Search

One possibility for the non-invasive imaging of encapsulated cell grafts is to label the lumen of cell embedding capsules with a redox-responsive probe, as an increased extracellular reducing potential can be considered as a marker of hypoxia-induced necrosis. A Gd(III)-HPDO3A-like chelate has been conjugated to glycol-chitosan through a redox-responsive disulphide bond to obtain a contrast agent for Magnetic Resonance Imaging (MRI). Such a compound can be interspersed with fibroblasts within the lumen of alginate-chitosan capsules. Increasing reducing conditions within the extracellular microenvironment lead to the reductive cleavage of the disulphide bond and to the release of gadolinium in the form of a low molecular weight, non-ionic chelate. The efflux of such chelate from capsules is readily detected by a decrease of contrast enhancement in T 1 -weighted MR images.

Mobile proton-containing solutes can be detected by MRI by the chemical exchange saturation transfer (CEST) method. CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, shifted by a paramagnetic shift reagent. The chemical shift of the intraliposomal water resonance (δIL ) is affected by the overall shape of the supramolecular system. δIL of a spherical LipoCEST acts as a sensitive reporter of the distribution of streptavidin proteins anchored at the liposome surface by biotinylated phospholipids. This finding prompted the design of a MMP-2 responsive LipoCEST agent as the streptavidin moieties can be released from the liposome surfaces when a properly tailored enzyme-cleavable peptide is inserted on the phospholipids before the terminal biotin residues. δIL reports on the overall changes in the supramolecular architecture associated to the cleavage carried out by MMP-2.

Amphiphilic Janus-dendrimers are able to self-assemble into nanosized vesicles named dendrimersomes. We recently synthesized the 3,5-C12-EG-(OH)4 dendrimer that generates dendrimersomes with very promising safety and stability profiles, that can be loaded with different contrast agents for in vivo imaging. In this contribution, nanovesicles were loaded with both the Magnetic Resonance Imaging (MRI) reporter GdDOTAGA(C18)2 and the glucocorticoid drug Prednisolone Phosphate (PLP), in order to test their effective potential as theranostic nanocarriers on murine melanoma tumour models. The incorporation of GdDOTAGA(C18)2 into the membrane resulted in dendrimersomes with a high longitudinal relaxivity (r1=39.1mM-1s-1, at 310K and 40MHz) so that, after intravenous administration, T1-weighted MRI showed a consistent contrast enhancement in the tumour area. Furthermore, the nanovesicles encapsulated PLP with good efficiency and displayed anti-tumour activity both in vitro and in vivo, thus enabling their practical use for biomedical theranostic applications.

Cell scaffolds are often used in cell transplantation as they provide a solid structural support to implanted cells and can be bioengineered to mimic the native extracellular matrix. Gadolinium fluoride nanoparticles (Gd-NPs) as a contrast agent for Magnetic Resonance Imaging (MRI) were incorporated into poly(lactide-co-glycolide)/chitosan scaffolds to obtain Imaging Labelled Cell Scaffolds (ILCSs), having the shape of hollow spherical/ellipsoidal particles (200&ndash, 600 &mu, m diameter and 50&ndash, 80 &mu, m shell thickness). While Gd-NPs incorporated into microparticles do not provide any contrast enhancement in T1-weighted (T1w) MR images, ILCSs can release Gd-NPs in a controlled manner, thus activating MRI contrast. ILCSs seeded with human mesenchymal stromal cells (hMSCs) were xenografted subcutaneously into either immunocompromised and immunocompetent mice without any immunosuppressant treatments, and the transplants were followed-up in vivo by MRI for 18 days. Immunocompromised mice showed a progressive activation of MRI contrast within the implants due to the release of Gd-NPs in the extracellular matrix. Instead, immunocompetent mice showed poor activation of MRI contrast due to the encapsulation of ILCSs within fibrotic capsules and to the scavenging of released Gd-NPs by phagocytic cells. In conclusion, the MRI follow-up of cell xenografts can report the host cell response to the xenograft. However, it does not strictly report on the viability of transplanted hMSCs.

