Preclinical evaluation of L-fucoside from lapachol-loaded nanoemulsion as a strategy to breast cancer treatment.

Breast cancer prevails as the most common cancer in women, underscoring an urgent need for more effective therapies. This study explores the potential of our newly developed nanoemulsion containing a novel fucoside derivative of lapachol (NE-F-LapA) as an intravenous treatment strategy. We sought to overcome the solubility issues associated with fucoside with this improved drug delivery strategy that enhances tumor delivery and mitigates other dose-limiting toxicities. Nanoemulsion was prepared and characterized by DLS, zeta potential, encapsulation efficiency, and storage stability. Cytotoxicity against breast cancer cell lines (4T1 and MDA-MB-231) and non-tumor human fibroblasts (NTHF) were evaluated. In vivo assays included antitumoral activity performance and acute systemic toxicity in mice models. NE-F-LapA was synthesized and optimized to 200 nm size, - 20 mV zeta potential, and near-complete (>98%) drug encapsulation. Stability exceeded 6 months, and biological fluid exposure maintained suitable properties for administration. In vitro, NE-F-LapA showed high toxicity (3 µM) against 4T1 and MDA-MB-231, enhanced five times the breast cancer cell uptake and three times the selectivity when compared to normal cells. Systemic toxicity assessment in mice revealed no concerning hematological or biochemical changes. Finally, in a 4T1 breast tumor model, NE-F-LapA significantly inhibited growth by 50% of the subcutaneous 4T1 tumor and reduced lung metastases 5-fold versus control. Overall, tailored nanoemulsification of the lapachol derivative enabled effective intravenous administration and improved efficacy over the free drug, indicating promise for enhanced breast cancer therapy pending further optimization.

Tocotrienols-enriched Self-nanoemulsifying Drug Delivery System Enhances the Antileukemic Activity of All-trans Retinoic Acid but not Electrocardiogram Alterations Evoked by Its Combination with Arsenic Trioxide.

All-trans retinoic acid and arsenic trioxide are the leading choices for the treatment of acute promyelocytic leukemia. Notwithstanding the impressive differentiative properties of all-trans retinoic acid and the apoptotic properties of arsenic trioxide, some problems still occur in acute promyelocytic leukemia treatment. These problems are due to patients' relapses, mainly related to changes in the ligand-binding domain of RARα (retinoic acid receptor α) and the cardiotoxic effects caused by arsenic trioxide. We previously developed a self-nanoemulsifying drug delivery system enriched with tocotrienols to deliver all-trans retinoic acid (SNEDDS-TRF-ATRA). Herein, we have evaluated if tocotrienols can help revert ATRA resistance in an APL cell line (NB4-R2 compared to sensitive NB4 cells) and mitigate the cardiotoxic effects of arsenic trioxide in a murine model. SNEDDS-TRF-ATRA enhanced all-trans retinoic acid cytotoxicity in NB4-R2 (resistant) cells but not in NB4 (sensitive) cells. Moreover, SNEDDS-TRF-ATRA did not significantly change the differentiative properties of all-trans retinoic acid in both NB4 and NB4-R2 cells. Combined administration of SNEDDS-TRF-ATRA and arsenic trioxide could revert QTc interval prolongation caused by ATO but evoked other electrocardiogram alterations in mice, such as T wave flattening. Therefore, SNEDDS-TRF-ATRA may enhance the antileukemic properties of all-trans retinoic acid but may influence ECG changes caused by arsenic trioxide administration. SNEDDS-TRF-ATRA presents cytotoxicity in resistant APL cells (NB4-R2). Combined administration of ATO and SNEDDS-TRF-ATRA in mice prevented the prolongation of the QTc interval caused by ATO but evoked ECG abnormalities such as T wave flattening.

A new oral self-emulsifying drug delivery system improves the antileishmania efficacy of fexinidazole in vivo.

