An experimental and theoretical approach to understand the interaction between particles and mucosal tissues

Nanonization of poorly water-soluble drugs has shown great potential in improving their oral bioavailability by increasing drug dissolution rate and adhesion to the gastrointestinal mucus. However, the fundamental features that govern the particle-mucus interactions have not been investigated in a systematic way before. In this work, we synthesize mucin hydrogels that mimic those of freshly excised porcine mucin. By using fluorescent pure curcumin particles, we characterize the effect of particle size (200 nm, and 1.2 and 1.3 μm), concentration (18, 35, and 71 μg mL^-1), and hydrogel crosslinking density on the diffusion-driven particle penetration in vitro. Next, we derive a phenomenological model that describes the physics behind the diffusion-derived penetration and considers the contributions of the key parameters assessed in vitro. Finally, we challenge our model by assessing the oral pharmacokinetics of an anti-cancer model drug, namely dasatinib, in pristine and nanonized forms and two clinically relevant doses in rats. For a dose of 10 mg kg^-1, drug nanonization leads to a significant ∼8- and ∼21-fold increase of the drug oral bioavailability and half-life, respectively, with respect to the unprocessed drug. When the dose of the nanoparticles was increased to 15 mg kg^-1, the oral bioavailability increased though not significantly, suggesting the saturation of the mucus penetration sites, as demonstrated by the in vitro model. Our overall results reveal the potential of this approach to pave the way for the development of tools that enable a more rational design of nano-drug delivery systems for mucosal administration. STATEMENT OF SIGNIFICANCE: The development of experimental-theoretical tools to understand and predict the diffusion-driven penetration of particles into mucus is crucial not only to rationalize the design of nanomedicines for mucosal administration but also to anticipate the risks of the exposure of the body to nano-pollutants. However, a systematic study of such tools is still lacking. Here we introduce an experimental-theoretical approach to predict the diffusion-driven penetration of particles into mucus and investigate the effect of three key parameters on this interaction. Then, we challenge the model in a preliminary oral pharmacokinetics study in rats which shows a very good correlation with in vitro results. Overall, this work represents a robust platform for the modelling of the interaction of particles with mucosae under dynamic conditions.

Excipient-Free Pure Drug Nanoparticles Fabricated by Microfluidic Hydrodynamic Focusing

Nanoprecipitation is one of the most versatile methods to produce pure drug nanoparticles (PDNPs) owing to the ability to optimize the properties of the product. Nevertheless, nanoprecipitation may result in broad particle size distribution, low physical stability, and batch-to-batch variability. Microfluidics has emerged as a powerful tool to produce PDNPs in a simple, reproducible, and cost-effective manner with excellent control over the nanoparticle size. In this work, we designed and fabricated T- and Y-shaped Si-made microfluidic devices and used them to produce PDNPs of three kinase inhibitors of different lipophilicity and water-solubility, namely imatinib, dasatinib and tofacitinib, without the use of colloidal stabilizers. PDNPs display hydrodynamic diameter in the 90-350 nm range as measured by dynamic light scattering and a rounded shape as visualized by high-resolution scanning electron microscopy. Powder X-ray diffraction and differential scanning calorimetry confirmed that this method results in highly amorphous nanoparticles. In addition, we show that the flow rate of solvent, the anti-solvent, and the channel geometry of the device play a key role governing the nanoparticle size.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

A Microscopically Motivated Model for Particle Penetration into Swollen Biological Networks

Biological gels (bio-gels) are hydrated polymer networks that serve diverse biological functions, which often lead to intentional or unintentional exposure to particulate matter. In this work, we derive a microscopically motivated framework that enables the investigation of penetration mechanisms into bio-gels. We distinguish between two types of mechanisms: spontaneous (unforced) penetration and forced penetration. Using experimental data available in the literature, we exploit the proposed model to characterize and compare between the microstructures of respiratory, intestinal, and cervicovaginal mucus and two types of biofilms. Next, we investigate the forced penetration process of spherical and ellipsoidal particles into a locally quadrilateral network. The proposed framework can be used to improve and complement the analysis of experimental findings in vitro, ex vivo, and in vivo. Additionally, the insights from this work pave the way towards enhanced designs of nano-medicines and allow the assessment of risk factors related to the nano-pollutants exposure.

Selective Accumulation of Galactomannan Amphiphilic Nanomaterials in Pediatric Solid Tumor Xenografts Correlates with GLUT1 Gene Expression

In this work, we designed, characterized, and investigated the performance of hydrolyzed galactomannan (hGM)-based amphiphilic nanoparticles for selective intratumoral accumulation in pediatric patient-derived sarcomas. To create a self-assembly amphiphilic copolymer, the side chain of hGM was hydrophobized with poly(methyl methacrylate) (PMMA) by utilizing a graft free radical polymerization reaction. Different hGM and MMA weight feeding ratios were used to adjust the critical aggregation concentration and the size and size distribution of the nanoparticles. The ability to actively target glucose transporter-1 (GLUT-1) was studied by fluorescence confocal microscopy and imaging flow cytometry in vitro on Rh30 (rhabdomyosarcoma) and patient-derived Ewing sarcoma (HSJD-ES-001) cell lines with different expression levels of GLUT-1. Results confirmed that the nanoparticles are internalized by ∼100% of the cells at 37 °C. Furthermore, we investigated the biodistribution of the nanoparticles in pediatric patient-derived models of two deadly musculoskeletal tumors, rhabdomyosarcoma and Ewing sarcoma. Outstandingly, the intratumoral accumulation of the nanoparticles correlated very well with the expression level of GLUT1 gene in each patient-derived tumor (P = 0.0141; Pearson's correlation test). Finally, we demonstrated the encapsulation capacity of these nanoparticles by loading 7.5% (w/w) of the hydrophobic first-generation tyrosine kinase inhibitor imatinib. These findings point out the potential of this new type of nanoparticle to target GLUT-1-expressing tumors and selectively deliver anticancer agents.

