Rainer Tietze

Mitochondria are attractive anticancer targets, but selective targeting remains challenging. We report a Cu²⁺-mediated strategy for mitochondria-directed activity based on intracellular metal coordination. Aminoferrocene drugs were functionalized with Cu²⁺-binding ligands to exploit elevated copper levels in cancer cells. Among these, the bipyridine conjugate AFb-L4 displays pronounced Cu²⁺-dependent cytotoxicity, with an IC₅₀ of 29 nM in ovarian carcinoma cells (∼500-fold enhancement upon Cu²⁺ addition). Spectroscopic, magnetic, and mass spectrometric analyses confirm formation of a 1:1 AFb-L4-Cu²⁺ complex without electronic coupling between the Cu²⁺ and ferrocene centers. Intracellular Cu²⁺ coordination converts AFb-L4 into a cationic species that accumulates in mitochondria, inducing loss of membrane potential, mitochondrial remodeling, and mitochondrial ROS generation. Structure-activity relationships show that stabilization of Cu²⁺ is critical, as a sterically hindered isomer with reduced Cu²⁺ binding is largely inactive. These results establish intracellular Cu²⁺ coordination as a trigger for mitochondrial targeting.

Foodborne illnesses still remain a major health issue, as the WHO reported 600 million diseases and 420,000 deaths worldwide in 2010. Most of them were caused by pathogens like Campylobacter spp., Salmonella enterica , Escherichia coli , and Listeria monocytogenes . Due to the short shelf life of fresh meat and dairy products, a rapid detection of pathogens in contaminated food products is essential. Since reference methods for microbial food analysis require time-consuming nonselective and selective culturing procedures, the need for more efficient approaches is given. In this study, we employ superparamagnetic iron oxide nanoparticles (SPIONs) functionalized with the peptide KRQGRVEVLYRASWGTV derived from the salivary protein GP-340, to successfully remove different species of food-related microorganisms ( Pseudomonas paracarnis , Campylobacter jejuni , Escherichia coli , Enterococcus faecalis , Salmonella enterica , and Listeria monocytogenes ) from pure media and homogenates derived from retail meat products. We discovered differences in extraction efficiencies from pure culture ranging from 18% ( C. jejuni ) to complete extraction ( E. faecalis , L. monocytogenes and P. paracarnis ) depending on the organism. It was also shown that L. monocytogenes could successfully be removed from co-culture with a high surplus of non-pathogenic P. paracarnis , and also from food matrices. Key points: • SPION ^Cit can be functionalized with a GP-340 derived peptide (SPION ^Pep ) • SPION ^Pep  can immobilize and remove L. monocytogenes from pure and co-culture with high surplus of non-pathogenic P. paracarnis • Removal of L. monocytogenes is also possible in complex food matrices

Magnetic nanodiscs (MNDs) represent a transformative class of anisotropic magnetic nanoparticles with intrinsic vortex magnetization, enabling multifunctional applications in biomedical imaging and therapy.

Magnetic nanodiscs (MNDs) represent a transformative class of anisotropic magnetic nanoparticles with intrinsic vortex magnetization, enabling multifunctional applications in biomedical imaging and therapy. Here, we demonstrate their potential as dual-mode magnetic resonance (MR) contrast agents, a unique feature that is enabled by the high longitudinal relaxivity (r₁ ≈ 40 mM⁻¹s⁻¹) at ultralow magnetic fields ( 150 mM⁻¹s⁻¹) at ultrahigh fields (>7 T). This field-dependent relaxivity profile uniquely positions MNDs as versatile T₁/T₂ agents compatible with emerging low-field MRI platforms and high-resolution clinical systems. Ex vivo and in vivo assessments confirmed clear anatomical localization and preferential hepatic accumulation, suggesting prolonged circulation times due to surface-mediated immune evasion. These properties highlight MNDs as promising candidates for next-generation theranostics, with tunable magnetic responses, high contrast efficiency, and the ability to synergize imaging and neurostimulation.

This study explores the correlation between the iron mass on cell surfaces and the resultant magnetic field. Human colorectal cancer cells (HT29 line) were labeled with varying concentrations of superparamagnetic iron oxide nanoparticles (SPIONs) and imaged via an NV center widefield magnetic microscope. To assess the labeling efficacy, a convolutional neural network trained on simulated magnetic dipole data was utilized to reconstruct key labeling parameters on a cell-by-cell basis, including cell diameter, sensor proximity, and the iron mass associated with surface-bound SPIONs. Our analysis provided quantitative metrics for these parameters across a range of labeling concentrations. The findings indicated that increasing the SPION concentration enhances both the cell-surface iron mass and magnetic field strength, demonstrating a saturation effect. This methodology offers a coherent framework for the quantitative, high-throughput characterization of magnetically labeled cells, presenting significant implications for the fields of cell biology and magnetic sensing applications.

This research investigates the impact of various coatings on superparamagnetic iron oxide nanoparticles. The coatings stabilize the nanoparticles, influencing their magnetic behaviour, agglomeration, and oxidation stability.

We introduced a concept of prodrugs activated by H₂O₂ and mitochondrial OH⁻, which is applicable to camptothecin and its derivatives.