The effects of water-soluble cyclodextrins on the histological integrity of the rat nasal mucosa

Study of Host-Guest Interaction and In Vitro Neuroprotective Potential of Cinnamic Acid/Randomly Methylated β-Cyclodextrin Inclusion Complex

Cinnamic acid (CA) has many beneficial effects on human health. However, its poor water solubility (0.23 g/L, at 25 °C) is responsible for its poor bioavailability. This drawback prevents its clinical use. To overcome the solubility limits of this extraordinary natural compound, in this study, we developed a highly water-soluble inclusion complex of CA with randomly methylated-β-cyclodextrin (RAMEB). The host-guest interaction was explored in liquid and solid states by UV-Vis titration, phase solubility analysis, FT-IR spectroscopy, and 1H-NMR. Additionally, molecular modeling studies were carried out. Both experimental and theoretical studies revealed a 1:1 CA/RAMEB inclusion complex, with a high apparent stability constant equal to 15,169.53 M-1. The inclusion complex increases the water solubility of CA by about 250-fold and dissolves within 5 min. Molecular modeling demonstrated that CA inserts its phenyl ring into the RAMEB cavity with its propyl-2-enoic acid tail leaning from the wide rim. Finally, a biological in vitro study of the inclusion complex, compared to the free components, was performed on the neuroblastoma SH-SY5Y cell line. None of them showed cytotoxic effects at the assayed concentrations. Of note, the pretreatment of SH-SY5Y cells with CA/RAMEB at 10, 30, and 125 µM doses significantly counteracted the effect of the neurotoxin MPP+, whilst CA and RAMEB alone did not show any neuroprotection. Overall, our data demonstrated that inclusion complexes overcome CA solubility problems, supporting their use for clinical applications.

Randomly methylated β-cyclodextrin improves water - solubility, cellular protection and mucosa permeability of idebenone

Neurodegenerative diseases such as Alzheimer's are very common today. Idebenone (IDE) is a potent antioxidant with good potential for restoring cerebral efficiency in cases of these and other medical conditions, but a serious drawback for the clinical use of IDE in neurological disorders lies in its scarce water solubility, which greatly inhibits its bioavailability. In this work, we prepared the inclusion complex of IDE with randomly methylated β-cyclodextrin (RAMEB), resulting in improved water solubility of the included drug; then its in vitro biological activity and ex vivo permeability was evalutated. The solid complex was characterized through FT-IR spectroscopy, Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). A 78-fold improvement of the solubility of IDE in water resulted, together with a strong 1:1 host-guest interaction (association constant of 12630 M-1), and dissolution of the complex within 15 min, all evidenced during the in-solution studies. Biological in vitro studies were then performed on differentiated human neuroblastoma cells (SH-SY5Y) subjected to oxidative stress. Pretreatment with IDE/RAMEB positively affected cell viability, promoted the nuclear translocation of Nrf2, and increased the levels of GSH as well as those of the endogenous antioxidant enzymes Mn-SOD and HO-1. Lastly, the complexation significantly improved the permeation of IDE through isolated rat nasal mucosa.

Screening of Cyclodextrins in the Processing of Buserelin Dry Powders for Inhalation Prepared by Spray Freeze-Drying

Purpose

In this study, we prepared inhalable buserelin microparticles using the spray freeze-drying (SFD) method for pulmonary drug delivery. Raffinose as a cryoprotectant carrier was combined with two levels of five different cyclodextrins (CDs) and then processed by SFD.

Methods

Dry powder diameters were evaluated by laser light scattering and morphology was determined by scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were utilized for the determination of crystalline structures. The aerodynamic properties of the spray freeze-dried powders were evaluated by twin stage impinger (TSI) and the stability of prepared samples was assessed under normal and accelerated conditions.

Results

The prepared powders were mostly porous spheres and the size of microparticles ranged from 9.08 to 13.53 μm, which are suitable as spray-freeze dried particles. All formulations showed amorphous structure confirmed by DSC and XRD. The aerosolization performance of the formulation containing buserelin, raffinose and 5% beta-cyclodextrin (β-CD), was the highest and its fine particle fraction (FPF) was 69.38%. The more circular and separated structures were observed in higher concentrations of CDs, which were compatible with FPFs. The highest stability was obtained in the formulation containing hydroxypropyl beta-cyclodextrin (HP-β-16. CD) 5%. On the contrary, sulfobutylether beta-cyclodextrin (SBE-β-CD) 5% bearing particles showed the least stability.

