Stability of diclofenac sodium in the inclusion complex with beta-cyclodextrin in the solid state

Cyclodextrin in drug delivery: Exploring scaffolds, properties, and cutting-edge applications

Cyclodextrins (CDs) are unique cyclic compounds that can form inclusion complexes via host-guest complexation with a wide range of molecules, thereby altering their physicochemical properties. These molecules offer the formation of inclusion complexes without the formation of covalent bonds, making them suitable for a variety of applications in pharmaceutical and biomedical fields. Due to their supramolecular host-guest properties, CDs are being utilized in the fabrication of biomaterials, metal-organic frameworks, and nano-drug carriers. Additionally, CDs in combination with biomolecules are biocompatible and can deliver nano to macromolecules at the site of drug actions. However, the availability of free hydroxyl groups and a simple crosslinking process for supramolecular fabrication show immense opportunities for researchers in the field of tissue engineering and biomedical applications. In this review article, we have covered the historical development, various types of chemical frameworks, unique chemical and physical properties, and important applications of CDs in drug delivery and biomedical sciences.

Heat Treatment Induced Specified Aggregation Morphology of Metoprolol Tartrate in Poly(ε-caprolactone) Matrix and the Drug Release Variation

Hot-melt blending has been widely used in the pharmaceutical industry to produce drug delivery systems, however, realizing the controlled drug release behavior of a hot-melt blended medicament it is still a tough challenge. In this study, we developed a simple and effective heat treatment method to adjust the drug release behavior, without the addition of any release modifiers. Thin metoprolol tartrate (MPT)/poly(ε-caprolactone) (PCL) tablets were prepared through hot-melt processing, and different morphologies of MPT were obtained by altering processing temperatures and the following heat treatment. MPT particles with different particle sizes were obtained under different processing temperatures, and fibrous crystals of MPT were fabricated during the following heat treatment. Different morphological structures of MPT adjusted the drug diffusion channel when immersed in phosphate-buffered saline (PBS), and various drug release behaviors were approached. After being immersed for 24 h, 7% of the MPT was released from the blend processed at 130 °C, while more than 95% of the MPT were released after the following heat treatment of the same sample. Thus, flexible drug release behaviors were achieved using this simple and effective processing manufacture, which is demonstrated to be of profound importance for biomedical applications.

Encapsulation of echinomycin in cyclodextrin inclusion complexes into liposomes: in vitro anti-proliferative and anti-invasive activity in glioblastoma

Echinomycin, a DNA bis-intercalator peptide, belongs to the family of quinoxaline antibiotics. Echinomycin exhibits potent antitumor and antimicrobial activity. However, it is highly water insoluble and suffers from low bioavailability and unwanted side effects. Therefore, developing new formulations and delivery systems that can enhance echinomycin solubility and therapeutic potency is needed for further clinical application. In this study, echinomycin has been complexed into the hydrophobic cavity of γ-cyclodextrin (γCD) then encapsulated into PEGylated liposomes. The anti-proliferative and anti-invasive effect has been evaluated against U-87 MG glioblastoma cells. Echinomycin-in-γCD inclusion complexes have been characterized by phase solubility assay, TLC, and 1H-NMR. The echinomycin-in-γCD inclusion complexes have been loaded into liposomes using a thin film hydration method to end up with echinomycin-in-γCD-in-liposomes. Drug-loaded liposomes were able to inhibit cell proliferation with IC50 of 1.0 nM. Moreover, echinomycin-in-γCD-in-liposomes were found to inhibit the invasion of U-87 MG cells using the spheroid gel invasion assay. In conclusion, the current work describes for the first time γCD-echinomycin complexes and their encapsulation into PEGylated liposomes.

Remote loading of curcumin-in-modified β-cyclodextrins into liposomes using a transmembrane pH gradient

The current study provides a novel remote loading approach utilizing chemically modified cyclodextrins to incorporate hydrophobic drugs into liposomes.

