1
|
Xie X, Zhai J, Zhou X, Guo Z, Lo PC, Zhu G, Chan KWY, Yang M. Magnetic Particle Imaging: From Tracer Design to Biomedical Applications in Vasculature Abnormality. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2306450. [PMID: 37812831 DOI: 10.1002/adma.202306450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 09/14/2023] [Indexed: 10/11/2023]
Abstract
Magnetic particle imaging (MPI) is an emerging non-invasive tomographic technique based on the response of magnetic nanoparticles (MNPs) to oscillating drive fields at the center of a static magnetic gradient. In contrast to magnetic resonance imaging (MRI), which is driven by uniform magnetic fields and projects the anatomic information of the subjects, MPI directly tracks and quantifies MNPs in vivo without background signals. Moreover, it does not require radioactive tracers and has no limitations on imaging depth. This article first introduces the basic principles of MPI and important features of MNPs for imaging sensitivity, spatial resolution, and targeted biodistribution. The latest research aiming to optimize the performance of MPI tracers is reviewed based on their material composition, physical properties, and surface modifications. While the unique advantages of MPI have led to a series of promising biomedical applications, recent development of MPI in investigating vascular abnormalities in cardiovascular and cerebrovascular systems, and cancer are also discussed. Finally, recent progress and challenges in the clinical translation of MPI are discussed to provide possible directions for future research and development.
Collapse
Affiliation(s)
- Xulin Xie
- Department of Precision Diagnostic and Therapeutic Technology, City University of Hong Kong Shenzhen Futian Research Institute, Shenzhen, 518057, China
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
| | - Jiao Zhai
- Department of Precision Diagnostic and Therapeutic Technology, City University of Hong Kong Shenzhen Futian Research Institute, Shenzhen, 518057, China
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
| | - Xiaoyu Zhou
- Department of Precision Diagnostic and Therapeutic Technology, City University of Hong Kong Shenzhen Futian Research Institute, Shenzhen, 518057, China
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
| | - Zhengjun Guo
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
- Department of Oncology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, China
| | - Pui-Chi Lo
- Department of Precision Diagnostic and Therapeutic Technology, City University of Hong Kong Shenzhen Futian Research Institute, Shenzhen, 518057, China
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
| | - Guangyu Zhu
- Department of Chemistry, City University of Hong Kong, Hong Kong SAR, 999077, China
| | - Kannie W Y Chan
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong SAR, 999077, China
| | - Mengsu Yang
- Department of Precision Diagnostic and Therapeutic Technology, City University of Hong Kong Shenzhen Futian Research Institute, Shenzhen, 518057, China
- Department of Biomedical Sciences, and Tung Biomedical Sciences Centre, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, 999077, China
| |
Collapse
|
2
|
Akhtar N, Mohammed HA, Yusuf M, Al-Subaiyel A, Sulaiman GM, Khan RA. SPIONs Conjugate Supported Anticancer Drug Doxorubicin's Delivery: Current Status, Challenges, and Prospects. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3686. [PMID: 36296877 PMCID: PMC9611558 DOI: 10.3390/nano12203686] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 10/13/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Considerable efforts have been directed towards development of nano-structured carriers to overcome the limitations of anticancer drug, doxorubicin's, delivery to various cancer sites. The drug's severe toxicity to cardio and hepatic systems, low therapeutic outcomes, inappropriate dose-demands, metastatic and general resistance, together with non-selectivity of the drug have led to the development of superparamagnetic iron oxide nanoparticles (SPIONs)-based drug delivery modules. Nano-scale polymeric co-encapsulation of the drug, doxorubicin, with SPIONs, the SPIONs surface end-groups' cappings with small molecular entities, as well as structural modifications of the SPIONs' surface-located functional end-groups, to attach the doxorubicin, have been achieved through chemical bonding by conjugation and cross-linking of natural and synthetic polymers, attachments of SPIONs made directly to the non-polymeric entities, and attachments made through mediation of molecular-spacer as well as non-spacer mediated attachments of several types of chemical entities, together with the physico-chemical bondings of the moieties, e.g., peptides, proteins, antibodies, antigens, aptamers, glycoproteins, and enzymes, etc. to the SPIONs which are capable of targeting multiple kinds of cancerous sites, have provided stable and functional SPIONs-based nano-carriers suitable for the systemic, and in vitro deliveries, together with being suitable for other biomedical/biotechnical applications. Together with the SPIONs inherent properties, and ability to respond to magnetic resonance, fluorescence-directed, dual-module, and molecular-level tumor imaging; as well as multi-modular cancer cell targeting; magnetic-field-inducible drug-elution capacity, and the SPIONs' magnetometry-led feasibility to reach cancer action sites have made sensing, imaging, and drug and other payloads deliveries to cancerous sites for cancer treatment a viable option. Innovations in the preparation of SPIONs-based delivery modules, as biocompatible carriers; development of delivery route modalities; approaches to enhancing their drug delivery-cum-bioavailability have explicitly established the SPIONs' versatility for oncological theranostics and imaging. The current review outlines the development of various SPIONs-based nano-carriers for targeted doxorubicin delivery to different cancer sites through multiple methods, modalities, and materials, wherein high-potential nano-structured platforms have been conceptualized, developed, and tested for, both, in vivo and in vitro conditions. The current state of the knowledge in this arena have provided definite dose-control, site-specificity, stability, transport feasibility, and effective onsite drug de-loading, however, with certain limitations, and these shortcomings have opened the field for further advancements by identifying the bottlenecks, suggestive and plausible remediation, as well as more clear directions for future development.
