| Metadata | Details |
|---|
| Publication Date | 2022-12-16 |
| Journal | Nanomaterials |
| Authors | Gordon Winter, Nina Eberhardt, Jessica Löffler, Marco Raabe, Md Noor A Alam |
| Institutions | Medical University of Vienna, UniversitÀt Ulm |
| Citations | 13 |
| Analysis | Full AI Review Included |
This research establishes a robust preclinical platform combining Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) for the quantitative, non-invasive evaluation of Nanodiamond (ND) pharmacokinetics.
- Core Material: Carbon-13 enriched NDs (~100 nm diameter) were functionalized with a biocompatible Human Serum Albumin (HSA)-PEG coating and the chelator Deferoxamine (DFO).
- Radiolabeling Success: High radiochemical yields were achieved for both long-lived Zirconium-89 (89Zr, t1/2 = 78.4 h, 97 ± 3% bound) and short-lived Gallium-68 (68Ga, t1/2 = 67.7 min, 70 ± 16% bound). 89Zr stability was confirmed up to 138 h.
- Biodistribution Profile: Following intravenous injection, NDs exhibited rapid uptake and stable, long-term accumulation primarily in the organs of the Reticuloendothelial System (RES): the liver (up to 67.1 %IA/g) and spleen (up to 180.4 %IA/g).
- Model Validation: The platform was successfully tested in both immunocompetent (C57BL/6) and immunodeficient (SCID) mouse strains, showing similar biodistribution profiles.
- Quantitative Accuracy: Excellent correlation (R2 close to 1) was found between PET imaging data and ex vivo gamma counter quantification for 89Zr-NDs, validating the platform for absolute quantification of ND concentration.
- Tumor Targeting: Low but detectable accumulation was observed in prostate cancer xenografts (LNCaP C4-2 and PC-3), confirming uptake via the Enhanced Permeability and Retention (EPR) effect, with maximum tumor-to-blood ratios up to 12.5.
| Parameter | Value | Unit | Context |
|---|
| ND Core Material | Carbon-13 enriched | N/A | Used for NV center creation (MRI potential) |
| ND Diameter (MD100) | ~100 | nm | Based on Transmission Electron Microscopy (TEM) |
| Coated ND Diameter (DLS) | 170.1 ± 0.9 | nm | Post cHSA-DFO coating (PDI: 0.133) |
| Electron Irradiation Energy | 10 | MeV | Used for NV center creation |
| Zirconium-89 (89Zr) Half-life (t1/2) | 78.4 | h | Long-lived PET radionuclide |
| Gallium-68 (68Ga) Half-life (t1/2) | 67.7 | min | Short-lived PET radionuclide |
| 89Zr Labeling Efficiency | 97 ± 3 | % | Bound activity after 120 min incubation |
| 68Ga Labeling Efficiency | 70 ± 16 | % | Bound activity after 30 min incubation |
| DFO Units per cHSA-PEG | ~15 | units | Average coupling efficiency |
| Liver Accumulation (Max, 89Zr) | 67.1 ± 7.7 | %IA/g | SCID mice, 24 h post injection (p.i.) |
| Spleen Accumulation (Max, 89Zr) | 180.4 ± 148.0 | %IA/g | SCID mice, 168 h p.i. |
| Maximum Tumor-to-Blood Ratio | 12.5 | Ratio | LNCaP C4-2 xenograft (72 h p.i.) |
| MRI Field Strength | 11.7 | T | Anatomical reference imaging |
| 68Ga Positron Range (PR) | 0.337 | cm | Contributes to Partial Volume Effect (PVE) in PET |
| 89Zr Positron Range (PR) | 0.123 | cm | Lower PR, better spatial resolution than 68Ga |
- ND Core Preparation: Carbon-13 enriched NDs were irradiated with 10 MeV electrons to induce Nitrogen Vacancy (NV) centers, intended for future hyperpolarized MRI studies.
- Chelator Functionalization: Human Serum Albumin (HSA) was cationized (cHSA) and PEGylated (cHSA-PEG, 2000 g/mol PEG chains). The chelator Deferoxamine (DFO) was subsequently coupled to the cHSA-PEG via isothiocyanate reaction, yielding cHSA-DFO (approximately 15 DFO units per protein).
- ND Coating: NDs (0.1 mg/mL) were coated with cHSA-DFO (mass ratio 4:1 cHSA-DFO:NDs) overnight. Free proteins were removed by centrifugation (18,000Ă g).
