Investigation of inclusion complex of miconazole nitrate with β-cyclodextrin

Mucoadhesive polymers: Design of S-protected thiolated cyclodextrin-based hydrogels

AIM

This study aims to design chemically crosslinked thiolated cyclodextrin-based hydrogels and to evaluate their mucoadhesive properties via mucosal residence time studies on porcine small intestinal mucosa and on porcine buccal mucosa.

METHODS

Free thiol groups of heptakis(6-deoxy-6-thio)-β-cyclodextrin (β-CD-SH) were S-protected with 2-mercaptoethanesulfonic acid (MESNA) followed by crosslinking with citric acid. Cytotoxicity was assessed by hemolysis as well as resazurin assay. Hydrogels were characterized by their rheological and mucoadhesive properties. Ritonavir was employed as model drug for in vitro release studies from these hydrogels.

RESULTS

The structure of S-protected β-CD-SH was confirmed by IR and 1H NMR spectroscopy. Degree of thiolation was 390 ± 7 µmol/g. Hydrogels based on native β-CD showed hemolysis of 12.5 ± 2.5 % and 13.6 ± 2.7 % within 1 and 3 h, whereas hemolysis of just 3.5 ± 2.8 % and 3.9 ± 3.0 % was observed for the S-protected thiolated CD hydrogels, respectively. Both native and S-protected thiolated hydrogels showed minor cytotoxicity on Caco-2 cells. Rheological investigations of S-protected thiolated β-CD-based hydrogel (16.2 % m/v) showed an up to 13-fold increase in viscosity in contrast to the corresponding native β-CD-based hydrogel. Mucosal residence time studies showed that thiolated β-CD-based hydrogel is removed to a 16.6- and 2.4-fold lower extent from porcine small intestinal mucosa and porcine buccal mucosa in comparision to the native β-CD-based hydrogel, respectively. Furthermore, a sustained release of ritonavir from S-protected thiolated β-CD-based hydrogels was observed.

CONCLUSION

Because of their comparatively high mucoadhesive and release-controlling properties, S-protected thiolated β-CD-based hydrogels might be promising systems for mucosal drug delivery.

Development and Characterization of Thiolated Cyclodextrin-Based Nanoparticles for Topical Delivery of Minoxidil

PURPOSE

The aim of this research was to prepare adhesive nanoparticles for the topical application of Minoxidil (MXD).

METHODS

Thiolated β-CDs were prepared via conjugation of cysteamine with oxidized CDs. MXD was encapsulated within thiolated and unmodified β-CDs. Ionic gelation method was used to prepare nanoparticles (Thio-NP and blank NP) of CDs with chitosan. Nanoparticles were analyzed for size and zetapotential. Inclusion complexes were characterized via FTIR. Drug dissolution studies were carried out. An in vitro adhesion study over human hair was performed. An in vivo skin irritation study was performed. Ex vivo drug uptake was evaluated by using a Franz diffusion cell.

RESULTS

Thiolated β-CDs presented 1804.68 ± 25 μmol/g thiol groups and 902.34 ± 25 μmol/g disulfide bonds. Nanoparticles displayed particle sizes within a range of 231 ± 07 nm to 354 ± 13 nm. The zeta potential was in the range of -8.1 ± 02 mV, +16.0 ± 05 mV. FTIR analyses confirmed no interaction between the excipients and drug. Delayed drug release was observed from Thio-NP. Thio-NP retained over hair surfaces for a significantly longer time. Similarly, drug retention was significantly improved. Thio-NP displayed no irritation over rabbit skin.

CONCLUSION

Owing to the above results, nanoparticles developed with MXD-loaded thiolated β-CDs might be a potential drug delivery system for topical scalp diseases.

