Paclitaxel-Loaded Folate-Coated pH-Sensitive Liposomes Enhance Cellular Uptake and Antitumor Activity.

Paclitaxel (PTX) is a microtubule-stabilizing agent widely used to treat breast cancer. Nevertheless, the low solubility of the drug and the side effects of commercial formulations available limit its clinical use. In this way, our group recently described the preparation of PTX-loaded folate-coated long-circulating and pH-sensitive liposomes (SpHL-folate-PTX). Therefore, a proof-of-concept study was designed in order to demonstrate the feasibility of SpHL-folate-PTX against breast tumor cell line MDA-MB-231. Cellular uptake of the liposomes and PTX was evaluated. Apoptosis and cell cycle were analyzed by flow cytometry. In vivo antitumor activity was carried out in MDA-MB-231 tumor-bearing BALB/c nude mice. Cellular uptake assay showed a high cell delivery of PTX by SpHL-folate-PTX, which leads to superior cytotoxicity and activation of apoptosis pathways. The SpHL-folate-PTX treatment induces an expressive increase of cells in the G0/G1 phase compared to free PTX and SpHL-PTX (without folate). In vivo studies showed a significant reduction in the tumor growth and a lower uptake of a radiopharmaceutical in the scintigraphic images for the SpHL-folate-PTX group, suggesting its higher efficacy compared with free PTX and SpHL-PTX. Histomorphometric analyses demonstrated an increase in necrosis and inflammation areas in animals treated with SpHL-folate-PTX. A decrease in the proliferative cells and a higher percentage of apoptotic cells were observed by immunohistochemical analyses after the treatment with SpHL-folate-PTX. Therefore, the data confirmed the potential of SpHL-folate-PTX as an alternative antitumor therapy, especially for breast cancer.

Toxicological study of a new doxorubicin-loaded pH-sensitive liposome: A preclinical approach.

Doxorubicin (DOX) is widely used in cancer treatment, however, the use of this drug is often limited due to its cardiotoxic side effects. In order to avoid these adverse effects, the encapsulation of DOX into nanosystems has been used in the last decades. In this context, pH-sensitive liposomes have been shown promising for delivering cytotoxic agents into tumor cells, however, the lack of information about in vivo toxicity of this nanocarrier has impaired translational studies. Therefore, the aim of this work was to investigate the acute toxicity and cardiotoxicity of DOX-loading pH-sensitive liposomes (SpHL-DOX). To achieve this, female BALB/c mice, after intravenous administration, were monitored by means of clinical, laboratory, histopathological and electrocardiographic (ECG) analyses. Results indicate that SpHL was able to prevent renal toxicity and the hepatic injury was less extensive than free DOX. In addition, lower body weight loss was associated with less ECG QT interval prolongation to animals receiving SpHL-DOX (14.6 ±â€¯5.2%) compared to animals receiving free DOX (35.7 ±â€¯4.0%) or non-pH-sensitive liposomes (nSpHL-DOX) (47.0 ±â€¯9.8%). These results corroborate with SpHL-DOX biodistribution studies published by our group. In conclusion, the SpHL-DOX showed less toxic effects on mice compared to free DOX or nSpHL-DOX indicating that SpHL-DOX is a promising strategy to reduce the serious cardiotoxic effects of DOX.

Antitumor effectiveness of a combined therapy with a new cucurbitacin B derivative and paclitaxel on a human lung cancer xenograft model.

Non-small cell lung cancer (NSCLC) is one of the most common malignant tumors, with a high mortality rate due to the elevated risk of resistance. Natural cucurbitacins and their derivatives are recognized as promising antitumor compounds for several types of cancer, including NSCLC. In a recent study published by our research group, DACE (2-deoxy-2-amine-cucurbitacin E), which is a semisynthetic derivative of cucurbitacin B, showed potential in vitro synergistic antiproliferative effects combined with paclitaxel (PTX) in A549 cells. In sequence, the purpose of this study was to evaluate the in vivo antitumor efficacy of this combined therapy as well as with these drugs individually, using a human NSCLC xenograft model. Some indicators of sub chronic toxicity that could be affected by treatments were also assessed. The results obtained in vivo with the combined treatment (1mg/kg+PTX 10mg/kg) showed the most effective reduction of the relative tumor volume and the highest inhibition of tumor growth and proliferation, when compared with those of the single treatments. Furthermore, scintigraphic images, obtained before and after the treatments, showed that the most effective protocol able to reduce the residual viable tumor mass was the combined treatment. All treatment regimens were well tolerated without significant changes in body weight and no histological and functional damage to liver and kidney tissues. These results corroborate our previous in vitro synergistic effects published. Taken together, these insights are novel and highlight the therapeutic potential of DACE and PTX combination scheme for NSCLC.

