Publications by authors named "Andrew J Christofferson"

Nanomaterials are revolutionizing the development of novel therapies, with applications ranging from drug delivery and diagnostics to controlling specific biological processes. However, the specific interactions that govern nanomaterial behavior in biological systems remain difficult to elucidate due to the complex dynamic nature of the lipid bilayer environment. Here, a combination of atomic force microscopy and molecular dynamics simulations is used to discover the precise mechanisms by which various ligand-capped 5 nm gold nanoparticles (AuNPs) interact with supported lipid bilayers of pure fluid phospholipids (1,2-di(9Z-octadecenoyl)-sn-glycero-3-phosphocholine (DOPC)).

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The presence of solvated metallic elements with high mobility enables many applications of liquid metals (LMs) such as in catalysis, phase change materials, welding, soldering, and additive manufacturing. While the processes of crystallisation and dissolution in LM resemble those of traditional solvents, they have not been studied in great detail. Furthermore, crucial observations of solute mass transport speeds (flux) in LM have not been evaluated yet, despite being discovered within catalytic environments.

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Nanomaterials are revolutionizing biomedical research by enabling the development of novel therapies, with applications ranging from drug delivery and diagnostics to the modulation of specific biological processes. Current research focuses on tasks such as enhancing cellular uptake of materials while preserving their functionality. However, the mechanisms governing interactions between nanomaterials and biological systems-particularly cellular membranes-remain challenging to elucidate due to the complex, dynamic nature of the lipid bilayer environment.

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Hypothesis: Nanomaterials have gained significant attention due to their unique properties and potential applications in various biomedical fields, including immediate or targeted drug delivery for wound treatment, cancers, and microbial infections, as well as advancements in diagnostic techniques and tissue engineering. They can also penetrate biological barriers, such as lipid bilayers, offering potential for enhanced drug delivery systems. However, understanding nanomaterial-biomembrane interactions is critical to optimize their design for efficient and safe therapeutic applications.

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Gallium and gallium alloys have gained significant interest due to gallium's low melting point. This property allows for gallium-based catalysts to take advantage of the unique reaction environments only available in the liquid state. While understanding of the catalytic properties of liquid metals is emerging, a comprehensive investigation into the fundamental structures of these materials has yet to be undertaken.

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Developing efficient and durable electrocatalysts for ethanol electro-oxidation is crucial for enabling the application of direct ethanol fuel cell technology. Herein, it is demonstrated that Pt-Ga liquid metal-based nanodroplets can serve as an efficient electrocatalyst to drive ethanol oxidation. The mass activity of Pt is significantly improved by alloying with liquid gallium.

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Carbon-carbon (C─C) bond formation is a key step in diverse chemical processes and requires high-performance catalysts to enable energy-efficient technologies. Here, we present liquid Pd catalysts, formed by dissolving Pd in liquid Ga, for high-turnover C─C coupling reactions. The liquid Pd catalyst achieved a turnover frequency of 2.

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Regulating favorable assemblies of metallic atoms in the liquid state provides promise for catalyzing various chemical reactions. Expanding the selection of metallic solvents, especially those with unique properties and low cost, enables access to distinctive fluidic atomic structures on the surface of liquid alloys and offers economic feasibility. Here, Sn solvent, as a low-cost commodity, supports unique atomic assemblies at the interface of molten SnInCu, which are highly selective for H synthesis from hydrocarbons.

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Antimicrobial resistance (AMR) is a significant concern to society as it threatens the effectiveness of antibiotics and leads to increased morbidity and mortality rates. Innovative approaches are urgently required to address this challenge. Among promising solutions, two dimensional (2-D) nanomaterials with layered crystal structures have emerged as potent antimicrobial agents owing to their unique physicochemical properties.

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Lead (Pb) halide perovskite solar cells (PSCs) exhibit impressive power conversion efficiencies close to those of their silicon counterparts. However, they suffer from moisture instability and Pb safety concerns. Previous studies have endeavoured to address these issues independently, yielding minimal advancements.

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Low-melting liquid metals are emerging as a new group of highly functional solvents due to their capability to dissolve and alloy various metals in their elemental state to form solutions as well as colloidal systems. Furthermore, these liquid metals can facilitate and catalyze multiple unique chemical reactions. Despite the intriguing science behind liquid metals and alloys, very little is known about their fundamental structures in the nanometric regime.

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Crystallization of alloys from a molten state is a fundamental process underpinning metallurgy. Here the direct imaging of an intermetallic precipitation reaction at equilibrium in a liquid-metal environment is demonstrated. It is shown that the outer layers of a solidified intermetallic are surprisingly unstable to the depths of several nanometers, fluctuating between a crystalline and a liquid state.

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A series of nine luminescent iridium(III) complexes with pH-responsive imidazole and benzimidazole ligands have been prepared and characterized. The first series of complexes were of the form [Ir(ppy)(N^N)] or [Ir(ppy)(C^N)] (where ppy is 2-phenylpyridine and N^N is 2-(2-pyridyl)imidazole or 2-(2-pyridyl)benzimidazole and C^N represents a pyridyl-triazolylidene-based N-heterocyclic carbene ligand). For these complexes, the benzimidazole group was either unsubstituted or substituted with electron-withdrawing (Cl) or electron-donating (Me) groups.

