Design, synthesis, fabrication and in vitro evalution of mucoadhesive 5-amino-2-mercaptobenzimidazole chitosan as low water soluble drug carriers

Achieving strong, stable, and durable underwater adhesives based on a simple and generic amino-acid-resembling design

Developing underwater adhesives is important in many applications. Despite extensive progress, achieving strong, stable, and durable underwater adhesion via a simple and effective way is still challenging, mainly due to the conflict between the interfacial and bulk properties. Here, we report a unique bio-inspired strategy to facilely construct superior underwater adhesives with desirable interfacial and bulk properties. For adhesive design, a hydrophilic backbone is utilized to quickly absorb water for effective dehydration, and a novel amino acid-resembling functional block is developed to provide versatile molecular interactions for high interfacial adhesion. Moreover, the conjunction of these two components enables the generation of abundant covalent crosslinks for robust bulk cohesion. Such a rational design allows the adhesive to present a boosted underwater adhesion (3.92 MPa to glass), remarkable durability (maintaining high strength after one month), and good stability in various harsh environments (pH, salt, high temperature, and organic solvents). This strategy is generic, allowing the derivation of more similar adhesive designs easily and triggering new thinking for designing bio-inspired adhesives and beyond.

Phenylboronic acid modified hydrogel materials and their potential for use in contact lens based drug delivery

The use of hydrogel-based contact lens materials holds promise for ophthalmic drug delivery by increasing drug residence time, improving drug bioavailability, reducing administration frequency, and enhancing special site targeting. Issues such as ease of manufacturing, lens comfort and appropriate release kinetics must be considered. Furthermore, the high water content of hydrogel materials can result in rapid and poorly controlled release kinetics. Herein, we modified common hydrogels used in contact lens manufacturing with phenylboronic acid (PBA). PBA addresses these material design issues since boronate esters are easily formed when boron acid and diols interact, opening up a pathway for simple modification of the model lens materials with saccharide based wetting agents. The wetting agents have the potential to improve lens comfort. Furthermore, the hydrophobicity of PBA and the presence of diols can be useful to help control drug release kinetics. In this work, polymerizable 3-(acrylamido)phenylboronic acid (APBA) was synthesized and incorporated into various hydrogels used in contact lens applications, including poly(2-hydroxyethylmethacrylate) (PHEMA), polyvinylpyrrolidone (PVP) and poly(N,N-dimethyl acrylamide) (PDMA) using UV induced free radical polymerization. The APBA structure and its incorporation into the hydrogel materials were confirmed by NMR and FTIR. The materials were shown to interact with and bind wetting agents such as hyaluronan (HA) and hydroxypropyl guar (HPG) by simple soaking in an aqueous solution. The equilibrium water content of the modified materials was characterized, demonstrating that most materials are still in the appropriate range after the introduction of the hydrophobic PBA. The release of three model ophthalmic drugs with varying hydrophilicity, atropine, atropine sulfate and dexamethasone, was examined. The presence of PBA in the materials was found to promote sustained drug release due to its hydrophobic nature. The results suggest that the modification of the materials with PBA was able to not only provide a mucoadhesive property that enhanced wetting agent interactions with the materials, but had the potential to alter drug release. Thus, the modification of contact lens materials with mucoadhesive functionality may be useful in the design of hydrogel contact lenses for ophthalmic drug release and wetting agent binding.

Nanoparticle-Mediated Delivery of Emodin via Colonic Irrigation Attenuates Renal Injury in 5/6 Nephrectomized Rats

