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Babu B, Stoltz SA, Mittal A, Pawar S, Kolanthai E, Coathup M, Seal S. Inorganic Nanoparticles as Radiosensitizers for Cancer Treatment. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2873. [PMID: 37947718 PMCID: PMC10647410 DOI: 10.3390/nano13212873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 10/25/2023] [Accepted: 10/27/2023] [Indexed: 11/12/2023]
Abstract
Nanotechnology has expanded what can be achieved in our approach to cancer treatment. The ability to produce and engineer functional nanoparticle formulations to elicit higher incidences of tumor cell radiolysis has resulted in substantial improvements in cancer cell eradication while also permitting multi-modal biomedical functionalities. These radiosensitive nanomaterials utilize material characteristics, such as radio-blocking/absorbing high-Z atomic number elements, to mediate localized effects from therapeutic irradiation. These materials thereby allow subsequent scattered or emitted radiation to produce direct (e.g., damage to genetic materials) or indirect (e.g., protein oxidation, reactive oxygen species formation) damage to tumor cells. Using nanomaterials that activate under certain physiologic conditions, such as the tumor microenvironment, can selectively target tumor cells. These characteristics, combined with biological interactions that can target the tumor environment, allow for localized radio-sensitization while mitigating damage to healthy cells. This review explores the various nanomaterial formulations utilized in cancer radiosensitivity research. Emphasis on inorganic nanomaterials showcases the specific material characteristics that enable higher incidences of radiation while ensuring localized cancer targeting based on tumor microenvironment activation. The aim of this review is to guide future research in cancer radiosensitization using nanomaterial formulations and to detail common approaches to its treatment, as well as their relations to commonly implemented radiotherapy techniques.
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Affiliation(s)
- Balaashwin Babu
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
| | - Samantha Archer Stoltz
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Agastya Mittal
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Shreya Pawar
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Elayaraja Kolanthai
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
| | - Melanie Coathup
- Biionix Cluster, University of Central Florida, Orlando, FL 32827, USA;
- College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Sudipta Seal
- Advanced Materials Processing and Analysis Center, Department of Materials Science and Engineering, University of Central Florida, Orlando, FL 32826, USA; (B.B.); (S.A.S.); (A.M.); (S.P.); (E.K.)
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
- College of Medicine, University of Central Florida, Orlando, FL 32827, USA
- Nanoscience Technology Center, University of Central Florida, Orlando, FL, USA
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Klein JS, Kim TJ, Pratx G. Development of a Lensless Radiomicroscope for Cellular-Resolution Radionuclide Imaging. J Nucl Med 2023; 64:479-484. [PMID: 36109183 PMCID: PMC10071797 DOI: 10.2967/jnumed.122.264021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 09/08/2022] [Accepted: 09/08/2022] [Indexed: 11/16/2022] Open
Abstract
The action of radiopharmaceuticals takes place at the level of cells. However, existing radionuclide assays can only measure uptake in bulk or in small populations of single cells. This potentially hinders the development of effective radiopharmaceuticals for disease detection, staging, and treatment. Methods: We have developed a new imaging modality, the lensless radiomicroscope (LRM), for in vitro, cellular-resolution imaging of β- and α-emitting radionuclides. The palm-sized instrument is constructed from off-the-shelf parts for a total cost of less than $100, about 500 times less than the radioluminescence microscope, its closest equivalent. The instrument images radiopharmaceuticals by direct detection of ionizing charged particles via a consumer-grade complementary metal-oxide semiconductor detector. Results: The LRM can simultaneously image more than 5,000 cells within its 1 cm2 field of view, a 100-times increase over state-of-the-art technology. It has spatial resolution of 5 μm for brightfield imaging and 30 μm for 18F positron imaging. We used the LRM to quantify 18F-FDG uptake in MDA-MB-231 breast cancer cells 72 h after radiation treatment. Cells receiving 3 Gy were 3 times larger (mean = 3,116 μm2) than their untreated counterparts (mean = 940 μm2) but had 2 times less 18F-FDG per area (mean = 217 Bq/mm2), a finding in agreement with the clinical use of this tracer to monitor response. Additionally, the LRM was used to dynamically image the uptake of 18F-FDG by live cancer cells, and thus measure their avidity for glucose. Conclusion: The LRM is a high-resolution, large-field-of-view, and cost-effective approach to image radiotracer uptake with single-cell resolution in vitro.