The aim of this study was to develop, characterize and evaluate the in vivo oral efficacy of self-emulsifying drug delivery systems (SEDDS) containing fexinidazole (FEX) in the experimental treatment of visceral leishmaniasis (VL). The developed FEX-SEDDS formulation presented as a clear, yellowish liquid, with absence of precipitate. The droplet size, polydispersion index and zeta potential after dilution in water (1:200) was of 91 ± 3 nm, 0.242 ± 0.005 and -16.7 ± 0.2, respectively. In the simulated gastric and intestinal media, the FEX-SEDDS had a size of 97 ± 1 and 106 ± 9 nm, respectively. The FEX retention in droplet after SEDDS dilution in simulated gastrointestinal media was almost 100 %. Antileishmanial efficacy studies showed that FEX-SEDDS was the only treatment able to significantly (p < 0.05) reduce the parasite burden in the liver and spleen of animals experimentally infected with Leishmania infantum. Our intestinal permeability data suggest that FEX-SEDDS showed no evidence of injury to the intestinal mucosa. These findings suggest that FEX-SEDDS can be a promising oral alternative for the treatment of VL caused by L. infantum.

pH-sensitive doxorubicin-tocopherol succinate prodrug encapsulated in docosahexaenoic acid-based nanostructured lipid carriers: An effective strategy to improve pharmacokinetics and reduce toxic effects.

Side effects often limit the use of doxorubicin (DOX) in cancer treatment. We have recently developed a nanostructured lipid carrier (NLC) formulation for synergistic chemotherapy, encapsulating DOX and the anticancer adjuvants docosahexaenoic acid (DHA) and α-tocopherol succinate (TS). Hydrophobic ion-pairing with TS allowed a high DOX entrapment in the nanocarrier. In this work, we investigated the pharmacokinetics of this formulation after intravenous administration in mice. The first data obtained led us to propose synthesizing covalent DOX-TS conjugates to increase DOX retention in the NLC. We successfully conjugated DOX to TS via an amide or hydrazone bond. In vitro studies in 4T1 tumor cells indicated low cytotoxicity of the amide derivative, while the hydrazone conjugate was effective in killing cancer cells. We encapsulated the hydrazone derivative in a DHA-based nanocarrier (DOX-hyd-TS/NLC), which had reduced particle size and high drug encapsulation efficiency. The pH-sensitive hydrazone bond allowed controlled DOX release from the NLC, with increased drug release at acidic conditions. In vivo studies revealed that DOX-hyd-TS/NLC had a better pharmacokinetic profile than free DOX and attenuated the short-term cardiotoxic effects caused by DOX, such as QT prolongation and impaired left ventricular systolic function. Moreover, this formulation showed excellent therapeutic performance by reducing tumor growth in 4T1 tumor-bearing mice and decreasing DOX-induced toxicity to the heart and liver, demonstrated by hematologic, biochemical, and histologic analyses. These results indicate that DOX-hyd-TS/NLC may be a promising nanocarrier for breast cancer treatment.

Recent progress in micro and nano-encapsulation of bioactive derivatives of the Brazilian genus Pterodon.

In the last few decades, utilization of medicinal plants by the pharmaceutical industry has led to the identification of many new bioactive compounds. The genus Pterodon, native of the Brazilian Flora, is known for the therapeutic properties attributed to its species, which are widely used in popular medicine for their anti-inflammatory, anti-rheumatic, tonic, and depurative properties. The intrinsic low water solubility of the plant derivatives from the genus, including diterpenes with vouacapane skeletons that are partially associated with the pharmacological activities, impairs the bioavailability of these bioactive compounds. Recent studies have aimed to encapsulate Pterodon products to improve their water solubility, achieve stability, increase their efficacy, and allow clinical applications. The purpose of this paper is to review recent research on the use of nanotechnology for the development of new products from plant derivatives of the Pterodon genus in different types of micro- and nanocarriers. Therapeutic properties of their different products are also presented. Finally, an update about the current and future applications of encapsulated formulations is provided.

Nanomedicine in Oncocardiology: Contribution and Perspectives of Preclinical Studies.