Evaluation of antitumor activity and cardiac toxicity of a bone-targeted ph-sensitive liposomal formulation in a bone metastasis tumor model in mice.

Chemotherapy for bone tumors is a major challenge because of the inability of therapeutics to penetrate dense bone mineral. We hypothesize that a nanostructured formulation with high affinity for bone could deliver drug to the tumor while minimizing off-target toxicity. Here, we evaluated the efficacy and toxicity of a novel bone-targeted, pH-sensitive liposomal formulation containing doxorubicin in an animal model of bone metastasis. Biodistribution studies with the liposome showed good uptake in tumor, but low accumulation of doxorubicin in the heart. Mice treated with the bone-targeted liposome formulation showed a 70% reduction in tumor volume, compared to 35% reduction for free doxorubicin at the same dose. Both cardiac toxicity and overall mortality were significantly lower for animals treated with the bone-targeted liposomes compared to free drug. Bone-targeted, pH-sensitive, doxorubicin containing liposomes represent a promising approach to selectively delivering doxorubicin to bone tumors while minimizing cardiac toxicity.

Long-Circulating and pH-Sensitive Liposome Preparation Trapping a Radiotracer for Inflammation Site Detection.

Inflammatory and infectious diseases are one of the most common causes of mortality and morbidity. This paper aimed to prepare and to evaluate the ability of long-circulating and pH-sensitive liposomes, trapping a radiotracer, to identify inflamed focus. The physicochemical characterization of freeze-dried liposomes, using glucose as cryoprotectant, showed 80% of the vesicles with adequate mean diameter and good vesicle size homogeneity. Radiotracer encapsulation percentage in liposomes was 10.65%, of which 4.88% was adsorbed on the surface of the vesicles. Furthermore, liposomes presented positive zeta potential. Freeze-dried liposomes, stored for 180 days at 4 degrees C, did not show significant changes in the mean diameter, indicating good stability. Free radiotracer and radiolabeled liposomes were injected into inflammation focus-bearing rats, and ex-vivo biodistribution studies and scintigraphic images were performed. Results showed that radiopharmaceutical, free and encapsulated into liposomes, were able to identify the inflamed site. Target/non-target ratios, obtained by scintigraphic images, were greater than 1.5 at all investigated times. Data did not show significant differences between the free radiotracer and radiolabeled liposomes. Results suggest that this liposomal preparation could be employed as an alternative procedure for inflamed site detection by means of scintigraphic images. However, as the radiotracer is adsorbed onto the liposome surface by electrostatic forces, it is suggested that a neutral radiopharmaceutical be used to confirm the potential of this formulation as a scintigraphic probe for inflammation/infection detection.

Venoms, toxins and derivatives from the Brazilian fauna: valuable sources for drug discovery.

Animal venoms have been widely investigated throughout the world. The great number of biotechnological articles as well as patent applications in the field of drug discovery based on these compounds indicates how important the source is. This review presents a list of the most studied Brazilian venomous animal species and shows the most recent patent applications filed from 2000 to 2013, which comprise Brazilian venoms, toxins and derivatives. We analyze the data according to the species, the type of products claimed and the nationality of the inventors. Fifty-five patent applications were found, involving 8 genera. Crotalus, Lachesis, Bothrops and Loxosceles represented 78% of the patent applications. The other 22% were represented by Phoneutria, Tityus, Acanthoscurria and Phyllomedusa. Most of the inventions (42%) involved anticancer, immunomodulator or antimicrobial drugs, while 13% involved anti-venoms and vaccines, 11% involved hypotensive compositions, 9% involved antinociceptive and/or anti-inflammatory compositions, and the other 25% involved methods, kits or compositions for various purposes. Brazilian inventors filed 49% of the patent applications, but other countries, mainly the United States of America, Germany, Russia and France, also filed patent applications claiming products comprising venoms, toxins and/or derivatives from the Brazilian fauna. Brazil holds an important number of patent applications which mostly belong to universities and research institutes, but the pharmaceutical industry in this field is still weak in Brazil. Although, Brazilian venomous animal species have been reported in drug discovery throughout the world, many species remain to be explored as valuable and promising tools for drug discovery and development.