Cyclodextrins: structure, physicochemical properties and pharmaceutical applications

Since their discovery over 100 years ago cyclodextrins (CDs) have been the subject of numerous scientific publications. In 2016 alone CDs were the subject of over 2200 research articles published in peer-reviewed journals and mentioned in over 2300 patents and patent applications, many of which were on pharmaceutical applications. Natural CDs and their derivatives are used as enabling pharmaceutical excipients that enhance aqueous solubility of poorly soluble drugs, increase drug permeability through biological membranes and improve drug bioavailability. Unlike conventional penetration enhancers, their hydrophilic structure and high molecular weight prevents them from penetrate into lipophilic membranes leaving biological membranes intact. The natural CDs and some of their derivatives have monographs in pharmacopeias and are also commonly used as food additives and in toiletry products. CDs form inclusion complexes with lipophilic moieties of hydrophobic drugs. Furthermore, CDs are able to form non-inclusion complexes and self-assembled aggregates; small and large complex aggregates with micellar-like structures that can enhance drug solubility. Excipients commonly used in pharmaceutical formulations may have additive or inhibiting effect on the CD solubilization. Here various methods used to investigate CD aggregate formation are reviewed as well as techniques that are used to increase the solubilizing effects of CDs; methods that enhance the apparent intrinsic solubility of drugs and/or the complexation efficacy and decrease the amount of CD needed to develop CD-containing pharmaceutical formulations. It will be explained how too much or too little CD can hamper drug bioavailability, and the role of CDs in solid dosage forms and parenteral formulations, and examples given on how CDs can enhance drug delivery after ocular, nasal and pulmonary administration.

Chromatographic and spectroscopic studies on β-cyclodextrin functionalized ionic liquid as chiral stationary phase: Enantioseparation of NSAIDs

Recently, we reported a new chiral stationary phase prepared using β-cyclodextrin functionalized with aromatic ionic liquid which is aimed to enhance the performance of enantioseparation of flavonoids and β-blockers. In this paper, the characteristics and performance of previously prepared chiral stationary phase denoted as β-CD-BIMOTs were compared with the newly synthesized chiral stationary phase denoted as β-CD-DIMOTs. β-CD-DIMOTs were prepared by functionalization of β-cyclodextrin with aliphatic ionic liquid. The obtained β-CD-BIMOTs and β-CD-DIMOTs stationary phases were compared with native β-CD stationary phase for the enantioseparation of non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, indoprofen, ketoprofen and fenoprofen). The β-CD-BIMOTs stationary phase showed greater chiral resolution capabilities rather than β-CD-DIMOTs and native β-CD stationary phases. Further, in order to understand the interaction of enantioseparation, the inclusion complex formation between NSAIDs and β-CD-BIMOTs was studied using 1H NMR, NOESY and UV/Vis. The enantioseparated NSAIDs were found to form multiple interactions with β-CD-BIMOTs-CSP.

Combined Microdialysis-Tumor Homogenate Method for the Study of the Steady State Compartmental Distribution of a Hydrophobic Anticancer Drug in Patient-Derived Xenografts

PURPOSE

To develop a reproducible microdialysis-tumor homogenate method for the study of the intratumor distribution of a highly hydrophobic anticancer drug (SN-38; 7-ethyl-10-hydroxycamptothecin) in neuroblastoma patient-derived xenografts.

METHODS

We studied the nonspecific binding of SN-38 to the microdialysis tubing in the presence of 2-hydroxypropyl-beta-cyclodextrin (HPBCD) in the perfusate. We calibrated the microdialysis probes by the zero flow rate (ZFR) method and calculated the enhancement factor (f = extrapolated SN-38 concentration at the ZFR / SN-38 concentration in the dialysed solution) of HPBCD. We characterized the extravasation of HPBCD to tumors engrafted in mice. In vivo microdialysis and terminal homogenate data at the steady state (subcutaneous pump infusions) were used to calculate the volume of distribution of unbound SN-38 (Vu,tumor) in neuroblastoma.

RESULTS

HPBCD (10% w/v) in the perfusate prevented the nonspecific binding of SN-38 to the microdialysis probe and enhanced SN-38 recovery (f = 1.86). The extravasation of HPBCD in the tumor during microdialysis was lower than 1%. Vu,tumor values were above 3 mL/g tumor for both neuroblastoma models and suggested efficient cellular penetration of SN-38.

