Potential of biopartitioning micellar chromatography as an in vitro technique for predicting drug penetration across the blood-brain barrier

The blood-brain barrier (BBB) is considered to be the main barrier to drug transport into the central nervous system (CNS). The BBB restricts the passive diffusion of many drugs from blood to brain. The ease with which any particular drug diffuses across the BBB is determined largely by the molecular features of drugs, and it is therefore possible to predict the BBB permeability of a drug from its molecular structure. Biopartitioning micellar chromatography (BMC), a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 in adequate experimental conditions, can be useful in mimicking the drug partitioning process into biological systems. Retention in BMC depends on the hydrophobicity, electronic and steric properties of drugs. In this paper, the usefulness of BMC for predicting the BBB penetration ability of drugs expressed as the brain/blood distribution coefficient (BB) is demonstrated. A multiple linear regression (MLR) model that relates the BB distribution coefficients data with BMC retention data and total molar charge is proposed. The model is obtained using 44 heterogeneous drugs including, neutral, anionic, and cationic compounds. A comparison with other reported methodologies to predict the BBB permeability is also presented.     

Biopartitioning micellar chromatography: an in vitro technique for predicting human drug absorption

The main oral drug absorption barriers are fluid cell membranes and generally drugs are absorbed by a passive diffusion mechanism. Biopartitioning micellar chromatography (BMC) is a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 under adequate experimental conditions and can be useful to mimic the drug partitioning process in biological systems. In this paper the usefulness of BMC for predicting oral drug absorption in humans is demonstrated. A hyperbolic model has been obtained using the retention data of a heterogeneous set of 74 compounds, which shows predictive ability for drugs absorbed by passive diffusion. The model obtained in BMC is compared with those obtained using the well-known systems (Caco-2 and TC-7) that use intestinal epithelium cell lines. The use of BMC is simple, reproducible and can provide key information about the transport properties of new compounds during the drug discovery process.     

Retention–property relationships of anticonvulsant drugs by biopartitioning micellar chromatography

Epilepsy may be considered as a group of disorders with only one thing in common: the fact that recurrent anomalous electrochemical phenomena appear in the central nervous system. Different classes of drugs are included under the generic term of anticonvulsant drugs. All of them work by decreasing discharge propagation in different ways. Biopartitioning micellar chromatography (BMC) is a mode of reversed-phase liquid chromatography, which can be used as an in vitro system to model the biopartitioning process of drugs when there are no active processes. In this paper, relationships between the BMC retention data of anticonvulsant drugs, their pharmacokinetics (oral absorption, protein binding, volume of distribution, clearance, and renal elimination) and their therapeutic parameters (therapeutic, toxic and comatose-fatal concentration, and LD₅₀) are studied and the predictive ability of models is evaluated.     

Retention pharmacokinetic and pharmacodynamic parameter relationships of antihistamine drugs using biopartitioning micellar chromatography

Antihistamines are drugs which act by competitive inhibition of the H₁ or H₂ histamine receptors. Little has been known about their clinical pharmacokinetics and biological responses until the last few years. In this paper, we propose quantitative retention–activity relationship, QRAR, models based on the retention data of antihistamines in a biopartitioning micellar chromatography (BMC) system using a Brij35 mobile phase for describing pharmacokinetic parameters such as half-life and volume of distribution, or the pharmacodynamic parameters, therapeutic plasma levels, lethal doses and drug-receptor dissociation constant. The predictive ability of these models is statistically validated. These results are compared to traditional quantitative structure–activity relationship, QSAR, models using lipophilicity data. The adequacy of QRAR models can be explained taking into account the fact that the retention of compounds in BMC depends on their hydrophobic, electronic and steric characteristics which are of great importance in pharmacokinetic and pharmacodynamic behavior.     

