels measured in the eye. The OCT-derived VIT/RPE relative intensity may be a useful and objective marker for non-invasive monitoring of BRI/LAP IF.
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3
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Niendorf T, Beenakker JWM, Langner S, Erb-Eigner K, Bach Cuadra M, Beller E, Millward JM, Niendorf TM, Stachs O. Ophthalmic Magnetic Resonance Imaging: Where Are We (Heading To)? Curr Eye Res 2021; 46:1251-1270. [PMID: 33535828 DOI: 10.1080/02713683.2021.1874021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Magnetic resonance imaging of the eye and orbit (MReye) is a cross-domain research field, combining (bio)physics, (bio)engineering, physiology, data sciences and ophthalmology. A growing number of reports document technical innovations of MReye and promote their application in preclinical research and clinical science. Realizing the progress and promises, this review outlines current trends in MReye. Examples of MReye strategies and their clinical relevance are demonstrated. Frontier applications in ocular oncology, refractive surgery, ocular muscle disorders and orbital inflammation are presented and their implications for explorations into ophthalmic diseases are provided. Substantial progress in anatomically detailed, high-spatial resolution MReye of the eye, orbit and optic nerve is demonstrated. Recent developments in MReye of ocular tumors are explored, and its value for personalized eye models derived from machine learning in the treatment planning of uveal melanoma and evaluation of retinoblastoma is highlighted. The potential of MReye for monitoring drug distribution and for improving treatment management and the assessment of individual responses is discussed. To open a window into the eye and into (patho)physiological processes that in the past have been largely inaccessible, advances in MReye at ultrahigh magnetic field strengths are discussed. A concluding section ventures a glance beyond the horizon and explores future directions of MReye across multiple scales, including in vivo electrolyte mapping of sodium and other nuclei. This review underscores the need for the (bio)medical imaging and ophthalmic communities to expand efforts to find solutions to the remaining unsolved problems and technical obstacles of MReye, with the objective to transfer methodological advancements driven by MR physics into genuine clinical value.
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Affiliation(s)
- Thoralf Niendorf
- MRI.TOOLS GmbH, Berlin, Germany.,Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Jan-Willem M Beenakker
- Department of Ophthalmology and Department of Radiology, Leiden University Medical Centre, Leiden, The Netherlands
| | - Sönke Langner
- Institute of Diagnostic and Interventional Radiology, Pediatric Radiology and Neuroradiology, Rostock University Medical Center, Rostock, Germany
| | - Katharina Erb-Eigner
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität Zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | - Meritxell Bach Cuadra
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland.,Department of Radiology, Lausanne University and University Hospital, Lausanne, Switzerland
| | - Ebba Beller
- Institute of Diagnostic and Interventional Radiology, Pediatric Radiology and Neuroradiology, Rostock University Medical Center, Rostock, Germany
| | - Jason M Millward
- Berlin Ultrahigh Field Facility, Max Delbrueck Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | | | - Oliver Stachs
- Department Life, Light & Matter, University Rostock, Rostock, Germany.,Department of Ophthalmology, Rostock University Medical Center, Rostock, Germany
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4
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Molokhia S, Papangkorn K, Butler C, Higuchi JW, Brar B, Ambati B, Li SK, Higuchi WI. Transscleral Iontophoresis for Noninvasive Ocular Drug Delivery of Macromolecules. J Ocul Pharmacol Ther 2020; 36:247-256. [PMID: 32155098 DOI: 10.1089/jop.2019.0081] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Purpose: The objectives were to investigate the effect of transscleral iontophoresis of macromolecules in vitro and in vivo, to study the importance of electroosmosis on macromolecules of low charge to mass ratio, and to evaluate transscleral iontophoresis efficacy in a choroidal neovascularization (CNV) animal model. Methods: Through in vitro transport experiments, the permeability coefficients of macromolecules [eg, immunoglobulin G (IgG), dextran 70 kDa] were determined under different conditions. The effect of ionic strength formulations and iontophoretic conditions was studied on the distribution of IgG and bevacizumab into the eye in vivo. Magnetic resonance imaging (MRI) was utilized to evaluate in vivo real time distribution of gadolinium-labeled albumin (Galbumin) following iontophoresis. The efficacy between no treatment, intravitreal injection (IVT), and iontophoresis of bevacizumab on a CNV model of subretinal injection of adeno-associated virus encoding human VEGF-165 was investigated. Results: The permeability data suggested a significant effect of ionic strength on the iontophoretic transport of macromolecules. Transscleral iontophoresis of IgG at 4 mA with a low ionic strength formulation was about 600 times greater than passive diffusion and 14-fold over a conventional formulation in vitro. Approximately 0.6 mg of bevacizumab can be delivered into the rabbit eye in vivo with a 20-min treatment of iontophoresis. MRI showed that Galbumin was in the posterior tissues after iontophoresis. In the CNV model, the iontophoresis and IVT methods of bevacizumab delayed retinal neovascularization by 4 and 8 weeks, respectively. Conclusions: Transscleral iontophoresis is capable of delivering macromolecule drugs through the conjunctiva and sclera, eventually exposing the retina/choroid to the drugs.
