Preparation of celecoxib-dimethyl-β-cyclodextrin inclusion complex: characterization and in vitro permeation study

In vitro and in silico studies of the inclusion complexation of 8-bromobaicalein with β-cyclodextrins

Baicalein, a flavone derived from Scutellaria baicalensis Georgi, exhibits potent anti-inflammatory, antiviral, and anticancer properties. Its derivative, known as 8-bromobaicalein (BB), has been found to have strong cytotoxic effect on MCF-7 human breast cancer cells. However, its limited solubility in water has hindered its potential for wider applications. To address this issue, we investigated the use of cyclodextrins specifically βCD, 2,6-di-O-methyl-β-cyclodextrin (DMβCD), and hydroxypropyl-β-cyclodextrin (HPβCD) to improve the solubility of BB through inclusion complexation. During 250 ns molecular dynamics simulations, it was found that BB can form inclusion complexes with all βCDs. These complexes exhibit two distinct orientations: chromone group insertion (C-form) and phenyl group insertion (P-form). The formation of these complexes is primarily driven by van der Waals interactions. DMβCD has the highest number of atom contacts with BB and the lowest solvent accessibility in the hydrophobic cavity. These results coincide with the highest binding affinity from the MM/GBSA-based free energy calculation method. Experimental phase solubility diagrams revealed a 1:1 stoichiometric ratio (AL type) between BB and βCDs, in which BB/DMβCD showed the highest stability. The formation of inclusion complexes was confirmed by differential scanning calorimetry and scanning electron microscope methods. Additionally, the BB/DMβCD inclusion complex demonstrated significantly higher anticancer activity against MCF-7 human breast cancer cells compared to BB alone. These findings underscore the potential of DMβCD for formulating BB in pharmaceutical and medical applications.

Evaluating solubility, stability, and inclusion complexation of oxyresveratrol with various β-cyclodextrin derivatives using advanced computational techniques and experimental validation

Oxyresveratrol (OXY), a natural stilbenoid in mulberry fruits, is known for its diverse pharmacological properties. However, its clinical use is hindered by low water solubility and limited bioavailability. In the present study, the inclusion complexes of OXY with β-cyclodextrin (βCD) and its three analogs, dimethyl-β-cyclodextrin (DMβCD), hydroxypropyl-β-cyclodextrin (HPβCD) and sulfobutylether-β-cyclodextrin (SBEβCD), were investigated using in silico and in vitro studies. Molecular docking revealed two binding orientations of OXY, namely, 4',6'-dihydroxyphenyl (A-form) and 5,7-benzenediol ring (B-form). Molecular Dynamics simulations suggested the formation of inclusion complexes with βCDs through two distinct orientations, with OXY/SBEβCD exhibiting maximum atom contacts and the lowest solvent-exposed area in the hydrophobic cavity. These results corresponded well with the highest binding affinity observed in OXY/SBEβCD when assessed using the MM/GBSA method. Beyond traditional simulation methods, Ligand-binding Parallel Cascade Selection Molecular Dynamics method was employed to investigate how the drug enters and accommodates within the hydrophobic cavity. The in silico results aligned with stability constants: SBEβCD (2060 M-1), HPβCD (1860 M-1), DMβCD (1700 M-1), and βCD (1420 M-1). All complexes exhibited a 1:1 binding mode (AL type), with SBEβCD enhancing OXY solubility (25-fold). SEM micrographs, DSC thermograms, FT-IR and 1H NMR spectra confirm the inclusion complex formation, revealing novel surface morphologies, distinctive thermal behaviors, and new peaks. Notably, the inhibitory impact on the proliferation of breast cancer cell lines, MCF-7, exhibited by inclusion complexes particularly OXY/DMβCD, OXY/HPβCD, and OXY/SBEβCD were markedly superior compared to that of OXY alone.

Celecoxib Nanoformulations with Enhanced Solubility, Dissolution Rate, and Oral Bioavailability: Experimental Approaches over In Vitro/In Vivo Evaluation

