Effect of citrate spacer on mucoadhesive properties of a novel water-soluble cationic β-cyclodextrin-conjugated chitosan

Cyclodextrins and derivatives in drug delivery: New developments, relevant clinical trials, and advanced products

Cyclodextrins (CD) and derivatives are functional excipients that can improve the bioavailability of numerous drugs. Because of their drug solubility improving properties they are used in many pharmaceutical products. Furthermore, the stability of small molecular drugs can be improved by the incorporation in CDs and an unpleasant taste and smell can be masked. In addition to well-established CD derivatives including hydroxypropyl-β-CD, hydroxypropyl-γ-CD, methylated- β-CD and sulfobutylated- β-CD, there are promising new derivatives in development. In particular, CD-based polyrotaxanes exhibiting cellular uptake enhancing properties, CD-polymer conjugates providing sustained drug release, enhanced cellular uptake, and mucoadhesive properties, and thiolated CDs showing mucoadhesive, in situ gelling, as well as permeation and cellular uptake enhancing properties will likely result in innovative new drug delivery systems. Relevant clinical trials showed various new applications of CDs such as the formation of CD-based nanoparticles, stabilizing properties for protein drugs or the development of ready-to-use injection systems. Advanced products are making use of various benefical properties of CDs at the same time. Within this review we provide an overview on these recent developments and take an outlook on how this class of excipients will further shape the landscape of drug delivery.

The Use of Cyclodextrin Inclusion Complexes to Increase the Solubility and Pharmacokinetic Profile of Albendazole

Albendazole is the preferred deworming drug and has strong insecticidal effects on human and animal helminth parasites, showing remarkable activity against hepatocellular carcinoma and colorectal cancer cells. However, it is classified as being in class II in the Biopharmaceutics Classification System due to its poor water solubility (0.2 mg/L) and high permeability, which make the clinical application of albendazole impractical. Through complexation with methyl-β-cyclodextrin, as the best result so far, albendazole's water solubility was increased by 150,000 times, and albendazole could be 90% released during the first 10 min. In an in vivo pharmacokinetic study, the Cmax and Tmax of the active metabolized sulfoxide were changed from 2.81 µg/mL at 3 h to 10.2 µg/mL at 6 h and the AUC0-48 was increased from 50.72 h⁎μg/mL to 119.95 h⁎μg/mL, indicating that the inclusion complex obtained can be used as a new oral therapeutic anti-anthelmintic and anti-tumor agent formulation.

Electrospun nanofibers using β-cyclodextrin grafted chitosan macromolecules loaded with indomethacin as an innovative drug delivery system

Electrospun nanofibers, as an innovative drug delivery system, provide selective, effective, and safe drug release. The present study aimed to fabricate nanofibers based on β-cyclodextrin grafted chitosan (β-CD-g-CS) macromolecules with incorporated drug via the blend electrospinning technique. The grafting of β-CD onto chitosan (CS) was confirmed by FT-IR, ¹H NMR, TGA, XRD, and EDX analysis. Indomethacin was encapsulated in the β-CD-g-CS matrix as blend nanofibers using electrospinning in presence of polyvinyl alcohol (PVA). The SEM images revealed nanofibers with diameters at the nanoscale. The unique features of β-CD-g-CS/PVA as drug delivery system were investigated using indomethacin as a model drug molecule. Controlled release of indomethacin from nanofibers was studied in PBS solution by measuring the absorbance by UV-Vis spectrophotometer. The drug release profile exhibited that the rate of drug release can be tailored by polymer type and changing the drug/polymer ratio. The physicomechanical properties of the developed nanofibers were analyzed by tensile strength and water contact angle. The results demonstrated that β-CD-g-CS revealed enhanced wettability as well as favorable physicomechanical properties. In addition, the growth rate of the L929 cells on the CS and β-CD-g-CS nanofibers was not significantly inhibited and even improved cell proliferation. These findings indicated that β-CD-g-CS nanofibers could be appropriate as a smart drug delivery system for sustained release of indomethacin as an anti-inflammatory medicine in the wound healing and tissue engineering approaches in orthopedic applications.

