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The search for alternatives to Gd-containing magnetic resonance imaging (MRI) contrast agents addresses the field of Fe(III)-bearing species with the expectation that the use of an essential metal ion may avoid the issues raised by the exogenous Gd. Attention is currently devoted to highly stable Fe(III) complexes with hexacoordinating ligands, although they may lack any coordinated water molecule. We found that the hexacoordinated Fe(III) complex with two units of deferasirox, a largely used iron sequestering agent, owns properties that can make it a viable alternative to Gd-based agents. Fe(deferasirox)2 displays an outstanding thermodynamic stability, a high binding affinity to human serum albumin (three molecules of complex are simultaneously bound to the protein), and a good relaxivity that increases in the range 20-80 MHz. The relaxation enhancement is due to second sphere water molecules likely forming H-bonds with the coordinating phenoxide oxygens. A further enhancement was observed upon the formation of the supramolecular adduct with albumin. The binding sites of Fe(deferasirox)2 on albumin were characterized by relaxometric competitive assays. Preliminary in vivo imaging studies on a tumor-bearing mouse model indicate that, on a 3 T MRI scanner, the contrast ability of Fe(deferasirox)2 is comparable to the one shown by the commercial Gd(DTPA) agent. ICP-MS analyses on blood samples withdrawn from healthy mice administered with a dose of 0.1 mmol/kg of Fe(deferasirox)2 showed that the complex is completely removed in 24 h.

This study is focused on the development of innovative sensors to non-invasively monitor the tissue implant status by Fast-Field-Cycling Magnetic Resonance Imaging (FFC-MRI). These sensors are based on oligo-histidine moieties that are conjugated to PLGA polymers representing the structural matrix for cells hosting scaffolds. The presence of 14N atoms of histidine causes a quadrupolar relaxation enhancement (also called Quadrupolar Peak, QP) at 1.39 MHz. This QP falls at a frequency well distinct from the QPs generated by endogenous semisolid proteins. The relaxation enhancement is pH dependent in the range 6.5–7.5, thus it acts as a reporter of the scaffold integrity as it progressively degrades upon lowering the microenvironmental pH. The ability of this new sensors to generate contrast in an image obtained at 1.39 MHz on a FFC-MRI scanner is assessed. A good biocompatibility of the histidine-containing scaffolds is observed after its surgical implantation in healthy mice. Over time the scaffold is colonized by endogenous fibroblasts and this process is accompanied by a progressive decrease of the intensity of the relaxation peak. In respect to the clinically used contrast agents this material has the advantage of generating contrast without the use of potentially toxic paramagnetic metal ions.

This study reports the development of a completely new class of MRI contrast agents, displaying remarkable relaxation effects in the absence of paramagnetic metal ions. Their detection requires the acquisition of images at variable magnetic field strength as provided by fast field cycling imaging scanners. They contain poly-histidine chains (poly-His), whose imidazole groups generate 14 N-quadrupolar-peaks that cause a relaxation enhancement of water protons at a frequency (1.38±0.3 MHz) that is readily detectable from the frequencies associated with endogenous proteins. The poly-His quadrupolar peaks are detectable only when the polymer is in a solid-like form, that is, at pH>6.6. Above this value, their intensity is pH dependent and can be used to report on the occurring pH changes. On this basis, the poly-His moieties were conjugated to biocompatible polymers, such as polylactic and glycolic acid, in order to form stable nanoparticles able to encapsulate structured water in their core. FFC images were acquired to assess their contrast-generating ability.

International audience; Dysfunctional elastin turnover plays a major role in the progression of atherosclerotic plaques. Failure of tropoelastin cross-linking into mature elastin leads to the accumulation of tropoelastin within the growing plaque, increasing its instability. Here we present Gd4-TESMA, an MRI contrast agent specifically designed for molecular imaging of tropoelastin within plaques. Gd4-TESMA is a tetrameric probe composed of a tropoelastin-binding peptide (the VVGS-peptide) conjugated with four Gd(III)-DOTA-monoamide chelates. It shows a relaxivity per molecule of 34.0 ± 0.8 mM-1 s-1 (20 MHz, 298 K, pH 7.2), a good binding affinity to tropoelastin (KD = 41 ± 12 μM), and a serum half-life longer than 2 h. Gd4-TESMA accumulates specifically in atherosclerotic plaques in the ApoE-/- murine model of plaque progression, with 2 h persistence of contrast enhancement. As compared to the monomeric counterpart (Gd-TESMA), the tetrameric Gd4-TESMA probe shows a clear advantage regarding both sensitivity and imaging time window, allowing for a better characterization of atherosclerotic plaques.

The search for alternatives to Gd-containing magnetic resonance imaging (MRI) contrast agents addresses the field of Fe(III)-bearing species with the expectation that the use of an essential metal ion may avoid the issues raised by the exogenous Gd. Attention is currently devoted to highly stable Fe(III) complexes with hexacoordinating ligands, although they may lack any coordinated water molecule. We found that the hexacoordinated Fe(III) complex with two units of deferasirox, a largely used iron sequestering agent, owns properties that can make it a viable alternative to Gd-based agents. Fe(deferasirox)