The redox microenvironment within a cell graft can be considered as an indicator to assess whether the graft is metabolically active or hypoxic. We present a redox-responsive MRI probe based on porous silica microparticles whose surface has been decorated with a Gd-chelate through a disulphide bridge. Such microparticles are designed to be interspersed with therapeutic cells within a biocompatible hydrogel. The onset of reducing conditions within the hydrogel is paralleled by an increased clearance of Gd, that can be detected by MRI.

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.

Mobile proton-containing solutes can be detected by MRI by the chemical exchange saturation transfer (CEST) method. CEST sensitivity is dramatically enhanced by using, as exchanging protons, the water molecules confined inside liposomes, shifted by a paramagnetic shift reagent. The chemical shift of the intraliposomal water resonance (δ

// Cecilia Roux 1, 2 , Chiara Riganti 3 , Sammy Ferri Borgogno 1, 2 , Roberta Curto 1, 2 , Claudia Curcio 1, 2 , Valeria Catanzaro 4 , Giuseppe Digilio 4 , Sergio Padovan 5 , Maria Paola Puccinelli 6 , Monica Isabello 6 , Silvio Aime 2, 7 , Paola Cappello 1, 2, 7, * and Francesco Novelli 1, 2, 7, * 1 Center for Experimental Research and Medical Studies, Citta della Salute e della Scienza di Torino, 10126 Turin, Italy 2 Department of Molecular Biotechnology and Health Sciences, University of Turin, 10126 Turin, Italy 3 Department of Oncology, University of Turin, 10126 Turin, Italy 4 Department of Science and Technologic Innovation, Universita del Piemonte Orientale “A. Avogadro”, 15121 Alessandria, Italy 5 Institute for Biostructures and Bioimages (CNR) c/o Molecular Biotechnology Center, 10126 Turin, Italy 6 Clinical Biochemistry Laboratory, Citta della Salute e della Scienza di Torino, 10126 Turin, Italy 7 Molecular Biotechnology Center, University of Turin, 10126 Turin, Italy * These authors have contributed equally to this work Correspondence to: Francesco Novelli, email: franco.novelli@unito.it Paola Cappello, email: paola.cappello@unito.it Keywords: PDAC; amino acid; circulating biomarkers; pancreatitis; diagnosis Received: March 24, 2017 Accepted: August 04, 2017 Published: August 24, 2017 ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is becoming the second leading cause of cancer-related death in the Western world. The mortality is very high, which emphasizes the need to identify biomarkers for early detection. As glutamine metabolism alteration is a feature of PDAC, its in vivo evaluation may provide a useful tool for biomarker identification. Our aim was to identify a handy method to evaluate blood glutamine consumption in mouse models of PDAC. We quantified the in vitro glutamine uptake by Mass Spectrometry (MS) in tumor cell supernatants and showed that it was higher in PDAC compared to non-PDAC tumor and pancreatic control human cells. The increased glutamine uptake was paralleled by higher activity of most glutamine pathway-related enzymes supporting nucleotide and ATP production. Free glutamine blood levels were evaluated in orthotopic and spontaneous mouse models of PDAC and other pancreatic-related disorders by High-Performance Liquid Chromatography (HPLC) and/or MS. Notably we observed a reduction of blood glutamine as much as the tumor progressed from pancreatic intraepithelial lesions to invasive PDAC, but was not related to chronic pancreatitis-associated inflammation or diabetes. In parallel the increased levels of branched-chain amino acids (BCAA) were observed. By contrast blood glutamine levels were stable in non-tumor bearing mice. These findings demonstrated that glutamine uptake is measurable both in vitro and in vivo . The higher in vitro avidity of PDAC cells corresponded to a lower blood glutamine level as soon as the tumor mass grew. The reduction in circulating glutamine represents a novel tool exploitable to implement other diagnostic or prognostic PDAC biomarkers.