Jiangling Wan

A new solid self-microemulsifying formulation prepared by spray-drying to improve the oral bioavailability of poorly water soluble drugs.

The objectives of the present work were, first, to develop a new solid self-microemulsifying drug delivery system (SMEDDS) for oral poorly water-soluble drugs such as nimodipine; and second, to evaluate its oral bioavailability in healthy rabbits. The liquid SMEDDS consisted of ethyl oleate, Labrasol, Cremophor RH 40 and nimodipine. The solid SMEDDS was prepared by spray-drying the liquid SMEDDS in a laboratory spray dryer, using dextran as solid carrier. The imaging of TEM and photo correlation spectroscopy revealed no difference in the droplet size of reconstituted microemulsion between both SMEDDS. Solid state characterization of the solid SMEDDS was performed by SEM, DSC, and X-ray powder diffraction. The same dose of nimodipine in the solid SMEDDS and in the liquid SMEDDS resulted in similar AUC and C(max) values, but the maximum absorption was retarded by the solid SMEDDS. AUC and C(max) after oral administration of the solid SMEDDS were 2.6- and 6.6-fold higher, respectively, compared with those of the conventional tablet. These results demonstrate that the solid SMEDDS may preserve an improved bioavailability with releasing microemulsion lipid droplets from the formulation in vivo. Thus, this solid self-microemulsifying system may provide a useful solid dosage form for oral poorly water-soluble drugs.

Iontophoresis-driven penetration of nanovesicles through microneedle-induced skin microchannels for enhancing transdermal delivery of insulin

The transdsermal delivery of insulin remains a significant challenge due to low permeation rates at therapeutically useful rates. We report unilamellar nanovesicles with membrane thickness of 3-5 nm and entrapment efficiency of 89.05+/-0.91%, which can be driven by iontophoresis for enhancing transdermal delivery of insulin through microneedle-induced skin microchannels. The permeation rates of insulin from positive nanovesicles driven by iontophoresis through skins with microneedle-induced microchannels were 713.3 times higher than that of its passive diffusion. The in vivo studies show that the blood glucose levels of diabetic rats induced by the positive nanovesicles driven by iontophoresis through skins with microneedle-induced microchannels are 33.3% and 28.3% of the initial levels at 4 and 6 h, which are comparable to those induced by subcutaneous injection of insulin. The fluorescence imaging validated the penetration of insulin from the nanovesicles driven by iontophoresis through skins with microchannels. The nanovesicles with charges show significant permeation ability with the assistance of physical devices including microneedles and iontophoresis. This approach offers a new strategy for non-invasive delivery of peptides with large molecular weights using nanovesicles.

Hydrogel-thickened nanoemulsion system for topical delivery of lipophilic drugs

In this work, a hydrogel-thickened nanoemulsion system (HTN) with powerful permeation ability, good stability and suitable viscosity was investigated for topical delivery of active molecules. HTN was prepared to deliver an oily mixture of 5% camphor, 5% menthol and 5% methyl salicylate for topical therapy of arthritis, minor joint and muscle pain using soybean oil as the oil phase, soybean lecithin, Tween 80 and poloxamer 407 as the surfactants, propylene glycol as the cosurfactant, carbomer 940 as a thickening agent. The HTN system was found to combine the o/w microstructure of nanoemulsion with the gel network of hydrogel and had a suitable viscosity of 133.2PaS. The system had small average diameters and good long-term stability. The abilities of HTN to deliver the high amounts of camphor, menthol and methyl salicylate were evaluated using the in vitro permeation studies. The permeation rates of camphor, menthol and methyl salicylate from the optimal HTN formulation were 138.0+/-6.5, 63.6+/-3.3, 53.8+/-3.2 microg cm(-2) h(-1) and showed the significant advantages over the control gel. The HTN with good stability and powerful permeation enhancing ability and suitable viscosity might be a promising prospective carrier for topical delivery of lipophilic drugs.

Micelles assembled with carbocyanine dyes for theranostic near-infrared fluorescent cancer imaging and photothermal therapy.

It is an emerging focus to explore a theranostic nanocarrier for simultaneous cancer imaging and therapy. Herein, we demonstrate a theranostic micelle system for cancer near infrared fluorescent (NIRF) imaging with enhanced signal to noise ratio and superior photothermal therapy. The copolymers consisting of monomethoxy poly(ethylene glycol) and alkylamine-grafted poly(L-aspartic acid) are assembled with carbocyanine dyes into theranostic micelles, which exhibit small size, high loading capacity, good stability, sustained release behavior, and enhanced cellular uptake. The micelles achieve the preferable biodistribution and long-term retention of carbocyanine dyes at tumor, which result in enhanced NIRF imaging by generating stable retention of NIRF signals at both hypervascular and hypovascular tumors during a long-term imaging period of up to 8 day, accompanying with negligible noise at normal tissues. The photostability of carbocyanine dye (Cypate) plays an important role for long-term cancer imaging with enhanced SNR. Moreover, the micelles exhibit severe photothermal damage on cancer cells via the destabilization of subcellular organelles upon photoirradiation, causing superior photothermal tumor regress. The micelles act as a powerful theranostic nanocarrier for simultaneous cancer imaging with high contrast and superior photothermal therapy.