Collapse
Affiliation(s)
- Naseem Akhtar
- Department of Pharmaceutics, College of Dentistry & Pharmacy, Buraydah Private Colleges, P.O. Box 31717, Buraydah 51418, Qassim, Saudi Arabia
| | - Hamdoon A. Mohammed
- Department of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, Qassim University, Buraydah 51452, Qassim, Saudi Arabia
| | - Mohammed Yusuf
- Department of Clinical Pharmacy, College of Pharmacy, Taif University, P.O. Box 11099, Taif 21944, Mecca, Saudi Arabia
| | - Amal Al-Subaiyel
- Department of Pharmaceutics, College of Pharmacy, Qassim University, Buraydah 51452, Qassim, Saudi Arabia
| | - Ghassan M. Sulaiman
- Division of Biotechnology, Department of Applied Sciences, University of Technology, Baghdad 10066, Iraq
| | - Riaz A. Khan
- Department of Medicinal Chemistry & Pharmacognosy, College of Pharmacy, Qassim University, Buraydah 51452, Qassim, Saudi Arabia
| |
Collapse
|
3
|
Lu C, Han L, Wang J, Wan J, Song G, Rao J. Engineering of magnetic nanoparticles as magnetic particle imaging tracers. Chem Soc Rev 2021; 50:8102-8146. [PMID: 34047311 DOI: 10.1039/d0cs00260g] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Magnetic particle imaging (MPI) has recently emerged as a promising non-invasive imaging technique because of its signal linearly propotional to the tracer mass, ability to generate positive contrast, low tissue background, unlimited tissue penetration depth, and lack of ionizing radiation. The sensitivity and resolution of MPI are highly dependent on the properties of magnetic nanoparticles (MNPs), and extensive research efforts have been focused on the design and synthesis of tracers. This review examines parameters that dictate the performance of MNPs, including size, shape, composition, surface property, crystallinity, the surrounding environment, and aggregation state to provide guidance for engineering MPI tracers with better performance. Finally, we discuss applications of MPI imaging and its challenges and perspectives in clinical translation.
Collapse
Affiliation(s)
- Chang Lu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.
| | - Linbo Han
- College of Health Science and Environmental Engineering, Shenzhen Technology University, Shenzhen 518118, P. R. China
| | - Joanna Wang
- Molecular Imaging Program at Stanford, Department of Radiology, Stanford University School of Medicine, 1201 Welch Road, Stanford, California 94305-5484, USA.
| | - Jiacheng Wan
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.
| | - Guosheng Song
- State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.
| | - Jianghong Rao
- Molecular Imaging Program at Stanford, Department of Radiology, Stanford University School of Medicine, 1201 Welch Road, Stanford, California 94305-5484, USA.
| |
Collapse
|
4
|
Crețu BEB, Dodi G, Shavandi A, Gardikiotis I, Șerban IL, Balan V. Imaging Constructs: The Rise of Iron Oxide Nanoparticles. Molecules 2021; 26:3437. [PMID: 34198906 PMCID: PMC8201099 DOI: 10.3390/molecules26113437] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 05/27/2021] [Accepted: 06/01/2021] [Indexed: 12/14/2022] Open
Abstract
Over the last decade, an important challenge in nanomedicine imaging has been the work to design multifunctional agents that can be detected by single and/or multimodal techniques. Among the broad spectrum of nanoscale materials being investigated for imaging use, iron oxide nanoparticles have gained significant attention due to their intrinsic magnetic properties, low toxicity, large magnetic moments, superparamagnetic behaviour and large surface area-the latter being a particular advantage in its conjunction with specific moieties, dye molecules, and imaging probes. Tracers-based nanoparticles are promising candidates, since they combine synergistic advantages for non-invasive, highly sensitive, high-resolution, and quantitative imaging on different modalities. This study represents an overview of current advancements in magnetic materials with clinical potential that will hopefully provide an effective system for diagnosis in the near future. Further exploration is still needed to reveal their potential as promising candidates from simple functionalization of metal oxide nanomaterials up to medical imaging.
