Characterization of chitosan hydrochloride-mucin interaction by means of viscosimetric and turbidimetric measurements

On the mucoadhesive properties of synthetic and natural polyampholytes

HYPOTHESIS

The mucoadhesive characteristics of amphoteric polymers (also known as polyampholytes) can vary and are influenced by factors such as the solution's pH and its relative position against their isoelectric point (pHIEP). Whilst the literature contains numerous reports on mucoadhesive properties of either cationic or anionic polymers, very little is known about these characteristics for polyampholytes EXPERIMENTS: Here, two amphoteric polymers were synthesized by reaction of linear polyethylene imine (l-PEI) with succinic or phthalic anhydride and their mucoadhesive properties were compared to bovine serum albumin (BSA), selected as a natural polyampholyte. Interactions between these polymers and porcine gastric mucin were studied using turbidimetric titration and isothermal titration calorimetry across a wide range of pHs. Model tablets were designed, coated with these polymers and tested to evaluate their adhesion to porcine gastric mucosa at different pHs. Moreover, a retention study using fluorescein isothiocyanate (FITC)-labelled polyampholytes deposited onto mucosal surfaces was also conducted FINDINGS: All these studies indicated the importance of solution pH and its relative position against pHIEP in the mucoadhesive properties of polyampholytes. Both synthetic and natural polyampholytes exhibited strong interactions with mucin and good mucoadhesive properties at pH < pHIEP.

Challenges and Opportunities in the Oral Delivery of Recombinant Biologics

Recombinant biological molecules are at the cutting-edge of biomedical research thanks to the significant progress made in biotechnology and a better understanding of subcellular processes implicated in several diseases. Given their ability to induce a potent response, these molecules are becoming the drugs of choice for multiple pathologies. However, unlike conventional drugs which are mostly ingested, the majority of biologics are currently administered parenterally. Therefore, to improve their limited bioavailability when delivered orally, the scientific community has devoted tremendous efforts to develop accurate cell- and tissue-based models that allow for the determination of their capacity to cross the intestinal mucosa. Furthermore, several promising approaches have been imagined to enhance the intestinal permeability and stability of recombinant biological molecules. This review summarizes the main physiological barriers to the oral delivery of biologics. Several preclinical in vitro and ex vivo models currently used to assess permeability are also presented. Finally, the multiple strategies explored to address the challenges of administering biotherapeutics orally are described.

Boronic Acid-Tethered Silk Fibroin for pH-Dependent Mucoadhesion

Mucus lines all surfaces of the human body not covered by skin and provides lubrication, hydration, and protection. The properties of mucus are influenced by changes in pH that may occur due to physiological conditions and pathological circumstances. Reinforcing the mucus barrier with biopolymers that can adhere to mucus in different conditions can be a useful strategy for protecting the underlying mucosae from damage. In this work, regenerated silk fibroin (silk) was chemically modified with phenyl boronic acid to form reversible covalent complexes with the 1,2- or 1,3-diols. The silk modified with boronic acid pendant groups has an increased affinity for mucins, whose carbohydrate component is rich in diols. These results offer new applications of silk in mucoadhesion, and the ability to bind diols to the silk lays the foundation for the development of silk-based sugar-sensing platforms.

Chitosan-coated bovine serum albumin nanoparticles for topical tetrandrine delivery in glaucoma: in vitro and in vivo assessment

Glaucoma is one of the leading causes of blindness. Therapies available suffer from several drawbacks including low bioavailability, repeated administration and poor patient compliance with adverse effects thereafter. In this study, bovine serum albumin nanoparticles (BSA-NPs) coated with chitosan(CS) were developed for the topical delivery of tetrandrine (TET) for glaucoma management. Optimized nanoparticles were prepared by desolvation. pH, BSA, CS and cross-linking agent concentrations effects on BSA-NPs colloidal properties were investigated. CS-BSA-NPs with particle size 237.9 nm and zeta potential 24 mV was selected for further evaluation. EE% exceeded 95% with sustained release profile. In vitro mucoadhesion was evaluated based on changes in viscosity and zeta potential upon incubation with mucin. Ex vivo transcorneal permeation was significantly enhanced for CS coated formulation. In vitro cell culture studies on corneal stromal fibroblasts revealed NPs biocompatibility with enhanced cellular uptake and improved antioxidant and anti-proliferative properties for the CS-coated formulation. Moreover, BSA-NPs were nonirritant as shown by HET-CAM test. Also, bioavailability in rabbit aqueous humor showed 2-fold increase for CS-TET-BSA-NPs compared to TET with a sustained reduction in intraocular pressure in a rabbit glaucoma model. Overall, results suggest CS-BSA-NPs as a promising platform for topical ocular TET delivery in the management of glaucoma.

