Preformulation and characterization of raloxifene-loaded lipid nanoparticles for transdermal administration.

Transdermal administration of raloxifene hydrochloride (RLX)-loaded nanostructured lipid carriers (NLCs) has been proposed to circumvent its low oral bioavailability (2%). Preformulation studies were carried out to evaluate drug-excipient compatibility of various adjuvants commonly used for NLC preparation (waxes, cholesterol, compritol, gelucire, span 60, span 80, span 85, tween 80, poloxamer 188, oleic acid, caprylic/capric triglyceride, and castor oil). It was used differential scanning calorimetry (DSC), isothermal stress testing (IST), and solubility studies. The most promising excipients were chosen for NLC obtention, and full characterization was done, including in vitro skin permeation. DSC curves suggested drug-excipient interaction among some compounds, and the IST study showed incompatibility of RLX with waxes, compritol, cholesterol, span 60, and poloxamer 188. Solubility studies helped select gelucire, caprylic/capric triglyceride, span 80, and tween 80 for NLC production. Twelve NLCs were obtained (NLC1 to NLC12), but NLC7 and NLC8 were the most promising ones. In vitro release studies demonstrated that NLC7 and NLC8 were able to control RLX release (14.74 and 9.07% at 24 h, respectively) compared with the unloaded drug (> 90% at 24 h). Unloaded RLX did not permeate the diffusion cells' receptor medium and showed higher drug skin retention (11-fold) than RLX-loaded NLC. NLC reduced RLX skin retention, favoring drug permeation to deeper skin layers. NLC7 increased drug flux is 2.4-fold. NLC7 is a promising formulation for RLX transdermal drug delivery.

Combination of lipid nanoparticles and iontophoresis for enhanced lopinavir skin permeation: Impact of electric current on lipid dynamics.

Nanostructured lipid carriers (NLC)-loaded with lopinavir (LPV) were developed for its iontophoretic transdermal delivery. Electronic paramagnetic resonance (EPR) spectroscopy of fatty acid spin labels and differential scanning calorimetry (DSC) were applied to investigate the lipid dynamic behavior of NLC before and after the electrical current. In vitro release and permeation studies, with and without anodic and cathodic iontophoresis were also performed. NLC-LPV had nanometric size (179.0 ± 2.5 nm), high drug load (∼x223C 4.14%) and entrapment efficiency (EE) (∼x223C 80%). NLC-LPV was chemically and physically stable after applying an electric current. The electrical current reduced EE after 3 h (67.21 ± 2.64%), resulting in faster LPV in vitro release. EPR demonstrated that iontophoresis decreased NLC lipid dynamics, which is a long-lasting effect. DSC studies demonstrated that electrical current could trigger the polymorphic transition of NLC and drug solubilization in the lipid matrix. NLC-LPV, combined with iontophoresis, allowed drug quantification in the receptor medium, unlike unloaded drugs. Cathodic iontophoresis enabled the quantification of about 7.9 µg/cm2 of LPV in the receptor medium. Passive NLC-LPV studies had to be done for an additional 42 h to achieve similar concentrations. Besides, anodic iontophoresis increased by 1.8-fold the amount of LPV in the receptor medium, demonstrating a promising antiviral therapy strategy.

Development of carvedilol-loaded lipid nanoparticles with compatible lipids and enhanced skin permeation in different skin models.

The study aimed to develop lipid nanoparticles using excipients compatible with carvedilol (CARV) for enhanced transdermal drug delivery. Nanostructured lipid carriers (NLC) were successfully obtained and fully characterised. Franz diffusion cells were used for release and in vitro permeation studies in the porcine epidermis (EP) and full-thickness rat skin. NLC4 and NLC5 (0.5 mg/mL of CARV) presented small size (80.58 ± 1.70 and 116.80 ± 12.23 nm, respectively) and entrapment efficiency of 98.14 ± 0.79 and 98.27 ± 0.99%, respectively. CARV-loaded NLC4 and NLC5 controlled drug release. NLC4 allowed CAR permeation through porcine EP in greater amounts than NLC5, i.e. 11.83 ± 4.71 µg/cm2 compared to 3.06 ± 0.79 µg/cm2. NLC4 increased CARV permeation by 2.5-fold compared to the unloaded drug in rat skin studies (13.73 ± 4.12 versus 5.31 ± 1.56 µg/cm2). NLC4 seems to be a promising carrier for the transdermal delivery of CARV.

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.

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

OBJECTIVES: 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. METHODS: TPT-NLC were prepared and incorporated in hydrogels with hydroxyethyl cellulose and chitosan (TPT-NLC-HEC and TPT-NLC-Ch, respectively). Control formulations were obtained by dispersing TPT in HEC and Ch hydrogels (TPT-HEC and TPT-Ch). KEY FINDINGS: TPT-NLC-HEC and TPT-NLC-Ch showed to maintain the drug and nanoparticle dispersions stable for up to 30 days. When nanoparticles were incorporated into gels, TPT release was significantly decreased (P < 0.05). Still, TPT-NLC-HEC increased 2.37 times permeation compared with TPT-HEC (11.9 and 5.0 µg/cm2 , respectively). Cell culture experiments with B16F10 melanoma demonstrated that nanoencapsulation significantly increased TPT cytotoxicity (P < 0.05). TPT-NLC was more toxic than free TPT, with IC50 value of 5.74 µg/ml, whereas free TPT had an IC50 > 20 µg/ml. As skin permeated values of TPT from developed formulation (TPT-NLC) were superior to melanoma IC50, it can be extrapolated that chemotherapeutic permeated amounts may be sufficient for a therapeutic effect. CONCLUSIONS: TPT-NLC-HEC may be a valuable tool for the topical treatment of skin cancers.

