Preparation and pharmacokinetics in rabbits of breviscapine unilamellar vesicles

The purpose of the study was to prepare the unilamellar liposomal vesicles of breviscapine (Breviscapine-LUVs) and investigate the pharmacokinetics of Breviscapine-LUVs in rabbits. Breviscapine-LUVs were prepared by the film dispersion method and treated further by extrusion. Its size distribution and zeta potential were determined by photon correlation spectroscopy. The encapsulation efficiency (EE) and cumulative release of Breviscapine-LUVs were assayed by the dialysis method. The crossover design (two periods) was used in six rabbits, which were administered Breviscapine-LUVs and reference preparation. Results showed that the particle size of Breviscapine-LUVs was 50.8 nm, and the polydispersity index was 0.287. The zata potential was -24 mV ± 9 mV(n = 3), and the EE% was 81.1 ± 1.1% (n = 3). The cumulative release of vesicles in 0.9% NaCl was 17.2 ± 0.78%, 26.1 ± 0.68%, and 29.9 ± 0.81% in 2, 8, and 24 h, respectively. The mean concentration-time curves of breviscapine liposomes and reference preparation were both fitted to a two-compartment model with the main pharmacokinetic parameters as follows: t_1/2β of Breviscapine-LUVs and reference preparation were (42.5 ± 28.6) min and (6.01 ± 4.64) min, respectively; CL_(s) were (15.3 ± 9.03) mL × min^-1 and (84.6 ± 40.6) mL × min^-1, respectively; AUC_0-300 were (1267 ± 1083) μg × min × mL^-1 and (196 ± 107) μg × min × mL^-1, respectively. Compared with the reference preparation, breviscapine liposomes had a much higher concentration in plasma and contained characteristic of sustained-release, which ameliorated the pharmacokinetic properties of scutellarin.     

Vesicles and Liposomes: A Self‐Assembly Principle Beyond Lipids

This Progress Report describes the latest advances in vesicles and liposomes. Recent work on the self‐assembly of complex polymer systems shows that the formation of polymer vesicles or closed hull structures is archetypal, leading to fascinating new possibilities and applications in materials science. A general view of the underlying self‐assembly mechanisms leading to vesicles and the control of size, shape, and other vesicular properties by physicochemical means is presented, as background. This is followed by an overview of the recently described new classes of polymer and supramolecular tectons that make vesicle formation a more general phenomenon going beyond just lipids. Finally, the potential applications of vesicles, including non‐lipid vesicles, are outlined.     

灯盏花素注射液指纹图谱的建立及质量相关性研究

目的：应用高效液相色谱法建立灯盏花素注射液指纹图谱。方法：Hanbon C18（5μm,250nm×4.6nm）,柱温25℃,检测波长335nm,流速为1ml.min-1,流动相：甲醇（A）-0.4%磷酸缓冲液（B）梯度洗脱。结果：确定了不同批次灯盏花素指纹图谱的特征指纹图谱及相似度。结论：本方法稳定可靠,重复性好,可...     

Preparation,Characterization, and Pharmacokinetics of Sterically Stabilized Nimodipine-Containing Liposomes

ABSTRACT

Nimodipine is a dihydropyridine calcium antagonist used in clinical trials in the treatment of ischemic damage in subarachnoid hemorrhage and commercially available as nimotop® intravenous infusion solution and tablets. However, due to its poor solubility in water, intravenous administration depends on the use of the dehydrated alcohol to achieve a clinically relevant concentrated infusion solution while the low bioavailability of the nimotop® tablets were far away from content. We have prepared a well-characterized novel lyophilized liposome-based nimodipine formulation that is sterile and easy-to-use. Of the several formulations examined, nimodipine-liposomes composed of ePC/CHOL 20:3 and co-surfactant poloxamer 188/sodium deoxycholate/ePC/3:0.3:5 were chosen for further studies. This composition was found to give more stable liposomes than other formulations. It gave 89.9% entrapment efficiency and particle size of 200 nm after lyophilization. The pharmacokinetic parameters following orally and intravenously administration to New Zealand rabbits were determined and compared with those of commercial nimodipine formulations. Encapsulation of nimodipine in liposomes produced marked differences over those of commercial preparations with an increased C_max, prolonged elimination half-life, and an increased value for AUC. The obtained values for mean residence time (MRT) indicated that nimodipine remains longer for liposomal formulation. Thus an optimum i.v. liposome formulation for nimodipine can be developed for an alternative to the commercial nimodipine preparations.     