Conclusion

By adjusting the type and ratio of CDs in the presence of raffinose, the prepared formulations could effectively enhance the aerosolization and stability of buserelin. Therefore, they can be proposed as a suitable career for lung drug delivery.

Spray Freeze-Drying for inhalation application: Process and Formulation Variables

High porous particles with specific aerodynamic properties were processed by the spray freeze-drying (SFD) method. Comprehensive knowledge about all aspects of the SFD method is required for particle engineering of various pharmaceutical products with good flow properties. In this review, different types of the SFD method, the most frequently employed excipients, properties of particles prepared by this method, and most recent approaches concerning SFD are summarized. Generally, this technique can prepare spherical-shaped particles with a highly porous interior structure, responsible for the very low density of powders. Increasing the solubility of spray freeze-dried formulations achieves the desired efficacy. Also, due to the high efficiency of SFD, by determining the different features of this method and optimizing the process by model-based studies, desirable results for various inhaled products can be achieved and significant progress can be made in the field of pulmonary drug delivery.

Versatile Nasal Application of Cyclodextrins: Excipients and/or Actives?

Cyclodextrins (CDs) are oligosaccharides widely used in the pharmaceutical field. In this review, a detailed examination of the literature of the last two decades has been made to understand the role of CDs in nasal drug delivery systems. In nasal formulations, CDs are used as pharmaceutical excipients, as solubilizers and absorption promoters, and as active ingredients due to their several biological activities (antiviral, antiparasitic, anti-atherosclerotic, and neuroprotective). The use of CDs in nasal formulations allowed obtaining versatile drug delivery systems intended for local and systemic effects, as well as for nose-to-brain transport of drugs. In vitro and in vivo models currently employed are suitable to analyze the effects of CDs in nasal formulations. Therefore, CDs are versatile pharmaceutical materials, and due to the continual synthesis of new CDs derivatives, the research on the new nasal applications is an interesting field evolving in the coming years, to which Italian research will still contribute.

In vitro-in vivo correlation in the effect of cyclodextrin on oral absorption of poorly soluble drugs

In this study the concentration effect of 2-Hydroxypropyl-beta-cyclodextrin (HP-βCyD) on oral drug absorption of the BCS class II drugs Danazol (DNZ) and Albendazole (ABZ) was evaluated. In vitro permeation of solutions and suspension systems was compared with their in vivo intestinal absorption in rats and their in vitro-in vivo correlation assessed. In solutions excess amounts of HP-βCyD decreased both in vitro permeation and in vivo absorption due to the decrease in free drug concentration, as expected. However, in suspension systems the contribution of HP-βCyD by drug complexation was found to be altered by further rate limiting steps for membrane permeation and intestinal absorption of each drug. In vitro permeation of DNZ was rate-limited by the diffusion into the unstirred water layer (UWL), while that of ABZ was rate-limited by the permeation across the lipid membrane. For the in vivo intestinal absorption, both drugs were rate-limited by the dissolution rate from undissolved drug. These differences in the rate-limiting process were considered to cause discrepancies in the result of in vitro and in vivo assays. In conclusion, it is quite important to understand the rate limiting process of oral absorption of the target drug for designing oral liquid formulations containing cyclodextrins.

Supramolecular cyclodextrin complex: Diversity, safety, and applications in ocular therapeutics

Approximately 30-70% of the existing and new chemical entities exhibit poor aqueous solubility. For topical ocular delivery, drug molecules need to possess both hydrophilic and lipophilic nature to enable absorption through the aqueous tear layer and permeation through the corneal lipophilic barrier. To overcome the aqueous solubility related issues, various techniques such as solid dispersion, particle size reduction, cyclodextrin complexation, co-solvency, prodrug, derivatization, and salt formation are being explored in the healthcare sector. Cyclodextrin inclusion complexation techniques have been established by several pharmaceutical industries for systemic administration allowing a transition from the lab to the clinics. Though cyclodextrins are exploited in ocular drug delivery, there are prevailing concerns regarding its absorption enhancing capacity and mechanism, retention at the ocular surfaces and, irritation and toxicity profiles. In the present review, the efforts taken by various research groups to address the concerns of using cyclodextrin and its derivatives in ocular therapeutics are summarized. Also, considerations and utility of cyclodextrin systems in fabricating newer formulations such as contact lens, inserts, and implants have been discussed in the review.

