Self-assembly Characterization of the β-Cyclodextrin and Hydrochlorothiazide System: NMR, Phase Solubility, ITC and QELS

Coumarin/β-Cyclodextrin Inclusion Complexes Promote Acceleration and Improvement of Wound Healing

Coumarins have great pharmacotherapeutic potential, presenting several biological and pharmaceutical applications, like antibiotic, fungicidal, anti-inflammatory, anticancer, anti-HIV, and healing activities, among others. These molecules are practically insoluble in water, and for biological applications, it became necessary to complex them with cyclodextrins (CDs), which influence their bioavailability in the target organism. In this work, we studied two coumarins, and it was possible to conclude that there were structural differences between 4,7-dimethyl-2H-chromen-2-one (DMC) and 7-methoxy-4-methyl-2H-chromen-2-one (MMC)/β-CD that were solubilized in ethanol, frozen, and lyophilized (FL) and the mechanical mixtures (MM). In addition, the inclusion complex formation improved the solubility of DMC and MMC in an aqueous medium. According to the data, the inclusion complexes were formed and are more stable at a molar ratio of 2:1 coumarin/β-CD, and hydrogen bonds along with π-π stacking interactions are responsible for the better stability, especially for (MMC)2@β-CD. In vivo wound healing studies in mice showed faster re-epithelialization and the best deposition of collagen with the (DMC)2@β-CD (FL) and (MMC)2@β-CD (FL) inclusion complexes, demonstrating clearly that they have potential in wound repair. Therefore, (DMC)2@β-CD (FL) deserves great attention because it presented excellent results, reducing the granulation tissue and mast cell density and improving collagen remodeling. Finally, the protein binding studies suggested that the anti-inflammatory activities might exert their biological function through the inhibition of MEK, providing the possibility of development of new MEK inhibitors.

Development of pediatric orally disintegrating mini-tablets containing atomoxetine hydrochloride-β-cyclodextrin inclusion complex using experimental design

OBJECTIVE

The aim of the study was to develop and evaluate characteristics of orally disintegrating mini-tablet (ODMT) formulations including atomoxetine hydrochloride (ATO)/β-cyclodextrin (β-CD) inclusion complex for pediatric therapy of attention deficit and hyperactivity disorder (ADHD).

METHODS

Design of experiment approach was used to develop ODMTs. The ODMTs were compressed using direct compression method with two different superdisintegrants (Parteck ODT^® and Ac-Di-Sol^®) and characterized with quality control tests. In vitro dissolution and taste studies were performed.

RESULTS

The hardness and friability values of the optimized three ODMT formulations were determined as 41.7 N, 42.4 N, and 40.8 N and 0.32%, 0.29%, and 0.42%, respectively. The disintegration time of all the optimized formulations was found to be less than one minute. In addition, dissolution profiles of ATO from optimized ODMTs were determined in four different dissolution media (distilled water, pH 1.2, 6.8, and 7.4) and it was determined that the maximum dissolved ATO amount reached at the end of 20 min.

CONCLUSION

As a conclusion, the novel formulation of ODMTs with ATO/β-CD inclusion complex was successfully developed for pediatric use.

Recovery, reusability and stability studies of beta cyclodextrin used for cholesterol removal from shrimp lipid

Beta cyclodextrin (β-CD) was used for cholesterol removal from shrimp lipid using ethyl acetate and water as solvents. The cholesterol incorporating β-CD complex (β-CD–CL) was collected and β-CD recovery was performed using a β-CD–CL : ethanol mixture (1 : 15 ratio) with the aid of ultrasonication and a water bath at 55 °C for 40 min. Recycled β-CD (R-β-CD) was compared with pure β-CD (P-β-CD) for the reusability of cholesterol removal from shrimp lipid. R-β-CD showed 94% cholesterol removal, while 95% was achieved for P-β-CD. Differential Scanning Calorimetry (DSC) showed a slight decrease in the melting point of R-β-CD. Nevertheless, FTIR and NMR results revealed that functional groups and the proton spectrum of R-β-CD was negligibly altered. Fatty acid contents of treated oil were slightly higher when treated with R-β-CD than those of the lipid subjected to P-β-CD treatment. Reusability of β-CD could be achieved as confirmed by the maintained capacity in cholesterol removal and unaltered structure.

Beta cyclodextrin (β-CD) used for cholesterol removal from shrimp lipid was reused after the cholesterol bound with β-CD was removed. Efficenicy of recycled β-CD was similar to pure β-CD.

