Search

Flavin mononucleotide (FMN) is a riboflavin derivative that can be exploited to target the riboflavin transporters (RFTs) and the riboflavin carrier protein (RCP) in cells with high metabolic activity. In this study we present the synthesis of different FMN-coated ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) and their efficiency as targeting contrast agents. Since FMN alone cannot stabilize the nanoparticles, we used adenosine phosphates--AMP, ADP and ATP--as spacers to obtain colloidally stable nanoparticles. Nucleotides with di- and triphosphate groups were intended to increase the USPIO charge and thus improve zeta potential and stability. However, all nanoparticles formed negatively charged clusters with similar properties in terms of zeta potential (-28 ± 2 mV), relaxivity (228-259 mM(-1) s(-1) at 3 T) and hydrodynamic radius (53-85 nm). Molecules with a higher number of phosphate groups, such as ADP and ATP, have a higher adsorption affinity towards iron oxide, which, instead of providing more charge, led to partial desorption and replacement of FMN. Hence, we obtained USPIOs carrying different amounts of targeting agent, which significantly influenced the nanoparticles' uptake. The nanoparticles' uptake by different cancer cells and HUVECs was evaluated photometrically and with MR relaxometry, showing that the cellular uptake of the USPIOs increases with the FMN amount on their surface. Thus, for USPIOs targeted with riboflavin derivatives the use of spacers with increasing numbers of phosphate groups does not improve either zeta potential or the particles' stability, but rather detaches the targeting moieties from their surface, leading to lower cellular uptake.

Here, we present a detailed characterisation of rhodamine B-containing magnetoliposomes (FLU-ML), emphasising the dependence of their fluorescence properties on the presence of iron oxide cores, and the molar fraction of the fluorophore. The magnetoliposome types used exist as colloidally stable, negatively charged clusters with an average hydrodynamic diameter of 95 nm. The molar rhodamine B fractions were 0.67 % and 1.97 %. Rhodamine B normalised fluorescence, quantum yields and fluorescence lifetimes were substantially reduced by inner filter effects as the magnetoliposome concentration is increased, by increasing molar rhodamine B fraction, and by quenching originating from the iron oxide cores. MR relaxometry at 3 T revealed extremely high r2 relaxivities (440 to 554 s-1mM-1) and moderately high r1 values (2.06 to 3.59 s-1mM-1). Upon incubating human prostate carcinoma (PC-3) cells with FLU-ML, a dose-dependent particle internalisation was found by MR relaxometry. In addition, the internalised FLU-ML were clearly visible by fluorescence microscopy. At the FLU-ML concentrations used (up to 3 × 103 M Fe) cell viability was not substantially impaired. These results provide valuable insights on the fluorescence properties of bimodal magnetoliposomes and open promising perspectives for the use of these materials as a platform technology for advanced functional and molecular MR and optical imaging applications. Copyright © 2012 John Wiley & Sons, Ltd.

Riboflavin is an essential vitamin for cellular metabolism and is highly upregulated in metabolically active cells. Consequently, targeting the riboflavin carrier protein (RCP) may be a promising strategy for labeling cancer and activated endothelial cells. Therefore, Ultrasmall SuperParamagnetic Iron Oxide nanoparticles (USPIO) were adsorptively coated with the endogenous RCP ligand flavin mononucleotide (FMN), which renders them target-specific and fluorescent. The core diameter, surface morphology and surface coverage of the resulting FMN-coated USPIO (FLUSPIO) were evaluated using a variety of physico-chemical characterization techniques (TEM, DLS, MRI and fluorescence spectroscopy). The biocompatibility of FLUSPIO was confirmed using three different cell viability assays (Trypan blue staining, 7-AAD staining and TUNEL). In vitro evaluation of FLUSPIO using MRI and fluorescence microscopy demonstrated high labeling efficiency of cancer cells (PC-3, DU-145, LnCap) and activated endothelial cells (HUVEC). Competition experiments (using MRI and ICP-MS) with a 10- and 100-fold excess of free FMN confirmed RCP-specific uptake of the FLUSPIO by PC-3 cells and HUVEC. Hence, RCP-targeting via FMN may be an elegant way to render nanoparticles fluorescent and to increase the labeling efficacy of cancer and activated endothelial cells. This was shown for FLUSPIO, which due to their high T2-relaxivity, are favorably suited for MR cell tracking experiments and cancer detection in vivo.

