Preclinical PET and MR Evaluation of 89Zr- and 68Ga-Labeled Nanodiamonds in Mice over Different Time Scales

At a Glance

Metadata	Details
Publication Date	2022-12-16
Journal	Nanomaterials
Authors	Gordon Winter, Nina Eberhardt, Jessica Löffler, Marco Raabe, Md Noor A Alam
Institutions	Universität Ulm, Medical University of Vienna
Citations	13
Analysis	Full AI Review Included

Technical Documentation & Analysis: Preclinical PET/MR Evaluation of Radiolabeled Nanodiamonds

This document analyzes the research paper “Preclinical PET and MR Evaluation of ⁸⁹Zr- and ⁶⁸Ga-Labeled Nanodiamonds in Mice over Different Time Scales” to provide technical specifications and highlight how 6CCVD’s advanced MPCVD diamond materials and customization services can support and extend this critical research in nanomedicine and quantum sensing.

Executive Summary

This study successfully established a robust preclinical platform for evaluating the pharmacokinetics of nanodiamonds (NDs) using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). The core findings and value proposition are summarized below:

Platform Validation: A preclinical PET/MR imaging platform was successfully created and validated for monitoring ND biodistribution over short (⁶⁸Ga) and long (⁸⁹Zr) time scales (up to 7 days).
Material Foundation: The study utilized Carbon-13 enriched NDs, irradiated with 10 MeV electrons, confirming the material’s suitability for creating Nitrogen Vacancy (NV) centers essential for future hyperpolarized MRI contrast agents.
High Stability Achieved: Radiolabeling with the long-lived radionuclide ⁸⁹Zr using a DFO chelator achieved a high binding yield (97% ± 3%) and demonstrated excellent stability in human serum, saline, and cell culture media for the entire 138-hour measurement period.
Biodistribution Profile: NDs coated with HSA-PEG-DFO showed rapid and stable accumulation predominantly in the Reticuloendothelial System (RES) organs (Liver and Spleen), consistent with non-functionalized nanoparticle behavior.
Tumor Uptake: Low, but detectable, accumulation was observed in tumor xenografts (LNCaP C4-2 and PC-3), with tumor-to-blood ratios exceeding 1, confirming the potential for passive targeting via the Enhanced Permeability and Retention (EPR) effect.
Future Research Roadmap: The results provide a critical reference for future studies focusing on optimizing ND surface functionalization for specific tumor targeting or enhancing uptake kinetics necessary for hyperpolarized NV-diamond MRI.

Technical Specifications

Parameter	Value	Unit	Context
Nanodiamond Type	MD100, C-13 Enriched	N/A	Irradiated for NV center creation
Primary ND Diameter (TEM)	~100	nm	Starting material size
Coated ND Diameter (DLS)	170.1 ± 0.9	nm	cHSA-DFO coated NDs
⁸⁹Zr Half-Life (t_1/2)	78.4	h	Long-lived radionuclide for 7-day monitoring
⁶⁸Ga Half-Life (t_1/2)	67.7	min	Short-lived radionuclide for early monitoring
⁸⁹Zr Labeling Yield	97 ± 3	%	Achieved after 120 min incubation
⁶⁸Ga Labeling Yield	70 ± 16	%	Achieved after 30 min incubation
⁸⁹Zr Stability Duration	138	h	Stable in serum, saline, and cell media
Max Liver Accumulation (⁸⁹Zr, SCID)	67.1 ± 7.7	%IA/g	Measured at 24 h post injection
Max Spleen Accumulation (⁸⁹Zr, SCID)	180.4 ± 148.0	%IA/g	Measured at 168 h post injection
Max Tumor-to-Blood Ratio (LNCaP C4-2)	12.5	Ratio	Median value for ⁸⁹Zr-labeled NDs
MRI Field Strength	11.7	T	Used for anatomical reference (BioSpec 117/16)

Key Methodologies

The experiment relied on precise material synthesis and rigorous in vivo imaging protocols to ensure quantitative and stable radiolabeling of the nanodiamonds.

