Melarsoprol–cyclodextrins inclusion complexes

Preparation, Characterization, and Antioxidant Activity of L-Ascorbic Acid/HP-β-Cyclodextrin Inclusion Complex-Incorporated Electrospun Nanofibers

L-Ascorbic acid (LAA) is a key vitamin, implicated in a variety of physiological processes in humans. Due to its free radical scavenging activity, it is extensively employed as an excipient in pharmaceutical products and food supplements. However, its application is greatly impeded by poor thermal and aqueous stability. Herein, to improve the stability and inhibit oxidative degradation, we prepared LAA-cyclodextrin inclusion complex-incorporated nanofibers (NFs). The continuous variation method (Job plot) demonstrated that LAA forms inclusions with hydroxypropyl-β-cyclodextrin (HP-β-CD) at a 2:1 molar stoichiometric ratio. The NFs were prepared via the single step electrospinning technique, without using any polymer matrix. The solid-state characterizations of LAA/HP-β-CD-NF via powder x-ray diffractometry (PXRD), Fourier-transform infrared (FT-IR) analysis, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and nuclear magnetic resonance (¹H NMR and 2D-NOESY) spectroscopy, reveal the effective encapsulation of the LAA (guest molecule) inside the HP-β-CD (host) cavity. The SEM micrograph reveals an average fiber diameter of ~339 nm. The outcomes of the thermal investigations demonstrated that encapsulation of LAA within HP-β-CD cavities provides improved thermal stability of LAA (by increasing the thermal degradation temperature). The radical scavenging assay demonstrated the enhanced antioxidant potential of LAA/HP-β-CD-NF, as compared to native LAA. Overall, the study shows that cyclodextrin inclusion complex-incorporated NFs, are an effective approach for improving the limitations associated with LAA, and provide promising avenues in its therapeutic and food applications.

Delivery of melarsoprol using folate-targeted PEGylated cyclodextrin-based nanoparticles for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer, and has become one of the most lethal malignancies in the world. Although chemotherapy remains a cornerstone of cancer therapy, the number of chemotherapeutic drugs approved for HCC is low, and emerging therapeutics are needed. Melarsoprol (MEL) is an arsenic-containing drug, and has been applied in the treatment of human African trypanosomiasis at the late stage. In this study, the potential of MEL for HCC therapy was investigated for the first time using in vitro and in vivo experimental approaches. A folate-targeted polyethylene glycol-modified amphiphilic cyclodextrin nanoparticle was developed for safe, efficient and specific delivery of MEL. Consequently, the targeted nanoformulation achieved cell-specific uptake, cytotoxicity, apoptosis and migration inhibition in HCC cells. Furthermore, the targeted nanoformulation significantly prolonged the survival of mice with orthotopic tumor, without causing toxic signs. This study indicates the potential of the targeted nanoformulation as an emerging chemotherapy option for treating HCC.

Designing a Formulation of the Nootropic Drug Aniracetam Using 2-Hydroxypropyl-β-Cyclodextrin Suitable for Parenteral Administration

The nootropic drug aniracetam is greatly limited in its application by low aqueous solubility and a poor oral bioavailability. The primary aim of this study was to design a parenteral formulation of aniracetam that can be administered intravenously. Complexation of aniracetam with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated as a strategy to enhance solubility. A phase solubility analysis was performed to quantify the extent of improvement. An 819% increase in the solubility of aniracetam was obtained, reaching 36.44 mg/mL. This marked increase enables aniracetam to exist in an aqueous solvent at levels sufficient for parenteral dosing. A stability test was then devised using a design of experiment approach. The aniracetam-HP-β-CD formulation was subjected to different relative humidity and temperature and cyclodextrin concentrations over a 12-week period. Key changes in FTIR vibrational frequencies suggest the benzene moiety of aniracetam was introduced into the hydrophobic cavity of HP-β-CD. These results are highly supportive of the formation of a predictable 1:1 molar stoichiometric inclusion complex, explaining the improvement seen in physiochemical properties of aniracetam following formulation with HP-β-CD. This novel formulation of aniracetam suitable for parenteral administration will have utility in future studies to further elucidate the pharmacokinetics of this drug.