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Affiliation(s)
- Sarah Molokhia
- Aciont, Inc., Salt Lake City, Utah.,iVeena Delivery Systems, Salt Lake City, Utah
| | | | | | | | | | - Balamurali Ambati
- iVeena Delivery Systems, Salt Lake City, Utah.,University of Utah, Salt Lake City, Utah
| | - S Kevin Li
- College of Pharmacy, University of Cincinnati, Cincinnati, Ohio
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5
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Normand G, Maker M, Penraat J, Kovach K, Ghosh JG, Grosskreutz C, Chandra S. Non-invasive molecular tracking method that measures ocular drug distribution in non-human primates. Commun Biol 2020; 3:16. [PMID: 31925329 PMCID: PMC6949284 DOI: 10.1038/s42003-019-0731-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 12/07/2019] [Indexed: 02/02/2023] Open
Abstract
Intravitreal (IVT) injection has become the standard route for drug administration in retinal diseases. However, the ability to measure biodistribution of ocular therapeutics in large species remains limited, due to the invasive nature of some techniques or their lack of spatial information. The aim of this study was to develop in cynomolgus monkeys a non-invasive fluorescence imaging technology that enables tracking of IVT-dosed drugs and could be easily translated into humans. Here, we show a proof-of-concept for labeled ranibizumab with observed half-lives of 3.34 and 4.52 days at the retina and in the vitreous, respectively. We further investigate a long acting anti-VEGF antibody, which remains as an agglomerate with some material leaking out until the end of the study at Day 35. Overall, we were able to visualize and measure differences in the in vivo behavior between short and long-acting antibodies, demonstrating the power of the technology for ocular pharmacokinetics. Guillaume Normand et al. present a non-invasive fluorescence imaging technology that enables a longitudinal tracking of drugs delivered into the eyes. This method allows direct monitoring of any drugs delivered into the eyes, which could potentially inform clinicians of optimal dosing frequency for each patient.
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Affiliation(s)
- Guillaume Normand
- Department of Translational Medicine, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA.
| | - Michael Maker
- Department of Translational Medicine, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA.,InviCRO, 27 Drydock Avenue, Boston, MA, 02210, USA
| | - Jan Penraat
- Lab Animal Services, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA.,PetSmart, 33963 Doheny Park Road - San Juan, Capistrano, CA, 92675, USA
| | - Kellyann Kovach
- Lab Animal Services, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA.,Pfizer Corporation, Comparative Medicine, Middletown Road, Pearl River, NY, USA
| | - Joy G Ghosh
- Ophthalmology Research, Novartis Institutes for BioMedical Research, Cambridge, MA, 02139, USA.,Bain Capital Life Sciences, 200 Clarendon Street, Boston, MA, 02116, USA
| | - Cynthia Grosskreutz
- Department of Translational Medicine, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA.,Ophthalmology Research, Novartis Institutes for Biomedical Research, Cambrodge, MA, 02139, USA
| | - Sudeep Chandra
- Department of Translational Medicine, Novartis Institutes for BioMedical Research, East Hanover, NJ, 07936, USA
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6
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Castro-Balado A, Mondelo-García C, González-Barcia M, Zarra-Ferro I, Otero-Espinar FJ, Ruibal-Morell Á, Aguiar-Fernández P, Fernández-Ferreiro A. Ocular Biodistribution Studies using Molecular Imaging. Pharmaceutics 2019; 11:pharmaceutics11050237. [PMID: 31100961 PMCID: PMC6572242 DOI: 10.3390/pharmaceutics11050237] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 05/05/2019] [Accepted: 05/07/2019] [Indexed: 02/07/2023] Open
Abstract
Classical methodologies used in ocular pharmacokinetics studies have difficulties to obtain information about topical and intraocular distribution and clearance of drugs and formulations. This is associated with multiple factors related to ophthalmic physiology, as well as the complexity and invasiveness intrinsic to the sampling. Molecular imaging is a new diagnostic discipline for in vivo imaging, which is emerging and spreading rapidly. Recent developments in molecular imaging techniques, such as positron emission tomography (PET), single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI), allow obtaining reliable pharmacokinetic data, which can be translated into improving the permanence of the ophthalmic drugs in its action site, leading to dosage optimisation. They can be used to study either topical or intraocular administration. With these techniques it is possible to obtain real-time visualisation, localisation, characterisation and quantification of the compounds after their administration, all in a reliable, safe and non-invasive way. None of these novel techniques presents simultaneously high sensitivity and specificity, but it is possible to study biological procedures with the information provided when the techniques are combined. With the results obtained, it is possible to assume that molecular imaging techniques are postulated as a resource with great potential for the research and development of new drugs and ophthalmic delivery systems.
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Affiliation(s)
- Ana Castro-Balado
- Pharmacy Department, University Hospital of Santiago de Compostela (SERGAS), 15706 Santiago de Compostela, Spain.
