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

Direct comparison of two kinds of linoleic acid-docetaxel derivatives: in vitro cytotoxicity and in vivo antitumor activity

Rational designed lipid-drug derivatives provide a favorable approach to improve the druggability of highly hydrophobic prototypes. It has been regarded as common sense that good cytotoxicity is the guarantee of superior anticancer efficacy for candidate derivatives screening. However, does it apply to lipid-drug conjugate-based self-assembled nanoparticles? Here, we established the above two derivatives and a non-correlation between the cytotoxic activity in vitro and drug efficacy in vivo was found. The IC₅₀ of DSL NPs (DTX-S-LA nanoparticles) and DL NPs (DTX-LA nanoparticles) were 4.02 and 209.6 ng/mL (DTX equivalent concentration), respectively. However, DL NPs unexpectedly showed stronger tumor inhibition abilities than DSL NPs. To explain the non-positive correlation between cytotoxicity and anticancer efficacy, more experiments were carried out in depth. Remarkably, the drug release studies in blood and PK study both suggested that the DL NPs were more stable to remain the structural integrity in circulation, which resulted in more accumulation in tumor sites. As verified by the bio-distribution study, DL NPs performed a superior target effect than DSL NPs in tumors. Our data indicated that the biological fates of so-called smart bond inserted derivatives in vivo are complicated; thus, simple cytotoxicity is not enough for derivatives screening, and the comprehensive understanding of both in vitro and in vivo behaviors is essential.

Recent Development of Copolymeric Nano-Drug Delivery System for Paclitaxel

Background:

Paclitaxel (PTX) has been clinically used for several years due to its good therapeutic effect against cancers. Its poor water-solubility, non-selectivity, high cytotoxicity to normal tissue and worse pharmacokinetic property limit its clinical application.

Objective:

To review the recent progress on the PTX delivery systems.

Methods:

In recent years, the copolymeric nano-drug delivery systems for PTX are broadly studied. It mainly includes micelles, nanoparticles, liposomes, complexes, prodrugs and hydrogels, etc. They were developed or further modified with target molecules to investigate the release behavior, targeting to tissues, pharmacokinetic property, anticancer activities and bio-safety of PTX. In the review, we will describe and discuss the recent progress on the nano-drug delivery system for PTX since 2011.

Results:

The water-solubility, selective delivery to cancers, tissue toxicity, controlled release and pharmacokinetic property of PTX are improved by its encapsulation into the nano-drug delivery systems. In addition, its activities against cancer are also comparable or high when compared with the commercial formulation.

Conclusion:

Encapsulating PTX into nano-drug carriers should be helpful to reduce its toxicity to human, keeping or enhancing its activity and improving its pharmacokinetic property.

Simultaneous sentinel lymph node computed tomography and locoregional chemotherapy for lymph node metastasis in rabbit using an iodine-docetaxel emulsion

Purpose

A sentinel lymph node (SLN) tracer can gain multi-functionality by combining it with additional components. We developed a SLN tracer consisting of iodine and docetaxel and applied it as a theragnostic nanoparticle to simultaneously perform SLN computed tomography (CT) lymphography and locoregional chemotherapy of the draining lymphatic system.

Results

Docetaxel could be loaded in iodine emulsions at a drug-to-surfactant weight ratio as high as that in the drug formulation Taxotere^®. The particle size and drug concentration were stable during storage for up to 3 months in optimized nanoemulsions. Popliteal LN enhancement on CT was observed in all healthy rabbits (n=3) and VX2 tumor-implanted rabbits (n=6) 12 hours after injection. The rate of SLN metastasis was significantly lower in the treatment group (29.4%, 5/17) than in the non-treatment group (70.6%, 12/17) (P=0.038).

Material and Methods

We prepared a nanoemulsion carrying both iodine and docetaxel in a single structure by optimizing the composition of surfactants surrounding the inner iodized oil core. CT was performed 12 hours after subcutaneous injection of the emulsion in healthy rabbits (n=3) and VX2 tumor-implanted rabbits (n=6) for SLN imaging. Next, we tested the effect of treatment by histopathologically assessing the popliteal LN metastasis rate in VX2 tumor-implanted rabbits 7 days after subcutaneous injection of the emulsion (treatment group, n=17) and comparing it with that of non-treatment group rabbits (n=17).

Conclusions

We developed an iodine-docetaxel emulsion and demonstrated that it can be applied to simultaneously achieve CT SLN imaging and local chemotherapy against nodal metastasis.

2-Hydroxyoleic acid-inserted liposomes as a multifunctional carrier of anticancer drugs

Studies have shown that insertion of oleic acid into lipid bilayers can modulate the membrane properties of liposomes so as to improve their function as drug carriers. Considering that 2-hydroxyoleic acid (2OHOA), a potential antitumor agent currently undergoing clinical trials, is a derivative of oleic acid, we explored the possibility of developing 2OHOA-inserted liposomes as a multifunctional carrier of antitumor drugs in the present study. The insertion of 2OHOA into lipid bilayers was confirmed by surface charge determination and differential scanning calorimetry. 2OHOA insertion greatly decreased the order of dimyristoylphosphatidylcholine packing, produced a nanosized (<100 nm) dispersion, and improved the colloidal stability of liposomes during storage. Moreover, 2OHOA-inserted liposome forms exhibited greater growth inhibitory activity against cancer cells compared with free 2OHOA, and the growth-inhibitory activity of liposomal 2OHOA was selective for tumor cells. 2OHOA insertion greatly increased the liposome-incorporated concentration of hydrophobic model drugs, including mitoxantrone, paclitaxel, and all-trans retinoic acid (ATRA). The in vitro anticancer activity of ATRA-incorporated/2OHOA-inserted liposomes was significantly higher than that of ATRA-incorporated conventional liposomes. In a B16-F10 melanoma syngeneic mouse model, the tumor growth rate was significantly delayed in mice treated with ATRA-incorporated/2OHOA-inserted liposomes compared with that in the control group. Immunohistochemical analyses revealed that the enhanced antitumor activity of ATRA-incorporated/2OHOA-inserted liposomes was due, at least in part, to increased induction of apoptosis. Collectively, our findings indicate that 2OHOA-inserted liposomes exhibit multiple advantages as antitumor drug carriers, including the ability to simultaneously deliver two anticancer drugs - 2OHOA and incorporated drug - to the tumor tissue.

