Magnetite (Fe₃O₄) nanoparticles with uniform sizes of 10, 20, and 31 nm were prepared by thermal decomposition of Fe(III) oleate or mandelate in a high-boiling point solvent (>320 °C). To render the particles with hydrophilic and antifouling properties, their surface was coated with a PEG-containing bisphosphonate anchoring group. The PEGylated particles were characterized by a range of physicochemical methods, including dynamic light scattering, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and magnetization measurements. As the particle size increased from 10 to 31 nm, the amount of PEG coating decreased from 28.5 to 9 wt.%. The PEG formed a dense brush-like shell on the particle surface, which prevented particles from aggregating in water and PBS (pH 7.4) and maximized the circulation time in vivo. Magnetic resonance relaxometry confirmed that the PEG-modified Fe₃O₄ nanoparticles had high relaxivity, which increased with increasing particle size. In the in vivo experiments in a mouse model, the particles provided visible contrast enhancement in the magnetic resonance images. Almost 70% of administrated 20-nm magnetic nanoparticles still circulated in the blood stream after four hours; however, their retention in the tumor was rather low, which was likely due to the antifouling properties of PEG.

Photoacoustic imaging, an emerging modality, provides supplemental information to ultrasound imaging. We investigated the properties of polypyrrole nanoparticles, which considerably enhance contrast in photoacoustic images, in relation to the synthesis procedure and to their size. We prepared polypyrrole nanoparticles by water-based redox precipitation polymerization in the presence of ammonium persulphate (ratio nPy:nOxi 1:0.5, 1:1, 1:2, 1:3, 1:5) or iron(III) chloride (nPy:nOxi 1:2.3) acting as an oxidant. To stabilize growing nanoparticles, non-ionic polyvinylpyrrolidone was used. The nanoparticles were characterized and tested as a photoacoustic contrast agent in vitro on an imaging platform combining ultrasound and photoacoustic imaging. High photoacoustic signals were obtained with lower ratios of the oxidant (nPy:nAPS ≥ 1:2), which corresponded to higher number of conjugated bonds in the polymer. The increasing portion of oxidized structures probably shifted the absorption spectra towards shorter wavelengths. A strong photoacoustic signal dependence on the nanoparticle size was revealed; the signal linearly increased with particle surface. Coated nanoparticles were also tested in vivo on a mouse model. To conclude, polypyrrole nanoparticles represent a promising contrast agent for photoacoustic imaging. Variations in the preparation result in varying photoacoustic properties related to their structure and allow to optimize the nanoparticles for in vivo imaging.

Hypoxia represents one of the key factors that stimulate the growth of leukemic cells in their niche. Leukemic cells in hypoxia are forced to reprogram their original transcriptome, miRNome, and metabolome. How the coupling of miRNAs/mRNAs helps to maintain or progress the leukemic status is still not fully described. MicroRNAs (miRNAs) regulate practically all biological processes within cells and play a crucial role in leukemia development/progression. Here we worked with the human cell line MEC-1 (human chronic lymphocytic leukemia (CLL)) where we deleted mature miR-155 by CRISPR/Cas9. MEC-1 cells in hypoxia showed a higher proliferation rate with a relatively low level of apoptosis. Interestingly, miR-155 deficiency decreased the proliferation rate in both, normoxia and hypoxia. Besides common hypoxia-related genes (HIF1α, EGLN1, VHL, HK1, and HK2), we also measured, genes for glucose transporters SLC2A1 (GLUT1) and SLC2A3 (GLUT3). Surprisingly, only SLC2A3 (GLUT3) showed significant overexpression in hypoxia conditions in miR-155 deficient MEC-1cells which points to the possible novel target of miR-155 in CLL. Increased glucose uptake and decreased lactate support our hypothesis that miR-155 deficiency and hypoxia transform cell metabolism. To conclude, miR-155 deficiency and hypoxia-impaired glucose metabolism stimulate GLUT3 in CLL cells.