Galactose-decorated pH-responsive nanogels for hepatoma-targeted delivery of oridonin.

Nanogels based on the polymers of galactosylated chitosan-graft-poly (N-isopropylacrylamide) (Gal-CS-g-PNIPAm) were used as carriers of oridonin (ORI) for tumor targeting. Three ORI-loaded nanogels with various degrees of galactose substitution were prepared, and their characteristics were evaluated. The release behavior of ORI from these nanogels was pH-dependent, and the release could be accelerated under mildly acidic conditions. The cytotoxicity of ORI-loaded nanogels was pH-sensitive. ORI-loaded nanogels exhibited a higher antitumor activity than drug-loaded nanogels without galactosylation, and the anticancer activity increased in relation to increases in the number of galactose moieties of the nanogels in HepG2 cells. In contrast, the cytotoxicity of ORI-loaded nanogels against MCF-7 cells decreased compared with that of drug-loaded nanogels without galactosylation. Results demonstrated that these nanogels could enhance the uptake of ORI into HepG2 cells via asialoglycoprotein receptor-mediated endocytosis. These galactose-decorated pH-responsive nanogels were well-suited for targeted drug delivery to liver cancer cells.

A targeted and redox/pH-responsive chitosan oligosaccharide derivatives based nanohybrids for overcoming multidrug resistance of breast cancer cells.

A novel folic acid mediated chitosan oligosaccharide-grafted disulfide-containing polyethylenimine copolymer-based silica nanohybrids were fabricated for co-delivering paclitaxel and P-shRNA. These nanoparticles could efficiently protect P-shRNA against degradation, and exhibited well redox-responsive P-shRNA release and pH-responsive drug release behaviors. Folic acid as the targeting head, could improve cellular uptake of nanoparticles by multidrug-resistant breast cancer cells. Moreover, these nanoparticles showed excellent delivery P-shRNA into cells and displayed high gene silencing efficiency at the targeted mRNAs to downregulate the expression of P-gp which induced up to 63% decrease. Finally, nanoparticles could completely reverse the resistance of breast cancer cells to paclitaxel and the resistance reversion index was 50.59. These results suggested that our nanoparticles could efficiently co-deliver paclitaxel and P-shRNA into cancer cells to exert its synergistic antitumor effect, and opened up a new avenue for overcoming multidrug resistance.

Studies on pharmacokinetics and tissue distribution of oridonin nanosuspensions.

The purpose of the present study was to investigate the effects of particle size on the pharmacokinetics and tissue distribution of oridonin nanosuspensions after intravenous administration. Two oridonin nanosuspensions with markedly different size were prepared by high pressure homogenization method. The particle size of nanosuspension A is 103.3+/-1.5nm, while B is 897.2+/-14.2nm. Dissolution studies showed that complete dissolution could be obtained within 10min for nanosuspension A, however, nanosuspension B showed a slower dissolution, only 85.2% dissolved by 2h. The pharmacokinetics and tissue distribution of oridonin nanosuspensions A and B were studied after intravenous administration using New Zealand rabbits and Kunming mice as experimental animals, respectively. An Oridonin control solution was studied parallelly. The results showed that oridonin nanosuspension A exhibited pharmacokinetic and biodistribution properties similar to solution due to its rapid dissolution in blood circulation. Oridonin nanosuspension B, however, showed a high uptake in RES organs, meanwhile exhibited a markedly different pharmacokinetic property compared to nanosuspension A. These differences could be attributed to the different particle size of the two nanosuspensions considering their zeta potential had no significant difference. In conclusion, particle size showed obvious effects on pharmacokinetics and tissue distribution of nanosuspensions.

Synthesis, characterization, in vitro and in vivo evaluation of PEGylated oridonin conjugates.

Oridonin (ORI), a diterpenoid compound with promising antitumor activity, was proved to possess potent antileukemia efficacies in vitro and in vivo recently. However, the development and application of ORI was limited by its poor solubility and rapid plasma clearance. The purpose of this study was to solve these problems. PEGylated oridonin linked with succinic acid (SA) as spacer moiety (PEG-SA-ORI conjugate) was synthesized. mPEG amines with four specifications of molecular weight (MW) were utilized. All polymeric conjugates showed satisfactory aqueous solubility and in vitro studies implied that the drug solubility and release features of conjugates were relevant to PEGs. The drug solubility increased more when the MW of PEG was lower, while more significant sustained-release effect was shown with higher PEG MW. Moreover, the release behaviors of conjugates showed a pH-sensitive property. In vivo pharmacokinetic studies demonstrated that the elimination half-life was prolonged in comparison with ORI solution. PEGylation could be a promising method to obtain better efficacy in the field of drug delivery system.

Self-assembled nanoparticles based on galactosylated O-carboxymethyl chitosan-graft-stearic acid conjugates for delivery of doxorubicin.

A novel polymer, i.e. galactosylated O-carboxymethyl chitosan-graft-stearic acid (Gal-OCMC-g-SA) was synthesized for liver targeting delivery of doxorubicin. The chemical structure was characterized by FT-IR, (1)H NMR and elemental analysis. Gal-OCMC-g-SA could self-assemble into nanoparticles with diameter of 160 nm by probe sonication in aqueous medium and exhibited a low critical aggregation concentration of 0.047 mg/mL. The DOX-loaded Gal-OCMC-g-SA (Gal-OCMC-g-SA/DOX) self-assembled nanoparticles were almost spherical in shape with an average diameter of less than 200 nm and zeta potential of around -10 mV. In vitro release revealed that the Gal-OCMC-g-SA/DOX nanoparticles exhibited a sustained and pH-dependent drug release manner. Furthermore, the hemolysis test demonstrated the good safety of Gal-OCMC-g-SA in blood-contacting applications. These results indicated that Gal-OCMC-g-SA/DOX nanoparticles were highly potential to be applied in cancer therapy.

