Shanshan Tong

Enhancement of oral bioavailability of the poorly water-soluble drug silybin by sodium cholate/phospholipid-mixed micelles

AbstractAim:To evaluate a mixed micellar drug delivery system composed of sodium cholate and phospholipid for oral administration of silybin, a promising hepatoprotectants.Methods:The optimum formulation of sodium cholate/phospholipid-mixed micelles containing silybin was obtained based on the study of pseudo-ternary phase diagram. The dissolution of silybin-mixed micelles was investigated. The pharmacokinetic characteristics and bioavailability after oral administration of silybin-mixed micelles and silybin-N-methylglucamine were compared in dogs.Results:The mean particle size of prepared mixed micelles was 75.9±4.2 nm. The largest solubility of silybin was found to be 10.0±1.1 mg/mL in the optimum formulation of mixed micelles. The silybin-sodium cholate/phospholipid-mixed micelles showed a very slow release of silybin 17.5% (w/w) within 72 h in phosphate buffer (pH 7.4) and 15.6% (w/w) in HCl solution (pH 1.2). After oral administration to dogs, the relative bioavailability of mixed micelles versus silybin-N-methylglucamine in dogs was 252.0%.Conclusion:Sodium cholate/phospholipid-mixed micelles are promising carriers in orally delivery of silybin, considering their capability of enhancing bioavailability and large-scale production.

Proliposomes for oral delivery of dehydrosilymarin: preparation and evaluation in vitro and in vivo

Aim:To formulate proliposomes with a polyphase dispersed system composed of soybean phospholipids, cholesterol, isopropyl myristate and sodium cholate to improve the oral bioavailability of dehydrosilymarin, an oxidized form of herbal drug silymarin.Methods:Dehydrosilymarin was synthesized from air oxidation of silymarin in the presence of pyridine, and proliposomes were prepared by a film dispersion-freeze drying method. Morphological characterization of proliposomes was observed using a transmission electron microscope. Particle size and encapsulation efficiency of proliposomes were measured. The in vitro release of dehydrosilymarin from suspension and proliposomes was evaluated. The oral bioavailability of dehydrosilymarin suspension and proliposomes was investigated in rabbits.Results:The proliposomes prepared under the optimum conditions were spherical and smooth with a mean particle size in the range of 7 to 50 nm. Encapsulation efficiency was 81.59%±0.24%. The in vitro accumulative release percent of dehydrosilymarinloaded proliposomes was stable, which was slow in pH 1.2, and increased continuously in pH 6.8, and finally reached 86.41% at 12 h. After oral administration in rabbits, the relative bioavailability of proliposomes versus suspension in rabbits was 228.85%.Conclusion:Proliposomes may be a useful vehicle for oral delivery of dehydrosilymarin, a drug poorly soluble in water.

In vitro release and in vitro–in vivo correlation for silybin meglumine incorporated into hollow-type mesoporous silica nanoparticles

Background The purpose of this study was to develop a sustained drug-release model for water-soluble drugs using silica nanoparticles. Methods Hollow-type mesoporous silica nanoparticles (HMSNs) were prepared using Na2CO3 solution as the dissolution medium for the first time. The water-soluble compound, silybin meglumine, was used as the model drug. The Wagner–Nelson method was used to calculate the in vivo absorption fraction. Results The results of transmission electron microscopy and nitrogen adsorption revealed that the empty HMSNs had uniformly distributed particles of size 50–100 nm, a spherical appearance, a large specific surface area (385.89 ± 1.12 m2/g), and ultralow mean pore size (2.74 nm). The highly porous structure allowed a large drug-loading rate (58.91% ± 0.39%). In 0.08 M Na2CO3 solution, silybin meglumine-loaded HMSNs could achieve highly efficacious and long-term sustained release for 72 hours in vitro. The results of in vitro–in vivo correlation revealed that HMSNs in 0.08 M Na2CO3 solution had a correlation coefficient R2 value of 0.9931, while those of artificial gastric juice and artificial intestinal juice were only 0.9287 and 0.7689, respectively. Conclusion The findings of in vitro–in vivo correlation indicate that HMSNs together with Na2CO3 solution could achieve an excellent linear relationship between in vitro dissolution and in vivo absorption for 72 hours, leading to a promising model for sustained release of water-soluble drugs.

Preparation and in vitro evaluation of povidone-sodium cholate-phospholipid mixed micelles for the solubilization of poorly soluble drugs

Mixed micelles made of polyvinylpyrrolidone (PVP), sodium cholate, and phospholipids were prepared to improve the solubility of poorly water-soluble drugs. Sylibin, a drug used in treating liver diseases, was incorporated into the mixed micelles. The formulation of sylibin containing PVP-sodium cholate-phospholipid mixed micelles with an optimized composition (PVP/sodium cholate/phospholipid/silybin = 3:3:4:1∼2 by weight) was obtained based on the study of pseudoternary phase diagrams. The critical micelle concentration was used to evaluate the micellar stability towards dilution. The results showed that addition of PVP to sodium-cholate-phospholipid mixed micelles increased stability. The solubility of sylibin in PVP-sodium cholate-phospholipid mixed micelles was higher than that in pure water or in sodium cholate-phospholipid mixed micelles. In a stability study, we found that PVP-sodium cholate-phospholipid mixed micelles showed good stability. After 3 months storage at 40°C, just 2.6% sylibin was lost with only minor changes of the particle size when compared to a reference formulation containing sodium cholate and phospholipid mixed micelles. In addition, the developed formulation significantly improved in vitro drug release. The time required to release 50% sylibin (t50%) from sodium cholate and phospholipid mixed micelles was 326 h, while the t50% from PVP-sodium cholate-phospholipid mixed micelles was only 51.1 h. Our results suggest that these mixed micelles might have significant potential application to the biomedical field.

