Lab on a Chip Systeme zur Probenaufbereitung in der patientennahen Labordiagnostik Abstract: Fast and reliable detection of infectious pathogens is in many clinical cases decisive for the therapy and prognosis of the patient. Detection methods like PCR are able to meet these requirements. However to ensure successful amplification and detection the sample should be purified from inhibiting substances. Since very small sample volumes are used in a PCR run a previous concentration should also be carried out to achieve a sufficient concentration of the target sequence and thus avoid false negative results. Standard procedures for the preparation of a sample are time consuming and require many manual steps a well equipped microbiological laboratory and well trained personnel making them unsuitable for point of care testing (POCT) and resulting in high costs.<br>This work is focused on the development of lab on a chip (LOC) systems which are capable of performing all steps of sample preparation. The concentration is based on free flow electrophoresis (FFE) and allows the preparation of both bacteria and viruses. For the first time it could be shown that the concentration of viruses by FFE is possible larger volumes can be processed in a few minutes and the electrical conductivity of the sample medium is crucial for a fast and efficient concentration. The extraction was carried out by thermal or thermoelectric lysis and on chip gel electrophoresis for the purification of DNA and RNA. It was shown that bacterial mRNA can be extracted from undiluted EDTA blood in less than three minutes.<br>Since the lab on a chip systems can be used to prepare both bacteria and viruses their process characteristics and technology enable the rapid preparation of complex sample matrices in the least amount of space and automation of the process can be easily implemented the systems represent a promising approach for POCT and may help to improve a patients prognosis in the future