Cancer and cardiovascular diseases are the leading causes of death and morbidity worldwide. Strikingly, cardiovascular disorders are more common and more severe in cancer patients than in the general population, increasing incidence rates. In this context, it is vital to consider the anticancer efficacy of a treatment and the devastating heart complications it could potentially cause. Oncocardiology has emerged as a promising medical and scientific field addressing these aspects from different angles. Interestingly, nanomedicine appears to have great promise in reducing the cardiotoxicity of anticancer drugs, maintaining or even enhancing their efficacy. Several studies have shown the benefits of nanocarriers, although with some flaws when considering the concept of oncocardiology. Herein, we discuss how preclinical studies should be designed as closely as possible to clinical protocols, considering various parameters intrinsic to the animal models used and the experimental protocols. The sex and age of the animals, the size and location of the tumors, the doses of the nanoformulations administered, and the acute vs. the long-term effects of treatments are essential aspects. We also discuss the perspectives offered by non-invasive imaging techniques to simultaneously assess both the anticancer effects of treatment and its potential impact on the heart. The overall objective is to accelerate the development and validation of nanoformulations through high-quality preclinical studies reproducing the clinical conditions.

All-trans retinoic acid in anticancer therapy: how nanotechnology can enhance its efficacy and resolve its drawbacks.

Introduction: All-trans retinoic acid (ATRA, tretinoin) is the main drug used in the treatment of acute promyelocytic leukemia (APL). Despite its impressive activity against APL, the same could not be clinically observed in other types of cancer. Nanotechnology can be a tool to enhance ATRA anticancer efficacy and resolve its drawbacks in APL as well as in other malignancies.Areas covered: This review covers ATRA use in APL and non-APL cancers, the problems that were found in ATRA therapy and how nanoencapsulation can aid to circumvent them. Pre-clinical results obtained with nanoencapsulated ATRA are shown as well as the two ATRA products based on nanotechnology that were clinically tested: ATRA-IV® and Apealea®.Expert opinion: ATRA presents interesting properties to be used in anticancer therapy with a notorious differentiation and antimetastatic activity. Bioavailability and resistance limitations impair the use of ATRA in non-APL cancers. Nanotechnology can circumvent these issues and provide tools to enhance its anticancer activities, such as co-loading of multiple drug and active targeting to tumor site.

Enhanced antitumor efficacy of lapachol-loaded nanoemulsion in breast cancer tumor model.

Lapachol (LAP) is a natural compound with various biological properties, including anticancer activity. However, its clinical application is limited due to the low aqueous solubility and potential adverse side effects. Nanoemulsions are drug delivery systems that can assist in the administration of hydrophobic drugs, increasing their bioavailability and protecting from degradation. Thus, this study aimed to prepare a LAP-loaded nanoemulsion (NE-LAP), and evaluate its antitumor activity. For this purpose, the nanoemulsion was prepared using a hot homogenization method and characterized morphologically by cryogenic transmission electron microscopy (cryo-TEM). Mean diameter, polydispersity index, and zeta potential was evaluated by DLS, encapsulation efficiency was measured by HPLC. Moreover, the short-term storage stability, the drug release and hemolysis in vitro was determined. Additionally, pharmacokinetic, toxicology and toxicity properties of99mTc-NE-LAP were evaluated in a breast cancer (4T1) tumor model. The cryo-TEM showed spherical globules, and the physicochemical characterization of NE-LAP showed a homogeneous stable nanoemulsion with a mean diameter of ∼170 nm, zeta potential of around -20 mV, and encapsulation greater than 85 %. In vitro studies validated that encapsulation did not impair the cytotoxicity activity of LAP. The nanoemulsion was successfully radiolabeled and 99mTc-NE-LAP showed prolonged blood circulation and tumor affinity was confirmed by tumor-to-muscle ratio. Moreover, NE-LAP showed higher antitumor activity than the free drug and the treatment did not result in any signs of toxicity. Therefore, these findings suggest that NE-LAP can be considered an effective strategy for cancer treatment.

