(C-117) The Impact of the Lipid Formulation on Ultrasound Contrast Agent Fabrication

Introduction:: In the medical field, ultrasound imaging has become an essential technique for managing diseases and improving diagnoses. However, ultrasound imaging has limitations in its ability to distinguish tissue features, which led to the formulation of nanoscale spheres as ultrasound contrast agents (UCA). UCAs are nanoscale spheres of gas with low solubility in blood. Many compositions exist in the literature although with limited explanation for composition. Therefore, there is a need to investigate different compositions to elucidate the effects on size uniformity, stability, and echogenicity. This study aims to find how specifically lipid composition made of DPPA,DPPC,DPPE,DBPC,and DSPE-mPEG2000 affects the nanobubble's size, stability, and echogenicity.

Materials and Methods:: Three lipid compositions were done to observe the effect on the nanobubbles. The most commonly used lipids for fabrication include DPPC, DPPA, and DPPE due to their biocompatibility with living organisms and ability to form micelles and liposomes. The first lipid formulation is a 1:2:8 mass ratio of the lipids DPPC, DPPA, and DPPE with 1 mg of DiI, which is used for staining purposes and to image the nanobubbles; the second formulation is a 4:1:1:1 mass ratio of the lipids DPPC, DPPA, DPPE, and DSPE-mPEG, and the third formulation is a 6:1:2:1 mass ratio of the lipids DBPC, DPPA, DPPE, and DSPE-mPEG2000. The first two lipid formulations use chloroform to create a lipid layer, while the third formulation uses propylene glycol to dissolve the lipids. However, all three formulations have a gas core of octafluoropropane and are shaken, using a Lantheus Medical Imaging Vialmix Shaker, for 45 seconds. Each formulation had an experimental group with either a ratio or lipid change. To measure the uniformity in size of the USCAs nanobubbles, Dynamic Light Scattering (DLS) was done on the control group and the experimental group. Using DLS will allow measuring the stability of the nanobubbles since it measures the Furthermore, ultrasound imaging was used to observe the nanobubbles' echogenicity concerning different dilutions to observe the changes in intensity, which were measured using the program ImageJ which is a Java-based image processing program that will allow to measure how bright the nanobubbles are with the help of a linear graph.

Results, Conclusions, and Discussions:: An initial optimization study demonstrated the echogenicity of both the control and experimental nanobubbles are echogenic. Through the different formulations, it was shown how changes in the ratio and the lipid have an effect on the size of the nanobubble with a plot that measure the Z-average size which is the intensity weighted mean size of the ensemble collection of particles for the control group and experimental group of the three formulations. Also, a plot created with Image J shows how the lipid formulation affects the intensity of the nanobubbles.

Ultrasound contrast agents need to be chemically stable, have maximal contrast enhancement, biological inertness and complete extravasation from the body, and injectable intravenously.The nanobubbles made in this study achieve a stable size and that can enhance ultrasound waves. Moving forward, observing the stability, extravasation time, and retention time of the nanobubbles with in vivo experiments is crucial to see if they can be use as ultrasound contrast agents. 

Acknowledgements (Optional): :

References (Optional): :