Development of a stable oral pediatric solution of hydrochlorothiazide by the combined use of cyclodextrins and hydrophilic polymers

Hydrochlorothiazide (HCT) is widely used in pediatrics for hypertension management. Due to the lack of pediatric commercial forms, community or hospital pharmacies generally prepare HCT extemporaneous pediatric suspensions by dispersing in water a portion of a crushed tablet or the drug powder; however, any dose or stability control is usually done on these preparations. Obtaining stable HCT solutions is very challenging, due to its low water-solubility and pH-dependent degradation. The aim of this work was to develop a stable 2 mg/mL-HCT oral pediatric solution without using co-solvents. Combined use of cyclodextrins (CD) and hydrophilic polymers was exploited to improve poor HCT solubility and stability. HPβCD and SBEβCD were selected, considering their safe toxicological profiles, while PVP resulted the best among the tested polymers. Low PVP concentrations (0.2-1.0%) improved the solubilizing efficiency of both CDs, allowing to reach the prefixed HCT concentration. Different CD-PVP concentrations were used to prepare several 2 mg/mL-HCT solutions in pH 5.5 buffer. The best stability was shown by solutions containing the highest SBEβCD concentration (25 mM), which allowed a 3-months stability at 4 °C. In vivo studies on rats showed that such formulation allowed a more pronounced and more reproducible diuretic effect than the corresponding HCT suspension.

In Vitro Topical Delivery of Chlorhexidine to the Cornea: Enhancement Using Drug-Loaded Contact Lenses and β-Cyclodextrin Complexation, and the Importance of Simulating Tear Irrigation

Microbial keratitis is a severe, sight-threatening condition caused by various pathogens. Eyedrops are the standard delivery modality for treating these disorders; however, blinking reflex, elevated tear production, and nasolacrimal drainage eliminate much of the instilled dose within a few seconds. Therefore, eyedrops must be applied repeatedly for prolonged periods. The present study aimed to probe more effective ocular delivery of chlorhexidine based upon drug-loaded hydrogel contact lenses and β-cyclodextrin (β-CD), while also determining the effect of constant irrigation with simulated tear fluid (STF) in in vitro experiments. Chlorhexidine digluconate (as 0.2 and 2% solutions, β-CD inclusion complexes, and loaded hydrogel contact lenses) were applied to enucleated porcine eyes as single or multiple 10 μL doses, or as drug-loaded contact lenses, with and without β-CD. The corneas were then excised and drug-extracted quantified by high-performance liquid chromatography (HPLC). The effect of constant irrigation by STF was evaluated to test the effect of increased tear production on corneal delivery. Potential antimicrobial activity of the delivered drug was also assessed. Results showed that drug-loaded contact lenses delivered the greatest amount of chlorhexidine into the cornea over a 24 h period, while the eyedrop solution comparator delivered the least. The β-CD significantly enhanced chlorhexidine delivery to the cornea from eyedrop solution, although contact lenses loaded with chlorhexidine-β-CD failed to enhance delivery. β-CD within the hydrogel matrix impeded drug release. Constant irrigation with STF significantly reduced the amount of drug delivered to the cornea in all cases. Chlorhexidine retained antimicrobial activity in all delivery methods. Hydrogel contact lenses loaded with chlorhexidine delivered significantly higher levels to the cornea compared to eyedrops, either multiple hourly doses or a single dose. They also offer reduced application, in particular, to a nonulcerated corneal infection. Finally, the importance of fully accounting for tear production in in vitro ocular delivery experiments was highlighted.

Facile formation of co-amorphous atenolol and hydrochlorothiazide mixtures via cryogenic-milling: Enhanced physical stability, dissolution and pharmacokinetic profile

The development of poorly water-soluble drugs faces the risk of low bioavailability and therapeutic efficacy. The co-amorphous drug delivery system has recently gained considerable interest because it offers an alternative approach to modify properties of poorly water-soluble drugs. Herein, we developed a co-amorphous system of atenolol (ATE) and poorly water-soluble hydrochlorothiazide (HCT) by means of cryogenic milling. The co-administration of ATE and HCT has been reported to show therapeutic advantages for patients with uncomplicated hypertension. The co-amorphous ATE-HCT sample with 1:1 molar ratio showed excellent physical stability, which could be attributed to the formation of strong molecular interactions between ATE and HCT as evidenced by FT-IR spectra. Compared to the pure crystalline form, amorphous form and physical mixture, HCT in the co-amorphous form exhibited the significantly increased intrinsic dissolution rate, as well as the enhanced bioavailability in the pharmacokinetic study. It was found that the enhanced bioavailability of HCT in the co-amorphous formulation was achieved by the synergistic effect of amorphized HCT and the water-soluble coformer ATE. The present study provides an improved approach to implement the combination therapy of ATE and HCT for potential clinical treatments.

