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 π‐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.

Morphologically controllable synthesis of Rh nanoparticles (NPs) was achieved by the use of additives during polyol synthesis. The effect of salts and surfactant additives including PVP, sodium acetate, sodium citrate, CTAB, CTAC, and potassium bromide on Rh NPs morphology was investigated. When PVP was used as the only additive, trigonal NPs were obtained. Additives containing Br⁻ ions (CTAB and KBr) resulted in NPs with a cubic morphology, while those with carboxyl groups (sodium citrate and acetate) formed spheroid NPs. The use of Cl⁻ ions (CTAC) resulted in a mixture of polygon morphologies. Cytotoxicity of these NPs was evaluated on macrophages and ovarian cancer cell lines. Membrane integrity and cellular activity are both influenced to a similar extent, for both the cell lines, with respect to the morphology of Rh NPs. The cells exposed to trigonal Rh NPs showed the highest viability, among the NP series. Particles with a mixed polygon morphology had the highest cytotoxic impact, followed by cubic and spherical NPs. The Rh NPs were further demonstrated as contrast agents for X-ray fluorescence computed tomography (XFCT) in a small-animal imaging setting. This work provides a detailed route for the synthesis, morphology control, and characterization of Rh NPs as viable contrast agents for XFCT bio-imaging.

X-Ray fluorescence computed tomography (XFCT) is an emerging biomedical imaging technique, which demands the development of new contrast agents. Ruthenium (Ru) and rhodium (Rh) have spectrally attractive K_α edge energies, qualifying them as new XFCT bio-imaging probes. Metallic Ru and Rh nanoparticles are synthesized by polyol method, in the presence of a stabilizer. The effect of several reaction parameters, including reaction temperature time, precursor and stabilizer concentration, and stabilizer molecular weight, on the size of particles, were studied. Resultant materials were characterized in detail using XRD, TEM, FT-IR, DLS-zeta potential and TGA techniques. Ru particles in the size range of 1–3 nm, and Rh particles of 6–9 nm were obtained. At physiological pH, both material systems showed agglomeration into larger assemblies ranging from 12–104 nm for Ru and 25–50 nm for Rh. Cytotoxicity of the nanoparticles (NPs) was evaluated on macrophages and ovarian cancer cells, showing minimal toxicity in doses up to 50 μg/mL. XFCT performance was evaluated on a small-animal-sized phantom model, demonstrating the possibility of quantitative evaluation of the measured dose with an expected linear response. This work provides a detailed route for the synthesis, size control and characterization of two materials systems as viable contrast agents for XFCT bio-imaging.

One‐dimensional (1D) silver nanowires are promising surface‐enhanced Raman spectroscopy (SERS) substrates, yet their plasmonic hotspots are spatially confined to sharp tips or junctions, leaving the extensive body optically inactive. Additionally, realizing high‐performance Ag‐based substrates faces a fundamental trade‐off between chemical stability and surface activity. To simultaneously resolve these geometric and chemical limitations, we present a stepwise interfacial engineering strategy to synthesize 3D hierarchical dual‐layer porous@smooth Au‐shelled Ag nanowires. This architecture decouples functional requirements: A hermetic smooth Au inner shell passivates the Ag core for long‐term stability, while the nanowire body serves as a structural scaffold for a porous Au outer shell. This design activates the entire 1D surface, creating a volumetric distribution of high‐density hotspots localized at the interparticle gaps. Consequently, the hierarchical nanowires exhibit exceptional sensitivity for model analytes, including malachite green, crystal violet, and methylene blue, with detection limits ranging from 10 ⁻¹¹ down to 10 ⁻¹⁴ M. Notably, for malachite green the sensitivity approaches the single‐molecule regime. Finally, leveraging their high aspect ratio and mechanical flexibility, the nanowires demonstrate versatile utility in two distinct applications: enabling both stretchable SERS substrates for conformal sensing and colloidal dispersions for the rapid “mix‐and‐measure” fingerprinting of microplastics (PE, PP, PS, and PET).