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Affiliation(s)
- Justin S Klein
- Department of Radiation Oncology, Stanford University, Stanford, California
| | - Tae Jin Kim
- Department of Radiation Oncology, Stanford University, Stanford, California
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University, Stanford, California
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3
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Gawne PJ, Man F, Blower PJ, T M de Rosales R. Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging. Chem Rev 2022; 122:10266-10318. [PMID: 35549242 PMCID: PMC9185691 DOI: 10.1021/acs.chemrev.1c00767] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.
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Affiliation(s)
- Peter J Gawne
- School of Biomedical Engineering & Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, U.K
| | - Francis Man
- School of Biomedical Engineering & Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, U.K.,Institute of Pharmaceutical Science, School of Cancer and Pharmaceutical Sciences, King's College London, London, SE1 9NH, U.K
| | - Philip J Blower
- School of Biomedical Engineering & Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, U.K
| | - Rafael T M de Rosales
- School of Biomedical Engineering & Imaging Sciences, King's College London, St Thomas' Hospital, London, SE1 7EH, U.K
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Ha B, Kim TJ, Moon E, Giaccia AJ, Pratx G. Flow radiocytometry using droplet optofluidics. Biosens Bioelectron 2021; 194:113565. [PMID: 34492500 PMCID: PMC8530933 DOI: 10.1016/j.bios.2021.113565] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 07/22/2021] [Accepted: 08/11/2021] [Indexed: 11/29/2022]
Abstract
Flow-based cytometry methods are widely used to analyze heterogeneous cell populations. However, their use for small molecule studies remains limited due to bulky fluorescent labels that often interfere with biochemical activity in cells. In contrast, radiotracers require minimal modification of their target molecules and can track biochemical processes with negligible interference and high specificity. Here, we introduce flow radiocytometry (FRCM) that broadens the scope of current cytometry methods to include beta-emitting radiotracers as probes for single cell studies. FRCM uses droplet microfluidics and radiofluorogenesis to translate the radioactivity of single cells into a fluorescent signal that is then read out using a high-throughput optofluidic device. As a proof of concept, we quantitated [18F]fluorodeoxyglucose radiotracer uptake in single human breast cancer cells and successfully assessed the metabolic flux of glucose and its heterogeneity at the cellular level. We believe FRCM has potential applications ranging from analytical assays for cancer and other diseases to development of small-molecule drugs.
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Affiliation(s)
- Byunghang Ha
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-5847, USA; Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305-3011, USA.
| | - Tae Jin Kim
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-5847, USA
| | - Ejung Moon
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-5847, USA
| | - Amato J Giaccia
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-5847, USA
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94305-5847, USA.
