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Broad applications of electropolymerized conducting polymers (CPs) often prefer thinner soft electrodes to comply with downscaling of the fabrication resolution. However, high conductivity of existing CP films vanishes as thickness decreases to the nanoscale (i.e., below 100 nm), with an unclear mechanism so far. In this study, with an unprecedented family of polypyrrole (PPy) nanofilms that can be easily transferred in a fast and contamination-free manner, we are able to trace the initial development of electrical conductance along with chains' arrangement starting from the very early electrochemical deposition. Our results evidence that the classical nodular polymeric aggregation fundamentally accounts for the persistent losses of interchain connectivity and macroscopic conductivity at a limited thickness. Surprisingly, this seemingly disadvantageous structure can be altered into a large conjugated network to robustly restore the conductivity back to over 80 S cm-1 even below 100 nm, while the controllable formation, growth, and collapse of such networks radically vary the conductivity over a range of 3 orders of magnitude (0.8-129 S cm-1). These observations depict the first physical picture detailing how the long-range conductivity builds up in a growing conjugated network, which opens a route to fast synthesis and diverse applications of such highly conductive CP nanofilms.

One-dimensional zinc oxide (ZnO) nanostructure arrays show unique semiconducting, piezoelectric, and wetting properties, and how they interact with cells is critical for their biomedical applications. In this work, we prepare ZnO nanorod arrays (ZnO NRAs) and study their interactions with neonatal rat cardiomyocytes either as a substrate or patch. We find that ZnO NRAs can (1) inhibit cell adhesion and spreading as a substrate and (2) selectively kill underneath cells as a patch. We further identify surface nanomorphology as the dominant factor responsible for the inhibitory effect. These discoveries suggest potential application of ZnO NRAs as a cell inhibitory biointerface.

Objective Therapeutic intervention for Parkinson's disease (PD) via deep brain stimulation (DBS) represents the current paradigm for managing the advanced stages of the disease in patients when treatment with pharmaceuticals becomes inadequate. Although DBS is the prevailing therapy in these cases, the overall effectiveness and reliability of DBS can be diminished over time due to hardware complications and biocompatibility issues with the electronic implants. To achieve a lifetime solution, we envision that the next generation of neural implants will be entirely "biological" and "autologous", both physically and functionally. Thus, in this study, we set forth toward developing a biological brain pacemaker (BBP) for treating PD. Our focus is to investigate engineering strategies for creating a multicellular biological circuit that integrates innate biological design and function while incorporating principles of neuromodulation to create a biological mechanism for delivering high-frequency stimulation with cellular specificity. Approach We engineer a 3D multicellular circuit design built entirely from biological and biocompatible components using established tissue engineering protocols to demonstrate the feasibility of creating a living neural implant. Furthermore, using 2D co-culture systems, we investigate the physiologically relevant parameters that would be necessary to further develop a therapeutic benefit of high frequency stimulation with cellular specificity within our construct design. Main results Our results demonstrate the feasibility of fabricating a 3D multicellular circuit device in an implantable form. Furthermore, we show we can organize cellular materials to create potential functional connections in normal physiological conditions, thus laying down the foundation of designing a high-frequency pacing system for selective and controlled therapeutic neurostimulation. Significance The findings from this study may lead to the future development of autologous living neural implants that both circumvent the issues inherent in electronic neural implants and form more biocompatible devices with lifelong robustness to repair and restore motor functions, with the ultimate benefit for patients with PD.

Objective Implantable neurotechnologies have revolutionized neuromodulatory medicine for treating the dysfunction of diseased neural circuitry. However, challenges with biocompatibility and lack of full control over neural network communication and function limits the potential to create more stable and robust neuromodulation devices. Thus, we propose a platform technology of implantable and programmable cellular systems, namely Integrated Biocircuits, which use only cells as the functional components of the device. Approach We envision the foundational principles for this concept begins with novel in vitro platforms used for the study and reconstruction of cellular circuitry. Additionally, recent advancements in organoid and 3D culture systems account for microenvironment factors of cytoarchitecture to construct multicellular circuits as they are normally formed in the brain. We explore the current state of the art of these platforms to provide knowledge of their advancements in circuit fabrication and identify the current biological principles that could be applied in designing integrated biocircuit devices. Main results We have highlighted the exemplary methodologies and techniques of in vitro circuit fabrication and propose the integration of selected controllable parameters, which would be required in creating suitable biodevices. Significance We provide our perspective and propose new insights into the future of neuromodulaion devices within the scope of living cellular systems that can be applied in designing more reliable and biocompatible stimulation-based neuroprosthetics.

Zinc oxide (ZnO) nanowires have been widely studied for their applications in electronics, optics, and catalysts. Their semiconducting, piezoelectric, fluorescent, and antibacterial properties have also attracted broad interest in their biomedical applications. Thus, it is imperative to evaluate the biosafety of ZnO nanowires and their biological effects. In this study, the cellular level biological effects of ZnO nanowire arrays are specifically tested on three types of excitable cells, including NG108-15 neuronal cell line, HL-1 cardiac muscle cell line, and neonatal rat cardiomyocytes. Vertically aligned and densely packed ZnO nanowire arrays are synthesized using a solution-based method and used as a substrate for cell culture. The metabolism levels of all three types of cells cultured on ZnO nanowire arrays are studied using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays of a full factorial design. Under the studied settings, the results show statistically significant inhibitory effects of ZnO nanowire arrays on the metabolism of NG108-15 and HL-1 cells in comparison to gold, glass, and polystyrene substrates, and on the metabolism of cardiomyocytes in comparison to gold substrate.