Libra s60

The AR activity was determined at 37 °C as previously described³¹, following the decrease in absorbance at 340 nm due to NADPH oxidation (ε₃₄₀ = 6.22 mM⁻¹·cm⁻¹) through a Biochrom Libra S60 spectrophotometer (Biochrom, Cambridge, United Kingdom). The standard assay mixture contained a 0.25 M sodium phosphate buffer pH 6.8, 0.18 mM NADPH, 0.4 M ammonium sulphate, 0.5 mM EDTA and 4.7 mM GAL. One unit of enzyme activity is the amount that catalyses the conversion of 1 µmol of substrate/min in the above assay conditions. These assay conditions were also adopted to assess the effectiveness of inhibitors when L-idose, trans-4-hydroxy-2,3-nonenal (HNE), or 3-glutathionyl-4-hydroxynonenal (GSHNE) was used as a substrate instead of GAL.

Scanning
electron microscopy (SEM) images were acquired with a FESEM Zeiss
Ultra Plus operated at 3 kV to get surface information or at 20 kV
to penetrate deeper into the sample and obtain a greater contrast
of the plasmonic nanoparticle into the NR. Transmission electron microscopy
(TEM) images were acquired with a JEOL JEM-2010 microscope operated
at 200 kV by deposition of the sample on top of a copper grid coated
with a layer of carbon. A Biochrom Libra S60 UV–visible (spectrophotometer
was used to record UV–vis absorption spectrum of the NRs. Nanoparticle
size and concentration were determined by nanoparticle tracking analysis
(NTA), using a NanoSight NS300 (Malvern Instrument Ktd) equipped with
a 405 nm laser. The hydrodynamic diameter (d_h) and polydispersity indexes (PDI) of the NRs were determined
by dynamic light scattering (DLS) using a Malvern Zetasizer Nano ZSP
equipped with a 10 mW He–Ne laser operating at a wavelength
of 633 nm and fixed scattering angle of 173°. Zeta potential
(ζ) was measured with laser Doppler anemometry (LDA) using the
same Malvern’s instrument.

All experiments were proceeded in a duplicate batch system using a 50 mL conical tube (PE, SPL Korea, Hwaseong, Korea). For adsorption isotherm experiments, CPX adsorption was performed at 250 rpm for 24 h at room temperature using solutions of various concentrations (1–50 ppm). The amount of GO/Ca-Alg₂–PAM beads used at this time was 0.05 g, and the volume of the contact solution was 55 mL. The solution was separated from adsorbents by centrifugation at 3500 rpm for 10 min. The solution was filtered by 0.20 μm filters (Whatman, nitrocellulose membrane filters). The residual concentration of CPX was measured by a UV–visible spectrophotometer (Libra S60, Biochrom, Hwaseong, Korea) at 270 nm.
The equilibrium q_e value equation is shown below: $$q_e=\frac{\left(C_o-C_e\right)V}{W}$$
where q_e is the adsorption capacity (mg/g), and C_o and C_e are the before and after adsorption concentrations (ppm) of CPX, respectively. V represents the contact solution volume (mL) and W represents the weight of the adsorbent (g).
Temperature effect adsorption experiments with 0.5, 1, and 2 ppm CPX were performed at 10 °C, 25 °C, and 40 °C. The adsorption procedure was identical to the isothermal adsorption experiment.