NMR characterization of the host-guest inclusion complex between beta-cyclodextrin and doxepin

Polyaromatic Hydrocarbon Inclusion Complexes with 2-Hydroxylpropyl-β/γ-Cyclodextrin: Molecular Dynamic Simulation and Spectroscopic Studies

In aqueous and solid media, 2-HP-β/γ-CD inclusion complexes with poly aromatic hydrocarbon (PAH) Phenanthrene (PHN), Anthracene (ANT), Benz(a)pyrene (BaP), and Fluoranthene (FLT) were investigated for the first time. The inclusion complexes were characterized and investigated using fluorescence and 1HNMR spectroscopy. The most prevalent complexes consisting of both guests and hosts were those with a 1:1 guest-to-host ratio. The stability constants for the complexes of PHN with 2-HP-β-CD and 2-HP-γ-CD were 85 ± 12 M-1 and 49 ± 29 M-1, respectively. Moreover, the stability constants were found to be 502 ± 46 M-1 and 289 ± 44 M-1 for the complexes of ANT with both hosts. The stability constants for the complexes of BaP with 2-HP-β-CD and 2-HP-γ-CD were (1.5 ± 0.02) × 103 M-1 and (9.41 ± 0.03) × 103 M-1, respectively. The stability constant for the complexes of FLT with 2-HP-β-CD was (1.06 ± 0.06) × 103 M-1. However, FLT was observed to form a weak complex with 2-HP-γ-CD. Molecular dynamic (MD) simulations were used to investigate the mechanism and mode of inclusion processes, and to monitor the atomic-level stability of these complexes. The analysis of MD trajectories demonstrated that all guests formed stable inclusion complexes with both hosts throughout the duration of the simulation time, confirming the experimental findings. However, the flexible Hydroxypropyl arms prevented the PAHs from being encapsulated within the cavity; however, a stable exclusion complex was observed. The main forces that influenced the complexation included van der Waals interactions, hydrophobic forces, and C-H⋯π interaction, which contribute to the stability of these complexes.

Enhancing the Drug-Like Profile of a Potent Peptide PACE4 Inhibitor by the Formation of a Host-Guest Inclusion Complex with β-Cyclodextrin

The enzyme PACE4 has been validated as a promising therapeutic target to expand the range of prostate cancer (PCa) treatments. In recent years, we have developed a potent peptidomimetic inhibitor, namely, compound C23 (Ac-(DLeu)LLLRVK-4-amidinobenzylamide). Like many peptides, C23 suffers from an unfavorable drug-like profile which, despite our efforts, has not yet benefited from the usual SAR studies. Hence, we turned our attention toward a novel formulation strategy, i.e., the use of cyclodextrins (CDs). CDs can benefit compounds through the formation of "host-guest" complexes, shielding the guest from degradation and enhancing biological survival. In this study, a series of βCD-C23 complexes have been generated and their properties evaluated, including potency toward the enzyme in vitro, a cell-based proliferation assay, and stability in plasma. As a result, a new βCD-formulated lead compound has been identified, which, in addition to being more soluble and more potent, also showed an improved stability profile.

Investigation of the Interaction of Benzo(a)Pyrene and Fluoranthene with Cucurbit[n]urils (n = 6-8): Experimental and Molecular Dynamic Study

The inclusion complexes of cucurbit[n]uril, CB[n] (n = 6-8), with poly aromatic hydrocarbon (PAH) Benzo(a)Pyrene (BaP), and fluoranthene (FLT) were investigated carefully in aqueous media. Fluorescence and ¹H NMR spectroscopy were used to characterize and investigate the inclusion complexes that were prepared in the aqueous media. The most predominant complexes of both guests with hosts were the 1:1 guest: host complexes. Stability constants of 2322 ± 547 M^-1, 7281 ± 689 M^-1, 3566 ± 473 M^-1 were obtained for the complexes of BaP with CB[6], CB[7], and CB[8], respectively. On the other hand, stability constants of 5900.270 ± 326 M^-1, 726.87 ± 78 M^-1, 3327.059 ± 153 M^-1 were obtained for the complexes of FLT with CB[6], CB[7], and CB[8], respectively. Molecular dynamic (MD) simulations were used to study the mode and mechanism of the inclusion process and to monitor the stability of these complexes in aqueous media at an atomistic level. Analysis of MD trajectories has shown that both BaP and FLT form stable inclusion complexes with CB[7] and CB[8] in aqueous media throughout the simulation time, subsequently corroborating the experimental results. Nevertheless, the small size of CB[6] prohibited the encapsulation of the two PAHs inside the cavity, but stable exclusion complex was observed between them. The main driving forces for the stability of these complexes are the hydrophobic forces, van der Waals interactions, electrostatic effect, the π····π and C-H···π interaction. These results suggest that BaP and FLT can form stable complexes with CB[n] (n = 6-8) in solution.

