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1. A Fluidics-Based Biosensor to Detect and Characterize Inhibition Patterns of Organophosphate to Acetylcholinesterase in Food Materials

   https://doi.org/10.3390/mi12040397  

   Pham, Dang Song ; Nguyen, Xuan Anh ; Marsh, Paul ; Chu, Sung Sik ; Lau, Michael P. ; Nguyen, Anh H. ; Cao, Hung ( April 2021 , Micromachines)

   A chip-based electrochemical biosensor is developed herein for the detection of organophosphate (OP) in food materials. The principle of the sensing platform is based on the inhibition of dimethoate (DMT), a typical OP that specifically inhibits acetylcholinesterase (AChE) activity. Carbon nanotube-modified gold electrodes functionalized with polydiallyldimethylammonium chloride (PDDA) and oxidized nanocellulose (NC) were investigated for the sensing of OP, yielding high sensitivity. Compared with noncovalent adsorption and deposition in bovine serum albumin, bioconjugation with lysine side chain activation allowed the enzyme to be stable over three weeks at room temperature. The total amount of AChE was quantified, whose activity inhibition was highly linear with respect to DMT concentration. Increased incubation times and/or DMT concentration decreased current flow. The composite electrode showed a sensitivity 4.8-times higher than that of the bare gold electrode. The biosensor was challenged with organophosphate-spiked food samples and showed a limit of detection (LOD) of DMT at 4.1 nM, with a limit of quantification (LOQ) at 12.6 nM, in the linear range of 10 nM to 1000 nM. Such performance infers significant potential for the use of this system in the detection of organophosphates in real samples.
2. Nanoparticle size and natural organic matter composition determine aggregation behavior of polyvinylpyrrolidone coated platinum nanoparticles

   https://doi.org/10.1039/d0en00659a  

   Sikder, Mithun ; Wang, Jingjing ; Poulin, Brett A. ; Tfaily, Malak M. ; Baalousha, Mohammed ( November 2020 , Environmental Science: Nano)

   Engineered nanoparticle (NP) size and natural organic matter (NOM) composition play important roles in determining NP environmental behaviors. The aim of this work was to investigate how NP size and NOM composition influence the colloidal stability of polyvinylpyrrolidone coated platinum engineered nanoparticles (PVP-PtNPs). We evaluated PVP-PtNP aggregation as a function of the NP size (20, 30, 50, 75, and 95 nm, denoted as PVP-PtNP 20–95 ) in moderately hard water (MHW). Further, we quantified the effect of the hydrophobic organic acid (HPOA) fraction of NOM on the aggregation of PVP-PtNP 20 and PVP-PtNP 95 using 6 NOM samples from various surface waters, representing a range of NOM compositions and properties. NOM samples were characterized for bulk elemental composition ( e.g. , C, H, O, N, and S), specific ultraviolet absorbance at 254 nm (SUVA 254 ), and molecular level composition ( e.g. , compound classes) using ultrahigh resolution mass spectrometry. Single particle-inductively coupled plasma-mass spectrometry (sp-ICP-MS) was employed to monitor the aggregation of PVP-PtNPs at 1 μg PVP-PtNP per L and 1 mg NOM per L concentrations. PVP-PtNP aggregate size increased with decreasing primary PVP-PtNP size, likely due to the lower zeta potential, the higher number concentration, and the highermore »specific surface area of smaller NPs compared to larger NPs at the same mass concentration. No aggregation was observed for PVP-PtNP 95 in MHW in the presence and absence of the different NOM samples. PVP-PtNP 20 formed aggregates in MHW in the presence and absence of the six NOM samples, and aggregate size increased in the presence of NOM likely due to interparticle bridging of NOM-coated PVP-PtNPs by divalent counterions. PVP-PtNP 20 aggregate size increased with the increase in NOM elemental ratio of H to C and the relative abundance of lignin-like/carboxyl rich-alicyclic molecules (CRAM)-like compounds. However, the aggregate size of PVP-PtNP 20 decreased with the increase in NOM molecular weight, NOM SUVA 254 , elemental ratio of O to C, and the relative abundance of condensed hydrocarbons and tannin-like compounds. Overall, the results of this study suggest that the composition and sources of NOM are key factors that contribute to the stability of PVP-PtNPs in the aquatic environment.« less
3. Chemical modification in and on single phase [NiO] _0.5 [Al ₂ O ₃ ] _0.5 nanopowders produces “chocolate chip‐like” Ni _x @[NiO] _0.5‐x [Al ₂ O ₃ ] _0.5 nanocomposite nanopowders

   https://doi.org/10.1111/jace.16632  

   Wang, Fei ; Sun, Kai ; Yi, Eongyu ; Laine, Richard M. ( June 2019 , Journal of the American Ceramic Society)

