Reproducing the rhythmic electrical activity of the heart in vitro enables researchers to study how cardiomyocytes (CMs) respond to changes in pacing frequency in terms of contraction dynamics, electrical activity, and overall function. While electrical stimulation remains the gold standard, optical stimulation is emerging as a less invasive alternative with superior spatial and temporal resolution. Here, we propose a non-genetic, high-throughput optical platform for the stimulation of CMs cultured on microelectrode arrays, based on Ziapin2, a molecular phototransducer. Importantly, the system also incorporates a laser-based membrane poration module, allowing reliable access to intracellular signals. A user-friendly software was also developed for simultaneous analysis of multiple electrophysiological traces and to streamline data interpretation. Altogether, we propose a fully integrated, minimally invasive powerful platform for in vitro cardiac electrophysiology studies, with promising applications in disease modeling, drug screening, and fundamental research.

Membrane-targeted azobenzenes enable light-based control of membrane-associated cellular processes with high spatiotemporal precision. Their reversible trans-cis isomerization provides tunable control over molecular geometry and polarity, which can modulate cell membrane potential-dependent biological functions. Despite extensive work in eukaryotes, structure-property relationships for membrane-targeted azobenzenes remain largely unexplored in prokaryotes, where membrane electrostatics and the electrical potential component of the proton motive force are tightly coupled to bioenergetics, metabolism, and adaptive responses, including antibiotic susceptibility. Building on our previous finding that the amphiphilic azobenzene Az-2Pyr (also known as ZIAPIN2) inserts into bacterial membranes and elicits a light-driven response distinct from that observed in eukaryotic cells, here we show a comparative study to connect molecular design to photoswitching and bacterial outcomes. We study three amphiphilic azobenzenes with an identical core and a systematic variation in cationic pyridinium arms, from one (Az-1Pyr) to four (2Pyr-2Pyr), to probe the roles of charge density and molecular symmetry. We first characterize their optical properties by steady-state and ultrafast optical spectroscopy, resolving spectral signatures and kinetics of trans-cis photoisomerization. We then quantify bacterial affinity via cellular uptake, lethality, and zeta-potential. Finally, we show that photoswitching combined with bacterial association modulates antibiotic susceptibility.

Optostimulation is rapidly emerging as a promising approach to control cardiac bioelectricity, combining minimal invasiveness with unparalleled spatiotemporal precision and reversibility. Building on previous findings demonstrating that Ziapin2, a membrane-targeted molecular photoswitch, can modulate cardiomyocyte electrophysiology upon visible light stimulation, we evaluated its potential to precisely terminate reentry-based arrhythmias. Reentrant activity was induced in aligned laminar cardiac microtissues from human-induced pluripotent stem-cell-derived cardiomyocytes (hiPSC-CMs), using an S1S2 electrical pacing protocol in wild-type tissues and rapid pacing combined with catecholamine exposure in gene-edited microtissues harboring the CPVT-associated S404R variant in the RYR2 gene. Photostimulation disrupted spiral wave dynamics in Ziapin2-loaded tissues, whereas it had no effect on vehicle-treated controls. These results provide proof of principle for Ziapin2-mediated optotermination of arrhythmias and highlight its potential as a precise, non-genetic, and minimally invasive strategy for arrhythmia modulation.

Carbon atomic wires (CAWs), linear one-dimensional carbon nanostructures, are attracting increasing attention in materials science due to their remarkable electrical, mechanical, optical, and transport properties, which make them promising candidates for being the next generation supercapacitors, batteries, hydrogen storage, organic semiconductors, and active optical elements. However, their intrinsic instability currently hinders their practical implementation. Previous studies have shown that CAWs mainly degrade through crosslinking interactions, exposure to high temperatures, hydrogenation and oxidation. Furthermore, a clear relationship between the wire structure, solvent polarity, and stability has been observed, with longer wires and more polar solvents reducing CAWs stability, while terminal groups strongly influence the degradation processes. Despite this, the photodegradation kinetics has not yet been fully and systematically investigated. Gaining such understanding is of fundamental importance for the rational design of CAWs-based materials for optoelectronic applications where light exposure is inevitable. In this work, we introduce a synchrotron-based approach that enables precise photoexcitation of CAWs with different chemical structures, tuned in resonance with their characteristic absorption vibronic peaks in the UV. This UV resonance Raman approach allows real-time monitoring of photodegradation directly through the time evolution of Raman spectra of each wire. We compare the photostability in different environments (i.e., acetonitrile, water, and aqueous colloidal silver nanoparticle dispersions), focusing on the role of two key structural parameters—sp-carbon chain length and terminal functional groups—in controlling the stabilization of these systems.

