Mixing versus Polymer Chemistry in the Synthesis of Loaded Polymer Nanoparticles through Nanoprecipitation.

Polymer nanoparticles (NPs) loaded with drugs and contrast agents have become key tools in the advancement of nanomedicine, requiring robust technologies for their synthesis. Nanoprecipitation is a particularly interesting technique for the assembly of loaded polymer NPs, which is well-known to proceed under kinetic control, with a strong influence of the assembly conditions. On the other hand, the nature of the used polymer also influences the outcome of nanoprecipitation. Here, we investigated systematically the relative effects of mixing of the organic and aqueous phases and polymer chemistry on the formation of polymer nanocarriers. For this, two mixing schemes, manual mixing and microfluidic mixing using an impact-jet micromixer, were first evaluated, showing mixing times of several tens of milliseconds and a few milliseconds, respectively. Copolymers of ethyl methacrylate with charged and hydrophilic groups and different polyesters (poly(d-l-lactide-co-glycolide) and poly(lactic acid)) were combined with a fluorescent dye salt and tested for particle assembly using these "slow" and "fast" mixing methods. Our results showed that in the case of the most hydrophobic polymers, the speed of mixing had no significant influence on the size and loading of the formed NPs. In contrast, in the case of less hydrophobic polymers, faster mixing led to smaller NPs with better encapsulation. The switch between mixing and polymer-controlled assembly was directly correlated to the solubility limit of the polymers in acetonitrile-water mixtures, with a critical point for solubility limits between 15 and 20 vol % of water. Our results provide simple guidelines on how to evaluate the possible influence of polymer chemistry and mixing on the formation of loaded NPs, opening the way to fine-tune their properties and optimize their large-scale production.

Trojan pH-Sensitive Polymer Particles Produced in a Continuous-Flow Capillary Microfluidic Device Using Water-in-Oil-in-Water Double-Emulsion Droplets.

A facile and robust microfluidic method to produce nanoparticle-in-microparticle systems (Trojan systems) is reported as a delivery vector for the oral administration of active pharmaceutical ingredients. The microfluidic system is based on two coaxial capillaries that produce monodisperse water-in-oil-in-water (W/O/W) double emulsions in a highly controlled fashion with precise control over the resulting particle structure, including the core and shell dimensions. The influence of the three phase flow rates, pH and drying process on the formation and overall size is evaluated. These droplets are then used as templates for the production of pH-sensitive Trojan microparticles after solvent evaporation. The shell of Trojan microparticles is made of Eudragit®, a methacrylic acid-ethyl acrylate copolymer that would enable the Trojan microparticle payload to first pass through the stomach without being degraded and then dissolve in the intestinal fluid, releasing the inner payload. The synthesis of the pH-sensitive Trojan microparticles was also compared with a conventional batch production method. The payloads considered in this work were different in nature: (1) fluorescein, to validate the feasibility of the polymeric shell to protect the payload under gastric pH; (2) poly(D,L-lactic acid/glycolic acid)-PLGA nanoparticles loaded with the antibiotic rifampicin. These PLGA nanoparticles were produced also using a microfluidic continuous process and (3) PLGA nanoparticles loaded with Au nanoparticles to trace the PLGA formulation under different environments (gastric and intestinal), and to assess whether active pharmaceutical ingredient (API) encapsulation in PLGA is due efficiently. We further showed that Trojan microparticles released the embedded PLGA nanoparticles in contact with suitable media, as confirmed by electron microscopy. Finally, the results show the possibility of developing Trojan microparticles in a continuous manner with the ability to deliver therapeutic nanoparticles in the gastrointestinal tract.

Assembly of Fluorescent Polymer Nanoparticles Using Different Microfluidic Mixers.

Nanoprecipitation is a facile and efficient approach to the assembly of loaded polymer nanoparticles (NPs) for applications in bioimaging and targeted drug delivery. Their successful use in clinics requires reproducible and scalable synthesis, for which microfluidics appears as an attractive technique. However, in the case of nanoprecipitation, particle formation depends strongly on mixing. Here, we compare 5 different types of microfluidic mixers with respect to the formation and properties of poly(d-l-lactide-co-glycolide) (PLGA) and poly(methyl methacrylate) NPs loaded with a fluorescent dye salt: a cross-shaped mixer, a multilamination mixer, a split and recombine mixer, two herringbone mixers, and two impact jet mixers. Size and fluorescence properties of the NPs obtained with these mixers are evaluated. All mixers, except the cross-shaped one, yield NPs at least as small and fluorescent as those obtained manually. Notably in the case of impact jet mixers operated at high flow speeds, the size of the NPs could be strongly reduced from >50 nm down to <20 nm. Surprisingly, the fluorescence quantum yield of NPs obtained with these mixers also depends strongly on the flow speed, increasing, in the case of PLGA, from 30 to >70%. These results show the importance of precisely controlling the assembly conditions for loaded polymer NPs. The present work further provides guidance for choosing the optimal microfluidic setup for production of nanomaterials for biomedical applications.