Opioid analgetics retention-pharmacologic activity models using biopartitioning micellar chromatography

Opioids are drugs used in medicine for pain control. In this paper, retention-pharmacokinetics and retention-pharmacodynamics relationships of opioids are proposed and statistically validated. These models are based on the compound retention in the biopartitioning micellar chromatography system (BMC), a new methodology which has successfully been used to develop QRAR models for many other families of compounds. The obtained results are compared to the traditional QSAR models using lipophilicity data. The adequacy of QRAR models is due to the fact that the characteristics of the compounds such as the hydrophobicity, electronic charge and steric effects determine both their retention in BMC and their pharmacokinetic and pharmacodynamic behavior.     

Role of hydrophobicity on the monoamine receptor binding affinities of central nervous system drugs: a quantitative retention-activity relationships analysis using biopartitioning micellar chromatography

Biological action and activity reflect an aspect of the fundamental physicochemical properties of the bioactive compounds. As an alternative to classical QSAR studies, in this work different quantitative retention-activity relationships (QRAR) models are proposed, which are able to describe the role of hydrophobicity on the binding affinity to different brain monoamine receptors (H(1)-histamine, alpha(1)-noradrenergic and 5-HT(2)-serotonergic) of different families of psychotherapeutic drugs. The retention of compounds is measured in a biopartitioning micellar chromatography (BMC) system using Brij-35 mobile phases. The adequacy of the QRAR models developed is due to the fact that both the retention of compounds in BMC and the drug-receptor interaction are described by the same hydrophobic, electronic and steric properties of compounds. The obtained results indicate that, for structurally related compounds that present the same molecular features as the basic pharmacophore, there is a retention range in which compounds present the highest affinity to all of monoamine receptors.     

High-performance liquid chromatographic determination of diuretics in urine by micellar liquid chromatography

The use of micellar liquid chromatography for the determination of diuretics in urine by direct injection of the sample into the chromatographic system is discussed. The retention of the urine matrix at the beginning of the chromatograms was observed for different sodium dodecyl sulphate (SDS) mobile phases. The eluent strengths of a hybrid SDS—methanol micellar mobile phase for several diuretics were compared and related to the stationary phase/water partition coefficient with a purely micellar mobile phase. The urine band was appreciably narrower with a mobile phase of 0.05 M SDS—5% methanol (v/v) at 50°C (pH 6.9). With this mobile phase the determination of bendroflumethiazide and chlorthalidone was adequate. Acetazolamide, ethacrynic acid, furosemide, hydrochlorothiazide and probenecid were overlapped by the urine matrix, and the retention of amiloride and triamterene was too long.     

Magnesia-zirconia based mimetic biomembrane chromatography for predicting human drug absorption

In this paper, a novel mimetic biomembrane chromatography stationary phase of magnesia-zirconia composite matrix were prepared with the Lewis acid-base interaction between phosphatidylcholine's residue phosphonate group and Lewis acid sites of magnesia-zirconia composite; the retention factors of a chemically diverse set of drugs on the new stationary phase were determined; the drugs logK(mbm) values were correlationed with the absorbed fraction of drugs orally administered in humans (%F(a)) and a hyperbolic relationship was obtained. Meanwhile, the relationship between the logK(mbm) values and hydrophobic parameters (logP(oct) and logD(oct)) were discussed. The usefulness of the new column for predicting oral drug absorption in humans is demonstrated by comparing this model with IAM, ILC and BMC models. Results show that the logK(mbm) values have good relationship with logK(W)(IAM), logK(BMC) and have moderate to fair relationship with logK(s) determined on four different ILC column (EPL, PC, PC-PE, PC-PS). Therefore, the logK(mbm) values can provide key information about the transport properties of drugs and this chromatographic model may be applicable for prediction of drug uptake through epithelial cell membranes during the drug discovery process.     

Good oral absorption prediction on non-nucleoside benzothiadiazine dioxide human cytomegalovirus inhibitors using combined chromatographic and neuronal network techniques

The current drugs available against human cytomegalovirus (HCMV) suffer from a number of shortcomings such as toxic side effect, poor bioavailability and/or risk for emergence of drug-resistance virus strains. Due to these limitations, the development of new drugs against HCMV is of great interest. Taking into account the therapeutic potential of benzothiadiazines dioxides (BTD) derivatives, it is most important to know their oral bioavailability because all the current clinical drugs are poorly absorbed. In this work, the utility of CODES neural networks and biopartitioning micellar chromatography (BMC) in predicting pharmacokinetic properties has been used to estimate the oral absorption of BTD derivatives and their efficacy has been verified. The results indicate higher values for BTD derivatives than the currently licensed anti-viral agents.     

