Electrical impedance tomography of single cells in rolled-up microtubes

Datum

24.05.2017

Zeit

13:00 - 14:00

Sprecher

Sonja Maria Weiz

Zugehörigkeit

IIN, IFW Dresden

Sprache

en

Hauptthema

Materialien

Andere Themen

Materialien, Physik

Host

Kristina Krummer-Meier

Beschreibung

In recent years, it has become increasingly clearer that biological cells within one and the same cell culture can exhibit differing properties and behavior. These variations can be essential for the cellular processes that are observed, which has led to a growing interest in techniques that are able to quantify this cellular heterogeneity.[1] One method that is especially suited is impedance, since it is non-destructive, allows real-time data acquisition and does not require any sort of label. Spatially resolved measurement can also be carried out, which is referred to as electrical impedance tomography (EIT). EIT is an imaging technique with which the conductivity distribution inside an object is visualized by external application of an alternating current.[2] Recently, more and more miniaturized setups in the millimetric scale are developed, e.g. for visualization of tissue electroporation or flow in microreactors.[3,4] By employing rolled-up nano-technology,[5] even smaller devices in the sub-100 µm size scale can be elaborated which are suitable for the impedemetric imaging of micro-objects like single biological cells or small cell clusters. Microtubes with an integrated array of electrodes on the inner tube circumference were fabricated by several steps of 2D photolithography and e-beam depositions. Successively, a Ge sacrificial layer, a strained TiO2 bilayer, a Cr/Au electrode layer and a final insulating SiO2 layer which defines the active electrode areas were patterned onto glass substrates. By immersion into an aqueous hydrogen peroxide solution, the sacrificial layer is selectively removed, yielding rolled-up tubes with a diameter of ca. 35 µm (see Figure 1a). EIT measurements were carried out using an EIT system (Sciospec Scientific Instruments). For the first tests, the samples were immersed in PBS solution, and SiO2 micro-particle phantoms of different sizes (12 µm and 22 µm) were introduced into the rolled-up tube with a micromanipulator. Measurements were carried out with current injection of 11 µA between adjacent electrodes. A fidelity-embedded regularization (FER) method[6] was used to generate the frequency-difference EIT images which are shown in Figure 1b. The images show that the presence of the particles in the microtube as well as the size difference can be detected, serving as a proof-of-principle for the functionality of the microtubular EIT device. Furthermore, measurements were carried out with HeLa cells, which are human cervical cancer cells often used as a model. A current injection of 1 µA between adjacent electrodes was used for measurements in 0.01X PBS medium. EIT images were acquired over a time span of 3.5 h, during which cell death occurred. The images show a clear difference between the healthy and the dead HeLa cell (Figure 1c). These promising results pave the way for the detailed study of cell-cell, cell-material and cell-drug interactions using the fabricated microtubular EIT device.

Links

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Letztmalig verändert: 24.05.2017, 09:52:37