Spray-Freeze Drying: a Suitable Method for Aerosol Delivery of Antibodies in the Presence of Trehalose and Cyclodextrins

We aimed to prepare spray-freeze-dried powder of IgG considering physicochemical stability and aerodynamic aspects. Spray-freeze drying (SFD) exposes proteins to various stresses which should be compensated by suitable stabilizers. The competence of cyclodextrins (CDs), namely beta-cyclodextrin (βCD) and hydroxypropyl βCD (HPβCD), at very low concentrations, was investigated in the presence of separate mannitol- and trehalose-based formulations. Spray-freeze-dried preparations were quantified in terms of monomer recovery and conformation by size exclusion chromatography (SEC-HPLC) and Fourier transform infrared (FTIR) spectroscopy, respectively. Differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) were employed to identify the thermal characteristics of powders. Particle morphology was visualized by scanning electron microscopy (SEM). Aerodynamic behavior of powders was checked through an Anderson cascade impactor (ACI). Although all formulations protected antibody from aggregation during the SFD process (aggregation < 1%), mannitol-containing ones failed upon the storage (19.54% in the worst case). Trehalose-HPβCD incomparably preserved the formulation with fine particle fraction (FPF) of 51.29%. Crystallization of mannitol resulted in IgG destabilization upon storage. Although employed concentration of CDs is too low (less than 50:1 molar ratio to protein), they successfully served as stabilizing agents in SFD with perfect improvement in aerosol functionality. Graphical Abstract ᅟ.

Cyclodextrin-Based Formulations: A Non-Invasive Platform for Targeted Drug Delivery

Cyclodextrins (CDs) are recognized as promising pharmaceutical excipients due to their unique ability to form water-soluble inclusion complexes with various poorly soluble compounds. The numerous investigations on CDs and their use in nanomedicine have received considerable attention in the last three decades, leading to the rapid development of new CD-containing formulations that significantly facilitate targeted drug delivery and controlled drug release, with consequent improvements in drug bioavailability. This MiniReview highlights the efficacy and recent uses of CDs for non-invasive drug delivery. Using ophthalmic and nasal drug delivery as examples, an overview of chemical properties, mechanisms of CDs on drug solubilization, stabilization and permeation, along with their toxicological profiles relevant to nasal and ocular administration, are provided and discussed. The recent development and application of CD-based nanocarrier systems for targeted drug delivery are summarized.

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.

Formulation of olfactory-targeted microparticles with tamarind seed polysaccharide to improve nose-to-brain transport of drugs

Targeted delivery and retention of drug formulations in the olfactory mucosa, the target site for nose-to-brain drug absorption is a major challenge due to the geometrical complexity of the nose and nasal clearance. Recent modelling data indicates that 10μm-sized microparticles show maximum deposition in the olfactory mucosa. In the present study we tested the hypothesis that 10μm-sized mucoadhesive microparticles would preferentially deposit on, and increase retention of drug on, the olfactory mucosa in a novel 3D-printed human nasal-replica cast under simulated breathing. The naturally occurring mucoadhesive polymer, tamarind seed polysaccharide (TSP) was used to formulate the microparticles using a spray drying technique. Physicochemical properties of microparticles such as size, morphology and mucoadhesiveness was investigated using a combination of laser diffraction, electron microscopy and texture-analysis. Furthermore, FITC-dextrans (5-40kDa) were incorporated in TSP-microparticles as model drugs. Size-dependent permeability of the FITC-dextrans was observed ex vivo using porcine nasal mucosa. Using the human nasal-replica cast, greater deposition of 10μm TSP-microparticles in the olfactory region was observed compared to TSP-microparticles 2μm in size. Collectively, these findings support our hypothesis that 10μm-sized mucoadhesive microparticles can achieve selective deposition and retention of drug in the olfactory mucosa.