Nanostructured lipid carriers as a novel tool to deliver sclareol: physicochemical characterisation and evaluation in human cancer cell lines

Sclareol (SC) is arousing great interest due to its cytostatic and cytotoxic activities in several cancer cell lines. However, its hydrophobicity is a limiting factor for its in vivo administration. One way to solve this problem is through nanoencapsulation. Therefore, solid lipid nanoparticles (SLN-SC) and nanostructured lipid carriers (NLC-SC) loaded with SC were produced and compared regarding their physicochemical properties. NLC-SC showed better SC encapsulation than SLN-SC and was chosen to be compared with free SC in human cancer cell lines (MDA-MB-231 and HCT-116). Free SC had slightly higher cytotoxicity than NLC-SC and produced subdiploid DNA content in both cell lines. On the other hand, NLC-SC led to subdiploid content in MDA-MB-231 cells and G2/M checkpoint arrest in HCT-116 cells. These findings suggest that SC encapsulation in NLC is a way to allow the in vivo administration of SC and might alter its biological properties

Sclareol is a potent enhancer of doxorubicin: Evaluation of the free combination and co-loaded nanostructured lipid carriers against breast cancer.

AIMS: In this work, it was sought to determine if there was synergism between doxorubicin (DOX), a well-known antineoplastic, and sclareol (SC), a diterpene from natural origin, in breast cancer treatment. Moreover, it was investigated if their co-loading in the same nanocarrier would result in a gain of activity and/or a toxicity diminishment. MAIN METHODS: The synergism of the DOX:SC combination was evaluated in MDA-MB-231 and 4T1 cells. A nanostructured lipid carrier (NLC) co-encapsulating DOX and SC in their synergistic molar ratio was prepared and characterised, in terms of mean diameter, zeta potential, DOX encapsulation efficiency, small angle X-ray scattering, differential scanning calorimetry, and polarised light microscopy for further intravenous administration. The anticancer activity of the combination, free and encapsulated, was evaluated in 4T1-tumour bearing mice. KEY FINDINGS: It was determined that DOX:SC combination at the molar ratio 1:1.9 presents better synergistic anticancer activity than the molar ratio 1:7.5 in vitro. DOX:SC-loaded NLC (NLC-DOX-SC) improved in vitro cytotoxic and in vivo antitumour activity compared to free DOX. Although NLC-DOX-SC and free DOX:SC, at the synergistic molar ratio, showed similar activity in the in vivo study, the free combination provoked body weight loss, behaviour alterations and haematological toxicity in the animals, while this was not observed for NLC-DOX-SC. SIGNIFICANCE: This work shows that SC and DOX present synergistic anticancer activity for breast cancer treatment whereas NLC-DOX-SC was a feasible alternative to attain the benefits posed by DOX:SC combination but with none to fewer side effects.

Nanoencapsulated retinoic acid as a safe tolerogenic adjuvant for intranasal vaccination against cutaneous leishmaniasis.

Mucosal, but not peripheral, vaccination with whole Leishmania amazonensis antigen (LaAg) effectively protects mice against leishmaniasis, likely through a tolerogenic mechanism. Given the crucial role of retinoic acid (RA) in CD4+ Foxp3+ regulatory T cell (Treg) differentiation and mucosal tolerance, here we evaluated the capacity of RA to improve intranasal (i.n.) vaccination with LaAg. To prevent degradation and possible mucosa irritation, RA was encapsulated in solid lipid nanoparticles (RA-SLN). Thus, BALB/c mice were given two i.n. doses of LaAg alone or in association with RA-SLN (LaAg/RA-SLN) prior to challenge with L. amazonensis. No histological sign of irritation or inflammation was produced in the nasal mucosa after RA-SLN administration. LaAg/RA-SLN vaccine was more effective in delaying lesion growth and reducing parasite burdens than LaAg alone (96% and 61% reduction, respectively). At two months after challenge, both vaccinated groups displayed similar T helper (Th) 1-skewed in situ cytokine responses, different from early infection where both Th1 and Th2 responses were suppressed, except for transforming growth factor (TGF)-ß mRNA, that was higher in mice given RA-SLN. At the mucosa, RA-SLN promoted enhanced expression of interleukin (IL)-10 and CD4+ Foxp3+ Treg population. In sum, these data show that RA-SLN is an effective and safe tolerogenic adjuvant for i.n. vaccination against leishmaniasis.

Sclareol-loaded lipid nanoparticles improved metabolic profile in obese mice.

