Uv vis spectrophotometer

For each experimental condition in the dose response assessment and for comparisons of bacterial inactivation by each of the 13 UV-LED wavelengths, 1 mL prepared bacterial suspension was placed in a 35-mm TC dish (Sarstedt, Nümbrecht, Germany) and exposed to UV irradiation without stirring using the developed UV-LED irradiation device (Fig. 1). The bacterial suspension was irradiated at 0, 2, 4, 6, 8, or 10 mW/cm² using 254-, 267-, 270-, and 280-nm UV-LEDs. Experiments for comparisons of device conditions under UV-LED irradiation were as follows: WD was changed to 50, 100, and 200 mm; stage materials were changed to a low-reflection coating or without a low-reflection coating; suspension volume was changed to 1 or 6 mL; and absorbance of each bacterial suspensions were diluted to A₆₀₀ = 2.5 and 0.5 in addition to A₆₀₀ = 0.5/10.
Here, the transmission spectrum of bacterial solutions from 200 to 700 nm was measured using a UV/Vis-spectrophotometer (Beckman Coulter, Brea, CA, USA). To avoid the possible influence of ambient light such as photoreactivation, the entire process of UV exposure and bacterial inoculation was carried out in a dark place.

GPx activity was measured using the Ransel kit (Randox Laboratories, Crumlin, County Antrim, UK) based on a UV method proposed by Paglia and Valentine [27 (link)]. GPx from the sample of heparinized whole blood catalyses the oxidation of GSH (4 mmol/L) by cumene hydroperoxide (0.18 mmol/L). Oxidised glutathione (GSSG) is converted to GSH in the reaction catalysed by glutathione reductase (>0.5 U/L) in the presence of NADPH (reduced form of nicotinamide adenine dinucleotide phosphate) (0.34 mmol/L), leading to a decrease in absorbance, which was further measured at 340 nm. The optical density was measured using the UV/VIS spectrophotometer Beckman. Heparinized whole blood was previously diluted with diluting agent and Drabkins’ reagent to inhibit the interference of other blood peroxidases. GPx activity was expressed as U/L of haemolysate.
In order to determine GSH concentration and CAT activity, we blended equal volumes of blood and cold distillate water, and then centrifugated the mixture for 15 min at 4000× g (Eppendorf refrigerated centrifuge 5417 R, Eppendorf AG, Hamburg, Germany) to obtain a clear haemolysate.

UV-Vis-NIR spectra of the particles were obtained using quartz cuvette with a 1-cm light path using a UV-Vis spectrophotometer (Beckman Coulter, Fullerton, CA, USA). The images of particles during synthesis and modification were captured under transmission electron microscope (JEM 1010 JEOL, Tokyo, Japan) by placing aliquots of aqueous particle suspension on carbon-enhanced copper grids and accelerating the machine at 200 kV. The size distribution of the particles was analyzed using a Zeta instrument (ELS-8000, OTSUKA Electronics Co. Ltd., Japan). The X-ray diffraction (XRD) spectra of the particles were measured using XRD (X’Pert-MPD, Philips, Amsterdam, The Netherlands) with Cu-Kα radiation. To analyze the functional groups of the particles at different stages, aliquots of freeze-dried product were mixed with KBr and pelletized for FTIR analysis (Perkin Elmer Inc., Waltham, Massachusetts, USA) at a resolution of 4 cm⁻¹ over the wavelength range 500 to 4000 cm⁻¹. Thermogravimetric analysis was performed using TGA 7, Pyris 1 (Perkin Elmer, MA, USA).