Production of Janus/Hecate microfibers by microfluidic photopolymerization and evaluation of their potential in dye removal.

The microfluidic production of Janus/Hecate polymer microfibers with well-defined interfaces from miscible phases is reported. The process offers tunability of the width and composition of each part of the fibers by controlling the flow rate and nature of the monomers in a single step. The enhanced performances of the fibers are outlined for the simultaneous removal of dyes of opposite charges using amphoteric Janus fibers.

Microfluidic encapsulation for controlled release and its potential for nanofertilisers.

Nanotechnology is increasingly being utilized to create advanced materials with improved or new functional attributes. Converting fertilizers into a nanoparticle-form has been shown to improve their efficacy but the current procedures used to fabricate nanofertilisers often have poor reproducibility and flexibility. Microfluidic systems, on the other hand, have advantages over traditional nanoparticle fabrication methods in terms of energy and materials consumption, versatility, and controllability. The increased controllability can result in the formation of nanoparticles with precise and complex morphologies (e.g., tuneable sizes, low polydispersity, and multi-core structures). As a result, their functional performance can be tailored to specific applications. This paper reviews the principles, formation, and applications of nano-enabled delivery systems fabricated using microfluidic approaches for the encapsulation, protection, and release of fertilizers. Controlled release can be achieved using two main routes: (i) nutrients adsorbed on nanosupports and (ii) nutrients encapsulated inside nanostructures. We aim to highlight the opportunities for preparing a new generation of highly versatile nanofertilisers using microfluidic systems. We will explore several main characteristics of microfluidically prepared nanofertilisers, including droplet formation, shell fine-tuning, adsorbate fine-tuning, and sustained/triggered release behavior.

Experimental Validation of a Novel Generator of Gas Mixtures Based on Axial Gas Pulses Coupled to a Micromixer.

In this work, a novel generator of gas mixtures previously numerically investigated and based on axial gas pulses coupled to a micromixer has been conceived, manufactured, and validated. Standard gaseous pollutant mixtures and pure nitrogen or pure air were introduced in a microdevice designed to generate alternating axial gas pulses which were downstream homogenized by means of a multi-stage modular micromixer. The dilution, and therefore the final pollutant concentration, was controlled by two parameters: the ratio between the times of each of the two gas pulses and the partial pressure of the pollutant(s) mixture added to the device. The gas mixture generator was coupled to an analyzer to monitor the concentration of aromatic pollutants. The response time was optimized to be lower than 2 min in accordance with the analytical instrument. The quantity of pollutants measured at the micromixer's outlet increased linearly with the expected gas concentration of 3.7-100 ppb generated by this novel microfluidic generator and fitted perfectly with those obtained by a reference gas dilution bench. At 5 ppb, the precision on the concentration generated is close to that obtained with the conventional gas mixing bench, i.e., around 10%.

Organic molecule confinement reaction for preparation of the Sn nanoparticles@graphene anode materials in Lithium-ion battery.

Sn@Graphene composites as anode materials in Lithium-ion batteries have attracted intensive interest due to the inherent high capacity. On the other side, the high atomic ratio (Li4.4Sn) induces the pulverization of the electrode with cycling. Thus, suppressing pulverization by designing the structure of the materials is an essential key for improving cyclability. Applying the nanotechnologies such as electrospinning, soft/hard nano template strategy, surface modification, multi-step chemical vapor deposition (CVD), and so on has demonstrated the huge advantage on this aspect. These strategies are generally used for homogeneous dispersing Sn nanomaterials in graphene matrix or constructing the voids in the inner of the materials to obtain the mechanical buffer effect. Unfortunately, these processes induce huge energy consumption and complicated operation. To solve the issue, new nanotechnology for the composites by the bottom-up strategy (Organic Molecule Confinement Reaction (OMCR)) was shown in this report. A 3D organic nanoframes was synthesized as a graphene precursor by low energy nano emulsification and photopolymerization. SnO2 nanoparticles@3D organic nanoframes as the composites precursor were in-situ formed in the hydrothermal reaction. After the redox process by the calcination, the Sn nanoparticles with nanovoids (~100 nm, uniform size) were homogeneously dispersed in a Two-Dimensional Laminar Matrix of graphene nanosheets (2DLMG) by the in-situ patterning and confinement effect from the 3D organic nanoframes. The pulverization and crack of the composites were effectively suppressed, which was proved by the electrochemical testing. The Sn nanoparticles@2DLMG not delivered just the high cyclability during 200 cycles, but also firstly achieved a high specific capacity (539 mAh g-1) at the low loading Sn (19.58 wt%).

