In Situ Monitoring of Block Copolymer Self-Assembly via Solvent Exchange through Controlled Dialysis with Light and Neutron Scattering Detection.

Solution self-assembly of amphiphilic block copolymers (BCs) is typically performed by a solvent-to-water exchange. However, BC assemblies are often trapped in metastable states depending on the mixing conditions such as the magnitude and rate of water addition. BC self-assembly can be performed under near thermodynamic control by dialysis, which accounts for a slow and gradual water addition. In this Letter we report the use of a specifically designed dialysis cell to continuously monitor by dynamic light scattering and small-angle neutron scattering the morphological changes of PDMS-b-PEG BCs self-assemblies during THF-to-water exchange. The complete phase diagrams of near-equilibrium structures can then be established. Spherical micelles first form before evolving to rod-like micelles and vesicles, decreasing the total developed interfacial area of self-assembled structures in response to increasing interfacial energy as the water content increases. The dialysis kinetics can be tailored to the time scale of BC self-assembly by modifying the membrane pore size, which is of interest to study the interplay between thermodynamics and kinetics in self-assembly pathways.

Solution behavior and encapsulation properties of fatty acid-elastin-like polypeptide conjugates.

Developing new biomaterials is an active research area owing to their applications in regenerative medicine, tissue engineering and drug delivery. Elastin-like polypeptides (ELPs) are good candidates for these applications because they are biosourced, biocompatible and biodegradable. With the aim of developing ELP-based micelles for drug delivery applications we have synthesized 15 acyl-ELP compounds by conjugating myristic, palmitic, stearic, oleic or linoleic acid to the N-terminus of three ELPs differing in molar mass. The ELP-fatty acid conjugates have interesting solution behavior. They form micelles at low temperatures and aggregate above the cloud point temperature (Tcp). The critical micelle concentration depends on the fatty acid nature while the micelle size is mainly determined by the ELP block length. We were able to show that ELPs were better hydrated in the micelles than in their individual state in solution. The micelles are stable in phosphate-buffered saline at temperatures below the Tcp, which can vary between 20 °C and 38 °C depending on the length or hydrophilicity of the ELP. Acyl-ELP micelles were loaded with the small hydrophobic molecule Nile red. The encapsulation efficiency and release kinetics showed that the best loading conditions were achieved with the largest ELP conjugated to stearic acid.

Dual Photoredox Ni/Benzophenone Catalysis: A Study of the NiII Precatalyst Photoreduction Step.

The combination of NiIIX2 salts with a bipyridine-type ligand and aromatic carbonyl-based chromophores has emerged as a benchmark precatalytic system to efficiently conduct cross-couplings mediated by light. Mechanistic studies have led to two scenarios in which Ni0 is proposed as the catalytic species. Nonetheless, in none of these studies has a NiII to Ni0 photoreduction been evidenced. By exploiting UV-visible, nuclear magnetic resonance, resonance Raman, electron paramagnetic resonance, and dynamic light scattering spectroscopies and also transmission electron microscopy, we report that, when photolyzed by UVA in alcohols, the structurally defined [NiII2(µ-OH2)(dtbbpy)2(BPCO2)4] complex 1 integrating a benzophenone chromophore is reduced into a diamagnetic NiI dimer of the general formula [NiI2(dtbbpy)2(BPCO2)2]. In marked contrast, in THF, photolysis led to the fast formation of Ni0, which accumulates in the form of metallic ultrathin Ni nanosheets characterized by a mean size of ∼100 nm and a surface plasmon resonance at 505 nm. Finally, it is shown that 1 combined with UVA irradiation catalyzes cross-couplings, that is, C(sp3)-H arylation of THF and O-arylation of methanol. These results are discussed in light of the mechanisms proposed for these cross-couplings with a focus on the oxidation state of the catalytic species.

Complexation in Aqueous Solution of a Hydrophobic Polyanion (PSSNa) Bearing Different Charge Densities with a Hydrophilic Polycation (PDADMAC).