Antifungal Combination Eye Drops for Fungal Keratitis Treatment

Fungal keratitis (FK) is a corneal mycotic infection that can lead to vision loss. Furthermore, the severity of FK is aggravated by the emergence of resistant fungal species. There is currently only one FDA-approved formulation for FK treatment forcing hospital pharmacy departments to reformulate intravenous drug preparations with unknown ocular bioavailability and toxicity. In the present study, natamycin/voriconazole formulations were developed and characterized to improve natamycin solubility, permanence, and safety. The solubility of natamycin was studied in the presence of two cyclodextrins: HPβCD and HPγCD. The HPβCD was chosen based on the solubility results. Natamycin/cyclodextrin (HPβCD) inclusion complexes characterization and a competition study between natamycin and voriconazole were conducted by NMR (Nuclear Magnetic Resonance). Based on these results, several eye drops with different polymer compositions were developed and subsequently characterized. Permeability studies suggested that the formulations improved the passage of natamycin through the cornea compared to the commercial formulation Natacyn^®. The ocular safety of the formulations was determined by BCOP and HET-CAM. The antifungal activity assay demonstrated the ability of our formulations to inhibit the in vitro growth of different fungal species. All these results concluded that the formulations developed in the present study could significantly improve the treatment of FK.

Simple Host-Guest Assembly for High-Resolution Magnetic Resonance Imaging of Microvasculature

Magnetic resonance angiography (MRA) is an important imaging technique that can be used to identify and characterize various types of vascular diseases. However, currently used molecular contrast agents are unsuitable for MRA due to the short intravascular retention time, the whole-body distribution, and the relatively low contrast effect. In this study, we developed a vascular analysis contrast agent (i.e., VasCA) for MRA, which is a simple and biocompatible 1:1 host-guest assembly of PEGylated β-cyclodextrin and gadolinium chelate with renal clearable size and high relaxivity (r1 = 9.27 mM-1 s-1). Its biocompatibility was confirmed by in vivo animal studies as well as in vitro 3D cell culture. In a tumor-bearing rat model, VasCA circulated in the blood vessels much longer (4.3-fold increase) than gadoterate meglumine (Dotarem) and was mainly excreted by the renal system after intravenous injection. This feature of VasCA allows characterization of tumor microvasculature (e.g., feeding and draining vessels) as well as visualization of small vessels in the brain and body organs. Furthermore, after treatment with an angiogenesis inhibitor (i.e., sorafenib), VasCA revealed the vessel normalization process and allowed the assessment of viable and necrotic tumor regions. Our study provides a useful tool for diverse MRA applications, including tumor characterization, early-stage evaluation of drug efficacy, and treatment planning, as well as diagnosis of cardiovascular diseases.

Inclusion complexes of tricyclic drugs and β-cyclodextrin: Inherent chirality and dynamic behaviour

Amitriptyline (AMT) and cyclobenzaprine (CBZ) are tricyclic drugs used as antidepressant and muscle relaxant, respectively. They show inherently chirality, i.e. they are chiral due to the lack of any symmetry element. As they are used as racemic mixture, diastereomeric inclusion complexes are formed via encapsulation in homochiral βCD. In this work we show that a suitable combination of NMR methods easily provides details on the chiral recognition, geometry of complexation, rotational dynamics and spatial proximity of selected atom pairs. In particular, we show that ¹³C NMR can be used to unambiguously assess chiral recognition, demonstrating a higher performance over ¹H NMR. The mole fraction of the bound drug and the association constant can be worked out through diffusion experiments, whereas the combination of non-selective, selective and bi-selective relaxation spectra gave insights into the rotational motion of the complexed drug and the spatial proximity of selected proton pairs. The toolkit here proposed provides a thorough characterization of CD/drug inclusion complexes from a physicochemical point of view. This can constructively complement the conventional pharmacological and pharmacokinetic experiments, and can shed light on the understanding of CD/drug formulations.