Enhanced oral bioavailability and tissue distribution of a new potential anticancer agent, Flammulina velutipes sterols, through liposomal encapsulation.

This study innovatively investigated the anticancer effect of Flammulina velutipes sterols (FVSs), the in vivo pharmacokinetics, and the tissue distribution of FVS-loaded liposomes. The FVS consisting of mainly 54.8% ergosterol and 27.9% 22,23-dihydroergosterol exhibited evident in vitro antiproliferative activity (liver HepG-2, IC50 = 9.3 μg mL(-1); lung A549, IC50 = 20.4 μg mL(-1)). To improve the poor solubility of FVS, F. velutipes sterol liposome (FVSL) was originally prepared. The encapsulation efficiency of ergosterol was 71.3 ± 0.1% in FVSL, and the encapsulation efficiency of 22,23-dihydroergosterol was 69.0 ± 0.02% in FVSL. In comparison to its two free sterol counterparts, the relative bioavailability of ergosterol and 22,23-dihydroergosterol in FVSL was 162.9 and 244.2%, respectively. After oral administration in Kunming mice, the results of tissue distribution demonstrated that the liposomal FVS was distributed mostly in liver and spleen. The drug was eliminated rapidly within 4 h. These findings support the fact that FVS, a potential nutraceutical and an effective drug for the treatment of liver cancer, could be encapsulated in liposomes for improved solubility and bioavailability.

Enhanced oral bioavailability of a sterol-loaded microemulsion formulation of Flammulina velutipes, a potential antitumor drug

Purpose To investigate the growth inhibition activity of Flammulina velutipes sterol (FVS) against certain human cancer cell lines (gastric SGC and colon LoVo) and to evaluate the optimum microemulsion prescription, as well as the pharmacokinetics of encapsulated FVS. Methods Molecules present in the FVS isolate were identified by gas chromatography/mass spectrometry analysis. The cell viability of FVS was assessed with methyl thiazolyl tetrazolium (MTT) bioassay. Based on the solubility study, phase diagram and stability tests, the optimum prescription of F. velutipes sterol microemulsions (FVSMs) were determined, followed by FVSMs characterization, and its in vivo pharmacokinetic study in rats. Results The chemical composition of FVS was mainly ergosterol (54.8%) and 22,23-dihydroergosterol (27.9%). After 72 hours of treatment, both the FVS (half-maximal inhibitory concentration [IC50] = 11.99 μg · mL−1) and the standard anticancer drug, 5-fluorouracil (IC50 = 0.88 μg · mL−1) exhibited strong in vitro antiproliferative activity against SGC cells, with IC50 > 30.0 μg · mL−1; but the FVS performed poorly against LoVo cells (IC50 > 40.0 μg · mL−1). The optimal FVSMs prescription consisted of 3.0% medium chain triglycerides, 5.0% ethanol, 21.0% Cremophor EL and 71.0% water (w/w) with associated solubility of FVS being 0.680 mg · mL−1 as compared to free FVS (0.67 μg · mL−1). The relative oral bioavailability (area-under-the-curve values of ergosterol and 22,23-dihydroergosterol showed a 2.56-fold and 4.50-fold increase, respectively) of FVSMs (mean diameter ~ 22.9 nm) as against free FVS were greatly enhanced. Conclusion These results indicate that the FVS could be a potential candidate for the development of an anticancer drug and it is readily bioavailable via microemulsion formulations.

In vitro and in vivo evaluation of capsaicin‐loaded microemulsion for enhanced oral bioavailability

BACKGROUND Capsaicin, as a food additive, has attracted worldwide concern owing to its pungency and multiple pharmacological effects. However, poor water solubility and low bioavailability have limited its application. This study aims to develop a capsaicin-loaded microemulsion to enhance the oral bioavailability of the anti-neuropathic-pain component, capsaicin, which is poorly water soluble. RESULTS In this study, the microemulsion consisting of Cremophor EL, ethanol, medium-chain triglycerides (oil phase) and water (external phase) was prepared and characterized (particle size, morphology, stability and encapsulation efficiency). The gastric mucosa irritation test of formulated capsaicin was performed in rats to evaluate its oral feasibility, followed by the pharmacokinetic study in vivo. Under these conditions, the encapsulated capsaicin revealed a faster capsaicin release in vitro coupled with a greater absorption in vivo when compared to the free capsaicin. The oral bioavailability of the formulated capsaicin-loaded microemulsions was 2.64-fold faster than that of free capsaicin. No significant irritation was observed on the mucosa from the pathological section of capsaicin-loaded microemulsion treated stomach. CONCLUSION These results indicate that the developed microemulsion represents a safe and orally effective carrier for poorly soluble substances. The formulation could be used for clinical trials and expand the application of capsaicin.

