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Islam MA, Syed IM, Mamun MA, Hoque SM. Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid. Front Chem 2024; 12:1347423. [PMID: 38524916 PMCID: PMC10958782 DOI: 10.3389/fchem.2024.1347423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 02/07/2024] [Indexed: 03/26/2024] Open
Abstract
In this study, Mg1-xCoxFe2O4 (0≤x ≤ 1 with ∆x = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (Tmax) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co2+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co2+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (Mr/Ms), and anisotropy constant (K1) of the Mg1-xCoxFe2O4 nanoparticles increase with Co2+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and Tmax (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co2+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co2+ content decreases, but it decreases as the Co2+ content increases, a consequence of higher anisotropy with the increase in Co2+. Additionally, it is noteworthy that the maximum temperature (Tmax) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power.
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Affiliation(s)
- M. Aminul Islam
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh
- Department of Physics, University of Dhaka, Dhaka, Bangladesh
- Department of Physics, Magura Govt. Mahila College, Magura, Bangladesh
| | | | - M. Al Mamun
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh
| | - S. Manjura Hoque
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh
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Deb N, Rashid R, Das H, Syed IM, Hoque SM. Enhanced specific loss power of hematite-chitosan nanohybrid synthesized by hydrothermal method. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230384. [PMID: 37830020 PMCID: PMC10565375 DOI: 10.1098/rsos.230384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 09/12/2023] [Indexed: 10/14/2023]
Abstract
We used a hydrothermal technique to develop nano-scale α-Fe2O3 particles and functionalized them with chitosan. An X-ray diffraction study revealed α-Fe2O3 nanoparticles were of single-phase, lattice constants were a = 5.07 Å and c = 13.68 Å, and the grain size was 27 nm. The presence of lattice fringes in the HRTEM image confirmed the crystalline nature of the α-Fe2O3. The Mössbauer spectra reveal a mixed relaxation state, which supports the PPMS studies. Zero-field cooled studies revealed the existence of a Morin transition and blocking temperature. The z-average value of the coated particles by DLS was between 218 and 235 nm, PDI ranged from 0.048 to 0.119, and zeta potential was +46.8 mV. We incubated the Vero and HeLa cell lines for 24 h to study the viability of the nanohybrids at different concentrations. Hyperthermia studies revealed the maximum temperature and specific loss power attained by the hematite-chitosan nanohybrid solution of a concentration between 0.25-4 mg ml-1. The Tmax at the lowest and highest concentrations of 0.25 and 4 mg ml-1 were 42.9 and 48.3°C, while the SLP were 501.6 and 35.5 W g-1, which are remarkably high when the maximum magnetization of α-Fe2O3 nanoparticles was as small as 1.98 emu g-1 at 300 K.
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Affiliation(s)
- Nandita Deb
- Materials Science Division, Atomic Energy Centre Dhaka, Dhaka 1000, Bangladesh
| | - Rimi Rashid
- Materials Science Division, Atomic Energy Centre Dhaka, Dhaka 1000, Bangladesh
| | - H. Das
- Materials Science Division, Atomic Energy Centre Dhaka, Dhaka 1000, Bangladesh
| | | | - S. Manjura Hoque
- Materials Science Division, Atomic Energy Centre Dhaka, Dhaka 1000, Bangladesh
