Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration

Understanding mucus modulation behavior of chitosan oligomers and dextran sulfate combining light scattering and calorimetric observations

This study reports the fundamental understanding of mucus-modulatory strategies combining charged biopolymers with distinct molecular weights and surface charges. Here, key biophysical evidence supports that low-molecular-weight (Mw) polycation chitosan oligosaccharides (COSs) and high-Mw polyanion dextran sulfate (DS) exhibit distinct thermodynamic signatures upon interaction with mucin (MUC), the main protein of mucus. While the COS → MUC microcalorimetric titrations released ~14 kcal/mol and ~60 kcal/mol, the DS → MUC titrations released ~1200 and ~1450 kcal/mol at pH of 4.5 and 6.8, respectively. The MPT-2 titrations of COS → MUC and DS → MUC indicated a greater zeta potential variation at pH = 4.5 (relative variation = 815 % and 351 %, respectively) than at pH = 6.8 (relative variation = 282 % and 136 %, respectively). Further, the resultant binary (COS-MUC) and ternary (COS-DS-MUC) complexes showed opposite behavior (aggregation and charge inversion events) according to the pH environment. Most importantly, the results indicate that electrostatics could not be the driving force that governs COS-MUC interactions. To account for this finding, we proposed a two-level abstraction model. Macro features emerge collectively from individual interactions occurring at the molecular level. Therefore, to understand the outcomes of mucus modulatory strategy based on charged biopolymers it is necessary to integrate both visions into the same picture.

N-Acetyl-Cysteine Increases Activity of Peanut-Shaped Gold Nanoparticles Against Biofilms Formed by Clinical Strains of Pseudomonas aeruginosa Isolated from Sputum of Cystic Fibrosis Patients

Background

Extracellular polymeric substances (EPS) produced by bacteria, as they form a biofilm, determine the stability and viscoelastic properties of biofilms and prevent antibiotics from penetrating this multicellular structure. To date, studies demonstrated that an appropriate optimization of the chemistry and morphology of nanotherapeutics might provide a favorable approach to control their interaction with EPS and/or diffusion within the biofilm matrix. Targeting the biofilms’ EPS, which in certain conditions can adopt liquid crystal structure, was demonstrated to improve the anti-biofilm activity of antibiotics and nanoparticles. A similar effect is achievable by interfering EPS’ production by mucoactive agents, such as N-acetyl-cysteine (NAC). In our previous study, we demonstrated the nanogram efficiency of non-spherical gold nanoparticles, which due to their physicochemical features, particularly morphology, were noted to be superior in antimicrobial activity compared to their spherical-shaped counterparts.

Methods

To explore the importance of EPS matrix modulation in achieving a suitable efficiency of peanut-shaped gold nanoparticles (AuP NPs) against biofilms produced by Pseudomonas aeruginosa strains isolated from cystic fibrosis patients, fluorescence microscopy, as well as resazurin staining were employed. Rheological parameters of AuP NPs-treated biofilms were investigated by rotational and creep-recovery tests using a rheometer in a plate-plate arrangement.

Results

We demonstrated that tested nanoparticles significantly inhibit the growth of mono- and mixed-species biofilms, particularly when combined with NAC. Notably, gold nanopeanuts were shown to decrease the viscosity and increase the creep compliance of Pseudomonas biofilm, similarly to EPS-targeting NAC. Synergistic activity of AuP NPs with tobramycin was also observed, and the AuP NPs were able to eradicate bacteria within biofilms formed by tobramycin-resistant isolates.

Conclusion

We propose that peanut-shaped gold nanoparticles should be considered as a potent therapeutic agent against Pseudomonas biofilms.