Self-Assembly of Amphiphilic Compounds as a Versatile Tool for Construction of Nanoscale Drug Carriers

This review focuses on synthetic and natural amphiphilic systems prepared from straight-chain and macrocyclic compounds capable of self-assembly with the formation of nanoscale aggregates of different morphology and their application as drug carriers. Since numerous biological species (lipid membrane, bacterial cell wall, mucous membrane, corneal epithelium, biopolymers, e.g., proteins, nucleic acids) bear negatively charged fragments, much attention is paid to cationic carriers providing high affinity for encapsulated drugs to targeted cells. First part of the review is devoted to self-assembling and functional properties of surfactant systems, with special attention focusing on cationic amphiphiles, including those bearing natural or cleavable fragments. Further, lipid formulations, especially liposomes, are discussed in terms of their fabrication and application for intracellular drug delivery. This section highlights several features of these carriers, including noncovalent modification of lipid formulations by cationic surfactants, pH-responsive properties, endosomal escape, etc. Third part of the review deals with nanocarriers based on macrocyclic compounds, with such important characteristics as mucoadhesive properties emphasized. In this section, different combinations of cyclodextrin platform conjugated with polymers is considered as drug delivery systems with synergetic effect that improves solubility, targeting and biocompatibility of formulations.

Citric acid-crosslinked β-cyclodextrin supported zinc peroxide as a biocompatible H2O2 scavenger

The aim of the present study was to evaluate the H₂O₂ scavenging activity of the ZnO₂/β-CD as a biocompatible composite. Zinc peroxide was prepared via sonochemical approach. To synthesize a green composite, β-cyclodextrin was modified by citric acid (CA) and reacted with ZnO₂ under ultrasonic irradiation. The prepared samples were characterized using XRD, SEM, TGA and FTIR analytical techniques. XRD analysis exhibited a typical pattern of ZnO₂ and demonstrated the presence of citric acid and β-cyclodextrin in composite. The results of the catalytic assay showed that the ZnO₂/CA-βCD composite displayed stronger capability to decompose H₂O₂ in comparison to ZnO₂ particles (about seven times). It was attributed to increased adsorption capacity and solubility of composite due to the presence of citric acid and β-cyclodextrin. MTT assay studies confirmed the non-cytotoxic nature of ZnO₂ particles and ZnO₂/CA-βCD composite.

A water-soluble, mucoadhesive quaternary ammonium chitosan-methyl-β-cyclodextrin conjugate forming inclusion complexes with dexamethasone

The ocular bioavailability of lipophilic drugs, such as dexamethasone, depends on both drug water solubility and mucoadhesion/permeation. Cyclodextrins and chitosan are frequently employed to either improve drug solubility or prolong drug contact onto mucosae, respectively. Although the covalent conjugation of cyclodextrin and chitosan brings to mucoadhesive drug complexes, their water solubility is restricted to acidic pHs. This paper describes a straightforward grafting of methyl-β-cyclodextrin (MCD) on quaternary ammonium chitosan (QA-Ch60), mediated by hexamethylene diisocyanate. The resulting product is a water-soluble chitosan derivative, having a 10-atom long spacer between the quaternized chitosan and the cyclodextrin. The derivative is capable of complexing the model drug dexamethasone and stable complexes were also observed for the lyophilized products. Furthermore, the conjugate preserves the mucoadhesive properties typical of quaternized chitosan and its safety as solubilizing excipient for ophthalmic applications was preliminary assessed by in vitro cytotoxicity evaluations. Taken as a whole, the observed features appear promising for future processing of the developed product into 3D solid forms, such as controlled drug delivery systems, films or drug eluting medical devices.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.

