Phospholipid bilayers as biological membrane models: The effect of N,N′-bis(dichloroacetyl)-1,12-diaminododecane

Summary N,N-bis(dichloroacetyl)-1,12-diaminododecane is a potent inhibitor of microsomal drug metabolism and also uncouples succinate-linked mitochondrial oxidative phosphorylation, apparently by promoting a transient permeability to anions. When added in very small concentrations to synthetic phospholipid bilayers made from a 144 mixture of purified cardiolipin, phosphatidylcholine, and phosphatidylethanolamine, the drug causes a rapid, transient decrease in electrical resistance with a return to an end-resistance somewhat lower than the initial one. The magnitude of the decrease was related to drug concentration. However, the drug produced a nontransitory, i.e. permanent decrease in resistance of bilayers made from pure phosphatidylcholine or cardiolipin. The 144 mixture of lipids, which closely resembles the lipid composition of the inner mitochondrial membrane yielded drug effects most closely resembling those observed in intact mitochondria. Transference number measurements on the 144 bilayer with an impressed KCl gradient revealed that the drug-induced decrease in electrical resistance was caused by an increase in the fraction of current carried by the anions in the system. The 144 phospholipid bilayer thus mimics the mitochondrial inner membrane in its response to this drug and indicates that the lipid composition of the lipid bilayer is a major determinant of at least some of its physical characteristics. The effect of varying the structure of the drug was also examined.     

Combination of anti-hypertensive drugs: a molecular dynamics simulation study

The anti-hypertensive drugs amlodipine, atenolol and lisinopril, in ordinary and PEGylated forms, with different combined-ratios, were studied by molecular dynamics simulations using GROMACS software. Twenty simulation systems were designed to evaluate the interactions of drug mixtures with a dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane, in the presence of water molecules. In the course of simulations, various properties of the systems were investigated, including drug location, diffusion and mass distribution in the membrane; drug orientation; the lipid chain disorder as a result of drug penetration into the DMPC membrane; the number of hydrogen bonds; and drug surface area. According to the results obtained, combined drugs penetrate deeper into the DMPC lipid bilayer membrane, and the lipid chains remain ordered. Also, the combined PEGylated drugs, at a combination ratio of 1:1:1, enhance drug penetration into the DMPC membrane, reduce drug agglomeration, orient the drug in a proper angle for easy penetration into the membrane, and decrease undesirable lipotoxicity due to distorted membrane self-assembly and thickness.

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Nanostructured lipid carriers as semisolid topical delivery formulations for diflucortolone valerate

Context: Topical treatment of skin disease needs to be strategic to ensure high drug concentration in the skin with minimum systemic absorption.

Objective: The aim of this study was to produce semisolid nanostructured lipid carrier (NLC) formulations, for topical delivery of the corticosteroid drug, diflucortolone valerate (DFV), with minimum systemic absorption.

Method: NLC formulations were developed using a high shear homogenization combined with sonication, using Precirol® ATO5 or Tristearin® as the solid lipid, Capryol? or isopropyl myristate as the liquid lipid and Poloxamer® 407 as surfactant. The present study addresses the influence of different formulations composition as solid lipid, liquid lipid types and concentrations on the physicochemical properties and drug release profile from NLCs.

Results and discussion: DFV-loaded NLC formulations possessed average particle size ranging from 160.40?nm to 743.7?nm with narrow polydispersity index. The encapsulation efficiency was improved by adding the lipid-based surfactants (Labrasol® and Labrafil® M1944CS) to reach 68%. The drug release from the investigated NLC formulations showed a prolonged release up to 12?h. The dermatopharmacokinetic study revealed an improvement in drug deposition in the skin with the optimized DFV-loaded NLC formulation, in contrast to a commercial formulation.

Conclusion: NLC provides a promising nanocarrier system that work as reservoir for targeting topical delivery of DFV.     

