Bioelektronické materiály a systémy
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- ItemHow to Achieve High Spatial Resolution in Organic Optobioelectronic Devices?(WILEY, 2025-05-01) Fabbri, Luca; Migliaccio, Ludovico; Širvinskyt, Aleksandra; Rizzi, Giacomo; Bondi, Luca; Tamarozzi, Cristiano; Weber, Stefan A.L.; Fraboni, Beatrice; Glowacki, Eric Daniel; Cramer, TobiasLight activated local stimulation and sensing of biological cells hold great promise for minimally invasive bioelectronic interfaces. Organic semiconductors are particularly appealing for these applications due to their optoelectronic properties and biocompatibility. This study examines the material properties necessary to localize the optical excitation and achieve optoelectronic transduction with high spatial resolution. Using photovoltage and photocurrent microscopy, we investigate spatial broadening of local optical excitation in Phthalocyanine/3,4,9,10-Perylenetetracarboxylic diimide (H2PC/PTCDI) planar heterojunctions. Our measurements reveal that resolution losses are tied to the effective diffusion length of charge carriers at the heterojunction. For the H2PC/PTCDI heterojunction, the diffusion length is determined to be lambda d = 1.5 +/- 0.1 mu m, attributed to reduced carrier mobility. Covering the heterojunction with poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) improves the charge generation performance but increases the carrier diffusion length to lambda d = 7.0 +/- 0.3 mu m due to longer lifetime and higher carrier mobility. These findings elucidate the physical mechanisms underlying transduction and provide design principles for organic semiconductor devices aimed at achieving high efficiency and high spatial resolution for wireless and optically activated bioelectronics.
- ItemEngineering Conductive Hydrogels with Tissue-like Properties: A 3D Bioprinting and Enzymatic Polymerization Approach(WILEY, 2024-11-01) Li, Changbai; Naeimipour, Sajjad; Rasti Boroojeni, Fatemeh; Abrahamsson, Tobias; Strakosas, Xenofon; Yi, Yangpeiqi; Rilemark, Rebecka; Lindholm, Caroline; Perla, Venkata K.; Musumeci, Chiara; Li, Yuyang; Biesmans, Hanne; Savvakis, Marios; Olsson, Eva; Tybrandt, Klas; Donahue, Mary; Gerasimov, Jennifer Y.; Selegrd, Robert; Berggren, Magnus; Aili, Daniel; Simon, Daniel T.Hydrogels are promising materials for medical devices interfacing with neural tissues due to their similar mechanical properties. Traditional hydrogel-based bio-interfaces lack sufficient electrical conductivity, relying on low ionic conductivity, which limits signal transduction distance. Conducting polymer hydrogels offer enhanced ionic and electronic conductivities and biocompatibility but often face challenges in processability and require aggressive polymerization methods. Herein, we demonstrate in situ enzymatic polymerization of pi-conjugated monomers in a hyaluronan (HA)-based hydrogel bioink to create cell-compatible, electrically conductive hydrogel structures. These structures were fabricated using 3D bioprinting of HA-based bioinks loaded with conjugated monomers, followed by enzymatic polymerization via horseradish peroxidase. This process increased the hydrogels' stiffness from about 0.6 to 1.5 kPa and modified their electroactivity. The components and polymerization process were well-tolerated by human primary dermal fibroblasts and PC12 cells. This work presents a novel method to fabricate cytocompatible and conductive hydrogels suitable for bioprinting. These hybrid materials combine tissue-like mechanical properties with mixed ionic and electronic conductivity, providing new ways to use electricity to influence cell behavior in a native-like microenvironment. This study introduces a novel method to enhance hydrogel conductivity and biocompatibility for biomedical applications. By using in situ enzymatic polymerization of pi-conjugated monomers within a hyaluronan-based hydrogel bioink, followed by 3D bioprinting, the resulting hydrogels exhibit improved stiffness, electroactivity, and cytocompatibility. These conductive hydrogels provide a versatile platform for advanced 3D cell culture and neural engineering.image (c) 2024 WILEY-VCH GmbH
- ItemShattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodes(AMER CHEMICAL SOC, 2024-10-01) Ehlich, Jiří; Vašíček, Čeněk; Dobeš, Jan; Ruggiero, Amedeo; Vejvodová, Markéta; Glowacki, Eric DanielIt is generally accepted that for safe use of neural interface electrodes, irreversible faradaic reactions should be avoided in favor of capacitive charge injection. However, in some cases, faradaic reactions can be desirable for controlling specific (electro)physiological outcomes or for biosensing purposes. This study aims to systematically map the basic faradaic reactions occurring at bioelectronic electrode interfaces. We analyze archetypical platinum-iridium (PtIr), the most commonly used electrode material in biomedical implants. By providing a detailed guide to these reactions and the factors that influence them, we offer a valuable resource for researchers seeking to suppress or exploit faradaic reactions in various electrode materials. We employed a combination of electrochemical techniques and direct quantification methods, including amperometric, potentiometric, and spectrophotometric assays, to measure O-2, H-2, pH, H2O2, Cl-2/OCl-, and soluble platinum and iridium ions. We compared phosphate-buffered saline (PBS) with an unbuffered electrolyte and complex cell culture media containing proteins. Our results reveal that the "water window" the potential range without significant water electrolysis varies depending on the electrolyte used. In the culture medium that is rich with redox-active species, a window of potentials where no faradaic process occurs essentially does not exist. Under cathodic polarizations, significant pH increases (alkalization) were observed, while anodic water splitting competes with other processes in media, preventing prevalent acidification. We quantified the oxygen reduction reaction and accumulation of H2O2 as a byproduct. PtIr efficiently deoxygenates the electrolyte under low cathodic polarizations, generating local hypoxia. Under anodic polarizations, chloride oxidation competes with oxygen evolution, producing relatively high and cytotoxic concentrations of hypochlorite (OCl-) under certain conditions. These oxidative processes occur alongside PtIr dissolution through the formation of soluble salts. Our findings indicate that the conventional understanding of the water window is an oversimplification. Important faradaic reactions, such as oxygen reduction and chloride oxidation, occur within or near the edges of the water window. Furthermore, the definition of the water window significantly depends on the electrolyte composition, with PBS yielding different results compared with culture media.