A promising synthetic citric crosslinked β-cyclodextrin derivative for antifungal drugs: Solubilization, cytotoxicity, and antifungal activity

Effective antifungal therapy for the treatment of fungal keratitis requires a high drug concentration at the corneal surface. However, the use of natural β-cyclodextrin (βCD) in the preparation of aqueous eye drop formulations for treating fungal keratitis is limited by its low aqueous solubility. Here, we synthesized water-soluble anionic βCD derivatives capable of forming water-soluble complexes and evaluated the solubility, cytotoxicity, and antifungal efficacy of drug prepared using the βCD derivative. To achieve this, a citric acid crosslinked βCD (polyCTR-βCD) was successfully synthesized, and the aqueous solubilities of selected antifungal drugs, including voriconazole, miconazole (MCZ), itraconazole, and amphotericin B, in polyCTR-βCD and analogous βCD solutions were evaluated. Among the drugs tested, complexation of MCZ with polyCTR-βCD (MCZ/polyCTR-βCD) increased MCZ aqueous solubility by 95-fold compared with that of MCZ/βCD. The inclusion complex formation of MCZ/βCD and MCZ/polyCTR-βCD was confirmed by spectroscopic techniques. Additionally, the nanoaggregates of saturated MCZ/polyCTR-βCD and MCZ/βCD solutions were observed using dynamic light scattering and transmission electron microscopy. Moreover, MCZ/polyCTR-βCD solution exhibited good mucoadhesion, sustained drug release, and high drug permeation of porcine cornea ex vivo. Hen's Egg test-chorioallantoic membrane assay and cell viability study using Statens Seruminstitut Rabbit Cornea cell line showed that both MCZ/polyCTR-βCD and MCZ/βCD exhibited no sign of irritation and non-toxic to cell line. Additionally, antifungal activity evaluation demonstrated that all isolated fungi, including Candida albicans, Aspergillus flavus, and Fusarium solani, were susceptible to MCZ/polyCTR-βCD. Overall, the results showed that polyCTR-βCD could be a promising nanocarrier for the ocular delivery of MCZ.

Thiolated cyclodextrins: A comparative study of their mucoadhesive properties

AIM

The aim of this study was the comparison of the mucoadhesive properties of nonionic, negatively, and positively charged thiolated cyclodextrins (CDs), including α-, β-, and γ-CDs of low and high degree of thiolation.

METHODS

Native α-, β-, and γ-CDs were thiolated with phosphorous pentasulfide in sulfolane (CD-SH) (i), via reductive amination with cysteamine after oxidative ring opening (CD-Cya) (ii), and via esterification with mercaptosuccinic acid (CD-MSA) (iii). These thiolated CDs were characterized via ¹H NMR and Ellman's test. Cytotoxicity was determined via resazurin and hemolysis assay. Mucoadhesive properties were evaluated via rheological studies with freshly isolated porcine mucus, as well as residence time studies on porcine small intestinal mucosa.

RESULTS

The structure of thiolated CDs was confirmed via ¹H NMR. The degree of thiolation was in the range of 594-1034 µmol/g for low and 1360-3379 µmol/g for high CD-SH, whereas thiolated CD-Cya and thiolated CD-MSA exhibited a degree of thiolation of 1142-3242 µmol/g and 243-1227 µmol/g, respectively. Just cationic CDs showed cytotoxicity. Nonionic highly thiolated α-CD-SH, α-CD-Cya, and α-CD-MSA exhibited with mucus 5.6-, 15.7- and 2.8-fold improved dynamic viscosity, while improvement was 7.7-, 6.1-, and 5.4-fold for the corresponding thiolated β-CDs and 12.3-, 15.4- and 17.8-fold for the corresponding thiolated γ-CDs compared with native CDs, respectively. A prolonged mucosal residence time following the rank order γ > β > α was observed for all thiolated CDs, whereby γ-CD-Cya, nonionic highly thiolated β-CD-SH and α-CD-Cya showed the highest mucoadhesive properties.

CONCLUSION

A high degree of thiolation and the introduction of cationic charges are mainly responsible for high mucoadhesive properties of CDs.

