Lipid emulsions of palmitoylrhizoxin: effects of composition on lipolysis and biodistribution

Nanoemulsions as Delivery Systems for Poly-Chemotherapy Aiming at Melanoma Treatment

Aims: Advanced melanoma is characterized by poor outcome. Despite the number of treatments having been increased over the last decade, current pharmacological strategies are only partially effective. Therefore, the improvement of the current systemic therapy is worthy of investigation. Methods: a nanotechnology-based poly-chemotherapy was tested at preclinical level. Temozolomide, rapamycin, and bevacizumab were co-loaded as injectable nanoemulsions for total parenteral nutrition (Intralipid^®), due to suitable devices, and preliminarily tested in vitro on human and mouse cell models and in vivo on the B16-F10 melanoma mouse model. Results: Drug combination was efficiently loaded in the liquid lipid matrix of Intralipid^®, including bevacizumab monoclonal antibody, leading to a fast internalization in tumour cells. An increased cytotoxicity towards melanoma cells, as well as an improved inhibition of tumour relapse, migration, and angiogenesis were demonstrated in cell models for the Intralipid^®-loaded drug combinations. In preliminary in vivo studies, the proposed approach was able to reduce tumour growth significantly, compared to controls. A relevant efficacy towards tumour angiogenesis and mitotic index was determined and immune response was involved. Conclusions: In these preliminary studies, Intralipid^® proved to be a safe and versatile poly-chemotherapy delivery system for advanced melanoma treatment, by acting on multiple mechanisms.

Preparation of Conjugated Linoleic Acid Microemulsions and their Biodistribution

Conjugated linoleic acid (CLA) has several beneficial biological properties. Specifically, trans10, cis12-CLA, one of the CLA isomers, has strong physiologic activity against cancer and obesity. However, compared with cis9, trans11-CLA, a naturally occurring CLA isomer, trans10, cis12-CLA tends to be easily metabolized. Therefore, to make efficient use of its biological properties, it is necessary to overcome the rapid clearance of trans10, cis12-CLA from the blood. Here, we employed premix membrane emulsification to prepare two oil-in-water CLA microemulsions (CLA-ME), 100 nm CLA-ME and 200 nm CLA-ME, and investigated their pharmacokinetics in a mouse model. We report that 100 nm CLA-ME contributed to the concentration of blood CLA for longer than 200 nm CLA-ME, indicating that small CLA microparticles were more suitable for maintaining blood trans10, cis12-CLA levels in vivo. However, both CLA-ME could be hardly detected in blood and other tissues 24 h after administration, suggesting that additional strategies for prolonging CLA-ME half-life are required.

Influence of particle size on the in vitro and in vivo anti-inflammatory and anti-allergic activities of a curcumin lipid nanoemulsion

The polyphenolic compound, curcumin, is a natural yellow pigment component of turmeric. It exerts various biological effects, such as anti-inflammatory effects, and we have previously demonstrated that curcumin is a specific inhibitor of DNA polymerase λ. Curcumin is characterized by poor bioavailability as it is water-insoluble, is poorly absorbed and is systemically eliminated. In order to increase the bioavailability of curcumin, in this study, we produced a curcumin-loaded lipid nanoemulsion of various particle sizes (50, 100 and 200 nm). The curcumin lipid nanoemulsion was prepared by a modified thin-film hydration method followed by sonication. To identify the optimal particle size which exhibits the strongest physiological activity, we investigated the inhibitory effects of the obtained nanoemulsions against inflammatory and allergic activities. In in vitro cell culture experiments, the 100-nm curcumin lipid nanoemulsion showed the most prominent inhibitory effect on the production of tumor necrosis factor-α (TNF-α) induced by lipopolysaccharide (LPS) in RAW264.7 murine macrophages, and on the release of β-hexosaminidase induced by the calcium ionophore, A23187, in rat basophilic leukemia RBL-2H3 cells. In an in vivo experiment, in which mice were administered the curcumin-loaded lipid nanoemulsion of various particle sizes, the 100-nm curcumin lipid nanoemulsion showed the most prominent anti-inflammatory and anti-allergic effects, inhibiting 12-O-tetradecanoylphorbol-13-acetate-induced inflammatory ear edema and immunoglobulin E (IgE)-induced passive cutaneous anaphylactic (PCA) reaction. The effects of particle size on serum curcumin absorption were also assessed in mice, and the 100-nm lipid nanoemulsion showed the greatest absorption. The results from our study suggest that the physiological activities of curcumin lipid nanoemulsions differ depending on particle size. Our data indicate that the curcumin lipid nanoemulsion with a particle size of 100 nm has potential for use in enhancing the bioavailability and medical value of curcumin.