Background The combination of imaging and therapeutic agents in the same smart nanoparticle is a promising option to perform a minimally invasive imaging guided therapy. In this study, Low density lipoproteins (LDL), one of the most attractive biodegradable and biocompatible nanoparticles, were used for the simultaneous delivery of Paclitaxel (PTX), a hydrophobic antitumour drug and an amphiphilic contrast agent, Gd-AAZTA-C17, in B16-F10 melanoma cell line. These cells overexpress LDL receptors, as assessed by flow cytometry analysis. Results PTX and Gd-AAZTA-C17 loaded LDLs (LDL-PTX-Gd) have been prepared, characterized and their stability was assessed under 72 h incubation at 37 °C and compared to LDL loaded with Gd-AAZTA-C17 (LDL-Gd) and LDL-PTX. The cytotoxic effect of LDL-PTX-Gd was evaluated by MTT assay. The anti-tumour drug loaded into LDLs showed a significantly higher toxicity on B16-F10 cells with respect to the commercially available formulation Paclitaxel kabi (PTX Kabi) used in clinical applications. Tumour cells uptake was initially assessed by ICP-MS and MRI on B16-F10 cell line. By the analysis of the image signal intensity, it was possible to extrapolate the amount of internalized PTX indirectly by the decrease of relaxation times caused by Gd, proportional to its concentration. Finally, the treatment with PTX loaded LDL on B16-F10 tumour bearing mice resulted in a marked reduction of tumour growth compared to the administration of PTX Kabi alone. Conclusions LDLs are selectively taken-up by tumour cells and can be successfully exploited for the selective delivery of Paclitaxel and imaging agents. For the first time the anon invasive “in vivo” determination of the amount of PTX accumulated in the tumour was possible, thanks to the use of theranostic agents of natural origin. Graphic abstract

This study is focused on the development of innovative sensors to non-invasively monitor the tissue implant status by Fast-Field-Cycling Magnetic Resonance Imaging (FFC-MRI). These sensors are based on oligo-histidine moieties that are conjugated to PLGA polymers representing the structural matrix for cells hosting scaffolds. The presence of 14N atoms of histidine causes a quadrupolar relaxation enhancement (also called Quadrupolar Peak, QP) at 1.39 MHz. This QP falls at a frequency well distinct from the QPs generated by endogenous semisolid proteins. The relaxation enhancement is pH dependent in the range 6.5-7.5, thus it acts as a reporter of the scaffold integrity as it progressively degrades upon lowering the microenvironmental pH. The ability of this new sensors to generate contrast in an image obtained at 1.39 MHz on a FFC-MRI scanner is assessed. A good biocompatibility of the histidine-containing scaffolds is observed after its surgical implantation in healthy mice. Over time the scaffold is colonized by endogenous fibroblasts and this process is accompanied by a progressive decrease of the intensity of the relaxation peak. In respect to the clinically used contrast agents this material has the advantage of generating contrast without the use of potentially toxic paramagnetic metal ions.

HPLW is a Vascular Endothelial Growth Factor (VEGF)-mimicking beta-hairpin peptide endowed of proangiogenic effect and showing valuable biomedical application in the proangiogenic therapy. However, the translational potential of HPLW is limited by its low metabolic stability, which would shorten the in vivo efficacy of the molecule. Here, we developed a peptide analog of HPLW, named HPLW2, that retains the structural and biological properties of the original peptide but features an impressive resistance to degradation by human serum proteases. HPLW2 was obtained by covalently modifying the chemical structure of the peptide with molecular tools known to impart protease resistance. Notably, the peptide was cyclized by installing an interstrand triazole bridge through Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) reaction. HPLW2 appears as a novel and promising drug candidate with potential biomedical application in the proangiogenic therapy as a low molecular weight drug, alternative to the use of VEGF. Our work points out the utility of the interstrand triazole bridge as effective chemical platform for the conformational and metabolic stabilization of beta-hairpin bioactive peptides.

The discovery of isocitrate dehydrogenases (IDHs) mutations in several malignancies has brought to the approval of drugs targeting IDH1/2 mutants in cancers. More recently it has been suggested that the enzymatic inhibition of IDHs may have therapeutic potentials also for wild-type IDH cancers. Specifically, IDH2 inhibition can sensitize multiple myeloma cells to proteasome inhibitors. However, inhibitors directed against native IDHs are not present on the market. Here, we exploited an allosteric inhibitor of mutant IDH2 (AGI-6780), known to also decrease the activity of wild-type IDH2. Since AGI-6780 effectiveness in vivo is limited by its high hydrophobicity and very low bioavailability, the drug was loaded into mesoporous silica nanoparticles (MSNs) with the aim to enhance its efficacy. Furthermore, to enable high drug retention into the silica pores, improve biocompatibility, and reduce the off-target delivery of the drug, a Supported phosphoLipidic Bilayer (SLB) was self-assembled on the outer MSN surface. The silica nanoparticles were thus coated with three different lipid formulations and characterized in terms of structure, size, and morphology. We demonstrated that MSN@SLB nanoparticles have improved colloidal stability and hemocompatibility with respect to pristine MSN. We showed that MSN@SLB formulation displays an excellent loading and retention of the IDH2 inhibitor AGI-6780, with a limited drug leakage depending on the lipid formulation. Finally, we proved that AGI-6780-loaded MSN@SLB nanoparticles efficaciously inhibited the IDH2 enzymatic activity of multiple myeloma cells. Overall, this study provides a proof of concept of drug delivery to multiple myeloma cells by repurposing a neglected/dismissed drug (AGI-6780) with the use of smart nanoparticles and enabling the sensitization of multiple myeloma cells towards other possible treatments.