Sclareol is a bioactive hydrophobic diterpene in the essential oil isolated from Salvia sclarea (Fam. Lamiaceae). Sclareol has been widely studied due to its anti-inflammatory and antioxidant effects. AIMS: The present study aimed to evaluate the effects of Sclareol in different formulations (solid lipid nanoparticle and free) on the metabolic profile of obese mice. MAIN METHODS: Swiss male mice were randomly divided into two groups: standard diet (STD) and high-fat diet (HFD). After obesity induction, each group was divided into three treatment groups: free Sclareol (Sc), Sclareol-loaded lipid nanoparticle (L-Sc) and blank lipid nanoparticle (L). Treatments were performed every day during 30 days. KEY FINDINGS: L-Sc improves obese mice metabolic profile by decreasing adiposity, ameliorating insulin sensitivity, glucose tolerance and increasing the HDL plasma levels. In addition, L-Sc decreased the expression of NF-KB, MCP-1 and SERBP-1. SIGNIFICANCE: The use of sclareol together with lipid nanocarriers may be promising for the treatment of metabolic disorders by reducing adipose tissue.

Improved Cytotoxic Effect of Doxorubicin by Its Combination with Sclareol in Solid Lipid Nanoparticle Suspension.

This work aims to develop, characterize, and evaluate the anticancer activity of solid lipid nanoparticles (SLN) containing doxorubicin (DOX), an antitumoral from the antracycline class, and sclareol (SC), a lipophilic labdene diterpene (SLN-DOX-SC). The SLN were characterized by Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Small Angle X-ray Diffraction (SAXS), in vitro release, transmission electron microscopy, and polarized light microscopy. Evaluation of cell viability was performed in two cell cultures: MCF-7 (human breast cancer) and 4T1 (murine breast cancer). The SLN showed a size in the range of 128 nm, negative zeta potential, DOX encapsulation efficiency (EE) of 99%, and drug loading (DL) of 66 mg/g. Characterization of the formulation by DSC, XRD, and SAXS revealed the presence of DOX inside the nanoparticles of SLN and suggested increased expulsion/release of this drug when associated with SC. The release profiles revealed that the SLN-DOX-SC showed controlled release of DOX at pH 7.4 with enhanced drug release at low pH, useful for cancer treatment. The SLN-DOX-SC demonstrated to be more effective than the free DOX against 4T1 cells. So, the developed SLN efficiently encapsulate DOX and SC and show good potential as an alternative for cancer treatment.

A new nanoemulsion formulation improves antileishmanial activity and reduces toxicity of amphotericin B.

This work aimed to optimise a new nanoemulsion (NE) formulation loaded with Amphotericin B (AmB) and to evaluate its in vivo antileishmanial activity and in vitro haemolytic toxicity. The influence of gradual increases in pressure, using a high-pressure homogeniser, was evaluated. The NE was characterised for droplet size, polydispersity index, zeta potential and encapsulation efficiency (EE). For antileishmanial activity studies, AmB-NE was administered intravenously in mice infected by Leishmania infantum chagasi, which causes Visceral Leishmaniasis (VL). When the NE was submitted to gradual increases in pressure, the PI values and droplet size decreased. The droplet size (∼145 nm) was lower than that obtained in previous studies. The zeta potential was negative and the EE was almost 100%. The haemolytic toxicity, evaluated on human red blood cells, for AmB-loaded NE was lower than that observed for the conventional AmB (C-AmB). C-AmB at 2 mg/kg was very toxic. In contrast, administration of the AmB-loaded NE, at same dose, did not result in any sign of acute toxicity, promoting a significant reduction in parasite burden as compared to the C-AmB. These findings suggest that this new AmB-loaded NE constitutes an attractive alternative for the treatment of VL due to improved efficacy and lower toxicity.