Improved Bioavailability of Poorly Soluble Drugs through Gastrointestinal Muco-Adhesion of Lipid Nanoparticles

Gastrointestinal absorption remains indispensable in the systemic delivery of most drugs, even though it presents several challenges that, paradoxically, may also provide opportunities that can be exploited to achieve maximal bioavailability. Drug delivery systems made from nanoparticle carriers and especially, lipid carriers, have the potential to traverse gastrointestinal barriers and deploy in the lymphatic pathway, which aptly, is free from first pass via the liver. Several poorly soluble drugs have presented improved systemic bioavailability when couriered in lipid nanoparticle carriers. In this review, we propose an additional frontier to enhancing the bioavailability of poorly soluble drugs when encapsulated in lipid nano-carriers by imparting muco-adhesion to the particles through application of appropriate polymeric coating to the lipid carrier. The combined effect of gastrointestinal muco-adhesion followed by lymphatic absorption is a promising approach to improving systemic bioavailability of poorly soluble drugs following oral administration. Evidence to the potential of this approach is backed-up by recent studies within the review.

Insight into the Lubrication and Adhesion Properties of Hyaluronan for Ocular Drug Delivery

Hyaluronan (HA) is widely used for eye drops as lubricant to counteract dry eye disease. High and low molecular weight HA are currently used in ophthalmology. However, a large portion of the current literature on friction and lubrication addresses articular (joint) cartilage. Therefore, eye drops compositions based on HA and its derivatized forms are extensively characterized providing data on the tribological and mucoadhesive properties. The physiochemical properties are investigated in buffers used commonly in eye drops formulations. The tribological investigation reveals that amphiphilic HA-C12 decreases the friction coefficient. At the same time, the combination of trehalose/HA or HAC12 enhances up to eighty-fold the mucoadhesiveness. Thus, it is predicted a prolonged residence time on the surface of the eye. The incorporation of trehalose enhances the protection of human keratinocytes (HaCaT) cells, as demonstrated in an in-vitro cell-desiccation model. The presence of trehalose increases the friction coefficient. Medium molecular weight HA shows significantly lower friction coefficient than high molecular weight HA. This research represents a first, wide array of features of diverse HA forms for eye drops contributing to increase the knowledge of these preparations. The results here presented also provide valuable information for the design of highly performing HA-formulations addressing specific needs before preclinic.

Cubosomal lipid nanoassemblies with pH-sensitive shells created by biopolymer complexes: A synchrotron SAXS study

We report a strategy for sustainable development of pH-responsive cubic liquid crystalline nanoparticles (cubosomes), in which the structure-defining lyotropic nonlamellar lipid and the eventually encapsulated guest molecules can be protected by pH-sensitive polyelectrolyte shells with mucoadhesive properties. Bulk non-lamellar phases as well as pH-responsive polyelectrolyte-modified nanocarriers were formed by spontaneous assembly of the nonlamellar lipid monoolein and two biopolymers tailored in nanocomplexes with pH-dependent net charge. The mesophase particles involved positively charged N-arginine-modified chitosan (CHarg) and negatively charged alginate (ALG) chains assembled at different biopolymer concentrations and charge ratios into a series of pH-responsive complexes. The roles of Pluronic F127 as a dispersing agent and a stabilizer of the nanoscale dispersions were examined. Synchrotron small-angle X-ray scattering (SAXS) investigations were performed at several N-arginine-modified chitosan/alginate ratios (CHarg/ALG with 10, 15 and 20 wt% ALG relative to CHarg) and varying pH values mimicking the pH conditions of the gastrointestinal route. The structural parameters characterizing the inner cubic liquid crystalline organizations of the nanocarriers were determined as well as the particle sizes and stability on storage. The surface charge variations, influencing the measured zeta-potentials, evidenced the inclusion of the CHarg/ALG biopolymer complexes into the lipid nanoassemblies. The polyelectrolyte shells rendered the hybrid cubosome nanocarriers pH-sensitive and influenced the swelling of their lipid-phase core as revealed by the acquired SAXS patterns. The pH-responsiveness and the mucoadhesive features of the cubosomal lipid/polyelectrolyte nanocomplexes may be of interest for in vivo drug delivery applications.

Dopamine-loaded lipid based nanocarriers for intranasal administration of the neurotransmitter: A comparative study

Both dopamine (DA) loaded Solid Lipid Nanoparticles (SLN) and liposomes (Lip), designed for intranasal administration of the neurotransmitter as an innovative Parkinson disease treatment, were already characterized in vitro in some extent by us (Trapani et al., 2018a and Cometa et al., 2020, respectively). Herein, to gain insight into the structure of SLN, X-ray Photoelectron Spectroscopy Analysis was carried out and DA-SLN (SLN 1) were found to exhibit high amounts of the neurotransmitter on the surface, whereas the external side of Glycol Chitosan (GCS) containing SLN (SLN 2) possessed only few amounts. However, SLN 2 were characterized by the highest encapsulation DA efficiency (i.e., 81%). Furthermore, in view of intranasal administration, mucoadhesion tests in vitro were also conducted for SLN and Lip formulations, evidencing high muchoadesive effect exerted by SLN 2. Concerning ex-vivo studies, SLN and Lip were found to be safe for Olfactory Ensheathing Cells and fluorescent SLN 2 were taken up in a dose-dependent manner reaching the 100% of positive cells, while Lip 2 (chitosan-glutathione-coated) were internalised by 70% OECs with six-times more lipid concentration. Hence, SLN 2 formulation containing DA and GCS may constitute interesting formulations for further studies and promising dosage form for non-invasive nose-to-brain neurotransmitter delivery.

