Effect of Chitosan-Coated Alginate Microspheres on the Permeability of Caco-2 Cell Monolayers

Selective binding of cationic fibrinogen-mimicking chitosan nanoparticles to activated platelets and efficient drug release for antithrombotic therapy

Thrombosis is the main cause of catastrophic events including ischemic stroke, myocardial infarction and pulmonary embolism. Acetylsalicylic acid (ASA) therapy offers a desirable approach to antithrombosis through a reduction of platelet reactivity. However, major bleeding complications, severe off-target side effects, and resistance or nonresponse to ASA greatly attenuate its clinical outcomes. Herein, we report a cationic fibrinogen-mimicking nanoparticle, denoted as ASA-RGD-CS@TPP, to achieve activated-platelet-targeted delivery and efficient release of ASA for safer and more effective antithrombotic therapy. This biomimetic antithrombotic system was prepared by one-pot ionic gelation between cationic arginine-glycine-aspartic acid (RGD)-grafted chitosan (RGD-CS) and anionic tripolyphosphate (TPP). The platform exhibited selective binding to activated platelets, leading to efficient release of ASA and subsequent attenuation of platelet functions, including the remarkable inhibition of platelet aggregation through a potent blockage of cyclooxygenase-1 (COX-1). After intravenous administration, ASA-RGD-CS@TPP displayed significantly prolonged circulation time and successful prevention of thrombosis in a mouse model. ASA-RGD-CS@TPP was demonstrated to significantly enhance antithrombotic therapy while showing minimal coagulation and hemorrhagic risks and excellent biocompatibility in vivo as compared to free ASA. This platform provides a simple, safe, effective and targeted strategy for the development of antithrombotic nanomedicines.

Food Additive Solvents Increase the Dispersion, Solubility, and Cytotoxicity of ZnO Nanoparticles

Zinc oxide (ZnO) nanoparticles (NPs) are utilized as a zinc (Zn) fortifier in processed foods where diverse food additives can be present. Among them, additive solvents may strongly interact with ZnO NPs by changing the dispersion stability in food matrices, which may affect physico-chemical and dissolution properties as well as the cytotoxicity of ZnO NPs. In this study, ZnO NP interactions with representative additive solvents (methanol, glycerin, and propylene glycol) were investigated by measuring the hydrodynamic diameters, solubility, and crystallinity of ZnO NPs. The effects of these interactions on cytotoxicity, cellular uptake, and intestinal transport were also evaluated in human intestinal cells and using in vitro human intestinal transport models. The results revealed that the hydrodynamic diameters of ZnO NPs in glycerin or propylene glycol, but not in methanol, were significantly reduced, which is probably related to their high dispersion and increased solubility under these conditions. These interactions also caused high cell proliferation inhibition, membrane damage, reactive oxygen (ROS) generation, cellular uptake, and intestinal transport. However, the crystal structure of ZnO NPs was not affected by the presence of additive solvents. These findings suggest that the interactions between ZnO NPs and additive solvents could increase the dispersion and solubility of ZnO NPs, consequently leading to small hydrodynamic diameters and different biological responses.

Determination of Two Differently Manufactured Silicon Dioxide Nanoparticles by Cloud Point Extraction Approach in Intestinal Cells, Intestinal Barriers and Tissues

Food additive amorphous silicon dioxide (SiO₂) particles are manufactured by two different methods—precipitated and fumed procedures—which can induce different physicochemical properties and biological fates. In this study, precipitated and fumed SiO₂ particles were characterized in terms of constituent particle size, hydrodynamic diameter, zeta potential, surface area, and solubility. Their fates in intestinal cells, intestinal barriers, and tissues after oral administration in rats were determined by optimizing Triton X-114-based cloud point extraction (CPE). The results demonstrate that the constituent particle sizes of precipitated and fumed SiO₂ particles were similar, but their aggregate states differed from biofluid types, which also affect dissolution properties. Significantly higher cellular uptake, intestinal transport amount, and tissue accumulation of precipitated SiO₂ than of fumed SiO₂ was found. The intracellular fates of both types of particles in intestinal cells were primarily particle forms, but slowly decomposed into ions during intestinal transport and after distribution in the liver, and completely dissolved in the bloodstream and kidneys. These findings will provide crucial information for understanding and predicting the potential toxicity of food additive SiO₂ after oral intake.