Characteristics of protein partitioning in an aqueous micellar-gel system

Partitioning of proteins has been studied experimentally in a system combining a gel-bead phase and a nonionic micellar phase. The micellar phase consists of cylindrically shaped micelles, which are completely excluded from the gel-bead phase. Partitioning of single-component protein solutions (myoglobin, ovalbumin, and BSA) is determined by excluded-volume interactions in the micellar phase, and as a result the proteins prefer the gel-bead phase to the micellar phase. The protein concentration inside the gel beads increases with an increase in volume fraction of the micelles and increases with an increase in the size of the proteins. The protein partition coefficients obtained for a binary mixture of myoglobin and bovine serum albumin (BSA) show the same protein concentration dependence as the single-component protein partition coefficients.     

Chromatographic evaluation of the toxicity in fish of pesticides

Ecotoxicity assessment is essential before placing new chemical substances on the market. An investigation of the use of the chromatographic retention (log k) in biopartitioning micellar chromatography (BMC) as an in vitro approach to evaluate the toxicity in fish of pesticides (acute toxicity levels as pLC(50)) is proposed. A heterogeneous data set of 85 pesticides from six chemical families with available experimental fish toxicity data (ECOTOX database from U.S. Environmental Protection Agency (EPA)) was used. For pesticides exhibiting non-polar narcosis mechanism in fish (non-specific toxicity), more reliable models and precise pLC(50) estimations are obtained from log k (quantitative retention-activity relationships, QRAR) than from log P (quantitative structure-activity relationships, QSAR) or ECOSAR (ECOSAR program from U.S. EPA).     

Improvement in extraction and catalytic activity of Mucor javanicus lipase by modification of AOT reverse micelle

Reverse micelles are formed in apolar solvents by spontaneous aggregation of surfactants. Surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) is most often used for the reverse micellar extraction of enzymes. However, the inactivation of enzyme due to strong interaction with AOT molecules is a severe problem. To overcome this problem, the AOT/water/isooctane reverse micellar system was modified by adding short chain polyethylene glycol 400 (PEG 400). The modified AOT reverse micellar system was used to extract Mucor javanicus lipase from the aqueous phase to the reverse micellar phase. The extraction efficiency (E) increased with the increase in PEG 400 addition and the maximum E in PEG 400 modified system was twofold higher than that in the PEG 400-free system. Upon addition of PEG 400, the water activity (a(w)) of aqueous phase decreased, whereas a(w) of reverse micellar phase increased. The circular dichroism spectroscopy analysis revealed that PEG 400 changes the secondary and tertiary structure of lipase. The maximum specific activity of lipase extracted in PEG 400-modified reverse micellar system was threefold higher than that in the PEG-free system.     

Chromatographic behaviour in reversed-phase high-performance liquid chromatography with micellar and submicellar mobile phases: effects of the organic modifier