Cyclodextrin complexes for treatment improvement in infectious diseases

Infectious diseases are a heterogeneous group of maladies that represent a serious burden to healthcare systems worldwide. Most of the available antimicrobial drugs display poor biopharmaceutical properties that compromise their effectiveness. Cyclodextrins (CDs) are cyclic oligosaccharides of glucopyranose formed by a variable number of repeating units that combine a hydrophilic surface with a hydrophobic cavity. The production of drug/CD complexes has become one of the most extensively investigated technology approaches to improve the stability, solubility, dissolution rate and bioavailability of drugs. The present work overviews the applications of CDs for the formulation of anti-infective agents along with the most relevant administration routes. Finally, an update on the complexes with CDs available on the market to treat infectious diseases is presented.

A novel nasal powder formulation of glucagon: toxicology studies in animal models

BACKGROUND

Glucagon nasal powder (GNP), a novel intranasal formulation of glucagon being developed to treat insulin-induced severe hypoglycemia, contains synthetic glucagon (10% w/w), beta-cyclodextrin, and dodecylphosphocholine. The safety of this formulation was evaluated in four studies in animal models.

METHODS

The first study evaluated 28-day sub-chronic toxicology in rats treated intranasally with 1 and 2 mg of GNP/day (0.1 and 0.2 mg glucagon/rat/day). The second study evaluated 28-day sub-chronic toxicology in dogs administered 20 and 40 mg of formulation/dog/day (2 and 4 mg glucagon/dog/day) intranasally. A pulmonary insufflation study assessed acute toxicology following intra-tracheal administration of 0.5 mg of GNP (0.05 mg glucagon) to rats. Local tolerance to 30 mg of GNP (equivalent to 3 mg glucagon, the final dose for humans) was tested through direct administration into the eyes of rabbits.

RESULTS

There were no test article-related adverse effects on body weight and/or food consumption, ophthalmology, electrocardiography, hematology, coagulation parameters, clinical chemistry, urinalysis, or organ weights, and no macroscopic findings at necropsy in any study. In rats, direct intra-tracheal insufflation at a dose of 0.5 mg of GNP/rat (0.05 mg glucagon/rat) did not result in adverse clinical, macroscopic, or microscopic effects. In dogs, the only adverse findings following sub-chronic use were transient (<30 s) salivation and sneezing immediately post-treatment and mild to moderate reversible histological changes to the nasal mucosa. Daily dosing over 28 days in rats resulted in mild to moderate, unilateral or bilateral erosion/ulceration of the olfactory epithelium, frequently with minimal to mild, acute to sub-acute inflammation of the lamina propria at the dorsal turbinates of the nasal cavity in 2/10 males and 3/10 females in the high-dose group (0.2 mg glucagon/day). These lesions resolved completely over 14 days. Histological examination of tissues from both sub-chronic studies in dogs and rats revealed no microscopic findings. In rabbits, clinical observations noted in the GNP-treated eye and/or surrounding areas included ≥1 of the following: clear discharge, red conjunctiva, partial closure, and swelling of the peri-orbital area, which correlated with erythema and edema noted during ocular observations and grading.

DISCUSSION

The studies reported here revealed no safety concerns associated with GNP in animal models. Studies published earlier have highlighted the local safety profile of intranasally administered cyclodextrins (a component of GNP). The choline group, the phosphate group, and the saturated 12-carbon aliphatic chain that are present in the dodecylphosphocholine excipient used in GNP are all present in the phospholipids and lecithins seen ubiquitously in mammalian cell membranes and are unlikely to pose safety concerns; this notion is supported by several studies conducted by the authors that revealed no safety concerns. Taken together, these results suggest that intranasal delivery of GNP holds promise as a future rescue medication for use by caregivers to treat insulin-induced hypoglycemic episodes in patients with type 1 or type 2 diabetes.

CONCLUSION

This novel drug product is well tolerated in animal models.

Cyclodextrins, blood-brain barrier, and treatment of neurological diseases

Biological barriers are the main defense systems of the homeostasis of the organism and protected organs. The blood-brain barrier (BBB), formed by the endothelial cells of brain capillaries, not only provides nutrients and protection to the central nervous system but also restricts the entry of drugs, emphasizing its importance in the treatment of neurological diseases. Cyclodextrins are increasingly used in human pharmacotherapy. Due to their favorable profile to form hydrophilic inclusion complexes with poorly soluble active pharmaceutical ingredients, they are present as excipients in many marketed drugs. Application of cyclodextrins is widespread in formulations for oral, parenteral, nasal, pulmonary, and skin delivery of drugs. Experimental and clinical data suggest that cyclodextrins can be used not only as excipients for centrally acting marketed drugs like antiepileptics, but also as active pharmaceutical ingredients to treat neurological diseases. Hydroxypropyl-β-cyclodextrin received orphan drug designation for the treatment of Niemann-Pick type C disease. In addition to this rare lysosomal storage disease with neurological symptoms, experimental research revealed the potential therapeutic use of cyclodextrins and cyclodextrin nanoparticles in neurodegenerative diseases, stroke, neuroinfections and brain tumors. In this context, the biological effects of cyclodextrins, their interaction with plasma membranes and extraction of different lipids are highly relevant at the level of the BBB.

