MacDiarmid Institute for Advanced Materials and Nanotechnology

The spatial organisation of mechanical cues is increasingly recognised as a key regulator of tissue development and disease, yet in vitro systems capable of replicating such environments remain limited. Fibroblast migration and the fibroblast-to-myofibroblast transition, which affect scar formation, are examples of mechanisms affected by mechanical cues. We report a photolithographic platform that enables precise, spatial patterning of the Young's modulus of gelatin methacryloyl (GelMA) hydrogels, using a ruthenium/sodium persulfate (SPS) photoinitiation system. By altering light intensity, we achieved Young's modulus tunability between 4 kPa and 46 kPa in non-patterned gels. By displaying a binary light intensity pattern over the gel, the Young's modulus could be switched from 10 kPa to 45 kPa, representing healthy and fibrotic Young's moduli, over a distance of ∼20 μm (2.3MPa·mm⁻¹). This system could also generate relatively linear Young's modulus gradients that are more physiologically relevant, ∼10 kPa⋅mm-1. Non-patterned and binary-patterned gels confirmed that increasing the Young's modulus drives the fibroblast-to-myofibroblast transition, observed by significantly greater cell volumes and α-smooth muscle actin (α-SMA) stress fibre formation, from encapsulated cardiac fibroblasts after 7 days. In gradient-patterned gels, fibroblasts exhibited a progressive, modulus-dependent increase in both cell volume and α-SMA stress fibre formation, alongside expressing a durotactic response, moving from healthy to fibrotic environments, and also aligning themselves between ±45 degrees to the Young's modulus gradient. Beyond cardiac fibrosis, this versatile platform enables rapid generation of biologically relevant mechanical landscapes for diverse mechanobiological applications, bridging the gap between simplified, mechanically uniform models and the heterogeneous microenvironments of native tissues. STATEMENT OF SIGNIFICANCE: This study developed a platform for spatially controlling the Young's modulus of GelMA using a digital light projection system. Using this system, a change in Young's modulus from 10 kPa to 45 kPa was achieved with a resolution of 20 µm. Natural Young's modulus gradients observed in tissues (∼10 kPa·mm⁻¹) can also be achieved. The fibroblast-to-myofibroblast transition was controlled spatially in the patterned gels, evidenced by changes in cell volume and α-SMA fibrillation. Fibroblasts demonstrated alignment and migration to the Young's modulus gradient. Our photopatterning system demonstrates ease of pattern/gradient definition with adaptability to a diverse range of systems, highlighting the impact of mechanical properties on cardiac scar formation, offering avenues for studying these effects.

This chapter discusses the use of emission and resonance Raman spectroscopies to provide insight into excited states within transition metal polypyridyl complexes. The types of excited states present in metal complexes are described, including intra-ligand charge-transfer (ILCT) excited states. Emission spectroscopy is briefly discussed followed by a more in-depth description of the theory of resonance Raman spectroscopy, including sum-over-states and wave packet models. The use of computational methods is described including predictions of resonance Raman spectra. Time-resolved resonance Raman spectroscopy is discussed along with spectroelectrochemistry. A number of examples from the recent literature are provided and then a few specific case studies that use the aforementioned techniques are described to highlight the successes and limitations of these methods, scaling from straightforward analyses to more complex and ambiguous systems.

In a sustainable economy built on renewable energy, hydrogen plays a key role for storing energy and replacing fossil fuels. An efficient way to store hydrogen is to keep it in the solid state by binding it chemically in a metal hydride, which is particularly useful for seasonal energy storage or for applications where safety is a concern. Since experimental studies with hydrogen can be challenging and time-consuming, computational tools are extremely valuable for gaining a deeper understanding of the processes underlying the (de-)hydrogenation reaction. In this seminar, I will highlight our recent work on predicting the thermodynamics, interface energies, and volume expansion of metal-hydrogen systems using different computational methods. We leverage available experimental and computational data to build machine learning models as well as more sophisticated thermodynamic models for the calculation of phase diagrams (CALPHAD) to find novel metal hydride compositions and fine-tune existing alloys. Additionally, atomic-scale calculations based on density functional theory (DFT) are employed to model interfaces between the metal and hydride phases to inform meso-scale models and gain insights into nucleation barriers. As hydrogen is the lightest element of the periodic table, we also perform simulations that go beyond the classical approximation and test what happens if we treat the whole hydrogen atom as a quantum object instead.