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Kim TJ, Ha B, Bick AD, Kim M, Tang SK, Pratx G. Microfluidics-Coupled Radioluminescence Microscopy for In Vitro Radiotracer Kinetic Studies. Anal Chem 2021; 93:4425-4433. [PMID: 33647202 PMCID: PMC8006742 DOI: 10.1021/acs.analchem.0c04321] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Integrated bioassay systems that combine microfluidics and radiation detectors can deliver medical radiopharmaceuticals to live cells with precise timing, while minimizing radiation dose and sample volume. However, the spatial resolution of many radiation imaging systems is limited to bulk cell populations. Here, we demonstrate microfluidics-coupled radioluminescence microscopy (μF-RLM), a new integrated system that can image radiotracer uptake in live adherent cells growing inside microincubators with spatial resolution better than 30 μm. Our method enables on-chip radionuclide imaging by incorporating an inorganic scintillator plate (CdWO4) into a microfluidic chip. We apply this approach to investigate the factors that influence the dynamic uptake of [18F]fluorodeoxyglucose (FDG) by cancer cells. In the first experiment, we measured the effect of flow on FDG uptake of cells and found that a continuous flow of the radiotracer led to fourfold higher uptake than static incubation, suggesting that convective replenishment enhances molecular radiotracer transport into cells. In the second set of experiments, we applied pharmacokinetic modeling to show that lactic acidosis inhibits FDG uptake by cancer cells in vitro and that this decrease is primarily due to downregulation of FDG transport into the cells. The other two rate constants, which represent FDG export and FDG metabolism, were relatively unaffected by lactic acidosis. Lactic acidosis is common in solid tumors because of the dysregulated metabolism and inefficient vasculature. In conclusion, μF-RLM is a simple and practical approach for integrating high-resolution radionuclide imaging within standard microfluidics devices, thus potentially opening venues for investigating the efficacy of radiopharmaceuticals in in vitro cancer models.
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Affiliation(s)
- Tae Jin Kim
- Division of Medical Physics, Department of Radiation Oncology, Stanford University, 300 Pasteur Dr., Stanford, CA 94305, USA
| | - Byunghang Ha
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305, USA
| | - Alison Dana Bick
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305, USA
| | - Minkyu Kim
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305, USA
| | - Sindy K.Y. Tang
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305, USA
| | - Guillem Pratx
- Division of Medical Physics, Department of Radiation Oncology, Stanford University, 300 Pasteur Dr., Stanford, CA 94305, USA
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Kim TJ, Wang Q, Shelor M, Pratx G. Single-cell radioluminescence microscopy with two-fold higher sensitivity using dual scintillator configuration. PLoS One 2020; 15:e0221241. [PMID: 32634153 PMCID: PMC7340323 DOI: 10.1371/journal.pone.0221241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 06/21/2020] [Indexed: 11/25/2022] Open
Abstract
Radioluminescence microscopy (RLM) is an imaging technique that allows quantitative analysis of clinical radiolabeled drugs and probes in single cells. However, the modality suffers from slow data acquisition (15–30 minutes), thus critically affecting experiments with short-lived radioactive drugs. To overcome this issue, we suggest an approach that significantly accelerates data collection. Instead of using a single scintillator to image the decay of radioactive molecules, we sandwiched the radiolabeled cells between two scintillators. As proof of concept, we imaged cells labeled with [18F]FDG, a radioactive glucose popularly used in oncology to image tumors. Results show that the double scintillator configuration increases the microscope sensitivity by two-fold, thus reducing the image acquisition time by half to achieve the same result as the single scintillator approach. The experimental results were also compared with Geant4 Monte Carlo simulation to confirm the two-fold increase in sensitivity with only minor degradation in spatial resolution. Overall, these findings suggest that the double scintillator configuration can be used to perform time-sensitive studies such as cell pharmacokinetics or cell uptake of short-lived radiotracers.
