Fig. 1

Physical-chemical characterization of polystyrene NPs. Intensity weighted size distribution of carboxylated (a) and PEGylated (b) polystyrene nanoparticles measured by dynamic light scattering. Representative TEM images of the particles are shown in the top right panels of each DLS plot, scale bars represent 400 nm. c, d Aggregation–agglomeration properties and corona thickening of polystyrene nanoparticles was measured by DLS as a change in hydrodynamic size. Particles were incubated in inorganic (c) or biological solutions (d) for 96 h, and the size distribution was monitored. Color codes of samples are shown in the figure. Data are presented as mean ± standard deviation (n = 3). Particles showed no aggregation in distilled water or in PBS during the 96-h assay period (c). In contrast a time-dependent, heavy particle aggregation was found in serum-free DMEM (d). Incubation of nanoparticles with 10 % FBS also evoked an immediate size increase, but prevented large-scale aggregation (d). SDS-PAGE analysis confirmed the adsorption of serum proteins to both PS-COOH and PS-PEG nanoparticles after 1 h incubation in 10 % serum containing MEM (e) and verified reduced protein adsorption of PEG-coated nanoparticles after 24 h incubation (f)