Cyto/Biocompatibility of Dopamine Combined with the Antioxidant Grape Seed-Derived Polyphenol Compounds in Solid Lipid Nanoparticles

Background: The loss of nigrostriatal neurons containing dopamine (DA) together with the "mitochondrial dysfunction" in midbrain represent the two main causes related to the symptoms of Parkinson's disease (PD). Hence, the aim of this investigation is to co-administer the missing DA and the antioxidant grape seed-derived proanthocyanidins (grape seed extract, GSE) in order to increase the levels of the neurotransmitter (which is unable to cross the Blood Brain Barrier) and reducing the oxidative stress (OS) related to PD, respectively. Methods: For this purpose, we chose Solid Lipid Nanoparticles (SLN), because they have been already proven to increase DA uptake in the brain. DA-SLN adsorbing GSE (GSE/DA-SLN) were formulated and subjected to physico-chemical characterization, and their cytocompatibility and protection against OS were examined. Results: GSE was found on SLN surface and release studies evidenced the efficiency of GSE in preventing DA autoxidation. Furthermore, SLN showed high mucoadhesive strength and were found not cytotoxic to both primary Olfactory Ensheathing and neuroblastoma SH-SY5Y cells by MTT test. Co-administration of GSE/DA-SLN and the OS-inducing neurotoxin 6-hydroxydopamine (100 μM) resulted in an increase of SH-SY5Y cell viability. Conclusions: Hence, SLN formulations containing DA and GSE may constitute interesting candidates for non-invasive nose-to-brain delivery.

Antibacterial Activity of N,O-Acylated Chitosan Derivative

The antibacterial activity of N,O-acylated chitosan derivative with linoleic acid (CH_LA) was tested by disc and well diffusion, agar impregnation and microdilution methods against Staphylococcus aureus, Escherichia coli and Helicobacter pylori strains. Hydrophobically modified chitosan (HMC) was expected to exhibit enhanced antibacterial activity and specific mucin interactions. Although diffusion tests have not indicated the antibacterial potential of chitosan (CH) or CH_LA, the results of the microdilution method demonstrated that tested polymers significantly reduced the amount of living bacteria cells in different concentrations depending on the microorganism. Additionally, CH_LA was characterized by enhanced antibacterial activity compared to CH, which may suggest a different mechanism of interaction with S. aureus and H. pylori. Furthermore, the UV-VIS analysis revealed that the amphiphilic character of derivative led to strong CH_LA–mucin interactions. The study proved the high potential of CH_LA in antibacterial applications, especially for the gastrointestinal tract.

Synthesis and characterization of novel chitosan-dopamine or chitosan-tyrosine conjugates for potential nose-to-brain delivery

This work aims to the synthesis of novel carboxylated chitosan-dopamine (DA) and -tyrosine (Tyr) conjugates as systems for improving the brain delivery of the neurotransmitter DA following nasal administration. For this purpose, ester or amide conjugates were synthesized by N,N-dicyclohexylcarbodiimide (DCC) mediated coupling reactions between the appropriate N-tert-butyloxycarbonyl (Boc) protected starting polymers N,O-carboxymethyl chitosan and 6-carboxy chitosan and DA or O-tert-Butyl-L-tyrosine-tert-butyl ester hydrochloride. The resulting conjugates were characterized by FT-IR and ¹H- and ¹³C NMR spectroscopies and their in vitro mucoadhesive properties in simulated nasal fluid (SNF), toxicity and uptake from Olfactory Ensheathing Cells (OECs) were assessed. Results demonstrated that N,O-carboxymethyl chitosan-DA conjugate was the most mucoadhesive polymer in the series examined and, together with the 6-carboxy chitosan-DA-conjugate were able to release the neurotransmitter in SNF. The MTT assay showed that the starting polymers as well as all the prepared conjugates in OECs resulted not toxic at any concentration tested. Likewise, the three synthesized conjugates were not cytotoxic as well. Cytofluorimetric analysis revealed that the N,O-carboxymethyl chitosan DA conjugate was internalized by OECs in a superior manner at 24 h as compared with the starting polymer. Overall, the N,O-CMCS-DA conjugate seems promising for improving the delivery of DA by nose-to-brain administration.

Nanoscale poly(acrylic acid)-based hydrogels prepared via a green single-step approach for application as low-viscosity biomimetic fluid tears

The present work reports a nanotechnology strategy to prepare a low-viscosity poly(acrylic acid) (PAAc)-based tear substitute with enhanced efficacy and compliance. Specifically, nanogels composed of PAAc and polyvinylpyrrolidone (PVP) were prepared by adapting an ionizing radiation method. For this purpose, different aqueous systems: PVP/PAAc nanoparticulate complexes, PVP/acrylic acid (AAc), N-vinylpyrrolidone (N-VP)/PAAc, and N-VP/AAc were exposed to gamma rays. The dynamic light scattering technique showed that stable nanogels are only produced in a relatively high yield from the PVP/AAc system. Nanogel formation was driven by the hydrogen-bonding complexation between PVP and PAAc (formed in situ) as well as the radiation-induced cross-linking. Transparency, viscosity and mucoadhesiveness of emerged nanogels were optimized by controlling the feed composition and irradiation dose. Furthermore, neutralized nanogels were topically applied in a dry eye model and compared with a PAAc-based commercial tear substitute, namely Vidisic® Gel. The results of Schirmer's test and tear break-up time demonstrated that nanogels prepared from AAc-rich feed solutions at 20 kGy enhanced markedly the dry eye conditions. The histopathological analysis also ensured the competence of PAAc-rich nanogels to completely return the corneal epithelium to its normal state.