CONCLUSIONS

The method contributes to overcome the limitations of the microdialysis technique in hydrophobic drugs and provides a powerful tool to characterize compartmental anticancer drug distribution in xenografts.

Exploiting β-cyclodextrin in molecular imprinting for achieving recognition of benzylparaben in aqueous media

The molecularly imprinted polymer (MIP) based on methacrylic acid functionalized β-cyclodextrin (MAA-β-CD) monomer was synthesized for the purpose of selective recognition of benzylparaben (BzP). The MAA-β-CD monomer was produced by bridging a methacrylic acid (MAA) and β-cyclodextrin (β-CD) using toluene-2,4-diisocyanate (TDI) by reacting the –OH group of MAA and one of the primary –OH groups of β-CD. This monomer comprised of triple interactions that included an inclusion complex, π–π interaction, and hydrogen bonding. To demonstrate β-CD performance in MIPs, two MIPs were prepared; molecularly imprinted polymer-methacrylic acid functionalized β-cyclodextrin, MIP(MAA-β-CD), and molecularly imprinted polymer-methacrylic acid, MIP(MAA); both prepared by a reversible addition fragmentation chain transfer polymerization (RAFT) in the bulk polymerization process. Both MIPs were characterized using the Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Brunauer-Emmett-Teller (BET). The presence of β-CD not only influenced the morphological structure, it also affected the specific surface area, average pore diameter, and total pore volume of the MIP. The rebinding of the imprinting effect was evaluated in binding experiments, which proved that the β-CD contributed significantly to the enhancement of the recognition affinity and selective adsorption of the MIP.

Cloud point extraction of parabens using non-ionic surfactant with cylodextrin functionalized ionic liquid as a modifier

A cloud point extraction (CPE) process using non-ionic surfactant (DC193C) to extract selected paraben compounds from water samples was investigated using reversed phase high performance liquid chromatography (RP-HPLC). The CPE process with the presence of β-cyclodextrin (βCD) functionalized ionic liquid as a modifier (CPE-DC193C-βCD-IL) is a new extraction technique that has been applied on the optimization of parameters, i.e., pH, βCD-IL concentration and phase volume ratio. This CPE-DC193C-βCD-IL method is facilitated at 30 °C, showing great losses of water content in the surfactant-rich phase, resulting in a high pre-concentration factor and high distribution coefficient. The developed method CPE-DC193C-βCD-IL did show enhanced properties compared to the CPE method without the modifier (CPE-DC193C). The developed method of CPE-DC193C-βCD-IL gives an excellent performance on the detection of parabens from water samples with the limit of detection falling in the range of 0.013-0.038 µg mL-1. Finally, the inclusion complex formation, hydrogen bonding, and π-π interaction between the βCD-IL, benzyl paraben (ArP), and DC 193C were proven using 1H NMR and 2D NOESY spectroscopy.

Removal of 2,4-dichlorophenol using cyclodextrin-ionic liquid polymer as a macroporous material: characterization, adsorption isotherm, kinetic study, thermodynamics

Cyclodextrin-ionic liquid polymer (βCD-BIMOTs-TDI) was firstly synthesized using functionalized β-Cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using toluene diisocyanate (TDI) linker to form insoluble βCD-BIMOTs-TDI. SEM characterization result shows that βCD-BIMOTs-TDI exhibits macropore size while the BET result shows low surface area (1.254 m(2)g(-1)). The unique properties of the ILs allow us to produce materials with different morphologies. The adsorption isotherm and kinetics of 2,4-dichlorophenol (2,4-DCP) onto βCD-BIMOTs-TDI is studied. Freundlich isotherm and pseudo-second order kinetics are found to be the best to represent the data for 2,4-DCP adsorption on the βCD-BIMOTs-TDI. The presence of macropores decreases the mass transfer resistance and increases the adsorption process by reducing the diffusion distance. The change in entropy (ΔS°) and heat of adsorption (ΔH°) for 2,4-DCP on βCD-BIMOTs-TDI were estimated as -55.99 J/Kmol and -18.10 J/mol, respectively. The negative value of Gibbs free energy (ΔG°) indicates that the adsorption process is thermodynamically feasible, spontaneous and chemically controlled. Finally, the interactions between the cavity of βCD-BIMOTs and 2,4-DCP are investigated and the results shows that the inclusion of the complex formation and π-π interaction are the main processes involved in the adsorption process.

