Ultrasound-Mediated Drug Delivery With a Clinical Ultrasound System: In Vitro Evaluation

Abstract

Chemotherapy efficacy is often reduced by insufficient drug uptake in tumor cells. The combination of ultrasound and microbubbles (USMB) has been shown to improve drug delivery and to enhance the efficacy of several drugs in vitro and in vivo, through effects collectively known as sonopermeation. However, clinical translation of USMB therapy is hampered by the large variety of (non-clinical) US set-ups and US parameters that are used in these studies, which are not easily translated to clinical practice. In order to facilitate clinical translation, the aim of this study was to prove that USMB therapy using a clinical ultrasound system (Philips iU22) in combination with clinically approved microbubbles (SonoVue) leads to efficient in vitro sonopermeation. To this end, we measured the efficacy of USMB therapy for different US probes (S5-1, C5-1 and C9-4) and US parameters in FaDu cells. The US probe with the lowest central frequency (i.e. 1.6 MHz for S5-1) showed the highest USMB-induced intracellular uptake of the fluorescent dye SYTOX™ Green (SG). These SG uptake levels were comparable to or even higher than those obtained with a custom-built US system with optimized US parameters. Moreover, USMB therapy with both the clinical and the custom-built US system increased the cytotoxicity of the hydrophilic drug bleomycin. Our results demonstrate that a clinical US system can be used to perform USMB therapy as efficiently as a single-element transducer set-up with optimized US parameters. Therefore, future trials could be based on these clinical US systems, including validated US parameters, in order to accelerate successful translation of USMB therapy.

The Effect of Microbubble-Assisted Ultrasound on Molecular Permeability across Cell Barriers

“…In addition to increasing the intercellular permeability of hydrophilic molecules across the epithelial barrier, USMB induced intracellular accumulation of SYTOX TM green (molecular weight 600 Da) and two dextrans (molecular weight 4 and 20 kDa) as was already shown by us [ 26 , 37 ] and other groups [ 38 , 39 , 40 ] before. Quantification of fluorescent signals 30 and 120 min after incubation revealed that intracellular accumulation of dextrans was significantly higher in the cells treated with USMB at 0.7 MPa as compared to 0 MPa.…”

“…New studies using molecules with various hydrophilicities and molecular weights could help to comprehend the potential and limitations of USMB therapy in ocular drug delivery. Ideally, clinically approved microbubbles and a clinical ultrasound system could be used for USMB treatment [ 26 ] and to monitor microbubble emissions [ 56 ]. Finally, combination of USMB with pharmaceuticals (such as an anti-CXCR4 nanobody for the treatment of retinoblastoma) could be tested in in vivo disease models in order to determine the therapeutic efficacy of the method.…”

“…Sham-treated samples were immersed in the PBS bath for 2 min and served as negative controls (0 MPa). The pressure field maps ( Figure 1 D) of the transducer were measured with a calibrated hydrophone [ 26 ].…”

“…Right: axial plane, white dotted line indicates position of transversal plane. Adapted from [ 26 ], Frontiers Media S.A., 2021.…”

Proof of Concept: Protein Delivery into Human Erythrocytes Using Stable Cavitation

“…The improvement of drug/gene delivery by ultrasound in the presence of microbubbles has been widely studied. The combination of ultrasound and contrast agents of different compositions has been successfully applied in vitro and in vitro to molecules that hardly or not cross the cell membrane such as as cisplatin and bleomycin. − Evaluation of this approach in phase I clinical trials, although in a limited number of patients with pancreatic and hepatic cancer, has generated interesting results in terms of safety and drug clinical efficiency. , In a recent study using ultrasound in the presence of microbubbles and erythrocytes as carriers, increased trehalose uptake, an effective sugar for protection against desiccation, has been demonstrated by Centner et al with improvement of recovery of viable erythrocytes following freeze-drying and rehydration. The presented study is in the continuity of our previous publications exploiting the strong potential of ultrasound as an alternative tool for drug and nucleic acids delivery. − , A moderate correlation was found between inertial cavitation and hemolysis.…”