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A review on an effect of dispersant type and medium viscosity on magnetic hyperthermia of nanoparticles. Polym Bull (Berl) 2022. [DOI: 10.1007/s00289-022-04324-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Islam MK, Haque MM, Rashid R, Hasan R, Islam MA, Khan MNI, Hoque SM. Size Effect on MRI/MFH Relaxations by a High Anisotropic CoFe2O4-Chitosan Conjugate and Imaging/Angiography Efficacy. J Inorg Organomet Polym Mater 2022. [DOI: 10.1007/s10904-022-02381-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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AL-Harbi L, Darwish MS. Functionalized iron oxide nanoparticles: Synthesis through ultrasonic-assisted co-precipitation and performance as hyperthermic agents for biomedical applications. Heliyon 2022; 8:e09654. [PMID: 35711994 PMCID: PMC9192808 DOI: 10.1016/j.heliyon.2022.e09654] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 05/01/2022] [Accepted: 05/31/2022] [Indexed: 12/31/2022] Open
Abstract
Dual-functional iron oxide nanoparticles (IONPs), displaying self-heating and antibacterial effects are highly desired for biomedical application. This study involved the synthesis of functionalized IONPs coated with 3-aminopropyltriethoxysilane and polyethylene glycol via ultrasonic-assisted co-precipitation technique. The synthesized IONPs were then characterized by using Fourier-transform infrared spectroscopy, X-ray diffraction, dynamic light scattering, scanning electron microscopy, zeta potential, vibrating sample magnetometer and thermogravimetric analysis techniques. In addition, the effect of the synthesized IONPs on bacterial growth (S. aureus and E. coli) was studied. The influence of magnetic field power, as well as the viscous carriers on the heating efficiency of the synthesized IONPs was investigated. The specific absorption rate values increased as the power increased and decreased with the increase in the carrier viscosity. These characteristics render the synthesized iron oxide nanoparticles synthesized in the present study suitable for biomedical application as hyperthermic agents.
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Affiliation(s)
- L.M. AL-Harbi
- Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, 21589, Saudi Arabia
| | - Mohamed S.A. Darwish
- Egyptian Petroleum Research Institute, 1 Ahmed El-Zomor Street, El Zohour Region, Nasr City, Cairo, 11727, Egypt
- Corresponding author.
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Islam MA, Hasan MR, Haque MM, Rashid R, Syed IM, Hoque SM. Efficacy of surface-functionalized Mg 1−xCo xFe 2O 4 (0 ≤ x ≤ 1; Δ x = 0.1) for hyperthermia and in vivo MR imaging as a contrast agent. RSC Adv 2022; 12:7835-7849. [PMID: 35424744 PMCID: PMC8982169 DOI: 10.1039/d2ra00768a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 02/10/2022] [Indexed: 12/31/2022] Open
Abstract
Surface-functionalized Mg1−xCoxFe2O4 (0 ≤ x ≤ 1; Δx = 0.1) can be an exciting candidate as an MRI contrast agent and for thermotherapeutic applications.
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Affiliation(s)
- M. Aminul Islam
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, 1000, Dhaka, Bangladesh
- Magura Govt. Mahila College, Magura, Bangladesh
- Department of Physics, University of Dhaka, Bangladesh
| | - M. Razibul Hasan
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, 1000, Dhaka, Bangladesh
| | - M. Mahbubabl Haque
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, 1000, Dhaka, Bangladesh
| | - Rimi Rashid
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, 1000, Dhaka, Bangladesh
| | | | - S. Manjura Hoque
- Materials Science Division, Atomic Energy Centre Dhaka, Bangladesh Atomic Energy Commission, 1000, Dhaka, Bangladesh
