Quantifying H2S and NO Release from i-POF Discs

For the aqueous solution H₂S/NO kinetic release studies, the i-POF was mixed with Teflon particles in a wt.% ratio of 75:25 (sample: Teflon) and converted into disc pellets with 5 mm diameter in order to avoid sample dispersion in the liquid. The prior outgassing was conducted using the same conditions as the adsorption studies. The loading of the material with H₂S/NO used the procedure already described in [34 (link),35 (link)].
The DTNB and oxyhemoglobin assays were used for the H₂S and NO release studies, respectively. These two methodologies are appropriate for these studies since they allow detecting the presence of H₂S and NO at physiological pH (pH = 7.2). The preparation of the solutions and the detailed experimental procedures are described elsewhere [34 (link),35 (link)]. Briefly, the DTNB methodology is based on the absorbance (408 nm) of the anion 5-thio-2-nitrobenzoate formed in the reaction between DTNB and H₂S [36 ]. The calibration curve and corresponding spectra of the DTNB method are presented in the (Supplementary MaterialsFigure S1). The oxyhemoglobin assay is based on the oxidation of NO to nitrate by oxyhemoglobin (HbO₂). The reaction begins with methemoglobin (metHb), which absorbs at 406 nm. A shift to 415 nm (absorbance of HbO₂) is observed, allowing the NO to be quantified [37 ].
The experiments were conducted by adding the H₂S/NO loaded pellets to the DTNB or hemoglobin solutions, respectively. The first spectrum was acquired after 2 min of the pellet addition, followed by 15 to 30 min intervals until no changes were observed in the spectra, or all the hemoglobin was consumed. The absorbance spectra were recorded using a UV/Vis spectrophotometer (Genesys 10S UV/Vis spectrophotometer from Thermo Scientific Blank, Waltham, MA, USA) at room temperature. The absorbances were measured in the 250–500 nm range for the DTNB method and 350–700 nm for the oxyhemoglobin assay. The experimental conditions used in this study are shown in Table 1.