Combination of the Topical Photodynamic Therapy of Chloroaluminum Phthalocyanine Liposomes with Fexinidazole Oral Self-Emulsifying System as a New Strategy for Cutaneous Leishmaniasis Treatment.

Cutaneous leishmaniasis (CL) is a neglected tropical disease. The treatment is restricted to drugs, such as meglumine antimoniate and amphotericin B, that exhibit toxic effects, high cost, long-term treatment, and limited efficacy. The development of new alternative therapies, including the identification of effective drugs for the topical and oral treatment of CL, is of great interest. In this sense, a combination of topical photodynamic therapy (PDT) with chloroaluminum phthalocyanine liposomes (Lip-ClAlPc) and the oral administration of a self-emulsifying drug delivery system containing fexinidazole (SEDDS-FEX) emerges as a new strategy. The aim of the present study was to prepare, characterize, and evaluate the efficacy of combined therapy with Lip-ClAlPc and SEDDS-FEX in the experimental treatment of Leishmania (Leishmania) major. Lip-ClAlPc and SEDDS-FEX were prepared, and the antileishmanial efficacy study was conducted with the following groups: 1. Lip-ClAlPc (0.05 mL); 2. SEDDS-FEX (50 mg/kg/day); 3. Lip-ClAlPc (0.05 mL)+SEDDS-FEX (50 mg/kg/day) combination; 4. FEX suspension (50 mg/kg/day); and 5. control (untreated). BALB/c mice received 10 sessions of topical Lip-ClAlPc on alternate days and 20 consecutive days of SEDDS-FEX or FEX oral suspension. Therapeutical efficacy was evaluated via the parasite burden (limiting-dilution assay), lesion size (mm), healing of the lesion, and histological analyses. Lip-ClAlPc and SEDDS-FEX presented physicochemical characteristics that are compatible with the administration routes used in the treatments. Lip-ClAlPc+SEDDS-FEX led to a significant reduction in the parasitic burden in the lesion and spleen when compared to the control group (p < 0.05) and the complete healing of the lesion in 43% of animals. The Lip-ClAlPc+SEDDS-FEX combination may be promising for the treatment of CL caused by L. major.

Hybrid Nanosystem Formed by DOX-Loaded Liposomes and Extracellular Vesicles from MDA-MB-231 Is Effective against Breast Cancer Cells with Different Molecular Profiles.

Drug delivery selectivity is a challenge for cancer treatment. A hybrid pegylated pH-sensitive liposome-extracellular vesicle isolated from human breast cancer cell MDA-MB-231 was developed to investigate its in vitro activity against breast cancer cells of different molecular profiles to overcome this inconvenience. The hybrid nanosystem was produced by film hydration, and doxorubicin (DOX) was encapsulated in this system using the ammonium sulfate gradient method. The characterization of this hybrid nanosystem revealed a mean diameter of 140.20 ± 2.70 nm, a polydispersity index of 0.102 ± 0.033, an encapsulation efficiency of doxorubicin of 88.9% ± 2.4, and a great storage stability for 90 days at 4 °C. The fusion of extracellular vesicles with liposomes was confirmed by nanoflow cytometry using PE-conjugated human anti-CD63. This hybrid nanosystem demonstrated cytotoxicity against human breast cancer cell lines with different molecular subtypes, enhanced anti-migration properties, and exhibited similar cellular uptake to the free DOX treatment. Preliminary acute toxicity assessments using Balb/C female mice indicated a median lethal dose of 15-17.5 mg/kg, with no evidence of splenic, liver, heart, bone marrow, and renal damage at a dose of 15 mg/kg. These findings suggest the hybrid formulation as a versatile nanocarrier for the treatment of various breast cancer subtypes.