Immobilization of ß-Galactosidase by Encapsulation of Enzyme-Conjugated Polymer Nanoparticles Inside Hydrogel Microparticles.

Increasing the shelf life of enzymes and making them reusable is a prominent topic in biotechnology. The encapsulation inside hydrogel microparticles (HMPs) can enhance the enzyme's stability by preserving its native conformation and facilitating continuous biocatalytic processes and enzyme recovery. In this study, we present a method to immobilize ß-galactosidase by, first, conjugating the enzyme onto the surface of polymer nanoparticles, and then encapsulating these enzyme-conjugated nanoparticles (ENPs) inside HMPs using microfluidic device paired with UV-LEDs. Polymer nanoparticles act as anchors for enzyme molecules, potentially preventing their leaching through the hydrogel network especially during swelling. The affinity binding (through streptavidin-biotin interaction) was used as an immobilization technique of ß-galactosidase on the surface of polymer nanoparticles. The hydrogel microparticles of roughly 400 µm in size (swollen state) containing unbound enzyme and ENPs were produced. The effects of encapsulation and storage in different conditions were evaluated. It was discovered that the encapsulation in acrylamide (AcAm) microparticles caused an almost complete loss of enzymatic activity. Encapsulation in poly(ethylene glycol) (PEG)-diacrylate microparticles, on the other hand, showed a residual activity of 15-25%, presumably due to a protective effect of PEG during polymerization. One of the major factors that affected the enzyme activity was presence of photoinitiator exposed to UV-irradiation. Storage studies were carried out at room temperature, in the fridge and in the freezer throughout 1, 7 and 28 days. The polymer nanoparticles showcased excellent immobilization properties and preserved the activity of the conjugated enzyme at room temperature (115% residual activity after 28 days), while a slight decrease was observed for the unbound enzyme (94% after 28 days). Similar trends were observed for encapsulated ENPs and unbound enzyme. Nevertheless, storage at -26°C resulted in an almost complete loss of enzymatic activity for all samples.

Continuous-Flow Production of Perfluorocarbon-Loaded Polymeric Nanoparticles: From the Bench to Clinic.

Perfluorocarbon-loaded nanoparticles are powerful theranostic agents, which are used in the therapy of cancer and stroke and as imaging agents for ultrasound and 19F magnetic resonance imaging (MRI). Scaling up the production of perfluorocarbon-loaded nanoparticles is essential for clinical translation. However, it represents a major challenge as perfluorocarbons are hydrophobic and lipophobic. We developed a method for continuous-flow production of perfluorocarbon-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles using a modular microfluidic system, with sufficient yields for clinical use. We combined two slit interdigital micromixers with a sonication flow cell to achieve efficient mixing of three phases: liquid perfluorocarbon, PLGA in organic solvent, and aqueous surfactant solution. The production rate was at least 30 times higher than with the conventional formulation. The characteristics of nanoparticles can be adjusted by changing the flow rates and type of solvent, resulting in a high PFC loading of 20-60 wt % and radii below 200 nm. The nanoparticles are nontoxic, suitable for 19F MRI and ultrasound imaging, and can dissolve oxygen. In vivo 19F MRI with perfluoro-15-crown-5 ether-loaded nanoparticles showed similar biodistribution as nanoparticles made with the conventional method and a fast clearance from the organs. Overall, we developed a continuous, modular method for scaled-up production of perfluorocarbon-loaded nanoparticles that can be potentially adapted for the production of other multiphase systems. Thus, it will facilitate the clinical translation of theranostic agents in the future.

Production of lipophilic nanogels by spontaneous emulsification.