Dual-Functioning Scaffolds for the Treatment of Spinal Cord Injury: Alginate Nanofibers Loaded with the Sigma 1 Receptor (S1R) Agonist RC-33 in Chitosan Films

The present work proposed a novel therapeutic platform with both neuroprotective and neuroregenerative potential to be used in the treatment of spinal cord injury (SCI). A dual-functioning scaffold for the delivery of the neuroprotective S1R agonist, RC-33, to be locally implanted at the site of SCI, was developed. RC-33-loaded fibers, containing alginate (ALG) and a mixture of two different grades of poly(ethylene oxide) (PEO), were prepared by electrospinning. After ionotropic cross-linking, fibers were incorporated in chitosan (CS) films to obtain a drug delivery system more flexible, easier to handle, and characterized by a controlled degradation rate. Dialysis equilibrium studies demonstrated that ALG was able to form an interaction product with the cationic RC-33 and to control RC-33 release in the physiological medium. Fibers loaded with RC-33 at the concentration corresponding to 10% of ALG maximum binding capacity were incorporated in films based on CS at two different molecular weights-low (CSL) and medium (CSM)-solubilized in acetic (AA) or glutamic (GA) acid. CSL- based scaffolds were subjected to a degradation test in order to investigate if the different CSL salification could affect the film behavior when in contact with media that mimic SCI environment. CSL AA exhibited a slower biodegradation and a good compatibility towards human neuroblastoma cell line.

Mechanical and Surface Properties of Resilient Denture Liners Modified with Chitosan Salts

Chitosan (CS) and its derivatives show antibacterial and antifungal properties and could help treat and prevent denture stomatitis (DS). Mechanical and surface properties of resilient denture liners were evaluated when modified with CS salts. CS-hydrochloride (CS-HCl) and CS-glutamate (CS-G) were added to resilient denture liners Ufi Gel P and Coe-Soft at four different concentrations (0.1%, 0.2%, 0.4%, 1% w/w) from which specimens were produced, as well as a control group of each material with no added CS salt. Ten specimens per group (Ø 35 mm, height 6 mm) were manufactured. They were stored in distilled water at 37 °C for a total of 30 days (d). Shore A hardness (SHA) and surface roughness (Ra) were evaluated after 24 h (T1), 7 d (T2), 14 d (T3) and 30 d (T4). Kruskal-Wallis and U-test (Bonferroni-Holm adjusted) were used for statistical analysis (p ≤ 0.05). Ra increased significantly once CS salts were added. SHA increased significantly for some groups, but all specimens fulfilled requirements set by ISO 10139-2:2016. Modification with CS salts does not influence the mechanical properties of the modified resilient denture liners in a clinically relevant manner. Despite the increased roughness, the concept is suitable for further studies. Especially antimicrobial/antibiofilm studies are needed.

Novel O/W nanoemulsions for nasal administration: Structural hints in the selection of performing vehicles with enhanced mucopenetration

We propose novel oil-in-water nanoemulsions (O/W NEs) including PEGylated surfactants and chitosan, showing good biocompatibility and optimization for nasal administration of drugs or vaccines. The transmucosal route has been shown to be ideal for a fast and efficient absorption and represents a viable alternative when the oral administration is problematic. The critical structural features in view of optimal encapsulation and transmucosal delivery were assessed by characterizing the NEs with complementary scattering techniques, i.e. dynamic light scattering (DLS), small angle X-ray (SAXS) and neutron scattering (SANS). Combined results allowed for selecting the formulations with the best suited structural properties and in addition establishing their propensity to enter the mucus barrier. To this scope, mucin was used as a model system and the effect of adding chitosan to the NEs, as adjuvant, was investigated. Remarkably, the presence of chitosan had a positive impact on the diffusion of the NE particles through the mucin matrix. We can infer that chitosan-mucin interaction induces density inhomogeneity and an increase in the pore size within the gel matrix that enhances the PEGylated NEs mobility. The coupling of mucoadhesive and mucopenetrating agents is shown to be a promising strategy for innovative transmucosal delivery systems.