Simple Summary Chronic myeloid leukemia stem cells (CML LSCs) are a rare and quiescent population that are resistant to tyrosine kinase inhibitors. CML LSCs have many features in common with hematopoietic stem cells (HSCs) and selectively targeting this population and sparing HSCs is of paramount importance. Targeted therapy by liposome via reducing side effects, controlled release, and versatile surface modifications is an effective way for the treatment of different cancers including leukemia. Here for the first time, we designed a liposome conjugated with Begelomab (anti-CD26) loaded with venetoclax to selectively target CD26+ CML LSCs/progenitor cells and to increase treatment outcome in CML patients. We proved that after antigen binding and drug release, the CD26+ LSCs/progenitor cells could be eliminated without any side effect on CD26− cells. Abstract CML is a hematopoietic stem-cell disorder emanating from breakpoint cluster region/Abelson murine leukemia 1 (BCR/ABL) translocation. Introduction of different TKIs revolutionized treatment outcome in CML patients, but CML LSCs seem insensitive to TKIs and are detectable in newly diagnosed and resistant CML patients and in patients who discontinued therapy. It has been reported that CML LSCs aberrantly express some CD markers such as CD26 that can be used for the diagnosis and for targeting. In this study, we confirmed the presence of CD26+ CML LSCs in newly diagnosed and resistant CML patients. To selectively target CML LSCs/progenitor cells that express CD26 and to spare normal HSCs/progenitor cells, we designed a venetoclax-loaded immunoliposome (IL-VX). Our results showed that by using this system we could selectively target CD26+ cells while sparing CD26− cells. The efficiency of venetoclax in targeting CML LSCs has been reported and our system demonstrated a higher potency in cell death induction in comparison to free venetoclax. Meanwhile, treatment of patient samples with IL-VX significantly reduced CD26+ cells in both stem cells and progenitor cells population. In conclusion, this approach showed that selective elimination of CD26+ CML LSCs/progenitor cells can be obtained in vitro, which might allow in vivo reduction of side effects and attainment of treatment-free, long-lasting remission in CML patients.

Herein, the synthesis and an extensive characterization of two novel Gd(AAZTA) (AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetra acetic acid) derivatives functionalized with short (C2 and C4 ) n-alkyl acid functions are reported. The carboxylate functionality is the site for further conjugations for the design of more specific contrast agents (CAs). Interestingly, it has been found that the synthesized complexes display enhanced properties for use as MRI contrast agents on their own. The stability constants determined by using potentiometric titration and UV/Vis spectrophotometry were slightly higher than the one reported for the parent Gd(AAZTA) complex. This observation might be accounted for by the larger sigma-electron donation of the acyl substituents with respect to the one provided by the methyl group in the parent complex. As far as concerns the kinetic stability, transmetallation experiments with endogenous ions (e.g. Cu2+ ) implied that the Gd3+ ions present in these Gd(AAZTA) derivatives show somewhat smaller susceptibility to chemical exchange towards these ions at 25 °C, close to the physiological condition. The 1 H NMR spectra of the complexes with EuIII and YbIII displayed a set of signals consistent with half the number of methylene protons present on each ligand. The number of resonances was invariant over a large range of temperatures, suggesting the occurrence of a fast interconversion between structural isomers. The relaxivity values (298 K, 20 MHz) were consistent with q=2 being equal to 8.8 mm-1 s-1 for the C2 derivative and 9.4 mm-1 s-1 for the C4 one, that is, sensibly larger than the one reported for Gd(AAZTA) (7.1 mm-1 s-1 ). Variable-temperature (VT)-T217 O NMR measurements showed, for both complexes, the presence of two populations of coordinated water molecules, one in fast and one in slow exchange with the bulk water. As the high-resolution 1 H NMR spectra of the analogs with EuIII and YbIII did not show the occurrence of distinct isomers (as frequently observed in other macrocyclic lanthanide(III)-containing complexes), we surmised the presence of two fast-interconverting isomers in solution. The analysis of the 17 O NMR VT-T2 profiles versus temperature allowed their relative molar fraction to be established as 35 % for the isomer with the fast exchanging water and 65 % for the isomer with the water molecules in slower exchange. Finally, 1 H NMRD profiles over an extended range of applied magnetic field strengths have been satisfactory fitted on the basis of the occurrence of the two interconverting species.

A novel, highly biocompatible, well soluble melanin-based probe obtained from the conjugation of melanin macromolecule to bovine serum albumin (BSA) was tested as a contrast agent for photoacoustic tumor imaging. Five soluble conjugates (PheoBSA A-E) were synthesized by oxidation of dopamine (DA) in the presence of variable amounts of BSA. All systems showed the similar size and absorbance spectra, being PheoBSA D (DA:BSA ratio 1:2) the one showing the highest photoacoustic efficiency. This system was then selected for the investigations as it showed a marked enhancement of the photoacoustic (PA) contrast in the tumor region upon iv injection. Biodistribution studies confirmed the accumulation of PheoBSA D within the tumor region and showed fast renal elimination, lack of cell toxicity, and good hemocompatibility. A higher PA contrast enhancement was observed in the case of PC3 prostate tumor xenograft when compared to the TS/A breast one, likely reflecting different vascularization/extravasation properties between the two tumor murine models. The improved PA properties shown by PheoBSA D allowed to set up a 3D dynamic contrast-enhanced (DCE) approach that demonstrated a persistent increase of the PA signal in the tumor region for a long period. Overall, the herein reported results demonstrate that PheoBSA D is a promising blood pool contrast agent for in vivo PA imaging, particularly useful for the set-up of 3D DCE-PA approaches to monitor tumor vascular properties.