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Hoque SM, Islam MK, Hoq A, Haque MM, Maritim S, Coman D, Hyder F. Comparative Study of Specific Loss Power and Transverse Relaxivity of Spinel Ferrite Nanoensembles Coated With Chitosan and Polyethylene Glycol. FRONTIERS IN NANOTECHNOLOGY 2021. [DOI: 10.3389/fnano.2021.644080] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We synthesized spinel ferrite nanoensembles (MnFe2O4, CoFe2O4, and Fe3O4) using the chemical co-precipitation method and characterized their physical, chemical, and magnetic properties by X-ray diffraction (XRD), transmission electron microscopy (TEM), physical properties measurement system (PPMS), Mössbauer spectroscopy, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and Raman spectroscopy. Their relaxation properties and potential for hyperthermia therapy were determined using nuclear magnetic resonance (NMR) and cell viability assay, respectively. XRD and TEM data confirmed that the particle core sizes were 6–9 nm before coating while their sizes increased to 10–14 nm and 14–20 nm after coating with chitosan and polyethylene glycol (PEG), respectively. Mössbauer spectroscopy showed superparamagnetic behavior for MnFe2O4 nanoparticles and ferrimagnetic behavior for the CoFe2O4 and Fe3O4 nanoparticles. A detailed studies of MH loops of all three ferrites before and after coating showed surface functionalization by a large reduction of coercivity and anisotropy. The successful coating was further confirmed by the peak shifts in the FTIR spectra of the particles whereas Raman spectra of coated ferrites also displayed the characteristic absorption patterns and suppression of the ferrite peaks suggesting successful coating. The induced heating profile of the nanoparticles in stable suspension was tested with a radio frequency magnetic field of 76 mT and a frequency of 400 kHz. High mortality (>98%) of 9 L gliosarcoma cancer cells by hyperthermia suggested that these nanoparticles could be used for cancer therapy. Transverse relaxivities (r2) determined by NMR for chitosan-coated MnFe2O4, CoFe2O4, and Fe3O4 nanoparticles were 297 (±22), 353 (±26), and 345 (±13), mM−1S−1, while for PEG-coated nanoparticles are 165 (±22), 146 (±14), and 159 (±07) mM−1S−1, respectively. Overall these spinel ferrite nanoensembles show great promise for cancer theranostics research applications.
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Manganese Ferrite Nanoparticles (MnFe 2O 4): Size Dependence for Hyperthermia and Negative/Positive Contrast Enhancement in MRI. NANOMATERIALS 2020; 10:nano10112297. [PMID: 33233590 PMCID: PMC7699708 DOI: 10.3390/nano10112297] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 10/28/2020] [Accepted: 11/06/2020] [Indexed: 12/13/2022]
Abstract
We synthesized manganese ferrite (MnFe2O4) nanoparticles of different sizes by varying pH during chemical co-precipitation procedure and modified their surfaces with polysaccharide chitosan (CS) to investigate characteristics of hyperthermia and magnetic resonance imaging (MRI). Structural features were analyzed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), selected area diffraction (SAED) patterns, and Mössbauer spectroscopy to confirm the formation of superparamagnetic MnFe2O4 nanoparticles with a size range of 5–15 nm for pH of 9–12. The hydrodynamic sizes of nanoparticles were less than 250 nm with a polydispersity index of 0.3, whereas the zeta potentials were higher than 30 mV to ensure electrostatic repulsion for stable colloidal suspension. MRI properties at 7T demonstrated that transverse relaxation (T2) doubled as the size of CS-coated MnFe2O4 nanoparticles tripled in vitro. However, longitudinal relaxation (T1) was strongest for the smallest CS-coated MnFe2O4 nanoparticles, as revealed by in vivo positive contrast MRI angiography. Cytotoxicity assay on HeLa cells showed CS-coated MnFe2O4 nanoparticles is viable regardless of ambient pH, whereas hyperthermia studies revealed that both the maximum temperature and specific loss power obtained by alternating magnetic field exposure depended on nanoparticle size and concentration. Overall, these results reveal the exciting potential of CS-coated MnFe2O4 nanoparticles in MRI and hyperthermia studies for biomedical research.