Interaction Between Chitosan and Mucin: Fundamentals and Applications

The term chitosan (CS) refers to a family of aminopolysaccharides derived from chitin. Among other properties, CS is nontoxic, mucoadhesive and can be used for load and transport drugs. Given these and other physicochemical and biological properties, CS is an optimal biopolymer for the development of transmucosal drug delivery systems, as well as for the treatment of pathologies related to mucosal dysfunctions. Mucins are glycoprotein macromolecules that are the major components of mucus overlaying epithelia. CS interacts with mucin and adsorbs on and changes the rheology of mucus. However, CS and mucins denote families of polymers/macromolecules with highly variable chemical structure, properties, and behavior. To date, their interactions at the molecular level have not been completely unraveled. Also, the properties of complexes composed of CS and mucin vary as a function of the sources and preparation of the polymers. As a consequence, the mucoadhesion and drug delivery properties of such complexes vary as well. The breadth of this review is on the molecular interactions between CS and mucin. In particular, in vitro and ex vivo characterization methods to investigate both the interactions at play during the formation of CS-mucin complexes, and the advances on the use of CS for transmucosal drug delivery are addressed.

A transferrin receptor-binding mucoadhesive elastin-like recombinamer: In vitro and in vivo characterization

The development of mucoadhesive materials is of great interest and is also a major challenge. Being adsorption sites, mucosae are suitable targets for drug delivery, but as defensive barriers they are complex biological surfaces to interact with, mainly due to their protective mucus layer. As such, first- and second-generation mucoadhesives focused on material-mucus interactions, whereas the third generation of mucoadhesives introduced structural motifs that are able to interact with the cells beneath the mucus layer. The combination of different prerequisites (water solubility, soft gel formation at body temperature and able to interact with the mucus) in a single molecule is easily achieved using elastin-like recombinamers (ELRs) given their multiple block design. Moreover, we have been able to introduce a short amino-acid sequence known as T7 that is able to bind to transferrin receptors in the epithelial cell layer. The T7 sequence enhances the cell-binding properties of the mucoadhesive ELR (MELR), as demonstrated using a Caco-2 epithelial cell model. In vivo experiments confirmed the mucoadhesive properties found in vitro. STATEMENT OF SIGNIFICANCE: The development of a mucoadhesive material is a major challenge. Mucosae are suitable targets for drug delivery, but as defense barriers, they are complex surfaces to interact with. In this work we report the first ELR that combines different functional blocks, in a single molecule, which provide it with the properties of soft-gel forming at body temperature and being able of efficiently adhering to the mucus layer of mucosas, as well as to the underlying epithelial cell layer, as demonstrated in vitro and in vivo. The rationally designed materials presented in this work sets the basis for developing ELR-based, mucosa-directed drug delivery systems, which could improve patient's compliance, enhancing drug retention at the mucosal site.

Interactions of salivary mucins and saliva with food proteins: a review

Mucins are long glycoprotein molecules responsible for the gel nature of the mucous layer that covers epithelial surfaces throughout the body. Mucins, as the major salivary proteins, are also important proteins for the food oral processing and digestion. The interactions of salivary mucins and saliva with several food proteins and food protein emulsions, as well as their functional properties related to the food oral processing were reviewed in this paper. The target food proteins of focus were whey proteins (lactoferrin and beta-lactoglobulin) and non-whey proteins (casein, gelatin, galectin/lectin, and proline-rich proteins). Most of the studies suggest that electrostatic attraction (between positively charged food proteins with negatively charged moieties of mucin mainly on glycosylated region of mucin) is the major mode of interaction between them. On the other hand, casein attracts the salivary proteins only via non-covalent interactions due to its naturally self-assembled micellar structure. Moreover, recent studies related to β-lactoglobulin (BLG)-mucin interactions have clarified the importance of hydrophobic as well as hydrophilic interactions, such as hydrogen bonding. Furthermore, in vitro studies between protein emulsions and saliva observed a strong aggregating effect of saliva on caseinate and whey proteins as well as on surfactant-stabilized emulsions. Besides, the sign and the density of the charge on the surface of the protein emulsion droplets contribute significantly to the behavior of the emulsion when mixed with saliva. Other studies also suggested that the interactions between saliva and whey proteins depends on the pH in addition to the flow rate of the saliva. Overall, the role of interactions of food proteins and food protein emulsions with mucin/saliva-proteins in the oral perception, as well as the physicochemical and structural changes of proteins were discussed.

Solid Lipid Nanoparticles and Chitosan-coated Solid Lipid Nanoparticles as Promising Tool for Silybin Delivery: Formulation, Characterization, and In vitro Evaluation

Background:

Silybin (Sb) is the major flavolignan of the extract of Silybum marianum. It is used for the treatment of various acute and chronic liver toxicities, inflammation, fibrosis and oxidative stress. Many studies indicate that Sb is also active against different carcinomas and it has been very recently proposed to be beneficial in type 2 diabetes patients. However, Sb is a low water soluble and low permeable compound.

Objective:

In this study, Solid Lipid Nanoparticles (SLNs) were proposed to enhance the solubility and the intestinal absorption of Sb. </P><P> Methods: SLNs were made of stearic acid and Brij 78 and subsequently coated with chitosan. Formulations were physically and chemically characterized. Stability studies were also assessed. Sb in vitro release was evaluated in different pH media. In vitro permeability test with artificial membranes and Caco-2 cells were performed. Cellular uptake and mucoadhesion studies were conducted.