Supramolecular Complexes of β-Cyclodextrin with Clomipramine and Doxepin: Effect of the Ring Substituent and Component of Drugs on Their Inclusion Topologies and Structural Flexibilities

Depression is a global threat. Tricyclic antidepressants (TCAs) are still efficacious in treating depression, albeit with more side effects. Cyclodextrins (CDs) with a suitable nanocavity are potential drug carriers and can enhance the drug bioavailability. Aiming for an atomistic understanding of the CD encapsulation facilitating the improvement of drug stability and the reduction of side effects, a comprehensive study series of the β-CD-TCA inclusion complexes through single crystal X-ray diffraction and density functional theory (DFT) calculation was undertaken. This work reports the supramolecular complexes of β-CD with two pivotal TCAs, clomipramine (CPM; 1) and doxepin (DXP; 2). The different inclusion topologies of the β-CD-TCA complexes were notable. X-ray analysis revealed that, in 1, the CPM B-ring (without chloro group) was entrapped in the β-CD cavity, whereas, in 2, the E-DXP A-ring and the Z-DXP B-ring were disordered in the cavity, yielding energetically favorable complexes primarily maintained by intermolecular C-H⋯π interactions, as indicated by DFT calculation. Because both wings of TCAs were similar, an alternative inclusion scenario of the A-ring was evidenced crystallographically in four other TCA complexes. The enhanced TCA thermodynamic stabilities via CD inclusion complexation helped to reduce the side effects and to increase the bioavailability. Moreover, the scrutinization of six TCAs in different lattice circumstances revealed the greater TCA structural flexibilities for their optimum pharmacological activity while binding with proteins.

Stepwise Aggregation of Cholate and Deoxycholate Dictates the Formation and Loss of Surface-Available Chirally Selective Binding Sites

Bile salts are facially amphiphilic, naturally occurring chemicals that aggregate to perform numerous biochemical processes. Because of their unique intermolecular properties, bile salts have also been employed as functional materials in medicine and separation science (e.g., drug delivery, chiral solubilization, purification of single-walled carbon nanotubes). Bile micelle formation is structurally complex, and it remains a topic of considerable study. Here, the exposed functionalities on the surface of cholate and deoxycholate micelles are shown to vary from one another and with the micelle aggregation state. Collectively, data from NMR and capillary electrophoresis reveal preliminary, primary, and secondary stepwise aggregation of the salts of cholic (CA) and deoxycholic (DC) acid in basic conditions (pH 12, 298 K), and address how the surface availability of chirally selective binding sites is dependent on these sequential stages of aggregation. Prior work has demonstrated sequential CA aggregation (pH 12, 298 K) including a preliminary CMC at ca. 7 mM (no chiral selection), followed by a primary CMC at ca. 14 mM that allows chiral selection of binaphthyl enantiomers. In this work, DC is also shown to form stepwise preliminary and primary aggregates (ca. 3 mM DC and 9 mM DC, respectively, pH 12, 298 K) but the preliminary 3 mM DC aggregate is capable of chirally selective solubilization of the binaphthyl enantiomers. Higher-order, secondary bile aggregates of each of CA and DC show significantly degraded chiral selectivity. Diffusion NMR reveals that secondary micelles of CA exclude the BNDHP guests, while secondary micelles of DC accommodate guests, but with a loss of chiral selectivity. These data lead to the hypothesis that secondary aggregates of DC have an exposed binding site, possibly the 7α-edge of a bile dimeric unit, while secondary CA micelles do not present binding edges to the solution, potentially instead exposing the three alcohol groups on the hydrophilic α-face to the solution.

Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

Since several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving 4-thiothymidine (S(4)TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic techniques (UV-vis, FTIR-ATR, (1)H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective research on the photoreactivity of S(4)TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation. UV-vis, FTIR-ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S(4)TdR. (1)H NMR analyses confirmed such indication, unveiling the presence of inclusion complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S(4)TdR affinity towards CDs was also evaluated by using the Benesi-Hildebrand (B-H) equation at 25 °C employing CV and (1)H NMR methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs.

