1. Drug Research Program Division of Pharmaceutical Chemistry and Technology Faculty of Pharmacy University of Helsinki Helsinki 00014 Finland
2. Department of Pharmaceutics Faculty of Pharmacy Alexandria University Alexandria 21521 Egypt
3. Department of Biomedical Engineering University Medical Center Groningen University of Groningen Ant. Deusinglaan 1 Groningen 9713 AV The Netherlands
4. W.J. Kolff Institute for Biomedical Engineering and Materials Science University Medical Center Groningen University of Groningen Ant. Deusinglaan 1 Groningen 9713 AV The Netherlands