Hyaluronic acid-coated nanoemulsions loaded with a hydrophobic ion pair of all-trans retinoic acid for improving the anticancer activity

All-trans retinoic acid (ATRA) has been studied for the treatment of cancer, including leukemia and breast cancer. This work aims to develop nanoemulsions (NE) loaded with a hydrophobic ion pair (HIP) of all-trans retinoic acid (ATRA) and a lipophilic amine, stearylamine (SA), and coated with hyaluronic acid (HA) to enhance anticancer activity and reducing toxicity. Blank NE was prepared by spontaneous emulsification and optimized prior to HIP incorporation. NE-ATRA was electrostatically coated with different concentrations of HA. Incorporation of ATRA-SA led to monodisperse NE with small size (129 ± 2 nm; IP 0.18 ± 0.005) and positive zeta potential (35.7 ± 1.0 mV). After coating with 0.5 mg/mL HA solution, the mean diameter slightly increased to 158 ± 5 nm and zeta potential became negative (-19.7 ± 1.2 mV). As expected, high encapsulation efficiency (near 100%) was obtained, confirmed by polarized light microscopy and infrared analysis. Formulations remained stable over 60 days and release of ATRA from NE was delayed after the hydrophilic HA-coating. HA-coated NE-ATRA was more cytotoxic than free ATRA for MDA-MB-231 and MCF-7 breast cancer cell lines, especially in the CD44 overexpressing cells. Blank coated formulations showed no cytotoxicity. These findings suggest that this easily-made HA-coated NE-ATRA formulation is a promising alternative for parenteral administration, thus improving the breast cancer therapy with this drug.

Hydrophobic ion pairing as a strategy to improve drug encapsulation into lipid nanocarriers for the cancer treatment.

INTRODUCTION: Incorporation of anticancer drugs with low lipophilicity in lipid nanocarriers is usually low, which limits the utilization of this strategy in cancer therapy. However, the complexation of these drugs with lipophilic ion pairs containing ionizable groups has been reported to improve their incorporation in nanocarriers such as solid lipid nanoparticles (SLNs), nanostructured lipid nanocarriers (NLCs), and nanoemulsions (NEs). Therefore, those nanocarriers have shown an increase in efficacy and lower toxicity compared with the free drugs, particularly if the counter ion utilized has anticancer activity. Areas covered: This review covers, from 1999 to the present, the utilization of the hydrophobic ion pair (HIP) approach to enhance the encapsulation of anticancer drugs in lipid nanostructured delivery systems, SLN, NLC, and NE; the benefits achieved; and challenges to improve the anticancer therapy. Expert opinion: The HIP strategy has consistently demonstrated enhancement of the encapsulation efficiency in NLCs associated with increased anticancer activity of drugs such as doxorubicin, all-trans retinoic acid, methotrexate, vincristine and others. From this point on, conducting further physicochemical characterization studies of the formed ion pair as well as proceeding with the in vivo efficacy, toxicity and pharmacokinetics studies are expected.

Development of a bone-targeted pH-sensitive liposomal formulation containing doxorubicin: physicochemical characterization, cytotoxicity, and biodistribution evaluation in a mouse model of bone metastasis.

BACKGROUND: Despite recent advances in cancer therapy, the treatment of bone tumors remains a major challenge. A possible underlying hypothesis, limitation, and unmet need may be the inability of therapeutics to penetrate into dense bone mineral, which can lead to poor efficacy and high toxicity, due to drug uptake in healthy organs. The development of nanostructured formulations with high affinity for bone could be an interesting approach to overcome these challenges. PURPOSE: To develop a liposomal formulation with high affinity for hydroxyapatite and the ability to release doxorubicin (DOX) in an acidic environment for future application as a tool for treatment of bone metastases. MATERIALS AND METHODS: Liposomes were prepared by thin-film lipid hydration, followed by extrusion and the sulfate gradient-encapsulation method. Liposomes were characterized by average diameter, ζ-potential, encapsulation percentage, X-ray diffraction, and differential scanning calorimetry. Release studies in buffer (pH 7.4 or 5), plasma, and serum, as well as hydroxyapatite-affinity in vitro analysis were performed. Cytotoxicity was evaluated by MTT assay against the MDA-MB-231 cell line, and biodistribution was assessed in bone metastasis-bearing animals. RESULTS: Liposomes presented suitable diameter (~170 nm), DOX encapsulation (~2 mg/mL), controlled release, and good plasma and serum stability. The existence of interactions between DOX and the lipid bilayer was proved through differential scanning calorimetry and small-angle X-ray scattering. DOX release was faster when the pH was in the range of a tumor than at physiological pH. The bone-targeted formulation showed a strong affinity for hydroxyapatite. The encapsulation of DOX did not interfere in its intrinsic cytotoxicity against the MDA-MB-231 cell line. Biodistribution studies demonstrated high affinity of this formulation for tumors and reduction of uptake in the heart. CONCLUSION: These results suggest that bone-targeted pH-sensitive liposomes containing DOX can be an interesting strategy for selectively delivering this drug into bone-tumor sites, increasing its activity, and reducing DOX-related toxicity.