Chiral separation of asenapine enantiomers by capillary electrophoresis and characterization of cyclodextrin complexes by NMR spectroscopy, mass spectrometry and molecular modeling

The enantiomers of asenapine maleate (ASN), a novel antipsychotic against schizophrenia and mania with bipolar I disorder have been separated by cyclodextrin (CD) modified capillary zone electrophoresis for the first time. 15 different CDs were screened as complexing agents and chiral selectors, investigating the stability of the inclusion complexes and their enantiodiscriminating capacities. Although initially, none of the applied chiral selectors gave baseline separation, β-CD proved to be the most effective chiral selector. In order to improve resolution, an orthogonal experimental design was employed, altering the concentration of background electrolyte, organic modifier, pH, capillary temperature and applied voltage in a multivariate manner. The developed method (160 mM TRIS-acetate buffer pH 3.5, 7 mM β-CD, at 20 °C, applying 15 kV) was successful for baseline separation of ASN enantiomers (R(s)=2.40±0.04). Our method was validated according to ICH guidelines and proved to be sensitive, linear, accurate and precise for the chiral separation of ASN. Properties of the inclusion complexes, such as stoichiometry, atomic level intermolecular host-guest connections are proposed on the basis of ROESY NMR measurement, ESI-MS spectrometry and molecular modeling studies. It was found that the ASN-β-CD complex is of 1:1 composition, and either of the aromatic rings can be accommodated in the β-CD cavity.

Interaction of polyphenol oxidase of Solanum tuberosum with β-cyclodextrin: Process details and applications

Polysaccharides differing in structure and chemical nature were screened for their ability to bind non-covalently with polyphenol oxidase (PPO) from potato (as a model) and their effect on enzyme activity. All the polysaccharides selected inhibited the PPO but β-cyclodextrin showed maximum inhibition under optimum conditions. Process details for the inhibition of PPO were studied with respect to concentration of β-cyclodextrin, temperature, pH, and time. Higher inhibition constant and lower half life was obtained at 40 °C than at 30 °C in the presence of inhibitor. β-Cyclodextrin showed mixed type of inhibition of PPO. β-Cyclodextrin was further exploited as anti-browning agent in selected fruit juices. It not only showed a significant anti-browning effect on freshly prepared potato juice but was also effective in other fruit juices. Better effect was seen in pineapple, apple and pear as compared to banana, sugarcane and guava fruit juices.

Interaction of fentanyl with various cyclodextrins in aqueous solutions

OBJECTIVES

Water-soluble fentanyl citrate salt has been used in sublingual or buccal formulations for the breakthrough pain treatment. However, fentanyl absorption through the lipid mucosal membrane may be improved by enhancing the non-ionic lipophilic fentanyl base solubility. Therefore, the interaction between cyclodextrins (CDs) and fentanyl base has been evaluated to obtain basic information for its application.

METHODS

Parent CDs (α-, β- and γ-CD) as well as α- and β-CD derivatives were used for solubility studies with fentanyl base. Nuclear magnetic resonance (NMR) studies were applied in a system including β-CD or glucosyl-β-CD (G1-β-CD) with fentanyl base or fentanyl citrate. (1) H- and (13) C-NMR studies and a two-dimensional rotating frame Overhauser effect spectroscopy (ROESY) study were conducted to confirm inclusion complexes formation.

KEY FINDINGS

Parent CDs displayed BS type phase solubility diagrams; β-CD exhibited a strong interaction with fentanyl base. Hydrophilic β-CD derivatives, such as G1-β-CD, displayed AL type phase diagrams and higher solubilizing effects compared with parent CDs. ROESY study suggested that fentanyl phenyl groups were included in β-CD cavity.

CONCLUSIONS

This study revealed that hydrophilic β-CD derivatives, such as G1-β-CD, could be useful pharmaceutical additives for oral mucosal formulations because of the improved fentanyl base solubility via inclusion complexation.

Precision studies in supramolecular chemistry: a 1H NMR study of hydroxymethoxyacetophenone/β-cyclodextrin complexes

The association constants for the interactions of 2-hydroxy-4-methoxyacetophenone, 2-hydroxy-5-methoxyacetophenone, 2-hydroxy-6-methoxyacetophenone, 3-hydroxy-4-methoxyacetophenone and 4-hydroxy-3-methoxyacetophenone with β-cyclodextrin in water were measured by (1)H NMR and by isothermal titration calorimetry. Very good agreement was obtained between the different methods. The errors associated with the NMR method for measuring mM binding affinities were estimated to be 10-30%, and by isothermal titration calorimetry, 10-20%. Rotating frame nuclear Overhauser effect spectroscopy studies show that the solution phase host-guest complexes formed by β-cyclodextrin with these hydroxymethoxyacetophenone derivatives are not structurally well defined but that the hydroxymethoxyacetophenone derivatives are mostly associated with the narrow primary hydroxyl rim.

