Theranostic MRI liposomes for magnetic targeting and ultrasound triggered release of the antivascular CA4P.

Theranostic nanocarriers of antivascular drug encapsulated in thermosensitive ultramagnetic liposomes can be advantageously designed to provide a locally high concentration and an active delivery, with image-guided Magnetic Resonance Imaging (MRI) so as to reliably cure tumor. We propose a novel therapeutic strategy consisting of the magnetic accumulation of Ultra Magnetic Liposomes (UML) followed by High-Intensity Focused Ultrasound (HIFU) to trigger the release of an antivascular agent monitored by MRI. For this purpose, we co-encapsulated Combretastatin A4 phosphate (CA4P), a vascular disrupting agent, in the core of UML to obtain CA4P-loaded thermosensitive Ultra Magnetic Liposomes (CA4P-UML). To assess the HIFU parameters, the CA4P release has been triggered in vitro by local heating HIFU at the lipids transition temperature. Morphology of endothelial cells was assessed to evaluate the effect of encapsulated versus non-encapsulated CA4P. The efficiency of a treatment combining the magnetic targeting of CA4P-UML with the CA4P release triggered by HIFU was studied in CT26 murine tumors. Tumor perfusion and volume regression parameters were monitored by multiparametric quantitative anatomical and dynamic in vivo MRI at 7 T. Additionally, vascularization and cellularity were evaluated ex-vivo by histology. This thorough investigation showed that the combined treatment exhibited a full benefit. A 150-fold improvement compared with the chemotherapy alone was obtained using a magnetic targeting of CA4P-UML triggered by HIFU, and was consistent with an expected effect on vascularization 24 h after treatment.

In Vivo Evaluation of Magnetic Targeting in Mice Colon Tumors with Ultra-Magnetic Liposomes Monitored by MRI.

PURPOSE: The development of theranostic nanocarriers as an innovative therapy against cancer has been improved by targeting properties in order to optimize the drug delivery to safely achieve its desired therapeutic effect. The aim of this paper is to evaluate the magnetic targeting (MT) efficiency of ultra-magnetic liposomes (UML) into CT26 murine colon tumor by magnetic resonance imaging (MRI). PROCEDURES: Dynamic susceptibility contrast MRI was applied to assess the bloodstream circulation time. A novel semi-quantitative method called %I0.25, based on the intensity distribution in T2*-weighted MRI images was developed to compare the accumulation of T2 contrast agent in tumors with or without MT. To evaluate the efficiency of magnetic targeting, the percentage of pixels under the intensity value I0.25 (I0.25 = 0.25(Imax - Imin)) was calculated on the intensity distribution histogram. RESULTS: This innovative method of processing MRI images showed the MT efficiency by a %I0.25 that was significantly higher in tumors using MT compared to passive accumulation, from 15.3 to 28.6 %. This methodology was validated by ex vivo methods with an iron concentration that is 3-fold higher in tumors using MT. CONCLUSIONS: We have developed a method that allows a semi-quantitative evaluation of targeting efficiency in tumors, which could be applied to different T2 contrast agents.

One-pot direct synthesis for multifunctional ultrasmall hybrid silica nanoparticles.

Ultrasmall silica nanoparticles (NPs), having hydrodynamic diameters under 10 nm are promising inorganic platforms for imaging and therapeutic applications in medicine. Herein is described a new way for synthesizing such kind of NPs in a one-pot scalable protocol. These NPs bear DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) ligands on their surface that can chelate different metals suitable for a wide variety of biomedical applications. By varying the ratio of the precursors, the hydrodynamic diameters of the particles can be controlled over the range of 3 to 15 nm. The resulting NPs have been characterized extensively by complementary techniques like dynamic light scattering (DLS), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), mass spectrometry (MS), phosphorescence titration, photophysical measurements, relaxometry and elemental analysis to elucidate their structures. Chelation of gadolinium (Gd) allowed its use as an effective intravenous contrast agent in MRI and was illustrated in mice bearing colorectal CT26 tumors. The new particle appears to sufficiently accumulate in the tumors and efficiently clear out of animal bodies through kidneys. This new synthesis is an original, time/material-saving and very flexible process that can be applied for creating versatile ultrasmall multifunctional nanomedicines.

