Exogenous Fe2+ alleviated the toxicity of CuO nanoparticles on Pseudomonas tolaasii Y-11 under different nitrogen sources

Extensive use of CuO nanoparticles (CuO-NPs ) inevitably leads to their accumulation in wastewater and toxicity to microorganisms that effectively treat nitrogen pollution. Due to the effects of different mediums, the sources of CuO-NPs-induced toxicity to microorganisms and methods to mitigating the toxicity are still unclear. In this study, CuO-NPs were found to impact the nitrate reduction of Pseudomonas tolaasii Y-11 mainly through the action of NPs themselves while inhibiting the ammonium transformation of strain Y-11 through releasing Cu2+. As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO3− and NH4+ decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe2+ significantly promoted the aggregation of CuO-NPs, reduced the possibility of contact with bacteria, and slowed down the damage of CuO-NPs to strain Y-11. When 0.01 mol/L Fe2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO3- were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH4+ were 55.95%, 96.71%, 38.11%, 20.71% and 7.43%, respectively. This study provides a method for mitigating the toxicity of CuO-NPs on functional microorganisms

High Relaxivity Gadolinium-Polydopamine Nanoparticles

AbstractThis study reports the preparation of a series of gadolinium‐polydopamine nanoparticles (GdPD‐NPs) with tunable metal loadings. GdPD‐NPs are analyzed by nuclear magnetic relaxation dispersion and with a 7‐tesla (T) magnetic resonance imaging (MRI) scanner. A relaxivity of 75 and 10.3 mM−1 s−1 at 1.4 and 7 T is observed, respectively. Furthermore, superconducting quantum interference device magnetometry is used to study intraparticle magnetic interactions and determine the GdPD‐NPs consist of isolated metal ions even at maximum metal loadings. From these data, it is concluded that the observed high relaxivities arise from a high hydration state of the Gd(III) at the particle surface, fast rate of water exchange, and negligible antiferromagnetic coupling between Gd(III) centers throughout the particles. This study highlights design parameters and a robust synthetic approach that aid in the development of this scaffold for T1‐weighted, high relaxivity MRI contrast agents

Structure and Function of Iron-Loaded Synthetic Melanin

We describe a synthetic method for increasing and controlling the iron loading of synthetic melanin nanoparticles and use the resulting materials to perform a systematic quantitative investigation on their structure 12property relationship. A comprehensive analysis by magnetometry, electron paramagnetic resonance, and nuclear magnetic relaxation dispersion reveals the complexities of their magnetic behavior and how these intraparticle magnetic interactions manifest in useful material properties such as their performance as MRI contrast agents. This analysis allows predictions of the optimal iron loading through a quantitative modeling of antiferromagnetic coupling that arises from proximal iron ions. This study provides a detailed understanding of this complex class of synthetic biomaterials and gives insight into interactions and structures prevalent in naturally occurring melanins

A self-assembling fluorescent dipeptide conjugate for cell labelling

Derivatives of fluorophore FITC (fluorescein isothiocyanate) are widely used in bioassays to label proteins and cells. An N-terminal leucine dipeptide is attached to FITC, and we show that this simple conjugate molecule is cytocompatible and is uptaken by cells (human dermal and corneal fibroblasts) in contrast to FITC itself. Co-localisation shows that FITC-LL segregates in peri-nuclear and intracellular vesicle regions. Above a critical aggregation concentration, the conjugate is shown to self-assemble into beta-sheet nanostructures comprising molecular bilayers

Metallic contact between MoS2 and Ni via Au nanoglue

A critical factor for electronics based on inorganic layered crystals stems from the electrical contact mode between the semiconducting crystals and the metal counterparts in the electric circuit. Here, a materials tailoring strategy via nanocomposite decoration is carried out to reach metallic contact between MoS2 matrix and transition metal nanoparticles. Nickel nanoparticles (NiNPs) are successfully joined to the sides of a layered MoS2 crystal through gold nanobuffers, forming semiconducting and magnetic NiNPs@MoS2 complexes. The intrinsic semiconducting property of MoS2 remains unchanged, and it can be lowered to only few layers. Chemical bonding of the Ni to the MoS2 host is verified by synchrotron radiation based photoemission electron microscopy, and further proved by first- principles calculations. Following the system's band alignment, new electron migration channels between metal and the semiconducting side contribute to the metallic contact mechanism, while semiconductor–metal heterojunctions enhance the photocatalytic ability