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Affiliation(s)
- Tae Jin Kim
- Department of Radiation Oncology, Stanford School of Medicine, Stanford, California, United States of America
- * E-mail:
| | - Qian Wang
- Department of Bioengineering, University of California, Davis, California, United States of America
| | - Mark Shelor
- Department of Biomedical Engineering, University of California, Merced, California, United States of America
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford School of Medicine, Stanford, California, United States of America
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7
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Liu Z, Lan X. Microfluidic radiobioassays: a radiometric detection tool for understanding cellular physiology and pharmacokinetics. LAB ON A CHIP 2019; 19:2315-2339. [PMID: 31222194 DOI: 10.1039/c9lc00159j] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The investigation of molecular uptake and its kinetics in cells is valuable for understanding the cellular physiological status, the observation of drug interventions, and the development of imaging agents and pharmaceuticals. Microfluidic radiobioassays, or microfluidic radiometric bioassays, constitute a radiometric imaging-on-a-chip technology for the assay of biological samples using radiotracers. From 2006 to date, microfluidic radiobioassays have shown advantages in many applications, including radiotracer characterization, enzyme activity radiobioassays, fast drug evaluation, single-cell imaging, facilitation of dynamic positron emission tomography (PET) imaging, and cellular pharmacokinetics (PK)/pharmacodynamics (PD) studies. These advantages lie in the minimized and integrated detection scheme, allowing real-time tracking of dynamic uptake, high sensitivity radiotracer imaging, and quantitative interpretation of imaging results. In this review, the basics of radiotracers, various radiometric detection methods, and applications of microfluidic radiobioassays will be introduced and summarized, and the potential applications and future directions of microfluidic radiobioassays will be forecasted.
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Affiliation(s)
- Zhen Liu
- Department of Nuclear Medicine, Wuhan Union Hospital, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, No. 1277 Jiefang Ave, Wuhan, Hubei Province 430022, China.
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8
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Radioluminescence Microscopy: A Quantitative Method for Radioisotopic Imaging of Metabolic Fluxes in Living Cancer Cells. Methods Mol Biol 2019. [PMID: 30725449 DOI: 10.1007/978-1-4939-9027-6_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Radionuclide imaging with cellular-scale resolution allows characterization of biological processes and metabolic fluxes in single live cells. In this protocol, we describe how to image radiotracer uptake with single-cell resolution and compare the method to conventional bulk-scale gamma counting. We describe the utility of both techniques, give examples where each technique is recommended, and provide detailed side-by-side instructions for both techniques.
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9
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Abstract
The electromagnetic spectrum contains different frequency bands useful for medical imaging and therapy. Short wavelengths (ionizing radiation) are commonly used for radiological and radionuclide imaging and for cancer radiation therapy. Intermediate wavelengths (optical radiation) are useful for more localized imaging and for photodynamic therapy (PDT). Finally, longer wavelengths are the basis for magnetic resonance imaging and for hyperthermia treatments. Recently, there has been a surge of interest for new biomedical methods that synergize optical and ionizing radiation by exploiting the ability of ionizing radiation to stimulate optical emissions. These physical phenomena, together known as radioluminescence, are being used for applications as diverse as radionuclide imaging, radiation therapy monitoring, phototherapy, and nanoparticle-based molecular imaging. This review provides a comprehensive treatment of the physics of radioluminescence and includes simple analytical models to estimate the luminescence yield of scintillators and nanoscintillators, Cherenkov radiation, air fluorescence, and biologically endogenous radioluminescence. Examples of methods that use radioluminescence for diagnostic or therapeutic applications are reviewed and analyzed in light of these quantitative physical models of radioluminescence.