Characterization and dynamic properties for the solid inclusion complexes of β-cyclodextrin and perfluorooctanoic acid

The structural characterization and dynamic properties of solid-state inclusion complexes (ICs) formed between β-cyclodextrin (β-CD; host) and perfluorooctanoic acid (PFOA; guest) were investigated using (13)C NMR spectroscopy. The 1:1 and 2:1 host/guest solid-state complexes were prepared using a modified dissolution method to obtain complexes with high phase purity. These complexes were further characterized using differential scanning calorimetry (DSC), FT-IR spectroscopy, powder X-ray diffraction (PXRD), (19)F directpolarization (DP), and (13)C cross-polarization (CP) with magic-angle spinning (MAS) NMR spectroscopy. The (19)F → (13)C CP results provided unequivocal support for the formation of well-defined inclusion compounds. The phase purity of the complexes formed between β-CD and PFOA were assessed using the (19)F DP NMR technique at variable temperature (VT) and MAS at 20 kHz. The complexes were found to be of high phase purity when prepared in accordance with the modified dissolution method. The motional dynamics of the guest in the solid complexes were assessed using T1/T2/T1ρ relaxation NMR methods at ambient and VT conditions. The relaxation data revealed reliable and variable guest dynamics for the 1:1 versus 2:1 complexes at the VTs investigated. The motional dynamics of the guest molecules involve an ensemble of axial motions of the whole chain and 120° rotational jumps of the methyl (CF3) group at the termini of the perfluorocarbon chain. The axial and rotational dynamics of the guest in the 1:1 and 2:1 complexes differ in distribution and magnitude in accordance with the binding geometry of the guest within the host.

Investigation of a novel 3-fluid nozzle spray drying technology for the engineering of multifunctional layered microparticles

OBJECTIVE

To examine the potential of a novel 3-fluid nozzle spray drying technology to formulate differentiated layered microparticles (MPs) of diclofenac sodium (DFS)/ethyl cellulose (EC).

METHODS

DFS/EC MPs were formulated using the inner and/or outer nozzles of a novel 3-fluid nozzle and compared with MPs formed using conventional (2-fluid) spray drying. MPs were characterised for particle size and for morphology by TEM and SEM. Distribution of DFS and EC of MPs was analysed by FT-IR and DSC. A two-factor, three-level (3(2)) factorial design was applied to investigate the effect and interaction of total feed solid content (TSC) and feed flow rate (FFR) on MP size, D(50%) and D(90%), bulk density and MP yield.

RESULTS

Interestingly, TEM demonstrated that MPs formed by 3-fluid nozzle spray drying showed a heterogeneous internal morphology consisting of a core and coat, characteristic of a microcapsule. In comparison, MPs from conventional spray drying showed a homogeneous internal morphology, characteristics of a matrix system. This differential distribution of DFS/EC was supported by FT-IR and DSC. Results of multiple linear regression analysis showed a linear relationship for the effect of TSC and FFR on all responses except for D(50%) where a quadratric model was valid. The effect of TSC/FFR on MP size and yield was similar to conventional spray drying.

CONCLUSION

The novel 3-fluid nozzle spray drying offers a new method of designing layered microparticles or microcapsules which can have wide applications from drug stabilisation to controlled drug delivery and targeting.