Optimization of Caco-2 and HT29 co-culture in vitro cell models for permeability studies

The purpose of this study was to investigate the appropriate proportion of Caco-2 and HT29 co-culture in vitro cell models for permeability studies. The results showed that the transepithelial electrical resistance values of 9:1 and 1:0 groups (263 ± 3.61 and 300 ± 7.55) after 21-day culture were >250 Ω cm(2), which were suitable for further experiments. The confocal laser microscopy showed that the group of 9:1 (Caco-2:HT29) had the highest integrity, whereas the group of 0:1 (Caco-2:HT29) exhibited the lowest. The staining study confirmed that mucus was successfully produced by HT29 cells, and it was also produced in co-cultures with Caco-2 cells model, but the Caco-2 monocultures did not have any blue staining, which made us affirm that mucus is only produced in the presence of HT29 cells. The real-time PCR results showed that the total highest expression level of ALPi and MUC5AC was the ratio of 9:1 (Caco-2:HT29) and lowest is 1:1 (Caco-2:HT29). So we concluded that 9:1 (Caco-2:HT29) is the optimal Caco-2 to HT29 ratio in the in vitro model co-culture for permeability studies.

Nanoparticle toxicity by the gastrointestinal route: evidence and knowledge gaps

The increasing interest in nanoparticles for advanced technologies, consumer products, and biomedical applications has led to great excitement about potential benefits but also concern over the potential for adverse human health effects. The gastrointestinal tract represents a likely route of entry for many nanomaterials, both directly through intentional ingestion or indirectly via nanoparticle dissolution from food containers or by secondary ingestion of inhaled particles. Additionally, increased utilisation of nanoparticles may lead to increased environmental contamination and unintentional ingestion via water, food animals, or fish. The gastrointestinal tract is a site of complex, symbiotic interactions between host cells and the resident microbiome. Accordingly, evaluation of nanoparticles must take into consideration not only absorption and extraintestinal organ accumulation but also the potential for altered gut microbes and the effects of this perturbation on the host. The existing literature was evaluated for evidence of toxicity based on these considerations. Focus was placed on three categories of nanomaterials: nanometals and metal oxides, carbon-based nanoparticles, and polymer/dendrimers with emphasis on those particles of greatest relevance to gastrointestinal exposures.

Biocompatibility of chitosan carriers with application in drug delivery

Chitosan is one of the most used polysaccharides in the design of drug delivery strategies for administration of either biomacromolecules or low molecular weight drugs. For these purposes, it is frequently used as matrix forming material in both nano and micron-sized particles. In addition to its interesting physicochemical and biopharmaceutical properties, which include high mucoadhesion and a great capacity to produce drug delivery systems, ensuring the biocompatibility of the drug delivery vehicles is a highly relevant issue. Nevertheless, this subject is not addressed as frequently as desired and even though the application of chitosan carriers has been widely explored, the demonstration of systems biocompatibility is still in its infancy. In this review, addressing the biocompatibility of chitosan carriers with application in drug delivery is discussed and the methods used in vitro and in vivo, exploring the effect of different variables, are described. We further provide a discussion on the pros and cons of used methodologies, as well as on the difficulties arising from the absence of standardization of procedures.

Facilitated nanoscale delivery of insulin across intestinal membrane models

The effect of nanoparticulate delivery system on enhancing insulin permeation through intestinal membrane was evaluated in different intestinal epithelial models using cell cultures and excised intestinal tissues. Multilayered nanoparticles were formulated by encapsulating insulin within a core consisting of alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin. Insulin permeation through Caco-2 cell monolayer was enhanced 2.1-fold, facilitated by the nanoparticles compared with insulin alone, 3.7-fold through a mucus-secreting Caco-2/HT29 co-culture, and 3.9-fold through excised intestinal mucosa of Wistar rats. Correlation of Caco-2/HT29 co-culture cells with the animal-model intestinal membrane demonstrates that the mucus layer plays a significant role in determining the effectiveness of oral nanoformulations in delivering poorly absorbed drugs. Albumin was applied to the nanoparticles as outermost coat to protect insulin through shielding from proteolytic degradation. The effect of the albumin layering on insulin permeation was compared with albumin-free nanoparticles that mimic the result of albumin being enzymatically removed during gastric and intestinal transport. Results showed that albumin layering is important toward improving insulin transport across the intestinal membrane, possibly by stabilizing insulin in the intestinal conditions. Transcellular permeation was evidenced by internalization of independently labeled insulin and nanoparticles into enterocytes, in which insulin appeared to remain associated with the nanoparticles. Transcellular transport of insulin through rat intestinal mucosa may represent the predominant mechanism by which nanoparticles facilitate insulin permeation. Nanoformulations demonstrated biocompatibility with rat intestinal mucosa through determination of cell viability via monitoring of mitochondrial dehydrogenases. Insulin permeation facilitated by the biocompatible nanoparticles suggests a potential carrier system in delivering protein-based drugs by the oral route.