Development and in vivo evaluation of an innovative "Hydrochlorothiazide-in Cyclodextrins-in Solid Lipid Nanoparticles" formulation with sustained release and enhanced oral bioavailability for potential hypertension treatment in pediatrics

An innovative pediatric oral formulation of hydrochlorothiazide (HCT) (2mg/mL), endowed with improved bioavailability and sustained release properties and suitable for the hypertension treatment in pediatric patients, was developed by combining the drug-cyclodextrin complexation and the incorporation of the complex into Solid Lipid Nanoparticles (SLN). Precirol^®ATO5-based SLN, with two different surfactants (Pluronic^®F68 and Tween^®80) loaded with the drug as such or as binary system with hydroxypropyl-beta-cyclodextrin (HPβCd) and sulfobutyl-ether-beta-cyclodextrin (SBEβCd) both as physical mixture (P.M.) or coground product (GR), were prepared using the hot high-shear homogenization followed by ultrasonication method. Loading of the drug:HPβCd both as P.M. and GR gave rise to nanoparticle formation, differently from the HCT:SBEβCd ones, with an entrapment efficiency of about 65%. Such SLN formulations showed an improvement of the drug release rate compared both to the drug suspension and to the free drug-loaded SLN. In all cases the SLN containing the GR systems exhibited better performances than the corresponding with P.M. However, the presence of Tween^®80 gave rise to the complete drug release after only 150min, without providing a sustained release, whereas Pluronic^®F68-based SLN containing GR were able to assure a sustained release over the time achieving more than 75% drug released at the end of the test, maintaining a constant 1.8-fold increase respect to simple drug suspension. Pluronic^®F68-based SLN showed a pharmaceutically acceptable stability up to three months. In vivo studies highlighted the effectiveness of such formulations, enabling a concomitant increased diuretic effect and a sustained drug release and, consequently, enhanced HCT oral bioavailability.

Inclusion complexes of hydrochlorothiazide and β-cyclodextrin: Physicochemical characteristics, in vitro and in vivo studies

Hydrochlorothiazide is a thiazide diuretic widely used in clinics to treat arterial hypertension. It is a class IV drug according to the Biopharmaceutical Classification System, that is, it presents low solubility and low permeability and, consequently, low absorption in the gastrointestinal tract. As a strategy to improve stability and biopharmaceutical properties of hydrochlorothiazide, the use of cyclodextrins to produce inclusion complexes, applying different methods, was investigated. In the phase solubility studies, β-cyclodextrin was identified as the cyclodextrin which provided the most promising results in terms of the solubilization of the drug. The thermal analysis verified the interaction between hydrochlorothiazide and β-cyclodextrin, indicating the formation of inclusion complexes, and the thermal stability varied according to the preparation technique. The physicochemical characterization showed that in the inclusion complexes obtained by co-evaporation, kneading followed by freeze-drying and kneading followed by spray-drying the hydrochlorothiazide complexation mostly occurred with different degrees of amorphization and the drug solubility was improved. These three inclusion complexes presented better in vitro characteristics and the inclusion complex obtained by kneading followed by freeze-drying increased the in vivo diuretic activity of the drug accompanied by significant effects on natriuresis, kaliuresis and chloriuresis. The inclusion complex formation was effective in improving the biopharmaceutical properties of hydrochlorothiazide and protecting the drug from hydrolysis. This paper describes an important alternative approach to the development of liquid pharmaceutical formulations to pediatric administration, a real need of the current pharmaceutical market.

Development, characterization, and pharmacodynamic evaluation of hydrochlorothiazide loaded self-nanoemulsifying drug delivery systems

The objective of the current work was to develop optimized self-nanoemulsifying drug delivery systems (SNEDDS) and evaluate their in vitro and in vivo performance. The research comprised various studies which includes solubility studies in various vehicles, pseudoternary phase diagram construction, and preparation and characterization of SNEDDS along with in vitro dissolution and in vivo pharmacodynamic profiling. Based on dissolution profile, a remarkable increase in rate of dissolution was observed in comparison with plain drug and marketed formulation. Optimized SNEDDS formulation was composed of Capmul MCM (19.17% w/w), Tween 80 (57.5% w/w), Transcutol P (12.7% w/w), and HCT (4.17% w/w). In vivo pharmacodynamic evaluation in Wistar rats showed considerable increase in pharmacological effect of HCT by SNEDDS formulation as compared with plain HCT.

Structural and physicochemical aspects of hydrochlorothiazide co-crystals

The drug–drug co-crystal of hydrochlorothiazide with pyrazinamide is a potential candidate for development of hydrochlorothiazide formulations for combinational therapy.