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Shakil MS, Hasan MA, Uddin MF, Islam A, Nahar A, Das H, Khan MNI, Dey BP, Rokeya B, Hoque SM. In Vivo Toxicity Studies of Chitosan-Coated Cobalt Ferrite Nanocomplex for Its Application as MRI Contrast Dye. ACS APPLIED BIO MATERIALS 2020; 3:7952-7964. [DOI: 10.1021/acsabm.0c01069] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Md. Salman Shakil
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
- Department of Pharmacology & Toxicology, University of Otago, Dunedin 9016, New Zealand
| | - Md. Ashraful Hasan
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
| | - Md. Forhad Uddin
- Department of Biochemistry and Molecular Biology, Jahangirnagar University, Savar Union 1342, Bangladesh
| | - Aminul Islam
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
- Department of Physics, Dhaka University, Dhaka 1000, Bangladesh
| | - Arijun Nahar
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
| | - Harinarayan Das
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
| | | | - Bishnu Pada Dey
- Department of Pathology, Bangabandhu Sheikh Mujib Medical University, Dhaka 1000, Bangladesh
| | - Begum Rokeya
- Department of Pharmacology, Bangladesh Institute of Health Sciences, Dhaka 1216, Bangladesh
| | - S. Manjura Hoque
- Material Science Division, Atomic Energy Centre, Dhaka 1000, Bangladesh
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Zhang Y, Guo S, Zhang P, Zhong J, Liu W. Iron oxide magnetic nanoparticles based low-field MR thermometry. NANOTECHNOLOGY 2020; 31:345101. [PMID: 32408274 DOI: 10.1088/1361-6528/ab932b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This paper reports on a highly accurate approach of magnetic resonance (MR) thermometry using iron oxide magnetic nanoparticles (MNPs) as temperature sensors. An empirical model for the description of the temperature dependent R 2 relaxation rate is proposed by taking into account the temperature sensitivity of the MNP magnetization. The temperature sensitivity of the MNP magnetization (η) and the temperature sensitivity of the R 2 relaxation rate (κ) are simulated with the proposed empirical models to investigate their dependence on the magnetic field and the particle size. Simulation results show the existence of optimal magnetic fields Hoη and Hoκ that maximize the temperature sensitivities η and κ. Furthermore, simulations and experiments demonstrate that the optimal magnetic field Hoη (Hoκ ) decreases with increasing the particle size. Experiments on temperature dependent R 2 relaxation rate are performed at different magnetic fields for MNP samples with different iron concentrations. Experimental results show that the proposed MR thermometry using MNPs as temperature sensors allows a temperature estimation accuracy of about 0.05 °C. We believe that the achieved approach of highly accurate MR thermometry is of great interest and significance to biomedicine and biology.
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Affiliation(s)
- Yapeng Zhang
- School of Artificial Intelligence and Automation, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of China. Key Laboratory of Image Processing and Intelligent Control (Huazhong University of Science and Technology), Ministry of Education, Wuhan 430074, People's Republic of China
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Synthesis of Magnetic Ferrite Nanoparticles with High Hyperthermia Performance via a Controlled Co-Precipitation Method. NANOMATERIALS 2019; 9:nano9081176. [PMID: 31426427 PMCID: PMC6724091 DOI: 10.3390/nano9081176] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 08/10/2019] [Accepted: 08/13/2019] [Indexed: 12/17/2022]
Abstract
Magnetic nanoparticles (MNPs) that exhibit high specific loss power (SLP) at lower metal content are highly desirable for hyperthermia applications. The conventional co-precipitation process has been widely employed for the synthesis of magnetic nanoparticles. However, their hyperthermia performance is often insufficient, which is considered as the main challenge to the development of practicable cancer treatments. In particular, ferrite MNPs have unique properties, such as a strong magnetocrystalline anisotropy, high coercivity, and moderate saturation magnetization, however their hyperthermia performance needs to be further improved. In this study, cobalt ferrite (CoFe2O4) and zinc cobalt ferrite nanoparticles (ZnCoFe2O4) were prepared to achieve high SLP values by modifying the conventional co-precipitation method. Our modified method, which allows for precursor material compositions (molar ratio of Fe+3:Fe+2:Co+2/Zn+2 of 3:2:1), is a simple, environmentally friendly, and low temperature process carried out in air at a maximum temperature of 60 °C, without the need for oxidizing or coating agents. The particles produced were characterized using multiple techniques, such as X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV–Vis spectroscopy), and a vibrating sample magnetometer (VSM). SLP values of the prepared nanoparticles were carefully evaluated as a function of time, magnetic field strength (30, 40, and 50 kA m−1), and the viscosity of the medium (water and glycerol), and compared to commercial magnetic nanoparticle materials under the same conditions. The cytotoxicity of the prepared nanoparticles by in vitro culture with NIH-3T3 fibroblasts exhibited good cytocompatibility up to 0.5 mg/mL. The safety limit of magnetic field parameters for SLP was tested. It did not exceed the 5 × 109 Am−1 s−1 threshold. A saturation temperature of 45 °C could be achieved. These nanoparticles, with minimal metal content, can ideally be used for in vivo hyperthermia applications, such as cancer treatments.
