Biomembrane model interaction and percutaneous absorption of papaverine through rat skin: effects of cyclodextrins as penetration enhancers

Absorption enhancer approach for protein delivery by various routes of administration: a rapid review

As bioactive molecules, peptides and proteins are essential in living organisms, including animals and humans. Defects in their function lead to various diseases in humans. Therefore, the use of proteins in treating multiple diseases, such as cancers and hepatitis, is increasing. There are different routes to administer proteins, which have limitations due to their large and hydrophilic structure. Another limitation is the presence of biological and lipophilic membranes that do not allow proteins to pass quickly. There are different strategies to increase the absorption of proteins from these biological membranes. One of these strategies is to use compounds as absorption enhancers. Absorption enhancers are compounds such as surfactants, phospholipids and cyclodextrins that increase protein passage through the biological membrane and their absorption by different mechanisms. This review focuses on using other absorption enhancers and their mechanism in protein administration routes.

Nano-Spray-Dried Levocetirizine Dihydrochloride with Mucoadhesive Carriers and Cyclodextrins for Nasal Administration

Antihistamines such as levocetirizine dihydrochloride (LC) are commercially used in oral tablets and oral drops to reduce allergic symptoms. In this study, LC was nano-spray-dried using three mucoadhesive polymers and four cyclodextrin species to form composite powders for nasal administration. The product was composed of hydroxypropyl methylcellulose polymer, including LC as a zwitterion, after neutralization by NaOH, and XRD investigations verified its amorphous state. This and a sulfobutylated-beta-cyclodextrin sodium salt-containing sample showed crystal peaks due to NaCl content as products of the neutralization reaction in the solutions before drying. The average particle size of the spherical microparticles was between 2.42 and 3.44 µm, except for those containing a polyvinyl alcohol excipient, which were characterized by a medium diameter of 29.80 µm. The drug was completely and immediately liberated from all the samples at pH 5.6 and 32 °C; i.e., the carriers did not change the good dissolution behavior of LC. A permeability test was carried out by dipping the synthetic cellulose ester membrane in isopropyl myristate using modified horizontal diffusion cells. The spray-dried powder with β-cyclodextrin showed the highest permeability (188.37 µg/cm²/h), as this additive was the least hydrophilic. Products prepared with other cyclodextrins (randomly methylated-beta-cyclodextrin, sulfobutylated-beta-cyclodextrin sodium salt and (hydroxypropyl)-beta-cyclodextrin) showed similar or slightly higher penetration abilities than LC. Other polymer excipients resulted in lower penetration of the active agent than the pure LC.

Physicochemical Characterization and Antioxidant Activity Evaluation of Idebenone/Hydroxypropyl-β-Cyclodextrin Inclusion Complex †

Idebenone (IDE) is an antioxidant drug active at the level of the central nervous system (CNS), whose poor water solubility limits its clinical application. An IDE/2-hydroxypropyl-β-cyclodextrin (IDE/HP-β-CD) inclusion complex was investigated by combining experimental methods and theoretical approaches. Furthermore, biological in vitro/ex vivo assays were performed. Phase solubility studies showed an A_L type diagram, suggesting the presence of a 1:1 complex with high solubility. Scanning electron microscopy (SEM) allowed us to detect the morphological changes upon complexation. The intermolecular interactions stabilizing the inclusion complex were experimentally characterized by exploring the complementarity of Fourier-transform infrared spectroscopy in attenuated total reflectance geometry (FTIR-ATR) with mid-infrared light, Fourier-transform near-infrared (FT-NIR) spectroscopy, and Raman spectroscopy. From the temperature evolution of the O–H stretching band of the complex, the average enthalpy ΔH_HB of the hydrogen bond scheme upon inclusion was obtained. Two-dimensional (2D) rotating frame Overhauser effect spectroscopy (ROESY) analysis and computational studies involving molecular modeling and molecular dynamics (MD) simulation demonstrated the inclusion of the quinone ring of IDE inside the CD ring. In vitro/ex vivo studies evidenced that complexation produces a protective effect of IDE against the H₂O₂-induced damage on human glioblastoma astrocytoma (U373) cells and increases IDE permeation through the excised bovine nasal mucosa.

