[Techniques and methods evaluation on pharmaceutical stability of liposomes].

Liposomes as a drug carrier is easy to form aggregation and cause drug leakage in vitro. In addition, the degradation and elimination in vivo happens frequently to reduce its delivery activity. Development and application of liposomes are restricted by the instability. The appropriate techniques and methods are great important in the study of pharmaceutical stability of liposomes. In this paper, the techniques and methods are reviewed on pharmaceutical stability evaluation of liposomes, which was done from physical, chemical and biological stability for the difference in stability of liposomes. The research strategies for establishing the stability evaluation system and improving the value of liposomes have been discussed to make full therapeutic advantage of it.

[Poly(ß-amino esters)-based barriers for tumor targeted delivery system].

Poly(ß-amino esters) (PBAE) are used for drug carrier and have many advantages, such as pH-sensitivity, low toxicity, structural diversity and the synthetic method of PBAE is easy. Therefore they are possessed broad application prospect in tumor-targeted drugs delivery systems. In this paper, the structural features and target drugs delivery property of PBAE are reviewed. The application forms of PBAE and different anti-cancer drugs loaded in the copolymer for tumor-targeted drugs delivery systems are introduced particularly.

Preparation and characterization of stable pH-sensitive vesicles composed of α-tocopherol hemisuccinate.

The current study aims to develop a stable pH-sensitive drug delivery system. First, cleavable polyethylene glycol-α-tocopherol hemisuccinate (PEG-THS) was synthesized. Conventional pH-sensitive vesicles composed of the Tris salt of α-tocopherol hemisuccinate (THST) were then prepared using the detergent removal technique. The vesicles had a mean particle size of (163.8 ± 5.5) nm and a zeta potential of -74.5 ± 6.4 mV. The THST vesicles were then modified using PEG-THS or uncleavable PEG-cholesterol (PEG-CHOL) (THST/PEG-lipids, 100:6 molar ratio). The mean vesicle particle size and absolute zeta potential decreased with increasing PEG-THS proportion. When the pH was decreased, the vesicle particle size and calcein release rate increased. The THST vesicles were initially Ca(2+)-unstable but exhibited significantly improved stability after modification with PEG-THS, especially at PEG-lipid ratios above 6%. Incubation in an acid serum increased the calcein release rate of conventional THST vesicles to 45 ± 1.98% at 10 min. However, the release rate of the PEG-CHOL vesicles remained low. The calcein release rate of PEG-THS vesicles was between those of conventional and PEG-CHOL-V. Therefore, PEG-THS can protect vesicles in serum and reconstitute their pH sensitivity in acidic conditions. Cleavable PEG-THS can be used in stable pH-sensitive preparations without loss of pH sensitivity. Free calcein and conventional vesicles eliminated from the plasma soon after injection, as well as the half-life (t(1/2)) and area under the curve of PEG-THS-V encapsulating calcein, were dramatically increased. This phenomenon indicates that the use of PEG-lipid derivatives has gained a favorably long circulation effect in mice.

[Rheological properties of poloxamer 407 aqueous solutions].

Rheological properties of poloxamer 407 (brand named Pluronic F127) were examined by changing shear rate, temperature and the recovery properties of apparent viscosity after heating for several times. The results indicated that poloxamer 407 aqueous solution showed a Newtonian behavior at a low concentration while it might be a pseudoplastic fluid when the concentration reached a certain point. The thixotropy and the sol-gel transition temperature decreased with increasing the concentration (it could be an in situ gel at body temperature when the concentration of poloxamer 407 up to 15.25%). The results that obtained from the theological data would be useful in the application of poloxamer 407 such as in situ gel preparation.

[The characterisitics of temperature/pH sensitive block copolymer micelles in vitro].