In this work the electrostatic complexation of two strong polyelectrolytes (PEs) was studied, the hydrophilic and positively charged poly (diallyldimethylammonium chloride) (PDADMAC) and the hydrophobic and negatively charged poly (styrene-co-sodium styrene sulfonate) (P(St-co-SSNa)), which was prepared at different sulfonation rates. The latter is known to adopt a pearl necklace conformation in solution for intermediate sulfonation rates, suggesting that a fraction of the P(St-co-SSNa) charges might be trapped in these hydrophobic domains; thus making them unavailable for complexation. The set of complementary techniques (DLS, zetametry, ITC, binding experiment with a cationic and metachromatic dye) used in this work highlighted that this was not the case and that all anionic charges of P(St-co-SSNa) were in fact available for complexation either with the polycationic PDADMAC or the monocationic o-toluidine blue dye. Only minor differences were observed between these techniques, consistently showing a complexation stoichiometry close to 1:1 at the charge equivalence for the different P(St-co-SSNa) compositions. A key result emphasizing that (i) the strength of the electrostatic interaction overcomes the hydrophobic effect responsible for pearl formation, and (ii) the efficiency of complexation does not depend significantly on differences in charge density between PDADMAC and P(St-co-SSNa), highlighting that PE chains can undergo conformational rearrangements favoring the juxtaposition of segments of opposite charge. Finally, these data have shown that the formation of colloidal PECs, such as PDADMAC and P(St-co-SSNa), occurs in two distinct steps with the formation of small primary complex particles (<50 nm) by pairing of opposite charges (exothermic step) followed by their aggregation within finite-size clusters (endothermic step). This observation is in agreement with the previously described mechanism of PEC particle formation from strongly interacting systems containing a hydrophobic PE.

Tuning the activity and selectivity of polymerised ionic liquid-stabilised ruthenium nanoparticles through anion exchange reactions.

The development of highly active and selective heterogeneous-based catalysts with tailorable properties is not only a fundamental challenge, but is also crucial in the context of energy savings and sustainable chemistry. Here, we show that ruthenium nanoparticles (RuNPs) stabilised with simple polymerised ionic liquids (PILs) based on N-vinyl imidazolium led to highly active and robust nano-catalysts in hydrogenation reactions, both in water and organic media. Of particular interest, their activity and selectivity could simply be manipulated through counter-anion exchange reactions. Hence, as a proof of concept, the activity of RuNPs could be reversibly turned on and off in the hydrogenation of toluene, while in the case of styrene, the hydrogenation could be selectively switched from ethylbenzene to ethylcyclohexane upon anion metathesis. According to X-ray photoelectron spectroscopy (XPS) and dynamic light scattering (DLS) analyses, these effects could originate not only from the relative hydrophobicity and solvation of the PIL corona but also from the nature and strength of the PIL-Ru interactions.

Carbohydr Polym Special Issue Invited contribution: Click chemistry for block polysaccharides with dihydrazide and dioxyamine linkers - A review.

Engineered block polysaccharides is a relatively new class of biomacromolecules consisting of chemical assembly of separate block structures at the chain termini. In contrast to conventional, laterally substituted polysaccharide derivatives, the block arrangement allows for much higher preservation of inherent chain properties such as biodegradability and stimuli-responsive self-assembly, while at the same time inducing new macromolecular properties. Abundant, carbon neutral, and even recalcitrant biomass is an excellent source of blocks, opening for numerous new uses of biomass for a wide range of novel biomaterials. Among a limited range of methodologies available for block conjugation, bifunctional linkers allowing for oxyamine and hydrazide 'click' reactions have recently proven useful additions to the repertoire. This article focuses the chemistry and kinetics of these reactions. It also presents some new data with the aim to provide useful protocols and methods for general use towards new block polysaccharides.

Interfacial Behavior of Solid- and Liquid-like Polyelectrolyte Complexes as a Function of Charge Stoichiometry.

We systematically investigate in this work the surface activity of polyelectrolyte complex (PECs) suspensions as a function of the molar charge ratio Z (= [-]/[+]) from two model systems: the weakly and strongly interacting poly (diallyldimethylammonium chloride)/poly (acrylic acid sodium salt) (PDADMAC/PANa) and poly (diallyldimethylammonium chloride)/poly (sodium 4- styrenesulfonate) (PDADMAC/PSSNa) pairs, respectively. For both systems, the PEC surface tension decreases as the system approaches charge stoichiometry (Z = 1) whenever the complexation occurs in the presence of excess PDADMAC (Z < 1) or excess polyanion (Z > 1) consistent with an increased level of charge neutralization of PEs forming increasingly hydrophobic and neutral surface-active species. The behavior at stoichiometry (Z = 1) is also particularly informative about the physical nature of the complexes. The PDADMAC/PANa system undergoes a liquid-liquid phase transition through the formation of coacervate microdroplets in equilibrium with macroions remaining in solution. In the PDADMAC/PSSNa system, the surface tension of the supernatant was close to that of pure water, suggesting that the PSSNa-based complexes have completely sedimented, consistent with a complete liquid-solid phase separation of an out-of-equilibrium system. Besides, the high sensitivity of surface tension measurements, which can detect the presence of trace amounts of aggregates and other precursors in the supernatant, allows for very accurate determination of the exact charge stoichiometry of the complexes. Finally, the very low water/water interfacial tension that develops between the dilute phase and the denser coacervate phase in the PDADAMAC/PANa system was measured using the generalized Young-Laplace method to complete the full characterization of both systems. The overall study showed that simple surface tension measurements can be a very sensitive tool to characterize, discriminate, and better understand the formation mechanism of the different structures encountered during the formation of PECs.

