Enhancement of stability and skin permeation by sucrose stearate and cyclodextrins in progesterone nanoemulsions

Effect of cell-penetrating peptide-coated nanostructured lipid carriers on the oral absorption of tripterine

PURPOSE

To develop nanostructured-lipid carriers (NLCs) coated with cell-penetrating peptides (CPP) for improving the oral bioavailability of tripterine.

METHODS

We prepared CPP-coated tripterine-loaded NLCs (CT-NLCs) by using a solvent evaporation method, and determined their physical properties. In vitro drug release was determined by using a dialysis bag diffusion technique, and intestinal toxicity was evaluated by performing MTT assay using Caco-2 cells. In vivo absorption was studied in an in situ rat intestinal perfusion model, and oral bioavailability was examined in beagles.

RESULTS

The average particle size, zeta potential, and encapsulation efficiency of the optimized CT-NLCs were 126.7 ± 9.2 nm, 28.7 ± 3.4 mV, and 72.64% ± 1.37%, respectively. The CT-NLCs showed a controlled release profile in vitro and had significantly lower intestinal cytotoxicity than the tripterine solution (P < 0.05). The absorption levels of tripterine from the CT-NLCs in the rat duodenum and jejunum were markedly higher than with tripterine-loaded NLCs without the CPP coating (T-NLCs), and with tripterine solution. Pharmacokinetic study showed that the maximum concentration of the CT-NLCs was greater than that of the T-NLCs and tripterine suspension, and that the time to maximum concentration of the CT-NLCs as well as the T-NLCs, was longer than that of the tripterine suspension. The relative oral bioavailability of the CT-NLCs compared to that of tripterine suspension and T-NLCs were 484.75% and 149.91% respectively.

CONCLUSION

The oral bioavailability of tripterine is dramatically increased by CT-NLCs. Therefore, CT-NLCs seem to be a promising carrier for oral delivery of tripterine.

Effect of γ-cyclodextrin on the in vitro skin permeation of a steroidal drug from nanoemulsions: impact of experimental setup

Numerous reports on the enhancement effect of cyclodextrins (CDs) on the skin permeation of dermally applied drugs exist, the majority of which is based on in vitro diffusion cell studies. The specific experimental setup of such studies may skew the obtained results, which is rarely discussed in the context of CD studies. Thus, the aim of this work was to conduct a systematic in vitro investigation of the permeation enhancement potential of γ-CD on a steroidal drug from a nanoemulsion. The role of critical diffusion cell parameters such as the dose of application, occlusive conditions, the nature of the receptor medium and the skin thickness were investigated. The results showed that significantly enhanced skin permeation rates of fludrocortisone acetate were indeed caused by 1% (w/w) of γ-CD at both finite and infinite dose conditions. At 0.5% (w/w) of γ-CD, significant enhancement was only achieved at infinite dose application. Additional in vitro tape stripping experiments confirmed these tendencies, but the observed effects did not reach statistical significance. It may be concluded that the full permeation enhancement potential of the CD as observed in the Franz-cell setup can only be realised at infinite dose conditions while preserving the formulation structure.

Nanoparticles and microparticles for skin drug delivery

Skin is a widely used route of delivery for local and systemic drugs and is potentially a route for their delivery as nanoparticles. The skin provides a natural physical barrier against particle penetration, but there are opportunities to deliver therapeutic nanoparticles, especially in diseased skin and to the openings of hair follicles. Whilst nanoparticle drug delivery has been touted as an enabling technology, its potential in treating local skin and systemic diseases has yet to be realised. Most drug delivery particle technologies are based on lipid carriers, i.e. solid lipid nanoparticles and nanoemulsions of around 300 nm in diameter, which are now considered microparticles. Metal nanoparticles are now recognized for seemingly small drug-like characteristics, i.e. antimicrobial activity and skin cancer prevention. We present our unpublished clinical data on nanoparticle penetration and previously published reports that support the hypothesis that nanoparticles >10nm in diameter are unlikely to penetrate through the stratum corneum into viable human skin but will accumulate in the hair follicle openings, especially after massage. However, significant uptake does occur after damage and in certain diseased skin. Current chemistry limits both atom by atom construction of complex particulates and delineating their molecular interactions within biological systems. In this review we discuss the skin as a nanoparticle barrier, recent work in the field of nanoparticle drug delivery to the skin, and future directions currently being explored.

Semi-solid Sucrose Stearate-Based Emulsions as Dermal Drug Delivery Systems

Mild non-ionic sucrose ester surfactants can be employed to produce lipid-based drug delivery systems for dermal application. Moreover, sucrose esters of intermediate lipophilicity such as sucrose stearate S-970 possess a peculiar rheological behavior which can be employed to create highly viscous semi-solid formulations without any further additives. Interestingly, it was possible to develop both viscous macroemulsions and fluid nanoemulsions with the same chemical composition merely by slight alteration of the production process. Optical light microscopy and cryo transmission electron microscopy (TEM) revealed that the sucrose ester led to the formation of an astonishing hydrophilic network at a concentration of only 5% w/w in the macroemulsion system. A small number of more finely structured aggregates composed of surplus surfactant were likewise detected in the nanoemulsions. These discoveries offer interesting possibilities to adapt the low viscosity of fluid O/W nanoemulsions for a more convenient application. Moreover, a simple and rapid production method for skin-friendly creamy O/W emulsions with excellent visual long-term stability is presented. It could be shown by franz-cell diffusion studies and in vitro tape stripping that the microviscosity within the semi-solid formulations was apparently not influenced by their increased macroviscosity: the release of three model drugs was not impaired by the complex network-like internal structure of the macroemulsions. These results indicate that the developed semi-solid emulsions with advantageous application properties are highly suitable for the unhindered delivery of lipophilic drugs despite their comparatively large particle size and high viscosity.