Dynamic bioelectric signalling in bacteria regulates physiology and collective behaviours, yet tools to perturb microbial membrane voltage with high spatiotemporal control remain limited. Here we introduce MTP2, a non-genetic, membrane-targeting azobenzene photoswitch that enables optical modulation of bacterial membrane potential by tuning interfacial electrostatics in Bacillus subtilis. MTP2 associates strongly with the cell envelope and shifts the resting potential to more negative values in the dark, while 470-nm illumination evokes a robust, reversible depolarization at the single-cell level. Although MTP2 photoisomerization is ultrafast (picoseconds), the voltage waveforms unfold over seconds to minutes, indicating that the response is set by homeostatic ion transport rather than by MTP2 photochemistry. Genetic and pharmacological perturbations show that K⁺ conductance, Cl⁻-sensitive pathways, and active transport reshape the amplitude, kinetics and even polarity of the optical response, revealing a context-dependent interplay between a passive molecular perturbation and endogenous bioelectric circuitry. As a functional proof of concept, kanamycin efficacy co-varies with the optically tuned voltage state. Together, these results establish MTP2 as a reversible chemical optostimulator for probing and controlling microbial electrophysiology. ### Competing Interest Statement The authors have declared no competing interest. European Research Council, https://ror.org/0472cxd90, 101115925 University of Warwick Research Development Fund Strategic Award, RPG-2024-327

Correction for 'Electrospun polymeric scaffolds enable 3D tissue-like functionality and efficient photoinduced contraction' by Giulia Simoncini et al., J. Mater. Chem. B, 2026, 14, 2832-2842, https://doi.org/10.1039/D5TB02640G.

Preventing contact with pathogens is a critical requirement in filtration applications for both public and private environments. Developing antibacterial membranes is essential to enhance protection and mitigate contamination risks. In this work, a direct comparative study of two silver-based functionalization strategies applied to electrospun polyvinyl alcohol (PVA) nanofiber membranes is presented, aiming to identify the most effective approach for producing durable antibacterial filters. The first method involves in-fiber incorporation of silver nanoparticles (AgNPs) by electrospinning a colloidal AgNP dispersion blended with the PVA solution, followed by crosslinking. The second method uses physical vapor deposition (PVD) to deposit a silica- or zirconia-based composite coating embedding silver nanoclusters onto pre-crosslinked PVA fibers. Both types of membranes were characterized at each processing stage. Morphological changes were assessed by FESEM and image analysis, surface wettability by contact angle measurements, and silver content by EDS. Antibacterial activity was tested against both Gram-positive and Gram-negative bacteria, while silver ion release in water was monitored to evaluate the ability of the inorganic matrix to control Ag+ leaching.The results show that, although both strategies confer antibacterial properties, the PVD-based coating provides a more uniform silver surface distribution, controlled and sustained silver release, and preservation of nanofiber morphology, making it a promising route for the fabrication of high-performance antibacterial membranes.