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.

Effects of cyclodextrins on the chemical stability of drugs

Cyclodextrins (CDs) are enabling pharmaceutical excipients that can enhance both solubility and stability of wide variety of drugs in aqueous solutions through formation of drug/CD inclusion complexes where apolar moieties of the drug molecules are located inside the CD cavity. In properly designed pharmaceutical formulations CDs will improve physiochemical properties of lipophilic drugs without affecting their intrinsic ability to permeate biological membranes. Here the effect of CD complexes on the chemical stability of drugs is reviewed. Numerous studies shown that in aqueous solutions CD complexation can hamper hydrolysis, oxidation, photodegradation, isomerization and enzyme catalyzed degradation of dissolved drugs. However, some drugs, such as β-lactam antibiotics, can under certain conditions undergo CD catalyzed degradation in aqueous solutions. Also, some drugs that are stabilized by CDs in aqueous solutions are destabilized by the same CDs in solid dosage forms. Thus, the effects of CDs on drug stability have to be tested and verified in the final drug formulation and under the recommended storage conditions.

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.

Pharmacokinetics of cyclodextrins and drugs after oral and parenteral administration of drug/cyclodextrin complexes

Objectives

The objective of the present study was to shed some light on pharmacokinetics of cyclodextrins (CDs) and drugs after oral and parenteral administration of inclusion complexes.

Key findings

The complex binding constant in water can predict pharmacokinetics after parenteral administration, but it has to be considered in the context of the physiological environment, where plasma proteins compete with CDs for drug binding. Neither drug/CD nor drug/protein complexes can extravasate, but differently from proteins, CDs are readily cleared through glomerular filtration. In such intricate interrelationships, for complexes with low-to-mid binding constant, binding of drug to plasma proteins will mainly dictate the pharmacokinetics. Oppositely, for drugs showing large CD complex binding constant and low protein binding, significant decrease in distribution volume and enhanced excretion of unmetabolized drug are observed; thus, relevant changes in bioavailability can be predicted. In the case of oral administration, volume for dilution/dissolution of the complexes is relatively low and hence excess CD can hamper drug absorption from the gastrointestinal (GI) tract.

Summary

CDs are well-established multipurpose excipients for overcoming organoleptic and biopharmaceutical deficiencies of a variety of drugs. Balances between free and complexed drug in the GI tract and between drug–CD binding and drug–protein binding in plasma seem to play a relevant role in drug pharmacokinetics.

Cyclodextrin and phospholipid complexation in solubility and dissolution enhancement: a critical and meta-analysis

INTRODUCTION

Poor solubility and dissolution of drugs are the major challenges in drug formulation and delivery. In order to improve the solubility and dissolution profile of drugs, various methods have been investigated so far. The cyclodextrin (CD) complexation and phospholipid (PL) complexation are among the exhaustively investigated methods employed for more precise improvement of the solubility and dissolution of poorly water-soluble drugs.

AREAS COVERED

The article discusses the CD and PL complexation techniques of solubility and dissolution enhancement. Various studies reporting the CD and PL complexation as the potential approaches to improve the dissolution, absorption and the bioavailability of the drugs have been discussed. The article critically reviews the physicochemical properties of CDs and PLs, eligibility of drugs for both the complexation, thermodynamics of complexation, methods of preparation, characterization, advantages, limitation and the meta-analysis of some studies for both the techniques.

EXPERT OPINION

The CD and PL complexation techniques are very useful in improving solubility and dissolution (and hence the bioavailability) of biopharmaceutical classification system Class II and Class IV drugs. The selection of a particular kind of complexation can be made on the basis of eligibility criteria (of drugs) for the individual techniques, cost, stability and effectiveness of the complexes.