Effects of nutrient and light limitation on the biochemical composition of phytoplankton

Three marine phytoplankters (Isochrysis galbana, Chaetoceros calcitrans andThalassiosira pseudonana), commonly used in the culture of bivalve larvae, were grown in batch or semi-continuous cultures. Changes in protein, carbohydrate, lipid and some fatty acids were measured as growth became limited by nitrogen, silicon, phosphorus or light. Under N starvation (2 d) the % lipid remained relatively constant, while% carbohydrate increased and% protein decreased in all 3 species compared to cells growing under no nutrient limitation. Under Si starvation (6 h) there was no change in lipid, protein or carbohydrates. The amount of two fatty acids, 20 : 53 and 22 : 63 remained relatively constant under N, P and Si starvation, exept for a sharp drop in the cells of P-starvedT. pseudonana. However, there were pronounced species differences withI. galbana containing significantly less 20 : 5 3 thanC. calcitrans orT. pseudonana. Under light limitation the amount of lipid per cell showed no consistent trend over a range of irradiances for all 3 species. The amount of N per cell (an index of protein content) as a function of irradiance, was relatively constant forI. galbana andT. pseudonana, while the amount of N per cell was lower under low irradiances forC. calcitrans. These examples of changes in protein, carbohydrate, lipid and certain fatty acids under nutrient (N, Si or P) or light limitation, emphasize the importance of knowing the phase (e.g. logarithmic vs stationary) of the growth curve in batch cultures, since the nutritional value of the phytoplankters could change as cultures become dense and growth is terminated due to nutrient or light limitation.Presented at the XIIIth International Seaweed Symposium, University of British Columbia, Vancouver, Canada, August 1989.     

Bio-shielding <Emphasis Type="Italic">In Situ</Emphasis> Forming Gels (BSIFG) Loaded With Lipospheres for Depot Injection of Quetiapine Fumarate: <Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">In Vivo</Emphasis> Evaluation

Quetiapine fumarate (QF), an anti-schizophrenic drug, suffers from rapid elimination and poor bioavailability due to extensive first-pass effect. Intramuscularly (IM) injected lipospheres were designed to enhance the drug’s bioavailability and extend its release. A central composite design was applied to optimize the liposphere preparation by a melt dispersion technique using Compritol® 888 ATO or glyceryl tristearate as lipid component and polyvinyl alcohol as surfactant. Lipospheres were evaluated for their particle size, entrapment efficiency, and in vitro release. The optimized QF lipospheres were prepared using a Compritol® 888 ATO fraction of 18.88% in the drug/lipid mixture under a stirring rate of 3979 rpm. The optimized lipospheres were loaded into a thermoresponsive in situ forming gel (TRIFG) and a liquid crystalline in situ forming gel (LCIFG) to prevent in vivo degradation by lipases. The loaded gels were re-evaluated for their in vitro release and injectability. Bioavailability of QF from liposphere suspension and bio-shielding in situ gels loaded with QF lipospheres were assessed in rabbits compared to drug suspension. Results revealed that the AUC_0–72 obtained from the liposphere-loaded TRIFG was ～3-fold higher than that obtained from the aqueous drug suspension indicating the bio-shielding effect of Poloxamer® 407 gel to inhibit the biodegradation of the lipospheres prolonging the residence of the drug in the muscle for higher absorption. Our results propose that bio-shielding in situ Poloxamer® 407 gels loaded with lipospheres is promising for the development of IM depot injection of drugs having extensive first-pass metabolism and rapid elimination.     

Interaction of local anesthetics with small phospholipid vesicles investigated by proton NMR spectroscopy