New formulation of an old drug in hypertension treatment: the sustained release of captopril from cyclodextrin nanoparticles

Captopril (CAP) was the first angiotensin I-converting enzyme (ACE) inhibitor to be developed and is widely used in hypertension treatment. On the other hand, cyclodextrins (CDs) are cyclic oligosaccharides whose cone-shaped cavity allows formation of noncovalent inclusion complexes with appropriately sized guest molecules, thus modifying guest physical, chemical, and biological properties. Herein, the physicochemical characterization and in vivo ACE inhibition evaluation of seven CAP/CD complexes are reported. The inclusion complexes were prepared by spray-drying, freeze-drying, kneading, or lyophilization methods and characterized by nuclear magnetic resonance, Fourier-transformed infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy techniques. In vivo assays compared CAP and CAP/CD complex administration (0.5 mg kg⁻¹ or 0.09 mg kg⁻¹, n = 4–7) to evaluate the ACE inhibition by continuous infusion of angiotensin I (30 ng 50 μL⁻¹ min⁻¹) in conscious Wistar rats. The physicochemical analysis demonstrated complete amorphization and complexation between CAP and CDs, indicating the substitution of water molecules inside the CD cavity with CAP. During the infusion of angiotensin I, the administration of all CAP/CD complexes induced a reduction in mean arterial pressure similar to that observed upon CAP administration. The nanoparticles obtained by the kneading method (CAP/α-CD:KM) showed a potent and long-lasting inhibitory activity (∼22 hours) on the angiotensin I pressor effect. The results suggest that the inclusion complex of CAP and α-CD can function as a novel antihypertensive formulation that may improve therapeutic use of CAP by reducing its oral dose administration to once per day, thus providing better quality of life for almost 25% of the world’s population who suffer from hypertension.

Molecular recognition and enhancement of aqueous solubility and bioactivity of CD437 by β-cyclodextrin

CD437 (6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid) is a novel synthetic retinoic acid derivative that has been shown to selectively induce apoptosis in human lung cancer cells. This compound, however, is limited in its application due to its low solubility in aqueous solutions. One technique for increasing the solubility and bioavailability of a cytotoxic agent is the formation of inclusion complexes with cyclodextrins. Herein, we report the formation and characterization of a 2:1 complex between β-cyclodextrin (β-CD) and CD437. It is shown that CD437 is a tight binder of β-CD with an overall association constant of 2.6±0.6×10(7)M(-2). In addition, we demonstrate (a) that β-CD-derived complexation enhances the aqueous solubility of CD437, and (b) that a significant increase in the toxicity of CD437 against a human lung adenocarcinoma cell line can be achieved by co-treatment with β-CD.

Preparation and characterization of inclusion complexes of a hemisuccinate ester prodrug of delta9-tetrahydrocannabinol with modified beta-cyclodextrins

Delta(9)-Tetrahydrocannabinol hemisuccinate (THC-HS), an ester prodrug of Delta(9)-tetrahydrocannabinol (THC) has been investigated for its potential to form inclusion complexes with modified synthetic beta-cyclodextrins (CDs). Phase solubility studies were performed to determine the stoichiometric ratio of complexation of THC-HS with random methylated beta-cyclodextrin (RAMEB) and 2-hydroxypropyl beta-cyclodextrin (HPBCD). THC-HS/RAMEB and THC-HS/HPBCD solid systems were prepared by lyophilization and the lyophilized complexes were characterized by Fourier transform infrared (FT-IR) spectroscopy, proton nuclear magnetic spectroscopy, and molecular modeling techniques. The formation of inclusion complexes of THC-HS/RAMEB and THC-HS/HPBCD was demonstrated by an A(L) type curve with the slopes less than unity by the phase solubility method. The association constants for THC-HS/RAMEB and THC-HS/HPBCD were found to be 562.48 and 238.83 M(-1), respectively. The stoichiometry of both of the complexes was found to be 1:1 as determined from the Job's plot. This was confirmed by (1)H NMR and FT-IR techniques. The results obtained from the molecular modeling studies were in accordance with the data obtained from nuclear magnetic resonance and FT-IR. The docking studies revealed the most probable mode of binding of THC-HS with RAMEB in which the alkyl chain was submerged in the hydrophobic pocket of the CD molecule and hydrogen bonding interactions were observed between the hemisuccinate ester side chain of THC-HS and the rim hydroxy groups of RAMEB. The solubility of THC-HS was significantly higher in RAMEB compared to HPBCD. Solid dispersions of THC-HS with CDs will be further utilized to develop oral formulations of THC-HS with enhanced bioavailability.