Oral nanomedicine for modulating immunity, intestinal barrier functions, and gut microbiome

The gastrointestinal tract (GIT) affects not only local diseases in the GIT but also various systemic diseases. Factors that can affect the health and disease of both GIT and the human body include 1) the mucosal immune system composed of the gut-associated lymphoid tissues and the lamina propria, 2) the intestinal barrier composed of mucus and intestinal epithelium, and 3) the gut microbiota. Selective delivery of drugs, including antigens, immune-modulators, intestinal barrier enhancers, and gut-microbiome manipulators, has shown promising results for oral vaccines, immune tolerance, treatment of inflammatory bowel diseases, and other systemic diseases, including cancer. However, physicochemical and biological barriers of the GIT present significant challenges for successful translation. With the advances of novel nanomaterials, oral nanomedicine has emerged as an attractive option to not only overcome these barriers but also to selectively deliver drugs to the target sites in GIT. In this review, we discuss the GIT factors and physicochemical and biological barriers in the GIT. Furthermore, we present the recent progress of oral nanomedicine for oral vaccines, immune tolerance, and anti-inflammation therapies. We also discuss recent advances in oral nanomedicine designed to fortify the intestinal barrier functions and modulate the gut microbiota and microbial metabolites. Finally, we opine about the future directions of oral nano-immunotherapy.

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.

An overview of gastrointestinal mucus rheology under different pH conditions and introduction to pH-dependent rheological interactions with PLGA and chitosan nanoparticles

This review discusses the physicochemical and mechanical properties of porcine gastrointestinal mucus from a rheological point of view. Considering mucus as a viscoelastic gel that functions as a biological barrier by limiting particles passage, lubricating the gastrointestinal tract, and protecting the stomach from gastric acids. The viscoelastic and protective properties of mucus are mainly produced by its mucin network, which is stabilized through electrostatic, hydrophobic and hydrogen bonding interactions. Otherwise, mucus rheology is determined by its polyanionic nature at physiological pH. At neutral pH, mucus presents a viscous behavior produced by chains crosslinking. While, at acidic pH, mucus exhibits an elastic behavior related with the extended conformation that produces mucus gelation at the stomach. Additionally, rheology studies the degree of adhesion between a polymer-mucus mixture through rheological synergism, and how it varies at different pH conditions. Finally, mucoadhesion phenomenon is exemplified with chitosan (cationic) and poly (lactic-co-glycolic) acid (anionic) polymers.

Implications of the Human Gut-Brain and Gut-Cancer Axes for Future Nanomedicine

Recent clinical and pathological evidence have implicated the gut microbiota as a nexus for modulating the homeostasis of the human body, impacting conditions from cancer and dementia to obesity and social behavior. The connections between microbiota and human diseases offer numerous opportunities in medicine, most of which have limited or no therapeutic solutions available. In light of this paradigm-setting trend in science, this review aims to provide a comprehensive and timely summary of the mechanistic pathways governing the gut microbiota and their implications for nanomedicines targeting cancer and neurodegenerative diseases. Specifically, we discuss in parallel the beneficial and pathogenic relationship of the gut microbiota along the gut-brain and gut-cancer axes, elaborate on the impact of dysbiosis and the gastrointestinal corona on the efficacy of nanomedicines, and highlight a molecular mimicry that manipulates the universal cross-β backbone of bacterial amyloid to accelerate neurological disorders. This review further offers a forward-looking section on the rational design of cancer and dementia nanomedicines exploiting the gut-brain and gut-cancer axes.

Particle coating alters mucociliary transit in excised rat trachea: A synchrotron X-ray imaging study

We have previously developed non-invasive in vivo mucociliary transport (MCT) monitoring methods using synchrotron phase contrast X-ray imaging (PCXI) to evaluate potential therapies for cystic fibrosis (CF). However, previous in vivo measurements of MCT velocity using this method were lower than those from alternate methods. We hypothesise this was due to the surface chemistry of the uncoated particles. We investigated the effect of particle surface coating on MCT marker performance by measuring the velocity of uncoated, positively-charged (aminated; NH₂), and negatively-charged (carboxylated; COOH) particles. The effect of aerosolised hypertonic saline (HS) was also investigated, as previous in vivo measurements showed HS significantly increased MCT rate. PCXI experiments were performed using an ex vivo rat tracheal imaging setup. Prior to aerosol delivery there was little movement of the uncoated particles, whilst the NH₂ and COOH particles moved with MCT rates similar to those previously reported. After application of HS the uncoated and COOH particle velocity increased and NH₂ decreased. This experiment validated the use of COOH particles as MCT marker particles over the uncoated and NH₂ coated particles. Our results suggest that future experiments measuring MCT using synchrotron PCXI should use COOH coated marker particles for more accurate MCT quantification.