The effects of the local anesthetics tetracaine, procaine (both charged at pH 6), and benzocaine (uncharged) on phospholipid liposomes have been investigated by 500 MHz ¹H NMR Spectroscopy. All the drugs reverse the Pr³⁺ induced shifts of phospholipid resonances in the same sequence as they are shifted by addition of Pr³⁺: choline POCH₂- > choline-CH₂N > choline-N(CH₃)₃ > glycerol > glycerol > acyl C₂ > acyl C₃. The drug effects result from incorporation of positive charges (tetracaine and procaine) and from the induction of a conformational change of the phospholipid head group via an action on the lipid glycerol backbone (benzocaine). From titration experiments with tetracaine on liposomes containing Pr³⁺ inside and outside is derived that the drug passes the bilayer by transverse diffusion. Tetracaine partitions outside/inside at a ratio of 21. Changes in linewidths of the drug resonances when incorporated into the liposomes allow the conclusion that the tetracaine molecule is located in an elongated way between the lipid acyl chains with its nitrogen group near the glycerol backbone. Benzocaine, showing strong effects on the line shapes of the protons on C₂ and C₃ of the lipid acyl chains is also located near the glycerol backbone, the region with the strongest hydrophobic forces.This work was supported by the Deutsche Forschungsgemeinschaft (SFB 30), Cardiology.     

Identification of Residues in the Drug Translocation Pathway of the Human Multidrug Resistance P-glycoprotein by Arginine Mutagenesis

P-glycoprotein (P-gp, ATP-binding cassette B1) is a drug pump that extracts toxic drug substrates from the plasma membrane and catalyzes their ATP-dependent efflux. To map the residues in the drug translocation pathway, we performed arginine-scanning mutagenesis on all transmembrane (TM) segments (total = 237 residues) of a P-gp processing mutant (G251V) defective in folding (15% maturation efficiency) (glycosylation state used to monitor folding). The rationale was that arginines introduced into the drug-binding sites would mimic drug rescue and enhance maturation of wild-type or processing mutants of P-gp. It was found that 38 of the 89 mutants that matured had enhanced maturation. Enhancer mutations were found in 11 of the 12 TM segments with the largest number found in TMs 6 and 12 (seven in each), TMs that are critical for P-gp-drug substrate interactions. Modeling of the TM segments showed that the enhancer arginines were found on the hydrophilic face, whereas inhibitory arginines were located on a hydrophobic face that may be in contact with the lipid bilayer. It was found that many of the enhancer arginines caused large alterations in P-gp-drug interactions in ATPase assays. For example, mutants A302R (TM5), L339R (TM6), G872R (TM10), F942R (TM11), Q946R (TM11), V982R (TM12), and S993R (TM12) reduced the apparent affinity for verapamil by ∼10-fold, whereas the F336R (TM6) and M986R (TM12) mutations caused at least a 10-fold increase in apparent affinity for rhodamine B. The results suggest that P-gp contains a large aqueous-filled drug translocation pathway with multiple drug-binding sites that can accommodate the bulky arginine side chains to promote folding of the protein.The human multidrug resistance P-glycoprotein (P-gp, ATP-binding cassette B1)² is an ATP-dependent drug pump that mediates efflux of a broad range of hydrophobic compounds out of the cell (1). It is expressed in the epithelium of liver, kidney, and gastrointestinal tract and at the blood-brain or blood-testes barrier where it functions to protect us from cytotoxic compounds. It is clinically important because it contributes to multidrug resistance in diseases such as cancer and AIDS (1).P-gp is an ATP-binding cassette transporter of 1280 amino acids that consists of two homologous halves (2). Each half begins with a transmembrane domain (TMD) containing six TM segments followed by a nucleotide-binding domain (NBD).A key goal to understanding the mechanism of P-gp drug transport is to identify the amino acids that line the drug translocation pathway. Because P-gp extracts drug substrates from the lipid bilayer, the drug-binding pocket/drug translocation pathway are predicted to reside in the transmembrane (TM) segments. We previously showed that the TMDs alone were sufficient for drug binding (3). Expression of the TMDs as separate polypeptides showed that both TMD1 and TMD2 were required for binding drug substrate (4). The results of studies utilizing cysteine-scanning mutagenesis and labeling with thiol-reactive drug substrates suggested that all of the TM segments contribute to the drug-binding pocket/drug translocation pathway (reviewed in Ref. 5). The next step is to identify the specific amino acids that line the drug translocation pathway. It is important to identify amino acids that line the drug translocation pathway and to compare whether the biochemical evidence supports a model of P-gp structure in the closed conformation (6) (NBDs close together that was based on the bacterial Sav1866 crystal structure (7)) or the recent crystal structure of mouse P-gp in the open conformation (NBDs far apart) (8). There have been concerns that the mouse P-gp structure may be a non-native structure or in a conformation that exists very transiently (9).Our approach to map the drug translocation pathway has been to use arginine-scanning mutagenesis of the TM segments of a P-gp processing mutant (G251V) that shows partial maturation (∼15% maturation efficiency) (10). Maturation efficiency can be used to detect folding of P-gp in whole cells by monitoring the conversion of P-gp from a core-glycosylated (150 kDa) protein to a mature protein (170 kDa) that contains complex carbohydrate. Because mutant G251V shows partial maturation, we can detect whether an introduced arginine promotes, inhibits, or has a neutral effect on folding. The rationale for using arginine-scanning mutagenesis was that arginine has a large free energy barrier (17 kcal/mol) for insertion into the lipid bilayer because it is highly charged (11). Therefore, introduction of an arginine into a lipid face of the G251V mutant would likely inhibit maturation, whereas an arginine introduced into the aqueous face of the drug translocation pathway would not inhibit maturation of the mutant P-gp.In an initial study on TM1, we demonstrated the feasibility of the approach (10). All arginines introduced into the predicted lipid-facing positions inhibited maturation, whereas those introduced into positions predicted to face the drug translocation pathway did not. A particularly intriguing observation was that some arginines promoted maturation. The residues at these positions were coincidentally at positions identical to those that reacted with thiol-reactive drug substrates in cysteine-scanning mutagenesis studies and were found to be within the drug-binding pocket (10, 12). This suggested that arginine-scanning mutagenesis could be a useful approach for identifying residues in the drug translocation pathway and for determining the orientation of the TM segments in the membrane.Arginines that promote maturation appear to identify positions that are important for P-gp-drug interactions because they appear to mimic drug rescue of P-gp. It was also found that the ability of arginines (such as I306R in TM5) to promote maturation involved global enhancement of P-gp folding rather than simply compensating for a localized mutation (such as G251V) because other processing mutants could also be rescued (12). Because these arginine mutations enhance folding of P-gp in general, they will be described as enhancer rather than suppressor arginines. In this study we performed arginine-scanning mutagenesis on TMs 2–12 of P-gp processing mutant G251V to determine their orientations in the membrane and to identify residues that line the drug translocation pathway.     