Investigation of alternative organic solvents and methods for the preparation of long-circulating and pH-sensitive liposomes containing cisplatin.

Recent studies using long-circulating and pH-sensitive liposomes containing cisplatin (SpHL-CDDP) have resulted in a formulation with improved pharmacokinetic, toxicity and tumor localization properties. In this study, SpHL-CDDP were prepared in both laboratory and pilot scales. This study evaluated the possibility of using the dehydration-rehydration method, as well as using alternative organic solvents (ethyl acetate/ethanol mixtures at 2:1 and 1:1 volume ratios), for the preparation of liposomes by the reverse-phase evaporation (REV) method. The influence of different concentrations of cisplatin (CDDP) (2.0, 1.0, 0.5 and 0.25 mg/mL) on the entrapment percentage and size of SpHL-CDDP was also investigated. In addition, carbohydrates were tested as cryoprotectants in a freeze-thaw study as a pretest to screen the type to be used in the freeze-drying process. A decrease in the encapsulation percentage of CDDP and an increase in the vesicle diameter could be observed for both liposome formulations prepared with ethyl acetate:ethanol mixtures, as compared with REV liposomes prepared with ethyl ether. It is important to note that after applying either quick or slow cooling, the mean diameter of SpHL (empty liposomes) proved to be similar when in the presence of cryoprotectants. In sum, the optimal processing conditions were achieved when using a 0.5 mg/mL CDDP solution, ethyl ether and the REV method, resulting in liposomal dispersions of mean diameters and homogeneities that were deemed suitable for intravenous administration.

Evaluation of acute toxicity and in vitro antitumor activity of a novel doxorubicin-loaded folate-coated pH-sensitive liposome.

Doxorubicin (DOX) loaded liposomes have been used and studied in the last decades due to the significant decrease in DOX induced cardiac and systemic toxicity relative to administration of free drug. Therefore, new strategies are sought to improve DOX delivery and antitumor activity, while avoiding side effects. Recently, folate-coated pH-sensitive liposomes (SpHL-Fol) have been studied as a tool to enhance cellular uptake and antitumor activity of paclitaxel and DOX in breast cancer cells expressing folate receptor (FR+). However, the elucidation of folate functionalization relevance in DOX-loaded SpHL (SpHL-DOX-Fol) in different cell types (MDA-MB-231, MCF-7, and A549), as well as, the complete safety evaluation, is necessary. To achieve these objectives, SpHL-DOX-Fol was prepared and characterized as previously described. Antitumor activity and acute toxicity were evaluated in vivo through direct comparison of free DOX verses SpHL-DOX, a well-known formulation to reduce DOX cardiotoxicity. The obtained data are crucial to support future translational research. Liposomes showed long-term stability, suitable for biological use. Cellular uptake, cytotoxicity, and percentage of migration inhibition were significantly higher for MDA-MB-231 (FR+) treated with SpHL-DOX-Fol. In addition, SpHL-DOX-Fol demonstrated a decrease in the systemic toxic effects of DOX, mainly in renal and cardiac parameters evaluation, even using a higher dose (20 mg/kg). Collectively these data build the foundation of support demonstrating that SpHL-DOX-Fol could be considered a promising drug delivery strategy for the treatment of FR+ breast tumors.

Technetium-99m-labeled ceftizoxime loaded long-circulating and pH-sensitive liposomes used to identify osteomyelitis.

Osteomyelitis is an infectious disease located in the bone or bone marrow. Long-circulating and pH-sensitive liposomes containing a technetium-99m-labeled antibiotic, ceftizoxime, (SpHL-(99m)Tc-CF) were developed to identify osteomyelitis foci. Biodistribution studies and scintigraphic images of bone infection or non infection-bearing rats that had been treated with these liposomes were performed. A high accumulation in infectious foci and high values in the target-non target ratio could be observed. These results indicate the potential of SpHL-(99m)Tc-CF as a potential agent for the diagnosis of bone infections.

