Preparation and evaluation of bilayer-core osmotic pump tablets contained topiramate.

Topiramate (TPM) was an antiepileptic agent commonly used in clinical. Studies showed that an oral preparation of TPM with extended-release manner could bring some benefits for epileptics. In this paper, controlled release push-pull osmotic pump (PPOP) tablets of sparingly water-soluble TPM were successfully prepared. This bi-layer tablet core mainly consisted of sodium chloride as osmotic promoting agent and polyethylene oxide as suspending and pushing agents. The influences of osmotic agents, pushing agents and the compositions of coating membrane on TPM release profiles were evaluated. An optimal formulation of TPM-PPOP was obtained through single-factor experiments. In vitro release tests showed that the optimum formulation could release TPM at an approximate zero-order rate up to 8 h. Pharmacokinetic behaviors of TPM-PPOP tablets were evaluated and compared with the immediate release capsules after an oral single dose in beagle dogs. Pharmacokinetics results demonstrated that the TPM-PPOP tablet was able to provide a prolonged release of TPM with longer tmax and mean residence time. Lower fluctuations of drug plasma levels could also be achieved with TPM-PPOP tablets. These results suggested that sparely water-soluble drugs as TPM can be designed to PPOP for efficacy and safety use.

Dual stimulus of hyperthermia and intracellular redox environment triggered release of siRNA for tumor-specific therapy.

Small interfering RNA (siRNA) offers a new and potential therapeutic strategy for tackling many diseases at the molecular level. Recently, cell-penetrating peptides (CPPs) conjugated with siRNA via disulfide-bonds (designated as siRNA-CPPs) were reported to form glutathione-sensitive carriers. However, non-cell specificity, CPPs degradation and the unwanted reduction of siRNA-CPPs before reaching the targeted tissue in vivo hampered the development of siRNA-CPPs. Herein, utilizing the dual stimulus of hyperthermia and the intracellular redox environment, we devised a thermosensitive liposome (TSL) containing an Asparagine-Glycine-Arginine (NGR) peptide and reducible siRNA-CPPs for tumor-specific siRNA transfection (siRNA-CPPs/NGR-TSL), in which siRNA-CPPs were "caged" in NGR-TSL to overcome their limitations in vivo. The functional nanocarrier possessed a small particle size of approximately 90nm, a high drug encapsulation efficiency of approximately 86% and good serum stability. Both free siRNA-CPPs and siRNA-CPPs/NGR-TSL (preheated) silenced c-myc in human fibrosarcoma (HT-1080) cells in vitro. However, in an HT-1080 xenograft murine model, siRNA-CPPs/NGR-TSL with hyperthermia displayed superior in vivo antitumor efficacy (about 3-fold) and gene silencing efficiency (about 2-fold) compared with free siRNA-CPPs under hyperthermia. This study demonstrates that the constructed vesicle in combination with hyperthermia could greatly improve the in vivo stability of siRNA-CPPs and synergistically enhance its cancer therapy efficiency.

Preparation, characterization, and pharmacodynamics of thermosensitive liposomes containing docetaxel.

A novel thermosensitive liposome (TL) containing docetaxel (DTX) was designed to enhance DTX-targeted delivery and antitumor effect. TL loading DTX (DTX-TL) were prepared by thin film hydration. The mean particle size of the liposomes was about 100 nm, and the drug entrapment efficiency was more than 95%. The phase transition temperature of liposomes was about 42 °C. In vitro drug release showed that drug released at 37 °C was obviously less than that at 42 °C. For in vivo experiments, the human breast tumor model was established by subcutaneous xenotransplantation on nude mice; liposomes and injection containing DTX were injected i.v. in nude mice, followed by exposure of the tumors to hyperthermia (HT) for 30 min after administration. The tumor inhibition ratio of DTX-TL group was significantly higher than the normal injection group. Combining TL with HT enhanced the delivery of DTX and thereby its antitumor effects. The liposomes reported in this paper could potentially produce viable clinical strategies for improved targeting and delivery of DTX for the treatment of breast cancer.

Improving efficiency of adriamycin crossing blood brain barrier by combination of thermosensitive liposomes and hyperthermia.

Adriamycin (ADM)-encapsulated thermosensitive liposomes (ts-lip-ADM) and common liposomes (lip-ADM) were developed and evaluated. The encapsulation efficiency of the two liposomes were above 99%, and the average sizes of liposomes were about 120 nm. Temperature-dependent drug release from loaded liposomes in vitro was investigated: more than 90% of loaded ADM was released from ts-lip-ADM within 30 min at 42°C, while less than 3% was released from lip-ADM at 42°C beyond 120 min. An in vitro model of blood brain barrier (BBB) was established and evaluated by permeability and transendothelial electrical resistance (TEER). The model was employed to study the permeability of liposomes in vitro. The permeability of ts-lip-ADM could be increased significantly after the temperature was raised to 42°C, which was about 10-16, 22-38, 38-45, 50-105 fold to that of ts-lip-ADM (37°C), lip-ADM (42°C), lip-ADM (37°C) and free ADM, respectively. C6 glioma-bearing mice model was developed and used to evaluate body distribution and anti-tumor efficacy in vivo. Mice were IV injected at a drug dose of 10 mg/kg. After administration the heads of mice were heated in water bath at 42°C for 30 min. The maximum brain concentration of ts-lip-ADM was 6.4, 3.7 fold compared with that of ADM solution and lip-ADM, respectively. The survival time of mice administered ts-lip-ADM (44 d) was remarkably longer than that of other three groups. This study indicates that ADM-encapsulated thermosensitive liposomes combined hyperthermia could enhance ADM delivery across BBB and prolong survival time of glioma-bearing mice.