- Pharmacology Group, Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Cristina Mondelo-García
- Pharmacy Department, University Hospital of Santiago de Compostela (SERGAS), 15706 Santiago de Compostela, Spain.
- Pharmacology Group, Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Miguel González-Barcia
- Pharmacy Department, University Hospital of Santiago de Compostela (SERGAS), 15706 Santiago de Compostela, Spain.
- Pharmacology Group, Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Irene Zarra-Ferro
- Pharmacy Department, University Hospital of Santiago de Compostela (SERGAS), 15706 Santiago de Compostela, Spain.
- Pharmacology Group, Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Francisco J Otero-Espinar
- Department of Pharmacology, Pharmacy and Pharmaceutical Technology and Industrial Pharmacy Institute, Faculty of Pharmacy, University of Santiago de Compostela (USC), 15706 Santiago de Compostela, Spain.
| | - Álvaro Ruibal-Morell
- Nuclear Medicine Department, University Hospital of Santiago de Compostela (SERGAS), University of Santiago de Compostela, 15706 Santiago de Compostela, Spain.
- Molecular Imaging Group. Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Pablo Aguiar-Fernández
- Nuclear Medicine Department, University Hospital of Santiago de Compostela (SERGAS), University of Santiago de Compostela, 15706 Santiago de Compostela, Spain.
- Molecular Imaging Group. Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
| | - Anxo Fernández-Ferreiro
- Pharmacy Department, University Hospital of Santiago de Compostela (SERGAS), 15706 Santiago de Compostela, Spain.
- Pharmacology Group, Health Research Institute Santiago Compostela (IDIS), 15706 Santiago de Compostela, Spain.
- Department of Pharmacology, Pharmacy and Pharmaceutical Technology and Industrial Pharmacy Institute, Faculty of Pharmacy, University of Santiago de Compostela (USC), 15706 Santiago de Compostela, Spain.
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7
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Penkova A, Moats R, Humayun MS, Fraser S, Sadhal SS. Diffusive Transport in the Vitreous Humor: Experimental and Analytical Studies. JOURNAL OF HEAT TRANSFER 2019; 141:050801. [PMID: 35832509 PMCID: PMC9201755 DOI: 10.1115/1.4042297] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 12/11/2018] [Indexed: 06/01/2023]
Abstract
In relation to intravitreal drug delivery, predictive mathematical models for drug transport are being developed, and to effectively implement these for retinal delivery, the information on biophysical properties of various ocular tissues is fundamentally important. It is therefore necessary to accurately measure the diffusion coefficient of drugs and drug surrogates in the vitreous humor. In this review, we present the studies conducted by various researchers on such measurements over the last several decades. These include imaging techniques (fluorescence and magnetic resonance imaging (MRI)) that make use of introducing a contrast agent or a labeled drug into the vitreous and tracking its diffusive movement at various time points. A predictive model for the same initial conditions when matched with the experimental measurements provides the diffusion coefficient, leading to results for various molecules ranging in size from approximately 0.1 to 160 kDa. For real drugs, the effectiveness of this system depends on the successful labeling of the drugs with suitable contrast agents such as fluorescein and gadolinium or manganese so that fluorescence or MR imagining could be conducted. Besides this technique, some work has been carried out using the diffusion apparatus for measuring permeation of a drug across an excised vitreous body from a donor chamber to the receptor by sampling assays from the chambers at various time intervals. This has the advantage of not requiring labeling but is otherwise more disruptive to the vitreous. Some success with nanoparticles has been achieved using dynamic light scattering (DLS), and presently, radioactive labeling is being explored.
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Affiliation(s)
- Anita Penkova
- Department of Aerospace & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453
| | - Rex Moats
- Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027
| | - Mark S Humayun
- Department of Ophthalmology, USC Roski Eye Institute, Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033-4682; Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089-1111
| | - Scott Fraser
- Departments of Molecular and Computational Biology, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089-0371
| | - Satwindar Singh Sadhal
- Department of Aerospace & Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453
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8
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Neupane R, Gaudana R, Boddu SHS. Imaging Techniques in the Diagnosis and Management of Ocular Tumors: Prospects and Challenges. AAPS JOURNAL 2018; 20:97. [PMID: 30187172 DOI: 10.1208/s12248-018-0259-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 08/23/2018] [Indexed: 12/23/2022]
Abstract
Different types of imaging modalities are used in the diagnosis of ocular cancer. Selection of an imaging modality is based on the features of a tumor as well as the inherent characteristics of the imaging technique. It is vital to select an appropriate imaging modality in diagnosis of ocular tumor with confidence. This review focuses on five most commonly used imaging modalities, i.e., positron emission tomography-computed tomography (PET/CT), single photon emission computed tomography (SPECT), optical coherence tomography (OCT), ultrasound (US), and magnetic resonance imaging (MRI). The principal of imaging modalities is briefly explained, along with their role in the diagnosis and management of the most common ocular tumors such as retinoblastoma and uveal melanoma. Further, the diagnostic features of ocular tumors corresponding to each imaging modality and possibilities of utilizing imaging techniques in the process of ocular drug development are included in this review.