Herein, the synthesis and an extensive characterization of two novel Gd(AAZTA) (AAZTA=6-amino-6-methylperhydro-1,4-diazepine tetra acetic acid) derivatives functionalized with short (C

This study reports the development of a completely new class of MRI contrast agents, displaying remarkable relaxation effects in the absence of paramagnetic metal ions. Their detection requires the acquisition of images at variable magnetic field strength as provided by fast field cycling imaging scanners. They contain poly-histidine chains (poly-His), whose imidazole groups generate

Nowadays, magnetic resonance imaging (MRI) is one of the key, noninvasive modalities to detect and stage cancer which benefits from contrast agents (CA) to differentiate healthy from tumor tissue. An innovative class of MRI CAs is represented by Gd-loaded gold nanoparticles. The size, shape and chemical functionalization of Gd-loaded gold nanoparticles appear to affect the observed relaxation enhancement of water protons in their suspensions. The herein reported results shed more light on the determinants of the relaxation enhancement brought by Gd-loaded concave cube gold nanoparticles (CCGNPs). It has been found that, in the case of nanoparticles endowed with concave surfaces, the relaxivity is remarkably higher compared to the corresponding spherical (i.e., convex) gold nanoparticles (SPhGNPs). The main determinant for the observed relaxation enhancement is represented by the occurrence of a large contribution from second sphere water molecules which can be exploited in the design of high-efficiency MRI CA.

Objectives Being administered intravenously, the tissue that gadolinium-based contrast agents (GBCAs) for magnetic resonance imaging mostly encounter is blood. Herein, it has been investigated how much Gd is internalized by cellular blood components upon the in vitro incubation of GBCAs in human blood or upon intravenous administration of GBCAs to healthy mice. We report results that show how the superb sensitivity of inductively coupled plasma-mass spectrometry (ICP-MS) allows the detection of very tiny amounts of GBCAs entering red blood cells (RBCs) and white blood cells (WBCs). This finding may introduce new insights in the complex matter relative to excretion and retention pathway of administered GBCAs. Materials and methods The study was tackled by 2 independent approaches. First, human blood was incubated in vitro with 5 mM of GBCAs (gadoteridol, gadobenate dimeglumine, gadodiamide, and gadopentetate dimeglumine) for variable times (30 minutes, 1 hour, 2 hours, and 3 hours) at 37°C. Then, blood cell components were isolated by using the Ficoll Histopaque method, washed 3 times, mineralized, and analyzed by ICP-MS for total Gd quantification. Furthermore, blood components derived from human blood incubated with gadodiamide or gadoteridol underwent UPLC-MS (ultra performance liquid chromatography-mass spectrometry) analysis for determination of the amount of intact Gd-DTPA-BMA and Gd-HPDO3A. Second, the distribution of Gd in the blood components of healthy CD-1 mice was administered intravenously with a single dose (1.2 mmol/kg) of gadodiamide or gadoteridol. Blood samples were separated and processed at different time points (24 hours, 48 hours, 96 hours, and 10 days after GBCA administration). As for human blood, ICP-MS quantification of total Gd and UPLC-MS determination of the amount of intact GBCAs were carried out. Results The amount of Gd taken up by RBCs and WBCs was well detectable by ICP-MS. The GBCAs seem to be able to cross the membrane by diffusion (RBCs) or, possibly, by macropinocytosis (WBCs). Ex vivo studies allowed it to be established that the structure of the different GBCAs were not relevant to determine the amount of Gd internalized in the cells. Although the amount of Gd steadily decreases over time in gadoteridol-labeled cells, in the case of gadodiamide, the amount of Gd in the cells does not decrease (even 10 days after the administration of the GBCA). Moreover, while gadoteridol maintains its structural integrity upon cellular uptake, in the case of gadodiamide, the amount of intact complex markedly decreases over time. Conclusions The detection of significant amounts of Gd in RBCs and WBCs indicates that GBCAs can cross blood cell membranes. This finding may play a role in our understanding of the processes that are at the basis of Gd retention in the tissues of patients who have received the administration of GBCAs.

Leukemia is a type of hematopoietic stem/progenitor cell malignancy characterized by the accumulation of immature cells in the blood and bone marrow. Treatment strategies mainly rely on the administration of chemotherapeutic agents, which, unfortunately, are known for their high toxicity and side effects. The concept of targeted therapy as magic bullet was introduced by Paul Erlich about 100 years ago, to inspire new therapies able to tackle the disadvantages of chemotherapeutic agents. Currently, nanoparticles are considered viable options in the treatment of different types of cancer, including leukemia. The main advantages associated with the use of these nanocarriers summarized as follows: i) they may be designed to target leukemic cells selectively; ii) they invariably enhance bioavailability and blood circulation half-life; iii) their mode of action is expected to reduce side effects. FDA approval of many nanocarriers for treatment of relapsed or refractory leukemia and the desired results extend their application in clinics. In the present review, different types of nanocarriers, their capability in targeting leukemic cells, and the latest preclinical and clinical data are discussed.

Prostate cancer (PCa), the most widespread male cancer in western countries, is generally eradicated by surgery, especially if localized. However, during surgical procedures, it is not always possible to identify malignant tissues by visual inspection. Among the possible consequences, there is the formation of positive surgical margins, often associated with recurrence. In this work, the gastrin-releasing peptide receptor (GRPR), overexpressed in the prostatic carcinoma and not in healthy tissues or in benign hyperplasia (BPH), is proposed as target molecule to design a novel near-infrared fluorescent (NIRF) probe for image-guided prostatectomy. The NIRF dye Sulfo-Cy5.5 was conjugated to a Bombesin-like peptide (BBN), targeting GRPR. The final product, called BBN-Cy5.5, was characterized and tested in vitro on PC-3, DU145, and LnCAP cell lines, using unconjugated Sulfo-Cy5.5 as control. In vivo biodistribution studies were performed by optical imaging in PC-3 tumor-bearing and healthy mice. Finally, simulation of the surgical protocol was carried out. BBN-Cy5.5 showed high water solubility and a good relative quantum yield. The ability of the probe to recognize the GRPR, highly expressed in PC-3 cells, was tested both in vitro and in vivo, where a significant tumor accumulation was achieved 24 h post-injection. Furthermore, a distinguishable fluorescent signal was visible in mice bearing PCa, when the surgery was simulated. By contrast, low signal was found in healthy or BPH-affected mice. This work proposes a new NIRF probe ideal to target GRPR, biomarker of PCa. The promising data obtained suggest that the dye could allow the real-time intraoperative visualization of prostate cancer.

