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Engineered gold nanoparticles (AuNPs) have great potential in many applications due to their tunable optical properties, facile synthesis, and surface functionalization via thiol chemistry. When exposed to a biological environment, NPs are coated with a protein corona that can alter the NPs’ biological identity but can also affect the proteins’ structures and functions. Protein disulfide isomerase (PDI) is an abundant protein responsible for the disulfide formation and isomerization that contribute to overall cell redox homeostasis and signaling. Given that AuNPs are widely employed in nanomedicine and PDI plays a functional role in various diseases, the interactions between oxidized (oPDI) and reduced (rPDI) with 50 nm citrate-coated AuNPs (AuNPs) are examined in this study using various techniques. Upon incubation, PDI adsorbs to the AuNP surface, which leads to a reduction in its enzymatic activity despite limited changes in secondary structures. Partial enzymatic digestion followed by mass spectrometry analysis shows that orientation of PDI on the NP surface is dependent on both its oxidation state and the PDI:AuNP incubation ratios. 

Surface patterning of inorganic nanoparticles through site-selective functionalization with mixed-ligand shells or additional inorganic material is an intriguing approach to developing tailored nanomaterials with potentially novel and/or multifunctional properties. The unique physicochemical properties of such nanoparticles are likely to impact their behavior and functionality in biological environments, catalytic systems, and electronics applications, making it vital to understand how we can achieve and characterize such regioselective surface functionalization. This Feature Article will review methods by which chemists have selectively modified the surface of colloidal nanoparticles to obtain both two-sided Janus particles and nanoparticles with patchy or stripey mixed-ligand shells, as well as to achieve directed growth of mesoporous oxide materials and metals onto existing nanoparticle templates in a spatially and compositionally controlled manner. The advantages and drawbacks of various techniques used to characterize the regiospecificity of anisotropic surface coatings are discussed, as well as areas for improvement, and future directions for this field. 

Supported lipid bilayers are often used as model systems for studying interactions of biological membranes with protein or nanoparticles. A supported lipid bilayer is a phospholipid bilayer built on a solid substrate. The latter is typically made of silica or a metal oxide due to the ease of its formation and range of compatible measurement techniques. Recently, a solvent-assisted method involving supported lipid bilayer formation has allowed the extension of compatible substrate materials to include noble metals such as gold. Here, we examine the influence of substrate composition (SiO2 vs Au) on the interactions between anionic ligand-coated Au nanoparticles or cytochrome c and zwitterionic supported lipid bilayers using quartz crystal microbalance with dissipation monitoring. We find that anionic nanoparticles and cytochrome c have higher adsorption to bilayers formed on Au relative to those on SiO2 substrates. We examine the substrate-dependence of nanoparticle adsorption with DLVO theory and all-atom simulations, and find that the stronger attractive van der Waals and weaker repulsive electrostatic forces between anionic nanoparticles and Au substrates vs anionic nanoparticles and SiO2 substrates could be responsible for the change in adsorption observed. Our results also indicate that the underlying substrate material influences the degree to which nanoscale analytes interact with supported lipid bilayers; therefore, interpretation of the supported lipid bilayer model system should be conducted with understanding of support properties. 

Among high-valence metal oxides, LiCoO 2 and related materials are of environmental importance because of the rapidly increasing use of these materials as cathodes in lithium ion batteries. Understanding the impact of these materials on aqueous environments relies on understanding their redox chemistry because Co release is dependent on oxidation state. Despite the critical role that redox chemistry plays in cellular homeostasis, the influence of specific biologically relevant electron transporters such as nicotinamide adenine dinucleotide (NADH) and glutathione (GSH) on the transformation of engineered nanoparticles has not been widely considered previously. Here we report an investigation of the interaction of LiCoO 2 nanoparticles with NADH and GSH. Measurements of Co release using inductively coupled plasma-mass spectrometry (ICP-MS) show that exposing LiCoO 2 nanoparticles to either NADH or GSH increases solubilization of cobalt, while corresponding spectroscopic measurements show that NADH is concurrently oxidized to NAD + . To demonstrate that these effects are a consequence the high-valence Co(III) inLiCoO 2 nanoparticles, we performed control experiments using Co(II)-containing Co(OH) 2 and LiCoPO 4 , and dissolved Co 2+ /Li + ions. Additional experiments using molecules of similar structure to NADH and GSH, but that are not reducing agents, confirm that these transformations are driven by redox reactions and not by chelation effects. Our data show that interaction of LiCoO 2 with NADH and GSH induces release Co 2+ ions and alters the redox state of these biologically important transporters. Observation of NADH binding to LiCoO 2 using x-ray photoelectron spectroscopy (XPS) suggests a surface catalyzed reaction. The reciprocal reduction of LiCoO 2 to enable release of Co 2+ and corresponding oxidation of NADH and GSH as model redox-active biomolecules has implications for understanding the biological impacts of high-valence metal oxide nanomaterials. 