The decrease of PAMAM dendrimer-induced cytotoxicity by PEGylation via attenuation of oxidative stress.

Due to their unique structure, poly(amidoamine) (PAMAM) dendrimers have been widely used in medical applications. However, PAMAM dendrimers bearing amino terminals show certain cytotoxicity. In order to improve their biocompatibility, we modified Generation-5 PAMAM dendrimers by conjugating them with poly(ethylene glycol) (PEG) of two different molecular weights and different number of chains. The IC(50) values of PEGylated dendrimers were 12-105 fold higher than those of PAMAM dendrimers. To investigate the influence of PEGylation on PAMAM-induced cytotoxicity, the intracellular responses, reactive oxygen species (ROS) content, mitochondrial membrane potential (MMP), and apoptosis were examined. The results indicated that conjugation with PEG could effectively reduce the PAMAM-induced cell apoptosis by attenuating the ROS production and inhibiting PAMAM-induced MMP collapse. Meanwhile, dendrimers conjugated with less PEG of lower molecular weight did not significantly change the endocytic properties. Dendrimers conjugated with more PEG of higher molecular weight were much less cytotoxic. This study provided a novel insight into the effects of PEGylation on the decrease of cytotoxicity at the molecular level.

Potent dried drug nanosuspensions for oral bioavailability enhancement of poorly soluble drugs with pH-dependent solubility.

The objective of this study was to enhance the oral bioavailability of itraconazole (ITZ) with dried drug nanosuspensions. The feasibility of using poloxamer 407 or HPMC (50 cp) as stabilizers for preparing ITZ nanosuspensions by facile acid-base neutralization was investigated. Dried ITZ nanosuspensions were prepared by spray drying. The effect of matrix former on the dissolution rate of dried ITZ nanosuspensions was investigated. Results from dissolution test revealed that spray-dried ITZ nanosuspensions (ITZ:HPMC:mannitol 1:0.5:2, w/w) preserved the high dissolution rate from nanosuspensions. After oral administration in rats, the AUC(0-36) from dried ITZ nanosuspensions was 1.5-fold and 1.8-fold higher than the AUC(0-36) from sporanox pellets (commercial product) in the fed and fasted states, respectively (p<0.05). More importantly, the AUC(0-36) from dried ITZ nanosuspensions showed no difference between fed/fasted states, because this formulation could enhance the adsorption of ITZ in target site (small intestine) regardless of food intake. In addition, dried ITZ nanosuspensions showed a lower inter-individual variability in terms of bioavailability. Positive results demonstrate that dried drug nanosuspensions formulation prepared by acid-base neutralization combined with spray drying may be a promising method for enhancing the oral bioavailability of poorly soluble drugs with pH-dependent solubility.

Cellular uptake and intracellular trafficking of PEG-b-PLA polymeric micelles.

Besides as an inert carrier for hydrophobic anticancer agents, polymeric micelles composed of di-block copolymer poly(ethylene glycol)-poly(lactic acid) (PEG-b-PLA) function as biological response modifiers including reversal of multidrug resistance in cancer. However, the uptake mechanisms and the subsequent intracellular trafficking remain to be elucidated. In this paper, we found that the uptake of PEG-b-PLA polymeric micelles incorporating nile red (M-NR) was significantly inhibited by both dynamin inhibitor dynasore and dynamin-2 dominant negative mutant (dynamin-2 K44A). Exogenously expressed caveolin-1 colocalized with M-NR and upregulated M-NR internalization in HepG2 cells expressing low level of endogenous caveolin-1, while caveolin-1 dominant negative mutant (caveolin-1 Y14F) significantly downregulated M-NR internalization in C6 cells expressing high level of endogenous caveolin-1. Exogenously expressed clathrin light chain A (clathrin LCa) did not mainly colocalize with the internalized M-NR and had no effect on M-NR uptake. These results suggested that dynamin- and caveolin-dependent but clathrin-independent endocytosis was involved in M-NR cellular uptake. We further found that M-NR colocalized with lysosome and microtubulin after internalization.

Preparation of Coenzyme Q10 nanostructured lipid carriers for epidermal targeting with high-pressure microfluidics technique.