Objective: The early embryo implantation is characterized by enhanced uterine vascular permeability at the site of blastocyst attachment, followed by extracellular-matrix remodeling and angiogenesis. Two TG (transglutaminase) isoenzymes, TG2 (tissue TG) and FXIII (factor XIII), catalyze covalent cross-linking of the extracellular-matrix. However, their specific role during embryo implantation is not fully understood. Approach and Results: For mapping the distribution as well as the enzymatic activities of TG2 and FXIII towards blood-borne and resident extracellular-matrix substrates, we synthetized selective and specific low molecular weight substrate analogs for each of the isoenzymes. The implantation sites were challenged by genetically modifying the trophoblast cells in the outer layer of blastocysts, to either overexpress or deplete TG2 or FXIII, and the angiogenic response was studied by dynamic contrast–enhanced-magnetic resonance imaging. Dynamic contrast–enhanced-magnetic resonance imaging revealed a decrease in the permeability of decidual vasculature surrounding embryos in which FXIII were overexpressed in trophoblast cell. Reduction in decidual blood volume fraction was demonstrated when either FXIII or TG2 were overexpressed in embryonic trophoblast cell and was elevated when trophoblast cell was depleted of FXIII. These results were corroborated by histological analysis. Conclusions: In this study, we report on the isoenzyme-specific roles of TG2 and FXIII during the early days of mouse pregnancy and further reveal their involvement in decidual angiogenesis. Our results reveal an important magnetic resonance imaging-detectable function of embryo-derived TG2 and FXIII on regulating maternal angiogenesis during embryo implantation in mice.Visual Overview: An online visual overview is available for this article.

A novel fluorescein/Gd-DOTAGA containing nanoprobe for the visualization of tumors by optical and Magnetic Resonance Imaging (MRI) is reported herein. It is based on the functionalization of the surface of small mesoporous silica nanoparticles (MSNs) (∼30 nm) with the arginine-glycine-aspartic (RGD) moieties, which are known to target αvβ3 integrin receptors overexpressed in several tumor cells. The obtained nanoprobe (Gd-MSNs-RGD) displays good stability, tolerability and high relaxivity (37.6 mM(-1) s(-1) at 21.5 MHz). After a preliminary evaluation of their cytotoxicity and targeting capability toward U87MG cells by in vitro fluorescence and MR imaging, the nanoprobes were tested in vivo by T1-weighted MR imaging of xenografted murine tumor models. The obtained results demonstrated that the Gd-MSNs-RGD nanoprobes are good reporters both in vitro and in vivo for the MR-visualization of tumor cells overexpressing αvβ3 integrin receptors.

The introduction of different generations of tyrosine kinase inhibitors (TKIs) significantly improved outcome and survival rate in chronic myeloid leukemia (CML) patients. However, long-term use of TKIs is concomitant with many side effects that affect the quality of life in patients. Approximately half of CML patients achieve deep molecular response (DMR), this makes them suitable candidates to discontinue the TKI therapy in a controlled condition, and about half of them will remain in treatment free remission (TFR) after discontinuation. It has been shown that a small population of leukemia stem cells (LSCs) as the residual disease burden is present at diagnosis, during the treatment, and in patients who are in TFR. While CML LSCs have many features in common with HSCs, they express specific markers such as CD25, CD26, IL1-RAP, etc., which can be used for the diagnosis and targeting. Protection by the bone marrow microenvironment and activity of signaling pathways such as WNT/β catenin, Hedgehog, PI3K, JAK/STAT in CML LSCs in a BCR-ABL dependent and independent manner guarantee their survival and elimination of these cells solely using TKIs seems ineffective. Herein we designed a pegylated liposomal nanocarrier conjugated with a specific antibody against CD26 (Begelomab, ADIENNE, Lugano, Switzerland). Then we loaded this immunoliposome with venetoclax, a BCL2 inhibitor, to eliminate CML LSCs selectively and to spare normal HSCs. First, we measured the expression of CD26 in the bone marrow and peripheral blood samples of newly diagnosed patients. We had a high expression of CD26 in CD34+/CD38- of both PB and BM, and a low expression on CD34+/CD38+ (progenitors) cells. Also, the expression of this marker in resistant patients to TKIs was visible while it was absent in normal stem cells. After the synthesis of the liposome, we conjugated Begelomab to the liposome. Then, we tested the selectivity of the designed system in different positive and negative cells. Our designed immunoliposome showed a strong selectivity toward CD26 positive cells. We also tested the selectivity on CML primary cells; in particular, we sorted newly diagnosed CML samples based on CD34+/CD38-/CD26- for HSCs and CD34+/CD38-/CD26+ for LSCs. Based on the confocal and flow cytometry analysis, our designed immunoliposome selectively targets LSCs and spares HSCs. Then we loaded this immunoliposome with venetoclax, and we treated CD26 positive and negative cells with this system. Based on our preliminary results, this immunoliposome loaded venetoclax specifically induced apoptosis in CD26+ cells, with higher activity compared to free venetoclax at the same dose. However, more analysis will be performed to confirm the selectivity of this system. Based on the obtained results, CD26 in newly diagnosed CML patients is expressed by CML LSCs and is a suitable option for diagnosis and targeting. Our preliminary data strongly suggest that we can selectively target CML LSCs. The main advantage of this system is its precision to hit the target. So we expect that after the drug release, the LSCs will be eliminated without any side effects on normal cells. Liposomes are suitable carriers because of their biocompatibility, self-assembly, large drug payload, and minimal toxicity. This strategy may help us to increase the number of patients attaining and maintaining TFR without relapsing. Disclosures Saglio: Ariad: Research Funding; Pfizer: Research Funding; Incyte: Research Funding; Roche: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Research Funding.