Collapse
Affiliation(s)
- Bianca Elena-Beatrice Crețu
- Advanced Centre for Research-Development in Experimental Medicine, Grigore T. Popa University of Medicine and Pharmacy of Iasi, 700115 Iasi, Romania; (B.E.-B.C.); (I.G.)
| | - Gianina Dodi
- Advanced Centre for Research-Development in Experimental Medicine, Grigore T. Popa University of Medicine and Pharmacy of Iasi, 700115 Iasi, Romania; (B.E.-B.C.); (I.G.)
| | - Amin Shavandi
- BioMatter-Biomass Transformation Lab, École Polytechnique de Bruxelles, Université Libre de Bruxelles, 1050 Brussels, Belgium;
| | - Ioannis Gardikiotis
- Advanced Centre for Research-Development in Experimental Medicine, Grigore T. Popa University of Medicine and Pharmacy of Iasi, 700115 Iasi, Romania; (B.E.-B.C.); (I.G.)
| | - Ionela Lăcrămioara Șerban
- Physiology Department, Grigore T. Popa University of Medicine and Pharmacy of Iasi, 700115 Iasi, Romania;
| | - Vera Balan
- Faculty of Medical Bioengineering, Grigore T. Popa University of Medicine and Pharmacy of Iasi, 700115 Iasi, Romania;
| |
Collapse
|
5
|
Zheng X, Wang J, Rao J. The Chemistry in Surface Functionalization of Nanoparticles for Molecular Imaging. Mol Imaging 2021. [DOI: 10.1016/b978-0-12-816386-3.00021-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|
6
|
Theis-Bröhl K, Saini A, Wolff M, Dura JA, Maranville BB, Borchers JA. Self-Assembly of Magnetic Nanoparticles in Ferrofluids on Different Templates Investigated by Neutron Reflectometry. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1231. [PMID: 32599954 PMCID: PMC7353075 DOI: 10.3390/nano10061231] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 01/24/2023]
Abstract
In this article we review the process by which magnetite nanoparticles self-assemble onto solid surfaces. The focus is on neutron reflectometry studies providing information on the density and magnetization depth profiles of buried interfaces. Specific attention is given to the near-interface "wetting" layer and to examples of magnetite nanoparticles on a hydrophilic silicon crystal, one coated with (3-Aminopropyl)triethoxysilane, and finally, one with a magnetic film with out-of-plane magnetization.
Collapse
Affiliation(s)
- Katharina Theis-Bröhl
- University of Applied Sciences Bremerhaven, An der Karlstadt 8, 27568 Bremerhaven, Germany
| | - Apurve Saini
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden; (A.S.); (M.W.)
| | - Max Wolff
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden; (A.S.); (M.W.)
| | - Joseph A. Dura
- NIST Center for Neutron Research, 100 Bureau Drive, Gaithersburg, MD 20899-6102, USA; (J.A.D.); (B.B.M.); (J.A.B.)
| | - Brian B. Maranville
- NIST Center for Neutron Research, 100 Bureau Drive, Gaithersburg, MD 20899-6102, USA; (J.A.D.); (B.B.M.); (J.A.B.)
| | - Julie A. Borchers
- NIST Center for Neutron Research, 100 Bureau Drive, Gaithersburg, MD 20899-6102, USA; (J.A.D.); (B.B.M.); (J.A.B.)
| |
Collapse
|
7
|
Wang Q, Ma X, Liao H, Liang Z, Li F, Tian J, Ling D. Artificially Engineered Cubic Iron Oxide Nanoparticle as a High-Performance Magnetic Particle Imaging Tracer for Stem Cell Tracking. ACS NANO 2020; 14:2053-2062. [PMID: 31999433 DOI: 10.1021/acsnano.9b08660] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Stem cell therapies are increasingly recognized as the future direction of regenerative medicine, but the biological fate of the administrated stem cells remains a major concern for clinical translation, which calls for an approach to efficiently monitoring the stem cell behaviors in vivo. Magnetic particle imaging (MPI) is an emerging technology for cell tracking; however, its utility has been largely restricted due to the lack of optimal magnetic nanoparticle tracers. Herein, by controlled engineering of the size and shape of magnetic nanoparticles tailored to MPI physics theory, a specialized MPI tracer, based on cubic iron oxide nanoparticles with an edge length of 22 nm (CIONs-22), is developed. Due to the inherent lower proportion of disordered surface spins, CIONs-22 exhibit significantly larger saturation magnetization than that of spherical ones, while they possess similar saturation magnetization but smaller coercivity compared to larger-sized CIONs. These magnetic properties of CIONs-22 warrant high sensitivity and resolution of MPI. With their efficient cellular uptake, CIONs-22 exhibit superior MPI performance for stem cell labeling and tracking compared to the commercialized tracer Vivotrax. By virtue of these advantages, CIONs-22 enable real-time and prolonged monitoring of the spatiotemporal trajectory of stem cells transplanted to hindlimb ischemia mice, which demonstrates the great potential of CIONs-22 as MPI tracers to advance stem cell therapies.