Effects of protein binding on a lipid bilayer containing local anesthetic articaine, and the potential of mean force calculation: a molecular dynamics simulation approach

Articaine, as a local anesthetic drug has been simulated in neutral and charged forms, and its interaction with the dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane is investigated by molecular dynamics simulation using GROMACS software. In order to obtain the optimum location of the drug molecules, as they penetrate into the membrane, umbrella sampling is applied and the free energy is calculated. The effect of protein binding to DMPC membrane on the process of drug diffusion through the membrane is considered. Five simulation systems are designed and by applying the potential of mean force, the molecular dynamics simulation on the system is performed. In light of the obtained results, the electrostatic potential, variation of lipid bilayer’s order parameter and the diffusion coefficient of drug are discussed.

Augmented simvastatin cytotoxicity using optimized lipid nanocapsules: a potential for breast cancer treatment

Context: We noticed paucity in exploiting solutol-based lipid nanocapsules in statins formulations though they carry all favorable properties that are needed for cancer passive targeting such as their small particle size, stealth properties, ability to highly accommodate lipophilic drugs, good internalization and P-gp pump inhibition.

Objective: The aim of this study was to design and optimize new simvastatin drug delivery systems; lipid nanocapsules intended for administration through the intravenous route as potential treatment for breast cancer.

Methods: Optimized nanocapsules were prepared by the phase-inversion method according to a D-optimal mixture design, characterized and assessed for their cytotoxicity.