Conventional study on novel dicationic ionic liquid inclusion with β-cyclodextrin

This study focuses on the synthesis and characterization of the inclusion complex of β-Cyclodextrin (β-CD) with dicationic ionic liquid, 3,3′-(1,4-Phenylenebis [methylene]) bis(1-methyl-1H-imidazol-3-ium) di(bromide) (PhenmimBr). The inclusion complex was prepared at room temperature utilizing conventional kneading technique. Proton (¹H) NMR and 2D (¹H–¹H) COSY NMR were the primary characterization tools employed to verify the formation of the inclusion complex. COSY spectra showed strong correlations between protons of imidazolium and protons of β-CD which indicates that the imidazolium ring of PhenmimBr has entered the cavity of β-CD. UV absorption indicated that β-CD reacts with PhenmimBr to form a 2:1 β-CD-PhenmimBr complex with an apparent formation constant of 2.61 × 10⁵ mol&⁻² L². Other characterization studies such as UV, FT-IR, XRD, TGA, DSC and SEM studies were also used to further support the formation of the β-CD-PhenmimBr inclusion complex.

Synthesis and characterization of the inclusion complex of dicationic ionic liquid and β-cyclodextrin

The supramolecular structure of the inclusion complex of β-cyclodextrin (β-CD) with 1,1',2,2'-tetramethyl-3,3'-(p-phenylenedimethylene) diimidazolium dibromide (TetraPhimBr), a dicationic ionic liquid, has been investigated. The inclusion complex with 1:1 molar ratio was prepared by a kneading method. Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) analysis, (1)H NMR and thermogravimetric analysis (TGA) confirmed the formation of the inclusion complex. The results showed that the host-guest system is a fine crystalline powder. The decomposition temperature of the inclusion complex is lower than that of its parent molecules, TetraPhimBr and β-CD individually.

Stability studies on aqueous and oily ophthalmic solutions of diclofenac

Various aqueous and oily diclofenac ophthalmic formulations were subjected to accelerated and long term stability studies. Degradation of diclofenac was found to follow first-order kinetics. Among the aqueous formulations containing preservative, formulation with PMA, PMN, SA, MP/PP and SMS showed diclofenac content above 90% after 6 months of accelerated and 12 months of room temperature storage. Diclofenac 0.1%, w/v aqueous formulation (pH 7.4), with 5-10% overages, containing SMS, MP/PP or PMN look promising taking both stability and corneal permeability in view. However, for use in cataract surgery formulation without preservative appears ideal. Oily ophthalmic formulations except those in olive and mustard oil, had more than 90% drug content after 6 months of accelerated and 12 months of room temperature storage. Diclofenac (0.2%, w/v) ophthalmic solution in sesame oil with 3% overage and containing benzyl alcohol (0.5%, v/v) as preservative, appears ideal, taking both stability and corneal permeability in view.

Kinetic measurements of the hydrolytic degradation of cefixime: effect of Captisol complexation and water-soluble polymers

We have taken kinetic measurements of the hydrolytic degradation of cefixime, and have studied the effect of Captisol complexation and water-soluble polymers on that degradation. The phase solubility of cefixime in Captisol was determined. Kinetic measurements were carried out as a function of pH and temperature. High-performance liquid chromatography (HPLC) was performed to assay all the samples of phase-solubility analysis and kinetic measurements. Chromatographic separation of the degradation products was also performed by HPLC. FT-IR spectroscopy was used to investigate the presence of any interaction between cefixime and Captisol and soluble polymer. The phase-solubility study showed A(L)-type behaviour. The pH-rate profile of cefixime exhibited a U-shaped profile whilst the degradation of cefixime alone was markedly accelerated with elevated temperature. A strong stabilizing influence of the cefixime-Captisol complexation and hypromellose was observed against aqueous mediated degradation, as compared with povidone and macrogol. The unfavourable effect of povidone and macrogol may have been due to the steric hindrance, which prevented the guest molecule from entering the cyclodextrin cavity, whereas hypromellose did not produce any steric hindrance.