Investigation of the Antitumor Activity and Toxicity of Tumor-Derived Exosomes Fused with Long-Circulating and pH-Sensitive Liposomes Containing Doxorubicin.

Exosome-liposome hybrid nanocarriers containing chemotherapeutic agents have been developed to enhance drug delivery, improve the efficacy of the treatment of metastatic cancer, and overcome chemoresistance in cancer therapy. Thus, the objectives of this study were to investigate the toxicological profiles of exosomes fused with long-circulating and pH-sensitive liposomes containing doxorubicin (ExoSpHL-DOX) in healthy mice and the antitumor activity of ExoSpHL-DOX in Balb/c female mice bearing 4T1 breast tumors. The acute toxicity was determined by evaluating the mortality and morbidity of the animals and conducting hematological, biochemical, and histopathological analyses after a single intravenous administration of ExoSpHL-DOX. The results of the study indicated that the ExoSpHL-DOX treatment is less toxic than the free doxorubicin (DOX) treatment. ExoSpHL-DOX showed no signs of nephrotoxicity, even at the highest dose of DOX, indicating that the hybrid nanosystem may alter the distribution of DOX and reduce the kidney damage. Regarding the antitumor activity, ExoSpHL-DOX showed an antitumor effect compared to the control group. Furthermore, the hybrid nanocarrier of tumor-derived exosomes fused with long-circulating and pH-sensitive liposomes reduced the number of metastatic foci in the lungs. These results indicate that ExoSpHL-DOX may be a promising nanocarrier for the treatment of breast cancer, reducing toxicity and inhibiting metastasis, mainly in the lungs.

PEGylated versus Non-PEGylated pH-Sensitive Liposomes: New Insights from a Comparative Antitumor Activity Study.

PEGylated liposomes are largely studied as long-circulating drug delivery systems. Nevertheless, the addition of PEG can result in reduced interactions between liposomes and cells, hindering liposomal internalization into target cells. The presence of PEG on the surface of pH-sensitive liposomes is not advantageous in terms of biodistribution and tumor uptake, raising the question of whether the indiscriminate use of PEG benefits the formulation. In this study, two doxorubicin-loaded pH-sensitive liposomal formulations, PEGylated (Lip2000-DOX) or non-PEGylated (Lip-DOX), were prepared and characterized. Overall, the PEGylated and non-PEGylated liposomes showed no differences in size or morphology in Cryo-TEM image analysis. Specifically, DLS analysis showed a mean diameter of 140 nm, PDI lower than 0.2, and zeta potential close to neutrality. Both formulations showed an EP higher than 90%. With respect to drug delivery, Lip-DOX had better cellular uptake than Lip2000-DOX, suggesting that the presence of PEG reduced the amount of intracellular DOX accumulation. The antitumor activities of free-DOX and both liposomal formulations were evaluated in 4T1 breast tumor-bearing BALB/c mice. The results showed that Lip-DOX was more effective in controlling tumor growth than other groups, inhibiting tumor growth by 60.4%. Histological lung analysis confirmed that none of the animals in the Lip-DOX group had metastatic foci. These results support that pH-sensitive liposomes have interesting antitumor properties and may produce important outcomes without PEG.

Tumor bombesin analog loaded long-circulating and pH-sensitive liposomes as tool for tumor identification.

Long-circulating and pH-sensitive liposomes trapping (99m)Tc-HYNIC-ßAla-bombesin((7-14)) (aSpHL-(99m)Tc-BBN((7-14))) were successfully prepared. Biodistribution studies and scintigraphic images were performed in Ehrlich tumor-bearing Swiss mice. This system showed high accumulation in tumor tissue with high tumor-to-muscle ratio. Therefore, aSpHL-(99m)Tc-BBN((7-14)) could be considered as a potential agent for tumor diagnosis.

Study of the pilot production process of long-circulating and pH-sensitive liposomes containing cisplatin.