Chitosan and Its Derivatives for Application in Mucoadhesive Drug Delivery Systems

Mucoadhesive drug delivery systems are desirable as they can increase the residence time of drugs at the site of absorption/action, provide sustained drug release and minimize the degradation of drugs in various body sites. Chitosan is a cationic polysaccharide that exhibits mucoadhesive properties and it has been widely used in the design of mucoadhesive dosage forms. However, its limited mucoadhesive strength and limited water-solubility at neutral and basic pHs are considered as two major drawbacks of its use. Chemical modification of chitosan has been exploited to tackle these two issues. In this review, we highlight the up-to-date studies involving the synthetic approaches and description of mucoadhesive properties of chitosan and chitosan derivatives. These derivatives include trimethyl chitosan, carboxymethyl chitosan, thiolated chitosan, chitosan-enzyme inhibitors, chitosan-ethylenediaminetetraacetic acid (chitosan-EDTA), half-acetylated chitosan, acrylated chitosan, glycol chitosan, chitosan-catechol, methyl pyrrolidinone-chitosan, cyclodextrin-chitosan and oleoyl-quaternised chitosan. We have particularly focused on the effect of chemical derivatization on the mucoadhesive properties of chitosan. Additionally, other important properties including water-solubility, stability, controlled release, permeation enhancing effect, and in vivo performance are also described.

Surface modification of nanostructure lipid carrier (NLC) by oleoyl-quaternized-chitosan as a mucoadhesive nanocarrier

A nanostructure lipid carrier (NLC) composed of solid, and liquid lipid as a core has been developed as a delivery system for hydrophobic drug molecules. The aim of this research was to fabricate an oleoyl-quaternized-chitosan (CS)-coated NLC, where the mucoadhesive property of nanoparticles is enhanced for more efficient drug delivery. NLC loaded with alpha-mangostin (AP), a model hydrophobic drug, were fabricated using a high pressure homogenization process and subsequently coated with CS. The fabricated nanoparticles showed particle sizes in the range of 200-400nm, with low polydispersity, high physical stability and excellent encapsulation efficiency (EE>90%). Additionally, in vitro viability, cytotoxicity and ability of NLC and CS-NLC to affect apoptosis in carcinoma Caco-2 cells were determined using the Triplex assay. Gene expressiom analysis were performed using quantitative reverse transcription Polymerase Chain Reaction (RT-qPCR). Moreover, in vivo toxicological testing of NLCs was conducted in zebrafish embryos. Results indicated that CS-NLC provieded high cytotoxicity than NLC itself. In the case of AP loaded nanoparticles, NLC loaded with AP (AP-NLC), and CS-NLC loaded with AP (CS-AP-NLC) exhibited higher cytotoxicity to Caco-2 over Hela cells. These results indicate that CS-NLC shows enhanced cellular uptake but increased cytotoxicity characteristics over NLC and therefore careful optimization of dosage and loading levels in CS-NLC is needed to allow cancer cell targeting, and for exploiting the potential of these systems in cancer therapy.

A vision for cyclodextrin nanoparticles in drug delivery systems and pharmaceutical applications

Cyclodextrins (CDs) have brought a revolution in the pharmaceutical field over the last decade. Natural and modified CDs (α-CD and β-CD) have been studied and some have gained US FDA approval or achieved 'Generally Regarded as Safe' (GRAS) status. Another characteristic of CDs is the ease with which they can be induced to form supramolecular structures for its use in drug delivery. CDs, grafted or crosslinked with polymers, are now being developed into 'smart' systems for efficient targeted drug delivery, especially for hydrophobic drugs. Amphiphilic CDs have the ability to form nanospheres or nanocapsules via a simple nanoprecipitation technique. This review deals with different types of CDs, and their efficacy, physicochemical properties and transformation into nanoparticles with interesting in vitro and in vivo applications.

