Chunliu Zhu

Self-assembled liquid crystalline nanoparticles as a novel ophthalmic delivery system for dexamethasone: Improving preocular retention and ocular bioavailability

The object of this study was to design novel self-assembled liquid crystalline nanoparticles (cubosomes) as an ophthalmic delivery system for dexamethasone (DEX) to improve its preocular retention and ocular bioavailability. DEX cubosome particles were produced by fragmenting a cubic crystalline phase of monoolein and water in the presence of stabilizer Poloxamer 407. Small angle X-ray diffraction (SAXR) profiles revealed its internal structure as Pn3m space group, indicating the diamond cubic phase. In vitro, the apparent permeability coefficient of DEX administered in cubosomes exhibited a 4.5-fold (F1) and 3.5-fold (F2) increase compared to that of Dex-Na phosphate eye drops. Preocular retention studies revealed that the retention of cubosomes was significantly longer than that of solution and carbopol gel, with AUC(0-->180min) of Rh B cubosomes being 2-3-fold higher than that of the other two formulations. In vivo pharmacokinetics in aqueous humor was evaluated by microdialysis, which indicated a 1.8-fold (F1) increase in AUC(0-->240min) of DEX administered in cubosomes relative to that of Dex-Na phosphate eye drops, with about an 8-fold increase compared to that of DEX suspension. Corneal cross-sections after incubation with DEX cubosomes demonstrated an unaffected corneal structure and tissue integrity, which indicated the good biocompatibility of DEX cubosomes. In conclusion, self-assembled liquid crystalline nanoparticles might represent a promising vehicle for effective ocular drug delivery.

Novel microemulsion in situ electrolyte-triggered gelling system for ophthalmic delivery of lipophilic cyclosporine A: In vitro and in vivo results

The objective of the present study was to design a novel microemulsion in situ electrolyte-triggered gelling system for ophthalmic delivery of a lipophilic drug, cyclosporine A (CsA). A CsA-loaded microemulsion was prepared using castor oil, Solutol HS 15 (surfactant), glycerol and water. This microemulsion was then dispersed in a Kelcogel solution to form the final microemulsion in situ electrolyte-triggered gelling system. In vitro, the viscosity of the CsA microemulsion Kelcogel system increased dramatically on dilution with artificial tear fluid and exhibited pseudo-plastic rheology. In vivo results revealed that the AUC(0-->32 h) of corneal CsA for the microemulsion Kelcogel system was approximately three-fold greater than for a CsA emulsion. Moreover, at 32 h after administration, CsA concentrations delivered by the microemulsion Kelcogel system remained at therapeutic levels in the cornea. This CsA microemulsion in situ electrolyte-triggered gelling system might provide an alternative approach to deliver prolonged precorneal residence time of CsA for preventing cornea allograft rejection.

Intestinal mucosa permeability following oral insulin delivery using core shell corona nanolipoparticles

Chitosan nanoparticles (NC) have excellent capacity for protein entrapment, favorable epithelial permeability, and are regarded as promising nanocarriers for oral protein delivery. Herein, we designed and evaluated a class of core shell corona nanolipoparticles (CSC) to further improve the absorption through enhanced intestinal mucus penetration. CSC contains chitosan nanoparticles as a core component and pluronic F127-lipid vesicles as a shell with hydrophilic chain and polyethylene oxide PEO as a corona. These particles were developed by hydration of a dry pluronic F127-lipid film with NC suspensions followed by extrusion. Insulin nested inside CSC was well protected from enzymatic degradation. Compared with NC, CSC exhibited significantly higher efficiency of mucosal penetration and, consequently, higher cellular internalization of insulin in mucus secreting E12 cells. The cellular level of insulin after CSC treatment was 36-fold higher compared to treatment with free insulin, and 10-fold higher compared to NC. CSC significantly facilitated the permeation of insulin across the ileum epithelia, as demonstrated in an ex vivo study and an in vivo absorption study. CSC pharmacological studies in diabetic rats showed that the hypoglycemic effects of orally administrated CSC were 2.5-fold higher compared to NC. In conclusion, CSC is a promising oral protein delivery system to enhance the stability, intestinal mucosal permeability, and oral absorption of insulin.

