Andreas H. Foitzik

A3.2 - Enzyme free sensor based on affinity viscosimetry for detection of glucose

The growing demand of miniaturization of cell cultivation new approaches towards measuring and sensing bio-analytes need to be addressed to overcome the challenge of small volumes (less than 150μl) containing small amounts of analytes. Most of the available glucose sensors monitor the glucose concentration with the help of enzymes, which become very unstable in terms of long time measurement and consume glucose during the measurement becoming not available anymore for the cells. Therefore, the focus was set on applying an enzyme-free glucose sensor based on a microelectromechanical system (MEMS).

Affinity Viscosimetry Sensor for Enzyme Free Detection of Glucose in a Micro-Bioreaction Chamber

With the growing demand of miniaturization of cell cultivation a new approach towards measuring and sensing bio-analytes needs to be made due to the problem of small volumes (less than 150μl) containing small amounts of analytes. Most of the available glucose sensors monitor the glucose concentration with the help of enzymes, which become very inaccurate in terms of long time measurement and uses (i.e. consumes) glucose during the measurement becoming not available anymore for the cells. Therefore, we focused on applying an enzyme-free glucose sensor based on a microelectromechanical system (MEMS).

A New Approach for the Spectroscopic Detection of Different pH-Values

The objective of the present work was the development of a micro-pH meter for the determination of the pH value within bioreactors with a volume of up to 200 μl in total. Two different prototypes of optodes were designed and tested. In a first approach spectroscopic analysis of bromothymol blue in a micro-sized-channel structure was carried out utilizing glass fibers, enabling measurements in sample volumes down to the range of picoliters. In a second approach a different illumination system consisting of a RGB-sensor and a LED light source was used. Phenol red was successfully applied as the pH indicator for this setup.

Experimental Bio-ESPI for Validation of Magnetic Induced Deformation on HeLa Cells

The determination of mechanical properties can provide insight into complex biochemical processes such as the cell cycle and even the progression of diseases. However, this field of biomechanical research strongly depends on a high-resolution measurement technology and a gentle stimulation method in order to examine these mostly biological samples in their original condition. In terms of this work, a different approach utilizing a modified ESPI setup and two types of ferro-fluids is presented. By exposing the prepared specimen to an electro-magnetic field it has been possible to induce a local displacement and to monitor the deformation with the adapted ESPI setup.

Miniaturized Flow-Through Bioreactor for Processing and Testing in Pharmacology

Conventional Bioreactor systems for cultivating cells in Life Science have been widely used for decades. An in vitro cell cultivation bioreactor should reliably and reproducibly mimic the in vivo microenvironment of the cultured cells. Normally, mammalian cell cultures are performed in conventional bioreactor devices such as culture flasks and culture-dishes. However, these tools have fundamental limitations due to being inappropriate for high throughput screening and consume a considerable amount of resources and time [1]. Therefore, there is a trend towards miniaturization, disposables and even micro platforms that fulfill increasing demands strongly aiming for production and testing of novel pharmaceutical products. Here we present the development and manufacture of a disposable miniaturized flow-through bioreactor system that can be produced in large numbers at low costs. nanoporous hollow fibers are located at the fluidic sources and drains of the miniaturized bioreactors and retain cells. The necessary mixture of oxygen and carbon dioxide is provided via diffusion through a semi-permeable membrane. Fluidic connections allow the continuous feeding of the cells adding nutrient solution at constant rates at the inlet of the micro bioreactor and removing the solution at the same rate at the outlet. This medium can be collected and used for subsequent analysis. Different designs and concepts for such bioreactors were carried out with varying numbers of plates, and integrated or joined miniaturized reactor chambers. First tests show full technical and biological functionality, cells could successfully be cultivated at high viability rates for some days.