Large positive in-plane magnetoresistance induced by localized states at nanodomain boundaries in graphene

Graphene supports long spin lifetimes and long diffusion lengths at room temperature, making it highly promising for spintronics. However, making graphene magnetic remains a principal challenge despite the many proposed solutions. Among these, graphene with zig-zag edges and ripples are the most promising candidates, as zig-zag edges are predicted to host spin-polarized electronic states, and spin-orbit coupling can be induced by ripples. Here we investigate the magnetoresistance of graphene grown on technologically relevant SiC/Si(001) wafers, where inherent nanodomain boundaries sandwich zig-zag structures between adjacent ripples of large curvature. Localized states at the nanodomain boundaries result in an unprecedented positive in-plane magnetoresistance with a strong temperature dependence. Our work may offer a tantalizing way to add the spin degree of freedom to graphene

Multifunctional Polymeric Materials Programming Interfaces and Designed Artificial Melanosomes

The interfaces with micro/nanostructures in nature play important roles to bring in specific functions, which inspired and drove the development of novel nanostructures, including inorganic nanoparticles and organic nanoparticles. Among them, polymeric nanoparticles have been widely explored to programming interfaces because of the precise controlling in synthesis of polymers. Ring opening metathesis polymerization (ROMP) is a unique polymerization technique, which can incorporate versatile functional groups, tunable composition (hydrophobicity, molecular weight), and stimuli-responsiveness to endow various functionalities for the polymers, which have been explored for different application areas. In our research, we focused on designing and synthesizing multifunctional ROMP-based polymeric materials programming interfaces for different applications. For Chapter 2, we describe amphiphilic tri-block copolymers containing FeIII-catecholate complexes formulated as spherical- or cylindrical-shaped micellar nanoparticles (SMN and CMN respectively) as new T1-weighted agents with high relaxivity, low cytotoxicity, and long-term stability in biological fluids. Relaxivities of both SMN and CMN exceed those of established gadolinium chelates across a wide range of magnetic field strengths. Interestingly, shape-dependent behavior was observed in terms of the particles’ interactions with HeLa cells, with CMN exhibiting enhanced uptake and contrast via magnetic resonance imaging (MRI) compared with SMN. These results suggest that control over soft nanoparticle shape will provide an avenue for optimization of particle based contrast agents as biodiagnostics. We propose those polycatechol nanoparticles as suitable for pre-clinical investigations into their viability as gadolinium-free, safe and effective imaging agents for MRI contrast enhancement. For Chapter 3, we describe a method for the stabilization of low-boiling point (low-bp) perfluorocarbons (PFCs) at physiological temperatures by an amphiphilic triblock copolymer which can emulsify PFCs and be crosslinked. After UV-induced thiol-ene crosslinking, the core of the PFC emulsion remains in liquid form even at temperatures exceeding their boiling points. Critically, the formulation permits vaporization at rarefactional pressures relevant for clinical ultrasound. For Chapter 4, liquid crystals confined within micrometer-scale domains have been explored as the basis of a wide range of field- and stimuli-responsive materials for use in technologies spanning from biological sensors to electro-optical devices. We aim to build up a versatile stimuli-responsive polymeric surfactant to modulate the orientation of liquid crystal microdroplets. By incorporated different types of cleavable linkers into this system, we are able to endow versatile stimuli-responsiveness (UV, Redox, pH, ROS) in order to adapt to different certain circumstances. We proved that those cleavable linker-contained homopolymers were able to emulsify with liquid crystal droplets and generate radial configuration. Then, by introducing specific stimuli, the linker will be cleaved and the homopolymer will be disassembled from the surface, then the configurations of liquid crystal droplets will change into bipolar. This work will provide fundamental information for designing a stimuli-responsive ROMP-based polymeric system, and it is promising to utilize this system as biosensor to detect some specific behaviors. For Chapter 5, we prepared melanin-like nanoparticles (MelNPs) via spontaneous oxidation of dopamine, as biocompatible, synthetic analogues of naturally occurring melanosomes, and investigated their uptake, transport, distribution, and UV-protective capabilities in human keratinocytes. Critically, we demonstrate that MelNPs are endocytosed, undergo perinuclear aggregation, and form a supranuclear cap, or so-called microparasol in human epidermal keratinocytes (HEKa), mimicking the behavior of natural melananosomes in terms of cellular distribution and the fact that they serve to protect the cells from UV damage