Novel mucus-penetrating liposomes as a potential oral drug delivery system: preparation, in vitro characterization, and enhanced cellular uptake

Background The aim of this study was to investigate the intestinal mucus-penetrating properties and intestinal cellular uptake of two types of liposomes modified by Pluronic F127 (PF127). Methods The two types of liposomes, ie, PF127-inlaid liposomes and PF127-adsorbed liposomes, were prepared by a thin-film hydration method followed by extrusion, in which coumarin 6 was loaded as a fluorescence marker. A modified Franz diffusion cell mounted with the intestinal mucus of rats was used to study the diffusion characteristics of the two types of PF127 liposomes. Cell uptake studies were conducted in Caco-2 cells and analyzed using confocal laser scanning microcopy as well as flow cytometry. Results The diffusion efficiency of the two types of PF127-modified liposomes through intestinal rat mucus was 5–7-fold higher than that of unmodified liposomes. Compared with unmodified liposomes, PF127-inlaid liposomes showed significantly higher cellular uptake of courmarin 6. PF127-adsorbed liposomes showed a lower cellular uptake. Moreover, and interestingly, the two types of PF127-modified liposomes showed different cellular uptake mechanisms in Caco-2 cells. Conclusion PF127-inlaid liposomes with improved intestinal mucus-penetrating ability and enhanced cellular uptake might be a potential carrier candidate for oral drug delivery.

Comparative study of Pluronic® F127-modified liposomes and chitosan-modified liposomes for mucus penetration and oral absorption of cyclosporine A in rats

Liposomes modified using cationic and hydrophilic nonionic polymers are 2 popular carriers for improving oral drug absorption. Cationic polymer-modified liposomes can adhere to the intestinal wall mucus (mucoadhesive type), while liposomes modified using hydrophilic nonionic polymers can penetrate across the mucus barrier (mucus-penetrating type). Chitosan-modified liposomes (CS-Lip, mucoadhesive type) and Pluronic(®) F127-modified liposomes (PF127-Lip, mucus-penetrating type) were engineered to investigate the differences between these mucoadhesive and mucus-penetrating systems in oral absorption of a poorly soluble drug, cyclosporine A (CyA). Stability of CS-Lip and PF127-Lip was studied in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF). The intestinal mucus adhesion or penetration of liposomes was studied by confocal laser scanning microcopy and fluorophotometry using coumarin 6 as the fluorescent probe. The oral absorption of CyA-loaded liposomes was also studied in Sprague-Dawley rats. In vitro and in vivo studies revealed that CS-Lip tended to aggregate in SIF, to be trapped by mucus, to remain mainly in the upper portion of the intestinal tract, and to show limited penetration ability. In contrast, PF127-Lip were more stable in the SIF and SGF, were found throughout the intestinal tract, and were able to penetrate the mucus layers to reach the epithelial surface. Pharmacokinetic analysis in rats showed that the Cmax and AUC0-t of PF127-Lip were 1.73- and 1.84-fold higher than those of CS-Lip, respectively (P<0.05). In conclusion, the stability and mucus-penetrating ability of PF127-Lip in the gastrointestinal tract rendered it more suitable than the mucoadhesive CS-Lip for oral delivery CyA.

Lipid-based formulations to enhance oral bioavailability of the poorly water-soluble drug anethol trithione: effects of lipid composition and formulation.

This study has explored the use of lipid-based formulations to enhance the oral bioavailability of the poorly water-soluble drug anethol trithione (ATT), and compared the performance of different formulations. Two groups of lipid-based formulations, sub-microemulsion (SME) and oil solution, were prepared using short (SCT), medium (MCT) and long (LCT) chain triglycerides respectively; aqueous suspension was used as the reference formulation. In vitro and in vivo studies were conducted to investigate the impact of lipid composition and formulation on drug absorption. In vitro digestion was used to analyze lipid digestion rates and drug distribution/solubilization. After in vitro digestion, the performance rank order for drug solubilization was SCT<MCT<LCT. SME formulations were digested more rapidly in vitro than oil solutions. The bioavailability of the drug from different formulations was investigated in rats. All six lipid-based formulations enhanced drug absorption compared to the aqueous suspension. For the SMEs, which were rapidly digested, in vivo bioavailability increased in accordance with the increase of solubilization data obtained by in vitro digestion, with the rank order SCT-SME<MCT-SME<LCT-SME. For the oil solutions, which were digested more slowly, there was no significant difference in drug bioavailability for the different formulations. In conclusion, lipid-based formulations can enhance the oral bioavailability of ATT, and for this BCS class II drug, both the lipid composition and type of lipid formulation are likely to govern in vivo performance.

Novel vehicle based on cubosomes for ophthalmic delivery of flurbiprofen with low irritancy and high bioavailability