Nanosized gel particles, so-called nanogels, have attracted substantial interest in different application fields, thanks to their controllable and three-dimensional physical structure, good mechanical properties and potential biocompatibility. Literature reports many technologies for their preparation and design, however a recurrent limitation remains in their broad size distributions as well as in the poor size control. Therefore, the monodisperse and size-controlled nanogels preparation by simple process -like emulsification- is a real challenge still in abeyance to date. In this study we propose an original low energy emulsification approach for the production of monodisperse nanogels, for which the size can be finely controlled in the range 30 to 200 nm. The principle lies in the fabrication of a direct nano-emulsion containing both oil (medium chain triglycerides) and a bi-functional acrylate monomer. The nanogels are thus formed in situ upon UV irradiation of the droplet suspension. Advantage of such modification of the oil nano-carriers are the potential modulation of the release of encapsulated drugs, as a function of the density and/or properties of the polymer chain network entrapped in the oil nano-droplets. This hypothesis was confirmed using a model of hydrophobic drug -ketoprofen- entrapped into the nanogels particles, along with the study of the release profile, carried out in function of the nature of the monomers, density of polymer chains, and different formulation parameters.

Synthesis and functionalization of hyperbranched polymers for targeted drug delivery.

Hyperbranched polymers (HBPs) have found use in a wide range of applications, such as optical, electronic and magnetic materials, coatings, additives, supramolecular chemistry, and biomedicine. HBPs have gained attention for the development of drug delivery systems due to the presence of internal cavities in their three-dimensional globular structure that can be used to encapsulate drugs and their facile synthesis as compared to dendrimers. The composition, topology, and functionality of HBPs have been tuned to design drug carriers with better efficacies. Recent advances have been reported to introduce functional groups to enhance targeting tumor cells. HBPs have been modified to promote passive and active targeting. This review article will describe the different routes to synthesize hyperbranched polymer, their use as drug carriers for targeted drug delivery, and their functionalization with ligands for active targeting through various synthesis strategies to give the reader an extended overview of the progresses accomplished in this field. The modification of HBPs with ligands such as peptides, oligonucleotides, and folic acid have been demonstrated to enhance the accumulation of the drug selectively at the tumor sites. The potential uses and developments of HBPs as nanoobjects for theranostics for example are discussed as perspectives.

Preparation and Deep Characterization of Composite/Hybrid Multi-Scale and Multi-Domain Polymeric Microparticles.

Polymeric microparticles were produced following a three-step procedure involving (i) the production of an aqueous nanoemulsion of tri and monofunctional acrylate-based monomers droplets by an elongational-flow microemulsifier, (ii) the production of a nanosuspension upon the continuous-flow UV-initiated miniemulsion polymerization of the above nanoemulsion and (iii) the production of core-shell polymeric microparticles by means of a microfluidic capillaries-based double droplets generator; the core phase was composed of the above nanosuspension admixed with a water-soluble monomer and gold salt, the shell phase comprised a trifunctional monomer, diethylene glycol and a silver salt; both phases were photopolymerized on-the-fly upon droplet formation. Resulting microparticles were extensively analyzed by energy dispersive X-rays spectrometry and scanning electron microscopy to reveal the core-shell morphology, the presence of silver nanoparticles in the shell, organic nanoparticles in the core but failed to reveal the presence of the gold nanoparticles in the core presumably due to their too small size (c.a. 2.5 nm). Nevertheless, the reddish appearance of the as such prepared polymer microparticles emphasized that this three-step procedure allowed the easy elaboration of composite/hybrid multi-scale and multi-domain polymeric microparticles.

Supported Catalytically Active Supramolecular Hydrogels for Continuous Flow Chemistry.

Inspired by biology, one current goal in supramolecular chemistry is to control the emergence of new functionalities arising from the self-assembly of molecules. In particular, some peptides can self-assemble and generate exceptionally catalytically active fibrous networks able to underpin hydrogels. Unfortunately, the mechanical fragility of these materials is incompatible with process developments, relaying this exciting field to academic curiosity. Here, we show that this drawback can be circumvented by enzyme-assisted self-assembly of peptides initiated at the walls of a supporting porous material. We applied this strategy to grow an esterase-like catalytically active supramolecular hydrogel (CASH) in an open-cell polymer foam, filling the whole interior space. Our supported CASH material is highly efficient towards inactivated esters and enables the kinetic resolution of racemates. This hybrid material is robust enough to be used in continuous flow reactors, and is reusable and stable over months.

Design of a Novel Axial Gas Pulses Micromixer and Simulations of its Mixing Abilities via Computational Fluid Dynamics.