Block copolymers at interfaces: interactions with physiological media

Triblock copolymers (also known as Pluronics or poloxamers) are biocompatible molecules composed of hydrophobic and hydrophilic blocks with different lengths. They have received much attention recently owing to their applicability for targeted delivery of hydrophobic compounds. Their unique molecular structure facilitates the formation of dynamic aggregates which are able to transport lipid soluble compounds. However, these structures can be unstable and tend to solubilize within the blood stream. The use of nanoemulsions as carriers for the lipid soluble compounds appears as a new alternative with improved protection against physiological media. The interfacial behavior of block copolymers is directly related to their peculiar molecular structure and further knowledge could provide a rational use in the design of poloxamer-stabilized nanoemulsions. This review aims to combine the new insights gained recently into the interfacial properties of block copolymers and their performance in nanoemulsions. Direct studies dealing with the interactions with physiological media are also reviewed in order to address issues relating metabolism degradation profiles. A better understanding of the physico-chemical and interfacial properties of block copolymers will allow their manipulation to modulate lipolysis, hence allowing the rational design of nanocarriers with efficient controlled release.

Computed tomography-guided screening of surfactant effect on blood circulation time of emulsions: application to the design of an emulsion formulation for paclitaxel

PURPOSE

In an effort to apply the imaging techniques currently used in disease diagnosis for monitoring the pharmacokinetics and biodisposition of particulate drug carriers, we sought to use computed tomography (CT) scanning methodology to investigate the impact of surfactant on the blood residence time of emulsions.

METHODS

We prepared the iodinated oil Lipiodol emulsions with different compositions of surfactants and investigated the impact of surfactant on the blood residence time of emulsions by CT scanning.

RESULTS

The blood circulation time of emulsions was prolonged by including Tween 80 or DSPE-PEG (polyethylene glycol 2000) in emulsions. Tween 80 was less effective than DSPE-PEG in terms of prolongation effect, but the blood circulating time of emulsions was prolonged in a Tween 80 content-dependent manner. As a proof-of-concept demonstration of the usefulness of CT-guided screening in the process of formulating drugs that need to be loaded in emulsions, paclitaxel was loaded in emulsions prepared with 87 or 65% Tween 80-containing surfactant mixtures. A pharmacokinetics study showed that paclitaxel loaded in 87% Tween 80 emulsions circulated longer in the bloodstream compared to those in 65% Tween 80 emulsions, as predicted by CT imaging.

CONCLUSIONS

CT-visible, Lipiodol emulsions enabled the simple evaluation of surfactant composition effects on the biodisposition of emulsions.

Lipid emulsion as a drug delivery system for breviscapine: formulation development and optimization

In this study, we developed an optimized formulation of a breviscapine lipid emulsion (BLE) and evaluated the physicochemical properties and in vivo pharmacokinetics of BLE in rats. For the preparation of the lipid emulsion, soybean oil and oleic acid were used as the oil phase, lecithin and poloxamer 188 as surfactants and glycerol as co-surfactant. An optimized formulation consisting of soybean oil (10.0%), oleic acid (0.9%), lecithin (1.5%), poloxamer 188 (0.4%), and glycerol (2.25%) was selected. The results showed that the average particle size, polydispersity index, and zeta potential of the optimized formulation were 183.5 ± 5.5 nm, 0.098 ± 0.046, and -35.0 ± 2.5 mV, respectively. The BLE was stable for at least three month at room temperature. After a single intravenous dose of 4 mg/kg to rats, the AUC of scutellarin from the lipid emulsion was about 1.5-fold higher than that of the commercial product (breviscapine injection). In conclusion, the optimized formulation of BLE showed positive results over the commercial product in terms of the physicochemical properties and pharmacokinetics of BLE in rats.