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Affiliation(s)
- Rabin Neupane
- College of Pharmacy and Pharmaceutical Sciences, The University of Toledo Health Science Campus, Toledo, OH, 43614, USA
| | - Ripal Gaudana
- Principal Scientist, Par Pharmaceuticals, 1 Ram Ridge Rd, Spring Valley, New York, 10977, USA
| | - Sai H S Boddu
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Ajman University, P.O. Box 346, Ajman, United Arab Emirates.
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9
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Ultrahigh field MR imaging of a subconjunctival anti-glaucoma drug delivery system in a rabbit model. Sci Rep 2017; 7:15780. [PMID: 29150670 PMCID: PMC5693897 DOI: 10.1038/s41598-017-15954-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/03/2017] [Indexed: 01/12/2023] Open
Abstract
Local drug delivery systems (DDS) have become a favourable approach for the treatment of numerous diseases. Biomedical imaging techniques such as ultrahigh field magnetic resonance imaging (UHF-MRI) offer unique insight into DDS biodegradation in vivo. We describe the establishment of a 7 Tesla MRI routine for longitudinal in vivo examinations of a subconjunctival DDS for the treatment of glaucoma in a rabbit model. In initial in vitro examinations the T2-relaxation times of the polymeric DDS components were assessed. Imaging of enzymatically degraded depot samples in vitro did not reveal changes in sample morphology or T2-relaxation time. Ex vivo investigations with an enucleated porcine eye showed good correlation of anatomical MRI and histological data. In longitudinal in vivo studies in rabbits, we repeatedly scanned the depot in the same animal over the course of 5 months with an in-plane resolution of 130 µm at scan times of less than 30 minutes. The degradation was quantified using volumetric analysis showing a volume reduction of 82% between 3 and 21 weeks after depot implantation. We have thereby demonstrated the feasibility of our UHF-MRI protocol as a non-invasive imaging routine for qualitative and quantitative, longitudinal evaluation of biodegradable subconjunctival DDS.
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10
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Del Amo EM, Rimpelä AK, Heikkinen E, Kari OK, Ramsay E, Lajunen T, Schmitt M, Pelkonen L, Bhattacharya M, Richardson D, Subrizi A, Turunen T, Reinisalo M, Itkonen J, Toropainen E, Casteleijn M, Kidron H, Antopolsky M, Vellonen KS, Ruponen M, Urtti A. Pharmacokinetic aspects of retinal drug delivery. Prog Retin Eye Res 2016; 57:134-185. [PMID: 28028001 DOI: 10.1016/j.preteyeres.2016.12.001] [Citation(s) in RCA: 403] [Impact Index Per Article: 50.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/25/2016] [Accepted: 12/01/2016] [Indexed: 12/14/2022]
Abstract
Drug delivery to the posterior eye segment is an important challenge in ophthalmology, because many diseases affect the retina and choroid leading to impaired vision or blindness. Currently, intravitreal injections are the method of choice to administer drugs to the retina, but this approach is applicable only in selected cases (e.g. anti-VEGF antibodies and soluble receptors). There are two basic approaches that can be adopted to improve retinal drug delivery: prolonged and/or retina targeted delivery of intravitreal drugs and use of other routes of drug administration, such as periocular, suprachoroidal, sub-retinal, systemic, or topical. Properties of the administration route, drug and delivery system determine the efficacy and safety of these approaches. Pharmacokinetic and pharmacodynamic factors determine the required dosing rates and doses that are needed for drug action. In addition, tolerability factors limit the use of many materials in ocular drug delivery. This review article provides a critical discussion of retinal drug delivery, particularly from the pharmacokinetic point of view. This article does not include an extensive review of drug delivery technologies, because they have already been reviewed several times recently. Instead, we aim to provide a systematic and quantitative view on the pharmacokinetic factors in drug delivery to the posterior eye segment. This review is based on the literature and unpublished data from the authors' laboratory.
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Affiliation(s)
- Eva M Del Amo
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Anna-Kaisa Rimpelä
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Emma Heikkinen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Otto K Kari
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Eva Ramsay
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Tatu Lajunen
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Mechthild Schmitt
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Laura Pelkonen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Madhushree Bhattacharya
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Dominique Richardson
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Astrid Subrizi
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Tiina Turunen
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Mika Reinisalo
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Jaakko Itkonen
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Elisa Toropainen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Marco Casteleijn
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Heidi Kidron
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | - Maxim Antopolsky
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland
| | | | - Marika Ruponen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Arto Urtti
- Centre for Drug Research, Division of Pharmaceutical Biosciences, University of Helsinki, Helsinki, Finland; School of Pharmacy, University of Eastern Finland, Kuopio, Finland.