A characterization study of resveratrol/sulfobutyl ether-β-cyclodextrin inclusion complex and in vitro anticancer activity

A resveratrol/sulfobutylether-β-cyclodextrin inclusion complex was prepared using the freeze-drying method and characterized in solution through UV-vis spectroscopy, solubility phase studies and Job's plot methods. At the solid state it was characterized using the FTIR-ATR technique. Sulfobutylether-β-cyclodextrin has a high affinity for the drug, and forms an inclusion complex with a 1:1 molar ratio both in solution and as a solid sample. It also has a high stability constant (Kc, 10,114 M(-1)). Complexation strongly increases the water solubility of resveratrol (from 0.03 mg/ml to 1.1 mg/ml, at 25 °C) and positively influences its in vitro anticancer activity which was observed on a human breast cancer cell line (MCF-7). In solid phase, FTIR-ATR revealed itself as being a useful technique in elucidating the complexation mechanism, which it did by emphasizing the functional groups involved in the activation of non-covalent "host-guest" interactions.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Characterization of mitotane (o,p'-DDD)--cyclodextrin inclusion complexes: phase-solubility method and NMR

Mitotane (o,p'-dichlorodimethyl dichloroethane [o,p'-DDD]) is used for the treatment of adrenocortical cancer and occasionally Cushing's syndrome. This drug is very poorly soluble in water, and following oral administration, approximately 60% of the dose is recovered in the feces unaltered. The preparation of a soluble formulation (i.e. by complexation with cyclodextrins) with improved bioavailability is the aim of this work. The inclusion of mitotane in methyl-ß-cyclodextrins was studied using both phase-solubility methods and NMR experiments. To elucidate the inclusion mechanism, o,p'-DDD was compared to its regioisomer (i.e. p,p'-DDD). It was demonstrated that two dimethyl-ß-cyclodextrins (DMßCD) can complex with the aromatic rings. From the phase-solubility diagrams, we observe that both cases are very different: K(1:1) is between 37 000 and 85 000 mol.l(-1), whereas K(1:2) is between 5.3 and 32 mol.l(-1). The NMR experiments confirmed the inclusion but it also gave an insight into the kinetics of the dissociation: the ortho-chloro moiety is in slow exchange on the NMR time scale, whereas the para-chloro moiety is in fast exchange rate.

Molecular modeling-based inclusion mechanism and stability studies of doxycycline and hydroxypropyl-β-cyclodextrin complex for ophthalmic delivery

The aim of the present study was to prepare a stable complex of doxycycline (Doxy) and hydroxypropyl-β-cyclodextrin (HPβCD) for ophthalmic delivery and investigate the inclusion mechanism and the inclusion effects on the stability of Doxy. The Doxy/HPβCD complex was prepared by solution stirring and then characterized by scanning electron microscopy and ultraviolet spectroscopy. Based on results of nuclear magnetic resonance, molecular model of Doxy/HPβCD complex was established using computational simulation of PM3 method implemented in Gaussian 03. Stabilities of Doxy/HPβCD complex in both aqueous solution and solid state at 25°C were evaluated by HPLC. Finally, in vitro antibacterial activity of the Doxy/HPβCD complex was evaluated by disk diffusion test. It was found that the stabilities of Doxy/HPβCD complex in both aqueous solution and solid state were improved obviously as compared with Doxy alone. This stability enhancement is consistent with the inclusion mechanism between HPβCD and Doxy, which showed that the unstable site of Doxy molecule at 6-CH3 was protected in the hydrophobic cavity of HPβCD, additionally, the chelation of Mg2+ provided a synergetic protection of the other unstable site of Doxy at 4-N(CH3)2. The antibacterial activity results indicated that Doxy/HPβCD complex might have potential for clinical applications.

Spectroscopic investigation on the inclusion complex formation between amisulpride and γ-cyclodextrin

The purpose of this research was to investigate inclusion complex formation between poorly soluble drug amisulpride (AMI) and γ-cyclodextrin (γ-CD). The solubility of AMI was enhanced by formation of inclusion complex of AMI with nano-hydrophobic cavity of γ-CD. The stoichiometry of inclusion complex was studied by continuous variation Job's plot method and found 1:1. The binding constant was found 1166.65 M(-1) by Benesi-Hildebrand plot. The molecular docking of AMI and γ-CD was done to investigate complexation. The inclusion complex formation was further confirmed by (1)H NMR and FT-IR, DSC and XRD analysis. The solubility of AMI was increased 3.74 times after inclusion complex formation with γ-CD.