Results: Three successful models for particle size, polydispersity index (PDI) and percentage of drug released after 48 h were generated. The prepared lipid nanocapsules acquired spherical and homogenous morphology, good stability and tolerance to sterilization. The obtained release profiles demonstrated desired sustained release pattern. Furthermore, testing selected formulations on human breast cancer adenocarcinoma cells showed augmented cytotoxicity of simvastatin reaching low IC50 values as 1.4?±?0.02 μg/ml compared to the pure drug.

Conclusion: The proposed lipid nanocapsules pose promising candidates as simvastatin carriers intended for the targeting of breast cancer.     

Modulating Drug Release and Enhancing the Oral Bioavailability of Torcetrapib with Solid Lipid Dispersion Formulations

The development of drug dispersions using solid lipids is a novel formulation strategy that can help address the challenges of poor drug solubility and systemic exposure after oral administration. The highly lipophilic and poorly water-soluble drug torcetrapib could be effectively formulated into solid lipid microparticles (SLMs) using an anti-solvent precipitation strategy. Acoustic milling was subsequently used to obtain solid lipid nanoparticles (SLNs). Torcetrapib was successfully incorporated into the lipid matrix in an amorphous state. Spherical SLMs with mean particle size of approximately 15–18 μm were produced with high drug encapsulation efficiency (>96%) while SLNs were produced with a mean particle size of 155 nm and excellent colloidal stability. The in vitro drug release and the in vivo absorption of the solid lipid micro- and nanoparticles after oral dosing in rats were evaluated against conventional crystalline drug powders as well as a spray dried amorphous polymer dispersion formulation. Interestingly, the in vitro drug release rate from the lipid particles could be tuned for immediate or extended release by controlling either the particle size or the precipitation temperature used when forming the drug-lipid particles. This change in the rate of drug release was manifested in vivo with changes in Tmax as well. In addition, in vivo pharmacokinetic studies revealed a significant increase (∼6 to 11-fold) in oral bioavailability in rats dosed with the SLMs and SLNs compared to conventional drug powders. Importantly, this formulation approach can be performed rapidly on a small scale, making it ideal as a formulation technology for use early in the drug discovery timeframe.Electronic supplementary materialThe online version of this article (doi:10.1208/s12249-015-0299-8) contains supplementary material, which is available to authorized users.KEY WORDS: anti-solvent precipitation, controlled release, formulation, nanoparticles, solid lipid     

Nadph-initiated cytochrome P450-dependent free iron-independent microsomal lipid peroxidation: Specific prevention by ascorbic acid

In this paper we demonstrate that ascorbic acid specifically prevents NADPH-initiated cytochrome P450 (P450)-mediated microsomal lipid peroxidation in the absence of free iron. Lipid peroxidation has been evidenced by the formations of conjugated dienes, lipid hydroperoxide and malondialdehyde. Other scavengers of reactive oxygen species including superoxide dismutase, catalase, glutathione, -tocopherol, uric acid, thiourea, mannitol, histidine, -carotene and probucol are ineffective to prevent the NADPH-initiated P450-mediated free iron-independent microsomal lipid peroxidation. Using a reconstituted system comprised of purified NADPH-P450 reductase, P450 and isolated microsomal lipid or pure L--phosphatidylcholine diarachidoyl, a mechanism has been proposed for the iron-independent microsomal lipid peroxidation and its prevention by ascorbic acid. It is proposed that the perferryl moiety P450 Fe³⁺. O₂ initiates lipid peroxidation by abstracting methylene hydrogen from polyunsaturated lipid to form lipid radical, which then combines with oxygen to produce the chain propagating peroxyl radical for subsequent formation of lipid peroxides. Apparently, ascorbic acid prevents initiation of lipid peroxidation by interacting with P450 Fe³⁺. O₂. (Mol Cell Biochem 166: 35-44, 1997)     

Nonclassical and Endogenous Cannabinoids: Effects on the Ordering of Brain Membranes

