Zhonggui He

Dual targeting folate-conjugated hyaluronic acid polymeric micelles for paclitaxel delivery

A series of novel self-assembled hyaluronic acid derivatives (HA-C(18)) grafted with hydrophobic octadecyl moiety and further dual targeting folic acid-conjugated HA-C(18) (FA-HA-C(18)) were synthesized. With the increase in the degree of substitution of octadecyl group from 12.7% to 19.3%, the critical micellar concentration of HA-C(18) copolymers decreased from 37.3 to 10.0 μg/mL. Paclitaxel (PTX) was successfully encapsulated into the hydrophobic cores of the HA-C(18) and FA-HA-C(18) micelles, with encapsulation efficiency as high as 97.3%. The physicochemical properties of the polymeric micelles were measured by DLS, TEM and DSC. Moreover, in vitro release behavior of PTX was investigated by dialysis bag method and PTX was released from micelles in a near zero-order sustained manner. In vitro antitumor activity tests suggested PTX-loaded HA-C(18) and FA-HA-C(18) micelles exhibited significantly higher cytotoxic activity against MCF-7 and A549 cells compared to Taxol at a lower PTX concentration. The cellular uptake experiments were conducted by quantitative assay of PTX cellular accumulation and confocal laser scanning microscopy imaging of coumarin-6 labeled HA-C(18) and FA-HA-C(18) micelles in folate receptor overexpressing MCF-7 cells. Folate and CD44 receptor competitive inhibition studies performed by fluorescence microscopy imaging suggested intracellular delivery of HA-C(18) and FA-HA-C(18) micelles were efficiently taken up via CD44 receptor-mediated endocytosis. The folate receptor-mediated endocytosis further enhanced internalized amounts of FA-HA-C(18) micelles in MCF-7 cells, as compared with HA-C(18) micelles. The internalization pathways of PTX-loaded HA-C(18) and FA-HA-C(18) micelles might include clathrin-mediated endocytosis, caveolae-mediated endocytosis and macropinocytosis. Therefore, the present study suggested that HA-C(18) and FA-HA-C(18) copolymers as biodegradable, biocompatible and cell-specific targetable nanostructure carriers, are promising nanosystems for cellular and intracellular targeting delivery of hydrophobic anticancer drugs.

Solid self-emulsifying nitrendipine pellets: Preparation and in vitro/in vivo evaluation

Objective of this study is to develop and evaluate the new solid self-emulsifying (SE) pellets of poorly soluble nitrendipine (NTD). These pellets were prepared via extrusion/spheronization technique, using liquid SEDDS (NTD, Miglyol 812, Cremophor RH 40, Tween 80, and Transcutol P), adsorbents (silicon dioxide and crospovidone), microcrystalline cellulose and lactose. The resulting SE pellets with 30% liquid SEDDS exhibited uniform size (800-1000 microm) and round shape, droplet size distribution following self-emulsification was nearly same to the liquid SEDDS (72+/-16 nm and 64+/-12 nm). The in vitro release was similar for the two SE formulations (over 80% within 30 min), both significantly higher than the conventional tablets (only 35% within 30 min). The oral bioavailability was evaluated for the SE pellets, liquid SEDDS and conventional tablets in fasted beagle dogs. AUC of NTD from the SE pellets showed 1.6-fold greater than the conventional tablets and no significant difference compared with the liquid SEDDS. In conclusion, our studies illustrated that extrusion/spheronization technique could be a useful large-scale producing method to prepare the solid SE pellets from liquid SEDDS, which can improve oral absorption of NTD, nearly equivalent to the liquid SEDDS, but better in the formulation stability, drugs leakage and precipitation, etc.

Prodrug-based nanoparticulate drug delivery strategies for cancer therapy

Despite the rapid developments in nanotechnology and biomaterials, the efficient delivery of chemotherapeutic agents is still challenging. Prodrug-based nanoassemblies have many advantages as a potent platform for anticancer drug delivery, such as improved drug availability, high drug loading efficiency, resistance to recrystallization upon encapsulation, and spatially and temporally controllable drug release. In this review, we discuss prodrug-based nanocarriers for cancer therapy, including nanosystems based on polymer-drug conjugates, self-assembling small molecular weight prodrugs and prodrug-encapsulated nanoparticles (NPs). In addition, we discuss new trends in the field of prodrug-based nanoassemblies that enhance the delivery efficiency of anticancer drugs, with special emphasis on smart stimuli-triggered drug release, hybrid nanoassemblies, and combination drug therapy.

Preparation and characterization of a submicron lipid emulsion of docetaxel: submicron lipid emulsion of docetaxel.