Continuing our earlier study of the retention behaviour in reversed-phase systems with aqueous mobile phases containing surfactants in concentrations lower (submicellar systems) and higher (micellar systems) than the critical micellar concentration (CMC), we investigated the chromatographic behaviour of various non-ionic solutes in mixed aqueous-organic micellar and submicellar mobile phases and their dependence on the methanol concentration. CMC values were measured for two cationic surfactant and one anionic surfactant in mixed aqueous-methanolic solvents, and were found to increase slightly with increasing methanol concentration. Depending on the character of the surfactant, a limiting concentration of methanol was found, above which micelles do not occur anymore. Sorption isotherms of the surfactants on an octylsilica gel column were measured as a function of the concentration of methanol in aqueous-methanolic solvents. A modified Langmuir equation was used to describe the distribution of the surfactants between the stationary and the mobile phases in the concentration range below CMC. The retention of several polar solutes was measured on an octylsilica gel column both in micellar and submicellar mobile phases containing methanol. The dependencies of the capacity factors of the solutes studied on the concentration of methanol in the mobile phase can be suitably described by the same form of equation as that conventionally used for aqueous-organic mobile phases that do not contain surfactants, but the slopes of the dependencies for a given solute are different in the two ranges of surfactant concentrations. The ratio of the two slopes is controlled by the interaction with micelles and is approximately equal to, below or above 1, depending on whether the solutes do or do not associate with the micelles, or are repulsed from them. Simultaneous control of the concentrations of the organic solvent and of the surfactant in the mobile phase can be used for fine tuning the selectivity of separation as a complement to commonly used adjusting concentrations of two organic solvents in ternary aqueous-organic mobile phases. These effects are illustrated by practical examples of submicellar HPLC with mobile phases containing methanol.     

Delivery of Thermoresponsive-Tailored Mixed Micellar Nanogel of Lidocaine and Prilocaine with Improved Dermatokinetic Profile and Therapeutic Efficacy in Topical Anaesthesia

The topical delivery of local anaesthetics has always been a difficult task due to the limited percutaneous absorption of local anaesthetic drugs across the various barriers of the skin. In this pursuit, a thermoresponsive mixed micellar nanogel (MMNG) system of lidocaine and prilocaine has been attempted in the current piece of work. The system relies on the ability to alter its phase state (sol-to-gel) for feasibility of the topical application in response to change in temperature. The composition of MMNG entails majorly of Pluronic® F127 and Tween 80 in a fixed combination so as to provide the desired thermoreversibility for the skin application. The gels were optimized with respect to phase transition temperature (T _sol/gel), turbidity and viscosity. The optimized systems were then characterized for particle size, spreadability, syringeability, bioadhesive strength, ex vivo skin permeation, retention and dermatokinetic studies. The skin compatibility revealed that no histological changes were observed for optimized formulation, while the conventional system showed changes in the skin-tissues. Further, the enhanced intensity of anaesthetic effect was noted in an in vivo rabbit model and tail flick model in mice. The overall results suggest that the prepared MMNG system possesses the potential in providing an efficacious, safe and acceptable alternative therapeutic system for topical anaesthesia.     

Characteristics of the action of psychostimulants on learning and memory in rats

The effects of intraperitoneal injections of psychostimulant drugs: centrophenoxine (50 mg/kg) and peptide analog of tuftsin TP-1 (300 micrograms/kg) on the processes of elaboration and retention of conditioned reflex have been experimentally studied. The animals were trained with food reward in 30 trials per day. Psychostimulant drugs or saline were injected after the 10th trial. The elaboration of conditioned reflex was continued 30 min later. The retention was tested 24 h, 7 and 30 days later. It was established that both drugs induce an increase in memory traces stability during 30 days. These findings provide direct evidence that psychostimulant drugs, centrophenoxine and peptide substance TP-1, when injected during consolidation phase can enhance memory storage processes.     

Lipase-catalyzed hydrolysis of olive oil in chemically-modified AOT/isooctane reverse micelles in a hollow fiber membrane reactor

The hydrolysis of olive oil catalyzed by Candida rugosa lipase in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane and the synthetic sodium bis(2-ethylhexyl polyoxyethylene)sulfosuccinate (MAOT)/isooctane reverse micellar systems was investigated in a polysulfone hollow fiber membrane reactor with recycle of the reaction mixture. Lipase was completely retained by the membrane while olive oil and oleic acid freely passed through. The retention of reverse micelles depended on W ₀ (molar ratio of water to surfactant). At an olive oil concentration of 0.23 mol l^–1 the final substrate conversion in the MAOT micellar system was about 1.4 times of that in the AOT micellar system.     