Functionalisation of the non-reducing end of chitin by selective periodate oxidation: A new approach to form complex block polysaccharides and water-soluble chitin-based block polymers.

Most polysaccharides used in polysaccharide-based block copolymers are attached to the second block through the reducing end, due to the few and highly polysaccharide specific non-reducing end (NRE) functionalisation methods available. Chitin oligomers, prepared by nitrous acid degradation of chitosan (AnM) can, however, be selectively oxidised by periodate since they only possess a single vicinal diol in the NRE residue. Here, we show that both aldehydes formed after oxidation are highly reactive towards bifunctional oxyamines and hydrazide linkers. Sub-stochiometric amounts of linkers resulted in conjugation of AnM oligomers through both chain termini to yield a discrete distribution of 'polymerised' oligomers. Such chitin-based block polymers were, in contrast to chitins of the same chain lengths, water-soluble. Oxidised AnM oligomers, functionalised at both termini can also enable the preparation of more complex block polysaccharides such as ABA- or ABC-type.

Fundamental and Practical Aspects in the Formulation of Colloidal Polyelectrolyte Complexes of Chitosan and siRNA.

The formation of electrostatic interactions between polyanionic siRNA and polycations gives an easy access to the formation of colloidal particles capable of delivering siRNA in vitro or in vivo. Among the polycations used for siRNA delivery, chitosan occupies a special place due to its unique physicochemical and biological properties. In this chapter we describe the fundamental and practical aspects of the formation of colloidal complexes between chitosan and siRNA. The basis of the electrostatic complexation between oppositely charged polyelectrolytes is first introduced with a focus on the specific conditions to obtain stable colloid complex particles. Subsequent, the properties that make chitosan so special are described. In a third part, the main parameters influencing the colloidal properties and stability of siRNA/chitosan complexes are reviewed with emphasis on some practical aspects to consider in the preparation of complexes.

2,5-Anhydro-d-Mannose End-Functionalized Chitin Oligomers Activated by Dioxyamines or Dihydrazides as Precursors of Diblock Oligosaccharides.

Diblock oligosaccharides based on renewable resources allow for a range of new but, so far, little explored biomaterials. Coupling of blocks through their reducing ends ensures retention of many of their intrinsic properties that otherwise are perturbed in classical lateral modifications. Chitin is an abundant, biodegradable, bioactive, and self-assembling polysaccharide. However, most coupling protocols relevant for chitin blocks have shortcomings. Here we exploit the highly reactive 2,5-anhydro-d-mannose residue at the reducing end of chitin oligomers obtained by nitrous acid depolymerization. Subsequent activation by dihydrazides or dioxyamines provides precursors for chitin-based diblock oligosaccharides. These reactions are much faster than for other carbohydrates, and only acyclic imines (hydrazones or oximes) are formed (no cyclic N-glycosides). α-Picoline borane and cyanoborohydride are effective reductants of imines, but in contrast to most other carbohydrates, they are not selective for the imines in the present case. This could be circumvented by a simple two-step procedure. Attachment of a second block to hydrazide- or aminooxy-functionalized chitin oligomers turned out to be even faster than the attachment of the first block. The study provides simple protocols for the preparation of chitin-b-chitin and chitin-b-dextran diblock oligosaccharides without involving protection/deprotection strategies.

Reducing-End Functionalization of 2,5-Anhydro-d-mannofuranose-Linked Chitooligosaccharides by Dioxyamine: Synthesis and Characterization.