The dialysis method was employed to prepare blank and doxorubicin (DOX) loaded micelles formed by temperature- and pH- sensitive polyhistidine-co-polyDL-lactide-co-glycolide-co-polyethyleneglycol-co-polyDL-lactide-co-glycolide-co-polyhistidine (PHis-b-PLGA-b-PEG-b-PLGA-b-PHis). The critical micelle concentrations (CMC) of the copolymers were measured with Pyrene Fluorescent Probe Technique. The temperature- and pH- sensitive properties of the blank micelles solution were investigated by optical transmittance measurement. The morphology and diameter of DOX micelles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The entrapment rate and drug-loading rate were determined with dialysis method. The in vitro release study was further performed to examine the temperature- and pH-responsive drug release behavior from DOX-loaded micelles. The results indicated that the CMC, entrapment efficiency and drug-loaded amount of the micelles were 7.5 x 10(-3) g x L(-1), 85.2 +/- 3.1% and 10.4 +/- 4.5%, respectively. The DOX micelle was globular-shaped with a mean diameter of 91.1 +/- 15.8 nm. The transmittance of micelle solution consistently increased with the increasing temperature or decreasing pH. In comparison to the drug release profile at physiological conditions (37 degrees C, pH 7.4), the DOX-loaded micelles showed faster drug release rate at higher temperature (41 degrees C), lower pH (pH 7.0, pH 6.5, pH 5.0) or higher temperature and lower pH (41 degrees C, pH 5.0). This indicated that the micelles showed a temperature and pH-triggered drug release pattern. Base on the above results, it can be concluded that PHis-b-PLGA-b-PEG-b-PLGA-b-PHis block copolymer micelles which respond to temperature and pH stimuli are promising smart carriers for anti-tumor drugs with the advantages of temperature- and pH- triggered drug release.

DOX-loaded PEG-PLGA and Pluronic copolymer composite micelles enhances cytotoxicity and the intracellular accumulation of drug in DOX-resistant tumor cells.

In the present study, doxorubicin (DOX) loaded polyethyleneglycol-poly (DL-lactic-co-glycolic acid) micelle as well as composite micelles composed polyethyleneglycol- poly(DL-lactic-co-glycolic acid) (PEG-PLGA) and Pluronic 105 (P105) were constructed. The micelles, with diameter around 106 nm and 85 nm respectively, were prepared by solvent evaporation method. The results showed that the encapsulation of DOX in micelles could significantly enhance its cytotoxicity in a DOX resistant tumor cell line, K562/DOX. The combination of PEG-PLGA and Pluronic further improved both the tumor-suppressive activity and the intracellular accumulation of DOX, indicating that the composite micelles would be potential to reverse the multidrug resistance in tumor cells.

[Recent advances in the study of accelerated blood clearance phenomenon of PEGylated liposomes].

It is generally believed that liposomes modified with polyethylene glycol (PEG) have no or lower immunogenicity. However, based on many recent literatures, when the PEGylated liposomes were repeatedly applied to the same animal, the immune responses occurred. The first injection of PEGylated liposomes resulted in a reduction in the circulation time and an increase in hepatic and splenic accumulation of the second dose of PEGylated liposomes in a time-interval, which was called "accelerated blood clearance (ABC)" phenomenon. Such immunogenicity of PEGylated liposomes presents a barrier in the research of liposomal formulations and their use in the clinics. This review focused on the definition, the method of verification, the development of the reason for ABC phenomenon, influencing factors of ABC phenomenon, and discussed if other PEGylated nanocarriers also induce ABC phenomenon.

[Preparation of adriamycin-loaded temperature/pH sensitive self-assembly block copolymer micelles].

The dialysis method was employed to load adriamycin into the micelles formed by temperature and pH sensitive polyhistidine-co-DL-lactide-co-glycolide-polyethylene glycol poly DL-lactide-co-glycolide-co-histidine (OLH-b-PLGA-b-PEG-b-PLGA-b-OLH). The critical micelle concentration (CMC) of the copolymer was measured with pyrene fluorescent probe method under different temperatures. The entrapment rate and drug-loading rate were determined with dialysis method. The diameter, morphology and surface potential of the copolymer micelles were investigated by corresponding instruments, respectively. The release behavior of adriamycin from copolymer micelles and the pH sensitivity were studied. The CMC of the copolymers ranged from 0.022 4 to 0.001 7 microg x mL(-1). The entrapment rate and drug-loading rate were 92.8% and 15.7%, respectively. The micelles have a mean diameter of (61.7 +/- 13.4) nm, and zeta potential was -9.88 mV. The in vitro adriamycin release rate increased with the pH dropping from 7.4 to 5.0. The results indicated that the CMC of the copolymers decreased as the raising of temperature, drug release behavior from the micelles possessed clearly pH sensitivity, and the copolymers may have a potential in targeted delivery system for anticancer drugs.

Use of surgical glue for Mason type III radial head fractures: A case report.

RATIONALE: A Mason type III radial head fracture, which is characterized by comminuted fragments of the radial head, is a severe injury. Open reduction and internal fixation (ORIF) is an alternative treatment method; however, the technique of using an on-table reduction in combination with surgical glue is rarely reported. PATIENT CONCERNS: A 48-year-old man was admitted to our department with complaints of elbow pain after falling down. Elbow radiography and computed tomography (CT) demonstrated characteristics of fractures before the operation. DIAGNOSIS: Radiographic images showed a Mason type III radial head fracture. INTERVENTIONS: The patient underwent ORIF at our hospital. During the operation, the technique of on-table reconstruction combined with surgical glue was used. OUTCOMES: The patient recovered well and was able to participate in his usual work. LESSONS: Mason type III radial head fractures could be treated with ORIF, and a satisfactory result could be anticipated, thus avoiding a radial head replacement or resection. Anatomical reduction of a comminuted radial head could be obtained via an on-table reconstruction and application of surgical glue.