Celecoxib (CXB) is a Biopharmaceutical Classification System (BCS) Class II molecule with high permeability that is practically insoluble in water. Because of the poor water solubility, there is a wide range of absorption and limited bioavailability following oral administration. These unfavorable properties can be improved using dry co-milling technology, which is an industrial applicable technology. The purpose of this study was to develop and optimize CXB nanoformulations prepared by dry co-milling technology, with a quality by design approach to maintain enhanced solubility, dissolution rate, and oral bioavailability. The resulting co-milled CXB composition using povidone (PVP), mannitol (MAN) and sodium lauryl sulfate (SLS) showed the maximum solubility and dissolution rate in physiologically relevant media. Potential risk factors were determined with an Ishikawa diagram, important risk factors were selected with Plackett-Burman experimental design, and CXB compositions were optimized with Central Composite design (CCD) and Bayesian optimization (BO). Physical characterization, intrinsic dissolution rate, solubility, and stability experiments were used to evaluate the optimized co-milled CXB compositions. Dissolution and permeability studies were carried out for the resulting CXB nanoformulation. Oral pharmacokinetic studies of the CXB nanoformulation and reference product were performed in rats. The results of in vitro and in vivo studies show that the CXB nanoformulations have enhanced solubility (over 4.8-fold (8.6 ± 1.06 µg/mL vs. 1.8 ± 0.33 µg/mL) in water when compared with celecoxib pure powder), and dissolution rate (at least 85% of celecoxib is dissolved in 20 min), and improved oral pharmacokinetic profile (the relative bioavailability was 145.2%, compared to that of Celebrex^®, and faster t_max 3.80 ± 2.28 h vs. 6.00 ± 3.67 h, indicating a more rapid absorption rate).

Osmani RA, Alqahtani A, Ghazwani M, Hani U, Ather H, Atiya A, Rahamathulla M, Siddiqua A. Development of stealth liposomal formulation of celecoxib: In vitro and in vivo evaluation

Celecoxib (CLB) is a highly hydrophobic selective cyclo-oxygenase inhibitor with high plasma protein binding and undergoes extensive hepatic metabolism. CLB is highly effective in the treatment of osteo and rheumatoid arthritis as first line therapy but produces severe gastro-intestinal toxicities and cardiovascular side effects. In this research, stealth liposomes of CLB were developed with the intention to reduce the side effects and increase the accumulation of drug in the sites of inflammation. Stealth liposomes were prepared by thin film hydration technique using distearoylphosphatidylcholine and PE-PEG 2000 with variable amounts of cholesterol and characterized. The effects of various lipids such as hydrogenated soy phosphatidylcholine, dipalmitoyl phosphatidylcholine, distearoylphosphatidylcholine and cholesterol content on % drug encapsulation was investigated. The optimized stealth liposomes were characterized by FT-IR and DSC for possible drug excipients interaction. Pharmacokinetics, pharmacodynamics and biodistribution studies were carried out for the stealth liposomes. The results revealed that the stealth liposomes reduced the inflammation to the larger magnitude and have also sustained the magnitude when compared to free drug along with maximum analgesic response. Higher elimination half-life, AUC, MRT and lowered clearance rate denotes the extended bioavailability of the drug in blood. Biodistribution studies revealed that stealth liposomes extend the circulation time of liposomes in blood by decreasing opsonisation and be less concentrated in kidney, thereby reducing the toxicities to RES and renal organs and facilitate the drug accumulation in the area of inflammation. Our results indicated that CLB, without the requirement of modifications to enhance solubilisation, can be encapsulated and released from liposomal formulations. This new-fangled drug delivery approach may be used to circumvent the low bioavailability and toxic side effects of oral CLB formulations.

Chiral Recognition R- and RS- of New Antifungal: Complexation/Solubilization/Dissolution Thermodynamics and Permeability Assay

Novel potential antifungal of 1,2,4-triazole class have been synthesized as pure enantiomer (R-98) and racemic (RS-186). The effect of 2-hydroxypropyl-β-cyclodextrin (CD) on the solubility and permeability of RS-186 and R-98 in terms of chiral recognition was investigated. Phase solubility studies were carried out at 4 temperatures in 0-0.05 M CD concentration range for pH 2.0 and pH 7.4. AL- and AL--type phase-solubility profiles were obtained for both compounds in pH 2.0 and pH 7.4. The racemic formed more stable complexes with CD as compared to R-isomer. Disclosing of chiral discrimination was facilitated using the approach based on the complex consideration of the derived complexation/solubilization/inherent dissolution thermodynamic functions, including the differential parameters between the racemic compound and R-enantiomer. The differences in the thermodynamic parameters determined by the chirality were discussed in terms of the driving forces of the processes and the main interactions of the compounds with CD in solution. The membrane permeability of both samples in the presence of CD was accessed in order to evaluate the specificity of enantioselective transport through the lipophilic membrane. The solubility/permeability interrelation was disclosed. The investigated compounds were classified as medium permeable in pure buffers and low permeable in the presence of 0.01 M CD. The obtained results can be useful for the design of pharmaceutical products in the form of liquid formulations based on the investigated substances.