A Current Overview of Cyclodextrin-Based Nanocarriers for Enhanced Antifungal Delivery

Fungal infections are an extremely serious health problem, particularly in patients with compromised immune systems. Most antifungal agents have low aqueous solubility, which may hamper their bioavailability. Their complexation with cyclodextrins (CDs) could increase the solubility of antifungals, facilitating their antifungal efficacy. Nanoparticulate systems are promising carriers for antifungal delivery due to their ability to overcome the drawbacks of conventional dosage forms. CD-based nanocarriers could form beneficial combinations of CDs and nanoparticulate platforms. These systems have synergistic or additive effects regarding improved drug loading, enhanced chemical stability, and enhanced drug permeation through membranes, thereby increasing the bioavailability of drugs. Here, an application of CD in antifungal drug formulations is reviewed. CD-based nanocarriers, such as nanoparticles, liposomes, nanoemulsions, nanofibers, and in situ gels, enhancing antifungal activity in a controlled-release manner and possessing good toxicological profiles, are described. Additionally, the examples of current, updated CD-based nanocarriers loaded with antifungal drugs for delivery by various routes of administration are discussed and summarized.

Cyclodextrin-based Pickering emulsions: functional properties and drug delivery applications

Cyclodextrins (CDs) are biocompatible, cyclic oligosaccharides that are widely used in various industrial applications and have intriguing interfacial science properties. While CD molecules typically have low surface activity, they are capable of stabilizing emulsions by inclusion complexation of oil-phase components at the oil/water interface, which results in Pickering emulsion formation. Such surfactant-free formulations have gained considerable attention in recent years, owing to their enhanced physical stability, improved tolerability, and superior environmental compatibility compared to conventional, surfactant-based emulsions. In this review, we critically describe the latest insights into the molecular mechanisms involved in CD stabilization of Pickering emulsions, including covering practical aspects such as methods to prepare CD-based Pickering emulsions, lipid encapsulation, and relevant stability issues. In addition, the rheological and textural features of CD-based Pickering emulsions are discussed and particular attention is focused on promising examples for drug delivery, cosmetic, and nutraceutical applications. The functionality of currently developed CD-based Pickering emulsions is also summarised, including examples such as antifungal uses, and we close by discussing emerging possibilities to utilize the molecular encapsulation of CD-based emulsions for translational medicine applications in the antiviral and antibacterial spaces.

Characterization of Inclusion Complexes between Miconazole and Different Cyclodextrin Derivatives

Objective: Miconazole, an imidazole antifungal derivative, is a very hydrophobic compound, a major drawback in obtaining topical pharmaceutical formulations with optimal bioavailability. Cyclodextrins (CDs) may increase local drug delivery by enhancing the drug release and/or permeation. The aim of the study is the characterization of inclusion complexes between miconazole and different CD derivatives.

Methods: Several CD derivatives were tested in the experiments. The binary systems between miconazole and different CDs were prepared in 1:1 molar ratios by physical-mixture and kneading methods. Differential scanning calorimetry (DSC) and Fourier transformed-infrared spectroscopy (FT-IR) methods were used to characterize solid state interactions between miconazole and CDs in their binary systems.

Results: The FT-IR analysis suggests the formation of a new solid phase, indicating a molecular interaction between the components. The DSC analysis sustains the hypothesis of formation of partial inclusion complexes between miconazole nitrate and CD.

Conclusion: The thermic behaviour of the complexes depends both on the preparation method and the composition of the products.

Thiolated Cyclodextrin: Development of a Mucoadhesive Vaginal Delivery System for Acyclovir

The objective of this study was the development of a mucoadhesive vaginal delivery system for acyclovir (Acv). Sodium-per-iodate (NaIO4) was used to introduce aldehyde substructures into beta-cyclodextrin (β-CD) by oxidative cleavage of vicinal diol bonds. Cysteamine was covalently attached to β-CD-CHO via reductive amination. Ellman's reagent was utilized for quantification of free thiol groups attached and resazurin assay was used for cytotoxicity studies. Mucoadhesive properties were evaluated on porcine vaginal mucosa in comparison to intestinal mucosa. Quantification of thiol groups revealed 851.84 ± 107, 1040.44 ± 132, and 1563.72 ± 171 μmol/g of free thiol groups attached to the β-CD-SH851, β-CD-SH1040, and β-CD-SH1563, respectively. β-CD-SH derivatives at concentrations of 0.5% (m/v) did not show significant reduction of viability of Caco-2 cells within 24 h. Furthermore, water solubility of β-CD-SH1563 was improved 7.6-fold in comparison to unmodified β-CD. β-CD-SH851, β-CD-SH1040, and β-CD-SH1563 showed 5.84-, 15.95-, and 17.14-fold improved mucoadhesive properties on porcine vaginal mucosa and 3-, 12.47-, and 32.13-fold on porcine intestinal mucosa, respectively. Inclusion complex of Acv with β-CD-SH1563 resulted in significantly improved drug dissolution. According to the results, β-CD-SH derivatives might be promising new tools for local vaginal delivery of Acv.