Diamond Precursor Treatment: Carbon-13 enriched NDs (~100 nm) were irradiated with 10 MeV electrons to induce defects, serving as precursors for Nitrogen Vacancy (NV) centers, critical for hyperpolarization studies.
Protein Functionalization: Human Serum Albumin (HSA) was chemically modified (cationized and PEGylated) to create cHSA-PEG, increasing its molecular weight from 66 kDa (native) to 72 kDa (cHSA) and then further.
Chelator Attachment: The chelating agent deferoxamine (DFO) was coupled to the cHSA-PEG via isothiocyanate reaction, resulting in cHSA-DFO with approximately 15 DFO units per molecule.
ND Coating: NDs were coated with cHSA-DFO (4:1 mass ratio) in boric acid buffer (pH 8.4) and purified via high-speed centrifugation (18,000× g). Successful coating was confirmed by Dynamic Light Scattering (DLS), showing an increase in diameter from 130.8 nm to 170.1 nm.
Radiolabeling Protocol: ⁸⁹ZrCl₄ was adjusted to pH 5-6 using 1 M Na₂CO₃ and incubated with the DFO-NDs for 60-120 min. ⁶⁸Ga was incubated for 30-60 min. Radiolabeling efficiency was monitored using thin layer chromatography (TLC).
In Vivo Imaging: Radiolabeled NDs were injected intravenously (i.v.) into immunodeficient (SCID) and wildtype (C57BL/6) mice. Biodistribution was monitored using dynamic PET scans (350-650 keV energy window) at multiple time points (up to 7 days for ⁸⁹Zr).
Data Validation: PET data were spatially co-registered with high-resolution 11.7T MRI anatomical images. Results were validated ex vivo by sacrificing animals and quantifying organ accumulation (% Injected Activity per gram tissue, %IA/g) using a gamma counter.

6CCVD Solutions & Capabilities

The research highlights the critical role of high-quality diamond materials and precise surface engineering in developing next-generation nanomedicine and quantum imaging agents. 6CCVD is uniquely positioned to supply the foundational MPCVD diamond materials and customization services required to replicate and advance this work.

Applicable Materials & Requirements from Research	6CCVD Solution & Capability	Engineering Advantage
High-Coherence NV Centers (Requires C-13 enriched, low-strain diamond precursors)	Optical Grade Single Crystal Diamond (SCD): We supply high-purity, low-birefringence SCD substrates (up to 500 µm thick, up to 10mm substrates) ideal for creating stable, high-coherence NV centers via controlled irradiation and annealing.	Provides the highest quality diamond foundation necessary to maximize NV center spin coherence time for hyperpolarized MRI applications.
Custom Device Integration (Future work requires integrating NDs into microfluidic or sensing platforms)	Custom Dimensions & Polycrystalline Diamond (PCD): We offer PCD plates/wafers up to 125mm in diameter, with thickness control from 0.1 µm to 500 µm. Custom laser cutting and shaping services are available.	Enables seamless transition from preclinical material testing to large-scale, integrated quantum sensing devices and detectors.
Complex Surface Functionalization (Requires consistent, ultra-smooth surface for HSA-PEG-DFO coating)	Precision Polishing Services: SCD surfaces polished to Ra < 1 nm; inch-size PCD polished to Ra < 5 nm.	Ensures reproducible surface chemistry and minimizes non-specific binding, crucial for maintaining the stability and targeting efficacy of complex coatings like HSA-PEG-DFO.
Integrated Imaging Components (Need for metal contacts or thin films for device operation)	In-House Metalization: We offer custom deposition of thin films including Au, Pt, Pd, Ti, W, and Cu directly onto diamond substrates.	Supports the development of hybrid PET/MR/Quantum sensing devices by providing integrated electrical contacts or protective layers.
Optimizing Uptake Kinetics (Future need for targeted delivery or faster uptake)	Boron-Doped Diamond (BDD): We supply BDD films for electrochemical sensing applications, offering an alternative platform for in vivo monitoring and drug release studies.	Provides versatile diamond materials for exploring alternative nanomedicine delivery and sensing mechanisms beyond NV centers.

Engineering Support

The paper concludes that further functionalization is needed to improve tumor targeting and optimize NDs for hyperpolarized MR imaging. 6CCVD’s in-house PhD team specializes in CVD diamond material science, defect engineering, and surface preparation. We can assist researchers in selecting the optimal diamond material (SCD vs. PCD), controlling doping levels, and achieving the precise surface termination required for advanced Nanomedicine and Quantum Sensing projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) to ensure your research materials arrive efficiently, wherever you are.

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.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano12244471

References

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