Functional block copolymer micelles based on poly (jasmine lactone) for improving the loading efficiency of weakly basic drugs

Functionalization of polymers is an attractive approach to introduce specific molecular forces that can enhance drug–polymer interaction to achieve higher drug loading when used as drug delivery systems. The novel amphiphilic block copolymer of methoxy poly(ethylene glycol) and poly(jasmine lactone) i.e., mPEG-b-PJL, derived from renewable jasmine lactone provides free allyl groups on the backbone thus, allowing flexible and facile post-synthesis functionalization. In this study, mPEG-b-PJL and its carboxyl functionalized polymer mPEG-b-PJL-COOH were utilised to explore the effect of ionic interactions on the drug–polymer behaviour. Various drugs with different pK_a values were employed to prepare drug-loaded polymeric micelles (PMs) of mPEG-b-PJL, mPEG-b-PJL-COOH and Soluplus® (polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer) via a nanoprecipitation method. Electrostatic interactions between the COOH pendant on mPEG-b-PJL-COOH and the basic drugs were shown to influence the entrapment efficiency. Additionally, molecular dynamics (MD) simulations were employed to understand the polymer–drug interactions at the molecular level and how polymer functionalization influenced these interactions. The release kinetics of the anti-cancer drug sunitinib from mPEG-b-PJL and mPEG-b-PJL-COOH was assessed, and it demonstrated a sustainable drug release pattern, which depended on both pH and temperature. Furthermore, the cytotoxicity of sunitinib-loaded micelles on cancer cells was evaluated. The drug-loaded micelles exhibited dose-dependent toxicity. Also, haemolysis capacity of these polymers was investigated. In summary, polymer functionalization seems a promising approach to overcome challenges that hinder the application of polymer-based drug delivery systems such as low drug loading degree.

Block copolymer micelles with a functional core have been synthesized and evaluated for their drug delivery capability. High drug loading was observed due to strong ionic interactions, while cytotoxicity of polymers was found to be low.

Increasing the Transport of Celecoxib over a Simulated Intestine Cell Membrane Model Using Mesoporous Magnesium Carbonate

In the current work, mesoporous magnesium carbonate (MMC) was used to suppress crystallization of the poorly soluble drug celecoxib (CXB). This resulted in both a higher dissolution rate and supersaturation of the substance in vitro as well as an increased transfer of CXB over a Caco-2 cell membrane mimicking the membrane in the small intestine. The CXB flux over the cell membrane showed a linear behavior over the explored time period. These results indicate that MMC may be helpful in increasing the bioavailability and obtaining a continuous release of CXB, and similar substances, in vivo. Neusilin US2 was used as a reference material and showed a more rapid initial release with subsequent crystallization of the incorporated CXB in the release media. The presented results form the foundation of future development of MMC as a potential carrier for poorly soluble drugs.

Celecoxib Crystallized from Hydrophilic Polymeric Solutions Showed Modified Crystalline Behavior with an Improved Dissolution Profile

The crystallization technique has been established as a cost-effective and simple approach to improve the dissolution rate and oral bioavailability of poorly soluble drugs. This study was carried out to study the effect of some selected hydrophilic polymers such as methyl cellulose, hydroxypropyl methylcellulose (HPMC), polyvinyl alcohol, and carboxymethyl cellulose on the crystal behavior and dissolution properties of celecoxib (CLX), a common nonsteroidal anti-inflammatory drug. Structural and spectral characteristics of crystallized CLX have been studied by Fourier transform infrared (FTIR) spectroscopy, diffraction scanning calorimetry (DSC), and X-ray diffraction (XRD) analysis. From FTIR and DSC analysis, no significant shifting of peaks or appearance of any new peaks (for polymers) were observed, which indicated the absence of any major interaction between drug and polymers as well as the absence of polymers in the final crystallized product of CLX. The XRD analysis showed a change in crystalline morphology to some extent. The dissolution rate of crystallized CLX in the presence of polymers (particularly with HPMC) was significantly improved compared with plain CLX. The improved dissolution profile of the experimental CLX crystal products could be an indication of improved bioavailability of CLX for better clinical outcome.

