Use of a Glass Membrane Pumping Emulsification Device Improves Systemic and Tumor Pharmacokinetics in Rabbit VX2 Liver Tumor in Transarterial Chemoembolization

Ultrasonic Heating Detects Lipiodol Deposition within Liver Tumors after Transarterial Embolization: An In Vivo Approach

Simple Summary

The accumulation of Lipiodol (ethiodized oil) after transarterial embolization is known to reflect tumor necrosis. In general, the treatment effect is evaluated by computed tomography; there has been no development in imaging modalities for several decades. A new technique, ultrasonic heating, can differentiate biological tissues based on the fact that tissues’ characteristic sound velocity varies depending on the temperature. This technique could have the potential to evaluate treatment effect after transarterial embolization as an alternative to computed tomography.

Abstract

Computed tomography (CT) is the standard method to evaluate Lipiodol deposition after transarterial embolization (TAE) for a long period. However, iodine but not Lipiodol can be observed on CT. A minimally invasive other method to detect Lipiodol has been needed to evaluate accurate evaluation after procedure. The purpose of this study was to evaluate the efficacy of using the rate of change in sound velocity caused by ultrasonic heating to reflect Lipiodol accumulation after TAE in a rat liver tumor model. We analyzed the association of this developed technique with CT images and histological findings. Eight rats bearing N1S1 cells were prepared. After confirmation of tumor development in a rat liver, Lipiodol was injected via the hepatic artery. Seven days after TAE, CT scan and sound velocity changes caused by ultrasonic heating were measured, and then the rats were sacrificed. An ultrasonic pulse-echo method was used to measure the sound velocity. The temperature coefficient of the sound velocity in each treated tumor was evaluated and compared with the mean CT value and the histological Lipiodol accumulation ratio. Pearson’s correlation coefficients were calculated to assess the correlation between the measured values. The correlation coefficient (r) of the mean CT value and histological Lipiodol accumulation ratio was 0.835 (p = 0.010), which was considered statistically significant. Also, those of the temperature coefficient of the sound velocity and the histological Lipiodol accumulation ratio were statistically significant (r = 0.804; p = 0.016). To our knowledge, this is the first study that reported the efficacy of ultrasonic heating to detect Lipiodol accumulation in rat liver tumors after TAE. Our results suggest that the rate of change in sound velocity caused by ultrasonic heating can be used to evaluate Lipiodol accumulation in liver tumors after TAE, and thus could represent an alternative to CT in this application. This new innovative technique is easy to treat and less invasive in terms of avoiding radiation compared with CT.

Solid-in-Oil-in-Water Emulsion: An Innovative Paradigm to Improve Drug Stability and Biological Activity

Abstract

An emulsion is a biphasic dosage form comprising of dispersed phase containing droplets that are uniformly distributed into a surrounding liquid which forms the continuous phase. An emulsifier is added at the interface of two immiscible liquids to stabilize the thermodynamically unstable emulsion. Various types of emulsions such as water-in-oil (w-o), oil-in-water (o-w), microemulsions, and multiple emulsions are used for delivering certain drugs in the body. Water (aqueous) phase is commonly used for encapsulating proteins and several other drugs in water-in-oil-in-water (w-o-w) emulsion technique. But this method has posed certain problems such as decreased stability, burst release, and low entrapment efficiency. Thus, a novel “solid-in-oil-in-water” (s-o-w) emulsion system was developed for formulating certain drugs, probiotics, proteins, antibodies, and tannins to overcome these issues. In this method, the active ingredient is encapsulated as a solid and added to an oil phase, which formed a solid-oil dispersion. This dispersion was then mixed with water to form a continuous phase for enhancing the drug absorption. This article focuses on the various studies done to investigate the effectiveness of formulations prepared as solid-oil-water emulsions in comparison to conventional water-oil-water emulsions. A summary of the results obtained in each study is presented in this article. The s-o-w emulsion technique may become beneficial in near future as it has shown to improve the stability and efficacy of the entrapped active ingredient.

Graphical abstract

Useful Parameters in Dynamic Contrast-enhanced Ultrasonography for Identifying Early Response to Chemotherapy in a Rat Liver Tumor Model

Objectives

The objective of the study is to determine a parameter on the time-intensity curve (TIC) of dynamic contrast-enhanced ultrasonography (DCE-US) that best correlates with tumor growth and to evaluate whether the parameter could correlate with the early response to irinotecan in a rat liver tumor model.