Co association of mucus modulating agents and nanoparticles for mucosal drug delivery

Nanoparticulate drug delivery systems (nDDS) offer a variety of options when it comes to routes of administration. One possible path is crossing mucosal barriers, such as in the airways and in the GI tract, for systemic distribution or local treatment. The main challenge with this administration route is that the size and surface properties of the nanoparticles, as opposed to small molecular drugs, very often results in mucosal capture, immobilization and removal, which in turn results in a very low bioavailability. Strategies to overcome this challenge do exist, like surface 'stealth' modification with PEG. Here we review an alternative or supplemental strategy, co-association of mucus modulating agents with the nDDS to improve bioavailability, where the nDDS may be surface modified or unmodified. This contribution presents some examples on how possible co-association systems may be achieved, using currently marketed mucolytic drugs, alternative formulations or novel agents.

Nanoparticle passage through porcine jejunal mucus: Microfluidics and rheology

A micro-slide chamber was used to screen and rank sixteen functionalized fluorescent silica nanoparticles (SiNP) of different sizes (10, 50, 100 and 200 nm) and surface coatings (aminated, carboxylated, methyl-PEG₁₀₀₀ylated, and methyl-PEG₂₀₀₀ylated) according to their capacity to permeate porcine jejunal mucus. Variables investigated were influence of particle size, surface charge and methyl-PEGylation. The anionic SiNP showed higher transport through mucus whereas the cationic SiNP exhibited higher binding with lower transport. A size-dependence in transport was identified - 10 and 50 nm anionic (uncoated or methyl-PEGylated) SiNP showed higher transport compared to the larger 100 and 200 nm SiNP. The cationic SiNP of all sizes interacted with the mucus, making it more viscous and less capable of swelling. In contrast, the anionic SiNP (uncoated or methyl-PEGylated) caused minimal changes in the viscoelasticity of mucus. The data provide insights into mucus-NP interactions and suggest a rationale for designing oral nanomedicines with improved mucopermeability.

Fabrication of NaYF4:Yb,Er Nanoprobes for Cell Imaging Directly by Using the Method of Hydrion Rivalry Aided by Ultrasonic

A novel method of fabricating water-soluble bio-probes with ultra-small size such as NaYF₄:Yb,Er (18 nm), NaGdF₄:Yb,Er (8 nm), CaF₂:Yb,Er (10 nm), PbS (7 nm), and ZnS (12 nm) has been developed to provide for the solubility switch of nanoparticles from oil-soluble to water-soluble in terms of hydrion rivalry aided by ultrasonic. Using NaYF₄:Yb,Er (18 nm) as an example, we evaluate the properties of as-prepared water-soluble nanoparticles (NPs) by using thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy (FTIR), zeta potential (ζ) testing, and 1H nuclear magnetic resonance (¹HNMR). The measured ζ value shows that the newly prepared hydrophilic NaYF₄:Yb,Er NPs are the positively charged particles. Acting as reactive electrophilic moiety, the freshly prepared hydrophilic NaYF₄:Yb,Er NPs have carried out the coupling with amino acids and fluorescence labeling and imaging of HeLa cells directly. Experiments indicate that the method of hydrion rivalry aided by ultrasonic provides a simple and novel opportunity to transform hydrophobic NPs into hydrophilic NPs with good reactivity, which can be imaging some specific biological targets directly.