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The emergence of ferroelectricity in two-dimensional (2D) metal oxides is a topic of significant technological interest; however, many 2D metal oxides lack intrinsic ferroelectric properties. Therefore, introducing asymmetry provides access to a broader range of 2D materials within the ferroelectric family. Here, the generation of asymmetry in 2D SnO by doping the material with HfZrO (HZO) is demonstrated.

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The use of liquid gallium as a solvent for catalytic reactions has enabled access to well-dispersed metal atoms configurations, leading to unique catalytic phenomena, including activation of neighbouring liquid atoms and mobility-induced activity enhancement. To gain mechanistic insights into liquid metal catalysts, here we introduce a GaSnNi liquid alloy for selective propylene synthesis from decane. Owing to their mobility, dispersed atoms in a Ga matrix generate configurations where interfacial Sn and Ni atoms allow for critical alignments of reactants and intermediates.

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Hypothesis: Nanomaterials have been extensively investigated for a wide range of biomedical applications, including as antimicrobial agents, drug delivery vehicles, and diagnostic devices. The commonality between these biomedical applications is the necessity for the nanoparticle to interact with or pass through the cellular wall and membrane. Cell-nanomaterial interactions/uptake can occur in various ways, including adhering to the cell wall, forming aggregates on the surface, becoming absorbed within the cell wall itself, or transversing into the cell cytoplasm.

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Few-layer black phosphorus (FLBP), a technologically important 2D material, faces a major hurdle to consumer applications: spontaneous degradation under ambient conditions. Blocking the direct exposure of FLBP to the environment has remained the key strategy to enhance its stability, but this can also limit its utility. In this paper, a more ambitious approach to handling FLBP is reported where not only is FLBP oxidation blocked, but it is also repaired postoxidation.

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NfsB has been studied extensively for its potential for cancer gene therapy by reducing the prodrug CB1954 to a cytotoxic derivative. We have previously made several mutants with enhanced activity for the prodrug and characterised their activity in vitro and in vivo. Here, we determine the X-ray structure of our most active triple and double mutants to date, T41Q/N71S/F124T and T41L/N71S.

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Although sonodynamic therapy (SDT) has shown promise for cancer treatment, the lack of efficient sonosensitizers (SSs) has limited the clinical application of SDT. Here, a new strategy is reported for designing efficient nano-sonosensitizers based on 2D nanoscale metal-organic layers (MOLs). Composed of Hf-oxo secondary building units (SBUs) and iridium-based linkers, the MOL is anchored with 5,10,15,20-tetra(p-benzoato)porphyrin (TBP) sensitizers on the SBUs to afford TBP@MOL.

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Nanomaterials have the potential to transform biological and biomedical research, with applications ranging from drug delivery and diagnostics to targeted interference of specific biological processes. Most existing research is aimed at developing nanomaterials for specific tasks such as enhanced biocellular internalization. However, fundamental aspects of the interactions between nanomaterials and biological systems, in particular, membranes, remain poorly understood.

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Mixtures of short-chain alcohols and water produce anomalous thermodynamic and structural quantities, including molecular segregation into water-rich and alcohol-rich components. Herein, we used molecular dynamics simulations with polarizable models to investigate interactions that could drive the self-association of water molecules in mixtures with methanol (MeOH). As water was diluted with MeOH, significant changes in the distribution of molecules and solvation properties occurred, where water exhibited a clear preference for self-association.

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Article Synopsis
  • Cryopreservation has advanced fields like assisted reproductive technology and stem cell therapies, but traditional cryoprotectants (dimethylsulfoxide and glycerol) are toxic and ineffective for many cell types.
  • Research indicates that deep eutectic solvents can serve as effective cryoprotectants, with a specific combination made from proline and glycerol showing promising results for mammalian cells.
  • The study not only showcases the potential of these solvents for preserving various cell types but also contributes to the future development of custom cryoprotective agents, paving the way for improved organ and tissue storage.
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Article Synopsis
  • Understanding how metal atoms interact in catalytic systems is crucial for maximizing their effectiveness.
  • Research shows that platinum dissolved in liquid gallium enhances catalytic reactions at lower temperatures without separating from the gallium matrix.
  • This liquid catalyst demonstrates significantly higher efficiency in electrochemical methanol oxidation compared to traditional solid platinum catalysts, paving the way for new catalytic applications.
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Nitroreductases activate nitroaromatic antibiotics and cancer prodrugs to cytotoxic hydroxylamines and reduce quinones to quinols. Using steady-state and stopped-flow kinetics, we show that the Escherichia coli nitroreductase NfsA is 20-50 fold more active with NADPH than with NADH and that product release may be rate-limiting. The crystal structure of NfsA with NADP shows that a mobile loop forms a phosphate-binding pocket.

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