Collapse
Affiliation(s)
- Qiyue Wang
- Institute of Pharmaceutics, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou , Zhejiang 310058 , China
| | - Xibo Ma
- CAS Key Laboratory of Molecular Imaging, The State Key Laboratory of Management and Control for Complex Systems , Institute of Automation, Chinese Academy of Sciences , Beijing 100190 , China
- CBSR & NLPR , Institute of Automation, Chinese Academy of Sciences , Beijing 100190 , China
| | - Hongwei Liao
- Institute of Pharmaceutics, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou , Zhejiang 310058 , China
| | - Zeyu Liang
- Institute of Pharmaceutics, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou , Zhejiang 310058 , China
| | - Fangyuan Li
- Institute of Pharmaceutics, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou , Zhejiang 310058 , China
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou 310058 , China
| | - Jie Tian
- CAS Key Laboratory of Molecular Imaging, The State Key Laboratory of Management and Control for Complex Systems , Institute of Automation, Chinese Academy of Sciences , Beijing 100190 , China
- Beijing Advanced Innovation Center for Big Data-Based Precision Medicine, School of Medicine , Beihang University , Beijing 100190 , China
| | - Daishun Ling
- Institute of Pharmaceutics, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou , Zhejiang 310058 , China
- Key Laboratory of Biomedical Engineering of the Ministry of Education, College of Biomedical Engineering & Instrument Science , Zhejiang University , Hangzhou , Zhejiang 310027 , China
- Hangzhou Institute of Innovative Medicine, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou 310058 , China
- Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences , Zhejiang University , Hangzhou 310058 , China
| |
Collapse
|
8
|
Wu LC, Zhang Y, Steinberg G, Qu H, Huang S, Cheng M, Bliss T, Du F, Rao J, Song G, Pisani L, Doyle T, Conolly S, Krishnan K, Grant G, Wintermark M. A Review of Magnetic Particle Imaging and Perspectives on Neuroimaging. AJNR Am J Neuroradiol 2019; 40:206-212. [PMID: 30655254 DOI: 10.3174/ajnr.a5896] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 07/06/2018] [Indexed: 12/14/2022]
Abstract
Magnetic particle imaging is an emerging tomographic technique with the potential for simultaneous high-resolution, high-sensitivity, and real-time imaging. Magnetic particle imaging is based on the unique behavior of superparamagnetic iron oxide nanoparticles modeled by the Langevin theory, with the ability to track and quantify nanoparticle concentrations without tissue background noise. It is a promising new imaging technique for multiple applications, including vascular and perfusion imaging, oncology imaging, cell tracking, inflammation imaging, and trauma imaging. In particular, many neuroimaging applications may be enabled and enhanced with magnetic particle imaging. In this review, we will provide an overview of magnetic particle imaging principles and implementation, current applications, promising neuroimaging applications, and practical considerations.
Collapse
Affiliation(s)
- L C Wu
- From the Departments of Bioengineering (L.C.W.)
| | - Y Zhang
- Radiology (Y.Z., H.Q., S.H., M.W.)
| | - G Steinberg
- Neurosurgery (G.S., M.C., T.B., F.D., G.G.).,Neuroradiology Section, Radiology (J.R., G.S., L.P.)
| | - H Qu
- Radiology (Y.Z., H.Q., S.H., M.W.)
| | - S Huang
- Radiology (Y.Z., H.Q., S.H., M.W.).,Chongqing Medical University (S.H.), Traditional Chinese Medicine College, Chongqing, China
| | - M Cheng
- Neurosurgery (G.S., M.C., T.B., F.D., G.G.)
| | - T Bliss
- Neurosurgery (G.S., M.C., T.B., F.D., G.G.)
| | - F Du
- Neurosurgery (G.S., M.C., T.B., F.D., G.G.)
| | - J Rao
- Neuroradiology Section, Radiology (J.R., G.S., L.P.)
| | - G Song
- From the Departments of Bioengineering (L.C.W.)
| | - L Pisani
- Neuroradiology Section, Radiology (J.R., G.S., L.P.)
| | - T Doyle
- Pediatrics (T.D.), Stanford University, Stanford, California
| | - S Conolly
- Department of Electrical Engineering and Computer Sciences (S.C.), University of California Berkeley, Berkeley, California
| | - K Krishnan
- Departments of Materials Sciences and Engineering and Physics (K.K.), University of Washington, Seattle, Washington
| | - G Grant
- Neurosurgery (G.S., M.C., T.B., F.D., G.G.)
| | | |
Collapse
|
9
|
Theis-Bröhl K, Vreeland EC, Gomez A, Huber DL, Saini A, Wolff M, Maranville BB, Brok E, Krycka KL, Dura JA, Borchers JA. Self-Assembled Layering of Magnetic Nanoparticles in a Ferrofluid on Silicon Surfaces. ACS APPLIED MATERIALS & INTERFACES 2018; 10:5050-5060. [PMID: 29299907 DOI: 10.1021/acsami.7b14849] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
This article describes the three-dimensional self-assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers. For layers in which the NPs are more free to rotate, the easy axis of the NP can readily orient along the field direction. In more dense packing, free rotation of the NPs is hampered, and the NP ensembles likely build up quasi-domain states to minimize energy, which leads to lower magnetization in those layers. Detailed analysis of polarized neutron reflectometry data together with model calculations of the arrangement of the NPs within the layers and input from small-angle scattering measurements provide full characterization of the core/shell NP dimensions, degree of chaining, arrangement of the NPs within the different layers, and magnetization depth profile.