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Brain Tumor Diagnostics and Therapeutics with Superparamagnetic Ferrite Nanoparticles. CONTRAST MEDIA & MOLECULAR IMAGING 2017; 2017:6387217. [PMID: 29375280 PMCID: PMC5742516 DOI: 10.1155/2017/6387217] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 09/24/2017] [Indexed: 11/18/2022]
Abstract
Ferrite nanoparticles (F-NPs) can transform both cancer diagnostics and therapeutics. Superparamagnetic F-NPs exhibit high magnetic moment and susceptibility such that in presence of a static magnetic field transverse relaxation rate of water protons for MRI contrast is augmented to locate F-NPs (i.e., diagnostics) and exposed to an alternating magnetic field local temperature is increased to induce tissue necrosis (i.e., thermotherapy). F-NPs are modified by chemical synthesis of mixed spinel ferrites as well as their size, shape, and coating. Purposely designed drug-containing nanoparticles (D-NPs) can slowly deliver drugs (i.e., chemotherapy). Convection-enhanced delivery (CED) of D-NPs with MRI guidance improves glioblastoma multiforme (GBM) treatment. MRI monitors the location of chemotherapy when D-NPs and F-NPs are coadministered with CED. However superparamagnetic field gradients produced by F-NPs complicate MRI readouts (spatial distortions) and MRS (extensive line broadening). Since extracellular pH (pHe) is a cancer hallmark, pHe imaging is needed to screen cancer treatments. Biosensor imaging of redundant deviation in shifts (BIRDS) extrapolates pHe from paramagnetically shifted signals and the pHe accuracy remains unaffected by F-NPs. Hence effect of both chemotherapy and thermotherapy can be monitored (by BIRDS), whereas location of F-NPs is revealed (by MRI). Smarter tethering of nanoparticles and agents will impact GBM theranostics.
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Mapping Extracellular pH of Gliomas in Presence of Superparamagnetic Nanoparticles: Towards Imaging the Distribution of Drug-Containing Nanoparticles and Their Curative Effect on the Tumor Microenvironment. CONTRAST MEDIA & MOLECULAR IMAGING 2017; 2017:3849373. [PMID: 29362558 PMCID: PMC5736903 DOI: 10.1155/2017/3849373] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 09/25/2017] [Accepted: 10/03/2017] [Indexed: 12/17/2022]
Abstract
Since brain's microvasculature is compromised in gliomas, intravenous injection of tumor-targeting nanoparticles containing drugs (D-NPs) and superparamagnetic iron oxide (SPIO-NPs) can deliver high payloads of drugs while allowing MRI to track drug distribution. However, therapeutic effect of D-NPs remains poorly investigated because superparamagnetic fields generated by SPIO-NPs perturb conventional MRI readouts. Because extracellular pH (pHe) is a tumor hallmark, mapping pHe is critical. Brain pHe is measured by biosensor imaging of redundant deviation in shifts (BIRDS) with lanthanide agents, by detecting paramagnetically shifted resonances of nonexchangeable protons on the agent. To test the hypothesis that BIRDS-based pHe readout remains uncompromised by presence of SPIO-NPs, we mapped pHe in glioma-bearing rats before and after SPIO-NPs infusion. While SPIO-NPs accumulation in the tumor enhanced MRI contrast, the pHe inside and outside the MRI-defined tumor boundary remained unchanged after SPIO-NPs infusion, regardless of the tumor type (9L versus RG2) or agent injection method (renal ligation versus coinfusion with probenecid). These results demonstrate that we can simultaneously and noninvasively image the specific location and the healing efficacy of D-NPs, where MRI contrast from SPIO-NPs can track their distribution and BIRDS-based pHe can map their therapeutic impact.
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