Abstract This study yields a comprehensive nanoscale investigation of the composition and molecular orientation of electrospun poly(methyl methacrylate) (PMMA) nanofibers containing halogen-terminated carbon atomic wires (CAWs), a finite-length analog of the carbyne construct. This is accomplished by conducting light-polarization-dependent experiments with advanced techniques such as atomic force microscopy-infrared spectroscopy (AFM-IR), optical photothermal infrared microscopy (O-PTIR), and hyperspectral photoluminescence (PL) microscopy. In PMMA nanofibers, AFM-IR reveals a remarkable, homogeneous uniaxial orientation of PMMA chains along the fiber axis, down to the ≈ 20 nm scale. Semi-quantitative analysis of IR dichroic ratios indicates a nearly orthogonal alignment ( $$\:{\psi\:}_{avg}\approx\:\:79^\circ\:$$ ) of the C = O dipole with respect to the nearly all-trans planar polymer backbone, consistent with expectations of the electrospinning process and in agreement with prior modeling of polymer chain dynamics. Congruous AFM-IR, O-PTIR, and hyperspectral PL data show that incorporation of CAWs into the PMMA nanofibers results in a peculiar compositional heterogeneity, with alternating 3 μm to 4 μm long PMMA-rich and CAW-rich regions across the fiber length. Notably, hyperspectral PL data reveal that CAWs preferentially align along the fiber axis, with sparse, 1.5 μm to 3 μm long domains displaying locally reduced or enhanced molecular orientation. We envision that the widely applicable approach used here will foster engineering of anisotropic nanostructures with advanced functionalities and complex compositions, laying the groundwork for future applications in nanoelectronics, photonics, and energy storage that demand anisotropic molecular orientation and composition.

Optical stimulation is emerging as a promising alternative to conventional methods for both research and therapeutic purposes due to its advantages, such as reduced energy consumption, minimal invasiveness, and exceptional spatial and temporal precision. Recently, we introduced Ziapin2, a novel light-sensitive azobenzene compound, as a tool to modulate cardiac cell excitability and contractility. The molecule proved to be effective in precisely regulating the excitation-contraction coupling process in both hiPS-derived cardiomyocytes and adult mouse ventricular myocytes (AMVMs). Experimental evidence suggests that stretch-activated channels (SACs) contribute to light-driven action potential (AP) generation, but the exact way this takes place remains unknown due to system complexity and lack of specific SAC blockers. Here, we aim to clarify the role of SACs and photostimulation mechanism by exploiting a computational model of murine AP that incorporates: 1) the variation in membrane capacitance resulting from the trans-cis isomerization of the molecule in response to light stimulation and 2) SACs activated by membrane tension due to the thickness variation induced by Ziapin2. Our numerical model accurately reproduces cell capacitance and membrane potential alterations induced by Ziapin2 photoisomerization. In addition, it elucidates the behavior observed experimentally in vitro in AMVMs, highlighting the pivotal role of calcium (Ca2+)-selective SACs in AP generation. The proposed model is thus a valid tool for cell behavior prediction in future experiments.

N-doped polymer semiconductors are of great interest in the field of organic thermoelectrics, as high-conductive materials are still highly desired. In this framework, this paper aims to clarify whether the n-doping of naphthalene diimide-bithiophene copolymer, P(NDI2OD-T2), by 1H-benzimidazoles is a thermally activated process. The study interestingly demonstrates that a relevant change in conductivity, with an increase of more than three orders of magnitude with respect to pristine P(NDI2OD-T2), occurs before the annealing process takes place, thus revealing that benzimidazole-derived dopants are already active at room temperature. Moreover, despite the annealing time and temperature affecting the electrical conductivity of the system, their contribution is less relevant, with the increase of electrical conductivity limited to up to three times. The results from the electrical characterization of the samples are supported by infrared spectroscopy investigation and X-ray analysis, revealing the marker bands of polaron and a manifest structural change between the undoped and the just-doped P(NDI2OD-T2) films, accompanied by only minor modifications during the annealing process. Finally, based on the results of density functional theory simulations, the conformational modifications of the 1H-benzimidazole dopant molecules, induced by the interaction with the P(NDI2OD-T2), are proposed as a possible mechanism explaining the effective doping at room temperature.

