Abstract. Many conventional analysis techniques achieve a high-detection sensitivity; however, they are equipment or time expensive due to a multi-step procedure. Sensor concepts, introduced in this work, using piezoresistive pressure sensor chips with integrated analyte-sensitive hydrogels enable inexpensive and robust biochemical sensors, which are miniaturized and in-line capable. For these sensor setups, it is important to optimize current established analyte-sensitive, reversible and biocompatible hydrogels for pH and glucose monitoring of chemical and biochemical processes. Therefore, low-viscous monomer mixtures based on hydroxypropyl methacrylate (HPMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), tetraethylene glycol dimethacrylate (TEGDMA) and ethylene glycol (EG) were prepared in molar ratios of 70/30/01/20, 60/40/01/20 and 60/40/02/20, respectively. Redox-polymerization of these pre-gel solutions were realized with N,N,N ,Ntetramethylethylenediamine and ammonium persulfate. The reversible pH-sensitive swelling behavior of hydrogels with compositions were compared. By using the photoinitiator 2-hydroxy-4 -(2-hydroxyethoxy)-2-methylpropiophenone, the free radical photopolymerization could be implemented leading to an increase of the swelling degree (SG). Glucose-sensitive hydrogels were prepared via immobilization of glucose oxidase in HPMA-DMAEMA-TEGDMA-EG hydrogel discs. These showed increasing swelling degrees with higher glucose concentrations in aqueous media and a reversible swelling behavior. The synthesized hydrogels were integrated in different piezoresistive sensors of different designs. The pH-depending course of the output voltage of a dip sensor with photopolymerized 60/40/02/20 hydrogel was studied in detail. Besides the usage of a dip sensor, two implantable, parylene C-coated setups are presented. The implantable sensor with long isolated gold bond wires was proved to be functional even after storage in aqueous media for several days.

Abstract. The treatment of metabolic diseases, such as diabetes mellitus, requires sensitive measuring systems. These should be able to detect the different metabolism-related parameters (blood glucose level, pH, pCO 2 ) simultaneously and continuously. A new approach is an implantable wireless sensor microarray consisting of several hydrogel-based piezoresistive sensors that can provide an on-line monitoring of physiological parameters in the human body fluid. The specifically customized stimuli-responsive hydrogels enable the development of reliable biosensors for different analytes. In this regard, the on-line medical diagnostics attracts the main interest. The developed sensor system and its encapsulation should correspond to high requirements on the biocompatibility of implants according to the medical standard DIN EN ISO 10993-5. A multi-layer sensor encapsulation consisting of parylene C and amphiphilic block copolymers was proposed for subcutaneous implants and characterized using contact angle measurements and X-ray photoelectron spectroscopy. In vitro studies with model cells showed no cytotoxicity of the polyethylene glycol-based block copolymers. In order to understand the behavior of implants under physiological conditions, the interaction of the implant surface with biological specimen like proteins is discussed, taking into account the possible protein adsorption on the implant surface due to tissue inflammation around the implant, which should be minimized. Finally, the biocompatibility of the developed sensor system was studied to prove the suitability of the approach.

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