Lucas Antônio Miranda Ferreira

Formation of ion pairing as an alternative to improve encapsulation and stability and to reduce skin irritation of retinoic acid loaded in solid lipid nanoparticles.

This work aims to investigate the influence of the formation of ion pairing between all-trans retinoic acid (RA) and a lipophilic amine (stearylamine; STE) on the drug encapsulation efficiency (EE) and stability of solid lipid nanoparticles (SLNs). The SLNs were characterized for EE and size. The EE and particle size were significantly improved and reduced, respectively, when the surfactant or co-surfactant concentration increased. However, while the formulation without STE allowed only 13% of RA encapsulation, the EE for RA-STE-loaded SLNs was 94%. The stability studies showed a significant decrease in EE for the SLNs without STE, while, for SLNs loaded with RA and STE, the EE remained constant after 360 days. The interactions among ion pairing components and the lipid matrix were investigated through small-angle X-ray scattering (SAXS). The SAXS analysis revealed the presence of RA in the crystalline form in SLNs without ion pairing, while crystalline RA was not observed in SLNs loaded with RA/amine. Skin irritation studies showed that the SLNs loaded with the ion pairing were significantly less irritating when compared to the marketed RA-cream. This novel SLN formulation represents a promising alternative for topical treatment of acne with RA.

New approach to improve encapsulation and antitumor activity of doxorubicin loaded in solid lipid nanoparticles

This work aimed to develop solid lipid nanoparticles (SLNs) loaded with doxorubicin evaluating the influence of docosahexaenoic acid (DHA), a polyunsaturated fatty acid that enhances the activity of anticancer drugs, on drug encapsulation efficiency (EE). The SLN were characterized for size, zeta potential, entrapment efficiency (EE) and drug release. Studies of in vitro antitumor activity and cellular uptake were also conducted. The reduction in particle size (from 127 ± 14 to 94 ± 1 nm) and negative charges were obtained for SLN loaded with DHA and triethanolamine (TEA), amine used to increase the solubility of doxorubicin in melted lipid. The EE was significantly improved from 36 ± 4% to 99 ± 2% for SLN without and with DHA at 0.4%, respectively. The doxorubicin release in a slightly acid medium (pH 5.0) was higher than that observed at physiological pH. The in vitro studies clearly showed the higher cytotoxicity of doxorubicin-DHA-loaded SLN than free doxorubicin+DHA on human lung tumor cell line (A549) and the improved cellular uptake achieved with the drug encapsulation can be an explanation. These findings suggest that DHA-doxorubicin-loaded SLN is a promising alternative for the treatment of cancer.

In Vitro Skin Permeation and Retention of Paromomycin from Liposomes for Topical Treatment of the Cutaneous Leishmaniasis

Paromomycin (PA), a very hydrophilic antibiotic, has been tested as an alternative topical treatment against cutaneous leishmaniasis (CL). Although this treatment has shown promising results, it has not been successful in accelerating the recovery in most cases. This could be attributed to the low skin penetration of PA. Liposomal formulations usually provide sustained and enhanced drug levels in skin. The aim of this study was to prepare liposomal formulations containing PA and to investigate their potential as topical delivery systems of this antileishmanial. Large multilamellar vesicles (MLVs) were prepared by conventional solvent evaporation method. Large unilamellar vesicles (LUVs) were prepared by reverse‐phase evaporation method. The lipids used were soybean phosphatidylcholine (PC) and PC:cholesterol (CH) (molar ratio 1:1). The skin permeation experiments across stripped and normal hairless mice skin were performed in modified Franz diffusion cells. The PA entrapment in LUV liposomes (20.4 ± 2.2%) was higher than that observed for MLV liposomes (7.5 ± 0.9%). Drug entrapment was 41.9 ± 6.2% and 27.2 ± 2.4% for PC and PC:CH LUV, respectively. The skin permeation was 1.55 ± 0.31%, 1.29 ± 0.40%, 0.20 ± 0.08%, and 0.50 ± 0.19% for PC LUV, PC:CH LUV, empty LUV + PA and aqueous solution, respectively. Controlled topical delivery, across stripped skin, was observed for PA entrapped in LUV liposomes.