Material and Methods

Twenty rats with tumors were evaluated (control: Saline, n = 6; treatment: Irinotecan, n = 14) regarding four parameters from TIC: Peak intensity (PI), k value, slope (PI × k), and time to peak (TTP). Relative changes in maximum tumor diameter between day 0 and 10, and parameters in the first 3 days were evaluated. The Mann-Whitney U-test was used to compare differences in tumor size and other parameters. Pearson's correlation coefficients (r) between tumor size and parameters in the control group were calculated. In the treatment group, relative changes of parameters in the first 3 days were compared between responder and non-responder (<20% and ≥20% increase in size on day 10, respectively).

Results

PI, k value, PI × k, and TTP significantly correlated with tumor growth (r = 0.513, 0.911, 0.665, and 0.741, respectively). The mean RC in k value among responders (n = 6) was significantly lower than non-responders (n = 8) (mean k value, 4.96 vs. 72.5; P = 0.003).

Conclusion

Parameters of DCE-US could be a useful parameter for identifying early response to irinotecan.

Efficacy of a Glass Membrane Emulsification Device to Form Mixture of Cisplatin Powder with Lipiodol on Transarterial Therapy for Hepatocellular Carcinoma

PURPOSE

To examine physiochemical characteristics and drug release properties of cisplatin powder and lipiodol mixtures formed by a glass membrane emulsification device compared with a 3-way stopcock.

MATERIALS AND METHODS

Seven different types of mixtures were evaluated: cisplatin powder and lipiodol directly mixed (suspension), complete cisplatin solution and lipiodol mixed by a 3-way stopcock or the device (emulsion), incomplete cisplatin solution and lipiodol mixed by a 3-way stopcock or the device (solid-in-water emulsion), and contrast material and cisplatin suspension mixed by a 3-way stopcock or the device (solid-in-oil emulsion).

RESULT

The percentages of water-in-oil were 98.08 ± 0.27% in the emulsion formed by the device, while 70.3 ± 4.63% in the emulsion formed by a 3-way stopcock (P = 0.037). Solid-in-water and solid-in-oil emulsions formed by the device showed 98.09 ± 0.38% and 98.70 ± 0.40% of water-in-oil, respectively, whereas both solid-in-water and solid-in-oil emulsions formed by a 3-way stopcock showed 0.00%. Homogenous droplet sizes were shown by using the device. The half release times of cisplatin in the emulsions formed by the device were 197 ± 19, 244 ± 24 and 478 ± 52 min, respectively, which were significantly longer than the emulsion formed by a 3-way stopcock of 8 ± 8 min (P = 0.046-0.050). Suspension showed the longest release time; however, the viscosity was lowest.

CONCLUSION

The glass membrane emulsification device formed almost 100% water-in-oil, whereas 3-way stopcock produced 100% oil-in-water when incomplete solution or suspension was mixed. Slower cisplatin release was shown in the emulsions formed by the device.

In vivo evaluation of a monodisperse solid-in-oil-in-water miriplatin/ lipiodol emulsion in transcatheter arterial chemoembolization using a rabbit VX2 tumor model

Transcatheter arterial chemoembolization (TACE) is a standard treatment for unresectable hepatocellular carcinoma; however, it does not always result in tumor control. Nevertheless, treatment outcome can be improved with monodisperse emulsions of anticancer agents. In this study, the distribution of a monodisperse miriplatin-Lipiodol emulsion in the tumor and its safety were evaluated in ten Japanese white rabbits. VX2 tumor was implanted into the left liver lobe. The animals were divided into control and experimental groups (of five animals each) and respectively administered a conventional miriplatin suspension or the emulsion via the left hepatic artery. Computed tomography (CT) was performed before, immediately after, and two days following TACE. All rabbits were sacrificed two days after the procedure. Each tumor was removed and cut in half for assessment of iodine concentration in one half by mass spectroscopy and evaluation of Lipiodol accumulation and adverse events in the other half. Mean Hounsfield unit (HU) values were measured using plain CT images taken before and after TACE. Iodine concentration was higher in the experimental group [1100 (750-1500) ppm, median (range)] than in the control group [840 (660-1800) ppm], although statistically not significant. Additionally, the HU value for the experimental group was higher than that for the control group immediately after [199.6 (134.0-301.7) vs. 165.3 (131.4-280.5)] and two days after [114.2 (56.1-229.8) vs. 58.3 (42.9-132.5)] TACE, although statistically not significant. Cholecystitis was observed in one rabbit in the control group. Ischemic bile duct injury was not observed in any group. The results show that Lipiodol accumulation and retention in VX2 tumor can possibly be improved with a monodisperse emulsion; however, it should be verified with a larger study. Moreover, no significant adverse events are associated with the use of the emulsion.