Strategies to Enhance Drug Absorption via Nasal and Pulmonary Routes

New therapeutic agents such as proteins, peptides, and nucleic acid-based agents are being developed every year, making it vital to find a non-invasive route such as nasal or pulmonary for their administration. However, a major concern for some of these newly developed therapeutic agents is their poor absorption. Therefore, absorption enhancers have been investigated to address this major administration problem. This paper describes the basic concepts of transmucosal administration of drugs, and in particular the use of the pulmonary or nasal routes for administration of drugs with poor absorption. Strategies for the exploitation of absorption enhancers for the improvement of pulmonary or nasal administration are discussed, including use of surfactants, cyclodextrins, protease inhibitors, and tight junction modulators, as well as application of carriers such as liposomes and nanoparticles.

Physicochemical properties of inclusion complexes of highly soluble β-cyclodextrins with highly hydrophobic testosterone propionate

Hydroxypropyl-β-cyclodextrin (HP-β-CyD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CyD) were used to generate hydrophilic complexes of the poorly water-soluble drug testosterone propionate (TP). The inclusion complexes were obtained by freeze-drying, and then analyzed at both liquid and solid states. Phase solubility studies, performed according to the type-A_L solubility diagrams of TP in presence of both CyDs, suggested the formation of water-soluble complexes at 1:1 molar ratio. These results were confirmed by continuous variation method (Job's plot). Both CyDs increased water-solubility of TP 100-fold as compared to the native drug. The host-guest arrangement of CyD complexes in a water solution was further investigated by one- and two-dimensional NMR spectroscopy, highlighting the insertion of the tetracyclic ring of TP into the CyD cavity, and the interaction of the pending ester chain of drug with the primary hydroxyl groups of CyDs at the narrow end of the toroid structure. In solid phase, FTIR-ATR spectroscopy showed that the CO stretching mode of the TP vibrational spectrum changed if the complex between the drug and CyDs occurred. This change is temperature-dependent, and its evolution, accounted for by deconvolution procedures, provided the thermodynamic parameters explaining the mechanisms involved in the formation of inclusion complexes.

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.

[In-vitro evaluation of cinnarizine as a competing agent to beta-cyclodextrin inclusion complexes: effect of cinnarizine on the membrane permeation rate of progesterone from its beta-cyclodextrin inclusion complex]

The use of competing agents is considered a powerful tool for the development of a drug-delivery system with drug/cyclodextrin inclusion complexes. However, there are very few studies examining this issue. To explain this phenomenon, it was thought that a competing agent with a sufficiently high stability constant had not yet been reported. In this study, cinnarizine (CN), which has a high stability constant with beta-cyclodextrin (beta-CD) and unique solubility characteristics, was selected, and its ability as a competing agent was examined in a membrane permeability study. The permeability study showed that the permeation rates of the drugs flurbiprofen, progesterone, and spironolactone decreased with their stability constants with the addition of beta-CD. In one of the drugs, progesterone (Pro), the decrease was restored by the addition of CN. The amount of CN added was a 1:1 molar ratio to the amount of Pro. However, no similar action was induced with the addition of DL-phenylalanine (Phe) in the permeation study at the 1:5 (Pro:Phe) molar ratio. These finding indicate that CN acts as a competing agent, and its action is much stronger than that of Phe.

Overcoming the Stratum Corneum: The Modulation of Skin Penetration

It is preferred that topically administered drugs act either dermally or transdermally. For that reason they have to penetrate into the deeper skin layers or permeate the skin. The outermost layer of the human skin, the stratum corneum, is responsible for its barrier function. Most topically administered drugs do not have the ability to penetrate the stratum corneum. In these cases modulations of the skin penetration profiles of these drugs and skin barrier manipulations are necessary. A skin penetration enhancement can be achieved either chemically, physically or by use of appropriate formulations. Numerous chemical compounds have been evaluated for penetration-enhancing activity, and different modes of action have been identified for skin penetration enhancement. In addition to chemical methods, skin penetration of drugs can be improved by physical options such as iontophoresis and phonophoresis, as well as by combinations of both chemical and physical methods or by combinations of several physical methods. There are cases where skin penetration of the drug used in the formulation is not the aim of the topical administration. Penetration reducers can be used to prevent chemicals entering the systemic circulation. This article concentrates on the progress made mainly over the last decade by use of chemical penetration enhancers. The different action modes of these substances are explained, including the basic principles of the physical skin penetration enhancement techniques and examples for their application.