3D Probed Lipid Dynamics in Small Unilamellar Vesicles

Single‐molecule fluorescence correlation spectroscopy overcomes the resolution barrier of optical microscopy (10≈–20 nm) and is utilized to look into lipid dynamics in small unilamellar vesicles (SUVs; diameter < 100 nm). The fluorescence trajectories of lipid‐like tracer 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindodicarbocyanine (DiD) in the membrane bilayers are acquired at a single‐molecule level. The autocorrelation analysis yields the kinetic information on lipid organization, oxygen transport, and lateral diffusion in SUVs' membrane. First, the isomerization feasibility may be restricted by the addition of cholesterols, which form structure conjugation with DiD chromophore. Second, the oxygen transport is prevented from the ultrasmall cluster and cholesterol‐rich regions, whereas it can pass through the membrane region with liquid‐disordered phase (L_d) and defects. Third, by analyzing 2D spectra correlating the lipid diffusion coefficient and triplet‐state lifetime, the heterogeneity in lipid bilayer can be precisely visualized such as lipid domain with different phases, the defects of lipid packing, and DiD‐induced “bouquet” ultrasmall clusters.     

Phospholipid‐Free Small Unilamellar Vesicles for Drug Targeting to Cells in the Liver

It is reported that cholesterol (Chol) and TWEEN 80 at a molar ratio of 5:1 can form small unilamellar vesicles (SUVs) using a staggered herringbone micromixer. These phospholipid‐free SUVs (PFSUVs) can be actively loaded with a model drug for targeting hepatocytes via the endogenous apolipoprotein mechanism. PFSUVs particles with compositions of Chol:TWEEN 80 ranging between 1.5:1 and 5:1 (mol/mol) can be produced with a mean diameter of ≈80 nm, but only the high‐Chol formulations (3:1 and 5:1) can retain a transmembrane gradient of ammonium sulfate for active loading of doxorubicin (DOX). Under cryo‐transmission electron microscopy, PFSUVs‐DOX displays a unilamellar bilayer structure with DOX molecules forming spindle‐shape aggregates inside the aqueous core. Relative to PEGylated liposomal doxorubicin (PLD) that exhibits little interaction with cells in various conditions, the cellular uptake of PFSUVs‐DOX is dependent on the presence of serum and enhanced with an increased concentration of apolipoproteins. After intravenous injection, the vast majority of PFSUVs‐DOX accumulates in the liver and DOX is detected in all liver cells (predominantly the hepatocytes), while PLD is captured only by the sinusoidal cells (i.e., macrophages). This report discloses an innovative lipid bilayer vesicle for highly efficient and selective hepatocyte targeting.     

Key Role of Choline Head Groups in Large Unilamellar Phospholipid Vesicles for the Interaction with and Rupture by Silica Nanoparticles

For highly abundant silica nanomaterials, detrimental effects on proteins and phospholipids are postulated as critical molecular initiating events that involve hydrogen-bonding, hydrophobic, and/or hydrophilic interactions. Here, large unilamellar vesicles with various well-defined phospholipid compositions are used as biomimetic models to recapitulate membranolysis, a process known to be induced by silica nanoparticles in human cells. Differential analysis of the dominant phospholipids determined in membranes of alveolar lung epithelial cells demonstrates that the quaternary ammonium head groups of phosphatidylcholine and sphingomyelin play a critical and dose-dependent role in vesicle binding and rupture by amorphous colloidal silica nanoparticles. Surface modification by either protein adsorption or by covalent coupling of carboxyl groups suppresses the disintegration of these lipid vesicles, as well as membranolysis in human A549 lung epithelial cells by the silica nanoparticles. Furthermore, molecular modeling suggests a preferential affinity of silanol groups for choline head groups, which is also modulated by the pH value. Biomimetic lipid vesicles can thus be used to better understand specific phospholipid–nanoparticle interactions at the molecular level to support the rational design of safe advanced materials.     