Molecular imaging requires the specific accumulation of contrast agents at the target. To exploit the superb resolution of MRI for applications in molecular imaging, gadolinium chelates, as the MRI contrast agents (CA), have to be conjugated to a specific vector able to recognize the epitope of interest. Several Gd(III)-chelates can be chemically linked to the same binding vector in order to deliver multiple copies of the CA (multimers) in a single targeting event thus increasing the sensitivity of the molecular probe. Herein three novel bifunctional agents, carrying one functional group for the bioconjugation to targeting vectors and four Gd(III)-AAZTA chelate functions for MRI contrast enhancement (AAZTA = 6-amino-6-methylperhydro-1,4-diazepinetetraacetic acid), are reported. The relaxivity in the tetrameric derivatives is 16.4 ± 0.2 mMGd–1 s–1 at 21.5 MHz and 25 °C, being 2.4-fold higher than that of parent, monomeric Gd(III)-AAZTA. These compounds can be used as versatile building blocks to insert pre...

Purpose To evaluate the speciation of gadolinium-containing species after multiple administrations of the gadolinium-based contrast agents (GBCAs) gadodiamide and gadoteridol and to quantify the amount of intact gadolinium complexes and insoluble gadolinium-containing species. Materials and Methods A total dose of 13.2 mmol per kilogram of body weight of each GBCA was administered in healthy Wistar rats over a period of 8 weeks. Three days after the final administration, rats were sacrificed, and the brains were excised and divided into three portions. Each portion of brain homogenate was divided into two parts, one for determination of the total gadolinium concentration with inductively coupled plasma mass spectrometry and one for determination of the amount of intact GBCA and gadolinium-containing insoluble species. Relaxometric measurements of gadodiamide and gadolinium trichloride in the presence of polysialic acid were also performed. Results The mean total gadolinium concentrations for gadodiamide and gadoteridol, respectively, were 0.317 μg/g ± 0.060 (standard deviation) and 0.048 μg/g ± 0.004 in the cortex, 0.418 μg/g ± 0.078 and 0.051 μg/g ± 0.009 in the subcortical brain, and 0.781 μg/g ± 0.079 and 0.061 μg/g ± 0.012 in the cerebellum. Gadoteridol comprised 100% of the gadolinium species found in rats treated with gadoteridol. In rats treated with gadodiamide, the largest part of gadolinium retained in brain tissue was insoluble species. In the cerebellum, the amount of intact gadodiamide accounts for 18.2% ± 10.6 of the total gadolinium found therein. The mass balance found for gadolinium implies the occurrence of other soluble gadolinium-containing species (approximately 30%). The relaxivity of the gadolinium polysialic acid species formed in vitro was 97.8 mM/sec at 1.5 T and 298 K. Conclusion Gadoteridol was far less retained, and the entire detected gadolinium was intact soluble GBCA, while gadodiamide yielded both soluble and insoluble gadolinium-containing species, with insoluble species dominating.

PolyLactic and Glycolic Acid nanoparticles (PLGA-NPs), coated with L-Ferritin,are exploited for the simultaneous delivery of paclitaxel and an amphiphilic Gd based MRI contrast agent into breast cancer cells (MCF7). L-Ferritin has been covalently conjugated to the external surface of PLGA-NPs exploiting NHS activated carboxylic groups. The results confirmed that nanoparticles decorated with L-Ferritin have many advantages with respect both albumin-decorated and non-decorated particles. Ferritin moieties endow PLGA-NPs with targeting capability, exploiting SCARA5 receptors overexpressed by these tumour cells, that results in an increased paclitaxel cytotoxicity. Moreover, protein coating increased nanoparticle stability thus reducing the fast and aspecific drug release before reaching the target. The theranostic potentiality of the nanoparticles has been demonstrated by evaluating the signal intensity enhancement on T1-weighted MRI images of labelled MCF7 cells. The results werecompared with that obtained with MDA cells used as negative control due to their lower SCARA5 expression. Fil: Turino, Ludmila Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Ruggiero, Maria R.. Universita di Torino; Italia Fil: Stefanìa, Rachele. Universita di Torino; Italia Fil: Cutrin, Juan C.. Universita di Torino; Italia Fil: Aime, Silvio. Universita di Torino; Italia Fil: Geninatti Crich, Simonetta. Universita di Torino; Italia

The combination of different therapeutic modalities is a promising option to combat the recurrence of tumors. In this study, polylactic and polyglycolic acid nanoparticles were used for the simultaneous delivery of a boron-curcumin complex (RbCur) and an amphiphilic gadolinium complex into tumor cells with the aim of performing boron and gadolinium neutron capture therapy (NCT) in conjunction with the additional antiproliferative effects of curcumin. Furthermore, the use of Gd complexes allows magnetic resonance imaging (MRI) assessment of the amount of B and Gd internalized by tumor cells. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles were targeted to ovarian cancer (IGROV-1) cells through folate receptors, by including in the formulation a PEGylated phospholipid functionalized with the folate moiety. NCT was performed on IGROV-1 cells internalizing 6.4 and 78.6 μg g-1 of 10 B and 157 Gd, respectively. The synergic action of neutron treatment and curcumin cytotoxicity was shown to result in a significant therapeutic improvement.