Formulation and evaluation of in situ gelling systems for intranasal administration of gastrodin

Gastrodin is the major bioactive constituent of the traditional Chinese drug "Tianma." It is used in the treatment of some nervous system diseases and can be transported to the brain via intranasal administration. In the current paper, the development of a novel ion-activated in situ gelling system for the nasal delivery of gastrodin is discussed. An in situ perfusion model was used to determine the absorption-rate constant of gastrodin through rat nasal mucosa. The optimal formulation was determined by measuring the critical cation concentration, anti-dilution capacity, gel expansion coefficient, water-holding capacity, and adhesive capacity. The best formulation consisted of 10% gastrodin, 0.5% deacetylated gellan gum as the gelatinizer, and 0.03% ethylparaben as the preservative. The rheological properties of gastrodin nasal in situ gels were also investigated. The viscosity and elasticity sharply increased at temperatures below 25°C. When physiological concentrations of cations were added into the preparation, the mixture gelled into a semi-solid. The results of an accelerated stability test show that gastrodin nasal in situ gels can be stable for more than 2 years. Mucociliary toxicity was evaluated using the in situ toad palate model and the rat nasal mucociliary method; both models demonstrated no measurable ciliotoxicity. Pharmacodynamic studies suggest that similar acesodyne and sedative effects were induced following intranasal administration of 50 mg/kg gastrodin nasal in situ gels or oral administration of 100 mg/kg gastrodin solution. The in situ gel preparation is a safe and effective nasal delivery system for gastrodin.

Evaluation of protein stability and in vitro permeation of lyophilized polysaccharides-based microparticles for intranasal protein delivery

Biocompatible microparticles prepared by lyophilization were developed for intranasal protein delivery. To test for the feasibility of this formulation, stability of the incorporated protein and enhancement of in vitro permeation across the nasal epithelium were evaluated. Lyophilization was processed with hydroxypropylmethylcellulose (HPMC) or water soluble chitosan (WCS) as biocompatible polymers, hydroxypropyl-β-cyclodextrin (HP-β-CD) and d-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS 1000) as permeation enhancers, sugars as cryoprotectants and lysozyme as the model protein. As a result, microparticles ranging from 6 to 12μm were developed where the maintenance of the protein conformation was verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism and fluorescence intensity detection. Moreover, in vitro bioassay showed that the lysozyme activity was preserved during the preparation process while exhibiting less cytotoxicity in primary human nasal epithelial (HNE) cells. Results of the in vitro release study revealed slower release rate in these microparticles compared to that of the lysozyme itself. On the other hand, the in vitro permeation study exhibited a 9-fold increase in absorption of lysozyme when prepared in lyophilized microparticles with HPMC, HP-β-CD and TPGS 1000 (F4-2). These microparticles could serve as efficient intranasal delivery systems for therapeutic proteins.

Comparison of different absorption enhancers on the intranasal absorption of isosorbide dinitrate in rats

The objective of this work was to study the influence of different absorption enhancers on the intranasal absorption of isosorbide dinitrate (ISDN). First of all, an in situ nasal perfusion technique in rats was used to investigate the effect of pH, concentration of drug solution and different absorption enhancers on the intranasal absorption of ISDN. The absorption enhancers investigated include hydroxypropyl-beta-cyclodextrin (HP-beta-CD), chitosans (CS) of different molecular weight, and poloxamer 188. All of them enhanced the intranasal absorption of ISDN remarkably. It was found that poloxamer 188 had better permeation enhancing effect than that of HP-beta-CD and CS of the same concentration. Thereafter, in vivo behaviors of the selected formulations were studied in rats and the pharmacokinetic parameters were calculated and compared with that of intravenous injection. Both in situ and in vivo studies demonstrated that poloxamer 188 played a key role in promoting intranasal absorption of ISDN. In nasal ciliotoxicity test, all the absorption enhancers investigated showed good safety profiles. Taking both enhancing effect and safety into account, we suggest poloxamer 188 is the most promising as an intranasal absorption enhancer.