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Affiliation(s)
- Justin Klein
- Department of Radiation Oncology, Stanford University, Stanford, CA 94305
| | - Conroy Sun
- College of Pharmacy, Oregon State University, Portland, OR 97201
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University, Stanford, CA 94305
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Kiru L, Kim TJ, Shen B, Chin FT, Pratx G. Single-Cell Imaging Using Radioluminescence Microscopy Reveals Unexpected Binding Target for [18F]HFB. Mol Imaging Biol 2019; 20:378-387. [PMID: 29143174 DOI: 10.1007/s11307-017-1144-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
PURPOSE Cell-based therapies are showing great promise for a variety of diseases, but remain hindered by the limited information available regarding the biological fate, migration routes and differentiation patterns of infused cells in trials. Previous studies have demonstrated the feasibility of using positron emission tomography (PET) to track single cells utilising an approach known as positron emission particle tracking (PEPT). The radiolabel hexadecyl-4-[18F]fluorobenzoate ([18F]HFB) was identified as a promising candidate for PEPT, due to its efficient and long-lasting labelling capabilities. The purpose of this work was to characterise the labelling efficiency of [18F]HFB in vitro at the single-cell level prior to in vivo studies. PROCEDURES The binding efficiency of [18F]HFB to MDA-MB-231 and Jurkat cells was verified in vitro using bulk gamma counting. The measurements were subsequently repeated in single cells using a new method known as radioluminescence microscopy (RLM) and binding of the radiolabel to the single cells was correlated with various fluorescent dyes. RESULTS Similar to previous reports, bulk cell labelling was significantly higher with [18F]HFB (18.75 ± 2.47 dpm/cell, n = 6) than 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) (7.59 ± 0.73 dpm/cell, n = 7; p ≤ 0.01). However, single-cell imaging using RLM revealed that [18F]HFB accumulation in live cells (8.35 ± 1.48 cpm/cell, n = 9) was not significantly higher than background levels (4.83 ± 0.52 cpm/cell, n = 12; p > 0.05) and was 1.7-fold lower than [18F]FDG uptake in the same cell line (14.09 ± 1.90 cpm/cell, n = 13; p < 0.01). Instead, [18F]HFB was found to bind significantly to fragmented membranes associated with dead cell nuclei, suggesting an alternative binding target for [18F]HFB. CONCLUSION This study demonstrates that bulk analysis alone does not always accurately portray the labelling efficiency, therefore highlighting the need for more routine screening of radiolabels using RLM to identify heterogeneity at the single-cell level.
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Affiliation(s)
- Louise Kiru
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Tae Jin Kim
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Bin Shen
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Frederick T Chin
- Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA.
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Sengupta D, Kim TJ, Almasi S, Miller S, Marton Z, Nagarkar V, Pratx G. Development and characterization of a scintillating cell imaging dish for radioluminescence microscopy. Analyst 2018; 143:1862-1869. [PMID: 29543293 PMCID: PMC6035884 DOI: 10.1039/c8an00106e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Radioluminescence microscopy is an emerging modality that can be used to image radionuclide probes with micron-scale resolution. This technique is particularly useful as a way to probe the metabolic behavior of single cells and to screen and characterize radiopharmaceuticals, but the quality of the images is critically dependent on the scintillator material used to image the cells. In this paper, we detail the development of a microscopy dish made of a thin-film scintillating material, Lu2O3:Eu, that could be used as the blueprint for a future consumable product. After developing a simple quality control method based on long-lived alpha and beta sources, we characterize the radioluminescence properties of various thin-film scintillator samples. We find consistent performance for most samples, but also identify a few samples that do not meet the specifications, thus stressing the need for routine quality control prior to biological experiments. In addition, we test and quantify the transparency of the material, and demonstrate that transparency correlates with thickness. Finally, we evaluate the biocompatibility of the material and show that the microscopy dish can produce radioluminescent images of live single cells.
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Affiliation(s)
- Debanti Sengupta
- Radiation Oncology, Stanford University, 300 Pasteur Dr, Stanford, California, USA.
| | - Tae Jin Kim
- Radiation Oncology, Stanford University, 300 Pasteur Dr, Stanford, California, USA.
| | - Sepideh Almasi
- Radiation Oncology, Stanford University, 300 Pasteur Dr, Stanford, California, USA.
| | - Stuart Miller
- Radiation Monitoring Devices Inc, Watertown, Massachusetts, USA
| | - Zsolt Marton
- Radiation Monitoring Devices Inc, Watertown, Massachusetts, USA
| | - Vivek Nagarkar
- Radiation Monitoring Devices Inc, Watertown, Massachusetts, USA
| | - Guillem Pratx
- Radiation Oncology, Stanford University, 300 Pasteur Dr, Stanford, California, USA.