Melarsoprol cyclodextrin inclusion complexes as promising oral candidates for the treatment of human African trypanosomiasis

Human African trypanosomiasis (HAT), or sleeping sickness, results from infection with the protozoan parasites Trypanosoma brucei (T. b.) gambiense or T. b. rhodesiense and is invariably fatal if untreated. There are 60 million people at risk from the disease throughout sub-Saharan Africa. The infection progresses from the haemolymphatic stage where parasites invade the blood, lymphatics and peripheral organs, to the late encephalitic stage where they enter the central nervous system (CNS) to cause serious neurological disease. The trivalent arsenical drug melarsoprol (Arsobal) is the only currently available treatment for CNS-stage T. b. rhodesiense infection. However, it must be administered intravenously due to the presence of propylene glycol solvent and is associated with numerous adverse reactions. A severe post-treatment reactive encephalopathy occurs in about 10% of treated patients, half of whom die. Thus melarsoprol kills 5% of all patients receiving it. Cyclodextrins have been used to improve the solubility and reduce the toxicity of a wide variety of drugs. We therefore investigated two melarsoprol cyclodextrin inclusion complexes; melarsoprol hydroxypropyl-β-cyclodextrin and melarsoprol randomly-methylated-β-cyclodextrin. We found that these compounds retain trypanocidal properties in vitro and cure CNS-stage murine infections when delivered orally, once per day for 7-days, at a dosage of 0.05 mmol/kg. No overt signs of toxicity were detected. Parasite load within the brain was rapidly reduced following treatment onset and magnetic resonance imaging showed restoration of normal blood-brain barrier integrity on completion of chemotherapy. These findings strongly suggest that complexed melarsoprol could be employed as an oral treatment for CNS-stage HAT, delivering considerable improvements over current parenteral chemotherapy.

Bioadhesive microspheres for bioavailability enhancement of raloxifene hydrochloride: formulation and pharmacokinetic evaluation

Raloxifene hydrochloride (R-HCl), a BCS class II drug, remains a mainstay in the prevention and pharmacologic therapy of osteoporosis. Its absolute bioavailability, however, is 2% due to poor solubility and extensive first pass metabolism. The present study describes two simultaneous approaches to improve its bioavailability, complexation of R-HCl with cyclodextrin(s), and formulation of mucoadhesive microspheres of the complex using different proportions of carbopol and HPMC. Microspheres were pale yellow in color, free-flowing, spherical, and porous in outline. The particle size ranged between 3 and 15 μm, and entrapment efficiency was found to be within 81.63% to 87.73%. A significant improvement in the solubility of R-HCl was observed, and it differed with the combination of excipients used. X-ray diffraction and differential scanning calorimetry studies revealed that enhancement in drug solubility was resulted due to a change in its crystallinity within the formulation. Microspheres possessed remarkable mucoadhesion and offered controlled drug release, lasting up to 24 h. They produced a sharp plasma concentration-time profile of R-HCl within 30 min post-administration to Wistar rats. [AUC](0-24 h) was found to be 1,722.34 ng h/ml, and it differed significantly to that of pure drug powder (318.28 ng h/ml). More than fivefold increase in AUC and more than twofold increase in MRT were observed. FT-IR studies evidenced no interaction among drug and excipients. The results of this study showed that mucoadhesive microspheres could be a viable approach to improve the pharmacokinetic profile of R-HCl.

Effects of K openers on the QT prolongation induced by HERG-blocking drugs in guinea-pigs

OBJECTIVES

This work evaluated the potential usefulness of pharmacological activation of cardiac ATP-sensitive potassium channels (K(ATP)) in the prevention of drug-induced QT prolongation in anaesthetised guinea-pigs. Prolongation of cardiac repolarisation and QT interval is an adverse effect of many drugs blocking HERG potassium channels. This alteration can be dangerously arrhythmogenic and has been associated with the development of a particular form of ventricular tachyarrhythmia known as torsade de pointes.