Cyclodextrins in delivery systems: Applications

Cyclodextrins (CDs) are a family of cyclic oligosaccharides with a hydrophilic outer surface and a lipophilic central cavity. CD molecules are relatively large with a number of hydrogen donors and acceptors and, thus in general, they do not permeate lipophilic membranes. In the pharmaceutical industry, CDs have mainly been used as complexing agents to increase aqueous solubility of poorly soluble drugs and to increase their bioavailability and stability. CDs are used in pharmaceutical applications for numerous purposes, including improving the bioavailability of drugs. Current CD-based therapeutics is described and possible future applications are discussed. CD-containing polymers are reviewed and their use in drug delivery is presented. Of specific interest is the use of CD-containing polymers to provide unique capabilities for the delivery of nucleic acids. Studies in both humans and animals have shown that CDs can be used to improve drug delivery from almost any type of drug formulation. Currently, there are approximately 30 different pharmaceutical products worldwide containing drug/CD complexes in the market.

Nasal administration of metoclopramide from different dosage forms: in vitro, ex vivo, and in vivo evaluation

Nasal drug delivery is an interesting route of administration for metoclopramide hydrochloride (MTC) in preventing different kind of emesis. Currently, the routes of administration of antiemetics are oral or intravenous, although patient compliance is often impaired by the difficulties associated with acute emesis or invasiveness of parenteral administration. In this perspective, nasal dosage forms (solution, gel, and lyophilized powder) of MTC were prepared by using a mucoadhesive polymer sodium carboxymethylcellulose (NaCMC). In vitro and ex vivo drug release studies were performed in a modified horizontal diffusion chamber with cellulose membrane and excised cattle nasal mucosa as diffusion barriers. The tolerance of nasal mucosa to the formulation and its components were investigated using light microscopy. In vivo studies were carried out for the optimized formulations in sheep and the pharmacokinetics parameters were compared with oral solution and IV dosage form. The release of MTC from solution and powder formulations was found to be higher than gel formulation (p < 0.05). Histopathological examination did not detect any severe damage. Hydroxypropyl-beta-cyclodextrin (HPbetaCD) used in powder formulations was found to be effective for enhancing the release and absorption of MTC. In contrast to in vitro and ex vivo experiments nasal bioavailability of gel is higher than those of solution and powder (p < 0.05). In conclusion, the NaCMC gel formulation of MTC with mucoadhesive properties with increased permeation rate is promising for prolonging nasal residence time and thereby nasal absorption.

Intranasal delivery: physicochemical and therapeutic aspects

Interest in intranasal (IN) administration as a non-invasive route for drug delivery continues to grow rapidly. The nasal mucosa offers numerous benefits as a target issue for drug delivery, such as a large surface area for delivery, rapid drug onset, potential for central nervous system delivery, and no first-pass metabolism. A wide variety of therapeutic compounds can be delivered IN, including relatively large molecules such as peptides and proteins, particularly in the presence of permeation enhancers. The current review provides an in-depth discussion of therapeutic aspects of IN delivery including consideration of the intended indication, regimen, and patient population, as well as physicochemical properties of the drug itself. Case examples are provided to illustrate the utility of IN dosing. It is anticipated that the present review will prove useful for formulation scientists considering IN delivery as a delivery route.

Study of the relationship between lipid binding properties of cyclodextrins and their effect on the integrity of liposomes