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Wang Q, Sengupta D, Kim TJ, Pratx G. In silico optimization of radioluminescence microscopy. JOURNAL OF BIOPHOTONICS 2018; 11:10.1002/jbio.201700138. [PMID: 28945305 PMCID: PMC5839938 DOI: 10.1002/jbio.201700138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Revised: 09/19/2017] [Accepted: 09/21/2017] [Indexed: 06/07/2023]
Abstract
Radioluminescence microscopy (RLM) is a high-resolution method for imaging radionuclide uptake in live cells within a fluorescence microscopy environment. Although RLM currently provides sufficient spatial resolution and sensitivity for cell imaging, it has not been systematically optimized. This study seeks to optimize the parameters of the system by computational simulation using a combination of numerical models for the system's various components: Monte-Carlo simulation for radiation transport, 3D optical point-spread function for the microscope, and stochastic photosensor model for the electron multiplying charge coupled device (EMCCD) camera. The relationship between key parameters and performance metrics relevant to image quality is examined. Results show that Lu2 O3 :Eu yields the best performance among 5 different scintillator materials, and a thickness: 8 μm can best balance spatial resolution and sensitivity. For this configuration, a spatial resolution of ~20 μm and sensitivity of 40% can be achieved for all 3 magnifications investigated, provided that the user adjusts pixel binning and electron multiplying (EM) gain accordingly. Hence the primary consideration for selecting the magnification should be the desired field of view and magnification for concurrent optical microscopy studies. In conclusion, this study estimates the optimal imaging performance achievable with RLM and promotes further development for more robust imaging of cellular processes using radiotracers.
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Affiliation(s)
- Qian Wang
- Department of Radiation Oncology, Stanford University, California
94305, United States
| | - Debanti Sengupta
- Department of Radiation Oncology, Stanford University, California
94305, United States
| | - Tae Jin Kim
- Department of Radiation Oncology, Stanford University, California
94305, United States
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University, California
94305, United States
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Gallina ME, Kim TJ, Shelor M, Vasquez J, Mongersun A, Kim M, Tang SKY, Abbyad P, Pratx G. Toward a Droplet-Based Single-Cell Radiometric Assay. Anal Chem 2017; 89:6472-6481. [PMID: 28562033 PMCID: PMC5480233 DOI: 10.1021/acs.analchem.7b00414] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
![]()
Radiotracers are
widely used to track molecular processes, both in vitro and in vivo, with high sensitivity
and specificity. However, most radionuclide detection methods have
spatial resolution inadequate for single-cell analysis. A few existing
methods can extract single-cell information from radioactive decays,
but the stochastic nature of the process precludes high-throughput
measurement (and sorting) of single cells. In this work, we introduce
a new concept for translating radioactive decays occurring stochastically
within radiolabeled single-cells into an integrated, long-lasting
fluorescence signal. Single cells are encapsulated in radiofluorogenic
droplets containing molecular probes sensitive to byproducts of ionizing
radiation (primarily reactive oxygen species, or ROS). Different probes
were examined in bulk solutions, and dihydrorhodamine 123 (DHRh 123)
was selected as the lead candidate due to its sensitivity and reproducibility.
Fluorescence intensity of DHRh 123 in bulk increased at a rate of
54% per Gy of X-ray radiation and 15% per MBq/ml of 2-deoxy-2-[18F]-fluoro-d-glucose ([18F]FDG). Fluorescence
imaging of microfluidic droplets showed the same linear response,
but droplets were less sensitive overall than the bulk ROS sensor
(detection limit of 3 Gy per droplet). Finally, droplets encapsulating
radiolabeled cancer cells allowed, for the first time, the detection
of [18F]FDG radiotracer uptake in single cells through
fluorescence activation. With further improvements, we expect this
technology to enable quantitative measurement and selective sorting
of single cells based on the uptake of radiolabeled small molecules.