Flavin mononucleotide (FMN) is a riboflavin derivative that can be exploited to target the riboflavin transporters (RFTs) and the riboflavin carrier protein (RCP) in cells with high metabolic activity. In this study we present the synthesis of different FMN-coated ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) and their efficiency as targeting contrast agents. Since FMN alone cannot stabilize the nanoparticles, we used adenosine phosphates--AMP, ADP and ATP--as spacers to obtain colloidally stable nanoparticles. Nucleotides with di- and triphosphate groups were intended to increase the USPIO charge and thus improve zeta potential and stability. However, all nanoparticles formed negatively charged clusters with similar properties in terms of zeta potential (-28 ± 2 mV), relaxivity (228-259 mM(-1) s(-1) at 3 T) and hydrodynamic radius (53-85 nm). Molecules with a higher number of phosphate groups, such as ADP and ATP, have a higher adsorption affinity towards iron oxide, which, instead of providing more charge, led to partial desorption and replacement of FMN. Hence, we obtained USPIOs carrying different amounts of targeting agent, which significantly influenced the nanoparticles' uptake. The nanoparticles' uptake by different cancer cells and HUVECs was evaluated photometrically and with MR relaxometry, showing that the cellular uptake of the USPIOs increases with the FMN amount on their surface. Thus, for USPIOs targeted with riboflavin derivatives the use of spacers with increasing numbers of phosphate groups does not improve either zeta potential or the particles' stability, but rather detaches the targeting moieties from their surface, leading to lower cellular uptake.

Theranostics 5(8), 905-918 (2015). doi:10.7150/thno.11304, Published by Ivyspring, Wyoming, NSW

The combination of target-specific drugs like bevacizumab with chemotherapeutics has improved treatment efficacy in advanced colorectal cancer (CRC). However, the clinical prognosis of metastatic CRCs is still poor, and novel drugs are currently assessed with respect to their efficacies in patients with CRCs. In a phase III study, the multikinase inhibitor regorafenib (BAY 73-4506) has recently been shown to prolong survival of patients with CRCs after standard therapies failed. In the present study, the activity of regorafenib was investigated in comparison with the angiogenesis inhibitor DC101 in the highly aggressive, murine CT26 metastatic colon cancer model. While a treatment for 10 days with DC101 given at a dose of 34 mg/kg every third day significantly delayed tumor growth compared with vehicle-treated animals, regorafenib completely suppressed tumor growth at a daily oral dose of 30 mg/kg. Regorafenib also induced a stronger reduction in tumor vascularization, as longitudinally assessed in vivo by dynamic contrast-enhanced MRI (DCE-MRI) and confirmed by immunohistochemistry. In addition, regorafenib inhibited the angiogenic activity more strongly and induced a three times higher apoptosis rate than DC101. Even more important, regorafenib completely prevented the formation of liver metastases, whereas in DC101-treated animals, the metastatic rate was only reduced by 33% compared with the vehicle group. In addition, regorafenib significantly reduced the amount of infiltrating macrophages. These data show that the multikinase inhibitor regorafenib exerts strong antiangiogenic, antitumorigenic, and even antimetastatic effects on highly aggressive colon carcinomas indicative for its high potential in the treatment of advanced CRCs. Mol Cancer Ther; 12(7); 1322–31. ©2013 AACR.