The nitrous acid depolymerization of chitosan enables the synthesis of singular chitosan oligosaccharides (COS) since their reducing-end unit is composed of 2,5-anhydro-d-mannofuranose (amf). In the present study, we describe a chemical method for the reducing-end conjugation of COS-amf by the commercially available dioxyamine O,O'-1,3-propanediylbishydroxylamine in high mass yields. The chemical structure of resulting dioxyamine-linked COS-amf synthesized by both oximation and reductive amination ways were fully characterized by 1H- and 13C-NMR spectroscopies and MALDI-TOF mass spectrometry. The coupling of chemically attractive linkers such as dioxyamines at the reducing end of COS-amf forms a relevant strategy for the development of advanced functional COS-based conjugates.

Activation of enzymatically produced chitooligosaccharides by dioxyamines and dihydrazides.

Reducing end activation of poly- and oligosaccharides by bifunctional dioxyamines and dihydrazides enables aniline-free and cyanoborohydride-free conjugation to aldehyde-containing molecules, particles and surfaces without compromising the chain structure. Chitosans are due to their polycationic character, biodegradability, and bioactivity important candidates for conjugation. Here, we present a kinetic and structural study of the conjugation of a dioxyamine and a dihydrazide to enzymatically produced chitooligosaccharides ranging from N,N'-diacetylchitobiose to a decamer, all having N-acetyl d-glucosamine at the reducing end. Conjugation of the dioxyamine resulted in mixtures of (E)- and (Z)-oximes and ß-N-pyranoside, whereas the dihydrazide yielded cyclic N-glycosides. Reaction kinetics was essentially independent of DP. Stable secondary amines were in both cases obtained by reduction with α-picoline borane, but higher temperatures were needed to obtain acceptable reduction rate. Comparison to dextran oligomers shows that the nature of the reducing end strongly influences the kinetics of both the conjugation and reduction.

Embedding of superparamagnetic iron oxide nanoparticles into membranes of well-defined poly(ethylene oxide)-block-poly(ε-caprolactone) nanoscale magnetovesicles as ultrasensitive MRI probes of membrane bio-degradation.

The present study reports the preparation of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) polymer vesicles via a nanoprecipitation method and the loading of two different size hydrophobically coated ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (a magnetic core size of 4.2 nm and 7.6 nm) into the membrane of these nanovesicles, whose thickness was measured precisely by small angle neutron scattering (SANS). Spherical nano-assemblies with a high USPIO payload and a diameter close to 150 nm were obtained as confirmed by dynamic light scattering (DLS), transmission electron microscopy (TEM) and cryo-TEM. The vesicular structure of these hybrid nano-assemblies was confirmed by multi-angle light scattering (MALS) measurements. Their magnetic properties were evaluated by T1 and T2 measurements (20 and 60 MHz) and by nuclear magnetic relaxation dispersion (NMRD) profiles. The size of USPIO entrapped in the membranes of PEO-b-PCL vesicles has a strong impact on their magnetic properties. It affects both their longitudinal and their transverse relaxivities and thus their magnetic resonance imaging (MRI) sensitivity. Acid-catalyzed hydrolysis of the PCL membrane also influences their relaxivities as shown by measurements carried out at pH 7 vs. pH 5. This property was used to monitor the membrane hydrolytic degradation in vitro, as a proof of concept of potential monitoring of drug delivery by nanomedicines in vivo and non-invasively, by MRI.

Effects of Chain Length of Chitosan Oligosaccharides on Solution Properties and Complexation with siRNA.

In the context of gene delivery, chitosan has been widely used as a safe and effective polycation to complex DNA, RNA and more recently, siRNA. However, much less attention has been paid to chitosan oligosaccharides (COS) despite their biological properties. This study proposed to carry out a physicochemical study of COS varying in degree of polymerization (DP) from 5 to 50, both from the point of view of the solution properties and the complexing behavior with siRNA. The main parameters studied as a function of DP were the apparent pKa, the solubility versus pH, the binding affinity with siRNA and the colloidal properties of complexes. Some parameters, like the pKa or the binding enthalpy with siRNA, showed a marked transition from DP 5 to DP 13, suggesting that electrostatic properties of COS vary considerably in this range of DP. The colloidal properties of siRNA/COS complexes were affected in a different way by the COS chain length. In particular, COS of relatively high DP (≥50) were required to form small complex particles with good stability.

Anti-tumor efficacy of hyaluronan-based nanoparticles for the co-delivery of drugs in lung cancer.