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Affiliation(s)
- Maria Elena Gallina
- Division of Medical Physics, Department of Radiation Oncology, Stanford University , 300 Pasteur Drive, Palo Alto, California 94305, United States
| | - Tae Jin Kim
- Division of Medical Physics, Department of Radiation Oncology, Stanford University , 300 Pasteur Drive, Palo Alto, California 94305, United States
| | - Mark Shelor
- University of California-Merced , Department of Bioengineering, 5200 North Lake Road, Merced, California 95343, United States
| | - Jaime Vasquez
- University of California-San Francisco , School of Pharmacy, 600 16th Street, San Francisco, California, 94158, United States
| | - Amy Mongersun
- Department of Chemistry and Biochemistry, Santa Clara University , Daly Science 123500 El Camino Real, Santa Clara, California 95053, United States
| | - Minkyu Kim
- Department of Mechanical Engineering, Stanford University , 418 Panama Mall, Stanford, California 94305, United States
| | - Sindy K Y Tang
- Department of Mechanical Engineering, Stanford University , 418 Panama Mall, Stanford, California 94305, United States
| | - Paul Abbyad
- Department of Chemistry and Biochemistry, Santa Clara University , Daly Science 123500 El Camino Real, Santa Clara, California 95053, United States
| | - Guillem Pratx
- Division of Medical Physics, Department of Radiation Oncology, Stanford University , 300 Pasteur Drive, Palo Alto, California 94305, United States
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14
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Kim TJ, Türkcan S, Pratx G. Modular low-light microscope for imaging cellular bioluminescence and radioluminescence. Nat Protoc 2017; 12:1055-1076. [PMID: 28426025 DOI: 10.1038/nprot.2017.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Low-light microscopy methods are receiving increased attention as new applications have emerged. One such application is to allow longitudinal imaging of light-sensitive cells with no phototoxicity and no photobleaching of fluorescent biomarkers. Another application is for imaging signals that are inherently dim and undetectable using standard microscopy techniques, such as bioluminescence, chemiluminescence or radioluminescence. In this protocol, we provide instructions on how to build a modular low-light microscope (1-4 d) by coupling two microscope objective lenses, back to back from each other, using standard optomechanical components. We also provide directions on how to image dim signals such as those of radioluminescence (1-1.5 h), bioluminescence (∼30 min) and low-excitation fluorescence (∼15 min). In particular, radioluminescence microscopy is explained in detail, as it is a newly developed technique that enables the study of small-molecule transport (e.g., radiolabeled drugs, metabolic precursors and nuclear medicine contrast agents) by single cells without perturbing endogenous biochemical processes. In this imaging technique, a scintillator crystal (e.g., CdWO4) is placed in close proximity to the radiolabeled cells, where it converts the radioactive decays into optical flashes detectable using a sensitive camera. Using the image reconstruction toolkit provided in this protocol, the flashes can be reconstructed to yield high-resolution images of the radiotracer distribution. With appropriate timing, the three aforementioned imaging modalities may be performed together on a population of live cells, allowing the user to perform parallel functional studies of cell heterogeneity at the single-cell level.