Study on the preparation of geranyl acetone and β-cyclodextrin inclusion complex and its application in cigarette flavoring

β-Cyclodextrin (β-CD) inclusion complex containing geranyl acetone as a guest was prepared by saturated water solution method. Furthermore, the structure and properties of the inclusion complex were studied. The formation of the inclusion complex was demonstrated by. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (X-RD), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The thermodynamic analysis of the inclusion complex showed that the inclusion reaction is an endothermic spontaneous reaction. The average of △H, △S and △G is 11.66 kJ mol-1, 0.082 kJ mol-1 and - 14.49 kJ mol-1, respectively. Moreover, the kinetic analysis of thermal decomposition of the inclusion compound showed that the thermal decomposition reaction is a first-order reaction (the inclusion ratio is 1:1), the average activation energy of the reaction is 180.90 kJ mol-1, and the binding force in the inclusion compound is mainly Van der Waals force. The flavor test of cigarettes showed that the inclusion compound improved the stability of geranyl acetone and the sensory quality of cigarettes. This study improves the solubility and thermal stability of geranyl acetone, and provides theoretical support and technical guidance for expanding the application of geranyl acetone.

Enhanced Solubility and Anticancer Potential of Mansonone G By β-Cyclodextrin-Based Host-Guest Complexation: A Computational and Experimental Study

Mansonone G (MG), a plant-derived compound isolated from the heartwood of Mansonia gagei, possesses a potent antitumor effect on several kinds of malignancy. However, its poor solubility limits the use for practical applications. Beta-cyclodextrin (βCD), a cyclic oligosaccharide composed of seven (1→4)-linked α-D-glucopyranose units, is capable of encapsulating a variety of poorly soluble compounds into its hydrophobic interior. In this work, we aimed to enhance the water solubility and the anticancer activity of MG by complexation with βCD and its derivatives (2,6-di-O-methyl-βCD (DMβCD) and hydroxypropyl-βCD). The 90-ns molecular dynamics simulations and MM/GBSA-based binding free energy results suggested that DMβCD was the most preferential host molecule for MG inclusion complexation. The inclusion complex formation between MG and βCD(s) was confirmed by DSC and SEM techniques. Notably, the MG/βCDs inclusion complexes exerted significantly higher cytotoxic effect (~2–7 fold) on A549 lung cancer cells than the uncomplexed MG.

Gemcitabine anticancer activity enhancement by water soluble celecoxib/sulfobutyl ether-β-cyclodextrin inclusion complex

We investigated the complexation of celecoxib (CCB) into sulfobuthyl-ether-β-cyclodextrin (SBE-β-CD) for the realization of an inhalable dry-powder formulation containing gemcitabine (GEM) for lung anticancer therapy. Complexation increased the water solubility of CCB (0.003 mg/mL and 0.834 mg/mL for CCB free and complexed, respectively) and produced a quantitative dissolution of the drug within 15 min. The CCB/SBE-β-CD inclusion complex showed a high stability constant (8131 M-1) not influenced by the presence of GEM in solution. Two-dimensional NMR experiments and computational studies demonstrated that the pyrazole ring of CCB penetrates deeper into SBE-β-CD from the secondary rim. The aromatic rings are positioned at the edge of the cavity, establishing hydrogen bonds with the SBE-β-CD that stabilized the complex. CCB showed limited cytotoxic activity on A549 cell lines. Complexation significantly increased activity passing from 30% to 45% cell mortality. Moreover, CCB/SBE-β-CD strongly improved the cytotoxicity of GEM, observing about 60% of cell mortality for the combined formulation.

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.

Spray Dried Chitosan Microparticles for Intravesical Delivery of Celecoxib: Preparation and Characterization

PURPOSE

Chitosan microparticles containing celecoxib (CB), were developed as chemoprevention of bladder cancer. Furthermore two inclusion complexes of CB with methyl-β-cyclodextrin (C1 and C2) were prepared to improve the solubility of the drug.

METHODS

C1 and C2 were obtained by freeze-drying and characterized in the solid state and in solution. Microparticles loaded with CB or C1 or C2 were prepared by spray drying and fully characterized.

RESULTS

The yield and encapsulation efficiencies of microparticles depended by both the viscosity and the presence of the inclusion complex in the feed medium nebulised. Generally, the microparticles exhibited a spherical shape with mean diameter of approximately 2 μm which was compatible with local intravesical administration using a catheter. The CB release studies from the microparticles allowed us to identify both immediate release systems (microparticles including the complexes) and prolonged release systems (microparticles including CB alone). The latter exhibited good adhesion to the bladder mucosa, as highlighted by a mucoadhesion study. Histological studies revealed a desquamation of the superficial cells when the bladder mucosa was treated with microparticles loaded with CB, while the morphology of the urothelium did not change when it was treated with microparticles loaded with the inclusion complex.

