Yingjie Deng

Oil-based formulations for oral delivery of insulin

Several oil‐based solution formulations of insulin were prepared, in which insulin was solubilized in the form of anhydrous reverse micelles. The preparation process involved micellar dissolution of insulin followed by freeze drying, then reconstitution of lyophilized product with an oil phase. These formulations were stable at room temperature for up to 12 months. No significant changes in the appearance were observed and no degradation products of insulin were detected during the course of the stability study. The efficacy of these formulations was evaluated in‐vivo using diabetic Wistar rat as an animal model and then a specific formulation was chosen for further study in non‐diabetic New Zealand rabbits. It was found that the efficacy of insulin oil solution was dose dependent and insulin oil solution had the same efficacy as insulin emulsion with the same formulation composition. If ethylene‐diaminetetraacetic acid (EDTA) was pre‐delivered 40 min before the delivery of insulin oil solution, the hypoglycaemic effect of insulin oil solution was greatly enhanced, with an AUC (% glucose reduced) value increase from 28.5 ± 14.7 to 167.1 ± 72.3. The improvement of oral absorption induced by pre‐delivery of EDTA might be attributed to enzyme inhibition, reduced gut mobility and the opening of paracellular routes.

Lyophilization of water-in-oil emulsions to prepare phospholipid-based anhydrous reverse micelles for oral peptide delivery.

A novel procedure for the preparation of hydrophilic peptide-containing oily formulations involving the freeze-drying of water-in-oil emulsions (FWE) is described. A mixture of an aqueous phase containing insulin and oil phase containing phosphatidylcholine was emulsified to prepare water-in-oil emulsions, which were subsequently lyophilized. Upon addition of oil, the lyophilates formed a clear oily solution which was considered as an anhydrous reverse micelle (ARM) system since it contained no water but 20-nm insulin nanoparticles, as revealed by dynamic light scattering. The 20-nm insulin nanoparticles, existing in a crystal form, were also contained in the lyophilates, as proved by scanning electron microscopy, small angle X-ray scattering and differential scanning calorimetry analysis. The drug release from the oily formulation of SPC/insulin (10:1) was slow and less than 12% of the total insulin was released after 24h. A significant reduction in the plasma glucose level of fasting diabetic rats after oral administration of insulin-containing ARMs confirmed the bioactivity of the drug and the potential usefulness of phospholipid-based oily formulations. Both the ARMs and lyophilates were stable and could be stored at 4 degrees C for at least 6 months. Thus, this simple FWE procedure is suitable for the solubilization of hydrophilic peptides in oil to produce stable products for therapeutic applications.

Studies on the encapsulation of oxymatrine into liposomes by ethanol injection and pH gradient method.

ABSTRACT Oxymatrine is the major active alkaloid constituent extracted from traditional Chinese herb medicine Sophora flavescens Ait (Kushen) and Sophora alopecuroides (Kudouzi). In recent years, oxymatrine had been found to posses remarkable anti-hepatic activity and has been used for treating hepatitis B in clinical therapy in China. In this study, we attempted to entrap oxymatrine into liposomes to facilitate the delivery of oxymatrine to the liver and enhance the therapeutic efficiency for hepatitis. Preformulation investigation was performed to obtain the drug physicochemical properties such as solubility, pKa, and logP for rational liposomes preparation design. Liposomes were prepared with soybean lecithin by ethanol injection and pH gradient loading methods. At the same time the factors affecting the entrapment efficiencies were investigated and compared. Ethanol injection method yielded liposomes with entrapment efficiency less than 20%. The lipid composition and aqueous medium had some effects on entrapment efficiency. However, liposomes could be produced with entrapment efficiency above 50% by pH gradient method. The internal pH buffer capacity, the lipid composition, and drug-to-lipid ratio greatly influenced the entrapment efficiency, while the incubation temperature had almost no effect on entrapment efficiency in the active loading procedure.

Preparation of hydrophobic drugs cyclodextrin complex by lyophilization monophase solution.