Long-circulating and pH-sensitive liposomes, containing cisplatin (SpHL-CDDP), have been developed as an alternative aimed at avoiding severe side effects as well as the appearance of resistance, which can limit the use of free cisplatin. However, physical (i.e., aggregation/fusion) and chemical instabilities limit the use of these drug carriers as pharmaceutical products. The preparation of freeze-dried pharmaceuticals has proven to be a successful strategy implemented to improve the stability of these formulations. In addition, the development of an economically feasible, reproducible process of liposome production, on a large scale, has also become necessary. A pilot production process, using three stages (i.e., reverse-phase evaporation, homogenization under high pressure, and ultrafiltration), was used to prepare SpHL-CDDP. The optimization of factors related to the homonogenization under high pressure (i.e., pressure and number of cycles), ultrafiltration (i.e., number of cycles), and storage stability at 4°C were assessed by means of particle size, zeta potential, and encapsulation percentage. A 500-bar pressure and 9 cycles were adopted as measures for the production of SpHL-CDDP, which presented a mean diameter of 99.0 ± 3.9 nm and an encapsulation percentage of 12.9 ± 2.3. The use of trehalose as a cryoprotectant was investigated, regarding its effective ability to control the vesicle diameter and retain encapsulated CDDP after the freeze-drying/rehydration step. After 135 days of storage, freeze-dried or liquid SpHL-CDDP showed no significant change in mean diameter. However, the freeze-dried SpHL-CDDP proved to be more efficient, in terms of CDDP retention, than did the liposomal liquid dispersion.

Triggered Drug Release From Liposomes: Exploiting the Outer and Inner Tumor Environment.

Since more than 40 years liposomes have being extensively studied for their potential as carriers of anticancer drugs. The basic principle behind their use for cancer treatment consists on the idea that they can take advantage of the leaky vasculature and poor lymphatic drainage present at the tumor tissue, passively accumulating in this region. Aiming to further improve their efficacy, different strategies have been employed such as PEGlation, which enables longer circulation times, or the attachment of ligands to liposomal surface for active targeting of cancer cells. A great challenge for drug delivery to cancer treatment now, is the possibility to trigger release from nanosystems at the tumor site, providing efficacious levels of drug in the tumor. Different strategies have been proposed to exploit the outer and inner tumor environment for triggering drug release from liposomes and are the focus of this review.

Liposomal paclitaxel induces apoptosis, cell death, inhibition of migration capacity and antitumoral activity in ovarian cancer.

The main goal of this study is to evaluate the efficacy of the paclitaxel (PTX) drug formulated with a liposomal nanosystem (L-PTX) in a peritoneal carcinomatosis derived from ovarian cancer. In vitro cell viability studies with the human ovarian cancer line A2780 showed a 50% decrease in the inhibitory concentration for L-PTX compared to free PTX. A2780 cells treated with the L-PTX formulation demonstrated a reduced capacity to form colonies in comparison to those treated with PTX. Cell death following L-PTX administration hinted at apoptosis, with most cells undergoing initial apoptosis. A2780 cells exhibited an inhibitory migration profile when analyzed by Wound Healing and real-time cell analysis (xCELLigence) methods after L-PTX administration. This inhibition was related to decreased expression of the zinc finger E-box-binding homeobox 1 (ZEB1) and transforming growth factor 2 (TGF-ß2) genes. In vivoL-PTX administration strongly inhibited tumor cell proliferation in ovarian peritoneal carcinomatosis derived from ovarian cancer, indicating higher antitumor activity than PTX. L-PTX formulation did not show toxicity in the mice model. This study demonstrated that liposomal paclitaxel formulations are less toxic to normal tissues than free paclitaxel and are more effective in inhibiting tumor cell proliferation/migration and inducing ZEB1/TGF-ß2 gene expression.

Preclinical toxicological study of long-circulating and fusogenic liposomes co-encapsulating paclitaxel and doxorubicin in synergic ratio.