Commercial Gd-containing complexes are often used as MRI reporters in cellular labeling procedures as they are internalized into endosomes by pinocytosis. A methodology has been applied to assess the relative stability of three commercial Gd contrast agents following cellular uptake in fibroblasts and macrophages. It has been found that the acyclic series of Gd MRI contrast agents are degraded much more rapidly than their macrocyclic analogues, following endosomal internalization into living cells. This helps to explain their causal role in the development of nephrogenic systemic fibrosis in renally impaired patients. The methodology has also been applied to assess the fate of Gd-DTPA-BMA-loaded liposomes upon their endosomal internalization. Resistant liposomes prevent the degradation of the complex, whereas liposomes designed to release their payload in the acidic environments show a loss of integrity of Gd-DTPA-BMA analogous to the one observed upon internalization of the free complex.

Inflammation is signaled by the overexpression of epitopes on the vascular endothelium that primarily aim at recruiting immune cells into the inflamed area. The intravascular localization of these biomarkers makes them suitable targets for the MRI visualization of inflammation. Phospholipid-based nanosystems appear excellent candidates in virtue of their good biocompatibility, ability to deliver a high number of imaging units at the target site, and for the easy functionalization with targeting vectors. In this work, phospholipid-based micelles (hydrodynamic diameter of 20 nm) loaded with the amphiphilic Gd(III)-complex Gd-DOTAMA(C18)2 were vectorized with a small peptide able to specifically bind VCAM-1 receptors. The micelles displayed a high longitudinal relaxivity (36.4 s-1mmolGd-1 at 25 °C and 0.7 T). A 1H- and 17O-water relaxometry study indicated that the paramagnetic complex embedded in the nanoparticles adopted two isomeric conformations, likely reflecting the well-known square antiprismatic (SAP) and twisted square antiprismatic (TSAP) configurations typically observed in DOTA-like lanthanide complexes. Interestingly, the TSAP structure, showing a much faster exchange rate for the water molecule coordinated to the metal ion, was the most abundant, thus explaining the high relaxivity of the micellar agent. The systemic administration of the micelles into a lipopolysaccharide-induced murine model of acute inflammation successfully demonstrated the ability of the targeting agents to detect the diseased area by T1 contrast enhanced MRI.

A dynamic contrast enhanced (DCE) approach for tumor photoacoustic (PA) imaging is described. Novel water soluble melanin-based derivatives are synthesized that exhibit good PA properties, stability, safety and accumulation in tumor bearing mice. This melanin derivative is capable to characterize tumor vasculature and to monitor vessel permeability changes upon antiangiogenic treatment. DCE-PA imaging can assess functional response to cancer treatments.

The Gd(III) complexes currently used as MRI contrast agents are hydrophilic agents that distribute in the vascular and extracellular compartments. The visualization of atherosclerotic plaques requires systems endowed with lipophilic characteristics. Several Gd(III) complexes bearing lipophilic substituents have been reported. Among them Gd(III) complexes containing one or two aliphatic chains appear particularly useful for the intended application. These amphiphilic Gd(III) complexes have been incorporated into various types of supramolecular adducts that ensure enough sensibility for their detection in MR images of atherosclerotic plaques. Much attention has been devoted to the use of HDL and LDL Gd-loaded particles. The presence of long aliphatic chain(s) promotes the spontaneous aggregation of these complexes to form micelles that may associate as such to the surface of HDL particles. It has been shown that the transfer of single amphiphilic complexes into the lipidic core of the particles is possible by disassembling the micelles through the formation of “host-guest” adducts with β–cyclodextrin. Gd-loaded liposomes have also been successfully tested in plaque detection as well as perfluoronanoparticles loaded with CEST agents.

This review discusses the main procedures that have been developed for pursuing the task of an efficient cellular labelling with paramagnetic metal complexes for MRI detection. Although most of the work deals with GdIII-based relaxation enhancers it is shown that the emerging class of paraCEST agents can allow the visualization of more cell types in the same MR image. To improve the detection of labelled cells, it is often necessary to deal with the use of nano-sized carriers able to deliver a large number of paramagnetic metal complexes. Finally, selected examples are reported to show how proper design of the paramagnetic complex can offer the way to acquire key information on underlying processes in the labelled cells.

The aim of this work is to design and test an MRI probe (Gd-DOTAtyr-gal) able to report on the gene expression of β-galactosidase (β-Gal) in melanoma cells. The probe consists of a Gd-DOTA reporter bearing on its surface a tyrosine-galactose-pyranose functionality that, upon the release of the sugar moiety, readily transforms, in the presence of tyrosinase, into melanin oligomeric/polymeric mixture. The formation of Gd-DOTA-containing melanin oligomers and polymers is accompanied by a marked increase of the water proton relaxation rate. The steps involving the release of the galactose-pyranose group and the formation of the melanin-like structure have been carefully investigated in vitro by relaxometric and UV-vis measurements. Cellular uptake studies of Gd-DOTAtyr-gal by melanoma cells have shown that the probe enters the cells, and it appears not to be confined in endosomal vesicles. Using B16-F10LacZ transfected cells, the fast formation of paramagnetic melanin-Gd(III)-containing species has been assessed by the measurement of increased longitudinal relaxation rates of the cellular pellets suspensions. The in vitro results have been confirmed in in vivo MRI investigations on murine melanoma tumor bearing mice. Upon direct injection of Gd-DOTAtyr-gal, a good contrast is observed after 5 h post injection in B16-F10LacZ tumors, but not in B16-F10 tumors lacking the β-Gal enzyme. Gd-DOTAtyr-gal in combination with tyrosinase introduces a novel approach for the detection of β-Gal expression by MRI in vivo.

