Fig. 6: Nanocatalytic performance of GAox–Fe and pro-oxidation property of GA–Fe. | Nature Communications

Fig. 6: Nanocatalytic performance of GAox–Fe and pro-oxidation property of GA–Fe.

From: Intratumoral synthesis of nano-metalchelate for tumor catalytic therapy by ligand field-enhanced coordination

Fig. 6

a High-resolution TEM image of a single GAox–Fe nanoparticle showing the well-crystallized nature. Scale bar, 2 nm. A representative image of three replicates is shown. b Proposed coordination mode of gallate molecules (here should be GAox2−) around each Fe center in GAox–Fe. The connection between the carboxylic anion of gallate and Fe center has shifted from bridge-type coordination to bidentate coordination. c Time-course absorbance of buffer solution (pH = 6.5) containing GAox–Fe and TMB after adding different concentrations of H2O2. d Michaelis-Menten kinetics of GAox–Fe based on (c). For one specific H2O2 concentration, the initial velocity of catalytic reaction was calculated by averaging the mean velocities of initial eight periods in (c) (15 s per period). Data are expressed as mean ± SD (N = 8 independent experiments). e Proposed nanocatalytic reactions triggered by GAox–Fe mimicking the property of HRP. The H2O2 generated from ORRs enabled via the oxidation of fresh GA–Fe in Fig. 4e can be further catalytically converted to •OH by GAox–Fe as a Fenton agent. f ESR spectra evaluating •OH generation in buffer solution (pH = 6.5) containing fresh GA–Fe under the addition of O2 or Ar. g RhB decolorization in buffer solution (pH = 6.5) containing fresh GA–Fe with the presence of O2 (blank group). SOD or catalase has also been added for investigating the generation of O2•− and H2O2 intermediates during the pro-oxidation reactions, respectively. Data are expressed as mean ± SD (N = 3 independent experiments). **P < 0.01, based on the Student’s two-sided t-test. h Proposed pro-oxidation mechanism of GA–Fe. The nano-metalchelate serve as a reactant in the former two one-electron reaction steps to successively reduce oxygen to O2•− and then to H2O2, after which it acts as a nanocatalyst to catalyze the decomposition of H2O2 to •OH. It is noted that additional n mol of H2O2 is required to reduce the [Fe(III)GAox•](x,y,z)2+ intermediate in the third and fourth steps of (e) for sustaining the catalytic process. It can also be considered that only half-amount of generated H2O2 has been catalytically converted to •OH while the other half was used for reducing [Fe(III)GAox•](x,y,z)2+, dependent on the specific chemical environments. However, here we only present the first scenario for a simplified illustration. Source data are provided as a Source Data file.

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