Pharmacokinetics of Ketoprofen After Intravenous and Intramuscular Administrations to Rabbits

Abstract

The pharmacokinetics of ketoprofen was studied in rabbits following intravenous and intramuscular administrations of ketoprofen, both at a dose of 4.0 mg.Kg^-1. Plasma levels of ketoprofen, as a function of time, were determined by a reversed-phase high performance liquid chromatography. The disposition of ketoprofen was described by a two-compartment open model with elimination from the central compartment. A model-independent method using the statistical moment theory was also applied. Pharmacokinetics of ketoprofen was characterized as a drug with terminal half-life of 3.15 hr, low apparent volumes of distribution (V = 0.031 L.Kg^-1, Vd_ss = 0.070 L.Kg^-1 and Vd_β = 0.130 L.Kg^c-1). The mean residence time (MRT) was found to be 1.44 hr for i.v. injection and 2.86 hr for i.m. injection. The clearance (CL) and apparent volume of distribution at steady state (Vd_ss) after i.v. injection was determined to be 0.027 L.Kg^-1.hr^-1 and 0.03 9 L.Kg^-1, respectively. The absorption rate constant from the limb muscle site into systemic circulation was calculated to be 2.19 hr^-1 and peak plasma concentration after i.m. injection was observed to be at 0.31 ± 0.11 hr. The systemic availability of ketoprofen after intramuscular administration was determined to be 0.38, relative to the equal i.v dose.     

Pharmacokinetics of Ketoprofen After Intravenous and Intramuscular Administrations to Rabbits

The pharmacokinetics of ketoprofen was studied in rabbits following intravenous and intramuscular administrations of ketoprofen, both at a dose of 4.0 mg.Kg^-1. Plasma levels of ketoprofen, as a function of time, were determined by a reversed-phase high performance liquid chromatography. The disposition of ketoprofen was described by a two-compartment open model with elimination from the central compartment. A model-independent method using the statistical moment theory was also applied. Pharmacokinetics of ketoprofen was characterized as a drug with terminal half-life of 3.15 hr, low apparent volumes of distribution (V = 0.031 L.Kg^-1, Vd_ss = 0.070 L.Kg^-1 and Vd_β = 0.130 L.Kg^c-1). The mean residence time (MRT) was found to be 1.44 hr for i.v. injection and 2.86 hr for i.m. injection. The clearance (CL) and apparent volume of distribution at steady state (Vd_ss) after i.v. injection was determined to be 0.027 L.Kg^-1.hr^-1 and 0.03 9 L.Kg^-1, respectively. The absorption rate constant from the limb muscle site into systemic circulation was calculated to be 2.19 hr^-1 and peak plasma concentration after i.m. injection was observed to be at 0.31 ± 0.11 hr. The systemic availability of ketoprofen after intramuscular administration was determined to be 0.38, relative to the equal i.v dose.     

Preparation and Pharmacodynamic Evaluation of Liposomes of Indomethacin

The side effects of indomethacin, such as ulceration of the kidney and central nervous system (CNS) toxicity, limit its use as a drug for rheumatoid arthritis. Encapsulation of this drug in liposomes may reduce the toxic effects. The aim of this study was to determine the factors influencing encapsulation of indomethacin in liposomes and to determine anti-inflammatory potential of liposomal indomethacin. A series of liposomal formulations of indomethacin were prepared using various phospholipids. The effects of method of preparation, lipid composition, charge, and cholesterol (CH) on encapsulation of indomethacin in liposomes were investigated. A significant variation in encapsulation of the drug in liposomes was observed when prepared by different methods. With all the methods of preparation tried, the favorable lipid compositn for high encapsulation of this drug was egg phosphatidyl choline:CH:stearlyamine (PC:CH:SA) at a 1:0.5:0.1 molar ratio. Inclusion of cholesterol did not affect the encapsulation efficiency of the drug in liposomes. The drug release profile from the liposomes was biphasic, and the highest percentage drug release was observed with large unilamellar vesicles (LUVs) (100 nm). Inclusion of steary-Ujylamine (PC:CH:SA 1:0.5:0.1) and phosphatidyl glycerol (PG) (PC:CH:PG:1:0.5:0.2) in the liposomes reduced the release of the drug in comparison to the neutral liposomes (PC:CH 1:1). The slow release of the drug from stearylamine-containing liposomes may be explained by the electrostatic interaction between the acid moiety of the drug and the amine moiety of the lipid. It is assumed that the possible hydrogen bonding between –OH groups of phosphatidyl glycerol and the –COOH group of the drug might be the reason for the slow release of the drug from PC:CH:PG (1:0.5:0.2) containing liposomes. Pharmacodynamic evaluation of the liposomes was performed by carrageenan-induced rat paw edema (acute) and adjuvant arthritis (chronic) models. The anti-inflammatory activity was increased from the first to fifth hour PC:CH:PG (1:0.5:0.2) and PC:CH:SA(1:0.5:0.1) liposomes showed the highest percentage inhibition of edema. In both these models, anti-inflammatory activity of liposomal indomethacin was significantly higher than that of free indomethacin (p <. 01). The ulcer index of the free drug was about three times more than the encapsulated drug when administered at the same dose intraperitoneally to arthritic rats consecutively for 21 days.     