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11
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Tsiapa I, Tsilimbaris MK, Papadaki E, Bouziotis P, Pallikaris IG, Karantanas AH, Maris TG. High resolution MR eye protocol optimization: Comparison between 3D-CISS, 3D-PSIF and 3D-VIBE sequences. Phys Med 2015; 31:774-80. [DOI: 10.1016/j.ejmp.2015.03.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Revised: 03/03/2015] [Accepted: 03/19/2015] [Indexed: 10/23/2022] Open
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12
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Stein S, Simroth-Loch C, Langner S, Hadlich S, Stachs O, Grabow N, Guthoff R, Weitschies W, Seidlitz A. MR imaging of model drug distribution in simulated vitreous. CURRENT DIRECTIONS IN BIOMEDICAL ENGINEERING 2015. [DOI: 10.1515/cdbme-2015-0059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
AbstractThe in vitro and in vivo characterization of intravitreal injections plays an important role in developing innovative therapy approaches. Using the established vitreous model (VM) and eye movement system (EyeMoS) the distribution of contrast agents with different molecular weight was studied in vitro. The impact of the simulated age-related vitreal liquefaction (VL) on drug distribution in VM was examined either with injection through the gel phase or through the liquid phase. For comparison the distribution was studied ex vivo in the porcine vitreous. The studies were performed in a magnetic resonance (MR) scanner. As expected, with increasing molecular weight the diffusion velocity and the visual distribution of the injected substances decreased. Similar drug distribution was observed in VM and in porcine eye. VL causes enhanced convective flow and faster distribution in VM. Confirming the importance of the injection technique in progress of VL, injection through gelatinous phase caused faster distribution into peripheral regions of the VM than following injection through liquefied phase. VM and MR scanner in combination present a new approach for the in vitro characterization of drug release and distribution of intravitreal dosage forms.
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Affiliation(s)
- Sandra Stein
- 2Institute of Pharmacy, Center of Drug Absorption and Transport, Ernst-MoritzArndt-University of Greifswald, Felix-Hausdorff-Strasse 3, 17487 Greifswald, Germany
| | - Christian Simroth-Loch
- 2Institute of Pharmacy, Center of Drug Absorption and Transport, Ernst-MoritzArndt-University of Greifswald, Felix-Hausdorff-Strasse 3, 17487 Greifswald, Germany
| | - Sönke Langner
- 3Institute for Diagnostic Radiology and Neuroradiology, Greifswald University Hospital, 17475 Greifswald, Germany
| | - Stefan Hadlich
- 4Department of Ophthalmology, University of Rostock, 18057 Rostock, Germany
| | - Oliver Stachs
- 3Institute for Diagnostic Radiology and Neuroradiology, Greifswald University Hospital, 17475 Greifswald, Germany
| | - Niels Grabow
- 5Institute for Biomedical Engineering, University of Rostock, 18119 Rostock, Germany
| | - Rudolf Guthoff
- 4Department of Ophthalmology, University of Rostock, 18057 Rostock, Germany
| | - Werner Weitschies
- 2Institute of Pharmacy, Center of Drug Absorption and Transport, Ernst-MoritzArndt-University of Greifswald, Felix-Hausdorff-Strasse 3, 17487 Greifswald, Germany
| | - Anne Seidlitz
- 1Institute of Pharmacy, Center of Drug Absorption and Transport, Ernst-Moritz-Arndt-University of Greifswald, Felix-Hausdorff-Strasse 3, 17487 Greifswald, Germany, phone: +49 3834 864898 fax: +49 3834 864886
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Fernández-Ferreiro A, González Barcia M, Gil-Martínez M, Vieites-Prado A, Lema I, Argibay B, Blanco Méndez J, Lamas MJ, Otero-Espinar FJ. In vitro and in vivo ocular safety and eye surface permanence determination by direct and Magnetic Resonance Imaging of ion-sensitive hydrogels based on gellan gum and kappa-carrageenan. Eur J Pharm Biopharm 2015; 94:342-51. [PMID: 26079831 DOI: 10.1016/j.ejpb.2015.06.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 05/20/2015] [Accepted: 06/08/2015] [Indexed: 11/17/2022]
Abstract
Gellan gum, kappa-carrageenan and alginates are natural polysaccharides able to interact with different cations that can be used to elaborate ion-activated in situ gelling systems for different uses. The interaction between fluid solutions of these polysaccharides and cations presents into the tear made these biopolymers very interesting to elaborate ophthalmic drug delivery systems. The main purpose of this study is to evaluate the ability of mixtures of these polymers to obtain ion-activated ophthalmic in situ gelling systems with optimal properties for ocular use. To achieve this purpose different proportion of the biopolymers were analyzed using a mixture experimental design evaluating their transparency, mechanical properties and bioadhesion in the absence and presence of simulated tear fluid. Tear induces a rapid sol-to-gel phase transition in the mixtures forming a consistent hydrogel. The solution composed by 80% of gellan gum and 20% kappa-carrageenan showed the best mechanical and mucoadhesive properties. This mixture was evaluated for rheological behavior, microstructure, cytotoxicity, acute corneal irritancy, ex-vivo and in vivo ocular toxicity and in vivo corneal contact time using Magnetic Resonance Images (MRI) techniques. Result indicates that the system is safe at ophthalmic level and produces an extensive ocular permanence higher than 6h.