Collapse
Affiliation(s)
| | - Erika C Vreeland
- Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
- Imagion Biosystems LLC , Albuquerque, New Mexico 87106, United States
| | - Andrew Gomez
- Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - Dale L Huber
- Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - Apurve Saini
- Division for Materials Physics, Uppsala University , 75120 Uppsala, Sweden
| | - Max Wolff
- Division for Materials Physics, Uppsala University , 75120 Uppsala, Sweden
| | - Brian B Maranville
- NIST Center for Neutron Research , 100 Bureau Drive, Gaithersburg 20899-6102, United States
| | - Erik Brok
- NIST Center for Neutron Research , 100 Bureau Drive, Gaithersburg 20899-6102, United States
- Department of Materials Science and Engineering, University of Maryland , College Park, Maryland 20742, United States
| | - Kathryn L Krycka
- NIST Center for Neutron Research , 100 Bureau Drive, Gaithersburg 20899-6102, United States
| | - Joseph A Dura
- NIST Center for Neutron Research , 100 Bureau Drive, Gaithersburg 20899-6102, United States
| | - Julie A Borchers
- NIST Center for Neutron Research , 100 Bureau Drive, Gaithersburg 20899-6102, United States
| |
Collapse
|
10
|
Arami H, Teeman E, Troksa A, Bradshaw H, Saatchi K, Tomitaka A, Gambhir SS, Häfeli UO, Liggitt D, Krishnan KM. Tomographic magnetic particle imaging of cancer targeted nanoparticles. NANOSCALE 2017; 9:18723-18730. [PMID: 29165498 PMCID: PMC6064607 DOI: 10.1039/c7nr05502a] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Magnetic Particle Imaging (MPI) is an emerging, whole body biomedical imaging technique, with sub-millimeter spatial resolution and high sensitivity to a biocompatible contrast agent consisting of an iron oxide nanoparticle core and a biofunctionalized shell. Successful application of MPI for imaging of cancer depends on the nanoparticles (NPs) accumulating at tumors at sufficient levels relative to other sites. NPs' physiochemical properties such as size, crystallographic structure and uniformity, surface coating, stability, blood circulation time and magnetization determine the efficacy of their tumor accumulation and MPI signal generation. Here, we address these criteria by presenting strategies for the synthesis and surface functionalization of efficient MPI tracers, that can target a typical murine brain cancer model and generate three dimensional images of these tumors with very high signal-to-noise ratios (SNR). Our results showed high contrast agent sensitivities that enabled us to detect 1.1 ng of iron (SNR ∼ 3.9) and enhance the spatial resolution to about 600 μm. The biodistribution of these NPs was also studied using near-infrared fluorescence (NIRF) and single-photon emission computed tomography (SPECT) imaging. NPs were mainly accumulated in the liver and spleen and did not show any renal clearance. This first pre-clinical study of cancer targeted NPs imaged using a tomographic MPI system in an animal model paves the way to explore new nanomedicine strategies for cancer diagnosis and therapy, using clinically safe magnetic iron oxide nanoparticles and MPI.
Collapse
Affiliation(s)
- Hamed Arami
- Department of Materials Science, University of Washington, Seattle, Washington 98195, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Mosayebi J, Kiyasatfar M, Laurent S. Synthesis, Functionalization, and Design of Magnetic Nanoparticles for Theranostic Applications. Adv Healthc Mater 2017; 6. [PMID: 28990364 DOI: 10.1002/adhm.201700306] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/14/2017] [Indexed: 12/13/2022]
Abstract
In order to translate nanotechnology into medical practice, magnetic nanoparticles (MNPs) have been presented as a class of non-invasive nanomaterials for numerous biomedical applications. In particular, MNPs have opened a door for simultaneous diagnosis and brisk treatment of diseases in the form of theranostic agents. This review highlights the recent advances in preparation and utilization of MNPs from the synthesis and functionalization steps to the final design consideration in evading the body immune system for therapeutic and diagnostic applications with addressing the most recent examples of the literature in each section. This study provides a conceptual framework of a wide range of synthetic routes classified mainly as wet chemistry, state-of-the-art microfluidic reactors, and biogenic routes, along with the most popular coating materials to stabilize resultant MNPs. Additionally, key aspects of prolonging the half-life of MNPs via overcoming the sequential biological barriers are covered through unraveling the biophysical interactions at the bio-nano interface and giving a set of criteria to efficiently modulate MNPs' physicochemical properties. Furthermore, concepts of passive and active targeting for successful cell internalization, by respectively exploiting the unique properties of cancers and novel targeting ligands are described in detail. Finally, this study extensively covers the recent developments in magnetic drug targeting and hyperthermia as therapeutic applications of MNPs. In addition, multi-modal imaging via fusion of magnetic resonance imaging, and also innovative magnetic particle imaging with other imaging techniques for early diagnosis of diseases are extensively provided.