ABSTRACT A novel method was evaluated for preparation of hydrophobic drugs cyclodextrin (CD) complex in this study. To obtain sterilized drug-CD complex lyophilized powder for injection or other purpose, the CD solution in water and the hydrophobic drug in tertiary butyl alcohol (TBA) were mixed in a suitable volume ratio, filtered through 0.22 μm millpores, and subsequently freeze-dried. A high drug concentration was obtained in the co-solvent due to the good solvency of TBA, which is miscible with water in any proportion, for hydrophobic drugs. Moreover, TBA could be removed rapidly and completely by freeze-drying because of its high vapor pressure and high melting point. The chemical stability of some labile active compounds was also improved in TBA-water co-solvent. Based on the data from differential scanning calormetry (DSC) and X-ray diffractometry (XRD), drug was amorphous in freeze-dried complex. The fourier transform infrared spectra indicated drug-CD interaction was present in drug-CD complex. An enhanced dissolution rate was also obtained in drug-CD complex. These results proved drug-CD complex had been formed after this technique. Thus, this report provided a simple, efficient, and economic technique for preparation of hydrophobic drugs CD complex, which may be useful practically in modifying hydrophobic drugs physicochemical properties and improving their absorption and pharmacodynamics.

N-Trimethyl chitosan-coated multivesicular liposomes for oxymatrine oral delivery

Background: Multivesicular liposomes (MVLs), uncoated and coated with N-trimethyl chitosan (TMC), have been studied for their potential use for drug delivery by the oral route. Method: Synthesized TMC was characterized by infrared spectroscopy, revealing the presence of trimethyl groups, and by proton nuclear magnetic resonance spectroscopy, allowing the calculation of the degree of substitution quaternization (70.2%). Oxymatrine (OM), a natural quinolizidine alkaloid used clinically for treating hepatitis B, was chosen as a model drug. The surface-modified MVLs and uncoated MVLs were characterized in vitro in terms of their shape, size, zeta potential, entrapment efficiency, coating efficiency, the stability of MVLs in polymer suspension, and the stability in simulated gastric and intestinal fluids. Results: In vivo, the area under the plasma concentration–time curve obtained from the pharmacokinetics study of TMC-coated MVLs was found to be about 3.26- and 1.96-fold higher than that of OM solution and uncoated MVLs, respectively. Conclusion: TMC-coated MVLs can be considered as a potential carrier for oral drug administration.

Liposomes incorporating sodium deoxycholate for hexamethylmelamine (HMM) oral delivery: Development, characterization, and in vivo evaluation

Liposomes incorporating sodium deoxycholate (NaDC) were prepared by the method of reverse phase evaporation and used for drug delivery by the oral route. Hexamethylmelamine (HMM), an anti-tumor agent, was chosen as a model drug and encapsulated into liposomes incorporating NaDC (NaDC-Lip). Several properties of NaDC-Lip containing HMM (HMM NaDC-Lip), such as particle size, entrapment efficiency, pinacyanol chloride (PIN) spectral characteristics with various molar ratio of NaDC/PC, as well as the vesicle stability measurements with calcein were evaluated. In vivo, the area under the plasma concentration–time curve obtained from the pharmacokinetics study of HMM NaDC-Lip was found to be ~ 9.76- and 1.21-fold higher than that of HMM solution and HMM Lip, respectively, indicating that NaDC-Lip can be used as a potential carrier for oral drug administration.