[Recent advances in the study of cleavable PEG-lipid derivatives modifying liposomes].

Polyethylene glycol (PEG) lipid derivatives could increase the stability of liposomes in vivo and in vitro and prolong the circulation time of liposomes in vivo. However, the chemical bond between PEG and lipid was so stable that liposomes modified with traditional PEG-lipid derivatives could not release their contents at targeted tissue immediately and the pharmacodynamic effect was reduced. The concept of cleavable PEG-lipid was raised in recent years and these PEG-lipid derivatives could break under physiological or pathological condition. The cleavable PEG-lipid derivatives could prolong the circulation time of liposomes, and after arriving at targeted location, PEG fragment had cleaved from the surface of liposomes, so liposomes could bind with pathological cells and release contents into cells. Removal of the protective polymer layer is necessary once the liposome close to the tumour to allow to fuse and release drug. Attempts have been made to increase the circulation time and reconstitute the cellular affinity of liposomes by incorporating PEG-lipid derivatives. This review focused on the kinds of cleavable PEG-lipid derivatives, types of cleavage, the application feature to liposomes and the advantages and localizations.

[Progress in the study of pH and temperature sensitive biodegradable block copolymers].

pH and temperature sensitive biodegradable block copolymers are some macromolecules connected by biodegradable materials and pH sensitive monomers according to a certain sequence, or biodegradable polyesters polymerized themselves. On the basis of pertinent documents, the development of pH and temperature sensitive biodegradable block copolymers was introduced, involving their mechanism of action and potential application. PH and temperature sensitive biodegradable block copolymers could control the drug release rate freely, avoiding burst effect. Besides, the biocompatibility of these biodegradable materials is also excellent. So the use of pH and temperature sensitive biodegradable block copolymers as biodegradable drug delivery devices has attracted considerable interest in the intelligent drug delivery system.

[Preparation of docetaxel-loaded pH-sensitive block copolymer micelles].

Basing on the synthesis of pH-sensitive amphiphilic block copolymer poly (2-ethyl-2-oxazoline)-poly (D, L-lactide)(PEOz-PDLLA), this paper presents the preparation of docetaxel-loaded pH-sensitive block copolymer micelles using film dispersion method. The critical micelle concentration (CMC) was measured by pyrene fluorescent probe technique. The entrapment efficiency and drug-loaded amount were determined by HPLC. The morphology, diameter and surface potential of the micelles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential analyzer, respectively. The in vitro release behavior of DTX from polymeric micelles was investigated using dialysis method. The results indicated that the CMC, drug-loaded amount and entrapment efficiency of the micelles was 1.0 x 10(-3) g x L(-1), 15.0% and 91.1%, respectively. The micelles had a narrow size distribution, with a mean diameter of 28.7 nm. The micelle was globular-shaped and its zeta potential was (1.19 +/- 0.12) mV. In pH 7.4 PBS, docetaxel was released in a sustained manner from the micelles; while in PBS at pH 5.0, drug was released more rapidly, which suggested the pH-sensitive drug release behavior of the PEOz-PDLLA micelles. According to all the studies above, it can be concluded that the PEOz-PDLLA block copolymer micelles may be applied as promising drug delivery system for hydrophobic anti-tumor drugs.

[Preparation of tetrandrine alginate calcium sustained release gel pellets].

OBJECTIVE: To prepare tetrandrine alginate calcium sustained release gel pellets twice daily with Eudragit RS 30D and Eudragit RL 30D. METHODS: The sustained release gel pellets were prepared by fluid bed technique and release in vitro was selected as the evaluate index. The formulation was optimized by full design test based on the studies of coating factors. RESULTS: The optimal coating formulation was shown at the ratio of Eudragit RS 30D and Eudragit RL 30D to 5:1, the loading weight of polymers of 45%, the plasticizer concentration of 20% and 35% talcum powder. CONCLUSION: The perfect sustained release of tetrandrine pellets can be obtained by adjusting the ratio of Eudragit RS 30D and Eudragit RL 30D and the loading weight of polymers.

[Preparation and study in vitro of long-circulating nanoliposomes of curcumin].

