Transistors with tunable transconductance allow high-quality recordings of human brain rhythms.

An organic electrochemical transistor operates in accumulation mode with high transconductance. The channel comprises a thiophene-based conjugated polyelectrolyte, which is p-type doped by anions injected from a liquid electrolyte upon the application of a gate voltage. The use of ethylene glycol as a co-solvent dramatically improves the transconductance and the temporal response of the transistors.

Organic electrochemical transistors are integrated on depth probes to achieve localized electrical stimulation of neurons. The probes feature a mechanical delamination process which leaves only a 4 μm thick film with embedded transistors inside the brain. This considerably reduces probe invasiveness and correspondingly improves future brain-machine interfaces.

In treating epilepsy, the ideal solution is to act at a seizure's onset, but only in the affected regions of the brain. Here, an organic electronic ion pump is demonstrated, which directly delivers on-demand pure molecules to specific brain regions. State-of-the-art organic devices and classical pharmacology are combined to control pathological activity in vitro, and the results are verified with electrophysiological recordings.

Funding Agencies|European Union [602102]; A*MIDEX [A_M-AAP-ID-13-24-130531-16.31-BERNARD-HLS]; Swedish Innovation Office (VINNOVA); Swedish Research Council [621-2011-3517]; Knut and Alice Wallenberg Foundation [2012.0302]; National Science Foundation [DMR-1105253]; ANR [ANR-13-BSV5-0019-01]; Fondation pour la Recherche Medicale [DBS20131128446]; Fondation de lAvenir; Onnesjo Foundation; Region PACA; Microvitae Technologies; Orthogonal, Inc.; Marie Curie Fellowships

A biosensing platform based on an organic transistor circuit for metabolite detection in highly complex biological media is introduced. The sensor circuit provides inherent background subtraction allowing for highly specific, sensitive lactate detection in tumor cell cultures. The proposed sensing platform paves the way toward rapid, label-free, and cost-effective clinically relevant in vitro diagnostic tools.

Lipid bilayers are widely employed as a model system to investigate interactions between cells and their environment. Supported lipid bilayers (SLB) with integrated transmembrane proteins are emerging as a preferred platform for sensing applications. Challenges lie in the generation of SLB on surfaces which allow transduction of signals for characterization of lipid bilayer and incorporated transmembrane proteins. For the first time, the formation of SLBs is shown on films of the conducting polymer, poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS), using traditional methods for characterizing lipid bilayer quality and function (QCM‐D, FRAP) combined with impedance spectroscopy. Further, partial formation of SLBs on PEDOT:PSS based organic electrochemical transistors (OECTs) is successfully demonstrated, as well as the ability to integrate and sense the ion pore α‐hemolysin, confirming the sensitivity of the OECT as a transducer of biological membrane function. This work represents a highly promising first step toward the use of such OECTs for functional readout of transmembrane proteins in their native environment.

Communication between living brain tissue and engineered devices is the key link to understand brain function and restore neurological deficits from disease, injury, and old age. Enabled by new materials and device designs, a new generation of brain interface technologies is replacing bulkier systems, offering lower tissue damage, reduced immunogenicity, and long‐term stability. New electrode materials with improved chronic performance and increasing emphasis on multimodal capabilities are being integrated onto ultraflexible and mechanically compliant architectures. As these scale to smaller dimensions and higher channel counts, the goal of bidirectional, single‐cell interfaces is nearly within reach. However, promising, long‐term reliability, toxicity, and performance of these systems are still largely unknown. Here, the basics of electrode materials and in vivo technologies are reviewed, and recent advances in electronic and ionic materials are highlighted.

Minimally invasive electrodes of cellular scale that approach a bio-integrative level of neural recording could enable the development of scalable brain machine interfaces that stably interface with the same neural populations over long period of time. In this paper, we designed and created NeuroRoots, a bio-mimetic multi-channel implant sharing similar dimension (10µm wide, 1.5µm thick), mechanical flexibility and spatial distribution as axon bundles in the brain. A simple approach of delivery is reported based on the assembly and controllable immobilization of the electrode onto a 35µm microwire shuttle by using capillarity and surface-tension in aqueous solution. Once implanted into targeted regions of the brain, the microwire was retracted leaving NeuroRoots in the biological tissue with minimal surgical footprint and perturbation of existing neural architectures within the tissue. NeuroRoots was implanted using a platform compatible with commercially available electrophysiology rigs and with measurements of interests in behavioral experiments in adult rats freely moving into maze. We demonstrated that NeuroRoots electrodes reliably detected action potentials for at least 7 weeks and the signal amplitude and shape remained relatively constant during long-term implantation. This research represents a step forward in the direction of developing the next generation of seamless brain-machine interface to study and modulate the activities of specific subpopulations of neurons, and to develop therapies for a plethora of neurological diseases. Science AdvancesManuscript Template