Optoacoustic imaging emerged in early 1990s as a new biomedical imaging technology that generates images by illuminating tissues with short laser pulses and detecting resulting ultrasound waves. This technique takes advantage of the spectroscopic approach to molecular imaging, and delivers high-resolution images in the depth of tissue. Resolution of the optoacoustic imaging is scalable, so that biomedical systems from cellular organelles to large organs can be visualized and, more importantly, characterized based on their optical absorption coefficient, which is proportional to the concentration of absorbing chromophores. Optoacoustic imaging was shown to be useful in both preclinical research using small animal models and in clinical applications. Applications in the field of molecular imaging offer abundant opportunities for the development of highly specific and effective contrast agents for quantitative optoacoustic imaging. Recent efforts are being made in the direction of nontoxic biodegradable contrast agents (such as nanoparticles made of melanin) that are potentially applicable in clinical optoacoustic imaging. In order to increase the efficiency and specificity of contrast agents and probes, they need to be made smart and capable of controlled accumulation in the target cells. This review was written in recognition of the potential breakthroughs in medical optoacoustic imaging that can be enabled by efficient and nontoxic melanin-based optoacoustic contrast agents.

Glucan particles (GPs) are monodisperse microspheres derived from baker's yeast and represent an interesting class of microcarriers for theranostic applications as they show a high affinity toward immune system cells. The typical loading strategy was to harness the ability of the molecule to be loaded to interact with nano-/microassembled systems through electrostatic or hydrophobic forces. However, small water-soluble chemicals could not be steadily retained by the leaky shell of GPs. In this work, we propose an alternative loading approach for small water-soluble compounds that is based on their entrapment in the aqueous core of liposomes that are directly formed into the microparticles through the reverse phase evaporation method (REV). The construct obtained may act as biocompatible carrier to deliver and release, even in a triggerable way, bioactive compounds.

Quantitative measurement of marker expression in diseased cells is still a topic of considerable interest and different methodologies are currently under intense scrutiny. This work aims at developing an in vitro diagnostic method based on the release of paramagnetic species from relaxometrically "silent" liposomes operated by the action of a phospholipase A2 (PLA2) previously targeted to the epitope of interest. The released paramagnetic species causes an increase of the longitudinal water proton relaxation rate proportional to the number of PLA2 bound to the cell outer surface. The sensitivity of the herein proposed method, named R-ELISA, was attempted in the detection of folate receptor expression on human ovarian cancer cells by functionalizing PLA2 with folic acid. Receptor/cell number of 8.3×10(5) has been measured on IGROV-1 cells. The R-ELISA assay can detect nanomolar cell suspension receptor concentrations and has been validated by well-established spectrofluorimetric procedures.

complexes has been investigated both in vitro and in vivo. The complexes differ in one donor group of the coordination cage (carboxylate versus carboxoamide), and in the length (C12 versus C18) and the point of attachment of the aliphatic chains to the chelators. The in vitro 1 H relaxometric characterisation of the systems, performed with a newly developed relaxation model that takes into account the contributions of the Gd III chelates pointing in- and outwards of the liposome, indicates that their efficacy is optimal in the range 0.5–1.5 T. The tetracarboxylic C12-containing liposomes (LIPO-GdDOTA(GAC12)2; GA = glutaric acid) are four-fold more efficient than the monoamide C18-based analogue (LIPO-GdDOTAMA(C18)2). Such a difference is also found in vivo at 1 T in a melanoma tumour model on mice. A few hours after intravenous injection, the T1 contrast enhancement in the organs where the nanovesicles typically distribute (liver, spleen, kidneys and tumour) is much higher for LIPO-GdDOTA(GAC12)2. Interestingly, after about 7 h post-injection the contrast enhancement observed for the more efficient liposomes decreases rapidly and becomes lower than for LIPO-GdDOTAMA(C18)2. The relaxometric data and the quantification of the Gd III complexes in the organs, determined ex vivo by inductively coupled plasma mass spectrometry, indicate that: 1) the differences in the contrast enhancement can be attributed to the different rate of water exchange and rotational dynamics of the Gd complexes, and 2) the rapid contrast decrease is caused by a faster clearance of GdDOTA(GAC12)2 from the organs. This is also confirmed by using a newly synthesised amphiphilic cyanine-based fluorescent probe (Cy5(C16)2). As one of the main limitations for the clinical translation of liposomes incorporating amphiphilic imaging agents is related to their very long persistence in the body, the results reported herein suggest that the clearance of the probes can be accelerated, without compromising their role, by a proper selection of the lipophilic portion of the incorporated compound as well as of the ligand site at which the aliphatic tails are linked. Then, GdDOTA(GAC12)2 complex may represent a good candidate for the development of improved MRI protocols based on paramagnetically labelled lipidic nanoparticles.

This review discusses the main procedures that have been developed for pursuing the task of an efficient cellular labelling with paramagnetic metal complexes for MRI detection. Although most of the work deals with GdIII-based relaxation enhancers it is shown that the emerging class of paraCEST agents can allow the visualization of more cell types in the same MR image. To improve the detection of labelled cells, it is often necessary to deal with the use of nano-sized carriers able to deliver a large number of paramagnetic metal complexes. Finally, selected examples are reported to show how proper design of the paramagnetic complex can offer the way to acquire key information on underlying processes in the labelled cells.