Following the fast development of microfluidics over the last decade, the need for methods for mixing two gases in flow at an overall flow rate ranging from 1 to 100 NmL·min-1 with programmable mixing ratios has been quickly increasing in many fields of application, especially in the calibration of analytical devices such as air pollution sensors. This work investigates numerically the mixing of pure gas pulses at flow rates in the range 1⁻100 NmL·min-1 in a newly designed multi-stage and modular micromixer composed of 4 buffer tanks of 300 µL each per stage. Results indicate that, for a 1 s pulse of pure gas (formaldehyde) followed by a 9 s pulse of pure carrier gas (air), that is a pulses ratio of 1/10, an effective mixing up to 94⁻96% can be readily obtained at the exit of the micromixer. This is achieved in less than 20 s for any flow rate ranging from 1 to 100 NmL·min-1 simply by adjusting the number of stages, 1 to 16 respectively. By using an already diluted gas bottle containing 100 ppm of a given compound in an inert gas same as the carrier gas, concentrations ranging from 10 to 90 ppm should be obtained by adjusting the pulses ratio between 1/10 and 9/10 respectively.

Magnetite- and Iodine-Containing Nanoemulsion as a Dual Modal Contrast Agent for X-ray/Magnetic Resonance Imaging.

Noninvasive diagnostic by imaging combined with a contrast agent (CA) is by now the most used technique to get insight into human bodies. X-ray and magnetic resonance imaging (MRI) are widely used technologies providing complementary results. Nowadays, it seems clear that bimodal CAs could be an emerging approach to increase the patient compliance, accessing different imaging modalities with a single CA injection. Owing to versatile designs, targeting properties, and high payload capacity, nanocarriers are considered as a viable solution to reach this goal. In this study, we investigated efficient superparamagnetic iron oxide nanoparticle (SPION)-loaded iodinated nano-emulsions (NEs) as dual modal injectable CAs for X-ray imaging and MRI. The strength of this new CA lies not only in its dual modal contrasting properties and biocompatibility, but also in the simplicity of the nanoparticulate assembling: iodinated oily core was synthesized by the triiodo-benzene group grafting on vitamin E (41.7% of iodine) via esterification, and SPIONs were produced by thermal decomposition during 2, 4, and 6 h to generate SPIONs with different morphologies and magnetic properties. SPIONs with most anisotropic shape and characterized by the highest r2/ r1 ratio once encapsulated into iodinated NE were used for animal experimentation. The in vivo investigation showed an excellent contrast modification because of the presence of the selected NEs, for both imaging techniques explored, that is, MRI and X-ray imaging. This work provides the description and in vivo application of a simple and efficient nanoparticulate system capable of enhancing contrast for both preclinical imaging modalities, MRI, and computed tomography.

Double emulsions prepared by two-step emulsification: History, state-of-the-art and perspective.

Attractive interest on double emulsions comes from their unique morphology, making them general multifunctional carriers able to encapsulate different hydrophilic and lipophilic molecules in the same particle. Over the past century, two different types of methods were followed to prepare double emulsions for pharmaceutics applications, so-called "one-step" and "two-step" processes. The two-step approach, consisting in two different emulsifications successively performed, allows the optimal and more efficient formulations due to simplicity of principle and controllability of the process. In this review, focused on the formulation of double emulsions by two-step process, we recount the historical development of this approach, along with the state-of-the-art, including a discussion on the role of the formulation parameters, surfactants, amphiphilic polymers, interface stabilization, volume fraction, and so forth, on the final formulation stability, morphology and properties as drug delivery system. Discussion was also extended to polymeric microparticles and nanoparticles made by solvent diffusion, on the basis of double emulsions made by two-step process, along with literature review on the impact of different formulation and processing parameters. In addition, the properties of the polymers used in the microparticles matrix (molecular weight, chemical nature) potentially impacting on the ones of the microparticles formed (drug release kinetics, stability, morphology), were also discussed. Finally, the future trends in double emulsions application were addressed, emphasizing some new advances made in the emulsifications method as potentially able to open the range of applications, for example to nanoscale with spontaneous emulsification or low energy microfluidic emulsification.

Production of dry-state ketoprofen-encapsulated PMMA NPs by coupling micromixer-assisted nanoprecipitation and spray drying.