Collapse
Affiliation(s)
- Jalal Mosayebi
- Department of Mechanical Engineering; Urmia University; Urmia 5756151818 Iran
| | - Mehdi Kiyasatfar
- Department of Mechanical Engineering; Urmia University; Urmia 5756151818 Iran
| | - Sophie Laurent
- Laboratory of NMR and Molecular Imaging; University of Mons; Mons Belgium
| |
Collapse
|
12
|
Magnetically Recoverable Pd/Fe
3
O
4
Core–Shell Nanowire Clusters with Increased Hydrogenation Activity. Chempluschem 2017; 82:347-351. [DOI: 10.1002/cplu.201700009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Indexed: 11/07/2022]
|
13
|
Arami H, Khandhar A, Liggitt D, Krishnan KM. In vivo delivery, pharmacokinetics, biodistribution and toxicity of iron oxide nanoparticles. Chem Soc Rev 2015; 44:8576-607. [PMID: 26390044 PMCID: PMC4648695 DOI: 10.1039/c5cs00541h] [Citation(s) in RCA: 492] [Impact Index Per Article: 54.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Iron oxide nanoparticles (IONPs) have been extensively used during the last two decades, either as effective bio-imaging contrast agents or as carriers of biomolecules such as drugs, nucleic acids and peptides for controlled delivery to specific organs and tissues. Most of these novel applications require elaborate tuning of the physiochemical and surface properties of the IONPs. As new IONPs designs are envisioned, synergistic consideration of the body's innate biological barriers against the administered nanoparticles and the short and long-term side effects of the IONPs become even more essential. There are several important criteria (e.g. size and size-distribution, charge, coating molecules, and plasma protein adsorption) that can be effectively tuned to control the in vivo pharmacokinetics and biodistribution of the IONPs. This paper reviews these crucial parameters, in light of biological barriers in the body, and the latest IONPs design strategies used to overcome them. A careful review of the long-term biodistribution and side effects of the IONPs in relation to nanoparticle design is also given. While the discussions presented in this review are specific to IONPs, some of the information can be readily applied to other nanoparticle systems, such as gold, silver, silica, calcium phosphates and various polymers.
Collapse
Affiliation(s)
- Hamed Arami
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington, 98195
| | - Amit Khandhar
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington, 98195
| | - Denny Liggitt
- Department of Comparative Medicine, University of Washington School of Medicine, Seattle, Washington, 98195
| | - Kannan M. Krishnan
- Department of Materials Science and Engineering, University of Washington, Seattle, Washington, 98195
| |
Collapse
|
14
|
Hufschmid R, Arami H, Ferguson RM, Gonzales M, Teeman E, Brush LN, Browning ND, Krishnan KM. Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition. NANOSCALE 2015; 7:11142-54. [PMID: 26059262 PMCID: PMC5198837 DOI: 10.1039/c5nr01651g] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2-30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application.
Collapse
Affiliation(s)
- Ryan Hufschmid
- Department of Materials Science & Engineering, University of Washington, Box 352120, Seattle, Washington 98195-2120, USA.
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Panagiotopoulos N, Duschka RL, Ahlborg M, Bringout G, Debbeler C, Graeser M, Kaethner C, Lüdtke-Buzug K, Medimagh H, Stelzner J, Buzug TM, Barkhausen J, Vogt FM, Haegele J. Magnetic particle imaging: current developments and future directions. Int J Nanomedicine 2015; 10:3097-114. [PMID: 25960650 PMCID: PMC4411024 DOI: 10.2147/ijn.s70488] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Magnetic particle imaging (MPI) is a novel imaging method that was first proposed by Gleich and Weizenecker in 2005. Applying static and dynamic magnetic fields, MPI exploits the unique characteristics of superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs’ response allows a three-dimensional visualization of their distribution in space with a superb contrast, a very high temporal and good spatial resolution. Essentially, it is the SPIONs’ superparamagnetic characteristics, the fact that they are magnetically saturable, and the harmonic composition of the SPIONs’ response that make MPI possible at all. As SPIONs are the essential element of MPI, the development of customized nanoparticles is pursued with the greatest effort by many groups. Their objective is the creation of a SPION or a conglomerate of particles that will feature a much higher MPI performance than nanoparticles currently available commercially. A particle’s MPI performance and suitability is characterized by parameters such as the strength of its MPI signal, its biocompatibility, or its pharmacokinetics. Some of the most important adjuster bolts to tune them are the particles’ iron core and hydrodynamic diameter, their anisotropy, the composition of the particles’ suspension, and their coating. As a three-dimensional, real-time imaging modality that is free of ionizing radiation, MPI appears ideally suited for applications such as vascular imaging and interventions as well as cellular and targeted imaging. A number of different theories and technical approaches on the way to the actual implementation of the basic concept of MPI have been seen in the last few years. Research groups around the world are working on different scanner geometries, from closed bore systems to single-sided scanners, and use reconstruction methods that are either based on actual calibration measurements or on theoretical models. This review aims at giving an overview of current developments and future directions in MPI about a decade after its first appearance.