Results:

Both nanoparticles were found to be stable. In vitro release indicated that SLNs may prevent burst release and gastric degradation of Sb. Higher extent of Sb permeation was observed for both nanoparticles in PAMPA and Caco-2 cell monolayer models. The results of the cellular uptake study suggested the involvement of active endocytic processes. Chitosan significantly improves mucoadhesion properties of nanoparticles. </P><P> Conclusions: Together with the excellent stability, strong mucoadhesive property, and slow release, chitosan coated SLNs demonstrated promising potential to enhance absorption of hydrophobic Sb after oral administration.

Encapsulation of Babchi Oil in Cyclodextrin-Based Nanosponges: Physicochemical Characterization, Photodegradation, and In Vitro Cytotoxicity Studies

Babchi (Psoralea corylifolia) oil is an important essential oil used in several traditional medicines to cure various disorders. This phytotherapeutic agent possesses a number of pharmacological activities including antibacterial, antifungal, antioxidant, anti-inflammatory, immunomodulatory, and antitumor factors. However, volatile nature, poor stability, and solubility of babchi oil (BO) restrict its pharmaceutical applications. Therefore, the aim of the present work was to encapsulate this oil in β-cyclodextrin nanosponges (NS) in order to overcome the above limitations. To fabricate nanosponges, β-cyclodextrin was cross-linked with diphenyl carbonate in different molar ratios viz. 1:2, 1:4, 1:6, 1:8, and 1:10. The blank nanosponges were loaded with BO using the freeze-drying method. The particle size of the BO loaded nanosponges was found to lie between 200 and 500 nm with low polydispersity index. Furthermore, the zeta potential, the Fourier transform infrared spectroscopy, X-ray diffraction, thermal analysis, and electron microscopy were carried out for characterization of BO nanosponges. Results obtained from spectral analysis ascertained the formation of inclusion complexes. Additionally, solubilisation efficiency of BO was checked in distilled water and found enhanced by 4.95 times with optimized β-cyclodextrin nanosponges. The cytotoxicity study was carried out by the MTT assay using HaCaT cell lines. A significant improvement in photo-stability of essential oil was also observed by inclusion innanosponges. Lastly, the optimized formulation was tested for antibacterial activity using Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. Therefore, encapsulation of BO in nanosponges resulted in efficacious carrier system in terms of solubility, photo-stability, and safety of this oil along with handling benefits.

Rheological analysis and mucoadhesion: A 30 year-old and still active combination

At the end of 80s and in the early 90s, an increasing interest in the development of mucoadhesive formulations occurred in the pharmaceutical field. Such formulations, prolonging the drug permanence on the mucosa of action/absorption, improve drug availability/bioavailability and therefore its therapeutic effectiveness. Among the various methods reported in the literature for the evaluation of the mucoadhesive properties of polymers, in the early 1990s, the study of the rheological variation of the polymer solutions after mixing with a mucin solution/dispersion has been proposed as an approach to measure the strength of the mucoadhesive joint. Even today, both viscosity and viscoelastic measurements are used to evaluate the ability of polymers and formulations to adhere to the mucosa of application/action. This review aims at providing an overview of the rheological approaches employed in the development and characterization of mucoadhesive formulation, highlighting their advantages and disadvantages. To do this the scientific path that, since the beginning of the 90s, has led to the affirmation of the rheological analysis as a useful tool for the evaluation of the strength of the mucoadhesive bond is retraced.

Mucus-penetrating solid lipid nanoparticles for the treatment of cystic fibrosis: Proof of concept, challenges and pitfalls

Nanocarrier-mediated transmucosal drug delivery based on conventional mucoadhesive, muco-inert or mucus-penetrating nanoparticles (NPs) is a growing field especially in challenging diseases like cystic fibrosis (CF). Efficacy of such systems dictates profound investigation of particle-mucus interaction and factors governing the whole process. Although variable techniques studying particle diffusion in mucus have been introduced, standardized procedures are lacking. The study comprised different methods based on micro- and macro-displacement as well as colloidal stability and turbidimetric experiments. Artificial sputum medium (ASM), CF sputum and mucus-secreting cell line (Calu-3 air interface culture, AIC) were applied. Solid lipid nanoparticles (SLNs) coated with variable hydrophilic sheath (poloxamer, Tween 80 or PVA) represented the nanocarriers under investigation. Both micro-displacement studies based on single particle tracking and macro-displacement experiments based on 3D-time laps confocal imaging revealed faster diffusion of poloxamer- > Tween- > PVA-coated SLNs. Compared to ASM, CF sputum showed not only lower diffusion rates but also remarkable discrepancies in particle-mucus diffusion rate due to sputum heterogenicity. Meanwhile, in case of Calu-3 AIC, thickness of the mucosal layer as well as density of mucus network were key determinants in the diffusion process. The points emphasized in this study highlight the road towards in vivo relevant particle-mucus interaction research.