Modulation of the physicochemical state of interior agents to prepare controlled release liposomes

To prepare controlled release liposomes, freeze-drying of double emulsions (FDE) was employed to entrap a model drug, topotecan, which has been reported to tend to leak rapidly from vesicles. In addition, hydrogenated soy phosphatidylcholine (HSPC), N-(carbonyl-methoxypolyethyleneglycol2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (PEG-PE), and cholesterol (3:1:1, mass ratio) were used as the vesicle lipid. Different inner aqueous phases (W1) containing topotecan together with a variety of chemicals, such as citrate, sulfate, and divalent copper ions, were used to prepare W1/O/W2 double emulsions, which were then freeze-dried to obtain dry products. Upon rehydration, the dry products formed topotecan-entrapping unilamelar liposomes with an encapsulation efficiency of 80% and a mean diameter of less than 200nm. The in vitro release experiments demonstrated that the drug release of topotecan-entrapping FDE liposomes could be successfully controlled through altering the state of the incorporated drug by means of protonation, precipitation, or forming a transition metal-complex. Specifically, the formulation of 300mM CuSO(4) had a drug release half-life of 36h. This novel method is a promising way to prepare controlled release liposomes that are more suitable for therapeutic application. In addition, the liposome formation mechanism was discussed based on micrographs and the size of the double emulsions and vesicles, as well as the small angle X-ray scattering pattern and transmission electron microscopy images.

Development and pharmacokinetics of nimodipine-loaded liposomes.

In order to improve the water solubility of nimodipine and prolong the time of the drug in the circulation, nimodipine‐loaded liposomes with a small size and high entrapment efficiency were prepared by a method that was easy to scale up (the modified ethanol injection method). The nimodipine liposome dispersions were characterized with respect to particle size distribution, zeta potential and entrapment efficiency. Liposomal nimodipine and nimodipine solution were intravenously administered to mice as a single dose of 4 mg kg−1. The pharmacokinetic parameters of nimodipine changed significantly when encapsulated in liposomes. The clearance of nimodipine encapsulated in liposomes was reduced and the elimination half‐life was prolonged. The ratios of the area under the curve values of nimodipine liposomes to nimodipine solution were 1.78 and 1.90 in plasma and cerebral tissue, respectively. The drug concentration in cerebral tissue and in plasma showed a good linear correlation, which showed that liposomes could efficiently deliver nimodipine into brain tissue. These findings suggest that intravenous administration of liposomal nimodipine produces higher and more stable plasma and cerebral drug concentrations compared with nimodipine solution. In conclusion, liposomal nimodipine is a promising alternative to the solution preparation.

Degradation kinetics of fluorouracil-acetic-acid-dextran conjugate in aqueous solution.

ABSTRACT The degradation kinetics of fluorouracil-acetic-acid-dextran conjugate (FUAC-dextran) was investigated in various buffer solutions with different pH value and physiological saline solution at 60°C and 37°C, respectively. The hydrolytic reaction displayed pseudo-first-order degradation kinetics. Hydrolytic rate constant obtained was the function of pH value and independent of species of buffering agents. The smallest rate constant was observed at pH round 3.00. The activation energy of the hydrolytic reaction was estimated from Arrhenius equation as 88.73 ± 6.00 kJ·mol−1. The special base catalytic degradation of the conjugate was observed from acidic to slight alkaline condition and the special base catalytic rate constants were calculated. The conjugate was more stable in physiological saline than that in buffer solution at pH 7.00 or 9.00 at 37°C. The results revealed that the conjugate was stable in acidic condition and will degrade in alkaline condition.

Freeze Drying of Double Emulsions to Prepare Topotecan-Entrapping Liposomes Featuring Controlled Release

Topotecan-entrapping liposomes were prepared by freeze drying double emulsions with hydrogenated soy phosphatidylcholine, N-(carbonyl-methoxypolyethyleneglycol2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine, and cholesterol. Different inner aqueous phases of different pH values containing topotecan together with different chemicals, such as citrate and sulfate, were used to modify the physicochemical state of the drug to prepare W1/O/W2 double emulsions that were then freeze dried to obtain dry products. Upon rehydration, the dry products, which were stable for at least 6 months, formed into unilamellar liposomes with a high encapsulation efficiency of up to 80% and a mean diameter below 200 nm. The in vitro release experiments demonstrated that different formulations displayed different drug release properties. Thus, stable submicron unilamellar topotecan-entrapping liposomes can be prepared by freeze drying double emulsions, and the drug release can be successfully controlled by altering the physicochemical state of the incorporated drug.