Components of a Heart Catheter System for High Risk Patients

As late as fifteen years ago the intracardiac catheter was only used for diagnostic purposes. Since then it has also been established as a therapeutic method. The latest studies have shown that the reduction in convalescence that normally follows a catheter-interventional implantation of aortic valves by transcatheter aortic valve implantation is less significant in comparison to that of a cardiac surgery operation. It is expected that such minimal-invasive technologies will grow to a great extent, also helping to reduce socio-economic costs for the European health care system. Patients of higher ages with acquired cardiac defects or children with congenital cardiac defects of heart valves, especially of the pulmonary valve, are currently the main target groups. We present an alternative and optimized mechanism for stent placement and similar therapeutical interventions. This project focuses on the manipulation unit and tube system. It carries out a highly precise and repeatable linear motion. Ergonomic requirements are taken into account. Furthermore a possibility to support the linear motion by minimal strain is presented. The product is designed for disposable applications but is generally also suitable for long-term applications.

Novel ESPI Measurement Prototype for Analyzing Biological Samples from Cell Culture Technique

An essential part of cell cultivation via cell culture technology is the determination and monitoring of culture parameters. Such parameters refer to the vitality or mutual mutations of the cell culture, while the actual number of living cells in each batch indicates the correct growth rate rather than stagnation or an overgrowth of the cell culture. Today such parameters are determined by applying light microscopy methods or by staining specific constituents of the cells. Commonly such methods are a stressful procedure for the studied cells. Most applied dyes are toxic over a certain period of time and thus they are used in low concentrations only when necessary. Within this work a new kind of measurement device prototype was designed to address these problems. This device is based on the Electronic Speckle Pattern Interferometry (ESPI). ESPI is an optical high-resolution method combined with a photonic analysis system capable of analyzing cellular deformations and oscillations. In this approach the combination of a greatly modified microscope together with ESPI method is presented. The apparatus allows the determination of cellular deformation (i) at very high magnifications, (ii) with high lateral resolution. Furthermore the system studies (iii) contact free, (iv) in vitro cells, in a non-invasive and non-destructive way. A co-developed cultivation system allows monitoring the culture parameters in real time minimizing the stress for the cell culture. Since no additional substances are needed, the presented prototype is automated to a large extent and can be operated by a special control-and regulation system (CRS) based on a microcontroller development board (Arduino Mega).

Novel Bioreactor-System for In Situ-Cultivation of Artificial Tissue

A bioreactor is a device simulating physiological environments for different biotechnological applications. In highly promising research fields like tissue engineering micro-sized bioreactors were utilized successfully promoting mammalian cells to grow and build 3D cell structures similar to in vivo environments. For any practical application and even for improved R&D it is necessary to generate and maintain a physiological environment over the whole cultivation period (hours, days or weeks, in case of artificial organs even up to months). Depending on the field of application physiological environments can comprise different parameters. In case of mammalian cell lines these parameters require a complex supply and monitoring system. Thus, we developed a semi-automated bioreactor-system for long-term cultivation of different mammalian cell types imitating physiological conditions. The system included detection and control of the following parameters: temperature, pH-value, gas concentration and the continuous supply with nutrients. A micro fluidic network was established enabling a high through-put cultivating system as bioreactor-system. The bioreactor-system consists of several micro-sized chambers in a microliter scale (the related article discussing the micro-sized chambers “Miniaturized Flow-Through Bioreactor for Processing and Testing in Pharmacology” by Boehme et al is published within this issue). The chambers were placed in a polymeric slide each with an individual medium supply and disposal. Every single chamber thus was connected to an individual syringe-based micro-pump setup and supplied by nutrients solution with a velocity of 100μl/h. The pH-value was observed optically and controlled via CO2 supply. All gas interchanges into every single chamber were realized via semi permeable membranes. The required temperature was adjusted via an appropriate custom-fit heating system utilizing MOSFETs allocated on an aluminum board along the slides. Two slides each were housed in a PMMA case. This bioreactor-system is a first prototype for larger systems aiming for the parallel operation of up to 100 micro-sized reaction chambers.