Combination therapy between paclitaxel (PTX) and doxorubicin (DXR) is applied as the first-line treatment of breast cancer. Co-administration of drugs at synergistic ratio for treatment is facilitated with the use of nanocarriers, such as liposomes. However, despite the high response rate of solid tumors to this combination, a synergism of cardiotoxicity may limit the use. Thus, the objective of this work was to investigate the toxicity of long-circulating and fusogenic liposomes co-encapsulating PTX and DXR at the synergistic molar ratio (1:10) (LCFL-PTX/DXR). For this, clinical chemistry, histopathological analysis and electrocardiographic exams were performed on female Balb/c mice that received a single intravenous dose of LCFL-PTX/DXR. The results of the study indicated that the LD50 dose range (lethal dose for 50% of animals) of the LCFL-PTX/DXR treatment (28.9-34.7 mg/kg) is much higher than that found for free PTX/DXR treatment (20.8-23.1 mg/kg). In addition, liposomes promoted cardiac protection by not raising CK-MB levels in animals, keeping cardiomyocytes without injury or electrocardiographic changes. After 14 days of treatment, free PTX/DXR caused prolongation of the QRS interval when compared to LCFL-PTX/DXR treatment at the same dose (37.0 ± 5.01 ms and 30.83 ± 2.62 ms, respectively, with p = 0.017). The survival rate of animals treated with LCFL-PTX/DXR was three times higher than that of those treated with free drugs. Thus, it was established that the toxicity of LCFL-PTX/DXR is reduced compared to the combination of free PTX/DXR and this platform has advantages for the clinical treatment of breast cancer.

pH-responsive and folate-coated liposomes encapsulating irinotecan as an alternative to improve efficacy of colorectal cancer treatment.

Irinotecan (IRN) is a semisynthetic derivative of camptothecin that acts as a topoisomerase I inhibitor. IRN is used worldwide for the treatment of several types of cancer, including colorectal cancer, however its use can lead to serious adverse effects, as diarrhea and myelosuppression. Liposomes are widely used as drug delivery systems that can improve chemotherapeutic activity and decrease side effects. Liposomes can also be pH-sensitive to release its content preferentially in acidic environments, like tumors, and be surface-functionalized for targeting purposes. Herein, we developed a folate-coated pH-sensitive liposome as a drug delivery system for IRN to reach improved tumor therapy without potential adverse events. Liposomes were prepared containing IRN and characterized for particle size, polydispersity index, zeta potential, concentration, encapsulation, cellular uptake, and release profile. Antitumor activity was investigated in a murine model of colorectal cancer, and its toxicity was evaluated by hematological/biochemical tests and histological analysis of main organs. The results showed vesicles smaller than 200 nm with little dispersion, a surface charge close to neutral, and high encapsulation rate of over 90%. The system demonstrated prolonged and sustained release in pH-dependent manner with high intracellular drug delivery capacity. Importantly, the folate-coated pH-sensitive formulation had significantly better antitumor activity than the pH-dependent system only or the free drug. Tumor tissue of IRN-containing groups presented large areas of necrosis. Furthermore, no evidence of systemic toxicity was found for the groups investigated. Thus, our developed nanodrug IRN delivery system can potentially be an alternative to conventional colorectal cancer treatment.

Mechanistic insights into the intracellular release of doxorubicin from pH-sensitive liposomes.

pH-sensitive liposomes are interesting carriers for drug-delivery, undertaking rapid bilayer destabilization in response to pH changes, allied to tumor accumulation, a desirable behavior in the treatment of cancer cells. Previously, we have shown that pH-sensitive liposomes accumulate in tumor tissues of mice, in which an acidic environment accelerates drug delivery. Ultimately, these formulations can be internalized by tumor cells and take the endosome-lysosomal route. However, the mechanism of doxorubicin release and intracellular traffic of pH-sensitive liposomes remains unclear. To investigate the molecular mechanisms underlying the intracellular release of doxorubicin from pH-sensitive liposomes, we followed HeLa cells viability, internalization, intracellular trafficking, and doxorubicin's intracellular delivery mechanisms from pH-sensitive (SpHL-DOX) and non-pH-sensitive (nSpHL-DOX) formulations. We found that SpHL-DOX has faster internalization kinetics and intracellular release of doxorubicin, followed by strong nuclear accumulation compared to nSpHL-DOX. The increased nuclear accumulation led to the activation of cleaved caspase-3, which efficiently induced apoptosis. Remarkably, we found that chloroquine and E64d enhanced the cytotoxicity of SpHL-DOX. This knowledge is paramount to improve the efficiency of pH-sensitive liposomes or to be used as a rational strategy for developing new formulations to be applied in vivo.