Our previous study showed that emodin enema modulates gut microbiota and delays CKD progression. However, the poor solubility, limited colonic irrigation retention time, and inadequate colon adhesion of emodin hinder its clinical application. Based on the deficiencies of emodin, we prepared monomethoxy-poly (ethylene glycol)-poly (lactic acid)-chitosan-2-mercaptobenzimidazole nanoparticles with incorporated emodin (emodin-NP) and studied their efficacy in delaying CKD progression. 5/6 nephrectomized Male Sprague Dawley rats were administered via colonic irrigation with emodin-NP every two days for eight weeks. We found that treatment with emodin-NP improved the kidney function of the rats and limited the expansion of tubulointerstitial fibrosis. Treatment with emodin-NP once every two days is comparable to emodin treatment once a day. Furthermore, emodin-NP via colonic irrigation remarkably reduced IL-1β, IL-6, and LPS levels in serum, improved intestinal barrier functions, and downregulated the key proteins (TLR4, MyD88, and NF-κB) expression in intestinal TLR4 signaling pathway. 16S rDNA analyses showed that emodin-NP can regulate microbiota disturbance in CKD. Taken together, these results suggest that emodin-NP alleviates kidney dysfunction and tubulointerstitial fibrosis by mediation through the modification of gut microbiota disorders. Emodin-NP may be a new method to treat CKD.

Thiolated Chitosans: A Multi-talented Class of Polymers for Various Applications

Various properties of chitosan can be customized by thiolation for very specific needs in a wide range of application areas. Since the discovery of thiolated chitosans, many studies have proven their advantageous characteristics, such as adhesion to biological surfaces, adjustable cross-linking and swelling behavior, controllable drug release, permeation as well as cellular uptake enhancement, inhibition of efflux pumps and enzymes, complexation of metal ions, antioxidative properties, and radical scavenging activity. Simultaneously, these polymers remain biodegradable without increased toxicity. Within this Review, an overview about the different possibilities to covalently attach sulfhydryl ligands to the polymeric backbone of chitosan is given, and the resulting versatile physiochemical properties are discussed in detail. Furthermore, the broad spectrum of applications for thiolated chitosans in science and industry, ranging from their most advanced use in pharmaceutical and medical science over wastewater treatment to the impregnation of textiles, is addressed.

Chitosan and its Derivatives for Ocular Delivery Formulations: Recent Advances and Developments

Chitosan (CS) is a hemi-synthetic cationic linear polysaccharide produced by the deacetylation of chitin. CS is non-toxic, highly biocompatible, and biodegradable, and it has a low immunogenicity. Additionally, CS has inherent antibacterial properties and a mucoadhesive character and can disrupt epithelial tight junctions, thus acting as a permeability enhancer. As such, CS and its derivatives are well-suited for the challenging field of ocular drug delivery. In the present review article, we will discuss the properties of CS that contribute to its successful application in ocular delivery before reviewing the latest advances in the use of CS for the development of novel ophthalmic delivery systems. Colloidal nanocarriers (nanoparticles, micelles, liposomes) will be presented, followed by CS gels and lenses and ocular inserts. Finally, instances of CS coatings, aiming at conferring mucoadhesiveness to other matrixes, will be presented.

Phenylboronic acid-tethered chondroitin sulfate-based mucoadhesive nanostructured lipid carriers for the treatment of dry eye syndrome

Dry eye syndrome is a common eye disease that affects many people worldwide. It is usually treated with eye drops, which has low bioavailability owing to rapid clearance from the ocular surface and leads to poor patient compliance and side effects. For the purpose of improving the therapeutic efficacy, nanostructured lipid carrier (NLC)-loaded dexamethasone (DEX) was prepared and functionalized with (3-aminomethylphenyl)boronic acid-conjugated chondroitin sulfate (APBA-ChS). As APBA has a boronic acid group, it can form a high-affinity complex with sialic acids present in the ocular mucin, which contributes to extension of corneal retention time and improvement of drug delivery. Compared with eye drops, Rhodamine B (RhB)-labeled APBA-ChS-NLC could significantly prolong the residence time on the corneal surface. Moreover, the DEX-APBA-ChS-NLC showed no irritation to the rabbit eye as indicated in irritation studies and histological images. The pharmacodynamics study indicated that DEX-APBA-ChS-NLC could relieve symptoms of dry eye disease in rabbits. These results demonstrated that the developed mucoadhesive drug carrier could improve the delivery of drugs and have promising potential to treat anterior eye diseases. STATEMENT OF SIGNIFICANCE: In this research, (3-aminomethylphenyl)boronic acid-conjugated chondroitin sulfate (APBA-ChS)-based nanostructured lipid carriers (NLCs) including dexamethasone (DEX) were designed and constructed. APBA-ChS, which is present on the surface of DEX-NLC and contains the boronic acid group, can form complex with sialic acids in the ocular mucin, hence leading to prolonged precorneal retention. This affinity between boronic acid and sialic acids was used to develop a mucoadhesive drug delivery system. The developed mucoadhesive drug carrier demonstrated prolonged retention time and alleviation of dry eye syndrome. APBA-ChS-based NLC may be considered a promising ocular drug delivery system for treating anterior eye diseases.