CONCLUSION

A new CB intravesical formulation than can easily be administered with a catheter and is able to release the drug at the target site for several hours was realized. This new delivery system could be a good alternative to classic oral CB administration.

Formulation and Evaluation of Liposomes for Transdermal Delivery of Celecoxib

Background:

Celecoxib is a selective cyclo-oxygenase-2 inhibitor recommended orally to treat arthritis and osteoarthritis. It is a highly lipophilic, poorly soluble drug with oral bioavailability of around 40%. Long term oral administration of celecoxib causes serious gastrointestinal side effects.

Objectives:

The current study aimed to assess the skin permeation of celecoxib by a transdermally applied liposomal formulation.

Materials and Methods:

Liposomes were prepared by thin film method using soya lecithin and cholesterol. Physicochemical characteristics of the liposomes such as, particle size, drug encapsulation efficiency were determined. Also, drug release and in vitro skin permeability through rat skin were evaluated using Franz diffusion cells.

Results:

The results showed that the maximum drug encapsulation efficiency was 43.24%. Drug release profile showed that 81.25% of the drugs released in the first 24 hours of the experiment. Fluxes (Jss), permeability coefficient (P), diffusivity coefficient (D) parameters of the optimum liposomal formulation were significantly higher than those of saturated aqueous solution of celecoxib. The decrease of lecithin increased values. Particle sizes of the formulations ranged from 0.117 to 1.123 µm. J_ss, D_app and P parameters in L - 8 formulations were 29.18, 60.95, and 3.21 times higher than those of saturated water solution of celecoxib, respectively. The results of vesicles characterization indicated the potential application of celecoxib loaded liposome as carrier system.

Conclusions:

In conclusion, the components such as lecithin and cholesterol, and vortex time in liposomal formulations have an essential role in the physicochemical properties and celecoxib permeability through rat skin.

Temperature Dependence of the Complexation Mechanism of Celecoxib and Hydroxyl-β-cyclodextrin in Aqueous Solution

Hydroxypropyl-β-cyclodextrin (HP-β-CD) is commonly used as a complexation reagent to solubilize compounds with poor aqueous solubility to improve in vivo dosing. However, the degree of solubility enhancement was often limited by the formation of only a 1:1 complex and a low complexation constant (K). Such a limitation can be significantly improved by the formation of 1:2 complexes in some cases. Despite the understanding of the solubility advantage of the formation of the 1:2 complexes, there is no systematic understanding that could drive for the formation of 1:2 complexes. Thus, in most cases, the formation of 1:2 complexes was limited by observation bases. In this study, we pioneer the usages of molecular dynamics (MD) simulation to understand the phenomena of a model drug of celecoxib (CCB) and HP-β-CD. It has been reported that celecoxib (CCB) forms 1:1 complexes with cyclodextrin in solution; however, some data suggest the existence of a 1:2 complex. The simulation results suggest that a transition state of CCB and HP-β-CD may exit at a higher temperature of CCB and HP-β-CD; a model drug, such as celecoxib (CCB), that is known to form 1:1 complexes can achieve a higher degree of complexation (1:2) and obtain much improved solubility when the same amount of cyclodextrin was used and demonstrated in vitro. The simulation results of CCB and HP-β-CD could be a model system that may provide important insights into the inclusion mechanism.

Liposomal gels for site-specific, sustained delivery of celecoxib: in vitro and in vivo evaluation

The objective of this work was to evaluate liposome-containing gel formulations for the sustained, site-specific delivery of celecoxib (CXB). Liposomes composed of phosphadtidylcholine (and various amounts of cholesterol (Ch) were prepared using thin film hydration and characterized for encapsulation efficiency, vesicle size, and drug-excipient interaction using differential scanning calorimetry and Fourier-transform infrared spectroscopy. The selected liposome formulation was incorporated in different gel formulations: the Ch ratio affected the encapsulation efficiency of the drug, by increasing Ch ratio up until 1:1 the encapsulation efficiency increased. Further increasing the Ch ratio resulted in decreasing encapsulation efficiency. In vitro drug release and skin permeation studies showed sustained release and enhanced permeation compared with gel formulations containing free drug. In the rat paw edema test, the anti-inflammatory activity of the selected liposomal gel formulation was higher and more sustained compared with that of the nonliposomal gel formulation containing free drug. These results suggest that the liposome-containing gels are promising formulations for sustained, site-specific delivery of CXB.