The effects of several nonclassical cannabinoids and the endogenous cannabinoid ligand, anandam-ide on the lipid ordering of rat brain synaptic plasma membranes (SPM) were examined and compared to ⁹-tetrahydrocannabinol (⁹-THC). SPM order was determined using fluorescence polarization. All compounds tested affected membrane ordering. ⁹-THC, CP-55,940, CP-55,244 and WIN-55212 decreased lipid ordering in SPM. Some stereospecificity was observed with ⁹-THC and WIN-55212, but not other compounds. Anandamide also decreased lipid order as did its putative precursor, arachidonic acid. In contrast to these compounds, levonantradol increased SPM lipid order. Although all pharmacologically active cannabinoids affect SPM lipid order, potency on this measure does not correlate well with their pharmacological potency. The results of this study suggest that membrane perturbation (either increases or decreases in lipid order) may be a necessary characteristic for cannabinoid pharmacological activity, but it is not a primary or sufficient determinate of action for this class of drugs.     

Some similarities between processes at biological membranes and lipid bilayers

Several processes at biological membranes can be simulated by experiments with artificial lipid bilayer membranes. Three selected examples are discussed: The uncoupler induced proton permeability of lipid bilayers, the initiation of action potential like voltage responses in lipid membranes, and the reconstitution of active cation pumps across planar lipid bilayers or lipid vesicles.Paper presented at the Biomembrane Symposium of the Deutsche Gesellschaft für Biophysik, Freiburg, April 1975.Supported by Deutsche Forschungsgemeinschaft, SFB 38 Membranforschung.     

D-penicillamine affects lipid peroxidation and iron content in the rat brain cortex

d-Penicillamine, a trifunctional aminoacid known for its ability to form metal complexes and for being a radical scavenger, has been investigated in vitro and in vivo in the rat brain cortex. At 50 M the drug facilitate lipid hydroperoxides and TBARS formation in brain cortex homogenates, while at higher concentrations a clear inhibition of the lipid peroxidative process was observed. The activity of thed-penicillamine (25 and 50 mg/Kg i.p) was evaluated in vivo after a 7-day treatment in rats in whose brain cortex a slow process of lipid peroxidation was induced by iron-saccharate injection. Lipid hydroperoxides, lipid soluble fluorescent compounds and the iron content of both iron-injected and contralateral hemicortices showed a significant decrease in comparison to rats untreated withd-penicillamine. The higher dose also induced in normal rats a significant decrease in basal TBARS and iron content of the brain cortex. In the iron-injected cortex the observed Fe²⁺/Fe³⁺ ratio was significantly different from that of normal rats. On the contrary ratios obtained formd-penicillamine treated animals were higher in comparison to both normal and iron-injected animals. These results suggest thatd-penicillamine, acting as a reducing agent, inhibits the iron redox system and, as a chelating agents, can remove metal from action sites where lipid peroxidation may occur.     

Formulation and <Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">In Vivo</Emphasis> Evaluation of Lipid-Based Terbutaline Sulphate Bi-layer Tablets for Once-Daily Administration

The objective of this study was to prepare and evaluate terbutaline sulphate (TBS) bi-layer tablets for once-daily administration. The bi-layer tablets consisted of an immediate-release layer and a sustained-release layer containing 5 and 10 mg TBS, respectively. The sustained-release layer was developed by using Compritol®888 ATO, Precirol® ATO 5, stearic acid, and tristearin, separately, as slowly eroding lipid matrices. A full 4?×?2² factorial design was employed for optimization of the sustained-release layer and to explore the effect of lipid type (X ₁), drug–lipid ratio (X ₂), and filler type (X ₃) on the percentage drug released at 8, 12, and 24 h (Y ₁, Y ₂, and Y ₃) as dependent variables. Sixteen TBS sustained-release matrices (F1–F16) were prepared by melt solid dispersion method. None of the prepared matrices achieved the targeted release profile. However, F2 that showed a relatively promising drug release was subjected to trial and error optimization for the filler composition to develop two optimized matrices (F17 and F18). F18 which consisted of drug–Compritol®888 ATO at ratio (1:6 w/w) and Avicel PH 101/dibasic calcium phosphate mixture of 2:1 (w/w) was selected as sustained-release layer. TBS bi-layer tablets were evaluated for their physical properties, in vitro drug release, effect of storage on drug content, and in vivo performance in rabbits. The bi-layer tablets showed acceptable physical properties and release characteristics. In vivo absorption in rabbits revealed initial high TBS plasma levels followed by sustained levels over 24 h compared to immediate-release tablets.     