Functional intercalated nanocomposites with chitosan-glutathione-glycylsarcosine and layered double hydroxides for topical ocular drug delivery

Background

To enhance ocular bioavailability, the traditional strategies have focused on prolonging precorneal retention and improving corneal permeability by nano-carriers with positive charge, thiolated polymer, absorption enhancer and so on. Glycylsarcosine (GS) as an active target ligand of the peptide tranpsporter-1 (PepT-1), could specific interact with the PepT-1 on the cornea and guide the nanoparticles to the treating site.

Purpose

The objective of the study was to explore the active targeting intercalated nanocomposites based on chitosan-glutathione-glycylsarcosine (CG-GS) and layered double hydroxides (LDH) as novel carriers for the treatment of mid-posterior diseases.

Materials and methods

CG-GS-LDH intercalated nanocomposites were prepared by the coprecipitation hydrothermal method. In vivo precorneal retention study, ex vivo fluorescence images, in vivo experiment for distribution and irritation were studied in rabbits. The cytotoxicity and cellular uptake were studied in human corneal epithelial primary cells (HCEpiC).

Results

CG-GS-LDH nanocomposites were prepared successfully and characterized by FTIR and XRD. Experiments with rabbits showed longer precorneal retention and higher distribution of fluorescence probe/model drug. In vitro cytological study, CG-GS-LDH nanocomposites exhibited enhanced cellular uptake compared to pure drug solution. Furthermore, the investigation of cellular uptake mechanisms demonstrated that both the active transport by PepT-1 and clathrin-mediated endocytosis were involved in the internalization of CG-GS-LDH intercalated nanocomposites. An ocular irritation study and a cytotoxicity test indicated that these nanocomposites produced no significant irritant effects.

Conclusions

The active targeting intercalated nanocomposites could have great potential for topical ocular drug delivery due to the capacity for prolonging the retention on the ocular surface, enhancing the drug permeability through the cornea, and efficiently delivering the drug to the targeted site.

Preparation and Characterization of Mucoadhesive Nanoparticles for Enhancing Cellular Uptake of Coenzyme Q10

The mucoadhesive nanoparticles (NPs) for oral delivery of coenzyme Q10 (CoQ10) were prepared using natural mucoadhesive polysaccharides, chitosan (CS), and dextran sulfate sodium salt (DS) in order to improve the solubility, cellular uptake, and thermo- and photostability of CoQ10. CoQ10-loaded NPs were prepared in the range of 340-450 nm with an entrapment efficiency of 60-98%. The mucoadhesiveness and cellular uptake of NPs were evaluated by measuring the amount of mucin adsorbed on NPs and CoQ10 absorbed in Caco-2 cells, respectively. CS/DS NPs had higher mucoadhesive strength than CS/sodium triphosphate pentabasic NPs (control group). Moreover, the solubility, cellular uptake, thermo- and photostability of CS/DS NPs were significantly improved compared with non-nanoencapsulated free CoQ10. Particularly, CS/DS NPs prepared with 0.5 mg/mL of CS and DS produced the highest mucoadhesiveness, solubility, cellular uptake, and cellular antioxidant activity. Thus, mucoadhesive CS/DS NPs may be an effective oral delivery platform for improving bioavailability of CoQ10.

Chitosan–PVA monodisperse millimeter-sized spheres prepared by electrospraying reduce the thromboembolic risk in hemorrhage control

Chitosan–PVA monodisperse millimeter-sized spheres are efficient in hemorrhage control and also reduce the risk of thromboembolic complication.