   Phase‐pure [NiO]_0.5[Al₂O₃]_0.5spinel nanoparticles (NPs) with limited aggregation were obtained via liquid‐feed flame spray pyrolysis (LF‐FSP) by combusting metalloorganic precursor solutions. Thereafter “chocolate chip‐like” Ni_x[NiO_0.5‐x][Al₂O₃]_0.5nanoparticles consisting of primary [NiO_0.5‐x][Al₂O₃]_0.5particles with average particle sizes of 40‐60 nm decorated with Ni metal particles (<10 nm in diameter) dispersed on the surface were synthesized by heat treating the spinel NPs at 800°C/7 h in flowing 5% H₂:N₂100 mL/min in a fluidized bed reactor. The synthesized materials were characterized using TEM, XRD, FTIR, and TGA/DTA. The Ni depleted areas consist primarily of γ‐Al₂O₃. The Ni content (800°C) was determined by TGA to be ≈11.3 wt.% based on TGA oxidation behavior. The successful synthesis of such nanocomposites with limited aggregation on a high temperature support provides a facile route to synthesize well‐defined NP catalysts. This work serves as a baseline study for an accompanying paper, wherein thin, flexible, dense films made from these same NPs are used as regenerable catalysts for carbon nanotube syntheses.
4. A High-Pressure System for Studying Oxygen Reduction During Pt Nanoparticle Collisions

   https://doi.org/10.1149/1945-7111/abcde2  

   Zhang, Yulun ; Robinson, Donald A. ; McKelvey, Kim ; Ren, Hang ; White, Henry S. ; Edwards, Martin A. ( December 2020 , Journal of The Electrochemical Society)

   Here we report measurements of the oxygen reduction reaction (ORR) at single Pt nanoparticles (NPs) through their collision with a Au microdisk electrode of lower electrocatalytic activity. Performing measurements at an elevated pressure (10-atm, pure O₂) raises the O₂concentration ∼50-fold over air-saturated measurements, allowing the ORR activity of smaller Pt NPs to be resolved and quantified, compared to measurements taken at atmospheric pressure. Single-NP ORR current vs potential measurements for 2.6, 16, and 24 nm radius citrate-capped Pt NPs, show the catalytic activity of the smallest Pt NPs to be roughly one order of magnitude greater than the activity of the larger NPs. The particle-by-particle nature of our measurement quantifies the distribution of electrocatalytic activities of individual particles, which we determine to be larger than can be explained by the distribution of particle sizes. Additionally, we report that some of the observed ORR current transients contain multiple sharp peaks per single-NP measurement, indicating multiple collisions of a single Pt NP at the electrode surface.
5. Particle size determines the accumulation of platinum nanoparticles in the estuarine amphipod, Leptocheirus plumulosus

   https://doi.org/10.1039/d1en00713k  

   Sikder, Mithun ; Eudy, Emily ; Cai, Bo ; Chandler, G. Thomas ; Baalousha, Mohammed ( February 2022 , Environmental Science: Nano)

   Nanoparticles (NPs) typically display a wide distribution of different sizes in aquatic environments, yet little information is available on the impact of particle size dispersity on organismal uptake and elimination. This study investigated uptake and elimination of polyvinylpyrrolidone-coated platinum nanoparticles (PVP-PtNPs) of different sizes ( e.g. , 20.0 ± 4.8 nm, 40.5 ± 4.1 nm, and 70.8 ± 4.2 nm) by the estuarine amphipod Leptocheirus plumulosus . Accumulation and elimination were determined by measuring total Pt body burden in amphipods exposed to PtNPs using inductively coupled plasma-mass spectroscopy, as well as the mass and number PtNP body burden using single particle-ICP-MS (sp-ICP-MS). L. plumulosus accumulated Pt from PtNP suspensions of different sizes from water exposure, mostly ( e.g. , >90%) as PtNPs rather than as dissolved Pt. Mass- and number-based uptake increased with decreases in PtNP size whereas mass- and number-based elimination increased with increasing PtNP size. The residual whole-animal body burden of PtNPs after 48 h elimination increased with decreases in PtNP size, with residual body burdens approximately two-fold higher for amphipods exposed to 20 nm PtNPs than amphipods exposed to 70 nm PtNPs. PtNP influx rate ( k uw ) increased with decreasing NP size, with k uwmore »s of 1.07 ± 0.31, 0.82 ± 0.22, and 0.67 ± 0.10 μg g −1 d −1 for 20 nm, 40 nm, and 70 nm PtNPs, respectively. PtNP efflux rate ( k e ) increased with increasing PtNP size, with k e s of 0.31 ± 0.08, 0.66 ± 0.04, and 0.83 ± 0.07 d −1 for 20 nm, 40 nm, and 70 nm PtNP, respectively. When exposed to mixtures of 40 and 70 nm PtNPs with equal masses, surface areas, or number concentrations of 40 nm and 70 nm PtNPs, L. plumulosus accumulated higher numbers of the 40 nm PtNPs than 70 nm PtNPs from all mixtures. The increased exposure concentration of 70 nm PtNPs in the mixture did not affect the uptake of 40 nm PtNPs, suggesting that in a polydispersed NP suspension the uptake of a given size fraction is independent of other size fractions in the mixture.« less