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Affiliation(s)
- Tae Jin Kim
- Department of Radiation Oncology, Division of Medical Physics, Stanford University School of Medicine, Palo Alto, California, USA
| | - Silvan Türkcan
- Department of Radiation Oncology, Division of Medical Physics, Stanford University School of Medicine, Palo Alto, California, USA
| | - Guillem Pratx
- Department of Radiation Oncology, Division of Medical Physics, Stanford University School of Medicine, Palo Alto, California, USA
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15
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Wang Q, Sengupta D, Kim TJ, Pratx G. Performance evaluation of 18 F radioluminescence microscopy using computational simulation. Med Phys 2017; 44:1782-1795. [PMID: 28273348 DOI: 10.1002/mp.12198] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 02/09/2017] [Accepted: 02/21/2017] [Indexed: 01/12/2023] Open
Abstract
PURPOSE Radioluminescence microscopy can visualize the distribution of beta-emitting radiotracers in live single cells with high resolution. Here, we perform a computational simulation of 18 F positron imaging using this modality to better understand how radioluminescence signals are formed and to assist in optimizing the experimental setup and image processing. METHODS First, the transport of charged particles through the cell and scintillator and the resulting scintillation is modeled using the GEANT4 Monte-Carlo simulation. Then, the propagation of the scintillation light through the microscope is modeled by a convolution with a depth-dependent point-spread function, which models the microscope response. Finally, the physical measurement of the scintillation light using an electron-multiplying charge-coupled device (EMCCD) camera is modeled using a stochastic numerical photosensor model, which accounts for various sources of noise. The simulated output of the EMCCD camera is further processed using our ORBIT image reconstruction methodology to evaluate the endpoint images. RESULTS The EMCCD camera model was validated against experimentally acquired images and the simulated noise, as measured by the standard deviation of a blank image, was found to be accurate within 2% of the actual detection. Furthermore, point source simulations found that a reconstructed spatial resolution of 18.5 μm can be achieved near the scintillator. As the source is moved away from the scintillator, spatial resolution degrades at a rate of 3.5 μm per μm distance. These results agree well with the experimentally measured spatial resolution of 30-40 μm (live cells). The simulation also shows that the system sensitivity is 26.5%, which is also consistent with our previous experiments. Finally, an image of a simulated sparse set of single cells is visually similar to the measured cell image. CONCLUSIONS Our simulation methodology agrees with experimental measurements taken with radioluminescence microscopy. This in silico approach can be used to guide further instrumentation developments and to provide a framework for improving image reconstruction.
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Affiliation(s)
- Qian Wang
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94304, USA
| | - Debanti Sengupta
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94304, USA
| | - Tae Jin Kim
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94304, USA
| | - Guillem Pratx
- Department of Radiation Oncology, Stanford University, Stanford, CA, 94304, USA
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16
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Shaffer TM, Drain CM, Grimm J. Optical Imaging of Ionizing Radiation from Clinical Sources. J Nucl Med 2016; 57:1661-1666. [PMID: 27688469 DOI: 10.2967/jnumed.116.178624] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 09/03/2016] [Indexed: 12/11/2022] Open
Abstract
Nuclear medicine uses ionizing radiation for both in vivo diagnosis and therapy. Ionizing radiation comes from a variety of sources, including x-rays, beam therapy, brachytherapy, and various injected radionuclides. Although PET and SPECT remain clinical mainstays, optical readouts of ionizing radiation offer numerous benefits and complement these standard techniques. Furthermore, for ionizing radiation sources that cannot be imaged using these standard techniques, optical imaging offers a unique imaging alternative. This article reviews optical imaging of both radionuclide- and beam-based ionizing radiation from high-energy photons and charged particles through mechanisms including radioluminescence, Cerenkov luminescence, and scintillation. Therapeutically, these visible photons have been combined with photodynamic therapeutic agents preclinically for increasing therapeutic response at depths difficult to reach with external light sources. Last, new microscopy methods that allow single-cell optical imaging of radionuclides are reviewed.
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Affiliation(s)
- Travis M Shaffer
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center, New York, New York.,Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.,Department of Chemistry, Hunter College of City University of New York, New York, New York.,Department of Chemistry, Graduate Center of City University of New York, New York, New York
| | - Charles Michael Drain
- Department of Chemistry, Hunter College of City University of New York, New York, New York.,Department of Chemistry, Graduate Center of City University of New York, New York, New York
| | - Jan Grimm
- Molecular Pharmacology Program, Memorial Sloan Kettering Cancer Center, New York, New York .,Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, New York.,Department of Pharmacology, Weill Cornell Medical College, New York, New York; and.,Department of Radiology, Weill Cornell Medical College, New York, New York
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