Formulation, biological and pharmacokinetic studies of sucrose ester-stabilized nanosuspensions of oleanolic Acid

PURPOSE

The aim of this study was to develop sucrose ester (SE)-stabilized oleanolic acid (OA) nanosuspensions (NS) for enhanced delivery.

METHODS

SEOA NS were prepared via O/W emulsion and organic solvent evaporation methods. The particles' size and polydispersity index were measured by nanosizer. Their percent encapsulation efficiency, saturation solubility and in vitro dissolution rate were obtained via HPLC. The in vitro bioefficacy was analyzed by MTT measurements in A549 human non-small-cell lung cancer cell line. The cellular uptake of OA and in vivo pharmacokinetics profile were determined using LC-ESI-MS/MS.

RESULTS

Spherical SEOA NS particles (~100 nm in diameter) were produced and found to be physicochemically stable over a month at 4°C. In particular, SEOA 4121 NS (SEL: SEP at 4:1 w/w; SE: OA at 2:1 w/w) produced the greatest increase in saturation solubility (1.89 mg/mL vs. 3.43 μg/mL), dissolution rate, cytotoxicity and bioavailability. Preliminary studies indicated that cellular uptake of SEOA NS by A549 cells was temperature-, concentration- and time-dependent.

CONCLUSION

Preparing OA as SE-stabilized NS particles provides a novel method to enhance saturation solubility, in vitro dissolution rate, bioefficacy and in vivo bioavailability of free OA and/or other potentially useful hydrophobic drugs.

Use of photoacoustic spectroscopy in the characterization of inclusion complexes of benzophenone-3-hydroxypropyl-β-cyclodextrin and ex vivo evaluation of the percutaneous penetration of sunscreen

This work is aimed to evaluate the application of photoacoustic spectroscopy (PAS) in the characterization of inclusion complexes of benzophenone-3 (BZ-3) and hydroxypropyl-β-cyclodextrin (HPCD) and to analyze the ex vivo percutaneous penetration of sunscreens and their reaction with the skin. The formation of inclusion complexes of BZ-3 and HPCD was performed by co-precipitation in stoichiometric ratios of 1:1 and 1:2. Thermal analysis and PAS characterized these inclusion complexes, and they indicated that the stoichiometric ratio of 1:2 was best. Sunscreen formulations were prepared and applied on the ears of rabbits. PAS suggested that the formulation with the complex resulted in lower penetration of BZ-3. Histological analysis demonstrated that the use of the formulation with BZ-3 was associated with an increase in the comedogenic effect and the presence of acanthosis, while no such effect was found in the formulation with the complex. The formulation with the BZ-3-HPCD complex is a promising strategy for improving the photoprotective effect of BZ-3. PAS can be used in the study of inclusion complexes with cyclodextrins and the evaluation of the percutaneous penetration of sunscreen formulations. Further tests are being conducted using PAS to monitor in vivo changes in the optical absorption spectra of formulations and to investigate their photostability.

Development of sucrose stearate-based nanoemulsions and optimisation through γ-cyclodextrin

Nanoemulsions aimed at dermal drug delivery are usually stabilised by natural lecithins. However, lecithin has a high tendency towards self-aggregation and is prone to chemical degradation. Therefore, the aim of this study was to develop nanoemulsions with improved structure and long-term stability by employing a natural sucrose ester mixture as sole surfactant. A thorough comparison between the novel sucrose stearate-based nanoemulsions and corresponding lecithin-based nanoemulsions revealed that the sucrose ester is superior in terms of emulsifying efficiency, droplet formation as well as physical and chemical stability. The novel formulations exhibited a remarkably homogeneous structure in cryo TEM investigations, as opposed to the variable structure observed for lecithin-based systems. The in vitro skin permeation rates of lipophilic drugs from sucrose stearate nanoemulsions were comparable to those obtained with their lecithin-based counterparts. Furthermore, it was observed that addition of γ-cyclodextrin led to enhanced skin permeation of the steroidal drug fludrocortisone acetate from 9.99±0.46 to 55.10±3.67 μg cm(-2) after 24 h in the case of sucrose stearate-based systems and from 9.98±0.64 to 98.62±24.89 μg cm(-2) after 24 h in the case of lecithin-based systems. This enhancement effect was significantly stronger in formulations based on lecithin (P<0.05), which indicates that synergistic mechanisms between the surfactant and the cyclodextrin are involved. Cryo TEM images suggest that the cyclodextrin is incorporated into the interfacial film, which might alter drug release rates and improve the droplet microstructure.