Nanobubbles for enhanced ultrasound imaging of tumors

TLDR

Nanobubbles have shown promise as ultrasound contrast agents, but their nanoscale size, while enabling tumor vessel penetration for targeted imaging, weakens imaging performance compared to conventional microbubbles. The study fabricated lipid nanobubbles and assessed their passive tumor‑targeting capability in vivo. The authors fabricated lipid nanobubbles and used confocal laser scanning microscopy to directly observe fluorescently labeled NBs in tumor tissue. The lipid nanobubbles, averaging 436.8 nm, exhibited ultrasound imaging performance comparable to microbubbles, passively targeted tumor tissue, remained longer due to enhanced permeability and retention, and hold promise for drug/gene delivery. Keywords: phospholipids, ultrasound, contrast agent, tumor‑targeted.

Abstract

Abstract: The fabrication and initial applications of nanobubbles (NBs) have shown promising results in recent years. A small particle size is a basic requirement for ultrasound contrast-enhanced agents that penetrate tumor blood vessel pores to allow for targeted imaging and therapy. However, the nanoscale size of the particles used has the disadvantage of weakening the imaging ability of clinical diagnostic ultrasound. In this work, we fabricated a lipid NBs contrast-enhanced ultrasound agent and evaluated its passive targeting ability in vivo. The results showed that the NBs were small (436.8 ± 5.7 nm), and in vitro ultrasound imaging suggested that the ultrasonic imaging ability is comparable to that of microbubbles (MBs). In vivo experiments confirmed the ability of NBs to passively target tumor tissues. The NBs remained in the tumor area for a longer period because they exhibited enhanced permeability and retention. Direct evidence was obtained by direct observation of red fluorescence-dyed NBs in tumor tissue using confocal laser scanning microscopy. We have demonstrated the ability to fabricate NBs that can be used for the in vivo contrast-enhanced imaging of tumor tissue and that have potential for drug/gene delivery. Keywords: phospholipids, ultrasound, contrast agent, tumor-targeted