The evolutionary significance of phase-separated microsystems

The source, preparation, and properties of phase-separated systems such as lipid layers, coacervate droplets, sulphobes, and proteinoid microspheres are reviewed. These microsystems are of interest as partial models for the cell and as partial or total models for the protocell. Conceptual benefits from study of such models are: clues to experiments on origins, insights into principles of action and, in some instances, presumable models of the origin of the protocell. The benefits to evolution of organized chemical units are many, and can in part be analyzed. Ease of formation suggests that such units would have arisen early in primordial organic evolution. Integration of these various concepts and the results of consequent experiments have contributed to the developing theory of the origins of primordial and of contemporary life.Invited paper. Presented at the International Seminar Origin of Life, 2–7 August 1974, Moscow, U.S.S.R.     

Development,Optimization, and Evaluation of Carvedilol-Loaded Solid Lipid Nanoparticles for Intranasal Drug Delivery

Carvedilol, a beta-adrenergic blocker, suffers from poor systemic availability (25%) due to first-pass metabolism. The aim of this work was to improve carvedilol bioavailability through developing carvedilol-loaded solid lipid nanoparticles (SLNs) for nasal administration. SLNs were prepared by emulsion/solvent evaporation method. A 2³ factorial design was employed with lipid type (Compritol or Precirol), surfactant (1 or 2% w/v poloxamer 188), and co-surfactant (0.25 or 0.5% w/v lecithin) concentrations as independent variables, while entrapment efficiency (EE%), particle size, and amount of carvedilol permeated/unit area in 24 h (Q ₂₄) were the dependent variables. Regression analysis was performed to identify the optimum formulation conditions. The in vivo behavior was evaluated in rabbits comparing the bioavailability of carvedilol after intravenous, nasal, and oral administration. The results revealed high drug EE% ranging from 68 to 87.62%. Carvedilol-loaded SLNs showed a spherical shape with an enriched core drug loading pattern having a particle size in the range of 66 to 352 nm. The developed SLNs exhibited significant high amounts of carvedilol permeated through the nasal mucosa as confirmed by confocal laser scanning microscopy. The in vivo pharmacokinetic study revealed that the absolute bioavailability of the optimized intranasal SLNs (50.63%) was significantly higher than oral carvedilol formulation (24.11%). Hence, we conclude that our developed SLNs represent a promising carrier for the nasal delivery of carvedilol.     

The Improvement of the Anticancer Effect of a Novel Compound Benzoic Acid, 2-Hydroxy-, 2-d-ribofuranosylhydrazide (BHR) Loaded in Solid Lipid Nanoparticles

A novel drug delivery system consisting of benzoic acid, 2-hydroxy-, 2-d-ribofuranosylhydrazide (BHR)-loaded solid lipid nanoparticles (BHR-SLNs) was prepared using the emulsification–evaporation technique. The mean particle size of the BHR-SLNs measured by photon correlation spectroscopy was about 75 nm. BHR-SLN morphology was assessed by transmission electron microscopy and atomic force microscopy. The drug entrapment efficiency was 70.2%, as determined via Sephadex gel chromatography and high-performance liquid chromatography. Drug release assessment in vitro showed that BHR was gradually released from SLNs in a time-dependent manner. Furthermore, treatment of 293T and Hela cells with BHR-SLNs demonstrated that BHR-SLNs were less toxic to normal cells while more effective in antitumor potency compared with the BHR drug alone. The results imply that BHR-SLNs could be considered as a promising antitumor drug system for a range of new therapeutic applications.KEY WORDS: benzoic acid, 2-hydroxy-, 2-d-ribofuranosylhydrazide (BHR); controlled release; drug delivery; solid lipid nanoparticles