A relaxometric method for the assessment of intestinal permeability based on the oral administration of gadolinium-based MRI contrast agents.

Herein, a new relaxometric method for the assessment of intestinal permeability based on the oral administration of clinically approved gadolinium (Gd)-based MRI contrast agents (CAs) is proposed. The fast, easily performed and cheap measurement of the longitudinal water proton relaxation rate (R1) in urine reports the amount of paramagnetic probe that has escaped the gastrointestinal tract. The proposed method appears to be a compelling alternative to the available methods for the assessment of intestinal permeability. The method was tested on the murine model of dextran sulfate sodium (DSS)-induced colitis in comparison with healthy mice. Three CAs were tested, namely ProHance®, MultiHance® and Magnevist®. Urine was collected for 24 h after the oral ingestion of the Gd-containing CA at day 3-4 (severe damage stage) and day 8-9 (recovery stage) after treatment with DSS. The Gd content in urine measured by (1)H relaxometry was confirmed by inductively coupled plasma-mass spectrometry (ICP-MS). The extent of urinary excretion was given as a percentage of excreted Gd over the total ingested dose. The method was validated by comparing the results obtained with the established methodology based on the lactulose/mannitol and sucralose tests. For ProHance and Magnevist, the excreted amounts in the severe stage of damage were 2.5-3 times higher than in control mice. At the recovery stage, no significant differences were observed with respect to healthy mice. Overall, a very good correlation with the lactulose/mannitol and sucralose results was obtained. In the case of MultiHance, the percentage of excreted Gd complex was not significantly different from that of control mice in either the severe or recovery stages. The difference from ProHance and Magnevist was explained on the basis of the (known) partial biliary excretion of MultiHance in mice.

Design and testing of paramagnetic liposome-based CEST agents for MRI visualization of payload release on pH-induced and ultrasound stimulation.

The development of nanomedicines in cancer therapy is constantly growing because of the advantages associated with the use of nanosized drug delivery systems. Among them, the possibility of accurate spatiotemporal control of the release of the chemotherapeutic from the carrier is one of the most interesting and clinically relevant. To further improve the therapy outcome, the clinical translation of imaging protocols for the in vivo visualization of the release step is of paramount importance. In this work, the combination of the great chemical versatility of liposomes and the outstanding potential of MRI chemical exchange saturation transfer agents has been successfully harnessed to image the selective release of the liposomal content stimulated by endogenous (variation of pH) and externally applied (nonfocused ultrasound) stimuli. The use of clinically safe components (both liposomes and MRI agents) and the good results obtained in vitro hold promise for a successful future in vivo translation.

In vivo MRI visualization of release from liposomes triggered by local application of pulsed low-intensity non-focused ultrasound.

The work aimed at developing a MRI-guided protocol for the visualization of the release of material entrapped in liposomes stimulated by the local application of pulsed low-intensity non-focused ultrasound (pLINFU). The task was achieved by formulating liposomes filled up with the clinically approved paramagnetic agent gadoteridol, because the release of the agent from the nanovesicles is accompanied by a significant MRI signal enhancement. The protocol was validated in vivo on mice-bearing subcutaneous syngeneic B16 melanoma and i.v. injected with the paramagnetic liposomes. Upon exposing tumor to pLINFU (3MHz, insonation time 2min, duty cycle 50%) few minutes after liposomes injection, a signal enhancement of ca. 35% was detected. The effective release of the agent was confirmed by the strong enhancement measured in kidneys calyx and bladder due to the rapid renal excretion of the agent released in the tumor. FROM THE CLINICAL EDITOR: In this paper, a pulsed low-intensity non-focused ultrasound-based technique was used to release a paramagnetic MRI contrast agent from liposomes, demonstrating the feasibility of this triggered release system in a mouse melanoma model for future research applications.

Successful in vivo MRI tracking of MSCs labeled with Gadoteridol in a Spinal Cord Injury experimental model.

In this study, murine Mesenchymal Stem Cells (MSCs) labeled with the clinically approved MRI agent Gadoteridol through a procedure based on the hypo-osmotic shock were successfully tracked in vivo in a murine model of Spinal Cord Injury (SCI). With respect to iso-osmotic incubations, the hypo-osmotic labeling significantly increased the Gd(3+) cellular uptake, and enhanced both the longitudinal relaxivity (r1) of the intracellular Gadoteridol and the Signal to Noise Ratio (SNR) measured on cell pellets, without altering the biological and functional profile of cells. A substantial T1 Contrast Enhancement after local transplantation of 3.0×10(5) labeled cells in SCI mice enabled to follow their migratory dynamics in vivo for about 10days, and treated animals recovered from the motor impairment caused by the injury, indicating unaltered therapeutic efficacy. Finally, analytical and histological data corroborated the imaging results, highlighting the opportunity to perform a precise and reliable monitoring of the cell-based therapy.

Diolein Based Nanostructures as Targeted Theranostics.

Diolein based non-targeted theranostic nanoparticles (DO-NPs) containing 10%wt of the amphiphilic Gadolinium complex (C18)2DTPA(Gd), and targeted NPs, obtained by introducing growing amounts (3% wt, 6% wt or 10% wt) of (C18)2-Peg3000- FA in the sample composition, have been studied for their in vitro and in vivo properties. Cellular binding was studied by lCP-MS analysis of the Gadolinium content and by Surface Plasmon Resonance (SPR) assays. The best formulation in terms of selectivity towards IGROV-1 cells with respect to non-targeted DO-NPs, was that containing 3% (C18)2Peg3000- FA (P < 0.01). Cytotoxic studies and confocal microscopy analysis of IGROV-1 cells indicate high selective properties of the targeted doxorubicin (DOX) loaded NPs. Nanoparticles described here represent the first example in which a targeted carrier characterized by a stable foamy mesophase, provided by the Diolein component, combine the therapeutic effect due to the anticancer drug doxorubicin, with the imaging properties provided by paramagnetic gadolinium complexes for MRI. As evidenced by T(1w), and T(2w) MRI images and by the in vivo antitumor effect in IGROV-1 tumor-bearing mice, DO-NP3-FA/DOX provides very high therapeutic efficacy with a tumor growth regression of 80% and 50% higher as compared to the mice treated with saline solution and with Doxil, respectively.

Mesoporous silica nanoparticles functionalized with fluorescent and MRI reporters for the visualization of murine tumors overexpressing αvß3 receptors.

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 αvß3 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 αvß3 integrin receptors.

Gadolinium-doped LipoCEST agents: a potential novel class of dual 1H-MRI probes.

A novel class of paramagnetic liposome-based systems acting as dual T(1) and CEST (1)H-MRI contrast agents is described. The vesicles contain a shift reagent in the aqueous core and a Gd-complex on the external surface conjugated through a biodegradable linker. As such, the probe can generate T(1) contrast only, but after the cleavage and removal of the Gd-coating, the CEST contrast is switched on.