[Physical Properties of Squamous Cell Carcinoma Cells using Atomic Force Microscopy]. / Bestimmung elastischer Eigenschaften von Plattenepithelkarzinomzellen mittels Rasterkraftmikroskopie.

INTRODUCTION: Malignant and benign cells differ according to their elasticity. An atomic force microscope is a useful tool for measuring these mechanical cell properties. If cells of different dignity show different resonance behavior, due to their different elasticity, a selective ablation of specific tissue types by ultrasound would be possible. The goal is a highly selective ablation of tumor tissue without damaging healthy tissue. MATERIALS AND METHODS: We performed elasticity measurements of tumor cells (UD-01 cell line) with an atomic force microscope. In a further step, an ultrasound applicator has been positioned and the morphological changes of the cells during the treatment were documented. RESULTS: Different elasticities on the squamous cells were measured, depending on the location. Below a defined maximum amplitude the morphological cell changes were caused solely by ultrasonic excitation. SUMMARY: The atomic force microscope is suitable for the determination of the individual cell elasticity. The data collected could be the basis for treatment modalities that lead to a very selective damage for malignant cells.

Direct comparison between potential landscape and local density of states in a disordered two-dimensional electron system.

The local density of states (LDOS) of the adsorbate-induced two-dimensional electron system (2DES) on n-InAs(110) is studied by scanning tunneling spectroscopy. In contrast to a similar 3DES, the 2DES LDOS exhibits 20 times stronger corrugations and rather irregular structures. Both results are interpreted as consequences of weak localization. Fourier transforms of the LDOS reveal that the k values of the unperturbed 2DES still dominate the 2DES, but additional lower k values contribute. To clarify the origin of the LDOS patterns, we measure the potential landscape of the 2DES area. We use it to calculate the expected LDOS and find reasonable agreement between calculation and experiment.