Non-invasive quantitative imaging of hepatocellular carcinoma growth in mice by micro-CT using liver-targeted iodinated nano-emulsions

Hepatocellular carcinoma (HCC) is the only cancer for which non-invasive diagnosis is recognized by international guidelines. Contrast agent free ultrasound imaging, computed tomography (CT) and/or magnetic resonance imaging are techniques used for early detection and confirmation. Clinical evidence depicts that CT is 30% less precise as compared to MRI for detection of small tumors. In our work, we have reported some novel tools that can enhance the sensitivity and precision of CT applied to preclinical research (micro-CT). Our system, containing non-toxic nano-droplets loaded with iodine has high contrasting properties, liver and hepatocyte specificity and strong liver persistence. Micro-CT was performed on HCC model implanted in nude mice by intrahepatic injection. Contrast agent was administrated intravenously. This method allows an unprecedented high precision of detection, quantitative measurement of tumor volume and quantitative follow-up of the tumor development.PMC565532

Improvement of hyaluronic acid enzymatic stability by the grafting of amino-acids

Injection of hyaluronic acid (HA)-based hydrogels has proven to provide many therapeutic benefits. To increase the stability of HA-based products against enzymatic digestion, we modified hyaluronic acid by grafting various amino acids on its carboxylic group and then evaluated the enzymatic stability of the various conjugates in presence of a hyaluronidase. Our results showed that all amino acid-modified HA polymers were more resistant to degradation compared to the native HA albeit with variation according to the amino acids. Amino acids with carboxylate groups such as aspartic acid or with hydroxyl functions (threonine, serine or tyrosine) conferred a particularly strong resistance to HA towards enzymatic digestion. The HA-amino acid products were then cross-linked with butanediol diglycidyl ether (BDDE). The swelling properties of the formed hydrogels appeared close to native HA whereas the increased resistance towards hyaluronidase digestion remained. These results suggest that amino acid-modified HA derivatives can become promising material for viscosupplementation or drug delivery

Reversing the course of the competitive adsorption between a phospholipid and albumin at an air-water interface

When bovine serum albumin (BSA) and dipalmitoylphosphatidylcholine (DPPC) compete for occupation of an air–water interface, the protein rapidly colonizes the interface, effectively hindering the access of the phospholipid, a situation encountered in certain pulmonary conditions. We found that DPPC can totally and irreversibly displace BSA from the surface of a gas bubble when submitted to sustained sinusoidal oscillations at frequencies in the range of those encountered in respiration, and this without recourse to any additive

Do iodinated nano-emulsions designed for preclinical vascular imaging alter the vascular reactivity in rat aorta?

This study proposes a new methodology to evaluate the putative consequences of the long-lasting circulation in the blood pool of nanoparticulate systems widely used in nanomedicine, Indeed, the blood pool contrast agent for micro-computed tomography, i.e. iodinated nano-emulsions, have recently been developed, for their great potential in medical applications such as advanced diagnosis, image-guided surgery, personalized medicine or theragnostics. Stealth nanoparticles exhibit a low recognition by the reticuloendothelial system, resulting in a prolonged circulation in the bloodstream and long-lasting contact with the endothelium. Therefore, the aim of the present study is to determine whether this prolonged interaction could induce an alteration of the vascular reactivity in rat aorta. The Iodinated nano-emulsions were intravenously injected in anesthetized rats. After 1h of contrast agent circulation in the blood pool, the thoracic aorta was removed for the study of vascular reactivity. These animals were compared with control (untreated) rats and a third group of rats receiving an injection of phosphate buffered saline (i.e. dispersing phase of the nano-emulsions). Phenylephrine-induced concentration-dependent contractions of the isolated rat thoracic aorta were not modified whatever the group. Sodium nitroprusside (a nitric oxide (NO) donor)-induced relaxations of endothelium-denuded aorta were also unaltered in response to the different administrations. In contrast, in comparison with control animals, endothelium-dependent NO-mediated relaxations to acetylcholine were significantly impaired in thoracic aorta from PBS-treated rats, but not in animals receiving the iodinated nano-emulsion. In addition, neither isoprenaline-induced nor levcromakalim-induced relaxations were modified in the aorta from the three groups of animals. These findings indicate that even with a long-lasting residence time of the iodinated nano-emulsion in the blood flow, these iodinated nano-emulsions do not alter the vascular reactivity and thus can be used as contrast agent for preclinical vascular imaging on small laboratory animals

A Nonpolar, Nonamphiphilic Molecule Can Accelerate Adsorption of Phospholipids and Lower Their Surface Tension at the Air/Water Interface