Combinations of therapeutic agents could synergistically enhance the response of lung cancer cells. Co-delivery systems capable of transporting chemotherapeutics with different physicochemical properties and with the simultaneous release of drugs remain elusive. Here, we assess the ability of nanoparticles of 30-nm diameter obtained from the self-assembly of hyaluronan-based copolymer targeting CD44 receptors to encapsulate both gefitinib and vorinostat for effective combinational lung cancer treatment. Drug loading was performed by nanoprecipitation. Drug release experiments showed a slow release of both drugs after 5 days. Using two- and three-dimensional lung adenocarcinoma cell cultures, we observed that the nanoparticles were mostly found at the periphery of the CD44-expressing spheroids. These drug-loaded nanoparticles were as cytotoxic as free drugs in the two- and three-dimensional systems and toxicity was due to apoptosis induction. In mouse models, intravenous injection of hyaluronan-based nanoparticles showed a selective delivery to subcutaneous CD44-overexpressing tumors, despite a significant liver capture. In addition, the systemic toxicity of the free drugs was reduced by their co-delivery using the nanoparticles. Finally, intrapulmonary administration of drug-loaded nanoparticles, to avoid a possible hepatic toxicity due to their accumulation in the liver, showed a stronger inhibition of orthotopic lung tumor growth compared to free drugs. In conclusion, hyaluronan-based nanoparticles provide active targeting partially mediated by CD44, less-toxic drug release and improved antitumor efficiency.

Impact of the Formulation Pathway on the Colloidal State and Crystallinity of Poly-ε-caprolactone Particles Prepared by Solvent Displacement.

The formulation pathway and/or the mixing method are known to be relevant in many out-of-equilibrium processes. In this work, we studied the effect of the mixing conditions on the physicochemical properties of poly-ε-caprolactone (PCL) particles prepared by solvent displacement. More specifically, water was added in one shot (fast addition) or drop by drop to PCL solution in tetrahydrofuran (THF) to study the impact of the mixing process on particle properties including size, stability, and crystallinity. Two distinct composition maps representing the Ouzo domain characteristic of the presence of metastable nanoparticles have been established for each mixing method. Polymer nanoparticles are formed in the Ouzo domain according to a nucleation and growth (or aggregation) mechanism. The fast addition promotes a larger nucleation rate, thus favoring the formation of small and uniform particles. For the drop-by-drop addition, for which the polymer solubility gradually decreases, the composition trajectories systematically cross an intermediate unstable region between the solubility limit of the polymer and the Ouzo domain. This leads to heterogeneous nucleation as shown by the formation of larger and less stable particles. Particles formed in the Ouzo domain have semi-crystalline properties. The PCL melting point is decreased with the THF fraction trapped in particles in accordance with Flory's theory for melt crystallization. On the other hand, the degree of crystallinity is constant, around 20% regardless of the THF fraction. No difference between fast and slow addition could be detected on the semi-crystalline properties of the particles which emphasize that thermodynamic rather than kinetic factors drive the polymer crystallization in particles. The recovery of bulk PCL crystallinity after the removal of THF from particles tends to confirm this hypothesis.

Impact of surface grafting density of PEG macromolecules on dually fluorescent silica nanoparticles used for the in vivo imaging of subcutaneous tumors.

BACKGROUND: In the context of systematically administered nanomedicines, the physicochemistry of NP surfaces must be controlled as a prerequisite to improve blood circulation time, and passive and active targeting. In particular, there is a real need to develop NP stealth and labelling for both in vivo and microscopic fluorescence imaging in a mice model. METHODS: We have synthesized NIR/red dually fluorescent silica nanoparticles of 19nm covalently covered by a PEG layer of different grafting density in the brush conformational regime by using a reductive amination reaction. These particles were characterized by TEM, DRIFT, DLS, TGA, ζ potential measurements, UV-vis and fluorescence spectroscopy. Prostate tumors were generated in mice by subcutaneous injection of RM1-CMV-Fluc cells. Tumor growth was monitored by BLI after a D-luciferin injection. Four samples of PEGylated fluorescent NPs were individually intravenously injected into 6 mice (N=6, total 24 mice). Nanoparticle distribution was investigated using in vivo fluorescence reflectance imaging (FRI) over 48h and microscopy imaging was employed to localize the NPs within tumors in vitro. RESULTS: Fluorescent NP accumulation, due to the enhanced permeability and retention (EPR) effect, increases gradually as a function of increased PEG surface grafting density with a huge difference observed for the highest density grafting. For the highest grafting density, a blood circulation time of up to 24h was observed with a strong reduction in uptake by the liver. In vivo experimental results suggest that the biodistribution of NPs is very sensitive to slight variations in surface grafting density when the NPs present a high curvature radius. CONCLUSION: This study underlines the need to compensate a high curvature radius with a PEG-saturated NP surface to improve blood circulation and accumulation within tumors through the EPR effect. Dually fluorescent NPs PEGylated to saturation display physical properties useful for assessing the susceptibility of tumors to the EPR effect. GENERAL SIGNIFICANCE: Control of the physicochemical features of nanoparticle surfaces to improve blood circulation times and monitoring of the EPR effect. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Structure, thermodynamic and kinetic signatures of a synthetic polyelectrolyte coacervating system.