Tight junction modulation by chitosan nanoparticles: comparison with chitosan solution

Present work investigates the potential of chitosan nanoparticles, formulated by the ionic gelation with tripolyphosphate (TPP), to open the cellular tight junctions and in doing so, improve the permeability of model macromolecules. A comparison is made with chitosan solution at equivalent concentrations. Initial work assessed cytotoxicity (through MTS and LDH assays) of chitosan nanoparticles and solutions on Calu-3 cells. Subsequently, a concentration of chitosan nanoparticles and solution exhibiting minimal toxicity was used to investigate the effect on TEER and macromolecular permeability across filter-cultured Calu-3 monolayer. Chitosan nanoparticles and solution were also tested for their effect on the distribution of the tight junction protein, zonnula occludens-1 (ZO-1). Chitosan nanoparticles produced a sharp and reversible decrease in TEER and increased the permeability of two FITC-dextrans (FDs), FD4 (MW 4 kDa) and FD10 (MW 10 kDa), with effects of a similar magnitude to chitosan solution. Chitosan nanoparticles produced changes in ZO-1 distribution similar to chitosan solution, indicating a tight junction effect. While there was no improvement in permeability with chitosan nanoparticles compared to solution, nanoparticles provide the potential for drug incorporation, and hence the possibility for providing controlled drug release and protection from enzymatic degradation.

Colloidal carrier integrating biomaterials for oral insulin delivery: Influence of component formulation on physicochemical and biological parameters

Strategies to design effective and safe colloidal carriers for biopharmaceuticals have evolved through applying the knowledge gained in nanotechnology to medicine. Designing a colloidal carrier to serve as a protein delivery device requires an understanding of the effect of different materials on the physicochemical, physiological and toxicological parameters for clinical application. The purpose of this study was to evaluate the influence of formulation components on the physicochemical factors and biological function involved in the development and optimization of newly designed nanoparticles for orally dosed insulin. Biodegradable, biocompatible, mucoadhesive and protease-protective biomaterials were combined through ionotropic pre-gelation and polyelectrolyte complexation forming an alginate, dextran sulfate and poloxamer hydrogel containing insulin, stabilized in nanoparticles with chitosan and poly(ethyleneglycol) and coated with albumin. Nanoparticles ranged in size from 200 to 500nm with 70-90% insulin entrapment efficiency, and electrostatic stabilization was suggested by zeta potential values lower than -30mV. This combination of formulation components was selected for insulin protection against harsh gastric pH and proteolytic conditions, and to improve insulin absorption through intestinal mucosa by combining nanoparticle uptake and insulin release at the site of absorption. Insulin was shown to be bioactive after nanoparticle formulation and release in neutral pH conditions. Fourier transform infrared spectroscopy was used to confirm the presence of formulations components in the nanoparticle structure and to identify potential interactions between biomaterials.

Extracellular matrix stability of primary mammalian chondrocytes and intervertebral disc cells cultured in alginate-based microbead hydrogels

Three-dimensional alginate constructs are widely used as carrier systems for transplantable cells. In the present study, we evaluated the chondrogenic matrix stability of primary rat chondrocytes and intervertebral disc (IVD) cells cultured in three different alginate-based microbead matrices to determine the influence of microenvironment on the cellular and metabolic behaviors of chondrogenic cells confined in alginate microbeads. Cells entrapped in calcium, strontium, or barium ion gelled microbeads were monitored with the live/dead dual fluorescent cell viability assay kit and the 1,9-dimethylmethylene blue (DMB) assay designed to evaluate sulfated glycosaminoglycan (s-GAG) production. Expression of chondrogenic extracellular matrix (ECM) synthesis was further evaluated by semiquantitative RT-PCR of sox9, type II collagen, and aggrecan mRNAs. Results indicate that Ca and Sr alginate maintained significantly higher population of living cells compared to Ba alginate (p < 0.05). Production of s-GAG was similarly higher in Ca and Sr alginate microbead cultures compared to Ba alginate microbeads. Although there was no significant difference between strontium and calcium up to day 14 of culture, Sr alginate showed remarkably improved cellular and metabolic activities on long-term cultures, with chondrocytes expressing as much as 31% and 44% greater s-GAG compared to calcium and barium constructs, respectively, while IVD cells expressed 63% and 74% greater s-GAG compared to calcium and barium constructs, respectively, on day 28. These findings indicate that Sr alginate represent a significant improvement over Ca- and Ba alginate microbeads for the maintenance of chondrogenic phenotype of primary chondrocytes and IVD cells.

Effect of N-betainate and N-piperazine derivatives of chitosan on the paracellular transport of mannitol in Caco-2 cells

The effects of novel quaternary chitosan derivatives on the paracellular transport of mannitol and cell viability were studied in the Caco-2 cell model. The N-betainate derivative with the degree of substitution of 0.05 was very effective at 1.0% (w/v) concentration. The activity decreased as the degree of substitution increased. The cytotoxicity of N-betainates was rather low. The N-piperazines were at least equally effective as the N-betainates with a similar degree of substitution (>0.15). Most of the N-piperazines did not exert toxic effects on the cell monolayers. Overall, the inverse proportionality between the degree of substitution and activity suggests that an intact chitosan backbone is essential for the bioactivity of chitosan derivatives. The quaternary group does not substitute for the activity of the free amine group. In particular, the N-betainate derivatives of chitosan should contain only the minimum number of substituents required for water solubility.