Preparation of Lipid Nanoemulsions Incorporating Curcumin for Cancer Therapy

The aim of this study was to develop a new formulation of a curcumin lipid nanoemulsion having the smallest particle size, the highest loading, and a good physical stability for cancer chemotherapy. Curcumin lipid nanoemulsions were prepared by a modified thin-film hydration method followed by sonication. Soybean oil, hydrogenatedL-α-phosphatidylcholine from egg yolk, and cosurfactants were used to formulate the emulsions. The resultant nanoemulsions showed mean particle diameter of 47–55 nm, could incorporate 23–28 mg curcumin per 30 mL, and were stable in particle size for 60 days at 4°C. The cytotoxicity studies of curucumin solution and curcumin-loaded nanoemulsion using B16F10 and leukemic cell lines showed IC50values ranging from 3.5 to 30.1 and 22.2 to 53.7 μM, respectively. These results demonstrated the successful incorporation of curcumin into lipid nanoemulsion particles with small particle size, high loading capacity, good physical stability, and preserved cytotoxicity.

Injectable lipid emulsions-advancements, opportunities and challenges

Injectable lipid emulsions, for decades, have been clinically used as an energy source for hospitalized patients by providing essential fatty acids and vitamins. Recent interest in utilizing lipid emulsions for delivering lipid soluble therapeutic agents, intravenously, has been continuously growing due to the biocompatible nature of the lipid-based delivery systems. Advancements in the area of novel lipids (olive oil and fish oil) have opened a new area for future clinical application of lipid-based injectable delivery systems that may provide a better safety profile over traditionally used long- and medium-chain triglycerides to critically ill patients. Formulation components and process parameters play critical role in the success of lipid injectable emulsions as drug delivery vehicles and hence need to be well integrated in the formulation development strategies. Physico-chemical properties of active therapeutic agents significantly impact pharmacokinetics and tissue disposition following intravenous administration of drug-containing lipid emulsion and hence need special attention while selecting such delivery vehicles. In summary, this review provides a broad overview of recent advancements in the field of novel lipids, opportunities for intravenous drug delivery, and challenges associated with injectable lipid emulsions.

Formulation of multifunctional oil-in-water nanosized emulsions for active and passive targeting of drugs to otherwise inaccessible internal organs of the human body

Oil-in-water (o/w) type nanosized emulsions (NE) have been widely investigated as vehicles/carrier for the formulation and delivery of drugs with a broad range of applications. A comprehensive summary is presented on how to formulate the multifunctional o/w NE for active and passive targeting of drugs to otherwise inaccessible internal organs of the human body. The NE is classified into three generations based on its development over the last couple of decades to make ultimately a better colloidal carrier for a target site within the internal and external organs/parts of the body, thus allowing site-specific drug delivery and/or enhanced drug absorption. The third generation NE has tremendous application for drug absorption enhancement and for 'ferrying' compounds across cell membranes in comparison to its first and second generation counterparts. Furthermore, the third generation NE provides an interesting opportunity for use as drug delivery vehicles for numerous therapeutics that can range in size from small molecules to macromolecules.

Antileishmanial activity, pharmacokinetics and tissue distribution studies of mannose-grafted amphotericin B lipid nanospheres

