Characterization of biodegradable polymers with capacitive field-effect sensors

Abstract

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 Ta 2 O 5gate 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.

Degradation of thin poly(lactic acid) films: Characterization by capacitance–voltage, atomic force microscopy, scanning electron microscopy and contact-angle measurements

“…The thickness of the polymer films was approximately 300 nm. A more detailed description of the deposition of the polymer film can be found in [15].…”

“…Recently, a capacitive field-effect electrolyte-insulatorsemiconductor (EIS) sensor has been applied for the real-time in situ detection of polymer degradation (the benchmark polymer of poly(d,l-lactic acid) (PDLLA) was used as model system) for the first time by the authors [15]. Such EIS sensors are simple in layout, easy and low-cost in fabrication (usually no photolithographic process steps and complicated encapsulation procedures are required).…”

Impedance spectroscopy: A tool for real‐time in situ monitoring of the degradation of biopolymers

“…In preliminary experiments it was ascertained that the thickness of the deposited polymer layers can be controlled by the concentration of the dissolved polymer (see Fig. ) . The thin films were fabricated by dispensing 70 µL polymer solution on the sensor chip at 3000 rpm for 1 min.…”

Monitoring of the Enzymatically Catalyzed Degradation of Biodegradable Polymers by Means of Capacitive Field-Effect Sensors

“…The sensor signal was read-out every 60 min by means of IS in the frequency range of f = 10 0 −10 6 Hz. During these measurements, the EIS structure was biased to the accumulation region by applying a dc potential of V Bias = −2 V to the reference electrode (for a detailed description of the characteristics of a PMEIS sensor, see the work by Schusser et al 21 and Poghossian et al 38 ). To obtain the complex impedance of the polymer-covered sensor, an ac excitation signal of V ac = 20 mV was superimposed to the bias voltage and the current response was measured.…”

“…21 The system allows monitoring of multiple sensors in parallel by simple multiplexing of sensors. This option provides the capability to perform studies on numerous samples in parallel and, thus, to get a more detailed insight into degradation processes and parameters by increasing the throughput of studies with little effort and at low costs.…”