Piroxicam-β-cyclodextrin: a GI safer piroxicam

Although NSAIDs are very effective drugs, their use is associated with a broad spectrum of adverse reactions in the liver, kidney, cardiovascular (CV) system, skin and gut. Gastrointestinal (GI) side effects are the most common and constitute a wide clinical spectrum ranging from dyspepsia, heartburn and abdominal discomfort to more serious events such as peptic ulcer with life-threatening complications of bleeding and perforation. The appreciation that CV risk is also increased further complicates the choices of physicians prescribing anti-inflammatory therapy. Despite prevention strategies should be implemented in patients at risk, gastroprotection is often underused and adherence to treatment is generally poor. A more appealing approach would be therefore to develop drugs that are devoid of or have reduced GI toxicity. Gastro-duodenal mucosa possesses many defensive mechanisms and NSAIDs have a deleterious effect on most of them. This results in a mucosa less able to cope with even a reduced acid load. NSAIDs cause gastro-duodenal damage, by two main mechanisms: a physiochemical disruption of the gastric mucosal barrier and systemic inhibition of gastric mucosal protection, through inhibition of cyclooxygenase (COX, PG endoperoxide G/H synthase) activity of the GI mucosa. However, against a background of COX inhibition by anti-inflammatory doses of NSAIDs, their physicochemical properties, in particular their acidity, underlie the topical effect leading to short-term damage. It has been shown that esterification of acidic NSAIDs suppresses their gastrotoxicity without adversely affecting anti-inflammatory activity. Another way to develop NSAIDs with better GI tolerability is to complex these molecules with cyclodextrins (CDs), giving rise to so-called “inclusion complexes” that can have physical, chemical and biological properties very different from either those of the drug or the cyclodextrin. Complexation of NSAIDs with β-cyclodextrin potentially leads to a more rapid onset of action after oral administration and improved GI tolerability because of minimization of the drug gastric effects. One such drug, piroxicam-β-cyclodextrin (PBC), has been used in Europe for 25 years. Preclinical and clinical pharmacology of PBC do show that the β-cyclodextrin inclusion complex of piroxicam is better tolerated from the upper GI tract than free piroxicam, while retaining all the analgesic and anti-inflammatory properties of the parent compound. In addition, the drug is endowed with a quick absorption rate, which translates into a faster onset of analgesic activity, an effect confirmed in several clinical studies. An analysis of the available trials show that PBC has a GI safety profile, which is better than that displayed by uncomplexed piroxicam. Being an inclusion complex of piroxicam, whose CV safety has been pointed out by several observational studies, PBC should be viewed as a CV safe anti-inflmmatory compound and a GI safer alternative to piroxicam. As a consequence, it should be considered as a useful addition to our therapeutic armamentarium.

Celecoxib-loaded PLGA/cyclodextrin microspheres: characterization and evaluation of anti-inflammatory activity on human chondrocyte cultures

PLGA microspheres were prepared as a sustained release system for the intra-articular administration of celecoxib (CCB). The microspheres were prepared in the presence of different concentrations of dimethyl-β-cyclodextrin (DM-β-Cyd), by the simple oil-in-water emulsion/evaporation solvent method. The microspheres were evaluated as to surface morphology, size and technological properties (such as encapsulation efficiency, drug loading capacity and drug release). Ex vivo studies on cultures of human chondrocytes were performed in order to evaluate the influence of the polymeric carriers on the pharmacological activity of CCB. All systems ranged from about 1 to 5 μm in size and had a high encapsulation efficiency percentage ranging from about 80% to 90% (w/w), except for CCB-loaded-PLGA microspheres containing the highest amount of DM-β-Cyd, in which a dramatic drop in the encapsulation efficiency was observed (about 54%, w/w). FIB images evidenced the fact that the microspheres had a porous structure in the presence of the highest amount of DM-β-Cyd. The macrocycle modulated the release profiles of CCB from the microspheres, producing in some cases a zero-order kinetic release. Ex vivo biological studies demonstrated that DM-β-Cyd improved the drug's anti-inflammatory activity. Thus, CCB-loaded PLGA/cyclodextrin microspheres may have a potential therapeutic application in the treatment of osteo- and rheumatoid arthritis.

