Stephânia Fleury Taveira

Development of topotecan loaded lipid nanoparticles for chemical stabilization and prolonged release

Topotecan is an important cytotoxic drug that has gained broad acceptance in clinical use for the treatment of refractory ovarian and small-cell lung cancer. The lactone active form of topotecan can be hydrolyzed in vivo, decreasing the drugs therapeutic efficacy. Lipid encapsulation may promote in vivo stabilization by removing topotecan from aqueous media. Earlier reports of topotecan lipid nanoencapsulation have focused on liposomal encapsulation; however, the higher stability and cost-effectiveness of solid lipid nanoparticles (SLN) highlight the potential of these nanoparticles as an advantageous carrier for topotecan. The initial motivation for this work was to develop, for the first time, solid lipid nanoparticles and nanostructured lipid carriers (NLC) with a high drug loading for topotecan. A microemulsion technique was employed to prepare SLNs and NLCs and produced homogeneous, small size, negatively charged lipid nanoparticles with high entrapment efficiency and satisfactory drug loading. However, low recovery of topotecan was observed when the microemulsion temperature was high and in order to obtain high quality nanoparticles, and precise control of the microemulsion temperature is critical. Nanoencapsulation sustained topotecan release and improved its chemical stability and cytotoxicity. Surprisingly, there were no significant differences between the NLCs and SLNs, and both are potential carriers for topotecan delivery.

Impact of lipid dynamic behavior on physical stability, in vitro release and skin permeation of genistein-loaded lipid nanoparticles

The aim of this study was to develop lipid nanoparticles to deliver genistein (GEN) to deeper skin layers. To do so, the impact of lipid dynamic behavior (nanoparticle flexibility) on stability, release and skin permeation studies was verified. GEN-loaded solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were obtained and characterization was undertaken. Freshly prepared nanoparticles were produced with similar features (i.e., drug loading). However, a higher level of crystallization in GEN-SLN formulation was observed in differential scanning calorimetry experiments. Electron paramagnetic resonance measurements showed a lower mobility of the spin labels in the SLN, which would indicate that NLC could be more flexible than SLN. Despite the fact that NLC demonstrated more fluidity, GEN was released more slowly from NLC than from SLN. Skin permeation studies demonstrated that lipid nanoparticles increased GEN skin retention. More flexible particles (NLC) also favored drug penetration into deeper skin layers. GEN-NLC would seem to be a promising formulation for GEN topical delivery.

In vitro skin penetration of clobetasol from lipid nanoparticles: drug extraction and quantitation in different skin layers

Clobetasol propionate (CP) is a potent topical corticosteroid that causes several cutaneous and systemic side effects. In the present work, CP was encapsulated in nanostructured lipid carriers (NLCs) to increase drug retention in the outer skin layers and improve the safety of topical therapy. NLCs were prepared using a microemulsion technique with a mixture of lecithin, taurodeoxycholate, stearic acid, and oleic acid. In vitro penetration studies were performed in a modified Franz-type diffusion cell, and porcine ears were used as a model of human skin. A simple and sensitive liquid chromatographic method was developed and validated for clobetasol determination in different skin layers. NLCs presented uniform size distribution, high zeta potentialand entrapment efficiency values (> 98%). The analytical procedure was validated according to FDA guidelines. Clobetasol recoveries from skin samples were higher than 85%, with no interference of skin components and NLC ingredients. In experiments, after 6 h, a higher drug accumulation in the stratum corneum arising from NLCs compared to aqueous CP solution was observed. Thus, the NLCs demonstrated high potential for targeting CP to the skin and ensuring drug accumulation in the stratum corneum.

Clobetasol‐loaded nanostructured lipid carriers for epidermal targeting

The aim of this study was to investigate in vitro the epidermal targeting potential of clobetasol propionate‐loaded nanostructured lipid carriers (CP‐NLC) when compared to that of chitosan‐coated (CP‐NLC‐C).

Development and characterization of PLGA nanocapsules of grandisin isolated from Virola surinamensis: in vitro release and cytotoxicity studies

The most studied phyto constituent isolated from Virola surinamensis (Rol. ex Rottb.) Warb., Myristicaceae, is the tetrahydrofuran neolignan grandisin, which exhibits a series of biological activities, including trypanocidal, larvicidal and antitumoral. Due to its extremely low solubility, additional studies, including in vivo investigations are challenged by the difficulties in the development of an effective drug delivery system for grandisin. The encapsulation in polymeric nanoparticles is a very attractive alternative for overcoming some of these limitations. In this work, PLGA nanocapsules loaded with grandisin were developed in an attempt to optimize the efficacy of grandisin as an antitumoral drug, with high drug loading and efficiency, prolonged drug release and increased physical-chemical stability. Mean diameter of the nanocapsules was lower than 200 nm, with very low polydispersity. Encapsulation efficiency was above 90%. A sustained in vitro drug release was achieved for up to twenty days and cytotoxicity was markedly increased (IC50 for grandisin-NC and grandisin were 0.005 µM and 0.078 µM, respectively), indicating that polymeric nanocapsules are a potential drug delivery system for grandisin allowing the preparation of formulations viable for further in vivo studies.

Topotecan‐loaded lipid nanoparticles as a viable tool for the topical treatment of skin cancers

This work aimed to evaluate semisolid formulations containing topotecan (TPT) loaded nanostructured lipid carriers (NLC) for topical treatment of skin cancers, as TPT is effective against a variety of tumours. A formulation which increases TPT skin permeation would be extremely desirable.