Preparation, characterization, and pharmacokinetics of sterically stabilized nimodipine-containing liposomes

Nimodipine is a dihydropyridine calcium antagonist used in clinical trials in the treatment of ischemic damage in subarachnoid hemorrhage and commercially available as nimotop^® intravenous infusion solution and tablets. However, due to its poor solubility in water, intravenous administration depends on the use of the dehydrated alcohol to achieve a clinically relevant concentrated infusion solution while the low bioavailability of the nimotop^® tablets were far away from content. We have prepared a well-characterized novel lyophilized liposome-based nimodipine formulation that is sterile and easy-to-use. Of the several formulations examined, nimodipine-liposomes composed of ePC/CHOL 20:3 and co-surfactant poloxamer 188/sodium deoxycholate/ePC/3:0.3:5 were chosen for further studies. This composition was found to give more stable liposomes than other formulations. It gave 89.9% entrapment efficiency and particle size of 200 nm after lyophilization. The pharmacokinetic parameters following orally and intravenously administration to New Zealand rabbits were determined and compared with those of commercial nimodipine formulations. Encapsulation of nimodipine in liposomes produced marked differences over those of commercial preparations with an increased C_max, prolonged elimination half-life, and an increased value for AUC. The obtained values for mean residence time (MRT) indicated that nimodipine remains longer for liposomal formulation. Thus an optimum i.v. liposome formulation for nimodipine can be developed for an alternative to the commercial nimodipine preparations.     

Pharmacokinetics of Khellin in Rabbits: Oral,Intravenous, and Intramuscular Administrations

Abstract

This study was undertaken to investigate the pharmacokinetics of khellin in rabbits following oral, intravenous, and intramuscular administrations. Analysis of khellin in the plasma samples was performed according to a previously developed HPLC method. The data obtained from the rapid intravenous administration experiments fitted the two-compartment open model with β, α, total body clearance (TBC), and volume of central compartment (V_c) of 0.0306 hr^?1, 1.93 hr^?1, 573 ml. hr^?1.kg^?1, and 2.1 liter. kg^?1, respectively. The concentration-time profiles acquired following the administration of sugar-coated tablets of khellin were typical of sustained release formulations with time to peak concentration (t_max) and dose-normalized peak plasma concentration (C_max) of 21 hr and 23 ng. ml^?1.mg^?1.kg, respectively. With the exception of one animal, rapid absorption was obtained following the intramuscular or oral suspension administration with (t_max) ranging from 0.083 to 4 hr. A complete absorption was obtained with intramuscular injection, whereas, the fraction of dose absorbed following oral suspension administration was 38%.     

Preparation, characterization, and stability of liposome-based formulations of mitoxantrone

The preparation, characterization, and stability of lyophilized liposome-based formulation of mitoxantrone was investigated. Mitoxantrone was entrapped inside small, unilamellar liposomes composed of dioleoylphosphocholine (DOPC), cholesterol, and cardiolipin. The mean vesicle size and drug entrapment efficiency of the liposomes were ~ 150 nm and ~ 99%, respectively. Less than 1% of drug was lost and mean vesicle size remained unchanged after sterile filtration. The pre-lyophilized (pre-lyo) formulations were characterized by a differential scanning calorimetric (DSC) method. Results showed that the glass transition temperatures (Tg') increased as the molar ratios of sucrose:lipid and trehalose:lipid in the formulations were increased. The maximum Tg' of the pre-lyo formulations containing 10:1 sucrose:lipid and trehalose:lipid molar ratios were - 37°C and - 41°C, respectively. After reconstitution of the lyophilized cake of the sucrose-containing formulation, the mean vesicle size was comparable to pre-lyo liposome size. In vitro release studies showed that less than 2% of mitoxantrone was released after an extensive dialysis against phosphate buffered saline (PBS) at 37°C, indicating that the mitoxantrone was highly associated and retained inside the liposomes. Short-term stability studies of the sucrose-containing formulations revealed that the reconstituted and eight-fold diluted formulations were stable for up to 8 hours at room temperature. Long-term stability studies of lyophilized liposomal mitoxantrone showed that the lyophilized formulation was stable for up to 13 months after storage at refrigerated condition.     