Chitosan Nanoparticles as a Mucoadhesive Drug Delivery System for Ocular Administration

Pharmaceutical approaches based on nanotechnologies and the development of eye drops composed of the mucoadhesive polymers chitosan and hyaluronic acid are emerging strategies for the efficient treatment of ocular diseases. These innovative nanoparticulate systems aim to increase drugs’ bioavailability at the ocular surface. For the successful development of these systems, the evaluation of mucoahesiveness (the interaction between the ocular delivery system and mucins present on the eye) is of utmost importance. In this context, the aim of the present work was to investigate the mucoadhesivity of a novel nanoparticle eye drop formulation containing an antibiotic (ceftazidime) intended to treat eye infections. Eye drop formulations comprised a polymer (hydroxypropyl) methyl cellulose (HPMC) 0.75% (w/v) in an isotonic solution incorporating chitosan/sodium tripolyphosphate (TPP)-hyaluronic acid-based nanoparticles containing ceftazidime. The viscosity of the nanoparticles, and the gels incorporating the nanoparticles were characterized in contact with mucin at different mass ratios, allowing the calculation of the rheological synergism parameter (∆η). Results showed that at different nanoparticle eye formulation:mucin weight ratios, a minimum in viscosity occurred which resulted in a negative rheological synergism. Additionally, the results highlighted the mucoadhesivity of the novel ocular formulation and its ability to interact with the ocular surface, thus increasing the drug residence time in the eye. Moreover, the in vitro release and permeation studies showed a prolonged drug release profile from the chitosan/TPP-hyaluronic acid nanoparticles gel formulation. Furthermore, the gel formulations were not cytotoxic on ARPE-19 and HEK293T cell lines, evaluated by the metabolic and membrane integrity tests. The formulation was stable and the drug active, as shown by microbiological studies. In conclusion, chitosan/TPP-hyaluronic acid nanoparticle eye drop formulations are a promising platform for ocular drug delivery with enhanced mucoadhesive properties.

Shell-crosslinked zein nanocapsules for oral codelivery of exemestane and resveratrol in breast cancer therapy

Aim: Oral administration of exemestane (EXM) and resveratrol (RES) for breast cancer therapy has been limited by their poor solubility and low permeability. Methods: In this study, these issues were tackled using zein nanocapsules (ZNCs) for oral EXM/RES codelivery combining drug solubilization within oily core and resistance to digestion via hydrophobic protein shell. Furthermore, higher oral stability and sustained release could be enabled by glutaraldehyde crosslinking of zein shell. Results & conclusion: EXM/RES-ZNCs showed enhanced cytotoxicity against MCF-7 and 4T1 breast cancer cells compared with free drug combination with higher selectivity to cancer cells rather than normal fibroblasts. In vivo, crosslinked EXM/RES-ZNCs markedly reduced the percentage increase of Ehrlich ascites mammary tumor volume in mice by 2.4-fold compared with free drug combination.

Chitosan Ascorbate Nanoparticles for the Vaginal Delivery of Antibiotic Drugs in Atrophic Vaginitis

The aim of the present work was the development of chitosan ascorbate nanoparticles (CSA NPs) loaded into a fast-dissolving matrix for the delivery of antibiotic drugs in the treatment of atrophic vaginitis. CSA NPs loaded with amoxicillin trihydrate (AX) were obtained by ionotropic gelation in the presence of pentasodium tripolyphosphate (TPP). Different CSA:TPP and CSA:AX weight ratios were considered and their influence on the particle size, polydispersion index and production yield were investigated. CSA NPs were characterized for mucoadhesive, wound healing and antimicrobial properties. Subsequently, CSA NPs were loaded in polymeric matrices, whose composition was optimized using a DoE (Design of Experiments) approach (simplex centroid design). Matrices were obtained by freeze-drying aqueous solutions of three hydrophilic excipients, polyvinylpirrolidone, mannitol and glycin. They should possess a mechanical resistance suitable for the administration into the vaginal cavity and should readily dissolve in the vaginal fluid. In addition to antioxidant properties, due to the presence of ascorbic acid, CSA NPs showed in vitro mucoadhesive, wound healing and antimicrobial properties. In particular, nanoparticles were characterized by an improved antimicrobial activity with respect to a chitosan solution, prepared at the same concentration. The optimized matrix was characterized by mechanical resistance and by the fast release in simulated vaginal fluid of nanoparticles characterized by unchanged size.

A Polymer Chemistry Point of View on Mucoadhesion and Mucopenetration

Although oral is the preferred route of administration of pharmaceutical formulations, the long-standing challenge for medically active compounds to efficiently cross the mucus layer barrier limits its wider applicability. Efforts in nanomedicine to overcome this hurdle consider mucoadhesive and mucopenetrating drug carriers by selectively designing (macromolecular) building blocks. This review highlights and critically discusses recent strategies developed in this context including poly(ethylene glycol)-based modifications, cationic and thiolated polymers, as well as particles with high charge density, zeta-potential shifting ability, or mucolytic properties. The latest advances in ex vivo test platforms are also reviewed.

Role of Nitric Oxide-Releasing Chitosan Oligosaccharides on Mucus Viscoelasticity

Nitric oxide (NO)-releasing chitosan oligosaccharides were modified with ester functional groups to examine how the mucoadhesive nature of the scaffold impacts the ability of NO to degrade mucins from human bronchial epithelial cell cultures and clinical sputum samples collected from patients with cystic fibrosis (CF). Agarose gel electrophoresis experiments indicated that the mucoadhesive NO-releasing chitosan oligosaccharides degraded both the purified mucins and sputum, while control scaffolds (without NO release or mucoadhesive ligands) had no effect on mucin structure. Microscopic observations of sputum treated with the mucoadhesive NO-releasing chitosan oligosaccharide confirmed degradation of the mucin and DNA networks. Similarly, the viscosity and elasticity of sputum were reduced upon treatment with the mucoadhesive NO-releasing chitosan, demonstrating the potential utility of these NO-releasing scaffolds as mucolytic agents.