New insights into the mode of action of ultradeformable vesicles using calcein as hydrophilic fluorescent marker.

Whether ultradeformable vesicles pass intact through the stratum corneum and can promote the transdermal absorption of any substance remain open questions. This paper presents different experimental approaches, based on the use of calcein as hydrophilic fluorescent marker, to probe the physicochemical and pharmacokinetic characteristics of these vesicles. Ultradeformable membranes made from natural phosphatidylcholine and sodium cholate were found to be highly permeable to calcein, as a result of the permeabilizing effects of sodium cholate and ethanol. In vitro skin permeation and in vivo transdermal (percutaneous) absorption studies were performed using hairless mice. Both studies indicated that deformable vesicles reduce the transdermal flux of calcein, when compared to a solution containing or not sodium cholate and ethanol. The data support the model that the transdermal absorption of calcein from deformable vesicles is controlled by the release of the drug from the formulation deposited onto the skin surface. Importantly, fluorescence measurements of the receptor fluid of the Franz diffusion cell after addition of Co(2+) quencher revealed that permeated calcein exists essentially under the non-encapsulated form. In conclusion, our results argue against the model that deformable vesicles would carry hydrophilic drugs across the skin and act as a sustained release system in deep tissues.

Development of a new solid lipid nanoparticle formulation containing retinoic acid for topical treatment of acne

The development of solid lipid nanoparticles (SLN) containing all-trans retinoic acid (RA) is an interesting approach to topical treatment of acne. SLN has potential for controlled release and follicular penetration, which can reduce adverse effects in comparison with conventional formulations. However, the encapsulation efficiency (EE) of RA in SLN is usually low, unless a high surfactant/lipid ratio is used. The aim of this work was to develop SLN with high EE using a low surfactant/lipid ratio. Different formulations of RA-loaded SLN were prepared using glyceryl behenate as lipid matrix. The particle size, EE, zeta potential and differential scanning calorimetry (DSC) were investigated. High EE in SLN was obtained with addition of amines. These results indicate that the utilization of amines is an interesting approach to improve the EE of RA in SLN using a low surfactant/lipid ratio.

Comedolytic effect and reduced skin irritation of a new formulation of all-trans retinoic acid-loaded solid lipid nanoparticles for topical treatment of acne

Novel drug delivery systems, such as solid lipid nanoparticles (SLN), have been proposed to reduce retinoic acid (RA)-induced skin irritation. However, one question still remains: could it be accomplished without reducing efficacy? To evaluate this question the comedolytic effects and epidermal thickening of RA-loaded SLN were compared to the conventional RA formulations (gel or cream), as well as the potential of these formulations to induce skin irritation. The comedolytic effects and epidermal thickening of these formulations, both containing RA at 0.01 or 0.05%, were investigated in a rhino mouse model, while the studies of RA-induced skin irritation were evaluated through rabbit skin irritation tests and in the rhino mouse model. RA-loaded SLN, as compared to the placebo, produced a comedolytic effect with a significant reduction of the utricle diameter, which proved to be similar to that observed for marketed gels or creams regardless of the RA concentration. RA formulations (SLN or marketed cream) also induced an epidermal proliferation leading to a thickened epidermis in treated animals. In both animals studied (rhino mice and rabbits), the RA-loaded SLN, when compared to conventional formulations, promoted a significant reduction in RA-induced skin irritation (erythema and scaling). Then, RA-loaded SLN represents an interesting alternative to reduce RA-induced skin irritation without reducing efficacy, and constitutes an innovative approach for the topical treatment of acne with RA.