OBJECTIVE: To prepare the long-circulating nanoliposomes of curcumin. METHOD: The long-circulating nanoliposomes were prepared by ethanol infusion and the encapsulation efficiency was determindated by the mini-column centrifugation. The effect of some factors on the encapsulation efficiency, such as the buffer solutions, the weight ratio of curcumin to SPC, the weight ratio of SPC to Chol, the pH of buffer solution and the iron strength of water phase, was investigated respectively. Then the formulation was optimized by orthogonal design. RESULT: The encapsulation efficiency of the curcumin liposomes was (88.27 +/- 2.16)%, and the average diameter of the liposomes was (136 +/- 18) nm. There was no change on encapsulation efficency within 30 d. CONCLUSION: The preparation of curcumin liposomes was easy and practicable and the pharmaceutical characterization showed that the curcumin liposomes are stable.

Preparation of the traditional Chinese medicine compound recipe Shuxiong sustained-release capsules by multiparticulate time-controlled explosion technology.

In this study the traditional Chinese medicine compound recipe (TCMCR) Shuxiong sustained-release capsules (SXSRC) were prepared by multiparticulate time-controlled explosion technology. First, Shuxiong pellets were prepared with the refined medicinal materials containing in the recipe of Shuxiong tablets. Then, the pellets were coated sequentially with an inner swelling layer containing low-substituted hydroxypropylcellulose as the swelling agent and an outer rupturable layer of ethylcellulose. Finally, SXSRC were developed by encapsulating five kinds of pellets whose respective coating level of outer layer was 0%, 9%, 15%, 18% and 20% at equivalent ratio in hard gelatin capsules. Under the simulated gastrointestinal pH conditions, the in vitro release test of SXSRC was carried out. The value of similarity factor (f2) of hydroxysafflor yellow A and Panax notoginseng saponins, hydroxysafflor yellow A and ferulic acid, Panax notoginseng saponins and ferulic acid was 90.1, 77.3, 87.0, respectively. The release profiles of these three compositions from SXSRC showed a characteristic of obvious sustained-release and no significant difference between them. The results indicated that using multiparticulate time-controlled explosion technology various components in TCMCR with vastly different physicochemical properties could be released synchronously while sustained-releasing. That complies with the organic whole conception of compound compatibility of TCMCR.

[Preparation and anti-oxidative activity of liposomal ferulic acid].

Ferulic acid (FA) was loaded into liposomes via calcium acetate gradient with (80.2 +/- 5.2)% entrapment efficiency. The average sizes of blank liposome and FA liposome were about 155 nm and 154 nm, respectively. The zeta potential of blank liposome and FA liposome were (13.14 +/- 1.67) mV and (4.12 +/- 0.05) mV, respectively. Unilamellar vesicles were present in freeze-fracture electron microscopy. In the pharmacodynamic studies, the protective effect of liposomal ferulic acid on tBHP-challenged U937 cells was measured with the morphology of cell injury, mitochondrial transmembrane potential alternation and cell viability assay used as index. The results of MTT assay, microscopy indicated that FA liposomes exhibited greater antioxidant activity than FA solution on U937 cell.

[Preparation and in vitro tumor cells selectivity of sterically stabilized immunoliposomal peptides in bee venom].

Recently the use of peptides in bee venom (PBV) for cancer therapy has attracted considerable attention. In this study, the sterically stabilized liposomal PBV (PBV-SL) was prepared using soybean phosphatidylcholine, cholesterol, and cholesterol-PEG-COOH. The humanized antihepatoma disulfide-stabilized Fv (hdscFv25) was coupled to sterically stabilized liposomes using the N-hydroxysuccinimide ester method. The hdscFv25-immunoliposomes (SIL[hdscFv25]) were immunoreactive as determined by ELISA assay. SIL[hdscFv25] showed higher tumor cells selectivity. PBV-SIL[hdscFv25] can kill SMMC-7721 cells in vitro with higher efficiency than non-targeted liposomes. Whereas cytotoxicties were compared for Hela cells, no significant differences was observed between PBV-SIL[hdscFv25] and PBV-SL. Sterically stabilized immunoliposomal peptides in bee venom could be one drug targeting delivery system.

[Preparation of lectin-conjugated PLGA nanoparticles and evaluation of their in vitro bioadhesive activity].