We present a two-step process to produce dry-state Ketoprofen-loaded poly(methyl methacrylate) nanoparticles (NPs) with controllable size and tunable drug release profile. A colloidal suspension of drug-loaded nanoparticles was first obtained from a nanoprecipitation process and then transferred into a commercial spray dryer. Three micromixers of different designs and mixing principles (molecular diffusion and impact mixing) were tested. After the first step, highly monomodal NPs in the size range 100 to 210 nm were obtained as seen by the low polydispersity index value (ca. PDI ∼ 0.2) returned by a dynamic light scattering detector. Physicochemical properties, encapsulation efficiency/ratio and drug release kinetics of NPs before and after drying were determined. For similar operating conditions, the best micromixer tested (impact mixing) allowed concluding that the NPs size was not significantly affected by the spray drying while encapsulation parameters and drug release rate were slightly decreased compared to the non spray-dried NPs. A sustained drug release was observed over 6 h and the drug release rate (up to 70%) was found to vary with the size of the NPs which in turn was a function of the flow rate ratio between the polymer solution and the non-solvent solution.

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators.

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

Microfluidic-Assisted Production of Size-Controlled Superparamagnetic Iron Oxide Nanoparticles-Loaded Poly(methyl methacrylate) Nanohybrids.

In this paper, superparamagnetic iron oxide nanoparticles (SPIONs, around 6 nm) encapsulated in poly(methyl methacrylate) nanoparticles (PMMA NPs) with controlled sizes ranging from 100 to 200 nm have been successfully produced. The hybrid polymeric NPs were prepared following two different methods: (1) nanoprecipitation and (2) nanoemulsification-evaporation. These two methods were implemented in two different microprocesses based on the use of an impact jet micromixer and an elongational-flow microemulsifier. SPIONs-loaded PMMA NPs synthesized by the two methods presented completely different physicochemical properties. The polymeric NPs prepared with the micromixer-assisted nanoprecipitation method showed a heterogeneous dispersion of SPIONs inside the polymer matrix, an encapsulation efficiency close to 100 wt %, and an irregular shape. In contrast, the polymeric NPs prepared with the microfluidic-assisted nanoemulsification-evaporation method showed a homogeneous dispersion, an almost complete encapsulation, and a spherical shape. The properties of the polymeric NPs have been characterized by dynamic light scattering, thermogravimetric analysis, and transmission electron microscope. In vitro cytotoxicity assays were also performed on the nanohybrids and pure PMMA NPs.

A new formulation of poly(MAOTIB) nanoparticles as an efficient contrast agent for in vivo X-ray imaging.

Polymeric nanoparticles (PNPs) are gaining increasing importance as nanocarriers or contrasting material for preclinical diagnosis by micro-CT scanner. Here, we investigated a straightforward approach to produce a biocompatible, radiopaque, and stable polymer-based nanoparticle contrast agent, which was evaluated on mice. To this end, we used a nanoprecipitation dropping technique to obtain PEGylated PNPs from a preformed iodinated homopolymer, poly(MAOTIB), synthesized by radical polymerization of 2-methacryloyloxyethyl(2,3,5-triiodobenzoate) monomer (MAOTIB). The process developed allows an accurate control of the nanoparticle properties (mean size can range from 140 nm to 200 nm, tuned according to the formulation parameters) along with unprecedented important X-ray attenuation properties (concentration of iodine around 59 mg I/mL) compatible with a follow-up in vivo study. Routine characterizations such as FTIR, DSC, GPC, TGA, 1H and 13C NMR, and finally SEM were accomplished to obtain the main properties of the optimal contrast agent. Owing to excellent colloidal stability against physiological conditions evaluated in the presence of fetal bovine serum, the selected PNPs suspension was administered to mice. Monitoring and quantification by micro-CT showed that iodinated PNPs are endowed strong X-ray attenuation capacity toward blood pool and underwent a rapid and passive accumulation in the liver and spleen. STATEMENT OF SIGNIFICANCE: The design of X-ray contrast agents for preclinical imaging is still highly challenging. To date, the best contrast agents reported are based on iodinated lipids or inorganic materials such as gold. In literature, several attempts were undertaken to create polymer-based X-ray contrast agents, but their applicability in vivo was limited to their low contrasting properties. Polymer-based contrast agents present the advantages of an easy surface modification for future application in targeting. Herein, we develop a novel approach to design polymer-based nanoparticle X-ray contrast agent (polymerization of a highly iodine-loaded monomer (MAOTIB)), leading to an iodine concentration of 59 mg/mL. We showed their high efficiency in vivo in mice, in terms of providing a strong signal in blood and then accumulating in the liver and spleen.