Cyclodextrins in drug delivery: an updated review

The purpose of this review is to discuss and summarize some of the interesting findings and applications of cyclodextrins (CDs) and their derivatives in different areas of drug delivery, particularly in protein and peptide drug delivery and gene delivery. The article highlights important CD applications in the design of various novel delivery systems like liposomes, microspheres, microcapsules, and nanoparticles. In addition to their well-known effects on drug solubility and dissolution, bioavailability, safety, and stability, their use as excipients in drug formulation are also discussed in this article. The article also focuses on various factors influencing inclusion complex formation because an understanding of the same is necessary for proper handling of these versatile materials. Some important considerations in selecting CDs in drug formulation such as their commercial availability, regulatory status, and patent status are also summarized. CDs, because of their continuing ability to find several novel applications in drug delivery, are expected to solve many problems associated with the delivery of different novel drugs through different delivery routes.

A Raman spectroscopic study of the diclofenac sodium–β-cyclodextrin interaction

The inclusion complex of diclofenac sodium (DCFNa) and beta-cyclodextrin (betaCD) was prepared and analyzed by using Raman and SERS spectroscopy. The interaction between DCFNa and betaCD molecules was evidenced by monitoring the change in the peak positions and the widths of some guest molecule bands relative to those observed in the spectra of the free compound and 1:1 DCFNa-betaCD physical mixture. Raman data have shown that the interaction between the guest and host molecules in the 1:1 DCFNa-betaCD complex is maintained both through the dichlorophenyl ring and the phenylacetate group. SER spectra revealed that depending on the pH value of the solution different isomeric forms of the 1:1 guest-host complex are preferentially adsorbed on the silver surface via the nonbonding electrons of the oxygen atom. The orientation of the adsorbed species with respect to the metal surface was also elucidated.

Calorimetric studies of diclofenac sodium in aqueous solution of cyclodextrin and water-ethanol mixtures

The technique of solution calorimetry has been employed to study the interaction between diclofenac sodium and beta-cyclodextrin by determining the enthalpies of solution of the drug in water and in aqueous beta-cyclodextrin solution. Thermodynamic parameters characterizing the binding process such as enthalpy deltaH0, equilibrium constant K, free energy deltaG0 and entropy deltaS0 have been calculated to be 12.00 kJ mol(-1), 1670 dm3 mol(-1), -19.03kJ mol(-1) and 22.98 J K(-1) mol(-1), respectively. Enthalpies of solution of diclofenac sodium have also been determined in water-ethanol mixtures.

Thermal behaviour of diclofenac sodium: decomposition and melting characteristics

The thermal behaviour and melting characteristics of diclofenac sodium were investigated using various instrumental techniques--differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy and thin layer chromatography (TLC). DSC analysis of diclofenac sodium performed under dynamic flow of either synthetic air or helium or nitrogen did not produce any sharp endothermic peak characteristic of melting peak of a pure substance. Both the rate of scanning of the sample and the environmental atmospheric condition significantly affected the thermographic profile of diclofenac sodium. An exothermic peak prior to an endothermic peak corresponding to melting of the substance appeared when heated under dynamic flow of synthetic air suggesting oxidation (decomposition) of diclofenac sodium before reaching its melting point. In fact, at a scanning rate of 1 degree C/min only the exothermic peak appeared in the thermogram, suggesting complete decomposition prior to melting under the dynamic flow of synthetic air. DSC, FT-IR and TLC data obtained from samples heated under the dynamic flow of either helium or nitrogen revealed formation of a related compound, 1-(2,6-dichlorophenyl)-indolin-2-one, an indol-cyclic amide, as a result of an intramolecular cyclization reaction during the heating process. TGA data demonstrated a loss of 11.4-20.2% of the mass of diclofenac sodium when heated under various environmental conditions, and also supported the oxidative nature of degraded product(s) when the thermal process occurred slowly under a dynamic flow of synthetic air.

Cyclodextrin complexes of salts of acidic drugs. Thermodynamic properties, structural features, and pharmaceutical applications

The objective of this mini-review is to summarize the findings concerning the physicochemical properties and the pharmaceutical applications of acidic drugs whose performances have been modified by simultaneous complexation with cyclodextrins and salt formation. Particular attention is paid to the approaches undertaken for increasing the solubility of the drugs by proper choice of the type of counterion analogously to what has been reported for complexes of basic drugs in the presence of hydroxy acids.