Leishmania parasite resides mainly in the liver and the spleen and multiplies. Effective therapy of leishmaniasis could be achieved by delivering antileishmanial drugs to these sites. Present investigations were aimed at developing lipid nanospheres of amphotericin B (LN-A) anchored with mannose to achieve targeted delivery to the liver. Mannose is specifically involved in the recognition of parasite or appropriate ligands on the macrophage surface LN-A, and mannose-anchored lipid nanospheres (LN-A-MAN) were prepared by homogenization followed by ultrasonication method. Particle size and zeta potential were measured using Malvern Zetasizer. The average particle size after sterilization of LN-A and LN-A-MAN ranged from 193.4 +/- 1.1 to 775.8 +/- 9.1. Leishmaniasis was induced in BALB/c mice by injecting Leishmania donovani parasites intravenously. Infected mice were administered with a single dose (5 mg/kg body weight) of LN-A, LN-A-MAN, and Fungizone (marketed product).The efficacy of the formulations was evaluated by measuring the reduction in parasite burden. Fungizone reduced 82 and 69%, LN-A reduced 90 and 85%, LN-A-MAN reduced 95 and 94% of parasite burden in the liver and the spleen, respectively. LN-A and LN-A-MAN-treated mice did not show any elevation in serum glutamate pyruvate transaminase (SGPT), alkaline phosphatase (ALP), urea, and creatinine levels as compared with Fungizone. Pharmacokinetic parameters were estimated and the concentration of amphotericin B (AmB) in mice plasma declined biexponentially and AmB concentrations were significantly higher for LN-A- and LN-A-MAN than Fungizone-treated mice (P < 0.05). Tissue distribution patterns were studied in different tissues such as the liver, the spleen, the kidney, and the brain of BALB/c mice. LN-A-MAN was found to distribute more rapidly to the liver and the spleen explaining the reason for higher antileishmanial activity.

Species variation in pharmacokinetics and opsonization of palmitoyl rhizoxin (RS-1541) incorporated in lipid emulsions

Highly lipophilic antitumor agent, palmitoyl rhizoxin (RS-1541), was incorporated into stable lipid emulsions about 100-1000nm in mean diameter consisting of triglyceride ODO and surfactant HCO-60. The pharmacokinetics of RS-1541 were studied after i.v. injection in mice, rats, rabbits, and dogs. Dog showed characteristic pharmacokinetics of RS-1541, compared with other species. RS-1541 was much more rapidly eliminated from plasma with emulsion particles in dogs than in mice, rats, and rabbits. Most amounts of injected RS-1541 were recovered in the liver six hours after administration to dogs, while less than 20% recoveries were observed for mice and rats. To clarify this species variation, opsonization of emulsion particles were evaluated. When emulsions (about 200nm in size) were opsonized by dog plasma, and intravenously injected to rats, total clearance and liver uptake of RS-1541 were increased to 1.8 fold and 2.7 fold of control values, respectively. In contrasts, emulsions opsonized by mouse, rabbit and human plasma did not show such drastic changes in pharmacokinetics of RS-1541 in rats. Furthermore, total clearance of RS-1541 for emulsions opsonized by dog plasma was increased to 1.9 fold of controls after injection to rabbits. These results indicate that opsonizing activities of dog plasma for RS-1541 emulsions are high, compared with other species. This species variation in opsonizing process probably caused the species variation in the pharmacokinetics of RS-1541 incorporated in lipid emulsions.

Enhanced tumor delivery and antitumor activity of palmitoyl rhizoxin using stable lipid emulsions in mice

PURPOSE

A highly lipophilic antitumor agent, 13-O-palmitoyl-rhizoxin (RS-1541), was incorporated into lipid emulsions of various sizes consisting of triglyceride ODO and surfactant HCO-60. Pharmacokinetics, toxicities, and antitumor activities were evaluated after intravenous administration to mice bearing subcutaneously inoculated M5076 sarcoma cells.

METHODS

The levels of RS-1541 in the plasma and tissues including tumor, were determined by HPLC. The maximum tolerated dose (MTD) was estimated by toxic death and change in body weight. The decrease in tumor diameter was measured for antitumor activity.

RESULTS

There existed large variations in pharmacokinetics of RS-1541, depending on the size of emulsion particles. Compared with a colloidal solution (reference solution), the small (110nm) and medium (230nm) size emulsions showed high concentrations of RS-1541 in the tumor, while the large emulsions (350nm-630nm) exhibited low concentrations. The MTD of RS-1541 was reduced, when incorporated in the emulsions larger than 220nm in size. At MTD, each size of emulsions (70nm-380nm) effectively retarded the tumor growth and increased survival time. The maximum effect was achieved for the 220 nm emulsions.

CONCLUSIONS

When particle size is properly selected, these emulsions could be promising and effective as an injectable carrier for lipophilic antitumor agents in order to enhance the tumor delivery and efficacies while reducing toxicities.