Collapse
Affiliation(s)
- Nikolaos Panagiotopoulos
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Campus Lübeck, Germany
| | - Robert L Duschka
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Campus Lübeck, Germany
| | - Mandy Ahlborg
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | - Gael Bringout
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | | | - Matthias Graeser
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | | | | | - Hanne Medimagh
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | - Jan Stelzner
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | - Thorsten M Buzug
- Institute of Medical Engineering, University of Lübeck, Lübeck, Germany
| | - Jörg Barkhausen
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Campus Lübeck, Germany
| | - Florian M Vogt
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Campus Lübeck, Germany
| | - Julian Haegele
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig Holstein, Campus Lübeck, Germany
| |
Collapse
|
16
|
Arami H, Khandhar AP, Tomitaka A, Yu E, Goodwill PW, Conolly SM, Krishnan KM. In vivo multimodal magnetic particle imaging (MPI) with tailored magneto/optical contrast agents. Biomaterials 2015; 52:251-61. [PMID: 25818431 DOI: 10.1016/j.biomaterials.2015.02.040] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 01/30/2015] [Accepted: 02/06/2015] [Indexed: 12/31/2022]
Abstract
Magnetic Particle Imaging (MPI) is a novel non-invasive biomedical imaging modality that uses safe magnetite nanoparticles as tracers. Controlled synthesis of iron oxide nanoparticles (NPs) with tuned size-dependent magnetic relaxation properties is critical for the development of MPI. Additional functionalization of these NPs for other imaging modalities (e.g. MRI and fluorescent imaging) would accelerate screening of the MPI tracers based on their in vitro and in vivo performance in pre-clinical trials. Here, we conjugated two different types of poly-ethylene-glycols (NH2-PEG-NH2 and NH2-PEG-FMOC) to monodisperse carboxylated 19.7 nm NPs by amide bonding. Further, we labeled these NPs with Cy5.5 near infra-red fluorescent (NIRF) molecules. Bi-functional PEG (NH2-PEG-NH2) resulted in larger hydrodynamic size (∼98 nm vs. ∼43 nm) of the tracers, due to inter-particle crosslinking. Formation of such clusters impacted the multimodal imaging performance and pharmacokinetics of these tracers. We found that MPI signal intensity of the tracers in blood depends on their plasmatic clearance pharmacokinetics. Whole body mice MPI/MRI/NIRF, used to study the biodistribution of the injected NPs, showed primary distribution in liver and spleen. Biodistribution of tracers and their clearance pathway was further confirmed by MPI and NIRF signals from the excised organs where the Cy5.5 labeling enabled detailed anatomical mapping of the tracers.in tissue sections. These multimodal MPI tracers, combining the strengths of each imaging modality (e.g. resolution, tracer sensitivity and clinical use feasibility) pave the way for various in vitro and in vivo MPI applications.
Collapse
Affiliation(s)
- Hamed Arami
- Department of Materials Science, University of Washington, Seattle, WA, 98195, USA
| | | | - Asahi Tomitaka
- Department of Materials Science, University of Washington, Seattle, WA, 98195, USA
| | - Elaine Yu
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
| | - Patrick W Goodwill
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
| | - Steven M Conolly
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
| | - Kannan M Krishnan
- Department of Materials Science, University of Washington, Seattle, WA, 98195, USA.
| |
Collapse
|
17
|
Razali WAW, Sreenivasan VKA, Goldys EM, Zvyagin AV. Large-scale production and characterization of biocompatible colloidal nanoalumina. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:15091-15101. [PMID: 25434921 DOI: 10.1021/la5042629] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The rapid uptake of nanomaterials in life sciences calls for the development of universal, high-yield techniques for their production and interfacing with biomolecules. Top-down methods take advantage of the existing variety of bulk and thin-film solid-state materials for improved prediction and control of the resultant nanomaterial properties. We demonstrate the power of this approach using high-energy ball milling (HEBM) of alumina (Al2O3). Nanoalumina particles with a mean size of 25 nm in their most stable α-crystallographic phase were produced in gram quantities, suitable for biological and biomedical applications. Nanomaterial contamination from zirconia balls used in HEBM was reduced from 19 to 2% using a selective acid etching procedure. The biocompatibility of the milled nanomaterial was demonstrated by forming stable colloids in water and physiological buffers, corroborated by zeta potentials of +40 mV and -40 mV and characterized by in vitro cytotoxicity assays. Finally, the feasibility of a milled nanoalumina surface in anchoring a host of functional groups and biomolecules was demonstrated by the functionalization of their surface using facile silane chemistry, resulting in the decoration of the nanoparticle surface with amino groups suitable for further conjugation of biomolecules.
Collapse
Affiliation(s)
- W A W Razali
- MQ Biofocus Research Centre, Faculty of Science, Macquarie University , Sydney, NSW 2109, Australia
| | | | | | | |
Collapse
|
18
|
Ferguson RM, Khandhar AP, Arami H, Hua L, Hovorka O, Krishnan KM. Tailoring the magnetic and pharmacokinetic properties of iron oxide magnetic particle imaging tracers. ACTA ACUST UNITED AC 2014; 58:493-507. [PMID: 23787461 DOI: 10.1515/bmt-2012-0058] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 05/13/2013] [Indexed: 01/04/2023]
Abstract
Magnetic particle imaging (MPI) is an attractive new modality for imaging distributions of iron oxide nanoparticle tracers in vivo. With exceptional contrast, high sensitivity, and good spatial resolution, MPI shows promise for clinical imaging in angiography and oncology. Critically, MPI requires high-quality iron oxide nanoparticle tracers with tailored magnetic and surface properties to achieve its full potential. In this review, we discuss optimizing iron oxide nanoparticles' physical, magnetic, and pharmacokinetic properties for MPI, highlighting results from our recent work in which we demonstrated tailored, biocompatible iron oxide nanoparticle tracers that provided two times better linear spatial resolution and five times better signal-to-noise ratio than Resovist.