Preparation and characterization of inclusion complexes formed between baicalein and cyclodextrins

This study investigates the solubility of baicalein (Ba) with the addition of modified cyclodextrins using phase solubility method. The solubility of Ba in the presence of natural (α-, β-, and γ-) cyclodextrins and its derivatives, namely, hydroxypropyl-β-cyclodextrin (HP-β-CD) and (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), was higher than that of free Ba. In particular, the stability constant of inclusion complex with DM-β-CD was 13672.67l mol(-1), which was the highest among the examined cyclodextrins. The inclusion complexes of Ba and DM-β-CD were prepared via freeze-drying method, which were both characterized in the solution and solid state by UV-vis spectroscopy, differential scanning calorimetry (DSC), proton nuclear magnetic resonance ((1)H NMR), scanning electron microscopy (SEM), and X-ray powder diffractometry (XRPD). The UV-vis, DSC, (1)H NMR, SEM, and XRPD results proved the formation of inclusion complex between Ba and DM-β-CD. Furthermore, the dissolution rate and thermal stability of the inclusion complex were significantly enhanced compared with the pure drug. Therefore, using DM-β-CD can effectively improve the solubility and thermal stability of free Ba, which is a promising approach to promote its clinical application.

Development of formulations to improve the controlled-release of linalool to be applied as an insecticide

In recent studies, insecticide activity of a monoterpene, linalool, has been demonstrated, finding, however, limitations in application because of its rapid volatilization. Potential effectiveness of microcapsules and effects of various types of matrices on its stability as controlled-release systems for the slow volatilization of linalool to be applied as insecticide were evaluated. To study controlled-release, linalool was entrapped into microcapsules, inclusion complexes, and beads, obtained by different methods, inverse gelation (IG1, IG2, IG3, IG4, and IG5), oil-emulsion-entrapment (OEE), interfacial coacervation (INCO), and chemical precipitation (Cyc5 and Cyc10). The encapsulation yield turned out to be different for each formulation, reaching the maximum retention for IG1 and OEE. In controlled-release, OEE followed by INCO presented a long time necessary for releasing as a result of the presence of glycerol or chitosan. These results pointed out remarkable differences in the release behavior of linalool depending on matrix composition and the method of encapsulation.

Functionalization of acrylic hydrogels with alpha-, beta- or gamma-cyclodextrin modulates protein adsorption and antifungal delivery

Poly(hydroxyethyl methacrylate) (pHEMA) hydrogels were functionalized with pendant alpha-, beta- and gamma-cyclodextrins (CD) with the aim of improving the biocompatibility and increasing the ability to host drug molecules. Pendant alpha-, beta- and gamma-CDs did not affect swelling of the hydrogels but slightly decreased the water contact angle. Protein deposition was notably dependent on the nature of the CD, due to their different affinities for hydrophobic moieties of proteins. Lysozyme and albumin sorption was hindered by gamma-CD. Functionalization with beta-CD also reduced protein sorption, although less so, while alpha-CD decreased lysozyme deposition but enhanced albumin sorption compared with control pHEMA hydrogels. Loading of the hydrogels with miconazole was carried out by immersion in drug suspension followed by autoclaving. Functionalization with gamma-CD doubled the affinity of the network for the drug and resulted in the highest amount loaded (up to 170 mgg(-1)). Sustained delivery was observed for several days. Some miconazole-loaded hydrogels completely prevented Candida albicans biofilm formation as assayed in an in vitro microbiological test.