Preparation,in Vitro and in Vivo Evaluation of Liposomal/Niosomal Gel Delivery Systems for Clotrimazole

Clotrimazole, which is an imidazole derivative antifungal agent, was widely used for the treatment of mycotic infections of the genitourinary tract. To develop alternative formulation for the vaginal administration of clotrimazole to provide sustained and controlled release of appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of liposomes/niosomes with regard to size and entrapment efficiency, multilamellar liposomes/niosomes containing drug were prepared by lipid hydration method. The prepared liposomes/niosomes were incorporated into 2% carbopol gel, and the systems were evaluated for drug stability in phosphate-buffered saline (pH 7.4) and simulated vaginal fluid at 37 ± 1°C. Further, the vesicle gel system was evaluated by antifungal activity and tolerability on tissue level in rat.     

Preparation, in Vitro and in Vivo Evaluation of Liposomal/Niosomal Gel Delivery Systems for Clotrimazole

Clotrimazole, which is an imidazole derivative antifungal agent, was widely used for the treatment of mycotic infections of the genitourinary tract. To develop alternative formulation for the vaginal administration of clotrimazole to provide sustained and controlled release of appropriate drug for local vaginal therapy, liposomes/niosomes were evaluated as delivery vehicles. To optimize the preparation of liposomes/niosomes with regard to size and entrapment efficiency, multilamellar liposomes/niosomes containing drug were prepared by lipid hydration method. The prepared liposomes/niosomes were incorporated into 2% carbopol gel, and the systems were evaluated for drug stability in phosphate-buffered saline (pH 7.4) and simulated vaginal fluid at 37 ± 1°C. Further, the vesicle gel system was evaluated by antifungal activity and tolerability on tissue level in rat.     

Preparation and Characterization of pH-Sensitive Vesicles Made of Cholesteryl Hemisuccinate

pH-sensitive vesicles are designed to promote efficient release of entrapped agents in response to low pH. In this study, such vesicles were prepared from cholesteryl hemisuccinate (CHEMS) in Tris-HCl buffer. Vesicles prepared by this direct hydration method had a small particle size of 74.1 nm based on intensity of Gaussian and a size of 65.8 nm based on volume of Gaussian. The mean zeta potential was about –73mV, indicating that the vesicle system was stable. Entrapment efficiency for calcein by these vesicles was measured at 37 ± 2.36%, which is higher than that by phospholipid MLVs. These calcein loaded vesicles exhibited excellent stability at pH 7.4 and underwent rapid destabilization upon acidification as showed by calcein release. However these vesicles were unstable in Fetal Bovine Serum (FBS). Optimization of formulation might improve their stability in serum.     

Preparation,optimization, characterization,and stability studies of salicylic acid liposomes

Salicylic acid has been used widely in the treatment of dry skin conditions and also helps reduce acne symptoms. However, it suffers from the disadvantages of being a mild to strong irritant. Hence, its control can be achieved through encapsulation in liposomes. Liposomes were prepared by the conventional thin film hydration technique as described by Bangham et al. (J. Mol. Biol., 1965). The prepared liposomal dispersions were then characterized for entrapment efficiency, particle size by transmission electron microscopy (TEM), phase transition studies by differential scanning calorimetry (DSC), and lamellarity by nuclear magnetic resonance (NMR). The results showed the formation of bilayered liposomes in the particle size range of 0.2-0.8276 µm with a maximum entrapment efficiency of 42.6%. The liposomes stored at 4-5°C demonstrated maximum stability as compared to those stored at any other temperature.     

Recent Biophysical Issues About the Preparation of Solute-Filled Lipid Vesicles

Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.