Characterization of binding affinities in a chromatographic system by suspended state HR/MAS NMR spectroscopy

In the current work a racemate of (R)- and (S)-benzylmandelate was separated with a stereoselective polysaccharide-based chiral stationary phase by HPLC. To elucidate the occurring chiral molecular recognition processes in the heterogeneous system used, NMR spectroscopy was chosen under high resolution/magic angle spinning (HR/MAS) NMR conditions in the suspended state. Therefore, and as a proof of concept, a combination of several NMR methods such as spin-lattice relaxation time (T(1)) measurements (T(1)), the saturation transfer difference, and the 2D experiment of the transferred nuclear overhauser enhancement spectroscopy technique were applied. With HR/MAS NMR it is feasible to combine NMR and chromatography to achieve further insights into the separation process.

Transcutaneous electroporation mediated delivery of doxepin-HPCD complex: a sustained release approach for treatment of postherpetic neuralgia

The electroporation mediated transdermal delivery (Protocol - 120 V, 10 ms, 30 pulses at 1 Hz with post pulse waiting period of 20 min) of doxepin using pure drug solution (PDS) and doxepin-hydroxypropyl-beta-cyclodextrin (HPCD) complex solution (CDS) was studied using porcine epidermis model. The stoichiometry of drug-HPCD inclusion complex was determined by differential scanning calorimetry (DSC). The amount of doxepin retained in the epidermis following electroporation did not differ significantly between PDS and CDS. When the drug loaded epidermis was subjected to "Release studies", doxepin release attained a plateau within approximately 2.5 days in case of PDS, whereas in case of CDS, doxepin release was prolonged up to 5 days. Mechanistic studies across the nonbiological barriers demonstrated that the slow dissociation of complex was responsible for sustained release of drug from the epidermis. Pharmacodynamic studies were carried out by electroporation mediated delivery of CDS and PDS in hairless rats. The analgesic effect of doxepin was prolonged in case of CDS as compared to PDS.

Protein-free ligand screening: simplification of chiral chromatographic development via novel adaptation of NMR screening methodologies

We demonstrate here a promising NMR method that provides evidence for chiral compound selector interaction as a first-pass screening method. A novel adaptation of commonly used protein-based screening technologies, this approach relies upon ligand-to-stationary phase interaction wherein the stationary phase is tethered to sepharose beads. At only minutes per experiment, this methodology significantly reduces the time required for chiral separation methodology development and complements currently available chromatographic purity technologies.

Sodium cholate aggregation and chiral recognition of the probe molecule (R,S)-1,1'-binaphthyl-2,2'-diylhydrogenphosphate (BNDHP) observed by 1H and 31P NMR spectroscopy

Bile salt micelles can be employed as a pseudostationary phase in micellar electrokinetic capillary chromatography (MEKC) separations of chiral analytes. To improve MEKC separations of chiral analytes, a molecular level understanding of micelle aggregation in the presence of analyte is needed. Here, aggregation of sodium cholate has been observed by exploiting the presence of a model analyte molecule. The 31P and 1H nuclear magnetic resonance spectroscopy (NMR) chemical shifts of (R,S)-1,1'-binaphthyl-2,2'-diylhydrogenphosphate ((R,S)-BNDHP), a model analyte in chiral MEKC separations, are demonstrated to be very sensitive to the aggregation state of the bile salt sodium cholate. In addition to probing micellar aggregation, the NMR spectral resolution of enantiomeric species is also stronglycorrelated with chiral separations in MEKC. In this work, the aggregation of sodium cholate in basic solutions (pH 12) has been observed over the concentration range 0-100 mM. The primary critical micelle concentration (cmc) was found to be 14 +/- 1 mM for basic solutions of sodium cholate. In addition, a primitive aggregate is clearly observed to form at 7 +/- 1 mM sodium cholate. The data also show pseudo-cmc behavior for secondary aggregation observed in the regime of 50-60 mM cholate. Finally, the H5-H7 edge of BNDHP is shown to be sensitive to chirally selective interactions with primary cholate micelles.