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Item type:Publication, Access status: with files , Genetically engineered bacterial magnetosomes as optimized tracers for magnetic particle imaging(Elsevier, 2026-05-29); ; ; ; Medical imaging relies on tracer materials to enable accurate visualization and diagnosis of diseases. Magnetic Particle Imaging (MPI) is an innovative tomographic modality that offers exceptional sensitivity and temporal resolution. These characteristics make MPI particularly promising for clinical applications such as real-time vascular and perfusion imaging, tumor detection, and intraoperative guidance. However, MPI performance has so far been limited by the quality of available tracers, as conventional chemical synthesis provides only restricted control over the size, shape, and magnetic properties of iron oxide nanoparticles. Biogenic magnetic nanoparticles, so-called magnetosomes, produced by magnetotactic bacteria, represent a compelling alternative. Magnetosome biosynthesis is fully genetically encoded, enabling the natural formation of magnetite nanoparticles with uniform size and morphology, which is difficult to achieve through chemical synthesis. Moreover, genetic engineering of the bacterial production host allows precise tuning of particle characteristics, including size, shape, and magnetic behavior, to meet specific application requirements. In this study, magnetosomes isolated from different Magnetospirillum gryphiswaldense mutant strains, each biomineralizing particles with distinct core diameters, were systematically evaluated as potential MPI tracers. Magnetic particle spectroscopy (MPS) was used to identify the most promising candidates based on their signal properties. These tracers were subsequently subjected to detailed signal analyses and phantom experiments to directly compare their imaging performance. Our findings demonstrate that genetically tailored magnetosomes can substantially improve MPI signal quality, underscoring their potential as next-generation tracers. This work provides a foundation for the rational design of optimized biogenic nanoparticles to advance preclinical and future clinical MPI applications. Statement of significance Magnetic Particle Imaging (MPI) is a novel imaging technology with high sensitivity and real-time capabilities, making it highly promising for clinical applications such as blood flow monitoring and tumor detection. The performance of MPI strongly depends on the properties of the tracer materials used. However, producing high-quality tracers through conventional chemical synthesis remains challenging. In this study, we introduce an innovative biological approach by using genetically engineered magnetotactic bacteria to produce uniform magnetic nanoparticles, so-called magnetosomes. This strategy allows precise control of particle size, shape, and magnetic properties, resulting in tracers with superior performance. Our findings pave the way for the development of next-generation MPI tracers, advancing both fundamental research and potential clinical translation.Publicationtype: Journal Article12 8 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Magnetic particle imaging for real-time perfusion imaging in acute stroke(Jenny Stanford Publishing, 2026-01-01); ; ; ; The fast and accurate assessment of cerebral perfusion is fundamental for the diagnosis and successful treatment of stroke patients. Magnetic particle imaging (MPI) is a new radiation-free tomographic imaging method with a superior temporal resolution, compared to other conventional imaging methods. In addition, MPI scanners can be built as prehospital mobile devices, which require less complex infrastructure than computed tomography (CT) and magnetic resonance imaging (MRI). With these advantages, MPI could accelerate the stroke diagnosis and treatment, thereby improving outcomes. Our objective was to investigate the capabilities of MPI to detect perfusion deficits in a murine model of ischemic stroke. Cerebral ischemia was induced by inserting of a microfilament in the internal carotid artery in C57BL/6 mice, thereby blocking the blood flow into the medial cerebral artery. After the injection of a contrast agent (superparamagnetic iron oxide nanoparticles) specifically tailored for MPI, cerebral perfusion and vascular anatomy were assessed by the MPI scanner within seconds. To validate and compare our MPI data, we performed perfusion imaging with a small animal MRI scanner. MPI detected the perfusion deficits in the ischemic brain, which were comparable to those with MRI but in real-time. For the first time, we showed that MPI could be used as a diagnostic tool for relevant diseases in vivo, such as an ischemic stroke. Due to its shorter image acquisition times and increased temporal resolution compared to that of MRI or CT, we expect that MPI offers the potential to improve stroke imaging and treatment.Publicationtype: Book Part6 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Development of optimized magnetic