Docetaxel, a widely used anticancer agent, has sparingly low aqueous solubility, thus Tween 80 and ethanol need to be added into its formulation, probably resulting in the toxic effects. In this study, we aimed to utilize submicron lipid emulsions as a carrier of docetaxel to avoid these potential toxic vehicles. Preformulation study was performed for rational emulsions formulation design, including drug solubility, distribution between oil and water, and degradation kinetics. Supersaturated submicron lipid emulsion of docetaxel was prepared by temperature elevation method. Soya oil and Miglyol 812 can incorporate docetaxel up to 1.0% (drug to lipid ratio) and were used as the oil phase of emulsions. The optimal formulation of docetaxel is composed of 10% oil phase, 1.2% soybean lecithin, 0.3% Pluoronic F68, and 0.4 or 0.8 mg/mL docetaxel, with particle size in the nanometer range, entrapment efficiency more than 90%, and is physicochemically stable at 4 and 25°C for 6 months. Animal studies showed that docetaxel emulsion has significantly higher area under the curve (AUC) and Cmax in rats compared to its micellar solution. The results suggested that the submicron lipid emulsion is a promising intravenous carrier for docetaxel in place of its present commercially available docetaxel micellar solution with potential toxic effects.

Development of novel self-assembled DS-PLGA hybrid nanoparticles for improving oral bioavailability of vincristine sulfate by P-gp inhibition

To improve the encapsulation efficiency and oral bioavailability of vincristine sulfate (VCR), novel self-assembled dextran sulphate-PLGA hybrid nanoparticles (DPNs) were successfully developed using self-assembly and nanoprecipitation method. By introducing the negative polymer of dextran sulphate sodium (DS), VCR was highly encapsulated (encapsulation efficiency up to 93.6%) into DPNs by forming electrostatic complex. In vitro release of VCR solution (VCR-Sol) and VCR-loaded DPNs (VCR-DPNs) in pH 7.4 PBS showed that about 80.4% of VCR released from VCR-DPNs after 96h and burst release was effectively reduced, indicating pronounced sustained-release characteristics. In vivo pharmacokinetics in rats after oral administration of VCR-Sol and VCR-DPNs indicated that the apparent bioavailability of VCR-DPNs was increased to approximate 3.3-fold compared to that of VCR-Sol. The cellular uptake experiments were conducted by quantitative assay of VCR cellular accumulation and fluorescence microscopy imaging of fluorescent labeled DPNs in two human breast cancer cells including MCF-7 and P-glycoprotein over-expressing MCF-7/Adr cells. The relative cellular uptake of VCR-DPNs was 12.4-fold higher than that of VCR-Sol in MCF-7/Adr cells implying that P-glycoprotein-mediated drug efflux was diminished by the introduction of DPNs. The new DPNs might provide an effective strategy for oral delivery of VCR with improved encapsulation efficiency and oral bioavailability.

Nanoparticle albumin-bound (NAB) technology is a promising method for anti-cancer drug delivery.

Albumin is a versatile drug carrier in anti-cancer drug delivery system and it also has an actively targeting capacity to tumors. Recently, nanoparticle albumin-bound (nab) paclitaxel (nab-paclitaxel; Abraxane) has been approved in 2006 for use in patients with metastatic breast cancer who have failed in the combination chemotherapy, and so the nab-technology has attracted much interest in the anti-cancer drug delivery system. The details about the preparation, characterization and evaluation of nab-paclitaxel (ABI-007) are discussed. The pharmacokinetics, pharmacodynamics and the clinical trials of ABI-007 are also reviewed. Furthermore, the recent applications of nab-technology in the anti-cancer drug delivery systems are summarized by virtue of the patents pertaining to nab-technology. To sum up, nab-technology has a great potential of being applied extensively in the field of anti-cancer agents delivery in the future in order to acquire the good safety and better therapeutical effect.

Development of a chemically stable 10-hydroxycamptothecin nanosuspensions

The purpose of this study was to prepare and characterize nanosuspensions loading the active lactone form of 10-hydroxycamptothecin (10-HCPT). Nanosuspensions were prepared in terms of microprecipitation-high-pressure homogenization method. As for the preparation processes, three important parameters, i.e. the agitation rate of stabilizer solution, homogenization pressure and cycle numbers, were investigated and optimized, and the optimal values were 1000 rpm, 1000 bar and 20 times, respectively. The particle size and zeta potential of the 10-HCPT-nanosuspensions were 131 nm and -25.5 mV. The particle morphology was determined by transmission electron microscopy and the 10-HCPT nanoparticles were baculine or trabecular in shape. The solid state of 10-HCPT in nanoparticles was analyzed using X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The XRD and the DSC results both indicated that 10-HCPT was present as an amorphous state in the lyophilized powders for nanosuspension. The chemical stability tests demonstrated that near 90% lactone form of 10-HCPT was present in the nanosuspensions but it was easily transferred to the carboxylate form in the solution at pH 7.0-8.0. In vitro dissolution tests showed the dissolution rate of nanosuspensions, compared with the coarse suspensions, had been significantly increased.