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Affiliation(s)
- Anxo Fernández-Ferreiro
- Pharmacy and Pharmaceutical Technology Department and Industrial Pharmacy Institute, Faculty of Pharmacy, University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela 15782, Spain; Pharmacy Department, Xerencia de Xestión Integrada de Santiago de Compostela (SERGAS), Travesía Choupana s/n, Santiago de Compostela 15706, Spain; Clinical Pharmacology Group, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain
| | - Miguel González Barcia
- Pharmacy Department, Xerencia de Xestión Integrada de Santiago de Compostela (SERGAS), Travesía Choupana s/n, Santiago de Compostela 15706, Spain; Clinical Pharmacology Group, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain
| | - María Gil-Martínez
- Instituto Oftalmológico Gómez-Ulla, Rúa de Maruxa Mallo, 3, Santiago de Compostela 15706, Spain
| | - Alba Vieites-Prado
- Clinical Neurosciences Research Laboratory, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain
| | - Isabel Lema
- Clinical Neurosciences Research Laboratory, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain; Surgery Department (Ophthalmology), Faculty of Optics and Optometry, University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela 15782, Spain
| | - Barbara Argibay
- Clinical Neurosciences Research Laboratory, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain
| | - José Blanco Méndez
- Pharmacy and Pharmaceutical Technology Department and Industrial Pharmacy Institute, Faculty of Pharmacy, University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela 15782, Spain
| | - Maria Jesus Lamas
- Pharmacy Department, Xerencia de Xestión Integrada de Santiago de Compostela (SERGAS), Travesía Choupana s/n, Santiago de Compostela 15706, Spain; Clinical Pharmacology Group, Health Research Institute of Santiago de Compostela (IDIS), Travesía da Choupana s/n, Santiago de Compostela 15706, Spain
| | - Francisco Javier Otero-Espinar
- Pharmacy and Pharmaceutical Technology Department and Industrial Pharmacy Institute, Faculty of Pharmacy, University of Santiago de Compostela (USC), Campus Vida, Santiago de Compostela 15782, Spain.
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14
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Feng L, Li SK, Liu H, Liu CY, LaSance K, Haque F, Shu D, Guo P. Ocular delivery of pRNA nanoparticles: distribution and clearance after subconjunctival injection. Pharm Res 2013; 31:1046-58. [PMID: 24297069 DOI: 10.1007/s11095-013-1226-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Accepted: 10/03/2013] [Indexed: 12/28/2022]
Abstract
PURPOSE RNA nanoparticles derived from the three-way junction (3WJ) of the pRNA of bacteriophage phi29 DNA packaging motor were previously found to be thermodynamically stable. As the nanoparticles could have potential in ocular drug delivery, the objectives in the present study were to investigate the distribution of pRNA nanoparticles after subconjunctival injection and examine the feasibility to deliver the nanoparticles to the cells of cornea and retina. METHODS Alexa647-labeled pRNA nanoparticles (pRNA-3WJ and pRNA-X) and double-stranded RNA (dsRNA) were administered via subconjunctival injection in mice. Alexa647 dye was a control. Topical administration was performed for comparison. Ocular clearance of pRNA nanoparticles and dsRNA after the injection was assessed using whole-body fluorescence imaging of the eyes. The numbers of cells in the ocular tissues with nanoparticle cell internalization were determined in fluorescence microscopy of dissected eye tissues. RESULTS After subconjunctival injection, pRNA nanoparticles and dsRNA were observed to distribute into the eyes and cleared through the lymph. pRNA-3WJ, pRNA-X, and dsRNA were found in the cells of the conjunctiva, cornea, and sclera, but only pRNA-X was in the cells of the retina. Topical administration was not effective in delivering the nanoparticles to the eye. CONCLUSIONS The pRNA nanoparticles were delivered to the cells in the eye via subconjunctival injection, and cell internalization was achieved in the cornea with pRNA-3WJ and pRNA-X and in the retina with pRNA-X. Only the X-shape pRNA-X could enter the retina.
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Affiliation(s)
- Liang Feng
- Division of Pharmaceutical Sciences James L. Winkle College of Pharmacy, University of Cincinnati, 3225 Eden Avenue 136 HPB, Cincinnati, Ohio, 45267, USA
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15
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Fanea L, Fagan AJ. Review: magnetic resonance imaging techniques in ophthalmology. Mol Vis 2012; 18:2538-60. [PMID: 23112569 PMCID: PMC3482169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Accepted: 10/10/2012] [Indexed: 11/19/2022] Open
Abstract
Imaging the eye with magnetic resonance imaging (MRI) has proved difficult due to the eye's propensity to move involuntarily over typical imaging timescales, obscuring the fine structure in the eye due to the resulting motion artifacts. However, advances in MRI technology help to mitigate such drawbacks, enabling the acquisition of high spatiotemporal resolution images with a variety of contrast mechanisms. This review aims to classify the MRI techniques used to date in clinical and preclinical ophthalmologic studies, describing the qualitative and quantitative information that may be extracted and how this may inform on ocular pathophysiology.