AbstractAim:To develop a novel vehicle based on cubosomes as an ophthalmic drug delivery system for flurbiprofen (FB) to reduce ocular irritancy and improve bioavailability.Methods:FB-loaded cubosomes were prepared using hot and high-pressure homogenization. Cubosomes were then characterized by particle size, zeta potential, encapsulation efficiency, particle morphology, inner cubic structure and in vitro release. Corneal permeation was evaluated using modified Franz-type cells. Ocular irritation was then evaluated using both the Draize method and histological examination. The ocular pharmacokinetics of FB was determined using microdialysis.Results:The particle size of each cubosome formulation was about 150 nm. A bicontinuous cubic phase of cubic P-type was determined using cryo-transmission electron microscopy (cryo-TEM) observation and small angle X-ray scattering (SAXS) analysis. In vitro corneal permeation study revealed that FB formulated in cubosomes exhibited 2.5-fold (F1) and 2.0-fold (F2) increase in Papp compared with FB PBS. In the ocular irritation test, irritation scores for each group were less than 2, indicating that all formulations exhibited excellent ocular tolerance. Histological examination revealed that neither the structure nor the integrity of the cornea was visibly affected after incubation with FB cubosomes. The AUC of FB administered as FB cubosome F2 was 486.36±38.93 ng·mL−1·min·μg−1, which was significantly higher than that of FB Na eye drops (P<0.01). Compared with FB Na eye drops, the Tmax of FB cubosome F2 was about 1.6-fold higher and the MRT was also significantly longer (P<0.001).Conclusion:This novel low-irritant vehicle based on cubosomes might be a promising system for effective ocular drug delivery.

Dual-functional liposome for tumor targeting and overcoming multidrug resistance in hepatocellular carcinoma cells

The purpose of this study was to design and evaluate the dual-functional liposome (LPG) with synthetic polymeric nano-biomaterial (Gal-P123) that targets cancer cells and reverses multidrug resistance (MDR) in hepatocellular carcinoma (HCC) cells. The mitoxantrone (MX) loaded LPG (MX-LPG) was about 100 nm in diameter, spherically shaped, and had an encapsulation efficiency of 97.3%. The cytotoxicity and cellular uptake of MX-LPG were evaluated in HCC Huh-7 cells. BCRP-overexpressing MDCKII/BCRP cells were used to certify the inhibitory effect of LPG on drug efflux transporter. Compared with MX, MX-LPG had 2.3-fold higher cytotoxicity in Huh-7 cells and a 14.9-fold increase in cellular MX accumulation in MDCKII/BCRP cells. The pharmacokinetic study in rats showed that LPG significantly prolonged the circulation time and enhanced the bioavailability of MX. Moreover, MX-LPG increased antitumor activity and improved selectivity in BALB/c mice bearing orthotopic xenograft HCC tumors.

Supersaturated polymeric micelles for oral cyclosporine A delivery

Polymeric micelles provide a promising platform for improving oral absorption of poorly soluble drugs. However, improved understanding of how drug retention within the hydrophobic micelle core can reduce drug absorption is required. We designed supersaturated polymeric micelles (Super-PMs) to increase molecularly dissolved drug concentration and gain an insight into the effect of the degree of supersaturation on oral absorption of cyclosporine A (CsA) in rats. The drug release from Super-PMs increased with an increase in initial supersaturation degrees in micelles. The cellular uptake of coumarin-6 was reduced by the retention of drug in polymer micelles. The transport flux of CsA across Caco-2 monolayer was increased with initial supersaturation degrees of 0.81-3.53 (p < 0.05). However, increase in supersaturation to 5.64 actually resulted in decreased CsA transport. The same trend was observed in a rat in vivo absorption study, in which the highest bioavailability of 134.6 ± 24.7% (relative to a commercial product, Sandimmun Neoral®, p<0.01) was achieved when the supersaturation degree was 3.53. These results demonstrated that Super-PMs were a promising drug delivery system for compounds with low aqueous solubility. This study also provided an experimental proof for the hypothesis that moderately supersaturated formulations are valuable alternative to high supersaturation formulations, resulting in optimal in vivo performance, and the degree of supersaturation should be carefully controlled to optimize drug absorption.

Cationic core-shell liponanoparticles for ocular gene delivery.

To achieve enhanced gene transfection efficiency with ocular eye-drop therapy, a cationic core-shell liponanoparticle (DLCS-NP) was designed by enveloping the plasmid-laden chitosan nanoparticle (CS-NP) into a cationic lipid shell. The cellular uptake of DLCS-NP was up to 1.25-fold and 5-fold higher than that of CS-NP and lipid-coated chitosan nanoparticles (LCS-NP), respectively. Further endocytosis inhibition investigation discovered that facilitated by the cationic outer lipid layer, several other distinct pathways (besides clathrin-mediated endocytosis) were involved in the endocytosis of DLCS-NP. Endolysosome trafficking experiment verified that cationic lipid coating could facilitate the endolysosome escape of DLCS-NP. Consequently, using enhanced green fluorescence protein (EGFP) as a reporter gene, DLCS-NP-treated human conjunctival epithelial cells exhibited 3.1- and 3.5-fold more intense EGFP expression than that of LCS-NP and CS-NP, respectively. Finally, in vivo transfection experiments on rabbits revealed that EGFP expression exhibited 2.52-fold increase in DLCS-NP group than that of CS-NP group. In summary, this type of cationic core-shell liponanoparticle, possessing multiple functions including better DNA protecting effect, superior cellular uptake efficiency, utilization of multiple endocytic pathways, and endolysosome escaping ability, may represent a promising strategy for ocular gene delivery.