Fig. 2: Cy5-labeled protein corona is detectable after uptake in murine macrophages.

a RAW264.7 cells were incubated with 150 µg mL⁻¹ of carboxyl-functionalized PS NPs for 2 h. Untreated NPs, NPs with an unlabeled protein corona, and NPs with a Cy5-labeled protein corona were used for the uptake experiment. Flow cytometry was performed to measure BODIPY (PS NPs) fluorescence and Cy5 (labeled corona proteins) fluorescence. Values are shown as the percentage of measured events regarding the fluorescence. b The percentage of BODIPY-positive cells is shown c The percentage of Cy5-positive cells is shown (data is shown as mean ± SD, n = 5). d As a control experiment, RAW264.7 cells were incubated with 9 µg mL⁻¹ Cy5-labeled murine plasma proteins and 150 µg mL⁻¹ of PS NPs with a Cy5-labeled protein corona, respectively. The amount of 9 µg mL⁻¹ corresponds to the amount of proteins on the protein corona. The uptake was evaluated after 2 h and 2 h + 24 h. Flow cytometry was performed to measure the median fluorescence intensity (MFI) of Cy5 (proteins or protein corona; data is shown as mean ± SD, n = 3). The gating strategy for flow cytometry is provided in Supplementary Fig. 2. e The uptake was analyzed by cLSM at three different areas on a single section, and similar results were obtained. Red represents the Cy5-labeled protein corona. The green signal is not included for a better overview of the red signal. Scale bars: 20 µm.