Collapse
|
19
|
Arami H, Krishnan KM. Intracellular performance of tailored nanoparticle tracers in magnetic particle imaging. JOURNAL OF APPLIED PHYSICS 2014; 115:17B306. [PMID: 24753632 PMCID: PMC3977802 DOI: 10.1063/1.4867756] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 12/05/2013] [Indexed: 05/17/2023]
Abstract
Magnetic Particle Imaging (MPI) is a quantitative mass-sensitive, tracer-based imaging technique, with potential applications in various cellular imaging applications. The spatial resolution of MPI, in the first approximation, improves by decreasing the full width at half maximum (FWHM) of the field-derivative of the magnetization, dm/dH of the nanoparticle (NP) tracers. The FWHM of dm/dH depends critically on NPs' size, size distribution, and their environment. However, there is limited information on the MPI performance of the NPs after their internalization into cells. In this work, 30 to 150 μg of the iron oxide NPs were incubated in a lysosome-like acidic buffer (0.2 ml, 20 mM citric acid, pH 4.7) and investigated by vibrating sample magnetometry, magnetic particle spectroscopy, transmission electron microscopy, and dynamic light scattering (DLS). The FWHM of the dm/dH curves of the NPs increased with incubation time and buffer to NPs ratio, consistent with a decrease in the median core size of the NPs from ∼20.1 ± 0.98 to ∼18.5 ± 3.15 nm. Further, these smaller degraded NPs formed aggregates that responded to the applied field by hysteretic reversal at higher field values and increased the FWHM. The rate of core size decrease and aggregation were inversely proportional to the concentration of the incubated NPs, due to their slower biodegradation kinetics. The results of this model experiment show that the MPI performance of the NPs in the acidic environments of the intracellular organelles (i.e., lysosomes and endosomes) can be highly dependent on their rate of internalization, residence time, and degradation.
Collapse
|
20
|
Arami H, Ferguson RM, Khandhar AP, Krishnan KM. Size-dependent ferrohydrodynamic relaxometry of magnetic particle imaging tracers in different environments. Med Phys 2014; 40:071904. [PMID: 23822441 DOI: 10.1118/1.4810962] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PURPOSE Magnetic particle imaging (MPI) is a recently developed imaging technique that seeks to provide ultrahigh resolution and tracer sensitivity with positive contrast directly originated from superparamagnetic iron oxide nanoparticles (NPs). MPI signals can be generated from a combination of Néel relaxation, Brownian rotational diffusion, and hysteretic reversal mechanisms of NPs in response to applied magnetic fields. When specific targeting of organs, such as carcinoma and endothelial cardiovascular cells, is needed, different behavior may be expected in immobilized NPs, due to complete or partial elimination of the Brownian motion. Here, the authors present an experimental investigation of the MPI spatial resolution and signal intensities as a function of a wide range of median core sizes of NPs under four representative conditions, including after immobilization in a tissue equivalent medium. METHODS Monodisperse hydrophobic NPs with median core diameters (d0) ranging from 7 to 22 nm were synthesized in organic media and subsequently dispersed in aqueous solution after a facile surface modification. Morphology, median size, size distribution, and magnetic properties of the NPs were investigated. Hydrophobic and hydrophilic NPs with various core sizes were immobilized in trioctyl phosphine oxide and agarose gel, respectively. Their size-dependent performance as MPI tracers for system matrix and x-space image reconstruction was evaluated using magnetic particle spectrometry (MPS) and compared with the free rotating counterparts. RESULTS Immobilized NPs with core diameters smaller than ≈ 20 nm have similar spatial resolution, but lower signal intensities when compared with their free rotating counterparts. Compared to their performance in solution, spatial resolution was improved, but signal intensity was lower, when larger NPs with core size of 22 nm were immobilized in agarose. Same trends were observed in signal intensities, when considering either system matrix or x-space approaches. The harmonic and dm/dH signal intensities changed linearly and the spatial resolution did not change with decreasing NP concentration up to 15 μg/ml. CONCLUSIONS The results show that the MPI signal is very sensitive to both NP size and environment. The authors' calculations show that Brownian rotational diffusion is slower than the field switching cycle and, therefore, it has minimal influence on MPS signals. dm/dH analyses show that Néel relaxation is the dominant mechanism determining MPI response in smaller NPs (d0 < ≈ 20 nm). Larger NPs show hysteretic reversal when the applied field amplitude is large enough to overcome the coercivity. Linear variation of the MPS signal intensity with iron concentration but with uniform spatial resolution enables quantitative imaging for a range of applications, from high-concentration bolus chase imaging to low-concentration molecular imaging (while the authors' instrument is noise-limited to ≈ millimolar iron concentrations, nanomolar sensitivity is expected for MPI, theoretically). These results pave the way for future application of the authors' synthesized tracers for immobilized or in vivo targeted MPI of tissues.
Collapse
Affiliation(s)
- Hamed Arami
- Department of Materials Science and Engineering, University of Washington, P.O. Box 352120, Seattle, Washington 98195-2120, USA
| | | | | | | |
Collapse
|