Conventional methods for enzyme immobilisation onto sensor surfaces often use dip‐, drop‐ or spin‐coating techniques. In this study, a nano‐spotting technique has been investigated for a patterned, spatially resolved deposition of enzymes onto a capacitive field‐effect electrolyte–insulator–semiconductor (EIS) sensor and compared with the drop‐coating method. Therefore, four different sensor arrangements covered with immobilised penicillinase as a model enzyme have been studied: (i) The sensor surface fully drop‐coated, (ii) half drop‐coated, (iii) half nano‐spotted and (iv) fully nano‐spotted with penicillinase. The sensors have been electrochemically characterised in pH buffers and penicillin solutions by means of impedance‐spectroscopy, capacitance–voltage and constant‐capacitance methods.

A novel sensor system is introduced featuring real-time in-situ monitoring of biodegradation processes. The system measures changes of the electrochemical properties of the polymer under investigation to quantify the progress of the degradation process. As a result, a higher time resolution is achieved and higher throughput can be realized compared to common measurement techniques. The obtained results demonstrate the potential of field-effect sensors as promising non-destructive tool for the real-time monitoring of polymer degradation.

A semiconductor field-effect device has been used for an enzymatically catalyzed degradation of biopolymers for the first time. This novel technique is capable to monitor the degradation process of multiple samples in situ and in real-time. As model system, the degradation of the biopolymer poly(D,L-lactic acid) has been monitored in the degradation medium containing the enzyme lipase from Rhizomucor miehei. The obtained results demonstrate the potential of capacitive field-effect sensors for degradation studies of biodegradable polymers.

A semiconductor field-effect device has been used for an enzymatically catalyzed degradation of biopolymers for the first time. This novel technique is capable to monitor the degradation process of multiple samples in situ and in real-time. As model system, the degradation of the biopolymer poly(D, L-lactic acid) has been monitored in the degradation medium containing the enzyme lipase from Rhizomucor miehei. The obtained results demonstrate the potential of capacitive field-effect sensors for degradation studies of biodegradable polymers.

The characterization of the degradation kinetics of biodegradable polymers is mandatory with regard to their proper application. In the present work, polymer-modified electrolyte–insulator–semiconductor (PMEIS) field-effect sensors have been applied for in-situ monitoring of the pH-dependent degradation kinetics of the commercially available biopolymer poly(d,l-lactic acid) (PDLLA) in buffer solutions from pH 3 to pH 13. PDLLA films of 500nm thickness were deposited on the surface of an Al–p-Si–SiO2–Ta2O5 structure from a polymer solution by means of spin-coating method. The PMEIS sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. A faster degradation has been observed for PDLLA films exposed to alkaline solutions (pH 9, pH 11 and pH 13).

It is well known that the degradation environment can strongly influence the biodegradability and kinetics of biodegradation processes of polymers. Therefore, besides the monitoring of the degradation process, it is also necessary to control the medium in which the degradation takes place. In this work, a micromachined multi‐parameter sensor chip for the control of the polymer‐degradation medium has been developed. The chip combines a capacitive field‐effect pH sensor, a four‐electrode electrolyte‐conductivity sensor and a thin‐film Pt‐temperature sensor. The results of characterization of individual sensors are presented. In addition, the multi‐parameter sensor chip together with an impedimetric polymer‐degradation sensor was simultaneously characterized in degradation solutions with different pH and electrolyte conductivity. The obtained results demonstrate the feasibility of the multi‐parameter sensor chip for the control of the polymer‐degradation medium.

