Publications

Cable bacteria are filamentous, multicellular microorganisms that display an exceptional form of biological electron transport across centimeter-scale distances. Currents are guided through a network of nickel-containing protein fibers within the cell envelope. Still, the mechanism of long-range conduction remains unresolved. Here, we characterize the conductance of the fiber network under dry and wet, physiologically relevant, conditions. Our data reveal that the fiber conductivity is high (median value: 27 S cm-1; range: 2 to 564 S cm-1), does not show any redox signature, has a low thermal activation energy (Ea = 69 +/- 23 meV), and is not affected by humidity or the presence of ions. These features set the nickel-based conduction mechanism in cable bacteria apart from other known forms of biological electron transport. As such, conduction resembles that of an organic semi-metal with a high charge carrier density. Our observation that biochemistry can synthesize an organometal-like structure opens the way for novel bio-based electronic technologies.

JTD Keywords: 'current, Activation energy, Bacteria, Bioelectronic, Bioelectronics, Cable bacteria, Cables, Centimeter-scale, Electrochemical impedance spectroscopy, Electrochemical-impedance spectroscopies, Electron transport, Electron transport properties, Electron-transport, Long -distance electron transport, Long-distance electron transport, Microbial nanowires, Nickel, Nickel containing, Protein conductivity, Protein fibers, Proteins, Sulfur

Organic electronic materials offer an untapped potential for novel tools for low-invasive electrophysiological recording and stimulation devices. Such materials combine semiconducting properties with tailored surface chemistry, elastic mechanical properties and chemical stability in water. In this work, we investigate solution processed Electrolyte Gated Organic Field Effect Transistors (EGOFETs) based on a small molecule semiconductor. We demonstrate that EGOFETs based on a blend of soluble organic semiconductor 2,8-Difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) combined with an insulating polymer show excellent sensitivity and long-term recording under electrophysiological applications. Our devices can stably record the extracellular potential of human pluripotent stem cell derived cardiomyocyte cells (hPSCs-CMs) for several weeks. In addition, cytotoxicity tests of pharmaceutical drugs, such as Norepinephrine and Verapamil was achieved with excellent sensitivity. This work demonstrates that organic transistors based on organic blends are excellent bioelectronics transducer for extracellular electrical recording of excitable cells and tissues thus providing a valid alternative to electrochemical transistors.

JTD Keywords: Bioelectronics, Cardiac cells, Organic electronics, Organic field effect transistors, Organic semiconducting blend

Emerging nanobiotechnologies can offer solutions to the current and future challenges in medicine. By covering topics from regenerative medicine, tissue engineering, drug delivery, bionanofabrication, and molecular biorecognition, this Special Issue aims to provide an update on the trends in nanomedicine and drug delivery using biomimetic approaches, and the development of novel biologically inspired devices for the safe and effective diagnosis, prevention, and treatment of disease.

JTD Keywords: Bioinspired nanotechnologies, Bionanofabrication, Bio-nano measurement and microscopy, Nanomaterials for biological and medical applications, Nanoassemblies, Nanostructured surfaces, Drug delivery, Nanobioelectronics, Integrated systems/nanobiosensors, Nanotoxicology, Graphene-based applications

Detection of the hybridisation events is of great importance in many different biotechnology applications such as diagnosis, computing, molecular bioelectronics, and among others. However, one important drawback is the low current of some redox reporters that limits their application. This paper demonstrates the powerful features of molecular wires, in particular the case of S-[4-[2-[4-(2-Phenylethynyl)phenyl]ethynyl]phenyl] thiol molecule and the key role that play the nanometric design of the capture probe linkers to achieve an efficient couple of the DNA complementary ferrocene label with the molecular wire for an effective electron transfer in co-immobilised self-assembled monolayers (SAMs) for DNA hybridisation detection. In this article, the length of the linker capture probe was studied for electron transfer enhancement from the ferrocene-motifs of immobilised molecules towards the electrode surface to obtain higher kinetics in the presence of thiolated molecular wires. The use of the right couple of capture probe linker and molecular wire has found to be beneficial as it helps to amplify eightfold the signal obtained.

JTD Keywords: DNA hybridisation, Bioelectronics, Electron transfer rate constant, Molecular wires, Electrochemistry, Ferrocene, Biosensor

Nanogap electrodes have attracted a lot of consideration as promising platform for molecular electronic and biomolecules detection. This is mainly for their higher aspect ratio, and because their electrical properties are easily accessed by current-voltage measurements. Nevertheless, application of standard current-voltages measurements used to characterize nanogap response, and/or to modify specific nanogap electrodes properties, represents an issue. Since the strength of electrical fields in nanoscaled devices can reach high values, even at low voltages. Here, we analyzed the effects induced by different methods of surface modification of nanogap electrodes, in test-voltage application, employed for the electrical detection of a desoxyribonucleic acid (DNA) target. Nanogap electrodes were functionalized with two antisymmetric oligo-probes designed to have 20 terminal bases complementary to the edges of the target, which after hybridization bridges the nanogap, closing the electrical circuit. Two methods of functionalization were studied for this purpose; a random self-assembling of a mixture of the two oligo-probes (OPs) used in the platform, and a selective method that controls the position of each OP at selected side of nanogap electrodes. We used for this aim, the electrophoretic effect induced on negatively charged probes by the application of an external direct current voltage. The results obtained with both functionalization methods where characterized and compared in terms of electrode surface covering, calculated by using voltammetry analysis. Moreover, we contrasted the electrical detection of a DNA target in the nanogap platform either in site-selective and in randomly assembled nanogap. According to our results, a denser, although not selective surface functionalization, is advantageous for such kind of applications.

JTD Keywords: Biosensor bioelectronics, DNA electrophoresis, Nanogap electrodes, Self-assembled monolayers, Site-selective deposition

Switching events in the current flowing through individual redox proteins, (azurin) spontaneously wired between two electrodes, are studied using an electrochemical scanning tunneling microscope (ECSTM). These switching events in the current–time trace are characterized using conductance histograms, and reflect the intrinsic redox thermodynamic dispersion in the azurin population. This conductance switching may pose limitations to miniaturizing redox protein-based devices.

JTD Keywords: Bioelectronics, Protein transistors, Molecular junctions, Switches, STM

A ±1.2V / 350μW integrated front-end architecture for a true/false in-vivo subcutaneous detection device is presented. The detection is focused on using three electrodes amperometric sensors. The powering and AM transcutaneous communication are based on an inductively coupled link working at 13.56 MHz. A prototype device (5.5 mm x 29.5 mm) has been implemented and fully validated.

JTD Keywords: Implantable Device, Front-End architecture, Bioelectronics, Microelectronics Design, Biosensors