Abdelrazek H. Mousa

Current electrode technologies are too rigid for safe and effective delivery of electrotherapy in the brain, and patients with glioblastoma continue to face a devastating prognosis, with median survival stalled at 15 months despite intensive treatment with surgery, radiation, and chemotherapy. But these conventional approaches potentially compromise immune function, underscoring the urgent need for therapies that activate, rather than suppress, the immune system. Therefore, we introduce injectable conductive hydrogels engineered to match the softness of brain tissue while exhibiting electrical conductivities up to three orders of magnitude higher than any previously reported injectable hydrogels. They can be implanted through minimally invasive syringe capillaries as narrow as 30 µm—avoiding brain tissue damage—and via convection-enhanced delivery (CED) or endovascular catheters, the latter potentially eliminating the need for open brain surgery. Additionally, it can drape a resection cavity to eliminate residual tumor cells. In human glioblastoma tumors in the chicken chorioallantoic membrane model, implantation of the electrode using CED, followed by irreversible electroporation, obliterated tumors within three days. Other injection techniques impaired tumor growth, induced immunogenic cell death, and a robust infiltration of helper and cytotoxic T cells, alongside macrophages, highlighting the immune-activating and tumor-targeting capabilities.

Bioelectronics holds great potential as therapeutics, but introducing conductive structures within the body poses great challenges. While implanted rigid and substrate‐bound electrodes often result in inflammation and scarring in vivo, they outperform the in situ‐formed, more biocompatible electrodes by providing superior control over electrode geometry. For example, one of the most researched methodologies, the formation of conductive polymers through enzymatic catalysis in vivo, is governed by diffusion control due to the slow kinetics, with curing times that span several hours to days. Herein, the discovery of the formation of biocompatible conductive structures through photopolymerization in vivo, enabling spatial control of electrode patterns is reported. The process involves photopolymerizing novel photoactive monomers, 3Es (EDOT‐trimers) alone and in a mixture to cure the poly(3, 4‐ethylenedioxythiophene)butoxy‐1‐sulfonate (PEDOT‐S) derivative A5, resulting in conductive structures defined by photolithography masks. These reactions are adapted to in vivo conditions using green and red lights, with short curing times of 5–30 min. In contrast to the basic electrode structures formed through other in situ methods, the formation of specific and layered patterns is shown. This opens up the creation of more complex 3D layers‐on‐layer circuits in vivo.

Without intervention, cardiac arrhythmias pose a risk of fatality. However, timely intervention can be challenging in environments where transporting a large, heavy defibrillator is impractical, or emergency surgery to implant cardiac stimulation devices is not feasible. Here, we introduce an injectable cardiac stimulator, a syringe loaded with a nanoparticle solution comprising a conductive polymer and a monomer that, upon injection, forms a conductive structure around the heart for cardiac stimulation. Following treatment, the electrode is cleared from the body, eliminating the need for surgical extraction. The mixture adheres to the beating heart in vivo without disrupting its normal rhythm. The electrofunctionalized injectable cardiac stimulator demonstrates a tissue-compatible Young’s modulus of 21 kPa and a high conductivity of 55 S/cm. The injected electrode facilitates electrocardiogram measurements, regulates heartbeat in vivo, and rectifies arrhythmia. Conductive functionality is maintained for five consecutive days, and no toxicity is observed at the organism, organ, or cellular levels.

Bioelectronics can potentially complement classical therapies in nonchronic treatments, such as immunotherapy and cancer. In addition to functionality, minimally invasive implantation methods and bioresorbable materials are central to nonchronic treatments. The latter avoids the need for surgical removal after disease relief. Self-organizing substrate-free organic electrodes meet these criteria and integrate seamlessly into dynamic biological systems in ways difficult for classical rigid solid-state electronics. Here we place bioresorbable electrodes with a brain-matched shear modulus—made from water-dispersed nanoparticles in the brain—in the targeted area using a capillary thinner than a human hair. Thereafter, we show that an optional auxiliary module grows dendrites from the installed conductive structure to seamlessly embed neurons and modify the electrode’s volume properties. We demonstrate that these soft electrodes set off a controlled cellular response in the brain when relaying external stimuli and that the biocompatible materials show no tissue damage after bioresorption. These findings encourage further investigation of temporary organic bioelectronics for nonchronic treatments assembled in vivo.

Organic electrochemical transistors formed by in operando electropolymerization of the semiconducting channel are increasingly becoming recognized as a simple and effective implementation of synapses in neuromorphic hardware. However, very few studies have reported the requirements that must be met to ensure that the polymer spreads along the substrate to form a functional conducting channel. The nature of the interface between the substrate and various monomer precursors of conducting polymers through molecular dynamics simulations is investigated, showing that monomer adsorption to the substrate produces an increase in the effective monomer concentration at the surface. By evaluating combinatorial couples of monomers baring various sidechains with differently functionalized substrates, it is shown that the interactions between the substrate and the monomer precursor control the lateral growth of a polymer film along an inert substrate. This effect has implications for fabricating synaptic systems on inexpensive, flexible substrates.