Fig. 4From: Horseradish Peroxidase-Encapsulated Hollow Silica Nanospheres for Intracellular Sensing of Reactive Oxygen Speciesa WST-1 assay of RAW 264.7 macrophages after treatments of exogenous H2O2 or stimulation with phorbol 12-myristate 13-acetate (PMA) for 1 h. b Detection of the concentration of H2O2 endogenously produced by RAW264.7 macrophages under various concentrations of the PMA stimulant in the presence of horseradish peroxidase-encapsulated hollow silica nanospheres (HRP@HSNs) and dihydrorhodamine 123 (DHR123). Inset: a calibration curve obtained from the external standards of H2O2 mixed with HRP@HSNs and DHR123Back to article page