Hyaluronan nanoplatelets exert an intrinsic anti-inflammatory activity in a rat model of bladder painful syndrome/interstitial cystitis.

Glycosaminoglycan (GAG) replenishment therapy consists of the instillation of GAG solutions directly in the bladder to alleviate Bladder Painful Syndrome/Interstitial Cystitis (BPS/IC). However, several issues were reported with this strategy because the GAG solutions are rapidly eliminated from the bladder by spontaneous voiding, and GAG have low bioadhesive behaviors. Herein, GAG nanomaterials with typical flattened morphology were obtained by a self-assembly process. The formation mechanism of those nanomaterials, denoted as nanoplatelets, involves the interaction of α-cyclodextrin cavity and alkyl chains covalently grafted on the GAG. Three GAG were used in this investigation, hyaluronan (HA), chondroitin sulfate (CS), and heparin (HEP). HA NP showed the best anti-inflammatory activity in an LPS-induced in vitro inflammation model of macrophages. They also exhibited the best therapeutic efficacy in a BPS/IC rat inflammation model. Histological examinations of the bladders revealed that HA NP significantly reduced bladder inflammation and regenerated the bladder mucosa. This investigation could open new perspectives to alleviate BPS/IC through GAG replenishment therapy.

Real-time visualization of morphology-dependent self-motion of hyaluronic acid nanomaterials in water.

Drug delivery to target sites is often limited by inefficient particle transport through biological media. Herein, motion behaviors of spherical and nonspherical nanomaterials composed of hyaluronic acid were studied in water using real-time multiple particle tracking technology. The two types of nanomaterials have comparable surface compositions and surface potentials, and they have equivalent diameters. The analysis of nanomaterial trajectories revealed that particles with flattened morphology and a high aspect ratio, designated nanoplatelets, exhibited more linear trajectories and faster diffusion in water than nanospheres. Fitting the plots of mean square displacement vs. time scale suggests that nanoplatelets exhibited hyperdiffusive behavior, which is similar to the motion of living microorganisms. Furthermore, at 37 °C, the surface explored by a nanoplatelet was up to 33-fold higher than that explored by a nanosphere. This investigation on morphology-dependent self-motion of nanomaterials could have a significant impact on drug delivery applications by increasing particle transport through biological media.

Role of the interactions of soft hyaluronan nanomaterials with CD44 and supported bilayer membranes in the cellular uptake.

Increasing valence by acting on nanomaterial morphology can enhance the ability of a ligand to specifically bind to targeted cells. Herein, we investigated cell internalization of soft hyaluronic acid (HA) nanoplatelets (NPs) that exhibit a typical hexagonal shape, flat surfaces and high aspect ratio (Γ≈12 to 20), as characterized by atomic force microscopy in hydrated conditions. Fluorescence imaging revealed that internalization of HA-NPs by a T24 tumor cell line and by macrophages was higher than native polysaccharide in a dose-dependent and time-dependent manners. The ability of HA-NPs to efficiently compete with native HA assessed using Bio-layer interferometry showed that NPs had a stronger interaction with recombinant CD44 receptor compared to native HA. The results were discussed regarding physical properties of the NPs and the implication of multivalent interactions in HA binding to CD44. Experiments conducted on supported bilayer membranes with different compositions showed that non-specific interactions of NPs with lipid membranes were negligible. Our findings provide insights into intracellular drug delivery using soft HA-NPs through receptor-mediated multivalent interactions.

Mucoadhesive Poloxamer-Based Hydrogels for the Release of HP-ß-CD-Complexed Dexamethasone in the Treatment of Buccal Diseases.