Disulfide Bond Bridge Insertion Turns Hydrophobic Anticancer Prodrugs into Self-Assembled Nanomedicines

It is commonly observed that hydrophobic molecules alone cannot self-assemble into stable nanoparticles, requiring amphiphilic or ionic materials to support nanoparticle stability and function in vivo. We report herein newly self-assembled nanomedicines through entirely different mechanisms. We present proof-of-concept methodology and results in support of our hypothesis that disulfide-induced nanomedicines (DSINMs) are promoted and stabilized by the insertion of a single disulfide bond into hydrophobic molecules, in order to balance the competition between intermolecular forces involved in the self-assembly of nanomedicines. This hypothesis has been explored through diverse synthetic compounds, which include four first-line chemotherapy drugs (paclitaxel, doxorubicin, fluorouracil, and gemcitabine), two small-molecule natural products and their derivatives, as well as a fluorescent probe. Such an unprecedented and highly reproducible system has the potential to serve as a synthetic platform for a wide array of safe and effective therapeutic and diagnostic nanomedicine strategies.

Stealth CD44-targeted hyaluronic acid supramolecular nanoassemblies for doxorubicin delivery: probing the effect of uncovalent pegylation degree on cellular uptake and blood long circulation.

Stealth active targeting nanoparticles (NPs) usually include two types of ligand sites: ligand anchored on distal ends of the polyethylene glycol (PEG) and ligand buried under pegylated layer. The latter typical case is hyaluronic acid (HA)-based NPs; however, there is little information available for the latter NPs about effect of the optimal density of surface PEG coating on the blood circulation time, cellular uptake and in vivo anticancer activity. Thus, in this study, in order to optimize the anticancer effects of HA-based NPs, we focus on how uncovalent pegylation degree modulates blood circulation time and cellular uptake of HA-based NPs. We firstly designed a new double-hydrophilic copolymer by conjugating HP-β-cyclodextrin with HA, and this carrier was further pegylated with adamantyl-peg (ADA-PEG) to form inclusion complex HA-HPCD/ADA-PEG, termed as HCPs. The supramolecular nanoassemblies were fabricated by host-guest and polar interactions between HCPs and doxorubicin (Dox), with vitamin E succinate (VES) being a nanobridge. Despite the active recognition between HA and CD44 receptor, the cellular uptake and targeting efficiency of HA-NPs decreased with the increasing peg density, demonstrating HA was partly buried by high density peg coating. However, the high density of peg coating was beneficial to long circulation time, tumor biodistribution and anticancer activity in vivo. NPs with 5% peg coating had the optimal cellular targeting efficiency in vitro and anticancer effects in vivo. The findings suggest that balancing long circulation property and cellular uptake is important to achieve the optimal antitumor efficacy for pegylated HA-based NPs, and that PEG coating densities cannot be extended beyond a certain density for shielding effect without compromising the efficacy of hyaluronic acid targeted delivery.

Simultaneous determination of tetrahydropalmatine, protopine, and palmatine in rat plasma by LC-ESI-MS and its application to a pharmacokinetic study

A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method has been developed and validated for the simultaneous quantification of tetrahydropalmatine, protopine and palmatine in rat plasma using phenacetin as the internal standard (IS). Two hundred microliters plasma samples were extracted by dichloromethane under a strong basic condition. The analytes were separated by a C18 column and detected with a single quadrupole mass spectrometer. The used mobile phase was acetonitrile-water (40:60, v/v) containing 5mM ammonium acetate and 0.2% glacial acetic acid. Detection was carried out by positive electrospray ionization in selected ion reaction (SIR) mode at m/z 356.6 for tetrahydropalmatine, 354.6 for protopine, 352.6 for palmatine and 180.4 for the IS, respectively. The method was validated over the concentration range of 1.00-500ngmL(-1) and the lower limit of quantification (LLOQ) was 1.00ngmL(-1) for all three analytes. The intra- and inter-day precision values were less than 9% relative standard deviation (R.S.D.), and the relative error ranged from -7.4 to 4.8%. The extraction recoveries were on average 91.42% for tetrahydropalmatine, 84.75% for protopine, 57.26% for palmatine, and 83.18% for IS. The validated method was successfully applied to a pharmacokinetic study of tetrahydropalmatine, protopine and palmatine in rats after oral administration of Rhizoma Corydalis Decumbentis extract.