METHODS

The well-known K(ATP) openers aprikalim, cromakalim and pinacidil were used. Moreover, three benzothiazine derivatives, which have been reported as potent activators of K(ATP) channels, were also used.

KEY FINDINGS

Pharmacological activation of K(ATP) channels caused a reduction of the QT prolongation, induced by astemizole, cisapride, quinidine and thioridazine. In contrast, the QT prolongation induced by haloperidol, sotalol and terfenadine, which are known to block HERG channels but also K(ATP) channels, was not influenced by K(ATP) activation. Glibenclamide and tolbutamide (non-selective blockers of K(ATP) channels expressed both in sarcolemmal and in mitochondrial membranes) antagonised the effects of K(ATP) openers, whereas 5-hydroxydecanoic acid (selective blocker of the mitochondrial K(ATP) channels) failed to antagonise the effects of K(ATP) openers, indicating that only the sarcolemmal K(ATP) is involved in the cardioprotective activity.

CONCLUSIONS

The data suggest that pharmacological K(ATP) activation might represent an option for treatment of patients exposed to QT-prolonging drugs.

Complexation study of the anticancer agent EO-9 with 2-hydroxypropyl-beta-cyclodextrin

For the development of a bladder instillation of the indoloquinone agent EO-9, use of the complexing agent 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD) was considered. Therefore, a complexation study of EO-9 with HPbetaCD was performed. Complexation was studied in aqueous solution and in solid freeze-dried products. A phase solubility study, UV-visible spectroscopy (UV/VIS), and analysis of the effect of HPbetaD on the stability of EO-9 were performed. With the phase solubility study, a complexation constant (K1:1) of 32.9, a complexation efficiency (CE) of 0.0457, and a utility number (UCD) of 38.3 were calculated. These K1:1 and CE values indicate a weak complex, but the UCD shows that HPbetaCD can be very useful as solubilizer in the desired formulation. Furthermore, a positive effect of HPbetaCD on the chemical stability of EO-9 in solution was seen. Subsequently, complexation in the freeze-dried products was studied more thoroughly using Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. HPbetaCD was found to be an excellent pharmaceutical complexing agent for application in formulations for EO-9 bladder instillations. Reconstitution before use of the developed freeze-dried products can be simply accomplished with water for injection.

Arsenical-based cancer drugs

Arsenic is a semi-metal or metalloid with two biologically important oxidation states, As(III) and As(V). As(III), in particular, reacts with closely spaced protein thiols, forming stable cyclic dithioarsinite complexes in which both sulfur atoms are bound to arsenic. It is this reaction that is mostly responsible for arsenics cytotoxicity. Arsenic compounds have been used as medicinal agents for many centuries for the treatment of diseases such as psoriasis, syphilis, and rheumatosis. From the 1700's until the introduction of and use of modern chemotherapy and radiation therapy in the mid 1900's, arsenic was a mainstay in the treatment of leukemia. Concerns about the toxicity of arsenical compounds led eventually to their abandonment for the treatment of cancer. The discovery in the 1980's that arsenic trioxide induces complete remission in a high percentage of patients with acute promyelocytic leukemia has awakened interest in this metalloid for the treatment of human disease. In particular, a new class or organoarsenicals are being trialed for the treatment of hematological malignancies and solid tumors. In this review, we discuss the arsenical-based compounds used in the past and present for the treatment of various forms of cancer. Mechanisms of action and selectivity and acute and chronic toxicities are discussed along with the prospects of this class of molecule.