Development of paclitaxel-loaded liposomal nanocarrier stabilized by triglyceride incorporation

Studies have highlighted the challenge of developing injectable liposomes as a paclitaxel (PTX) carrier, a challenge attributable to the limitations in liposomal stability caused by PTX loading. Poor stability of PTX-loaded liposomes is caused by PTX-triggered aggregation or fusion of liposomal membranes and is exacerbated in the presence of PEGylated lipid. In the present study, the effect of triglyceride incorporation on the stability of PTX-loaded/PEGylated liposomes was explored. Incorporation of a medium chain triglyceride Captex 300 into saturated phosphatidylcholine (PC)-based liposomes (1,2-dimyristoyl-sn-glycero-3-phosphocholine [DMPC]:cholesterol [CHOL]:N-(Carbonyl-methoxypolyethyleneglycol 2000)-1, 2-distearoyl-sn-glycero-3-phospho-ethanolamine [PE-PEG]), produced a fine, homogeneous, and membrane-filterable PTX-loaded liposomes fulfilling the requirement of an injectable lipid formulation. Triglyceride incorporation also greatly inhibited the time-dependent leakage of PTX from saturated PC-based liposomes, which appears to be mediated by the inhibition of liposome fusion. In contrast, triglyceride incorporation induced the destabilization and PTX leakage of unsaturated PC-based liposomes, indicating the opposite effect of triglyceride depending on the fluidity status of PC constituting the liposomal membrane. PTX release profile and the in vitro and in vivo anticancer efficacy of triglyceride-incorporated DMPC:CHOL:PE-PEG liposomes were similar to Taxol^® while the toxicity of liposomal PTX was significantly lower than that of Taxol. Taken together, triglyceride incorporation provided an injectable PTX formulation by functioning as a formulation stabilizer of PEGylated/saturated PC-based liposomes.

Effects of triglycerides on the hydrophobic drug loading capacity of saturated phosphatidylcholine-based liposomes

A high drug-loading capacity is a critical factor for the clinical development of liposomal formulations. The accommodation of hydrophobic drugs within the liposomal membrane is often limited in saturated phosphatidylcholine (PC)-based liposomes owing to the rigidity of the lipid acyl chain. In the current study, we explored the possibility of improving the hydrophobic drug loading capacity of liposomes by incorporating triglyceride into liposomal membranes. Incorporation of Captex 300, a medium chain triglyceride, into liposomes composed of dimyristoylphosphatidylcholine and cholesterol greatly increased the fluidity and lamellarity of the resultant liposomes. Liposomal incorporation of medium or long chain, but not short chain, triglycerides greatly enhanced the concentration of loaded paclitaxel (PTX) in saturated PC-based liposomes. The enhancing effect of triglyceride saturated at a triglyceride content corresponding to the amount required to fluidize the liposome structure. In addition, the enhancing effect was not observed in unsaturated PC-based liposomes and was not associated with the solubility of PTX in each triglyceride. Triglycerides also enhanced the loading of docetaxel, another hydrophobic drug. Taken together, our results suggest that triglyceride incorporation in saturated PC-based liposomes provide an improved dosage form that enables increased hydrophobic drug loading by altering the fluidity and structure of liposomal membranes.

Fluorescent iodized emulsion for pre- and intraoperative sentinel lymph node imaging: validation in a preclinical model

PURPOSE

To validate the usefulness of a newly developed tracer for preoperative gastric sentinel lymph node (LN) (SLN) mapping and intraoperative navigation after a single preoperative submucosal injection in rat and beagle models.

MATERIALS AND METHODS

This study was approved by the Experimental Animal Ethical Committee of Yonsei University College of Medicine according to the eighth edition of the Guide for the Care and Use of Laboratory Animals published in 2011. An emulsion was developed that contained indocyanine green in iodized oil, which can be visualized with both computed tomography (CT) and near-infrared (NIR) optical imaging and has the property of delayed washout. This emulsion was injected into the footpad of rats (n = 6) and the gastric submucosa of beagles (n = 8). CT lymphography was performed. The degree of enhancement of popliteal LNs was measured in rats, and the enhancing LNs were identified and the degree of enhancement of the enhancing LNs was measured in beagles. Next, NIR imaging was performed in beagles during open, laparoscopic, and robotic surgery to identify LNs containing the fluorescent signals of indocyanine green. The enhanced LNs detected with CT lymphography and NIR imaging were matched to see if they corresponded.

RESULTS

Preoperative CT lymphography facilitated SLN mapping, and 26 SLNs were identified in eight beagles. NIR imaging enabled high-spatial-resolution visualization of both SLNs and the intervening lymphatic vessels and was useful for intraoperative SLN navigation.

CONCLUSION

SLN mapping with fluorescent iodized oil emulsion is effective and feasible for both CT and NIR imaging.