Lithium cobalt oxide (LiCoO 2 ), an example of nanoscale transition metal oxide and a widely commercialized cathode material in lithium ion batteries, has been shown to induce oxidative stress and generate intracellular reactive oxygen species (ROS) in model organisms. In this study, we aimed to understand the time-dependent roles of abiotic ROS generation and Co ions released in aqueous medium by LiCoO 2 NPs, and examined the induced biological responses in model bacterium, B. subtilis upon exposure. We found that the redox-active LiCoO 2 NPs produced abiotic ROS primarily through H 2 O 2 generation when freshly suspended. Subsequently, the freshly-suspended LiCoO 2 NPs induced additional DNA breakage, and changes in expression of oxidative stress genes in B. subtilis that could not be accounted for by the released Co ions alone. Notably, in 48 hour old LiCoO 2 suspensions, H 2 O 2 generation subsided while higher concentrations of Co ions were released. The biological responses in DNA damage and gene expression to the aged LiCoO 2 NPs recapitulated those induced by the released Co ions. Our results demonstrated oxidative stress mechanisms for bacteria exposed to LiCoO 2 NPs were mediated by the generation of distinct biotic and abiotic ROS species, which depended on the aqueous transformation state of the NPs. This study revealed the interdependent and dynamic nature of NP transformation and their biological consequences where the state of NPs resulted in distinct NP-specific mechanisms of oxidative injury. Our work highlights the need to capture the dynamic transformation of NPs that may activate the multiple routes of oxidative stress responses in cells. 

The increasing use of nanoscale lithium nickel manganese cobalt oxide (Li x Ni y Mn z Co 1−y−z O 2 , NMC) as a cathode material in lithium-ion batteries poses risk to the environment. Learning toxicity mechanisms on molecular levels is critical to promote proactive risk assessment of these complex nanomaterials and inform their sustainable development. We focused on DNA damage as a toxicity mechanism and profiled in depth chemical and biological changes linked to DNA damage in two environmentally relevant bacteria upon nano-NMC exposure. DNA damage occurred in both bacteria, characterized by double-strand breakage and increased levels of many putative chemical modifications on bacterial DNA bases related to direct oxidative stress and lipid peroxidation, measured by cutting-edge DNA adductomic techniques. Chemical probes indicated elevated intracellular reactive oxygen species and transition metal ions, in agreement with DNA adductomics and gene expression analysis. By integrating multi-dimensional datasets from chemical and biological measurements, we present rich mechanistic insights on nano-NMC-induced DNA damage in bacteria, providing targets for biomarkers in the risk assessment of reactive materials that may be extrapolated to other nano–bio interactions. 

As lithium intercalating complex metal oxides become more widely used in energy storage devices, there is an increasing need to understand their environmental impact at the end of their life cycle due to the lack of recycling options. In this study, we examine the biological impact of a panel of nanoscale lithium nickel manganese cobalt oxides (LixNiyMnzCo1−y−zO2, 0 < x, y, z < 1, abbreviated as NMCs), to a model Gram-positive bacterium, Bacillus subtilis in terms of cellular respiration and growth. A highly sensitive single-cell gel electrophoresis method is also applied for the first time to understand the genotoxicity of this nanomaterial to bacterial cells. Results from these assays indicate that the free Ni and Co ions released from the incongruent dissolution of the NMC material in B. subtilis growth media induced both hindered growth and cellular respiration. More remarkably, the DNA damage induced by the combination of the two ions in solution is comparble to that induced by the NMC material, which suggests the free Ni and Co ions are responsible for the toxicity observed. A material redesign by enriching Mn is also presented. The combined approaches of evaluating impact on bacterial growth, respiration, DNA damage at a single-cell level, as well as other phenotypical changes allows us to probe the nanomaterial and bacterial cells from a mechanistic prospective, and provides a useful means to an understanding of bacterial response to new potential environmental stressors.