Analysis of ultrasound fields in cell culture wells for in vitro ultrasound therapy experiments.

Ultrasound is an established therapy method for bone fracture healing, hyperthermia and the ablation of solid tumors. In this new emerging field, ultrasound is further used for microbubble-enhanced drug delivery, gene therapy, sonoporation and thrombolysis. To study selected therapeutic effects in defined experimental conditions, in vitro setups are designed for cell and tissue therapy. However, in vitro studies often lack reproducibility and the successful transfer to other experimental conditions. This is partly because of the uncertainty of the experimental conditions in vitro. In this paper, the ultrasound wave propagation in the most common in vitro ultrasound therapy setups for cell culture wells is analyzed in simulations and verified by hydrophone measurements. The acoustic parameters of the materials used for culture plates and growth media are determined. The appearance and origin of standing waves and ring interference patterns caused by reflections at interfaces is revealed in simulations and measurements. This causes a local maximal pressure amplitude increase by up to the factor of 5. Minor variations of quantities (e.g., growth medium volume variation of 2.56%) increase or decrease the peak rarefaction pressure at a cell layer by the factor of 2. These pressure variations can affect cell therapy results to a large extent. A sealed cell culture well submersed in a water bath provides the best reproducibility and therefore promises transferable therapy results.

Synergistic effects of sonoporation and taurolidin/TRAIL on apoptosis in human fibrosarcoma.

Sonodynamic therapy, in combination with ultrasound contrast agents, proved to enhance the uptake of chemotherapeutics in malignant cells. HT1080 fibrosarcoma cells were treated in vitro with a combination of ultrasound SonoVue™-microbubbles and taurolidine (TRD) plus tumor necrosis factor related apoptosis inducing ligand (TRAIL). Apoptosis was measured by TdT-mediated dUTP-biotin nick end labelling (TUNEL) assay and fluorescence activated cell sorting (FACS) analysis. Gene expression was analysed by RNA-microarray. The apoptotic effects of TRD and TRAIL on human fibrosarcoma are enhanced by sonodynamic therapy and additional application of contrast agents, such as SonoVue™ by 25%. A broad change in the expression of genes related to apoptotic pathways is observed when ultrasound and microbubbles act synchronously in combination with the chemotherapeutics (e.g. BIRC3, NFKBIA and TNFAIP3). Some of these genes have already been proven to play a role in programmed cell death in human fibrosarcoma (HSPA1A/HSPA1B, APAF1, PAWR, SOCS2) or were associated with sonication induced apoptosis (CD44). Further studies are needed to explore the options of sonodynamic therapy on soft tissue sarcoma and its molecular mechanisms.

Evaluation of Ferucarbotran (Resovist) as a photoacoustic contrast agent / Evaluation von Ferucarbotran (Resovist) als photoakustisches Kontrastmittel.

Photoacoustic imaging combines the resolution of ultrasound imaging with the contrast of optical imaging, while maintaining a penetration depth up to a few centimeters. Inorganic gold nanorods can be employed as photoacoustic contrast agents. However, the toxicological properties of such nanoparticles are still under investigation. At the same time, there is an increasing need for clinically established photoacoustic contrast agents. In this paper, therefore, we investigate the photoacoustic properties of Ferucarbotran, which is a clinically established nanoscale contrast agent for magnetic resonance imaging. Gelatin phantoms containing cubes with different gelatin-Ferucarbotran mixture concentrations were prepared and irradiated by a Nd:YAG laser (1064 nm). First, the photoacoustic signals were acquired by a single element ultrasound transducer (7.5 MHz) and evaluated quantitatively. In a second setup, photoacoustic imaging of Ferucarbotran with a modified clinical scanner was demonstrated. The experiments showed that in order to achieve a 6 dB gain of received photoacoustic signal energy, compared to the sensitivity threshold of the used system, a Ferucarbotran concentration of 1.9 micromol Fe/ml is needed. The photoacoustic imaging was successful and showed a contrast-to-background ratio of 15.7 dB for a concentration of 11.63 micromol Fe/ml. However, for imaging in tissue the signal-to-noise ratio has to be increased.