Gadolinium and Platinum in Tandem: Real-time Multi-Modal Monitoring of Drug Delivery by MRI and Fluorescence Imaging.

A novel dual-imaging cisplatin-carrying molecular cargo capable of performing simultaneous optical and MR imaging is reported herein. This long-lasting MRI contrast agent (r1 relaxivity of 23.4 mM-1s-1 at 3T, 25 oC) is a photo-activated cisplatin prodrug (PtGdL) which enables real-time monitoring of anti-cancer efficacy. PtGdL is a model for monitoring the drug delivery and anti-cancer efficacy by MRI with a much longer retention time (24 hours) in several organs such as renal cortex and spleen than GdDOTA and its motif control GdL. Upon complete release of cisplatin, all PtGdL is converted to GdL enabling subsequent MRI analyses of therapy efficacy within its reasonably short clearance time of 4 hours. There is also responsive fluorescence enhancement for monitoring by photon-excitation.

Mechanostereoselective One-Pot Synthesis of Functionalized Head-to-Head Cyclodextrin [3]Rotaxanes and Their Application as Magnetic Resonance Imaging Contrast Agents.

A versatile, five-component, one-pot synthesis of cyclodextrin (CD) [3]rotaxanes using copper-catalyzed azide-alkyne cycloaddition has been developed. Head-to-head [3]rotaxanes of α-CD selectively functionalized by one or two gadolinium 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid monoamide complexes were obtained mechanostereoselectively. The magnetic resonance imaging efficiency, expressed by the longitudinal proton relaxivity of the rotaxanes, was significantly improved as compared to the functionalized CD. In vitro and in vivo preclinical studies showed a higher contrast and retention in the kidney than gadolinium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid complex, demonstrating the potential of these rotaxanes as MRI contrast agent.

High resolution 3D imaging of ex-vivo biological samples by micro CT.

Non-destructive volume visualization can be achieved only by tomographic techniques, of which the most efficient is the x-ray micro computerized tomography (µCT). High resolution µCT is a very versatile yet accurate (1-2 microns of resolution) technique for 3D examination of ex-vivo biological samples(1, 2). As opposed to electron tomography, the µCT allows the examination of up to 4 cm thick samples. This technique requires only few hours of measurement as compared to weeks in histology. In addition, µCT does not rely on 2D stereologic models, thus it may complement and in some cases can even replace histological methods(3, 4), which are both time consuming and destructive. Sample conditioning and positioning in µCT is straightforward and does not require high vacuum or low temperatures, which may adversely affect the structure. The sample is positioned and rotated 180° or 360°between a microfocused x-ray source and a detector, which includes a scintillator and an accurate CCD camera, For each angle a 2D image is taken, and then the entire volume is reconstructed using one of the different available algorithms(5-7). The 3D resolution increases with the decrease of the rotation step. The present video protocol shows the main steps in preparation, immobilization and positioning of the sample followed by imaging at high resolution.

Vascular perfusion of human lung cancer in a rat orthotopic model using dynamic contrast-enhanced magnetic resonance imaging.

Lung cancer is the leading cause of death among cancers. Early detection and diagnosis present a major goal in the efforts to improve survival rates of lung cancer patients. Changes in angiogenic activity and microvascular perfusion properties in cancers can serve as markers of malignancy. The aim of this study was to employ MRI means to measure the microvascular perfusion parameters of orthotopic nonsmall cell lung cancer, using the experimental rat model. Anatomical and dynamic contrast-enhanced lung images were acquired at high spatial resolution, and registered and analyzed, pixel by pixel and globally, by means of a model-based algorithm. The MRI output yielded color-coded parametric images of the influx and efflux transcapillary transfer constants that indicated rapid microvascular perfusion. The transfer constants were about 1 order of magnitude higher than those found in other tumors or in nonorthotopic lung cancer, with the influx constant median value of 0.42 min(-1) and the efflux constant median value of 1.61 min(-1). The rapid perfusion was in accord with the immunostaining of the capillaries, which suggested the tumor exploitation of the existing alveolar vessels. The results showed that high resolution, dynamic, contrast-enhanced MRI is an effective tool for the quantitative measurement of spatial and temporal changes in lung cancer perfusion and vasculature.