In vitro cardiac microphysiological models are highly reliable for scientific research, drug development, and medical applications. Although widely accepted by the scientific community, these systems are still limited in longevity due to the absence of non-invasive stimulation techniques. Phototransducers provide an efficient stimulation method, offering a wireless approach with high temporal and spatial resolution while minimizing invasiveness in stimulation processes. In this manuscript, we present a fully optical method for stimulating and detecting the activity of an in vitro cardiac microphysiological model. Specifically, we fabricated engineered laminar anisotropic tissues by seeding human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated in a 3D bioreactor suspension culture. We employed a phototransducer, an amphiphilic azobenzene derivative, named Ziapin2, for stimulation and a Ca2+ dye (X-Rhod 1) for monitoring the system's response. The results demonstrate that Ziapin2 can photomodulate Ca2+ responses in the employed system without compromising tissue integrity, viability, or behavior. Furthermore, we showed that the light-based stimulation approach offers a similar resolution compared to electrical stimulation, the current gold standard. Overall, this protocol opens promising perspectives for the application of Ziapin2 and material-based photostimulation in cardiac research.

In vitro cardiac microphysiological models are highly reliable for scientific research, drug development, and medical applications. Although widely accepted by the scientific community, these systems are still limited in longevity due to the absence of non-invasive stimulation techniques. Phototransducers provide an efficient stimulation method, offering a wireless approach with high temporal and spatial resolution while minimizing invasiveness in stimulation processes. In this manuscript, we present a fully optical method for stimulating and detecting the activity of an in vitro cardiac microphysiological model. Specifically, we fabricated engineered laminar anisotropic tissues by seeding human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) generated in a 3D bioreactor suspension culture. We employed a phototransducer, an amphiphilic azobenzene derivative, named Ziapin2, for stimulation and a Ca2+ dye (X-Rhod 1) for monitoring the system's response. The results demonstrate that Ziapin2 can photomodulate Ca2+ responses in the employed system without compromising tissue integrity, viability, or behavior. Furthermore, we showed that the light-based stimulation approach offers a similar resolution compared to electrical stimulation, the current gold standard. Overall, this protocol opens promising perspectives for the application of Ziapin2 and material-based photostimulation in cardiac research.

Carbon atomic wires (CAWs) are one-dimensional (1D) sp-carbon nanostructures with remarkable electronic, mechanical, and optical properties, but their instability limits their practical applications. Embedding them in solid matrices can enhance their stability. This work reports the first example of electrospun nanofibers embedding halogenated CAWs. A solution of poly-(methyl methacrylate) and CAWs in N,N-dimethylformamide was electrospun using various parameters to investigate the effects on fiber morphology and diameter. Halogenated CAWs were successfully incorporated with a minimal morphological impact. Raman spectroscopy confirmed effective embedding and CAWs stability during electrospinning. The halogenated CAWs showed resistance to degradation for at least six months and demonstrated enhanced thermal stability when embedded within nanofibers. Additionally, our work investigated the influence of different halogen terminations on the degradation kinetics of CAWs upon exposure to these conditions. Similarly, photodegradation studies revealed improved photostability within fibers and demonstrated how CAWs chemical structure affects degradation pathways, including possible homolytic C-X bond cleavage. This work introduces electrospun nanofibers as a novel platform for stabilizing CAWs, offering advantages over thin films, such as better homogeneity, larger surface area, and comparable stability. These findings open new perspectives for CAWs-based nanocomposites in electronics, electrochemistry, and energy-related applications.

The lack of effective therapies for visual restoration in Retinitis pigmentosa and macular degeneration has led to the development of new strategies, such as optogenetics and retinal prostheses. However, visual restoration is poor due to the massive light-evoked activation of retinal neurons, regardless of the segregation of visual information in ON and OFF channels, which is essential for contrast sensitivity and spatial resolution. Here, we show that Ziapin2, a membrane photoswitch that modulates neuronal capacitance and excitability in a light-dependent manner, is capable of reinstating, in mouse and rat genetic models of photoreceptor degeneration, brisk and sluggish ON, OFF, and ON-OFF responses in retinal ganglion cells evoked by full-field stimuli, with reactivation of their excitatory and inhibitory conductances. Intravitreally injected Ziapin2 in fully blind rd10 mice restores light-driven behavior and optomotor reflexes. The results indicate that Ziapin2 is a promising molecule for reinstating physiological visual responses in the late stages of retinal degeneration. Here authors demonstrate Ziapin2, a membrane-targeted photoswitch, reinstates physiological ON/OFF light responses in retinal ganglion cells from degenerate retinas, and restores light-driven behavior and optomotor reflexes in fully blind rd10 mice.