particle imaging tracers utilizing genetically engineered magnetosomes(Infinite Science Publishing, 2023-03-19); ; ; ; The imaging quality of Magnetic Particle Imaging (MPI) is not just limited by the MPI system but also by the quality of available tracers. The tracer quality can be improved by optimizing the shape, core size and shell of the nanoparticles. However, such a defined synthesis is quite challenging. Biogenic magnetic nanoparticles, so-called magnetosomes, synthesized by magnetotoactic bacteria, might provide a promising alternative. In this study, magnetosomes isolated from different Magnetospirillum gryphiswaldense mutant strains biomineralizing particles with varying core diameters were investigated with regard to their usability as tracers for MPI.Publicationtype: Journal ArticleScopus© Citations 1 79 238 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Magnetic particle imaging for assessment of cerebral perfusion and ischemia(Wiley-Blackwell, 2022-01); ; ; ; Stroke is one of the leading worldwide causes of death and sustained disability. Rapid and accurate assessment of cerebral perfusion is essential to diagnose and successfully treat stroke patients. Magnetic particle imaging (MPI) is a new technology with the potential to overcome some limitations of established imaging modalities. It is an innovative and radiation-free imaging technique with high sensitivity, specificity, and superior temporal resolution. MPI enables imaging and diagnosis of stroke and other neurological pathologies such as hemorrhage, tumors, and inflammatory processes. MPI scanners also offer the potential for targeted therapies of these diseases. Due to lower field requirements, MPI scanners can be designed as resistive magnets and employed as mobile devices for bedside imaging. With these advantages, MPI could accelerate and improve the diagnosis and treatment of neurological disorders. This review provides a basic introduction to MPI, discusses its current use for stroke imaging, and addresses future applications, including the potential for clinical implementation. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.Publicationtype: Review ArticleScopus© Citations 15 231 798 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Design of a head coil for high resolution mouse brain perfusion imaging using magnetic particle imaging(2020-11-25); ; ; ; Magnetic particle imaging (MPI) is a novel and versatile imaging modality developing toward human application. When up-scaling to human size, the sensitivity of the systems naturally drops as the coil sensitivity depends on the bore diameter. Thus, new methods to push the sensitivity limit further have to be investigated to cope for this loss. In this paper a dedicated surface coil for mice is developed, improving the sensitivity in cerebral imaging applications. Similar to magnetic resonance imaging the developed surface coil improves the sensitivity due to the closer vicinity to the region of interest. With the developed surface coil presented in this work, it is possible to image tracer samples containing only 896 pgfe and detect even small vessels and anatomical structures within a wild type mouse model. As current sensitivity measures require a tracer system a new method for determining a sensitivity measure without this requirement is presented and verified to enable comparison between MPI receiver systems.Publicationtype: Journal Article81 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Monitoring Intracranial Cerebral Hemorrhage Using Multicontrast Real-Time Magnetic Particle Imaging(2020-10-27); ; ; ; Magnetic particle imaging (MPI) is an innovative radiation-free tomographic imaging method providing excellent temporal resolution, contrast, sensitivity, and safety. Mobile human MPI prototypes suitable for continuous bedside monitoring of whole-brain perfusion have been developed. However, for the clinical translation of MPI, a crucial gap in knowledge still remains: while MPI can visualize the reduction in blood flow and tissue perfusion in cerebral ischemia, it is unclear whether MPI works in intracranial hemorrhage. Our objective was to investigate the capability of MPI to detect intracranial hemorrhage in a murine model. Intracranial hemorrhage was induced through the injection of collagenase into the striatum of C57BL/6 mice. After the intravenous infusion of a long-circulating MPI-tailored tracer consisting of superparamagnetic iron oxides, we detected the intracranial hemorrhage in less than 3 min and could monitor hematoma expansion in real time. Multicontrast MPI can distinguish tracers based on their physical characteristics, core size, temperature, and viscosity. By employing in vivo multicontrast MPI, we were able to differentiate areas of liquid and coagulated blood within the hematoma, which could provide valuable information in surgical decision making. Multicontrast MPI also enabled simultaneous imaging of hemorrhage and cerebral perfusion, which is essential in the care of critically ill patients