New challenges for pharmaceutical formulations and drug delivery systems characterization using isothermal titration calorimetry

Long viewed as the 'method of choice' for characterizing thermodynamics and stoichiometry of molecular interactions, with high sensitivity, isothermal titration calorimetry (ITC) has been applied to many areas of pharmaceutical analysis. This review highlights ITC employment to measure binding thermodynamics and their use for pharmaceutical formulations and drug delivery system characterization particularly cyclodextrin-guest interactions, investigation of micellar-based systems, polyelectrolytes, nucleic acid interactions with multivalent cations and the optimization of DNA targeting and delivery. Furthermore, the potential of ITC for the characterization of different functionalities carried by nanoparticles as well as their interaction with living systems was outlined.

Study of angiotensin-(1-7) vasoactive peptide and its beta-cyclodextrin inclusion complexes: complete sequence-specific NMR assignments and structural studies

We report the complete sequence-specific hydrogen NMR assignments of vasoactive peptide angiotensin-(1-7) (Ang-(1-7)). Assignments of the majority of the resonances were accomplished by COSY, TOCSY, and ROESY peak coordinates at 400MHz and 600MHz. Long-side-chain amino acid spin system identification was facilitated by long-range coherence transfer experiments (TOCSY). Problems with overlapped resonance signals were solved by analysis of heteronuclear 2D experiments (HSQC and HMBC). Nuclear Overhauser effects (NOE) results were used to probe peptide conformation. We show that the inclusion of the angiotensin-(1-7) tyrosine residue is favored in inclusion complexes with beta-cyclodextrin. QM/MM simulations at the DFTB/UFF level confirm the experimental NMR findings and provide detailed structural information on these compounds in aqueous solution.

Supramolecular self-assembly of β-cyclodextrin: an effective carrier of the antimicrobial agent chlorhexidine

The supramolecular assembly between chlorhexidine and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was characterized using NMR spectroscopy ((1)H, T(1), and ROESY), ESIMS and ITC. NMR data suggest the formation of high ordered complexes. ESIMS and ITC allowed the confirmation of the average stoichiometry as 1:4 and the thermodynamic data, also obtained by ITC, showed that the assembly is strongly stabilized by short distance interactions, but suffers a strong, opposite effect of entropy reduction. The antimicrobial activity of 1:1, 1:2, 1:3, and 1:4 Clx/betaCD molar ratio mixtures was investigated in aqueous solution and after incorporation into mucoadhesive gels. These were used to determine the initial and the long-term antimicrobial activity, respectively, toward Actinobacillus actinomycetemcomitans (A.a.) (Y4-FDC) and Enterococcus faecalis (E.f.) (ATCC 14508) strains. The results showed that A.a. and E.f. were more susceptible to the 1:4 molar ratio mixture in either solution or gel (p<0.05).

A supramolecular complex between proteinases and beta-cyclodextrin that preserves enzymatic activity: physicochemical characterization

BACKGROUND

Cyclodextrins are suitable drug delivery systems because of their ability to subtly modify the physical, chemical, and biological properties of guest molecules through labile interactions by formation of inclusion and/or association complexes. Plant cysteine proteinases from Caricaceae and Bromeliaceae are the subject of therapeutic interest, because of their anti-inflammatory, antitumoral, immunogenic, and wound-healing properties.

METHODS

In this study, we analyzed the association between beta-cyclodextrin (betaCD) and fraction P1G10 containing the bioactive proteinases from Carica candamarcensis, and described the physicochemical nature of the solid-state self-assembled complexes by Fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and nuclear magnetic resonance (NMR), as well as in solution by circular dichroism (CD), isothermal titration calorimetry (ITC), and amidase activity.

RESULTS AND DISCUSSION

The physicochemical analyses suggest the formation of a complex between P1G10 and betaCD. Higher secondary interactions, namely hydrophobic interactions, hydrogen bonding and van der Waals forces were observed at higher P1G10 : betaCD mass ratios. These results provide evidence of the occurrence of strong solid-state supramolecular non-covalent interactions between P1G10 and betaCD. Microcalorimetric analysis demonstrates that complexation results in a favorable enthalpic contribution, as has already been described during formation of similar betaCD inclusion compounds. The amidase activity of the complex shows that the enzyme activity is not readily available at 24 hours after dissolution of the complex in aqueous buffer; the proteinase becomes biologically active by the second day and remains stable until day 16, when a gradual decrease occurs, with basal activity attained by day 29.

CONCLUSION

The reported results underscore the potential for betaCDs as candidates for complexing cysteine proteinases, resulting in supramolecular arrays with sustained proteolytic activity.