Abstract – Therapeutic Bubbles'

The Young Investigator Winner, WFUMB 2011, Klazina Kooiman

Klazina Kooiman ¹ Miranda Foppen-Harteveld¹, Antonius F.W. van der Steen^1,2, and Nico de Jong^1,2,3

1Dept. of Biomedical Engineering, Thoraxcenter, Erasmus MC, Rotterdam, the Netherlands

2Interuniversity Cardiology Institute of the Netherlands, Utrecht, the Netherlands

2Dept. of Applied Physics, Physics of Fluids, University of Twente, Enschede, the Netherlands

Purpose

Molecular imaging using ultrasound uses targeted ultrasound contrast agents that consist of encapsulated gas microbubbles. Until now, targeted microbubbles have only been used for imaging, not for therapy. In this study we investigated whether they could also be used to induce sonoporation, resulting in a transient increase in cell membrane permeability so that therapeutics can enter the cell.

Methods and materials

CD31-targeted microbubbles were made and allowed to adhere to human umbilical vein endothelial cells. Microbubble-cell behavior upon insonification at 1 MHz (10 cycle sine-wave bursts) was studied with the Brandaris 128 high-speed camera (frame rate ∼ 13 MHz). Microbubble diameter (D) – time curves were extracted from the recordings and the relative vibration amplitude, Dmax – Dmin normalized to the resting diameter D0, was calculated. Propidium iodide (PI; 25 μg/ml) was used as indicator for sonoporation.

Results

Thirty-one cells were studied that all had one microbubble attached per cell. After insonification at 80 kPa (MI 0.08), 30% of the cells had taken up PI, while this was 20% at 120 kPa (MI 0.12), and 83% at 200 kPa (MI 0.20). Irrespective of the applied peak negative acoustic pressure, uptake of PI was observed when the relative vibration amplitude of the targeted microbubbles was larger than 0.5. No relationship was found between the position of the microbubble on the cell and induction of sonoporation.

Conclusion

This study reveals that vibrating targeted microbubbles can induce sonoporation. This feature may now be used in molecular imaging, thereby combining ultrasound imaging and therapy.

Young Investigator award Klazina Kooiman (1977) studied Bio-Pharmaceutical Sciences at the University of Leiden, the Netherlands, from 1995–2000 and graduated cum laude. She did her main traineeship at the department of Pharmaceutical Technology of the Leiden/Amsterdam Center for Drug Research (LACDR) under supervision of Prof. dr. H.E. Junginger. Subsequently, she started to work as a PhD student at the Radboud University Nijmegen Medical Centre, the Netherlands. Due to the Epstein Barr virus she could not finish the project. From 2005–2010 she was a PhD student at the Department of Biomedical Engineering of the Erasmus MC, the Netherlands. The research was performed under the supervision of Prof. dr. ir. N. de Jong and Prof. dr. ir. A.F.W. van der Steen. Her project focused on using ultrasound contrast agents (microbubbles) as local drug delivery systems. Both the simultaneous administration of drugs and microbubbles and the incorporation of drugs into microbubbles were studied. The results were presented at national and international conferences. Two of her poster presentations were awarded with a poster prize and two of her oral presentations were awarded with the best student presentation. On January 19, 2011 she obtained her PhD on ‘therapeutic bubbles’. The research described in her thesis aids in understanding how to utilise ultrasound and bubbles for therapy in the most optimal way. She currently holds a postdoc position at the Department of Biomedical Engineering focusing on targeted microbubble imaging of vasa vasorum in atherosclerosis. She participates in the European FP7 Sonodrugs project focusing on ultrasound-triggered drug delivery systems and supervises two PhD students. She is (co)author of seven peer reviewed articles and has an h-index of six. At WFUSMB 2011 in Vienna she won the EFSUMB Young Investigator award.