Improved In Vitro Antileukemic Activity of All-Trans Retinoic Acid Loaded in Cholesteryl Butyrate Solid Lipid Nanoparticles.

All-trans retinoic acid, a hydrophobic drug, has become one of the most successful examples of differentiation agents used for treatment of acute promyelocytic leukemia. On the other hand, histone deacetylase inhibitors, such as cholesteryl butyrate, present differentiating activity and.can potentiate action of drugs such as all-trans retinoic acid. Solid lipid nanoparticles represent a promising alternative for administration of hydrophobic drugs such as ATRA. This study aimed to develop, characterize, and evaluate the cytotoxicity of all-trans retinoic acid-loaded solid lipid nanoparticles for leukemia treatment. The influence of in situ formation of an ion pairing between all-trans retinoic acid and lipophilic amines on the characteristics of the particles (size, zeta potential, encapsulation efficiency) was evaluated. Cholesteryl butyrate, a butyric acid donor, was used as a component of the lipid matrix. In vitro activity on cell viability and distribution of cell cycle phases were evaluated for HL-60, Jurkat, and THP-1 cell lines. The encapsulation efficiency of all-trans retinoic acid in cholesteryl butyrate-solid lipid nanoparticles was significantly increased by the presence of the amine. Inhibition of cell viability by all-trans retinoic acid-loaded solid lipid nanoparticles was more pronounced than the free drug. Analysis of the distribution of cell cycle phases also showed increased activity for all-trans retinoic acid-loaded cholesteryl butyrate-solid lipid nanoparticles, with a clear increase in subdiploid DNA content. The ion pair formation in SLN containing cholesteryl butyrate can be explored as a simple and inexpensive strategy to improve the efficacy and bioavail-ability of ATRA in the treatment of the cancer and metabolic diseases in which this retinoid plays an important role.

Evaluation of Antitumor Activity of Long-Circulating and pH-Sensitive Liposomes Containing Ursolic Acid in Animal Models of Breast Tumor and Gliosarcoma.

Background Ursolic acid (UA) is a triterpene found in different plant species, possessing antitumor activity, which may be a result of its antiangiogenic effect. However, UA has low water solubility, which limits its use because the bioavailability is impaired. To overcome this inconvenience, we developed long-circulating and pH-sensitive liposomes containing ursolic acid (SpHL-UA). We investigated the antiangiogenic effect of free UA and SpHL-UA in murine brain cancer and human breast tumor models by means of determination of the relative tumor volume, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and histopathological analysis. Methods The animals were treated with dimethyl sulfoxide in 0.9% (w/v) NaCl, free UA, long-circulating and pH-sensitive liposomes without drug (SpHL), or SpHL-UA. The animals were submitted to each treatment by intraperitoneal injection for 5 days. The dose of free UA or SpHL-UA was equal to 23 mg/kg. Results Tumor growth inhibition was not observed in human breast tumor-bearing animals. For murine gliosarcoma-bearing animals, a slight tumor growth inhibition was observed in the groups treated with free UA or SpHL-UA (9% and 15%, respectively). No significant change in any of the parameters evaluated by DCE-MRI for both experimental models could be observed. Nevertheless, the evaluation of the mean values of magnetic resonance parameters of human breast tumor-bearing animals showed evidence of a possible antiangiogenic effect induced by SpHL-UA. Histopathological analysis did not present significant change for any treatment. Conclusion SpHL-UA did not show antiangiogenic activity in a gliosarcoma model and seemed to induce an antiangiogenic effect in the human breast tumor model.