Fig. 3

Distribution of polystyrene NPs in the brain and the placenta 5 min after systemic exposure. Spectral images of tissue sections from the mouse brain (a, b) and placenta (c, d) 5 min after injection of PS-COOH (a, c) or PS-PEG (b, d) nanoparticles into the tail vein. a′–d′: spectrum profiles of ROIs in the corresponding images. The spectrum of each ROI is marked with the same color as it is delineated in the microscopic image. Green curves represent particle fluorescence (positive controls); red curve represents tissue autofluorescence (negative control). Scale bars 50 µm