Human African trypanosomiasis: pharmacological re-engagement with a neglected disease

This review discusses the challenges of chemotherapy for human African trypanosomiasis (HAT). The few drugs registered for use against the disease are unsatisfactory for a number of reasons. HAT has two stages. In stage 1 the parasites proliferate in the haemolymphatic system. In stage 2 they invade the central nervous system and brain provoking progressive neurological dysfunction leading to symptoms that include the disrupted sleep wake patterns that give HAT its more common name of sleeping sickness. Targeting drugs to the central nervous system offers many challenges. However, it is the cost of drug development for diseases like HAT, that afflict exclusively people of the world's poorest populations, that has been the principal barrier to new drug development and has led to them becoming neglected. Here we review drugs currently registered for HAT, and also discuss the few compounds progressing through clinical trials. Finally we report on new initiatives that might allow progress to be made in developing new and satisfactory drugs for this terrible disease.

Organoarséniés dérivés du 2-phényl- [1,3,2]dithiarsolane-4-yl)-méthanol (AsIII) à propriétés antileucémiques : des trypanosomicides aux anticancéreux

For several decades, organometallic and organometalloid compounds have played an important part in anticancer chemotherapies, in particular those derived from platinum. Trivalent arsenic, in the form of arsenic trioxide (As2O3; Trisenox(R)) is currently used in the treatment of refractory leukemias, but at the cost of major adverse effects. Moreover, recent studies showed that the trypanocide melarsoprol, could be more effective than arsenic trioxide on myelogenous leukaemias. We have synthesized a series of derivatives from 2-phenyl-[1,3,2]dithiarsolan-4-yl)-methanol (AsIII). Our work shows that the substitution of the aromatic ring by an iodine atom in the ortho position or by an amino-dimethoxytriazin group in the para position increases very significantly the antileukemic activity and improves the therapeutic index (IT=LD50/IC50) of these melarsoprol-derivatives molecules, as compared to arsenic trioxide. However, one of the most promising compounds seems to be arsthinol, an old drug used in the past as an amebicide. Nanoparticle carriers of melarsoprol were also prepared for the purpose of modifying its tissue distribution reduce its brain toxicity.

ConCept: de Novo Design of Synthetic Receptors for Targeted Ligands

Low-molecular-weight receptors that bind targeted guest molecules have a wide range of potential applications but are difficult to design. This paper describes an evolutionary method for computer-aided design of such receptors that works by linking together chemical components from a user-defined library around a stable conformation of the targeted ligand. The software can operate in three modes: de novo design, in which it builds a wide variety of receptors from small components; macrocycle design, in which it builds homopolymeric macrocycles around the ligand; and elaboration of an existing receptor structure. The top candidates generated by the automatic construction process are further studied with detailed affinity calculations whose validity is supported by prior studies of experimentally characterized host-guest systems. All three modes of operation are illustrated here through the design of novel adenine receptors.

Preparation of Drug Nanoparticles by Co-grinding with Cyclodextrin: Formation Mechanism and Factors Affecting Nanoparticle Formation

The aim of this study was to investigate the factors affecting the formation of pranlukast nanoparticle prepared by co-grinding with beta-cyclodextrin (beta-CD) and to elucidate the mechanism of nanoparticle formation. The effects of grinding time, moisture content and CD content on the nanoparticle formation were evaluated by means of UV quantitative determination and particle size analysis. High-resolution scanning electron microscopy (HRSEM) was employed to observe drug nanoparticles in the ground mixture. Nanoparticle recovery was higher than 95% for 2 : 1 molecular mixtures of beta-CD : pranlukast which had been ground for 10 min with moisture levels between 10 and 15%. While that of the 1 : 2 ground mixture prepared at 8% moisture level was only 57%. Nanoparticle recovery from beta-CD : pranlukast 2 : 1 mixture ground for 1 min was 2.5%, while that of the 10 min ground mixture was as high as 95%. HRSEM demonstrated that primary drug nanoparticles having a particle size around 50 nm were observed in the ground mixture. The grinding time, the moisture content, and the CD content had significant influences on the formation of drug nanoparticles. The CD matrix may form and stabilize primary particles by its interaction with the particle surface through water molecules. Primary nanoparticles existed in the ground mixture as 50 nm drug nanocrystallites.