Improvement of enalapril maleate chemical stability by high shear melting granulation

Abstract Enalapril maleate is a widely used drug, which is chemically unstable when mixed with excipients resulting in enalaprilat and diketopiperazine as the main degradation products. The preparation of enalapril sodium salt has been used to improve drug stability in solid dosage forms; however, product rejection is observed when the chemical reaction for obtaining the sodium salt is not completely finished before packaging. In this study, granules were prepared by melting granulation using stearic acid or glyceryl monostearate, with a view to developing more stable enalapril maleate solid dosage forms. The granules were prepared in a laboratory-scale high shear mixer and compressed in a rotary machine. Size distribution, flow properties, in vitro drug release and enalapril maleate chemical stability were evaluated and compared with data obtained from tablets prepared without hydrophobic binders. All formulations showed good physical properties and immediate drug release. The greatest improvement in the enalapril maleate stability was observed in formulations containing stearic acid. This study showed that hot melting granulation could be successfully used to prepare enalapril maleate granules which could substitute the in situ formation of enalapril sodium salt, since they provided better enalapril stability in solid dosage forms.

Preparation of pellets containing Pothomorphe umbellata extracts by extrusion-spheronization: improvement of 4-nerolidylcatechol photostability

Pothomorphe umbellata (L.) Miq., Piperaceae, has been extensively used in Brazilian folk medicine and it is well known for its strong antioxidant properties. However, its main active constituent, 4-nerolydilcatechol (4-NC), is sensitive to ultraviolet and visible light, which can limit the use of intermediate and final herbal preparations of this species. In the present work, coated multiparticulate solid dosage forms of P. umbellata were obtained with the purpose of increasing the stability of 4-NC. P. umbellata extract was used as a wetting liquid for the preparation of pellets by extrusion-spheronization. Pellets were coated in a fluidized bed by three different polymers (hydroxypropylmethylcellulose (HPMC), polyvynilpirrolidone K-30 (PVP-K30), and polyvinyl alcohol-polyethylene glycol graft-copolymer (PVAPEG)). 4-NC photostability was evaluated by an accelerated photostability protocol. Pellets showed a narrow size distribution and low friability. 4-NC photodegradation followed a second order degradation kinetics with similar k values for the percolate, uncoated pellets and HPMC coated pellets. Photoprotection was higher in pellets coated with PVP-K30 and PVA-PEG. PVA-PEG coated pellets with 6 and 9% weight gain resulted in a final concentration of 4-NC approximately cinco times higher than uncoated pellets or liquid extracts, suggesting the potential of this formulation as a multiparticulate solid dosage form for P. umbellata extracts.

Voriconazole-loaded nanostructured lipid carriers (NLC) for drug delivery in deeper regions of the nail plate

Voriconazole-loaded nanostructured lipid carriers (VOR-NLC) were developed and drug penetration evaluated in porcine hooves in vitro. Synergistic effect of urea (Ur), selected among other known chemical enhancers according to hoof hydration potential, was also evaluated. VOR-NLC presented a high encapsulation efficiency (74.52±2.13%), approximate mean diameter of 230nm and were positively charged (+27.32±2.74mV). Stability studies indicated they were stable under refrigeration (4±2°C) for up to 150days. SEM images revealed hooves treated with VOR-NLC and VOR-NLC-Ur suffered a disturbance on the surface depicting high roughness and porosity. Permeation data showed a substantial VOR amount retained in superficial hooves sections independent of the formulation used (2.42±0.26; 2.52±0.36 and 2.41±0.60μg/cm2 for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p>0.05). Still, successive extractions, revealed the amount of VOR retained in deeper regions was significantly higher when VOR-NLC or VOR-NLC-Ur was used (0.17±0.04, 0.47±0.14 and 0.36±0.07μg/cm2 for unloaded VOR, VOR-NLC and VOR-NLC-Ur, respectively, p<0.05). Such results indicate NLC are promising formulations for the management of onychomycosis. Further studies in diseased nail plates are necessary.

The role of formulation and follicular pathway in voriconazole cutaneous delivery from liposomes and nanostructured lipid carriers

In general, colloids provide increased cutaneous permeation of drugs. Still, skin interaction and main pathways for drug diffusion may vary depending on system and formulation characteristics. The knowledge of how different colloidal systems interact with biological membranes and the formulation impact on delivery is especially relevant for drugs that can be encapsulated in multiple nanosystems, as voriconazole (VOR). In here, we compared VOR release and permeation profile from liposomes (LP) and nanostructured lipid carriers (NLC) in aqueous colloidal dispersions and in gel formulations. Despite the controlled drug release provided by gel formulations, formulation only had a significant impact on drug skin accumulation from LP. The reduced mobility in gel formulations compromised follicle deposition and drug retention in the skin. Such a hypothesis was confirmed by permeation experiments evaluating follicle pathway influence. Follicular route also had an influence on delivery from NLC, which was only significant for total drug that reached the acceptor medium. These differences could be attributed to the mechanisms of colloid interaction with the skin and subsequent drug release. Follicle LP deposition and slow drug release leads to higher cutaneous amounts whilst NLC interaction with skin and fast drug release leads to fast drug diffusion and deeper penetration. By the low MIC50 values encountered against Trichophyton rubrum (∼ 0.001 μg/mL), permeated amounts could inhibit fungal growth, regardless the system. In conclusion, both LP and NLC seem to be valuable systems for cutaneous VOR delivery. Fluidic formulations could provide better efficiency for cutaneous drug delivery from LP.