Phi 5600 xps

The disintegration of FKPN in response to GSH was examined by analyzing the chemical states of iron using a Perkin Elmer PHI 5600 XPS. TEM imaging was used to record the morphology change of FKPN. Furthermore, the GSH depletion was measured using Ellman’s reagent^{50 (link)}. Briefly, DMSO solution containing DTNB (5 μL, 100 mM) was mixed with GSH solution (995 μL) with different concentrations (0, 0.625, 1.25, 2.5, 5, 10 mM). The absorbance of solutions in 24-well plates were determined by a Bio-Rad model-680 microplate reader (USA) at λ = 405 nm after incubation for 2 min, establishing A_GSH standard curve. Meanwhile, the standard curve of nanoparticles (NPs) was determined through measuring the absorbance of NP solution (420 nm). Then different concentrations of GSH solutions (C₀, 995 μL) were incubated with a certain concentration of NPs, followed by adding 5 μL of DMSO containing DTNB (100 mM). The absorption of the solutions in 96 well plates was detected by microplate reader at λ = 405 nm after standing for 10 min. The background absorption was subtracted from the sample absorption. The depletion of GSH (C_X) were calculated by the formula: C_X = (A_X − A_NPs)/(A_GSH − A_NPs) × C₀.

XPS spectra of the pristine PDA and LAPDA films were obtained using Phi 5600 XPS (Perkin Elmer, USA) to analyze atomic compositions. A monochromatic X-ray source (Al Kα) was used for the data collection. To avoid the effect of surface charging, the neutralizer was applied simultaneously to the surfaces with a constant current (~1 µA). The at.%s were calculated by deconvolution of the XPS spectra with MATLAB-based software (MultiPak) provided by Physical Electronics, Inc.