It is well known that cyclodextrins are able to extract lipids constituting membranes, increasing their fluidity and permeability. This behaviour towards biological membranes is directly linked to the toxicological effects of methylated cyclodextrins. However, confusion is currently made in the literature between the different methylated cyclodextrin derivatives. Moreover, a new methylated cyclodextrin derivative recently occurred in the market, the Crysmeb. We wanted to compare and understand the effect of the most currently used cyclodextrins on a model membrane. We studied the influence of natural cyclodextrins (betaCD and gammaCD), methylated derivatives (2,6-dimethyl-betaCD (Dimeb), 2,3,6-trimethyl-betaCD (Trimeb) and randomly methylated-betaCD (Rameb), as well as the new derivative Crysmeb), hydroxypropylated derivatives (HPbetaCD of different substitution degrees and HPgammaCD) and the sulfobutylated derivative (SBEbetaCD) on the release of a fluorescent marker encapsulated in the inner cavity of liposomes. It was shown that the observed effect on calcein release can be directly related to the affinity of cyclodextrins for both lipid components of liposomes, cholesterol and phosphatidylcholine. From this relationship, we were able to determine, for each cyclodextrin, a theoretical concentration giving rise to 50% or 100% calcein release. This theoretical concentration was confirmed experimentally. We have also showed that cyclodextrins which provoke calcein release also induce large structure modifications of liposomes.

Conjugates of poly(DL-lactic acid) with ethylenediamino or diethylenetriamino bridged bis(beta-cyclodextrin)s and their nanoparticles as protein delivery systems

Some biodegradable amphiphilic copolymers were synthesized by conjugating poly(DL-lactic acid) (PLA) onto ethylenediamino or diethylenetriamino bridged bis(beta-cyclodextrin)s (bis-CDs). Double emulsion (DE) and nanoprecipitation (NP) methods were used to fabricate the nanoparticles of these copolymers entrapping bovine serum albumin (BSA) as a model protein. Effects of the experimental parameters, such as copolymer composition, BSA concentration, copolymer concentration and poly(vinyl alcohol) concentration, on particular size and encapsulation efficiency (EE) were investigated. Their EE to BSA could reach 83.5% at an optimized condition owing to the cooperative binding effect of the CD moiety with BSA. The core-corona structure of copolymer micelles fabricated from the nanoprecipitation was studied on the basis of 1H NMR and other measurements at various temperatures. The results showed that the core-corona structure kept stable below 50 degrees C (lower than Tg). And increase of the micelle association number occurred above the Tg because the size of the NPs became larger and proton signals of the liquid-like PLA cores could be observed in 1H NMR in D2O at 60 degrees C. The release profiles of NPs showed a burst effect followed by a continuous release. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, circular dichroic and fluorescence spectra were further used to identify the stability of BSA released from the NPs. The nanoparticles from the conjugates have a promising potential in nasal delivery system.

Nasal recombinant hirudin-2 delivery: absorption and its mechanism in vivo and in vitro studies

The objective of this study was to investigate the feasibility of systemic absorption of recombinant hirudin-2 (rHV2) by nasal delivery, and its possible absorption mechanism. The degradation of rHV2 in the nasal tissue homogenate and extracts of mucosae of rabbit, as well as the degradation inhibition of enzyme inhibitor (bacitracin) was evaluated. The bioavailability of rHV2 and the improvement with enhancers, after nasal administration in rats was investigated. For further understanding of the transport and uptake characteristics of rHV2, in vitro transport experiment under various conditions using diffusion chamber technique in excised rabbit nasal epithelium was performed. It was found that rHV2 underwent rapid degradation in rabbit nasal homogenate, but it was more stable in the extracts of nasal mucosae surface. Bacitracin was able to inhibit the degradation of rHV2 to certain extent. rHV2 was detected in the rat plasma by chromogenic substrate assay after nasal administration and some enhancers also significantly increased the nasal absorption of rHV2. The transport and uptake of rHV2 across nasal epithelium was concentration-dependent and unsaturated, and was significantly inhibited by low temperature, NaN(3), DNP and colchicines, while was less affected by alteration of transport direction. These results demonstrate that the possible absorption mechanism of rHV2 by nasal mucosa appears to be associated with the endocytosis as well as passive diffusion process.

Lack of effect of β-cyclodextrin and its water-soluble derivatives on in vitro drug transport across rat intestinal epithelium