Influence of modified cyclodextrins on solubility and percutaneous absorption of celecoxib through human skin

We evaluated the ability of two modified cyclodextrins, hydroxypropyl-beta-cyclodextrin (HP-beta-Cyd) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-Cyd), to influence the percutaneous absorption through isolated human stratum corneum and epidermis (SCE) of celecoxib (CCB). Previous studies demonstrated that DM-beta-Cyd includes the drug, producing a significant increase of water solubility (0.5 mg/ml at 25 degrees C) and dissolution rate of CCB. In this work chemical-physical characterization studies were performed to evaluate the ability of HP-beta-Cyd to include CCB. We showed that only an external interaction could exist between CCB and HP-beta-Cyd that positively influences the water solubility of the drug (0.12 mg/ml at 25 degrees C for CCB-HP-beta-CyD system and 4.12 x 10(-3) mg/ml at 25 degrees C for free CCB). In vitro percutaneous experiments were performed using samples in solution and in suspension containing different Cyd concentrations. Both HP-beta-Cyd and DM-beta-Cyd enhanced drug flux through SCE by means of an increase of dissolution rate of the drug as well as a direct action on the stratum corneum (SC). Histological analysis of treated SCE showed a protective effect of the two Cyds towards an invasive action shown by CCB on SC.

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

The ability of 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-Cyd) to include the anti-inflammatory drug celecoxib (CCB) was evaluated. The complex was prepared by kneading and freeze-drying methods and was characterized in the solid state and in aqueous solution. Water solubility and dissolution rate of CCB, in a medium simulating gastric fluid, significantly increased after complexation, with complete dissolution obtained after 30 and 180 min for the freeze-dried and kneaded complexes respectively. Phase solubility studies showed Ap-type diagrams. Stability constants for the 1:1 and 1:2 CCB-DM-beta-Cyd complexes and (1)H-NMR studies suggested a probable 1:1 inclusion complex and only an external interaction for the second Cyd molecule. Thermodynamic parameters of the binding process showed the existence of van der Waals forces between CCB and DM-beta-Cyd. DM-beta-Cyd influenced the permeation of CCB through the CaCo-2 cells monolayer. The increase of permeation observed was due to the fast dissolution rate of the included drug and to a destabilizing action exerted by the macrocycle on the biomembrane.

Combining NMR and molecular modelling in a drug delivery context: investigation of the multi-mode inclusion of a new NPY-5 antagonist bromobenzenesulfonamide into β-cyclodextrin

NMR spectroscopic and molecular modelling methods have been employed to describe the complexation of trans-N-4-[N'-(4-chlorobenzoyl)hydrazinocarbonyl]cyclohexylmethyl-4-bromobenzenesulfonamide, a new chemotype of NPY-5 antagonist, and beta-cyclodextrin, revealing the coexistence of two different kinds of 1:1 complexes where conformational changes of the guest compound with respect to the free state are also detected.

Preparation, characterization, molecular modeling and in vitro activity of paclitaxel-cyclodextrin complexes

Paclitaxel (PTX) was complexed with beta-cyclodextrin (1), 2,6-dimethyl-beta-cyclodextrin (2) and 2,3,6-trimethyl-beta-cyclodextrin (3). PTX-CYD complexes were characterized both at the solid and liquid states. Experimental findings are in agreement with molecular modeling analysis, which showed different PTX-CYD interaction as a function of macrocyle methylation. The complexation of PTX within the CYD cavity preserved its antitumoral activity.