Tumour xenografts of well-discernible sizes can be examined well by molecular ultrasound. Here, we investigated whether very early breast carcinomas express sufficient levels of VEGFR2 for reliable molecular ultrasound imaging with targeted microbubbles.MCF-7 breast cancer xenografts were orthotopically implanted in nude mice (n = 26). Tumours measuring from 4 mm(3) (2 mm diameter) up to 65 mm(3) (5 mm diameter) were examined with automated 3D molecular ultrasound using clinically translatable VEGFR2-targeted microbubbles (BR55). Additionally, the relative tumour blood volume was assessed with non-targeted microbubbles (BR38). In vivo ultrasound data were validated by quantitative immunohistochemistry.Very small lesions 2 mm in diameter showed the highest binding of VEGFR2-specific microbubbles. In larger tumours significantly less BR55 accumulated (p = 0.023). Nonetheless, binding of VEGFR2-targeted microbubbles was still high enough for imaging. The relative blood volume was comparable at all tumour sizes. Both findings were confirmed by immunohistochemistry. Additionally, a significantly enhanced number of large and mature vessels were detected with increasing tumour size (p 0.01), explaining the decrease in VEGFR2 expression during tumour growth.3D molecular ultrasound using BR55 is very well suited to depicting the angiogenic activity in very small breast lesions, suggesting its potential for detecting and characterising these lesions.

Here, we present a detailed characterisation of rhodamine B-containing magnetoliposomes (FLU-ML), emphasising the dependence of their fluorescence properties on the presence of iron oxide cores, and the molar fraction of the fluorophore. The magnetoliposome types used exist as colloidally stable, negatively charged clusters with an average hydrodynamic diameter of 95 nm. The molar rhodamine B fractions were 0.67 % and 1.97 %. Rhodamine B normalised fluorescence, quantum yields and fluorescence lifetimes were substantially reduced by inner filter effects as the magnetoliposome concentration is increased, by increasing molar rhodamine B fraction, and by quenching originating from the iron oxide cores. MR relaxometry at 3 T revealed extremely high r2 relaxivities (440 to 554 s-1mM-1) and moderately high r1 values (2.06 to 3.59 s-1mM-1). Upon incubating human prostate carcinoma (PC-3) cells with FLU-ML, a dose-dependent particle internalisation was found by MR relaxometry. In addition, the internalised FLU-ML were clearly visible by fluorescence microscopy. At the FLU-ML concentrations used (up to 3 × 10³ M Fe) cell viability was not substantially impaired. These results provide valuable insights on the fluorescence properties of bimodal magnetoliposomes and open promising perspectives for the use of these materials as a platform technology for advanced functional and molecular MR and optical imaging applications.

EJNMMI Research 1(1), 26 (2011). doi:10.1186/2191-219X-1-26, Published by Springer, Berlin [u.a.]

Lactate- or bicarbonate-buffered solutions in continuous extracorporeal renal replacement therapies. Background Continuous renal replacement therapies (CRRTs) are well accepted for critically ill patients with acute renal failure (ARF). Today, daily fluid exchange in CRRT reaches 30 to 40 liter and more. Therefore, the composition of the substitution/dialysate fluid, often primarily developed either for intermittent treatment or for peritoneal dialysis, becomes more relevant. Lactate (30 to 45 mmol/liter) is frequently used as the buffer because of the high stability of this substance. However, lactate is thought to have negative effects on metabolic and hemodynamic parameters. Methods Published data for different substitution fluids are presented with respect to acidosis and lactate concentration, uremia, and hemodynamic and metabolic alterations. Results Only a few studies compare substitution fluids with different buffers. Uremia and acidosis (pH, base excess) were sufficiently controlled during CRRT with an exchange volume of in average 30 liters using either buffer. If patients with severe liver failure and lactic acidosis were excluded, no difference in hemodynamic and metabolic parameters between the solutions occurred. The plasma lactate concentration was elevated during lactate use in some cases, but lactate levels remained within normal limits in patients without liver impairment. The bicarbonate concentration in the solutions should exceed 35 to 40 mmol/liter, as in some cases the buffer capacity of the solutions was inadequate. In patients with severe liver failure or lactic acidosis, solutions with lactate buffer were shown not to be indicated. Conclusion In patients with reduced lactate metabolism, for example, concomitant severe liver failure, after liver transplantation or in lactic acidosis, bicarbonate-buffered solutions should be used. In nearly all other cases of critically ill patients with ARF, lactate-buffered solutions may be used as well as bicarbonate solutions.

Nano research 9(5), 1319-1333 (2016). doi:10.1007/s12274-016-1028-7, Published by Tsinghua Press, [S.l.]