A fluorescent chromophore TOTO‐3 as a ‘smart probe’ for the assessment of ultrasound‐mediated local drug delivery in vivo

Abstract

Many potent anti-cancer drugs have an intracellular mode of action, but are limited in crossing the cell membrane, resulting in a reduced clinical efficacy. Ultrasound (US) is known to facilitate the penetration of drugs into tumors cells. However (molecular) imaging techniques that monitor in vivo the underlying processes of US-triggered drug delivery are lacking. The objective of this study was to demonstrate the feasibility of using a fluorescent nuclear acid stain (TOTO-3) as a model drug to monitor in real-time US-mediated delivery by in vivo fluorescence imaging. Following co-injection of TOTO-3 and microbubbles US was applied to the tumor. The time course of the drug delivery process was monitored by fluorescence imaging. Immunohistological analysis and in vitro experiments were performed to investigate the results in more detail. A significant signal intensity enhancement of the US-treated tumor was observed that indicates intracellular delivery of the dye. In the control tumor TOTO-3 signal was strongly associated with macrophages, which was not the case for the sonicated tumor. The capability of macrophages to uptake TOTO-3 was confirmed in vitro. This study demonstrates that an optical contrast agent with similar characteristics to an anti-cancer drug may be used for continuous in vivo monitoring of the drug delivery process.

Microbubble Therapy Enhances Anti‐tumor Properties of Cisplatin and Cetuximab In Vitro and In Vivo

“…20 This effect has been demonstrated previously by increased cellular uptake of small fluorescent molecules and labeled chemotherapeutic agents. 19 In the current in vitro experiments, we were able to use a membrane-impermeable fluorescent molecule to demonstrate the effects that MB-UST has on extracellular small-molecule uptake. Results show that MB-UST was sufficient to increase molecule uptake by showing a 41% increase in luciferase expression secondary to an increase in membrane permeability.…”

“…13,17 This application has also been shown to be effective in the delivery of small molecules and genetic material into cells. 13,18,19 The proposed mechanism of action is through mechanical vibration of MBs using US, whereby membrane disruption and tumor permeability are temporarily induced. 20 This effect has been demonstrated previously by increased cellular uptake of small fluorescent molecules and labeled chemotherapeutic agents.…”

Phase-shift, stimuli-responsive Drug Carriers for Targeted Delivery

“…IC of microbubbles creates microjets and shock waves that can create holes in blood vessels and cell membranes, thus increasing their permeability for drugs, genes and their carriers. The ultrasound-induced creation of pores in cell membranes is called sonoporation [29,83–94]. Although the mechanisms are very different, the end result of sonoporation is similar to the more common electroporation method.…”

Image-guided, targeted and triggered drug delivery to tumors using polymer-based microbubbles

“…This is because local US-induced MB oscillation (stable cavitation) or destruction (inertial cavitation), leads to a temporal permeabilization of blood vessels and/or cell membranes [15][16][17][18][19][20][21][22][23]. To exploit this potential of MB for facilitating drug delivery across biological barriers, therapeutic agents can either be co-administered with MB [24,25], or loaded into the shell of MB [13,26,27]. In addition to enhancing drug targeting to tumors, combining MB with US has also been extensively used for thrombolysis and for enabling drug delivery across the blood-brain-barrier [28][29][30][31].…”