The present study aimed to investigate whether beta-cyclodetxrin (beta-CD) and its water-soluble derivatives, hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and sulfobutyl ether beta-cyclodextrin (SBE-beta-CD), exert any effects on the permeation of two drug transport markers (propranolol and lucifer yellow) across rat intestinal epithelium. Rat ileum was stripped of its serosa and mounted inside an Ussing Chamber. Apparent permeability coefficients (P(app)) of the markers from the mucosal to serosal side of the tissue were determined at 37 degrees C in the presence and absence of the beta-cyclodextrins on the mucosal side. Potential difference (PD) was constantly monitored during each experiment to ensure maintenance of the viability and integrity of the tissue. Pre-incubation with 1% beta-CD, 1% HP-beta-CD or 1.48% SBE-beta-CD on the mucosal side for 30 min did not significantly alter the PD and the propranolol permeability (p>0.05). Co-incubation with 1% beta-CD or 1% HP-beta-CD exerted no significant effect on the P(app) of both propranolol and lucifer yellow (p>0.05), but co-incubation with 1.48% SBE-beta-CD lowered the P(app) of propranolol from (1.71+/-0.44)x10(-5) to (0.19+/-0.04)x10(-5)cm/s, which may be ascribed to the molecular complexation of propranolol with SBE-beta-CD. All three beta-cyclodextrins exert no apparent impact on both (passive) transcellar and paracellular drug transports.

Cholesterol and synaptic transmitter release at crayfish neuromuscular junctions

During exocytosis of synaptic transmitters, the fusion of highly curved synaptic vesicle membranes with the relatively planar cell membrane requires the coordinated action of several proteins. The role of membrane lipids in the regulation of transmitter release is less well understood. Since it helps to control membrane fluidity, alteration of cholesterol content may alter the fusibility of membranes as well as the function of membrane proteins. We assayed the importance of cholesterol in transmitter release at crayfish neuromuscular junctions where action potentials can be measured in the preterminal axon. Methyl-beta-cyclodextrin (MbetaCD) depleted axons of cholesterol, as shown by reduced filipin labelling, and cholesterol was replenished by cholesterol-MbetaCD complex (Ch-MbetaCD). MbetaCD blocked evoked synaptic transmission. The lack of postsynaptic effects of MbetaCD on the time course and amplitude of spontaneous postsynaptic potentials or on muscle resting potential allowed us to focus on presynaptic mechanisms. Intracellular presynaptic axon recordings and focal extracellular recordings at individual boutons showed that failure of transmitter release was correlated with presynaptic hyperpolarization and failure of action potential propagation. All of these effects were reversed when cholesterol was replenished with Ch-MbetaCD. However, focal depolarization of presynaptic boutons and administration of a Ca2+ ionophore both triggered transmitter release after cholesterol depletion. Therefore, both presynaptic Ca2+ channels and Ca2+-dependent exocytosis functioned after cholesterol depletion. The frequency of spontaneous quantal transmitter release was increased by MbetaCD but recovered when cholesterol was reintroduced. The increase in spontaneous release was not through a calcium-dependent mechanism because it persisted with intense intracellular calcium chelation. In conclusion, cholesterol levels in the presynaptic membrane modulate several key properties of synaptic transmitter release.

Cyclodextrins in nasal delivery of low-molecular-weight heparins: in vivo and in vitro studies

PURPOSE

To test the hypothesis that cyclodextrins reversibly enhance nasal absorption of low-molecular-weight heparins (LMWHs) and to investigate the mechanisms by which cyclodextrins enhance LMWH absorption via the nose.

METHODS

Absorption of LMWHs was studied by measuring plasma anti-factor Xa activity after nasal administration of various LMWH formulations to anesthetized rats. In vivo reversibility studies were performed to investigate if the effects of cyclodextrins are reversible and diminish with time. The absorption-enhancing mechanisms of cyclodextrins were investigated in cell culture model. The transport of enoxaparin and mannitol, changes in transepithelial electrical resistance (TEER), and distribution of tight junction protein ZO-1 were investigated.

RESULTS

Formulations containing 5% dimethyl-beta-cyclodextrin (DMbetaCD) produced the highest increase in the bioavailability of LMWH preparations tested. In vivo reversibility studies with 5% DMbetaCD showed that the effect of the absorption enhancer at the site of administration diminished with time. Transport studies using 16HBE14o(-) cells demonstrated that the increase in the permeability of enoxaparin and mannitol, reduction in TEER, and the changes in the tight junction protein ZO-1 distribution produced by 5% DMbetaCD were much greater than those produced by beta-cyclodextrin (betaCD) or hydroxyl-propyl-beta-cyclodextrin (HPbetaCD).

CONCLUSIONS

Of the cyclodextrins tested, DMbetaCD was the most efficacious in enhancing absorption of LMWHs both in vivo and in vitro. The study also suggests that cyclodextrins enhance nasal drug absorption by opening of cell-cell tight junctions.