In vitro Untersuchungen des Degradationsverlaufs sind essentiell für die Entwicklung und Optimierung implantierbarer Medizinprodukte auf der Basis von biodegradierbaren Polymeren.Erstmals wurde mit Hilfe eines halbleiterbasierten kapazitiven Feldeffektsensors, der über Impedanzspektren ausgelesen wird, ein Sensorsystem realisiert, das die Echtzeitmessung der Degradation in situ ermöglicht.In einem Modellversuch wurde die Funktionalität des System demonstriert, indem die Degradation eines kommerziell erhältlichen, biodegradierbaren Polymers (Poly-D,L-Milchsäure) in Echtzeit verfolgt wurde.Dazu wurde das Polymer mittels Spin-Coating auf den Sensor aufgebracht und zunächst einer neutralen Pufferlösung (pH 7) zur Degradation ausgesetzt.Nach einer Zeit von 53,5 h wurde der pH-Wert auf pH 9 erhöht, um die hydrolytische Degradation zu beschleunigen.Die derart erzeugte Veränderung der Degradationsrate des Polymers konnte in einer beschleunigten Abnahme der Impedanzwerte des Sensorsignals gezeigt werden.

In vitro studies of the degradation kinetic of biopolymers are essential for the design and optimization of implantable biomedical devices. In the presented work, a field-effect capacitive sensor has been applied for the real-time and in situ monitoring of degradation processes of biopolymers for the first time. The polymer-covered field-effect sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. The feasibility of this approach has been experimentally proven by using the commercially available biomedical polymer poly(D,L-lactic acid) (PDLLA) as a model system. PDLLA films of different thicknesses were deposited on the Ta2O5-gate surface of the field-effect structure from a polymer solution by means of spin-coating method. The polymer-modified field-effect sensors have been characterized by means of capacitance-voltage and impedance-spectroscopy method. The degradation of the PDLLA was accelerated by changing the degradation medium from neutral (pH 7.2) to alkaline (pH 9) condition, resulting in drastic changes in the capacitance and impedance spectra of the polymer-modified field-effect sensor. (C) 2012 Elsevier B. V. All rights reserved.

For the development of new biopolymers and implantable biomedical devices with predicted biodegradability, simple, non-destructive, fast and inexpensive techniques capable for real-time in situ testing of the degradation kinetics of polymers are highly appreciated. In this work, a capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensor has been applied for real-time in situ monitoring of degradation of thin poly(D,L-lactic acid) (PDLLA) films over a long-time period of one month. Generally, the polymer-modified EIS (PMEIS) sensor is capable of detecting any changes in the bulk, surface and interface properties of the polymer (e.g., thickness, coverage, dielectric constant, surface potential) induced by degradation processes. The time-dependent capacitance-voltage (C-V) characteristics of PMEIS structures were used as an indicator of the polymer degradation. To accelerate the PDLLA degradation, experiments were performed in alkaline buffer solution of pH 10.6. The results of these degradation measurements with the EIS sensor were verified by the detection of lactic acid (product of the PDLLA degradation) in the degradation medium. In addition, the micro-structural and morphological changes of the polymer surface induced by the polymer degradation have been systematically studied by means of scanning-electron microscopy, atomic-force microscopy, optical microscopy, and contact-angle measurements. (C) 2013 Elsevier Ltd. All rights reserved.

Investigation of the degradation kinetics of biodegradable polymers is essential for the development of implantable biomedical devices with predicted biodegradability. In this work, an impedimetric sensor has been applied for real-time and in situ monitoring of degradation processes of biopolymers. The sensor consists of two platinum thin-film electrodes covered by a polymer film to be studied. The benchmark biomedical polymer poly(D,L-lactic acid) (PDLLA) was used as a model system. PDLLA films were deposited on the sensor structure from a polymer solution by using the spin-coating method. The degradation kinetics of PDLLA films have been studied in alkaline solutions of pH 9 and 12 by means of an impedance spectroscopy (IS) method. Any changes in a polymer capacitance/resistance induced by water uptake and/or polymer degradation will modulate the global impedance of the polymer-covered sensor that can be used as an indicator of the polymer degradation. The degradation rate can be evaluated from the time-dependent impedance spectra. As expected, a faster degradation has been observed for PDLLA films exposed to pH 12 solution.