- ItemLight-Controlled Electric Stimulation with Organic Electrolytic Photocapacitors Achieves Complex Neuronal Network Activation: Semi-Chronic Study in Cortical Cell Culture and Rat Model(Wiley, 2024-08-13) Nowakowska, Marta; Jakešová, Marie; Schmidt, Tony; Opančar, Aleksandar; Polz, Mathias; Reimer, Robert; Fuchs, Julia; Patz, Silke; Ziesel, Daniel; Scheruebel, Susanne; Kornmueller, Karin; Rienmüller, Theresa; Derek, Vedran; Glowacki, Eric Daniel; Schindl, Rainer; Üçal, MuammerNeurostimulation employing photoactive organic semiconductors offers an appealing alternative to conventional techniques, enabling targeted action and wireless control through light. In this study, organic electrolytic photocapacitors (OEPC) are employed to investigate the effects of light-controlled electric stimulation on neuronal networks in vitro and in vivo. The interactions between the devices and biological systems are characterized. Stimulation of primary rat cortical neurons results in an elevated expression of c-Fos within a mature neuronal network. OEPC implantation for three weeks and subsequent stimulation of the somatosensory cortex leads to an increase of c-Fos in neurons at the stimulation site and in connected brain regions (entorhinal cortex, hippocampus), both in the ipsi- and contralateral hemispheres. Reactivity of glial and immune cells after semi-chronic implantation of OEPC in the rat brain is comparable to that of surgical controls, indicating minimal foreign body response. Device functionality is further substantiated through retained charging dynamics following explantation. OEPC-based, light-controlled electric stimulation has a significant impact on neural responsiveness. The absence of detrimental effects on both the brain and device encourages further use of OEPC as cortical implants. These findings highlight its potential as a novel mode of neurostimulation and instigate further exploration into applications in fundamental neuroscience. Wireless cortical stimulation is an attractive alternative to standard neurostimulation methods. Organic photoactive semiconductors can transduce light into electric signal, even in ultrathin layers, which can be used to stimulate neurons. In this study, light-based stimulation activated complex neuronal networks in vitro and in vivo, including deep brain regions. The devices proved safe and stable over three weeks of implantation. image
- ItemChoosing the right electrode representation for modeling real bioelectronic interfaces: a comprehensive guide(IOP Publishing, 2024-08-01) Opančar, Aleksandar; Glowacki, Eric Daniel; Derek, VedranObjective. Producing realistic numerical models of neurostimulation electrodes in contact with the electrolyte and tissue, for use in time-domain finite element method simulations while maintaining a reasonable computational burden remains a challenge. We aim to provide a straightforward experimental-theoretical hybrid approach for common electrode materials (Ti, TiN, ITO, Au, Pt, IrOx) that are relevant to the research field of bioelectronics, along with all the information necessary to replicate our approach in arbitrary geometry for real-life experimental applications. Approach. We used electrochemical impedance spectroscopy (EIS) to extract the electrode parameters in the AC regime under different DC biases. The pulsed electrode response was obtained by fast amperometry (FA) to optimize and verify the previously obtained electrode parameters in a COMSOL Multiphysics model. For optimization of the electrode parameters a constant phase element (CPE) needed to be implemented in time-domain. Main results. We find that the parameters obtained by EIS can be used to accurately simulate pulsed response only close to the electrode open circuit potential, while at other potentials we give corrections to the obtained parameters, based on FA measurements. We also find that for many electrodes (Au, TiN, Pt, and IrOx), it is important to implement a distributed CPE rather than an ideal capacitor for estimating the electrode double-layer capacitance. We outline and provide examples for the novel time-domain implementation of the CPE for finite element method simulations in COMSOL Multiphysics. Significance. An overview of electrode parameters for some common electrode materials can be a valuable and useful tool in numerical bioelectronics models. A provided FEM implementation model can be readily adapted to arbitrary electrode geometries and used for various applications. Finally, the presented methodology for parametrization of electrode materials can be used for any materials of interest which were not covered by this work.