Objective: The objective of this work was to prepare coenzyme Q10 loaded nanostructured lipid carriers (Q10-NLC) and evaluate its epidermal targeting effect. Methods: Q10-NLC was prepared by high-pressure microfluidics technique. Formulations and preparation parameters were optimized with response surface design. Q10-NLC was characterized by PCS, TEM, DSC and PXRD. The penetration of Q10 from the Q10-NLC formulations through skins and into skins were evaluated in vitro using Franz diffusion cells fitted with SD rat skins. In vitro release, long-term stability and light stability were also evaluated. Results: The results showed that the concentration of solid lipid and emulsifier in formulation had a significant influence on particle size. The optimized preparation parameters were magnetic stirring for 20 min, high stirring at 8000 rpm for 1 min and high-pressure microfluidics at 1200 bar for three cycles. The size of Q10-NLC prepared by optimized formulation and parameters was (151.7 ± 2.31) nm, polydispersity (PDI) 0.144, ζ potential was (−44.1 ± 1.68) mV, drug loading 2.51%, encapsulation efficiency 100%. In vitro release study, Q10-NLC showed fast release during the first 3 hours and prolonged release afterwards. In vitro skin permeation study, the accumulative uptake of Q10 in epidermal of Q10-NLC was 10.11 times over Q10 emulsion. After exposure to day light for 24 hours, the amount of Q10 in Q10-NLC decreased only 5.59%, while in Q10 emulsion decreased 24.61% and Q10-ethanol solution 49.74%. Conclusion: Q10-NLC exhibited a significant epidermal targeting effect, which was proved to be a promising carrier for topical delivery of Q10.

Controlled poorly soluble drug release from solid self-microemulsifying formulations with high viscosity hydroxypropylmethylcellulose

The objective of this work was the development of a controlled release system based on self-microemulsifying mixture aimed for oral delivery of poorly water-soluble drugs. HPMC-based particle formulations were prepared by spray drying containing a model drug (nimodipine) of low water solubility and hydroxypropylmethylcellulose (HPMC) of high viscosity. One type of formulations contained nimodipine mixed with HPMC and the other type of formulations contained HPMC and nimodipine dissolved in a self-microemulsifying system (SMES) consisting of ethyl oleate, Cremophor RH 40 and Labrasol. Based on investigation by transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray powder diffraction, differences were found in the particle structure between both types of formulations. In vitro release was performed and characterized by the power law. Nimodipine release from both types of formulations showed a controlled release profile and the two power law parameters, n and K, correlated to the viscosity of HPMC. The parameters were also influenced by the presence of SMES. For the controlled release solid SMES, oil droplets containing dissolved nimodipine diffused out of HPMC matrices following exposure to aqueous media. Thus, it is possible to control the in vitro release of poorly soluble drugs from solid oral dosage forms containing SMES.

Nanostructured lipid carriers as a novel oral delivery system for triptolide: induced changes in pharmacokinetics profile associated with reduced toxicity in male rats

After oral administration in rodents, triptolide (TP), a diterpenoid triepoxide compound, active as anti-inflammatory, immunosuppressive, anti-fertility, anti-cystogenesis, and anticancer agent, is rapidly absorbed into the blood circulation (from 5.0 to 19.5 minutes after dosing, depending on the rodent species) followed by a short elimination half-life (from about 20 minutes to less than 1 hour). Such significant and rapid fluctuations of TP in plasma likely contribute to its toxicity, which is characterized by injury to hepatic, renal, digestive, reproductive, and hematological systems. With the aim of prolonging drug release and improving its safety, TP-loaded nanostructured lipid carriers (TP-NLCs), composed of Compritol® 888 ATO (solid lipid) and Capryol™ 90 (liquid lipid), were developed using a microemulsion technique. The formulated TP-NLCs were also characterized and in vitro release was evaluated using the dialysis bag diffusion technique. In addition, the pharmacokinetics and toxicology profiles of TP-NLCs were compared to free TP and TP-loaded solid lipid nanoparticles (TP-SLNs; containing Compritol 888 ATO only). Results demonstrate that TP-NLCs had mean particle size of 231.8 nm, increased drug encapsulation with a 71.6% efficiency, and stable drug incorporation for over 1-month. TP-NLCs manifested a better in vitro sustained-release pattern compared to TP-SLNs. Furthermore, TP-NLCs prolonged mean residence time (MRT)0–t (P<0.001, P<0.001), delayed Tmax (P<0.01, P<0.05) and decreased Cmax (P<0.01, P<0.05) compared to free TP and TP-SLNs, respectively, which was associated with reduced subacute toxicity in male rats. In conclusion, our data suggest that TP-NLCs are superior to TP-SLNs and could be a promising oral delivery system for a safer use of TP.