In this study, wheat germ agglutinin (WGA), tomato lectin (TL) and asparagus pea lectin (AL) were covalently coupled to conventional poly lactic-co-glycolic acid (PLGA) nanoparticles using a carbodiimide method to take the bioadhesive properties. The influences of the amounts of activating agents and lectins, as well as the activating time and incubating time on the effect of lectin conjugating were investigated to optimize the preparation conditions. The mean diameters of the performed nanoparticles with or without lectin conjugation ranged from (140.7 +/- 5.7) nm to (245.6 +/- 18.3) nm. The yields of lectin conjugating and the lectin surface concentrations on nanoparticles were determined by Lowry's methods, and were calculated to be (18.97 +/- 2.9)% - (20.15 +/- 2.4)% and (9.46 +/- 1.45)--(10.05 +/- 1.19) microg x mg(-1), respectively. The in vitro bioadhesive activities of nanoparticles were evaluated by pig gastric mucin (PM) binding experiments. After incubation at room temperature for 60 min, the equilibria of binding between nanoparticles and PM reached. The percentages of the bulk PM which had interacted with different lectin-conjugated PLGA nanoparticles were 15.5%, 12.1% and 11.8%, respectively. The conjugation of lectin enhanced the interaction about 2.4 - 3.2 fold compared with that of the non-conjugated one. A mathematical model was used based on the Langmuir equation, and the rate constants of interaction (k) were calculated to be 2.373 x 10(-3), 1.536 x 10(-3) and 1.714 x 10(-3) (microg x min/mL)(-1), respectively. These interactions could be competitively inhibited by their corresponding sugars of lectins. The results suggested that lectin-conjugated PLGA nanoparticles greatly promoted the interaction with PM in vitro compared with the conventional PLGA nanoparticles, thus would improve the bioadhesion on gastrointestinal mucosa after oral administration resulting in a prolonged residence time in the gastrointestinal tract.

Novel, nano-sized, liposome-encapsulated polyamidoamine dendrimer derivatives facilitate tumour targeting by overcoming the polyethylene glycol dilemma and integrin saturation obstacle.

Drug delivery systems (DDSs) commonly employ arginine-glycine-aspartic acid (RGD) peptides with polyethylene glycol (PEG)-dependent enhanced permeability and retention (EPR) effect to optimise tumour-targeting. However, the PEG dilemma and integrin saturation obstacle are major challenges. To address these issues, we constructed a novel, nano-sized DDS by encapsulating doxorubicin (DOX)-loaded folic acid derivatives of polyamidoamine dendrimer (PAMAM G5.0) in cyclic RGD-tyrosine-lysine pentapeptide (c[RGDyK])-modified liposomes (RGD-SL[FND/DOX]), prepared using thin-film hydration, film-dispersion and hydration-sonication. The liposomes were PEGylated, sterically stabilised and pH-sensitive. In vitro, RGD-SL[FND/DOX] showed pH-sensitive holistic FND/DOX release, and pH-dependent uptake and cytotoxicity in human cancer KB cells. At pH 7.4, RGD-SL[FND/DOX] demonstrated greater cellular uptake and cytotoxicity than relevant control formulations (except FND/DOX) did, although this advantage disappeared at pH 6.5. In vivo, RGD-SL[FND/DOX] inhibited S180 sarcoma xenografted tumour growth in Kunming mice more effectively than FND/DOX did. These findings demonstrate the feasibility of constructing double-stage tumour-targeting nano-sized DDSs such as RGD-SL[FND/DOX]. c[RGDyK] and the EPR effect, facilitated by the particle size (about 110 nm) and PEGylation, helped to target the DDS to the tumour tissue, while the subsequent pH-dependent release of FND/DOX and folic acid-mediated endocytosis specifically targeted the tumour cells, thereby overcoming the PEG dilemma and integrin saturation obstacle.

Synthesis of a novel galactosylated lipid and its application to the hepatocyte-selective targeting of liposomal doxorubicin.

This paper described the synthesis of a novel galactosylated lipid with mono-galactoside moiety, (5-Cholesten-3beta-yl) 4-oxo-4-[2-(lactobionyl amido) ethylamido] butanoate (CHS-ED-LA), and the targetability of doxorubicin (DOX), a model drug, in liposomes containing 10% mol/mol CHS-ED-LA (galactosylated liposomes, GalL) to the liver was studied. The weighted-average overall drug targeting efficiency (Te(*)) was used to evaluate the liver targetability of GalL DOX. The results showed that GalL DOX gave a relatively high (Te(*))(liver) value of 64.6%, while DOX in conventional liposome (CL DOX) only gave a (Te(*))(liver) value of 21.8%. In the liver, the GalL DOX was mainly taken up by parenchymal cells (88% of the total hepatic uptake). Moreover, preinjection of asialofetuin significantly inhibited the liver uptake of GalL DOX (from 70 to 12% of the total injected dose). It was suggested that liposomes containing such novel galactosylated lipid, CHS-ED-LA, had a great potential as drug delivery carriers for hepatocyte-selective targeting.