Oral lichen planus (OLP) is an ongoing and chronic inflammatory disease affecting the mucous membrane of the oral cavity. Currently, the treatment of choice consists in the direct application into the buccal cavity of semisolid formulations containing a corticosteroid molecule to decrease inflammatory signs and symptoms. However, this administration route has shown various disadvantages limiting its clinical use and efficacy. Indeed, the frequency of application and the incorrect use of the preparation may lead to a poor efficacy and limit the treatment compliance. Furthermore, the saliva clearance and the mechanical stress present in the buccal cavity also involve a decrease in the mucosal exposure to the drug. In this context, the design of a new pharmaceutical formulation, containing a steroidal anti-inflammatory, mucoadhesive, sprayable and exhibiting a sustained and controlled release seems to be suitable to overcome the main limitations of the existing pharmaceutical dosage forms. The present work reports the formulation, optimization and evaluation of the mucoadhesive and release properties of a poloxamer 407 thermosensitive hydrogel containing a poorly water-soluble corticosteroid, dexamethasone acetate (DMA), threaded into hydroxypropyl-beta-cyclodextrin (HP-ß-CD) molecules. Firstly, physicochemical properties were assessed to ensure suitable complexation of DMA into HP-ß-CD cavities. Then, rheological properties, in the presence and absence of various mucoadhesive agents, were determined and optimized. The hydration ratio (0.218-0.191), the poloxamer 407 (15-17 wt%) percentage and liquid-cyclodextrin state were optimized as a function of the gelation transition temperature, viscoelastic behavior and dynamic flow viscosity. Deformation and resistance properties were evaluated in the presence of various mucoadhesive compounds, being the sodium alginate and xanthan gum the most suitable to improve adhesion and mucoadhesion properties. Xanthan gum was shown as the best agent prolonging the hydrogel retention time up to 45 min. Furthermore, xanthan gum has been found as a relevant polymer matrix controlling drug release by diffusion and swelling processes in order to achieve therapeutic concentration for prolonged periods of time.

Hierarchically built hyaluronan nano-platelets have symmetrical hexagonal shape, flattened surfaces and controlled size.

Most of nanomaterials composed of hyaluronic acid (HA) used for drug targeting are spherical. In this investigation, we suggest that the morphology of HA nanomaterials could be considered as a new parameter to control their interactions with cells. However, designing nanomaterials with elongated morphology and controlled size is still challenging. The aim of this study was to design and to characterize non-spherical HA nanomaterials with flat surfaces and to highlight main parameters controlling the size. Nanoparticles were formed by mixing HA hydrophobically-modified with palmitoyl groups (PA-HA) and α-cyclodextrin in water. These particles, called nano-platelets, had symmetrical hexagonal shape, flattened surfaces and were 9-fold larger than thick. Small nano-platelets with well-defined shape were obtained with low PA-HA degree of substitution, by adding 5 wt% of α-cyclodextrin solution for a fixed concentration of PA-HA (1 wt%) (569 nm) and for long stirring periods (735-538 nm for 72-168 h). PA-HA was successfully conjugated to a near-infrared fluorescent probe suitable for in vitro and in vivo experiments without nano-platelet size and surface charge modification. This is the first report showing the design of non-spherical and flattened HA nano-platelets that could be used to study the impact of nanomaterial shape on molecular interactions with cells.

Hierarchical supramolecular platelets from hydrophobically-modified polysaccharides and α-cyclodextrin: Effect of hydrophobization and α-cyclodextrin concentration on platelet formation.

Micro- and nano-platelets are a group of particles with typical flat surfaces and hexagonal shape. They are obtained by hierarchical self-assembly in water of α-cyclodextrin and polysaccharides hydrophobically-modified with alkyl chains. It is expected that the formation of well structured and cohesive platelets is driven by the interaction between alkyl chains grafted on polysaccharides and α-cyclodextrin. The objective of this investigation is to tune platelet formation by modifying these two parameters, independently on polysaccharide composition. A systematic study was conducted by varying polysaccharide type (dextran, pullulan, amylopectin), degree of substitution (DS:0.1-5.6%) and α-cyclodextrin concentration (0-10 wt%) for a fixed concentration of polysaccharide esterified with palmitoyl groups (1 wt%). Characterizations include ATR-FTIR, elemental analysis, solid state 13C NMR and transmission electron microscopy. Abundant and well-organized hexagonal platelets were obtained with high DS (4.2-5.6%) and a concentration of α-cyclodextrin higher than 2.5 wt%. Isothermal titration calorimetry revealed a sequential binding with a stoichiometry of 2 α-cyclodextrin molecules for 1 palmitoyl group grafted on dextran. This is the first report showing the possibility to control platelet formation by modifying DS and α-cyclodextrin concentration, independently on polysaccharide composition.