Development of a High-Performance Liquid Chromatographic Method for Asiaticoside Quantification in Different Skin Layers after Topical Application of a Centella asiatica Extract.

The topical application of Centella asiatica extract has been commonly used for many different purposes but especially for cosmetic use in the treatment of gynoid lipodystrophy. Asiaticoside, the most active component in this extract, is responsible for its therapeutic activities. However, little is known to date about asiaticoside skin penetration. Thus, an analytical method for asiaticoside quantification in different skin layers after the topical application of C. asiatica extract was developed and skin permeation studies were performed with the plant extract to apply the analytical method developed. An extraction procedure to recover asiaticoside from the biological matrix was also developed. Asiaticoside was assayed by HPLC/UV (high-performance liquid chromatography-ultraviolet detection) using a gradient of ACN (acetonitrile) and 0.2% phosphoric acid (flow rate of 1.0 mL/min). The analytical procedure was validated according to U. S. Food and Drug Administration guidelines. Selectivity was shown, as endogenous skin components did not interfere with the asiaticoside peak. Analytical curve was linear (3 to 60 µg/mL) and the lower limit of quantification was determined (3 µg/mL). Asiaticoside recoveries from skin samples were 95.1% and 66.7% for the stratum corneum and remaining skin, respectively. After 48 h of in vitro permeation studies, a substantial amount of asiaticoside was quantified in the skin layers. The presence of asiaticoside was also detected in the receptor solution of Franz diffusion cells after 48 h (5.81 ± 1.00 µg/mL). The method was reliable and reproducible for asiaticoside quantification in skin samples, thereby making it possible to determine the cutaneous penetration profile of this drug in permeation studies.

Improved tacrolimus skin permeation by co-encapsulation with clobetasol in lipid nanoparticles: Study of drug effects in lipid matrix by electron paramagnetic resonance.

Combined therapy with corticosteroids and immunosuppressant-loaded nanostructured lipid carriers (NLC) could be useful in the treatment of skin diseases. To circumvent NLC loading capacity problems, loaded drugs should have different physicochemical characteristics, such as tacrolimus (TAC) and clobetasol (CLO). Therefore, in the present study, TAC and CLO were encapsulated in NLC (TAC-NLC, CLO-NLC and TAC+CLO-NLC), coated or otherwise with chitosan. Electron paramagnetic resonance (EPR) spectroscopy of different spin labels was used to investigate the impact of drug and oil incorporation on the lipid dynamic behavior of the lipid matrices. In addition, the impact of co-encapsulation on drug release and skin permeation was evaluated. Entrapment efficiency was greater than 90% for both drugs, even when the maximum drug loading achieved for TAC-NLC and CLO-NLC was kept at TAC+CLO-NLC, because TAC is more soluble in the solid lipid and CLO in the liquid lipid. EPR data indicated that both drugs reduced the lipid fluidity near the polar surface of the lipid matrix, which suggests their presence in this region. In addition, EPR data showed that liquid lipid is also present in more superficial regions of the nanoparticle matrix. CLO was released faster than TAC from TAC+CLO-NLC, probably because it is more soluble in the liquid lipid. TAC skin penetration was affected by CLO. A 5-fold increase in TAC penetration was observed from TAC+CLO-NLC when compared to TAC-NLC formulations. Coating also increased TAC and CLO permeation to deeper skin layers (1.8-fold and 1.6-fold, respectively). TAC+CLO-NLC seems to be an effective strategy for topical delivery of TAC and CLO, and thus constitutes promising formulations for the treatment of skin diseases.

Clobetasol-loaded nanostructured lipid carriers for epidermal targeting.

OBJECTIVES: 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). METHODS: CP-NLC were prepared by microemulsion method and characterized by dynamic light scattering, transmission electron microscopy, in vitro release and permeation studies. To verify epidermal targeting, permeation studies were performed in two sets of experiments. For the first set, the skin was removed from the diffusion cell and stratum corneum (SC) was separated from the remaining skin (RS). For the second set, the whole epidermis (EP) was separated from the dermis (DER). CP quantification was performed in each skin layer. KEY FINDINGS: A novel clobetasol propionate-loaded NLC was produced with 1/5th of the drug dose used in commercial formulations and, even so, presented greater skin permeation. Both chitosan-coated and uncoated NLC enhanced the amount of CP in the epidermis more than 80-fold when compared to the commercial formulation (20.26 ± 2.77; 17.85 ± 0.49 and 0.22 ± 0.02 µg/cm(2) , respectively). Differently from chitosan-coated NLC, the uncoated NLC did not show dermal retention. CONCLUSIONS: NLC proved to be a system with potential for targeting drug delivery to the epidermal layer.

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.