Spray-dried mucoadhesives for intravesical drug delivery using N-acetylcysteine- and glutathione-glycol chitosan conjugates

This work describes N-acetylcysteine (NAC)- and glutathione (GSH)-glycol chitosan (GC) polymer conjugates engineered as potential platform useful to formulate micro-(MP) and nano-(NP) particles via spray-drying techniques. These conjugates are mucoadhesive over the range of urine pH, 5.0-7.0, which makes them advantageous for intravesical drug delivery and treatment of local bladder diseases. NAC- and GSH-GC conjugates were generated with a synthetic approach optimizing reaction times and purification in order to minimize the oxidation of thiol groups. In this way, the resulting amount of free thiol groups immobilized per gram of NAC- and GSH-GC conjugates was 6.3 and 3.6mmol, respectively. These polymers were completely characterized by molecular weight, surface sulfur content, solubility at different pH values, substitution and swelling degree. Mucoadhesion properties were evaluated in artificial urine by turbidimetric and zeta (ζ)-potential measurements demonstrating good mucoadhesion properties, in particular for NAC-GC at pH 5.0. Starting from the thiolated polymers, MP and NP were prepared using both the Büchi B-191 and Nano Büchi B-90 spray dryers, respectively. The resulting two formulations were evaluated for yield, size, oxidation of thiol groups and ex-vivo mucoadhesion. The new spray drying technique provided NP of suitable size (<1μm) for catheter administration, low degree of oxidation, and sufficient mucoadhesion property with 9% and 18% of GSH- and NAC-GC based NP retained on pig mucosa bladder after 3h of exposure, respectively.

STATEMENT OF SIGNIFICANCE

The aim of the present study was first to optimize the synthesis of NAC-GC and GSH-GC, and preserve the oxidation state of the thiol moieties by introducing several optimizations of the already reported synthetic procedures that increase the mucoadhesive properties and avoid pH-dependent aggregation. Second, starting from these optimized thiomers, we studied the feasibility of manufacturing MP and NP by spray-drying techniques. The aim of this second step was to produce mucoadhesive drug delivery systems of adequate size for vesical administration by catheter, and comparable mucoadhesive properties with respect to the processed polymers, avoiding thiolic oxidation during the formulation. MP with acceptable size produced by spray-dryer Büchi B-191 were compared with NP made with the apparatus Nano Büchi B-90.

Rationally designed nanocarriers for intranasaltherapy of allergic rhinitis: influence of carrier type on in vivo nasal deposition

The aim of this study is to develop a locally acting nasal delivery system of triamcinolone acetonide (TA) for the maintenance therapy of allergic rhinitis. The effect of encapsulating TA in different nanocarriers on its mucosal permeation and retention as well as in vivo nasal deposition has been studied. A comparative study was established between polymeric oil core nanocapsules (NCs), lipid nanocarriers such as nanoemulsion (NE), and nanostructured lipid carriers (NLCs). The elaborated nanocarriers were compared with TA suspension and the commercially available suspension "Nasacort(®)". The study revealed that NC provided the highest mucosal retention, as 46.14%±0.048% of the TA initial dose was retained after 24 hours, while showing the least permeation through the nasal mucosa. On the other hand, for TA suspension and Nasacort(®), the mucosal retention did not exceed 23.5%±0.047% of the initial dose after 24 hours. For NE and NLC, values of mucosal retention were 19.4%±0.041% and 10.97%±0.13%, respectively. NC also showed lower mucosal irritation and superior stability compared with NE. The in vivo nasal deposition study demonstrated that NC maintained drug in its site of action (nasal cavity mucosa) for the longest period of time. The elaborated polymeric oil core NCs are efficient carriers for the administration of nasally acting TA as it produced the least permeation results, thus decreasing systemic absorption of TA. Although NCs have been administered via various routes, this is the first study to implement the polymeric oil core NC as an efficient carrier for localized nasal drug delivery.

Mucoadhesive and thermogelling systems for vaginal drug delivery

This review focuses on two formulation approaches, mucoadhesion and thermogelling, intended for prolonging residence time on vaginal mucosa of medical devices or drug delivery systems, thus improving their efficacy. The review, after a brief description of the vaginal environment and, in particular, of the vaginal secretions that strongly affect in vivo performance of vaginal formulations, deals with the above delivery systems. As for mucoadhesive systems, conventional formulations (gels, tablets, suppositories and emulsions) and novel drug delivery systems (micro-, nano-particles) intended for vaginal administration to achieve either local or systemic effect are reviewed. As for thermogelling systems, poly(ethylene oxide-propylene oxide-ethylene oxide) copolymer-based and chitosan-based formulations are discussed as thermogelling systems. The methods employed for functional characterization of both mucoadhesive and thermogelling drug delivery systems are also briefly described.