New insights on the structure of hexagonally faceted platelets from hydrophobically modified chitosan and α-cyclodextrin.

A new class of non-spherical particles was recently designed in our research group by mixing a polysaccharide grafted with fatty acids and α-cyclodextrin in water. Because their flat surfaces, and according to their size, particles are called micro- or nano-platelets. Here, we varied the composition of fatty acids grafted on chitosan (oleic acid, palmitic acid or stearic acid) and characterized platelet morphology. Transmission electron microscopy (TEM), cryogenic TEM, scanning electron microscopy, atomic force microscopy (AFM) and confocal laser scanning microscopy experiments showed that the platelets have a preferentially hexagonal shape with sharp edges, independently on alkyl chain grafted on chitosan. Furthermore, AFM topographic analysis of platelet surface showed parallel thin terraces with 12-14-nm height, suggesting a multi-layered structure alternating chitosan and fatty-acid/α-cyclodextrin inclusion complexes. We also revealed for the first time that a simple magnetic mixing of fatty acids with α-cyclodextrin in water results from solid inclusion complexes with a crystalline structural organization characterized by powder X-ray diffraction. Our results demonstrate that fatty acid/α-cyclodextrin interaction is the driving force for platelet formation.

Autoassemblies of α-Cyclodextrin and Grafted Polysaccharides: Crystal Structure and Specific Properties of the Platelets.

Cyclodextrins (CDs) are a family of oligosaccharides with a toroid shape, which exhibit a remarkable ability to include guest molecules in their internal cavity, providing a hydrophobic environment for poorly soluble molecules. Recently, new types of inclusions of α CDs with alkyl grafted polysaccharide chains (pullulan, chitosan, dextran, amylopectin, chondroitin sulfate...) have been prepared which are autoassembled into micro- and nanoplatelets. We report in this paper an extensive investigation of platelets with different compositions, including their reversible hydration (thermogravimetric analysis), crystalline structure (powder X-ray diffraction), dimensions and shapes (scanning electron microscopy-field emission gun), thermal properties, solubility, and melting (micro-differential scanning calorimetry). The crystalline platelets exhibit layered structures intercalating the polysaccharide backbones and CD complexes hosting the grafted alkyl chains. The monoclinic symmetry of columnar-type crystals suggests a head-to-tail arrangement of the CDs. The platelets have a preferentially hexagonal shape with sharp edges, variable sizes, and thicknesses and sometimes show incomplete layers (terraces). The crystal parameters change upon dehydration. Melting temperatures of platelets in aqueous solutions exceed 100 °C. Finally, we discuss the potential relation between the platelet structure and applications for mucoadhesive devices.

Pickering emulsions with α-cyclodextrin inclusions: Structure and thermal stability.

This paper explores structural, interfacial and thermal properties of two types of Pickering emulsions containing α-cyclodextrin inclusion complexes: on one hand, emulsions were obtained between aqueous solutions of α-cyclodextrin and different oils (fatty acids, olive oil, silicone oil) and on the other hand, emulsions were obtained between these oils, water and micro or nano-platelet suspensions with inclusion complexes of hydrophobically-modified polysaccharides. The emulsions exhibit versatile properties according to the molecular architecture of the oils. Experiments were performed by microcalorimetry, X-ray diffraction and confocal microscopy. The aptitude of oil molecules to be threaded in α-cyclodextrin cavity is a determining parameter in emulsification and thermal stability. The heat flow traces and images showed dissolution, cooperative melting and de-threading of inclusion complexes which take place progressively, ending at high temperatures, close or above 100°C. Another important feature observed in the emulsions with micro-platelets is the partial substitution of the guest molecules occurring at room temperature at the oil/water interfaces without dissolution, possibly by a diffusion mechanism of the oil. Accordingly, the dissolution and the cooperative melting temperatures of the inclusion crystals changed, showing marked differences upon the type of guest molecules. The enthalpies of dissolution of crystals were measured and compared with soluble inclusions.