Probing mucin interaction behavior of magnetic nanoparticles

In this study, we developed iron oxide based magnetic nanoparticles (MNPs) by precipitation of iron salts in the presence of ammonia and created four different formulations: without functionality (plain MNPs, no coating), with β-cyclodextrin (MNPs+β-CD) or pluronic 127 polymer (MNPs+F-127), and both β-cyclodextrin and pluronic 127 polymer (MNPs+β-CD-F-127) functionality for its efficient use in mucosal delivery. We studied the interaction and/or binding behavior of these MNPs formulations with porcine stomach mucin using steady-state fluorescence spectroscopy, and then quantified the bound mucin from absorption studies. Toxicity of these MNPs against cervical cancer cells and red blood cells was evaluated. Ex-vivo studies were performed using freshly collected gastrointestinal, ovarian, pancreas and colon organ tissues of pig to evaluate binding and uptake phenomenon of MNPs. Transport studies of these MNPs in mucin was evaluated using Boyden's chamber assay. All these studies together suggest that the MNPs+β-CD-F-127 formulation was strongly interacted with mucin and interestingly transported through mucin compared to other MNPs formulations. Hence, MNPs+β-CD-F-127 formulation could be a good candidate for the mucoadhesive biopharmaceuticals and drug delivery system.

Core-shell nanocarriers with high paclitaxel loading for passive and active targeting

Rapid blood clearance and premature burst release are inherent drawbacks of conventional nanoparticles, resulting in poor tumor selectivity. iRGD peptide is widely recognized as an efficient cell membrane penetration peptide homing to αVβ3 integrins. Herein, core-shell nanocapsules (NCs) and iRGD-modified NCs (iRGD-NCs) with high drug payload for paclitaxel (PTX) were prepared to enhance the antitumor activities of chemotherapy agents with poor water solubility. Improved in vitro and in vivo tumor targeting and penetration were observed with NCs and iRGD-NCs; the latter exhibited better antitumor activity because iRGD enhanced the accumulation and penetration of NCs in tumors. The NCs were cytocompatible, histocompatible, and non-toxic to other healthy tissues. The endocytosis of NCs was mediated by lipid rafts in an energy-dependent manner, leading to better cytotoxicity of PTX against cancer cells. In contrast with commercial product, PTX-loaded NCs (PTX-NCs) increased area under concentration-time curve (AUC) by about 4-fold, prolonged mean resident time (MRT) by more than 8-fold and reduced the elimination rate constant by greater than 68-fold. In conclusion, the present nanocarriers with high drug-loading capacity represent an efficient tumor-targeting drug delivery system with promising potential for cancer therapy.

A New Class of Safe Oligosaccharide Polymer Therapy To Modify the Mucus Barrier of Chronic Respiratory Disease

The host- and bacteria-derived extracellular polysaccharide coating of the lung is a considerable challenge in chronic respiratory disease and is a powerful barrier to effective drug delivery. A low molecular weight 12-15-mer alginate oligosaccharide (OligoG CF-5/20), derived from plant biopolymers, was shown to modulate the polyanionic components of this coating. Molecular modeling and Fourier transform infrared spectroscopy demonstrated binding between OligoG CF-5/20 and respiratory mucins. Ex vivo studies showed binding induced alterations in mucin surface charge and porosity of the three-dimensional mucin networks in cystic fibrosis (CF) sputum. Human studies showed that OligoG CF-5/20 is safe for inhalation in CF patients with effective lung deposition and modifies the viscoelasticity of CF-sputum. OligoG CF-5/20 is the first inhaled polymer therapy, represents a novel mechanism of action and therapeutic approach for the treatment of chronic respiratory disease, and is currently in Phase IIb clinical trials for the treatment of CF.

General and facile surface functionalization of hydrophobic nanocrystals with poly(amino acid) for cell luminescence imaging

Hydrophobic nanocrystals with various shape, size, and chemical composition were successfully functionalized by poly(amino acid) with one particle per micelle without aggregation or precipitation via a facile, general, and low-cost strategy. Via simply tuning the pH value, multifunctional nanocomposites consisting of different nanocrystals were also fabricated. Due to the poly(amino acid) coating, these nanocrystals are highly water-stable, biocompatible, and bioconjugatable with chemical and biological moieties. Meanwhile, their shape, size, optical/magnetic properties are well retained, which is highly desirable for bioapplications. This developed strategy presents a novel opportunity to apply hydrophobic nanocrystals to various biomedical fields.