Enhanced dissolution and stability of lansoprazole by cyclodextrin inclusion complexation: preparation, characterization, and molecular modeling

In this study, lansoprazole (LSP)/cyclodextrin (CD) inclusion complexes were prepared using a fluid bed coating technique, with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HPCD) as the host molecules, respectively, to simultaneously improve the dissolution and stability of LSP. The dissolution rate and stability of LSP was dramatically enhanced by inclusion complexation regardless of CD type. LSP/HPCD inclusion complex was more stable under illumination than LSP/β-CD inclusion complex. Differential scanning calorimetry and powder X-ray diffractometry proved the absence of crystallinity in both LSP/CD inclusion complexes. Fourier transform infrared spectroscopy together with molecular modeling indicated that the benzimidazole of LSP was included in the cavity of both CDs, while LSP was more deeply included in HPCD than β-CD. The enhanced photostability was due to the inclusion of the sulfinyl moiety into the HPCD cavity. CD inclusion complexation could improve the dissolution and stability of LSP.

Interaction of liposome-encapsulated cisplatin with biomolecules

We prepared liposomes by hydrating 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid with aqueous solutions of three "probe" molecules-cis-diamminedichloroplatinum(II) (cis-[Pt(II)(NH(3))(2)Cl(2)], cisplatin), guanosine 5'-monophosphate (5'-GMP), and 9-ethylguanine (9-EtG)-in phosphate-buffered saline as well as N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid buffer. The positively charged hydrolysis product of cisplatin, [Pt(II)(NH(3))(2)Cl(H(2)O)](+), is in the inner core of the liposomes and negatively charged 5'-GMP embeds in the lipid bilayer of liposomes. In the presence of cisplatin, the size of the liposomes remains unchanged, and for 5'-GMP-embedded liposomes the size increases significantly compared with that of empty or control liposomes. In contrast, the neutral biomolecule 9-EtG was found to be dispersed in the exterior bulk water and the size of the liposomes remained the same as that of empty or control liposomes. When cisplatin-containing liposomes mix with 5'-GMP-embedded liposomes or liposomes with 9-EtG, the N7 nitrogen atom of 5'-GMP or 9-EtG binds the cisplatin, thus replacing the "leaving groups" and forming a bisadduct. After 48 h of mixing, the size of the liposomes changes for the mixture of 5'-GMP-embedded liposomes and cisplatin-containing liposomes. We used (1)H and (31)P NMR spectroscopic techniques to monitor incorporation or association of cisplatin and biomolecules with liposomes and their subsequent reactions with each other. The dynamic light scattering technique provided the size distribution of the liposomes in the presence and absence of probe molecules.

Preparation, characterization, and in vitro intestinal permeability evaluation of thalidomide-hydroxypropyl-β-cyclodextrin complexes

Thalidomide is emerging as a therapeutic agent with renewed clinical importance, presenting anti-inflammatory, immunomodulatory, and antineoplasic properties. In this work, we studied the complexation of thalidomide with cyclodextrins as a strategy to circumvent the poor aqueous solubility of the drug. Thalidomide-hydroxypropyl-β-cyclodextrin complexes were obtained by kneading method and were characterized by differential scanning calorimetry, powder X-ray diffractometry, and scanning electronic microscopy. The aqueous solubility and in vitro dissolution of thalidomide were significantly improved through the complexation. Physicochemical analysis of the complexes in solid state revealed a decreased crystallinity of the complexed drug in comparison with free thalidomide. Thalidomide was able to dissociate from the complexes and permeates across intestinal epithelial Caco-2 cells with a favorable high permeability profile equivalent to that of the free drug. In summary, the present results suggest that thalidomide-hydroxypropyl-β-cyclodextrin complexes could be regarded as a promising strategy for improving the gastrointestinal absorption of thalidomide.

In vitro characterization of chitosan gels for buccal delivery of celecoxib: influence of a penetration enhancer

Celecoxib (Cx) shows high efficacy in the treatment of osteoarthritis and rheumatoid arthritis as a result of its high specificity for COX-2, without gastrolesivity or interference with platelet function at therapeutic concentrations. Besides of anti-inflammatory effects, Cx also has a potential role for oral cancer chemoprevention. For these conditions, oral administration in long-term treatment is a concern due to its systemic side effects. However, local application at the site of injury (e.g., buccal inflammation conditions or chemoprevention of oral cancer) is a promising way to reduce its toxicity. In this study, the in vitro characterization of mucoadhesive chitosan (CHT) gels associated to Azone® was assessed to explore the potential buccal mucosal administration of Cx in this tissue. Rheological properties of gels were analyzed by a rheometer with cone-plate geometry. In vitro Cx release and permeability studies used artificial membranes and pig cheek mucosa, respectively. Mucoadhesion were measured with a universal test machine. CHT gels (3.0%) containing 2.0% or 3.0% Az showed more appropriate characteristics compared to the others: pH values, rheology, higher amount of Cx retained in the mucosa, and minimal permeation through mucosa, besides the highest mucoadhesion values, ideal for buccal application. Moreover, the flux (J) and amounts of drug released decreased with increased CHT and Az concentrations. CHT gels (3.0%) associated with 2.0% or 3.0% Az may be considered potential delivery systems for buccal administration of Cx.