Enhanced delivery of daidzein into fibroblasts and neuronal cells with cationic derivatives of gamma-cyclodextrin for the control of cellular glycosaminoglycans

Two cationic derivatives of γ-cyclodextrin (GCD) were synthesized by functionalization with glycidyltrimethylammonium chloride (GTMAC) and ethylenediamine (EDA). Both these derivatives (GCD-GTMAC and GCD-EDA) have been shown to interact strongly with anionic biopolymers, unfractionated heparin (UFH) and mucin, the latter showing their mucoadhesive properties. They form inclusion complexes with daidzein (DAI), an isoflavone displaying a multitude of physiological effects, much more efficiently than the unmodified GCD. It was also shown that the complexes of these GCD derivatives with DAI and Nile Red penetrate human fibroblasts and murine hippocampal neuronal cells indicating that cationic GCD derivatives can be considered as potential delivery systems for isoflavones and other poorly water soluble compounds. Moreover, it was found that DAI delivered in cationic GCD complexes decreased the level of the cellular glycosaminoglycans (GAGs) in normal fibroblasts suggesting their possible application in the control of GAGs in mucopolysaccharidoses, lysosomal storage diseases caused by pathological accumulation of GAGs in the cells.

The Synthesis of the Locating Substitution Derivatives of Chitosan by Click Reaction at the 6-Position of Chitin

A novel method to prepare the macrocyclic compound locating substitution derivatives of chitosan was investigated, by using cyclodextrin as the model of macrocyclic compound. The method combines the advantages of activated 6-OH of chitin and high efficiency of click reaction. Chitin C6-OHp-toluenesulfonate (CTN-6-OTs) was generated and subsequently transferred to chitin C6-N3via nucleophilic substitution. Afterwards,β-cyclodextrin was immobilized at 6-OH of chitin via click reaction to afford CTN-6-CD. Ultimately, CTS-6-CD was obtained by removing the acetyl group of chitin unit. The structures and properties of these products were characterized by FTIR, TG, and XRD, respectively. It was found that CTN-6-CD synthesized at the optimum conditions has an immobilized loading of1.6126×10-4 mol/g and that of the corresponding CTS-6-CD, generated by removal of the acetyl group, was1.6891×10-4 mol/g.

A comparison of spacer on water-soluble cyclodextrin grafted chitosan inclusion complex as carrier of eugenol to mucosae

In this study two types of water-soluble βCD grafted chitosan were synthesized and compared based on similar degree of N-substitution of βCD moiety; QCD23-g-CS contained methylene spacer and QCDCA22-g-CS contained citric acid spacer. The QCD23-g-CS demonstrated greater eugenol (EG) encapsulation efficiency than that of QCDCA22-g-CS. The micelle-like assemblies of QCD23-g-CS led to slower release of EG while it did not observe in case of QCDCA22-g-CS. It was found that EG could absorb on chitosan backbone according to in silico modeling. Cytotoxicity of both derivatives against buccal mucosa cell is concentration-dependent. The QCDCA22-g-CS demonstrated stronger mucoadhesive response than that of QCD23-g-CS, due to hydrogen bonding according to mucin particle and SPR methods. Our results revealed that the spacer on both derivatives played an important role on binding affinity with EG, releasing profile and mucoadhesive property. These derivatives could be considered as promising carriers for mucosal delivery system.

Cationic polymers and their therapeutic potential

The last decade has witnessed enormous research focused on cationic polymers. Cationic polymers are the subject of intense research as non-viral gene delivery systems, due to their flexible properties, facile synthesis, robustness and proven gene delivery efficiency. Here, we review the most recent scientific advances in cationic polymers and their derivatives not only for gene delivery purposes but also for various alternative therapeutic applications. An overview of the synthesis and preparation of cationic polymers is provided along with their inherent bioactive and intrinsic therapeutic potential. In addition, cationic polymer based biomedical materials are covered. Major progress in the fields of drug and gene delivery as well as tissue engineering applications is summarized in the present review.