Targeted cell replacement with bone marrow cells for airway epithelial regeneration

It has been suggested that some adult bone marrow cells (BMC) can localize to the lung and develop tissue-specific characteristics including those of pulmonary epithelial cells. Here, we show that the combination of mild airway injury (naphthalene-induced) as a conditioning regimen to direct the site of BMC localization and transtracheal delivery of short-term cultured BMC enhances airway localization and adoption of an epithelial-like phenotype. Confocal analysis of airway and alveolar-localized BMC (fluorescently labeled) with epithelial markers shows expression of the pulmonary epithelial proteins, Clara cell secretory protein, and surfactant protein C. To confirm epithelial gene expression by BMC, we generated transgenic mice expressing green fluorescent protein (GFP) driven by the epithelial-specific cytokeratin-18 promoter and injected BMC from these mice transtracheally into wild-type recipients after naphthalene-induced airway injury. BMC retention in the lung was observed for at least 120 days following cell delivery with increasing GFP transgene expression over time. Some BMC cultured in vitro over time also expressed GFP transgene, suggesting epithelial transdifferentiation of the BMC. The results indicate that targeted delivery of BMC can promote airway regeneration.     

Protein extraction using the sodium bis(2-ethylhexyl) phosphate (NaDEHP) reverse micellar system

The reverse micellar system of sodium bis(2-ethylhexyl) phosphate (NaDEHP)/isooctane/brine was used for liquid-liquid extraction of proteins. We investigated the solubilization of cytochrome-c and alpha-chymotrypsin into the NaDEHP reverse micellar phase by varying the pH and NaCl concentration in the aqueous phase. At neutral pH and relatively low ionic strength, the proteins are extracted into the micellar phase with high yield. By contacting the micellar phase with a divalent cation (e.g., Ca(2+)) aqueous solution, the reverse micelles are destabilized and release the protein molecules back into an aqueous solution for recovery. This method separates the proteins from the surfactant with very high overall efficiencies. (c) 1996 John Wiley & Sons, Inc.     

Bone marrow cell-mediated cardiovascular repair: potential of combined therapies

Recent evidence indicates that bone-marrow cells (BMCs) can contribute to the healing process of the injured cardiovascular system via the chemokine receptor CXCR4/SDF-1, thymosin beta(4) and integrin alpha(4)beta(1) molecular pathways. During tissue ischemia overwhelming numbers of detrimental oxygen radicals are generated, and therefore treatment with antioxidants and L-arginine, the precursor of nitric oxide (NO), could induce beneficial effects beyond those achieved by BMC transplantation alone. Recent studies have reported that BMCs have enhanced neovascularization capacity in cotreatment with alpha-tocopherol (vitamin E), ascorbic acid (vitamin C) and L-arginine. Moreover, BMC therapy can be combined with gene therapy. Clinical trials employing BMCs in the treatment of cardiovascular diseases have been completed with mixed or positive results, and several trials are ongoing. Here, we discuss the clinical potential of BMC transplantation alone and in combined therapy that aims to restore organ vascularization and function. We also consider the mechanisms of mobilization, differentiation and incorporation of BMCs.     

Differences in the release of cholesterol from taurocholate versus taurochenodeoxycholate micellar solutions

The maximal micellar solubility, distribution and apparent monomer activity of cholesterol in taurine-conjugated cholate and chenodeoxycholate micellar solutions were studied to clarify the different modulating effect of these bile salt species on cholesterol uptake in an intestinal lumen. The maximal micellar solubility was significantly greater in taurochenodeoxycholate. The intermicellar cholesterol monomer concentration was not significantly different between the two kinds of micellar solution. However, the apparent cholesterol monomer activity determined using an artificial organic phase (polyethylene disc) was significantly higher in taurocholate than that in taurochenodeoxycholate. A linear relationship between the intermicellar cholesterol concentration and the apparent cholesterol monomer activity was found, with the slope depending upon the bile salt species. It is concluded that the difference in partitioning of cholesterol from taurocholate and taurochenodeoxycholate micelles into a fixed organic phase may contribute in part to the different regulating effects of these bile salts on the uptake of cholesterol in the intraluminal phase.