Flexible, biocompatible electronic materials and semiconductors are wanted to create a novel generation of bioelectronic interfaces. Such interfaces will be at the heart of future medical devices that allow to record and stimulate in a low-invasive manner from the central and peripheral nervous system or to transduce directly biochemical signals. In our research we investigate in detail the material properties and the underlying physics of novel material candidates for bioelectronic interfaces. The experiments provide us the necessary knowledge to propose novel transducer concepts that could help to improve the interface between the worlds of biological cells and microelectronics.
We structure our research into three basic activities:
Conducting polymers are promising materials for tissue engineering applications, since they can both provide a soft biocompatible scaffold for physical support of living cells and ion-to-electron trasduction to electrically interact with cells.
In order to investigate the microscopic mechanisms of interaction between living cells and semiconductor surfaces we perform in-vitro experiments. In these experiments cell-cultures are plated onto nano-structured electrical surfaces fabricated in our lab and we perform a series of experiments to probe the transduction of signals between cells and these electronic surfaces. For example, we are interested to investigate how the porperties of the conducting polymer surface can influence the cells adehsion and growth as shown in the image on the left.
When patterning the organic semiconductor in a transistor configuration it becomes also possible to employ the electronic signals to continuously monitor the cellular tissue coverage and its response to toxic agents.
Organic semiconductors are also easy to excite with light. The optically generated electrical excitation can be further transduced to stimulate cells and impact on their phenotype. Such an interaction paves the way to organic opto-bioelectronic devices that we are investigating.
Organic electrochemical transistors (OECT) have been proposed as biosensors for redox-active biomolecules. In the OECTs sensors the current flowing in the organic channel can be modulated through the voltage applied to the gate electrode by electrochemical reactions that take place in an electrolytic solution. Since the device is the combination of a sensitive element and an amplifier, OECTs directly amplify the electro-chemical signals of various redox active bio molecules.
In our reserach group we fabricate and investigate the performance of OECT sensors modifyng the transistor geometries and organic materials properties and functionalization. We developed all-plastic planar OECT sensor for detection of several redox-active biomolecules: Dopamine, Ascorbic Acid, Adrenaline, Uric Acid, pH, Cl- ions.
Moreover, we explored a new approach to selectively identify and determine the contributions of different analytes to the OECT electrical output signal through a potentiodynamic approach, by varying the operating gate voltage and the scan rate.
Soft bioelectronic devices that interface non-invasively neuronal tissue are expected to open an enormous potential for novel medical therapies. However, the technology encounters currently a fundamental limit as a compromise between mechanical stability and the medical invasiveness has to be found: Bioelectronics interfaces should match the soft elastic properties of the tissue where they are embedded (E < 1 MPa). Missing compliance with the low elastic modulus of tissue leads on the long-term to inflammation, scar formation and passivation. However, bio-electronic implants rely on patterned microelectronic structures made of more rigid electronic materials for signal recording and stimulation. The resulting mismatch in mechanical properties imposed by the requirement of a soft substrate combined with electrical functional rigid elements makes bio-electronic microelectrodes prone to stress induced mechanical failure and does not allow any further miniaturization and reduction in invasiveness.
To overcome the fundamental limitations in the engineering of soft, multi-component microelectronic devices, our group investigates novel materials and device architectures that combine soft mechanical behaviour with stable electronic performance. We employ a wide range of macroscopic and microscopic technics to decipher the combined electromechanical effects relevant for bioelectronic interfaces.
Recent related publications
Mariani F, Gualandi I, Tessarolo M, Fraboni B, Scavetta E PEDOT: Dye-Based, Flexible Organic Electrochemical Transistor for Highly Sensitive pH Monitoring. ACS Applied Materials & Interfaces. 2018 Jun 19.
Fabrizio Amorini; Isabella Zironi; Marco Marzocchi; Isacco Gualandi; Maria Calienni; Tobias Cramer; Beatrice Fraboni; Gastone Castellani, Electrically Controlled “Sponge Effect” of PEDOT:PSS Governs Membrane Potential and Cellular Growth, ACS Applied Materials & Interfaces, 2017, 9, pp. 6679 - 6689