In vitro and in vivo evaluation of oridonin-loaded long circulating nanostructured lipid carriers.

The purpose of this study was to develop poly(ethylene glycol)-coated nanostructured lipid carriers (PEG-NLC) for parenteral delivery of oridonin (ORI) to prolong drug circulation time in blood. Oridonin-loaded PEG-NLC (ORI-PEG-NLC) consisting of PEG(2000)-stearate, glycerol monostearate and medium chain triglycerides were prepared by emulsion-evaporation and low temperature-solidification technique. Oridonin-loaded NLC (ORI-NLC) were also prepared as control. ORI-PEG-NLC were observed by transmission election microscope and the morphology was in rotiform shape. The mean particle size of ORI-PEG-NLC was 329.2 nm and entrapment efficacy was 71.18%. The results of differential scanning calorimetry and X-ray diffraction revealed a low-crystalline structure of ORI and verified the incorporation of ORI into the nanoparticles. In vitro drug release of ORI-PEG-NLC exhibited biphasic drug release patterns with burst release initially and prolonged release afterwards. Pharmacokinetic analysis showed that the mean residence time of ORI-PEG-NLC was prolonged and AUC (area under tissue concentration-time curve) value was also improved compared with ORI-NLC and ORI solution. In conclusion, ORI-PEG-NLC could be a potential carrier to get prolonged retention time of oridonin in blood.

Comparison of different methods for preparation of a stable riccardin D formulation via nano-technology.

Riccardin D is a new compound extracted from liverwort Marchantia polymorpha L. It has been proved to be useful in antifungal therapy and reversing the resistance of Candida albicans against fluconazole. However, the poor solubility leads to the poor bioavailability and limits its development. In this study, nanocrystals were prepared in the evaporative precipitation into aqueous solution (EPAS) and the microfluidisation process. The characterizations of nanocrystals were compared by transmission electron microscope, size distribution, and zeta potential. In the EPAS method, the drug was dissolved in the organic phase and F68, HPMC, PVP K30 were dissolved in water with the mass ratio of 2:1:2:1. In the microfluidisation process, two key factors - pressure and number of cycles were screened and 8 cycles at 2000 bar was the most efficient parameter. The nanocrystals made in EPAS process were smaller, more uniform and had a narrower distribution than the microfluidisation nanocrystals. Differential scanning calorimetry (DSC) and X-ray diffraction confirmed the crystalline states that were both reserved. The solubility was greatly improved by the two methods and the EPAS nanocrystals were more soluble due to the smaller size. An enhanced dissolution was obvious in vitro. And the stable nanocrystals were successfully achieved by the two methods.

Synergistic effect of folate-mediated targeting and verapamil-mediated P-gp inhibition with paclitaxel -polymer micelles to overcome multi-drug resistance.

Multidrug resistance (MDR) in tumor cells is a significant obstacle for successful cancer chemotherapy. Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) is a key factor contributing to the development of tumor drug resistance. Verapamil (VRP), a P-gp inhibitor, has been reported to be able to reverse completely the resistance caused by P-gp. For optimal synergy, the drug and inhibitor combination may need to be temporally colocalized in the tumor cells. Herein, we investigated the effectiveness of simultaneous and targeted delivery of anticancer drug, paclitaxel (PTX), along with VRP, using DOMC-FA micelles to overcome tumor drug resistance. The floate-functionalized dual agent loaded micelles resulted in the similar cytotoxicity to PTX-loaded micelles/free VRP combination and co-administration of two single-agent loaded micelles, which was higher than that of PTX-loaded micelles. Enhanced therapeutic efficacy of dual agent micelles could be ascribe to increased accumulation of PTX in drug-resistant tumor cells. We suggest that the synergistic effect of folate receptor-mediated internalization and VRP-mediated overcoming MDR could be beneficial in treatment of MDR solid tumors by targeting delivery of micellar PTX into tumor cells. As a result, the difunctional micelle systems is a very promising approach to overcome tumor drug resistance.

Chitosan-g-poly(N-isopropylacrylamide) based nanogels for tumor extracellular targeting.

The principle objective of this research was to develop and characterize pH-responsive and biocompatible nanogels as a tumor-targeting drug delivery system. The nanogels were self-assembled from chitosan-based copolymers, chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAm). The copolymers were synthesized via free radical copolymerization and characterized for their chemical structure by FT-IR and (1)H NMR. These copolymers could be efficiently loaded with oridonin (ORI) and the characteristics of ORI-loaded nanogels were evaluated. Drug release researches indicated that the ORI-loaded nanogels displayed pH-dependent release behaviors. Based on MTT assay and cellular morphological analysis, the anti-tumor activity of ORI-loaded nanogels was higher at pH 6.5 than at pH 7.4. In conclusion, the obtained nanogels appeared to be of great promise in tumor extracellular pH targeting for ORI.