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Affiliation(s)
- Laura Fanea
- Department of Biomedical Physics, Physics Faculty, Babes-Bolyai University, Cluj-Napoca, Romania,Department of Radiology, Cluj County Emergency Hospital, Cluj-Napoca, Romania
| | - Andrew J. Fagan
- Centre for Advanced Medical Imaging, St. James’s Hospital Dublin / University of Dublin Trinity College, Ireland
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16
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Smith CA, Newson TA, Leonard KC, Barfett J, Holdsworth DW, Hutnik CML, Hill KA. A framework for modeling ocular drug transport and flow through the eye using micro-CT. Phys Med Biol 2012; 57:6295-307. [PMID: 22982646 DOI: 10.1088/0031-9155/57/19/6295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study uses micro-computed tomography (micro-CT) imaging for assessment of concentration and transport mechanisms of ocular drug surrogates following intravitreal injection. Injections of an iodinated contrast agent were administered to enucleated porcine eyes prior to scanning over 192 min. Image analysis was performed using signal profiles and regions of interest that corresponded to specific iodine concentrations. Diffusion coefficients of the injected iodine solutions were calculated using nonlinear regression analysis with a diffusion model. There was a predominantly diffusive component in the movement of the contrast to the back of the eye in the horizontal (sagittal & coronal) directions, with ultimate retinal fate observed after 120 min. The diffusion coefficients were found to have a mean of 4.87 × 10(-4) mm(2) s(-1) and standard deviation of 8.39 × 10(-5) mm(2) s(-1) for 150 mg ml(-1) iodine concentration and 6.13 × 10(-4) ± 1.83 × 10(-4) mm(2) s(-1) for 37.5 mg ml(-1) concentration. However, it should be noted that these coefficients were time dependent and were found to decay as the diffusion front interacted with the retinal wall. A real-time, accurate, non-invasive method of tracking a bolus and its concentration is achieved using a high spatial resolution and fast scanning speed micro-CT system.
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Affiliation(s)
- Corey A Smith
- Department of Biology, The University of Western Ontario, London, Ontario, Canada
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17
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Occhiutto ML, Freitas FR, Maranhao RC, Costa VP. Breakdown of the blood-ocular barrier as a strategy for the systemic use of nanosystems. Pharmaceutics 2012; 4:252-75. [PMID: 24300231 PMCID: PMC3834913 DOI: 10.3390/pharmaceutics4020252] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 04/17/2012] [Accepted: 05/05/2012] [Indexed: 12/14/2022] Open
Abstract
Several drug delivery systems have been proposed to overcome physiological barriers, improving ocular bioavailability. Systemic routes are seldom used due to the blood-ocular barrier. Novel drug delivery systems based on nanotechnology techniques have been developed to overcome ocular physiological barriers. This non-systematic review suggests the utilization of a transitory blood-ocular breakdown to allow the access of drugs by nanotechnology drug delivery systems via the systemic route. We discuss the possible ways to cause the breakdown of the blood-ocular barrier: acute inflammation caused by intraocular surgery, induced ocular hypotony, and the use of inflammatory mediators. The suitability of use of the systemic route and its toxic effects are also discussed in this article.
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Affiliation(s)
- Marcelo L. Occhiutto
- Heart Institute, Medical School Hospital, University of São Paulo, São Paulo 05403-000, Brazil; (M.L.O.); (F.R.F.); (R.C.M.)
| | - Fatima R. Freitas
- Heart Institute, Medical School Hospital, University of São Paulo, São Paulo 05403-000, Brazil; (M.L.O.); (F.R.F.); (R.C.M.)
| | - Raul C. Maranhao
- Heart Institute, Medical School Hospital, University of São Paulo, São Paulo 05403-000, Brazil; (M.L.O.); (F.R.F.); (R.C.M.)
- Faculty of Pharmaceutical Science, University of São Paulo, São Paulo 05508-000, Brazil
| | - Vital P. Costa
- Department of Ophthalmology, University of Campinas, Campinas, São Paulo 13083-887, Brazil
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Li SK, Hao J, Liu H, Lee JH. MRI study of subconjunctival and intravitreal injections. J Pharm Sci 2012; 101:2353-63. [PMID: 22473517 DOI: 10.1002/jps.23127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 02/21/2012] [Accepted: 03/01/2012] [Indexed: 11/06/2022]
Abstract
Previous magnetic resonance imaging (MRI) studies to investigate the routes of penetration and barriers in ocular delivery have provided insights into the mechanisms of transscleral and intraocular drug delivery. The objective of the present study was to investigate ocular penetration and clearance after subconjunctival and intravitreal injections using a contrast agent at concentrations higher than those in the previous studies. This high concentration approach was hypothesized to allow the visualization of the contrast agent in the eye that could not be achieved previously. Subconjunctival and intravitreal injections of contrast agent Magnevist, a model hydrophililc probe, were performed in rabbits, and the distribution and clearance of the probe after the injections were examined by MRI. After subconjunctival injection in vivo, significant contrast agent penetration into the anterior chamber was observed but not into the vitreous. A clearance pathway of the hydrophilic probe from the subconjunctival depot to the regions near the periocular fat behind the eye was found. After intravitreal injection in vivo, the contrast agent was observed in the anterior chamber, optic nerve, and tissues surrounding the eye during clearance. MRI continues to provide insights into the transport barriers and clearance pathways of hydrophilic molecules in ocular delivery.