While many studies on coacervation have targeted biomacromolecules, we review in this article the key structure, thermodynamic and kinetic features of a fully synthetic coacervating system based on polyacrylic acid (PAA) and poly(diallyldimethylammonium chloride) (PDADMAC) oppositely charged polyelectrolytes at pH10, where PAA chains are fully deprotonated. Among the main points of interest, we can highlight (i) the presence of polyelectrolyte complex (PEC) nanoparticles that, unexpectedly, coexist with a certain amount of coacervate droplets in a large range of compositions, even far from stoichiometry; (ii) the fact that these PEC nanoparticles are likely precursors of the coacervation occurring at stoichiometry; (iii) the formation of soluble PECs only in a certain range of physicochemical conditions; (iv) the equilibrium properties of the system; (v) and last but not least a distinctive kinetic signature at stoichiometry evidenced by a peak in light scattering at very short times (~100ms). Some of these results can be rationalized on the basis of weak interaction unfolding between oppositely charged PAA and PDADMAC chains as revealed by microcalorimetry measurements.

Early stage kinetics of polyelectrolyte complex coacervation monitored through stopped-flow light scattering.

Polyelectrolyte complexes (PECs) between poly(acrylic acid) (PAA) and poly(diallyldimethylammonium chloride) (PDADMAC), a model system forming coacervate particles via electrostatic interaction at pH 10, were prepared by a stopped-flow (SF) fast mixing technique at different mixing charge ratios (z) and ionic strengths. Both PEC final morphologies prepared by either SF or manual one-shot mixing are similar at bench time. In situ light scattering combined with the SF technique pointed-out, however, the presence of three distinct early stage kinetic behaviors in the formation of PECs. The first stage observed at low z is ascribed to the relaxation/reorganization of soluble PECs. At higher z or in the presence of salt, a second stage is found corresponding to the aggregation and/or rearrangement of small soluble PECs into larger structures. Redistribution of excess charges among those PECs produces some neutral condensed coacervate droplets as well, coexisting with PECs in a wide range of mixing ratios. Finally, a last process featured with bell-shaped curves indicates the full coacervation that quickens while approaching charge neutrality and/or at higher ionic strength.

Targeting CD44 receptor-positive lung tumors using polysaccharide-based nanocarriers: Influence of nanoparticle size and administration route.

New approaches that are more efficient and able to specifically reach lung tumors are needed. We developed new hyaluronan-based nanoparticles targeting CD44 receptors of two different sizes and compared their lung cancer cells targeting efficacy in vitro and in vivo. The nanoparticles' cellular uptake was dose-dependent, and specific to hyaluronan receptors, particularly CD44. The binding and internalization differed according to nanoparticle size. In vivo biodistribution studies in two orthotopic lung tumor models showed that intrapulmonary nebulized nanoparticles accumulated in lungs, but not in the tumor nodules. In contrast, despite a significant liver capture, intravenous injection led to a better accumulation of the nanoparticles in the lung tumors compared with the surrounding healthy lung tissues. We demonstrated that the hyaluronan-based nanoparticles size plays significant role in cellular uptake and biodistribution. Small nanoparticles showed active targeting of CD44-overexpressing tumors, suggesting that they could be used as drug-delivery system. FROM THE CLINICAL EDITOR: Combating cancers remains an important goal in clinical medicine. In this study, the authors investigated the ability of two hyaluronan-based nanoparticles targeting CD44 receptors to home in on lung cancer cells in an in-vivo orthotropic model. The preferential uptake of smaller sized nanoparticles via intravenous route has further enhanced the existing knowledge of future drug designs.