The electronic properties of the lanthanide nitrides are slowly yielding to experimental and theoretical probes. In this work the electronic, optical, and vibrational properties of stoichiometric and nitrogen vacancy doped ErN are studied using density functional theory with empirically-determined Hubbard parameter corrections. We report the band structure, finding that the material can be doped with electrons similar to other lanthanide nitrides. We discuss the effects of the dopant electrons on the optical and vibrational properties of the material in the context of application in optoelectronics. We find that limiting nitrogen vacancy defects in ErN is essential for retaining transparency at 0.81 eV, a technologically useful infrared intra-4ftransition, used for light emission in telecommunication. This work provides a foundation for understanding the electronic, optical, and vibrational properties when ErN is doped with nitrogen vacancies.

Modulating membrane permeability and morphology remains a central challenge in the design of responsive colloidal and self-assembled systems. Here, we present a strategy that integrates fluorescently labelled, photoswitchable amphiphiles into lipid vesicles to enable real-time visualization of dynamic membrane behavior and light-triggered cargo release. A novel amphiphilic molecule based on an azobenzene core was synthesized and functionalized with the fluorophore Nile red. This compound was incorporated into giant and large unilamellar vesicles (GUVs and LUVs) composed primarily of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) lipids. The response of the vesicles to alternating UV and visible light was characterized using confocal microscopy, fluorescence spectroscopy, and molecular dynamics simulations. Upon irradiation, vesicles exhibited reversible morphological transformations including budding, swelling, and prolate deformation. Fluorescence imaging confirmed efficient incorporation of the amphiphiles into lipid membranes, and the solvatochromic behavior of Nile red enabled distinction between lipid domains. Simulations revealed that Z-isomerization induces asymmetric expansion of the outer membrane leaflet, increasing surface tension and bending modulus, key drivers of the observed shape changes. Furthermore, cargo release assays with LUVs demonstrated controlled, reversible light-induced permeability. The temporal mismatch between morphological response and ROS (reactive oxygen species) generation, along with the reversibility of the effects, supports a non-oxidative, photomechanical mechanism. Based on these findings, fluorescent photoswitchable amphiphiles can be considered as powerful tools for both functional membrane engineering and the study of the relationship between molecular-level interactions, polarity, and macroscale membrane behavior.

Sulfate-reducing bacteria import organosulfur compounds from the environment for anaerobic respiration. They contribute to human disease and are problematic in industrial settings because they produce hydrogen sulfide. Here, we demonstrate how the sulfate-reducing bacterium Oleidesulfovibrio alaskensis imports isethionate, a common organosulfonate, using a tripartite ATP-independent periplasmic (TRAP) transporter (OaIsePQM). The cryo-EM structure of isethionate-bound OaIseQM to 2.98 Å resolution defines the substrate-binding site, two Na+-binding sites, and a distinct fusion helix. Key residues within the OaIseQM substrate-binding site are identified using substitution and proteoliposome assays. Functional studies demonstrate that OaIseQM requires the substrate-binding protein (OaIseP) and a Na+ gradient to drive transport. Modeling of the OaIsePQM complex supports that elevator-type conformational changes are involved in this unique coupled transport process. This work expands our knowledge of the transport of organosulfur compounds in bacteria and establishes OaIsePQM as a new model system for exploring the mechanism of TRAP transporters.

The efficiency of the electrocatalytic hydrogen evolution reaction (HER) is critically influenced by gas bubble nucleation, growth, and detachment dynamics at the electrode–electrolyte interface. However, correlating individual bubble events with electrochemical responses remains challenging on the macroscale due to overlapping signals from concurrent surface processes. In this study, we use scanning electrochemical cell microscopy (SECCM), integrated with optical imaging, to investigate hydrogen bubble dynamics under confined electrochemical conditions at the microscale, enabling a direct correlation between visual observations and electrochemical responses. We first demonstrate that correlating individual H2 bubble formation with electrochemical responses is difficult at the bulk scale when visualizing the electrode surface during HER on platinum (Pt). SECCM, however, provides a confined environment at the microscale, allowing for systematic variation of H2 mass transport. By adjusting the probe–substrate distance (h), we reveal a strong relationship of gas bubble formation with local confinement by the glass probe and mass transport through the three-phase boundary (electrode–electrolyte–air) at the meniscus. Current–time (i–t) responses directly reflect bubble formation, as the gas bubble blocks the probe orifice, a finding supported by COMSOL simulations. Aerophobic and aerophilic surface modifications of SECCM probes offer further control over interfacial wettability between the gas bubble and Pt surface. Aerophilic probes promote repeated rapid gas film formation and removal inside the glass wall of the probe that is reflected in periodic i–t transients (at ∼1 Hz), while aerophobic probes induce broader droplet contact areas and variable nucleation profiles. Amperometric measurements conducted at 20 spatially distinct locations on a polycrystalline Pt surface generated a comprehensive dataset for statistical analysis, revealing consistent nucleation and detachment times. These findings establish SECCM as a powerful tool for studying liquid–gas phase transitions and interfacial gas management for the development of electrocatalysts.