- Radiolabeling:
- 89ZrCl4 was pH adjusted (5-6) and incubated with DFO-NDs for 60-120 min (1500-fold DFO excess relative to 89Zr).
- 68Ga (eluted from a generator) was incubated with DFO-NDs for 30-60 min (up to 92,000-fold DFO excess relative to 68Ga).
- Stability Testing: 89Zr-ND stability was assessed in human serum, 0.9% NaCl, and cell culture media via thin layer chromatography (TLC) over 138 h.
- In Vivo Administration: Radiolabeled NDs were injected intravenously (i.v.) into male SCID (tumor xenograft model) and C57BL/6 (wildtype) mice.
- Multimodal Imaging:
- PET scans (Focus120) were performed dynamically (1 h p.i.) and statically (up to 7 days p.i. for 89Zr).
- Anatomical correlation was provided by high-resolution MRI (11.7T BioSpec) using a fast multi-slice gradient echo sequence (TE/TR = 1.5 ms/150 ms).
- Ex Vivo Validation: Animals were sacrificed at various time points, and organs were excised, weighed, and quantified using a gamma counter (%IA/g) to validate PET results.
| Industry/Application | Relevance to ND Technology |
|---|
| Nanomedicine & Drug Delivery | NDs coated with HSA/PEG offer a highly inert, biocompatible platform for carrying therapeutic agents (e.g., doxorubicin). The study confirms the long circulation time and RES accumulation profile critical for passive targeting (EPR effect). |
| Longitudinal Imaging Diagnostics | The use of 89Zr enables non-invasive, quantitative monitoring of nanoparticle fate over multiple days, essential for optimizing dosing and scheduling in preclinical trials. |
| Hyperpolarized Quantum Sensing | The 13C-enriched NDs containing NV centers are foundational materials for developing next-generation hyperpolarized MRI contrast agents, offering significantly enhanced sensitivity for molecular imaging. |
| Preclinical Screening Platforms | The established PET/MR imaging and validation methodology provides a standardized, quantitative tool for rapidly assessing the pharmacokinetics and biodistribution of new ND surface chemistries or targeting ligands. |
| Immunology Research | The comparison between immunodeficient (SCID) and immunocompetent (C57BL/6) models provides insight into how the RES (liver, spleen) handles nanoparticles, informing the design of immune-modulating nanocarriers. |
View Original Abstract
Nanodiamonds (NDs) have high potential as a drug carrier and in combination with nitrogen vacancies (NV centers) for highly sensitive MR-imaging after hyperpolarization. However, little remains known about their physiological properties in vivo. PET imaging allows further evaluation due to its quantitative properties and high sensitivity. Thus, we aimed to create a preclinical platform for PET and MR evaluation of surface-modified NDs by radiolabeling with both short- and long-lived radiotracers. Serum albumin coated NDs, functionalized with PEG groups and the chelator deferoxamine, were labeled either with zirconium-89 or gallium-68. Their biodistribution was assessed in two different mouse strains. PET scans were performed at various time points up to 7 d after i.v. injection. Anatomical correlation was provided by additional MRI in a subset of animals. PET results were validated by ex vivo quantification of the excised organs using a gamma counter. Radiolabeled NDs accumulated rapidly in the liver and spleen with a slight increase over time, while rapid washout from the blood pool was observed. Significant differences between the investigated radionuclides were only observed for the spleen (1 h). In summary, we successfully created a preclinical PET and MR imaging platform for the evaluation of the biodistribution of NDs over different time scales.
- 2018 - Direct hyperpolarization of micro- and nanodiamonds for bioimaging applicationsâConsiderations on particle size, functionalization and polarization loss [Crossref]
- 2015 - Hyperpolarized nanodiamond with long spin-relaxation times [Crossref]
- 2017 - Hyperpolarized Nanodiamond Surfaces [Crossref]
- 2016 - Diamond Quantum Devices in Biology [Crossref]
- 2018 - Robust optical polarization of nuclear spin baths using Hamiltonian engineering of nitrogen-vacancy center quantum dynamics [Crossref]
- 2014 - Nanodiamond as a New Hyperpolarizing Agent and Its 13C MRS [Crossref]
- 2020 - Synthesis and coherent properties of 13C-enriched sub-micron diamond particles with nitrogen vacancy color centers [Crossref]
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- 2017 - Positron emission tomography and nanotechnology: A dynamic duo for cancer theranostics [Crossref]
- 2017 - Recent development of nanoparticles for molecular imaging [Crossref]