Nanoparticle-in-microparticle oral drug delivery system of a clinically relevant darunavir/ritonavir antiretroviral combination

Nanonizationhas been extensively investigated to increase theoral bioavailability of hydrophobicdrugsin general andantiretrovirals(ARVs)used inthe therapy of the human immunodeficiency virus (HIV) infection in particular. Weanticipatedthatin the caseofprotease inhibitors, a family of pH-dependent ARVsthatdisplay high aqueous solubility undertheacidconditionsof thestomach andextremely low solubilityunder the neutral ones ofthe small intestine, this strategy might failowing to an uncontrolled dissolution-re-precipitation process that will take place along the gastrointestinal tract.To tackle thisbiopharmaceutical challenge, in this work, wedesigned, produced and fully characterized a novelNanoparticle-in-MicroparticleDelivery System(NiMDS)comprised of pure nanoparticlesofthefirst-line protease inhibitor darunavir(DRV) and itsboosting agentritonavir (RIT) encapsulated within film-coated microparticles.For this, a clinically relevant combination of pure DRV and RIT nanoparticles wassynthesized by a sequential nanoprecipitation/solvent diffusion and evaporation method employing sodium alginateas viscosity stabilizer. Then, pure nanoparticles were encapsulated within calcium alginate/chitosanmicroparticlesthat were film-coated with a series ofpoly(methacrylate) copolymers with differential solubility in the gastrointestinal tract. This coating ensured full stability under gastric-like pH and sustained drug release under intestinal one. PharmacokineticstudiesconductedinalbinoSpragueDawleyratsshowed that DRV/RIT-loadedNiMDSs containing 17% w/w drug loading based on dry weight significantlyincreasedthe oral bioavailabilityof DRVby 2.3-foldwith respect to both theunprocessedandthenanonized DRV/RIT combinations that showed statistically similar performance. Moreover, they highlighted the limited advantage of only drugnanonizationto improve the oral pharmacokinetics of protease inhibitors and the potential of our novel delivery approach to improve the oral pharmacokinetics of nanonized poorly water-soluble drugs displaying pH-dependent solubility.

STATEMENT OF SIGNIFICANCE

Protease inhibitors (PIs) are gold-standard drugs in many ARV cocktails. Darunavir (DRV) is the latest approved PI and it is included in the 20th WHO Model List of Essential Medicines. PIs poorly-water soluble at intestinal pH and more soluble under gastric conditions. Drug nanonization represents one of the most common nanotechnology strategies to increase dissolution rate of hydrophobic drugs and thus, their oral bioavailability. For instance, pure drug nanosuspensions became the most clinically relevant nanoformulation. However, according to the physicochemical properties of PIs, nanonization does not appear as a very beneficial strategy due to the fast dissolution rate anticipated under the acid conditions of the stomach and their uncontrolled recrystallization and precipitation in the small intestine that might result in the formation of particles of unpredictable size and structure (e.g., crystallinity and polymorphism) and consequently, unknown dissolution rate and bioavailability. In this work, we developed a sequential nanoprecipitation method for the production of pure nanoparticles of DRV and its boosting agent ritonavir in a clinically relevant 8:1 wt ratio using alginate as viscosity stabilizer and used this nanosuspension to produce a novel kind of nanoparticle-in-microparticle delivery system that was fully characterized and the pharmacokinetics assessed in rats. The most significant points of the current manuscript are.

Electrohydrodynamic atomization and spray-drying for the production of pure drug nanocrystals and co-crystals

In recent years, nanotechnology has offered attractive opportunities to overcome the (bio)pharmaceutical drawbacks of most drugs such as low aqueous solubility and bioavailability. Among the numerous methodologies that have been applied to improve drug performance, a special emphasis has been made on those that increase the dissolution rate and the saturation solubility by the reduction of the particle size of pure drugs to the nanoscale and the associated increase of the specific surface area. Different top-down and bottom-up methods have been implemented, each one with its own pros and cons. Over the last years, the latter that rely on the dissolution of the drug in a proper solvent and its crystallization or co-crystallization by precipitation in an anti-solvent or, conversely, by solvent evaporation have gained remarkable impulse owing to the ability to adjust features such as size, size distribution, morphology and to control the amorphous/crystalline nature of the product. In this framework, electrohydrodynamic atomization (also called electrospraying) and spray-drying excel due to their simplicity and potential scalability. Moreover, they do not necessarily require suspension stabilizers and dry products are often produced during the formation of the nanoparticles what ensures physicochemical stability for longer times than liquid products. This review overviews the potential of these two technologies for the production of pure drug nanocrystals and co-crystals and discusses the recent technological advances and challenges for their implementation in pharmaceutical research and development.