Adaptive optics (AO) has transformed the understanding of biology and medicine by providing unprecedented access to their fundamental elements. This technology leverages techniques and strategies originally developed in astronomy to measure and correct optical aberrations. Herein, the development of a novel photo‐responsive optical material for AO applications is presented. The material consists of a photochromic film of a zirconia‐based hybrid organic–inorganic (HOI) matrix that incorporates up to 20% dithienylethene molecules. The exceptional photochromic properties and thermal stability of the photochromic component, combined with the remarkable optical properties, adjustable thickness, and high dye‐loading capacity of the HOI sol–gel matrix, enable the creation of a system optimized for refractive index modulation (Δn) under light exposure. Comprehensive evaluations of the photochromic material are conducted, analyzing changes in optical properties in response to varying light intensity and exposure time. Additionally, prototypes of focusable adaptive lenses specifically designed for operation in the near‐infrared spectrum are engineered, achieving a significant Δn of 0.0314, effectively minimizing efficiency losses attributable to material absorption.

We introduce a family of membrane-targeted azobenzenes (MTs) with a push-pull character as a new tool for cell stimulation. These molecules are water soluble and spontaneously partition in the cell membrane. Upon light irradiation, they isomerize from trans to cis, changing the local charge distribution and thus stimulating the cell response. Specifically, MTs photoisomerization induces clear and reproducible depolarization. The most promising species, MTP2, was extensively studied. Time-resolved spectroscopy techniques provide insights into the excited state evolution and a complete understanding of its isomerization reaction. Molecular Dynamics simulations reveal the spontaneous and stable partitioning of the compound into the cellular membrane, without significant alterations to the bilayer thickness. MTP2 was tested in different cell types, including HEK293T cells, primary neurons, and cardiomyocytes, and a steady depolarization is always recorded. The observed membrane potential modulation in in-vitro models is attributed to the variation in membrane surface charge, resulting from the light-driven modulation of the MT dipole moment within the cell membrane. Additionally, a developed mathematical model successfully captures the temporal evolution of the membrane potential upon photostimulation. Despite being insufficient for triggering action potentials, the rapid light-induced depolarization holds potential applications, particularly in cardiac electrophysiology. Low-intensity optical stimulation with these modulators could influence cardiac electrical activity, demonstrating potential efficacy in destabilizing and terminating cardiac arrhythmias. We anticipate the MTs approach to find applications in neuroscience, biomedicine, and biophotonics, providing a tool for modulating cell physiology without genetic interventions.

Bacterial persistence and resistance to antibiotics pose critical challenges in healthcare and environmental contexts. Recent studies revealing that bacteria possess a dynamic electrical membrane potential open new avenues for influencing bacterial behaviour and drug susceptibility. In this work, we present a novel light-responsive strategy to modulate bacterial antibiotic persistence using Ziapin2, an azobenzene photoswitch previously shown to alter bacterial membrane potential. We selected two broad-spectrum antibiotics with distinct modes of action: Kanamycin, which requires cytosolic uptake to inhibit protein synthesis, and Ampicillin, which targets cell wall polymerization at the cell envelope, to probe the role of membrane potential in antibiotic efficacy. Our findings show that when Bacillus subtilis is exposed to Kanamycin and Ziapin2, photoactivation (470 nm) significantly impacts bacterial viability: under illumination, the previously lethal effects of Kanamycin are markedly reduced, suggesting that membrane potential changes drive altered antibiotic uptake or intracellular accumulation. In contrast, Ampicillin-treated samples remain largely unaffected by light-induced membrane modulation, consistent with its action at the external cell envelope. Taken together, these results indicate that membrane potential manipulation can selectively influence the activity of antibiotics whose intracellular uptake is critical to their function. This proof-of-concept study underscores the potential of non-genetic, light-based interventions to modulate bacterial susceptibility in real time. Future work will expand this approach by exploring additional antibiotic classes and novel azobenzene derivatives, ultimately advancing our understanding of bacterial bioelectric regulation and its applications in antimicrobial therapies.