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Affiliation(s)
- S Kevin Li
- Division of Pharmaceutical Sciences, James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio 45267, USA.
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Berezovsky DE, Patel SR, McCarey BE, Edelhauser HF. In vivo ocular fluorophotometry: delivery of fluoresceinated dextrans via transscleral diffusion in rabbits. Invest Ophthalmol Vis Sci 2011; 52:7038-45. [PMID: 21791594 DOI: 10.1167/iovs.11-7207] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To evaluate the transscleral delivery of fluoresceinated dextrans (FITC-D) with molecular mass up to 70 kDa to the rabbit posterior segment using sub-Tenon injections. METHODS Eighteen NZW rabbits received a unilateral 200-μL injection of 2 mg/mL sodium fluorescein (NaF), 25 mg/mL 40-kDa FITC-D, or 25 mg/mL 70-kDa FITC-D, with (n = 9) or without (n = 9) immediate euthanatization. In live animals, fluorescence was measured in the retina/choroid and mid-vitreous by fluorophotometry, immediately after injection and after 4, 24, 48, and 72 hours. Euthanatized animals were examined hourly through 5 or 6 hours. RESULTS In live animals, the average peak NaF concentration in the retina/choroid was 310.2 ng/mL, measured 3 hours after injection. Average 40- and 70-kDa FITC-D concentrations in the retina/choroid peaked at 5409.6 and 2375.6 ng/mL, respectively, 24 hours after injection. Fluorescence returned to baseline levels 6 hours after NaF injection, and 48 and 72 hours after 40- and 70-kDa FITC-D injections, respectively. Rabbits that received NaF followed by euthanatization exhibited a continuous increase in retina/choroid and mid-vitreous fluorescence, beginning 1 hour after injection, whereas FITC-D-injected eyes did not show elevated retina/choroid or mid-vitreous fluorescence through 6 hours. CONCLUSIONS FITC-D weighing up to 70-kDa, as well as NaF, reached the posterior retina/choroid after sub-Tenon injections in live rabbits. NaF and 40-kDa FITC-D reached higher peak concentrations and were cleared from the eye more rapidly than was 70-kDa FITC-D. There was minimal penetration of NaF and FITC-D into the mid-vitreous in the in vivo experiments.
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20
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Shi X, Liu X, Wu X, Lu ZR, Li SK, Jeong EK. Ocular pharmacokinetic study using T₁ mapping and Gd-chelate- labeled polymers. Pharm Res 2011; 28:3180-8. [PMID: 21691891 DOI: 10.1007/s11095-011-0507-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 06/01/2011] [Indexed: 10/18/2022]
Abstract
PURPOSE Recent advances in drug discovery have led to the development of a number of therapeutic macromolecules for treatment of posterior eye diseases. We aimed to investigate the clearance of macromolecular contrast probes (polymers conjugated with Gd-chelate) in the vitreous after intravitreal injections with the recently developed ms-DSEPI-T12 MRI and to examine the degradation of disulfide-containing biodegradable polymers in the vitreous humor in vivo. METHODS Intravitreal injections of model contrast agents poly[N-(2-hydroxypropyl)methacrylamide]-GG-1,6-hexanediamine-(Gd-DO3A), biodegradable (Gd-DTPA)-cystine copolymers, and MultiHance were performed in rabbits; their distribution and elimination from the vitreous after injections were determined by MRI. RESULTS Times for macromolecular contrast agents to decrease to half their initial concentrations in the vitreous ranged from 0.4-1.3 days post-injection. Non-biodegradable polymers demonstrated slower vitreal clearance than those of disulfide-biodegradable polymers. Biodegradable polymers had similar clearance as MultiHance. CONCLUSIONS Usefulness of T(1) mapping and ms-DSEPI-T12 MRI to study ocular pharmacokinetics was demonstrated. Results suggest an enzymatic degradation mechanism for the disulfide linkage in polymers in the vitreous leading to breakup of polymers in vitreous humor over time.
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Affiliation(s)
- Xianfeng Shi
- Department of Radiology Utah Center for Advanced Imaging Research, University of Utah, 729 Arapeen Dr., Salt Lake City, Utah 84108, USA
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Is It Possible to Anesthetize Palatal Tissues With Buccal 4% Articaine Injection? J Oral Maxillofac Surg 2010; 68:1032-7. [DOI: 10.1016/j.joms.2009.12.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2009] [Revised: 09/25/2009] [Accepted: 12/29/2009] [Indexed: 11/19/2022]
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GD-DTPA enhanced MRI of ocular transport in a rat model of chronic glaucoma. Exp Eye Res 2008; 87:334-41. [DOI: 10.1016/j.exer.2008.06.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Revised: 06/10/2008] [Accepted: 06/23/2008] [Indexed: 11/21/2022]
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