Topical delivery and in vivo antileishmanial activity of paromomycin-loaded liposomes for treatment of cutaneous leishmaniasis

The present study aimed to evaluate the potential of liposomes loaded with paromomycin (PA), an aminoglycoside antibiotic associated with poor skin penetration, for the topical treatment of cutaneous leishmaniasis (CL). Fluid liposomes were prepared and characterized for particle size, zeta potential, and drug entrapment. Permeation studies were performed with two in vitro models: intact and stripped skin. The antileishmanial activity of free and liposomal PA was evaluated in BALB/c mice infected by Leishmania (L.) major. Drug entrapment ranged from 10 to 14%, and the type of vesicle had little influence on this parameter. Particle size and polydispersity index of the vesicles composed by phosphatidylcholine (PC) and PC/cholesterol (Chol) ranged from of 516 to 362 nm and 0.7 to 0.4, respectively. PA permeation across intact skin was low, regardless of the formulation tested, while drug penetration into skin (percent of the applied dose) from PC (7.2 ± 0.2%) and PC/Chol (4.8 ± 0.2%) liposomes was higher than solution (1.9 ± 0.1%). PA-loaded liposomes enhanced in vitro drug permeation across stripped skin and improved the in vivo antileishmanial activity in experimentally infected mice. Our findings suggest that the liposomes represent a promising alternative for the topical treatment of CL using PA.

Topical Delivery of Fluconazole: In Vitro Skin Penetration and Permeation Using Emulsions as Dosage Forms

ABSTRACT We investigated in vitro skin penetration and permeation of fluconazole from emulsions containing different penetration enhancers. Fluconazole permeation was high (15–65% of the applied dose) across hairless mouse skin and low (8–9%) across pig ear skin. Permeation across mice skin from a formulation containing propyleneglycol and isopropyl myristate was significantly higher than that observed with the paraffin oil and propyleneglycol or Transcutol® emulsions. With pig skin, the paraffin oil or isopropyl myristate and propyleneglycol emulsions showed similar skin permeation and penetration. However, these emulsions provided epidermal concentrations higher than the minimal inhibitory concentrations for most dermatophytes.

Combined topical paromomycin and oral miltefosine treatment of mice experimentally infected with Leishmania (Leishmania) major leads to reduction in both lesion size and systemic parasite burdens

OBJECTIVES This study aimed to investigate the activity of the combination of topical paromomycin gel and oral miltefosine for the treatment of experimental cutaneous leishmaniasis caused by Leishmania (Leishmania) major. METHODS The efficacy of the combination, evaluated by measuring lesion size and parasite burden in the skin and spleen, was assessed in BALB/c mice infected by L. (L.) major. Miltefosine was administered orally at 25 mg/kg/day for 10 days, while 10% paromomycin gel was applied topically twice a day for 10 days. RESULTS Treatment of the experimentally infected animals with topical paromomycin + oral miltefosine combination induced a statistically significant reduction in lesion size and parasite burden in the skin, with complete healing of ulcers, as compared with those treated with oral miltefosine or placebo. Furthermore, topical paromomycin + oral miltefosine combination was as effective as topical paromomycin alone to reduce the lesion size and parasite load in lesions. However, the efficacy of the combination was significantly higher than that observed for the other treatments, including topical paromomycin alone, in reducing the parasite burden in spleen. CONCLUSIONS The combination of topical paromomycin gel and oral miltefosine provides an enhanced efficacy in the treatment of L. (L.) major-infected mice, thus presenting a significantly higher activity than that observed for the monotherapeutic regimens.

Reductions in Skin and Systemic Parasite Burdens as a Combined Effect of Topical Paromomycin and Oral Miltefosine Treatment of Mice Experimentally Infected with Leishmania (Leishmania) amazonensis

ABSTRACT This study aimed to investigate the activity of a combination of topical paromomycin gel and oral miltefosine for the treatment of experimental cutaneous leishmaniasis caused by Leishmania (Leishmania) amazonensis. The efficacy of the combination, evaluated by measuring lesion size and parasite burden in the skin and spleen, was assessed in BALB/c mice infected by L. (L.) amazonensis. The miltefosine was administered orally at 10 mg/kg of body weight/day for 10 days, while 10% paromomycin gel was applied topically twice a day for 20 days. Treatment of the experimentally infected animals with a topical paromomycin-oral miltefosine combination induced a statistically significant reduction in lesion size and parasite burden in the skin and spleen, with complete healing of ulcers, compared with those treated with a placebo group. A combination of topical paromomycin gel and oral miltefosine provided enhanced efficacy in the treatment of L. (L.) amazonensis-infected mice, showing activity higher than that observed for the monotherapeutic regimens.