with increased intracranial pressure. We conclude that MPI can be used for real-time diagnosis of intracranial hemorrhage. This work is an essential step toward achieving the clinical translation of MPI for point-of-care monitoring of different stroke subtypes.Publicationtype: Journal Article171 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Receive path calibration to exchange system matrix data of different receivers(Infinite Science Publishing, 2020-09-02); ; ; ; In Magnetic Particle Imaging the determination of the system matrix is a time-consuming process. As the transfer function differs depending on the electronics of the receive chain, a system matrix recorded with one chain cannot be used for reconstruction of measurement data using a different receive chain. This leads to huge amounts of data as system matrices have to be recorded for every set of drive field strength, particle system and receiver chain setting. In this paper the complexity of this is reduced by the factor of the receiver electronics. For each receive path of our MPI system the transfer function is recorded and stored on the measurement device. When loading the data, the transfer-function is corrected which allows the exchange of the system matrices data between receiver chains. To demonstrate this system matrix data is compared and a successful reconstruction of an in vivo dataset is shown.Publicationtype: Journal ArticleScopus© Citations 1 63 46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Quasi-simultaneous magnetic particle imaging and navigation of nanomag/synomag-D particles in bifurcation flow experiments(Infinite Science Publishing, 2020-09-02); ; ; ; Magnetic Particle Imaging (MPI) is used to visualize the distribution of superparamagnetic nanoparticles within 3D volumes with high sensitivity in real time. Recently, MPI is utilized to navigate micron-sized particles and micron-sized swimmers, since the magnetic field topology of the MPI scanner is well suited to apply magnetic forces. In this work, we analyze the magnetic mobility and imaging performance of nanomag/synomag-D for Magnetic Particle Imaging/Navigation (MPIN). With MPIN the focus fields are constantly switching between imaging and magnetic force mode, thus enabling quasi-simultaneous navigation and imaging of particles. In flow bifurcation experiment with a 100 % stenosis on one branch, we determine the limiting flow velocity of 1.36 mL/s, which allows all particles to flow only through one branch towards the stenosis. During this experiment, we image the accumulation of the particles within the stenosis. In combination with therapeutic substances, this approach has high potential for targeted drug delivery.Publicationtype: Journal ArticleScopus© Citations 4 109 84 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Organ specific mouse head coil for improved image quality in magnetic particle imaging(Infinite Science Publishing, 2020-09-02); ; ; ; Magnetic particle imaging is a very useful tool in the detection of stroke. To study the ability of stroke in a mouse model the data acquisition is challenging as a mouse brain contains only a very small ratio of blood compared to large animals or humans. The effective concentration within the whole organ is therefore very small, especially compared to the heart or the liver. Typical MPI receiver coils however cover a sensitive region of around 30 mm to 50 mm and have a bore size of above 40 mm. This leads on the one hand to non-optimal signal coupling due to the distance to the particles and on the other hand strong signals from the heart can cause artifacts in the low signal regions. In this work we present a coil optimized for mouse brain imaging, which due to its small size, also dampens signal from regions outside of the coil.Publicationtype: Journal ArticleScopus© Citations 1 118 48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Development of long circulating magnetic particle imaging tracers: use of novel magnetic nanoparticles and entrapment into human erythrocytesAim: Magnetic particle imaging (MPI) is highly promising for biomedical applications, but optimal tracers for MPI, namely superparamagnetic iron oxide-based contrast agents, are still lacking. Materials & methods: The encapsulation of commercially available nanoparticles, specifically synomag®-D and perimag®, into human red blood cells (RBCs) was performed by a hypotonic dialysis and isotonic resealing procedure. The amounts of superparamagnetic iron oxide incorporated into RBCs were determined by Fe quantification using nuclear magnetic resonance and magnetic particle spectroscopy. Results: Perimag-COOH nanoparticles were identified as the best nanomaterial for encapsulation in RBCs. Perimag-COOH-loaded RBCs proved to be viable cells showing a good magnetic particle spectroscopy performance, while the magnetic signal of synomag-D-COOH-loaded RBCs dropped sharply. Conclusion: Perimag-COOH-loaded RBCs could be a potential tool for MPI diagnostic applications.Publicationtype: Journal Article179