Keplinger, Franz

In the pathological healing of chronic wounds the ordered sequence of tissue restoration is disturbed. As a consequence, chronic wounds fail to heal within months and pose a major impact on the patient by pain, odor, leakage, and the risk of infection and the health care system by its constant treatment. Introducing objective wound assessment by sensor technology into clinical routine would help to guide treatment procedures and improve the healing outcome. The aim of this research study was the development of simple and effective concepts to evaluate the wound status at the point of care. Requirements for point of care testing include a fast and flexible device use by untrained personal, reduced time and costs, as well as reliable and easy to interpret results. The complex nature of wounds can be divided into the different regimes of physical appearance, biochemical status and microbiological environment, which influence each other. Each regime is tackled separately in this work by identifying possible parameters for wound analysis from the literature and the design of sensor concepts to quantify these candidates. A miniaturized, wearable sensor system for the integration in a wound dressing was developed to collect healing relevant, physiological data. The sensor measures optical reflectance, heart rate, arterial oxigenation, surface pH, moisture and temperature. The function of the sensor system was verified in a porcine wound model. A combination of surface pH, reflected infrared, and red light showed to be the most significant parameter, associated with the healing progress. For the measurement of biochemical parameters a microfluidic platform for the preparation of biosensing hydrogels by in situ polymerization was designed. Introducing functional structures for gel patterning in the chip fabrication allows for rapid assay customization. Simple handling and functionality were illustrated by assays for matrix metalloproteinase, an important factor in chronic wound healing. In addition, the demonstrated assays for total protein concentration and cell counts indicate the possibilities for a wide range of fast and simple diagnostics. The last part of the thesis discusses microfluidic technologies for rapid analysis of bacteria. Preconcentration of bacteria by on-chip electrophoresis and detection by a simple optical setup are presented. Furthermore, devices for rapid and parallel growth-based bacterial identification and antibiotic testing in microfluidic cultures were designed. The presented results and demonstrated tools show that medical analysis can be improved by sensor technologies that are simple to operate and yield fast results at the point of care.

In the last years the term Optofluidics has popped up in a large amount of scientific publications. The goal of this thesis is to prove Optofluidics as an applicable, powerful tool for distinct biological and medical applications. In the main part of this work, an optofluidic sensing unit for the determination of liquid concentration is presented. In an experimental evaluation, the sensor was tested with different dissolved molecules including phosphate and lactose. Depending on the analyte, a smallest detectable change in concentration of 10 to 40mmol/L was determined. Besides the sensing device, a new subfield of optofluidics was introduced for the very first time. Thermo-optofluidics deals with the integration of thermal elements in optofluidic systems. Compared to solely solid based realizations more than twice the theoretical switching frequency can be achieved. In conclusion, the applicability of optofluidics for different sensor as well as actuator systems was experimentally proven. All the devices were fabricated applying low-cost, rapid-prototyping fabrication techniques which allow the realization of cost-effective hand-held devices.

Keplinger, Franz

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