Inclusion interaction of chloramphenicol and heptakis (2,6-di-O-methyl)-β-cyclodextrin: phase solubility and spectroscopic methods

The inclusion interaction between chloramphenicol and heptakis (2,6-di-O-methyl)-β-cyclodextrin (DMBCD) had been investigated by phase solubility and spectroscopic methods such as UV-vis spectroscopy, circular dichroism, Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic resonance spectroscopy ((1)H NMR) as well as 2D-ROESY spectra. Phase solubility analysis showed A(L)-type diagram with DMBCD, which suggested the formation of 1:1 inclusion complex of DMBCD with chloramphenicol. The estimated stability constant (K(s)) of the inclusion complex of chloramphenicol with DMBCD is 493 M(-1) at 293 K. The solubility enhancement of chloramphenicol in the presence of DMBCD is stronger than that in the presence of β-CD, HP-β-CD and M-β-CD. The results obtained by spectroscopic methods showed that the nitrophenyl moiety of chloramphenicol is deeply inserted into inner cavity of DMBCD from the narrow rim of DMBCD, which the inclusion model of chloramphenicol with DMBCD differs from that with β-CD.

Nonsteroidal antiinflammatory drug-related injury to the gastrointestinal tract: clinical picture, pathogenesis, and prevention

Increasing life expectancy in developed countries has led to a growing prevalence of arthritic disorders, which has been accompanied by increasing prescriptions for nonsteroidal antiinflammatory drugs (NSAIDs). These are the most widely used agents for musculoskeletal and arthritic conditions. Although NSAIDs are effective, their use is associated with a broad spectrum of adverse reactions in the liver, kidney, cardiovascular system, skin, and gut. Gastrointestinal (GI) side effects are the most common. The dilemma for the physician prescribing NSAIDs is, therefore, to maintain the antiinflammatory and analgesic benefits, while reducing or preventing GI side effects. The challenge is to develop safer NSAIDs by shifting from a focus on GI toxicity to the increasingly more appreciated cardiovascular toxicity.

Complexation of sulfonamides with beta-cyclodextrin studied by experimental and theoretical methods

The complex formation between three structurally related sulfonamides (sulfadiazine (SDZ), sulfamerazine (SMR), and sulfamethazine (SMT)) and beta-cyclodextrin (beta-CD) was studied, by exploring its structure affinity relationship. In all the cases, 1:1 stoichiometries were determined with different relative affinities found by phase solubility (SDZ:beta-CD > SMR:beta-CD > SMT:beta-CD) and nuclear magnetic resonance (NMR) (SMT:beta-CD > SMR:beta-CD > SDZ:beta-CD) studies. The spatial configurations determined by NMR were in agreement with those obtained by molecular modeling, showing that SDZ included its aniline ring into beta-CD, while SMR and SMT included the substituted pyrimidine ring. Energetic analyses demonstrated that hydrophobicity is the main driving force to complex formation.

The role of L-arginine in inclusion complexes of omeprazole with cyclodextrins

In this study, we investigate how the effect of L-arginine (ARG) and cyclodextrins upon omeprazole (OME) stability and solubility. The effect of the presence of ARG on the apparent stability constants (K(1:1)) of the inclusion complexes formed between OME and each cyclodextrin, beta-cyclodextrin (betaCD), and methyl-beta-cyclodextrin (MbetaCD) is studied by phase solubility diagrams and nuclear magnetic resonance (NMR) spectroscopy. The interaction of OME with those cyclodextrins, in the presence of ARG, is characterized using NMR spectroscopy and molecular dynamics simulations. ARG significantly increases the drug solubility and complex stability, in comparison to inclusion complexes formed in its absence. The effect is more pronounced for the OME:betaCD complex. ARG also contributes to a larger stability of OME when free in aqueous solution. The combination of ARG with cyclodextrins can represent an important tool to develop stable drug formulations.