Tumor targeted delivery of octreotide-periplogenin conjugate: Synthesis, in vitro and in vivo evaluation

Periplogenin (PPG), a cardiac glycoside prepared from Cortex periplocae, with similar structure to bufalin, has been found to induce apoptosis in many tumor cells. However, lots of cardiac glycosides possessing strong antitumor activity in vitro have still not passed phase I clinical trials, mostly due to poor tumor selectivity and systemic toxicity. To overcome this drawback, we designed octreotide-periplogenin (OCT-PPG) conjugate by coupling PPG-succinate to the amino-terminal end of octreotide. In comparison with free PPG, the conjugate exhibited significantly stronger cytotoxicity on HepG2 cells (SSTRs overexpression) but much less toxicity in L-02 cells. After intravenous injection of OCT-PPG conjugate into H22 tumor-bearing mice, its total accumulation in tumor was 2.3 fold higher than that of free PPG, but was 0.71- and 0.84-fold lower in heart and liver, respectively, suggesting somatostatin-mediated target delivery of PPG into the tumor tissue and reduced distribution in heart and liver. In vivo studies using H22 tumor model in mice confirmed the remarkable therapeutic effect of this conjugate. These results suggested that OCT-PPG conjugate could provide a new approach for clinical application of cardiac glycosides and as a targeting agent for cancer therapy.

Cytotoxic effect of novel Flammulina velutipes sterols and its oral bioavailability via mixed micellar nanoformulation.

The aim of this study was to investigate the anti-tumor effect of sterols initially separated from Flammulina velutipes and the pharmacokinetics and tissue distribution after oral administration of F. velutipes sterol nanomicelles (FVSNs). F. velutipes sterol (FVS) consisted of mainly ergosterol (54.78%), 22,23-dihydroergosterol (27.94%) and ergost-8(14)-ene-3β-ol (discovered for the first time in F. velutipes). In vitro cytotoxicity assay of FVS against U251 cells and HeLa cells showed that at 72h treatment, the FVS (IC50=23.42μg/mL) exhibited strong inhibitory effect against U251 cells, even overwhelmed the standard anti-tumor drug (5-fluorouracil) to an extent, while the HeLa cells were not significantly susceptible to the FVS. To improve the solubility and bioavailability of FVS, a model for insoluble anti-tumor drugs, FVSNs were prepared. In vitro characterization of FVSNs revealed satisfactory size distribution, loading capacity and encapsulation efficiency. Pharmacokinetic study in SD rats demonstrated that the mixed micellar nanoformulation significantly enhanced the bioavailability of FVS than free drug. Additionly, tissue distribution in mice manifested that the biodistribution of FVSNs as compared to the free FVS suspension were significantly improved. In conclusion, the nanomicelles developed in our study provided a promising delivery system for enhancing the oral bioavailability and selective biodistribution of FVS, a potential anti-tumor agent.

Ergosterol-loaded poly(lactide-co-glycolide) nanoparticles with enhanced in vitro antitumor activity and oral bioavailability.

Aim:Ergosterol is a plant sterol with anti-tumor and anti-angiogenic activities, but is poorly soluble. In this study, we attempted to enhance its anti-tumor action and oral bioavailability via poly(lactide-co-glycolide) (PLGA) nanoparticle encapsulation.Methods:Ergosterol-loaded PLGA nanoparticles (NPs/Erg) were prepared using the emulsion/solvent evaporation technique. Their physicochemical properties were characterized, and their cytotoxicity against human cancer cell lines was evaluated with MTT assay. The pharmacokinetics and tissue distribution of NPs/Erg were investigated in rats and mice, respectively.Results:NPs/Erg were spherical in shape with a particle size of 156.9±4.8 nm and a Zeta potential of -19.27±1.13 mV, and had acceptable encapsulation efficiency and loading capacity. NPs/Erg exerted much stronger cytotoxicity against human cancer cells than the free ergosterol, and showed significantly reduced IC50 values (14.69±0.48 μg/mL in glioma U251 cells; 9.43±0.52 μg/mL in breast cancer MCF-7 cells; 4.70±0.41 μg/mL in hepatoma HepG2 cells). After oral administration of a single dose in rats, NPs/Erg displayed a prolonged plasma circulation with a 4.9-fold increase of oral bioavailability compared with the free ergosterol. After mice received NPs/Erg, the ergosterol in NPs/Erg was rapidly distributed in stomach, kidneys, liver, brain, spleen, and virtually non-existent in heart and lungs. The presence of NPs/Erg in brain was particularly improved compared with the free ergosterol.Conclusion:The PLGA nanoparticles serve as a promising carrier for the poorly soluble ergosterol and significantly improve its bioavailability, biodistribution and in vitro anti-tumor activities.