The adsorption dynamics of a series of phospholipids (PLs) at the interface between an aqueous solution or dispersion of the PL and a gas phase containing the nonpolar, nonamphiphilic linear perfluorocarbon perfluorohexane (PFH) was studied by bubble profile analysis tensiometry. The PLs investigated were dioctanoylphosphatidylcholine (DiC8‐PC), dilaurylphosphatidylcholine, dimyristoylphosphatidylcholine, and dipalmitoylphosphatidylcholine. The gas phase consisted of air or air saturated with PFH. The perfluorocarbon gas was found to have an unexpected, strong effect on both the adsorption rate and the equilibrium interfacial tension (γeq) of the PLs. First, for all of the PLs, and at all concentrations investigated, the γeq values were significantly lower (by up to 10 mN m−1) when PFH was present in the gas phase. The efficacy of PFH in decreasing γeq depends on the ability of PLs to form micelles or vesicles in water. For vesicles, it also depends on the gel or fluid state of the membranes. Second, the adsorption rates of all the PLs at the interface (as assessed by the time required for the initial interfacial tension to be reduced by 30 %) are significantly accelerated (by up to fivefold) by the presence of PFH for the lower PL concentrations. Both the surface‐tension reducing effect and the adsorption rate increasing effect establish that PFH has a strong interaction with the PL monolayer and acts as a cosurfactant at the interface, despite the absence of any amphiphilic character. Fitting the adsorption profiles of DiC8‐PC at the PFH‐saturated air/aqueous solution interface with the modified Frumkin model indicated that the PFH molecule lay horizontally at the interface

Counteracting the inhibitory effect of proteins towards lung surfactant substitutes: a fluorocarbon gas helps displace albumin at the air/water interface:

Perfluorohexane gas lowers the kinetic barrier that opposes the displacement of albumin by dipalmitoylphosphatidylcholine at the air/water interface submitted to sinusoidal oscillations at frequencies in the range of those encountered in respiration

Improved size-tunable preparation of polymeric nanoparticles by microfluidic nanoprecipitation

International audienceSize-tunable polymeric nanoparticles have been successfully produced by a microfluidic-assisted nanoprecipitation process. A multilamination micromixer has been chosen to fabricate continuously nanoparticles of methacrylic polymers. Various operating conditions, such as the polymer concentration, the amount of non-solvent and the characteristics of the raw polymer (molecular weight and architecture: linear vs. branched) have been investigated. Their influences on the final particle size, ranging from 76 to 217 nm, have been correlated to the mechanisms leading to the formation of nanoparticles. In this type of microfluidic device, mixing mainly operates by diffusion mass transfer, helped by hydrodynamic focusing. The effect of micromixing on the size of particles has also been shown experimentally and supported by a computational fluid dynamics (CFD) study. A mixing criterion has been defined and numerically calculated to corroborate the effect of the flow rate of polymer solution on the particles size. An increase in the polymer solution flow rate increases the value of this mixing criterion, resulting in smaller nanoparticles

Functionalization of nano-emulsions with an amino-silica shell at the oil-water interface

Nano-emulsions are very promising nano-carriers with high potential for loading lipophilic drugs. However, the surface of oil nano-droplets is a dynamic oil/water interface stabilized by surfactants, and its chemical modification to graft ligands is highly challenging. In this study we developed a new protocol for modification of the nano-droplets surface through a silica shell terminated by amine functions. It enabled preparation of nanocapsules of 65, 85 and 120 nm diameters with a surface coverage of ca. 2 amino groups per nm(2). The nanocapsule surface was then functionalized (41% efficiency) by a model fluorescent ligand (coumarin blue) with a carboxylic function. The evidence for the successful grafting was provided by spectrofluorometry, Forster resonance energy transfer, atomic force microscopy coupled with fluorescence imaging and fluorescence correlation spectroscopy. This simple protocol for surface functionalization of the liquid/liquid interface of lipid droplets may constitute a real advance regarding potential applications that need efficient decoration of droplets with ligands

Biodistribution of x-ray iodinated contrast agent in nano-emulsions is controlled by the chemical nature of the oily core

In this study, we investigated the role of the chemical nature of the oil droplet core of nano-emulsions used as contrast agents for X-ray imaging on their pharmacokinetics and biodistribution. To this end, we formulated PEGylated nano-emulsions with two iodinated oils (i.e., iodinated monoglyceride and iodinated castor oil) and compared them with another iodinated nano-emulsion based on iodinated vitamin E. By using dynamic light scattering and transmission electron microscopy, the three iodinated nano-emulsions were found to exhibit comparable morphologies, size, and surface composition. Furthermore, they were shown to be endowed with very high iodine concentration, which leads to stronger X-ray attenuation properties as compared to the commercial iodinated nano-emulsion Fenestra VC. The three nano-emulsions were i.v. administered in mice and monitored by microcomputed tomography (micro-CT). They showed high contrast enhancement in blood with similar half-life around 6 h but very different accumulation sites. While iodinated monoglycerides exhibited low accumulation in liver and spleen, high accumulation in spleen was observed for iodinated castor oil and in liver for vitamin E. These data clearly highlighted the important role of the oil composition of the nano-emulsion core to obtain strong X-ray contrast enhancement in specific targets such as liver, spleen, or only blood. These differences in biodistribution were partly attributed to differences in the uptake of the nanodroplets by the macrophages in vitro. Another key feature of these nano-emulsions is their long half-elimination time (several weeks), which offers sufficient retention for micro-CT imaging. This work paves the way for the design of nanoparticulate contrast agents for X-ray imaging of selected organs