Figure 6. Receptor clustering and internalization by protein G-functionalized GFP polygons.

(a) Confocal microscopy analysis of enhanced internalization of antibody–receptor clusters by protein G polygons. Cy5-labelled Erbitux (targeting EGFR) was treated to A549 cells with or without subsequent protein G hexamer treatment at 4 °C. After temperature change to 37 °C, receptor internalization was monitored by imaging Erbitux (Cy5) as well as protein G hexamer (GFP) at different time points. Cy5-Erbitux, red; Protein G-hexamer, green. (b) Flow cytometry analysis of antibody-mediated receptor internalization. A549 cells were treated with Cy5-Erbitux and subsequently protein G polygons with various valencies. Internalized levels of Cy5-Erbitux were quantified by flow cytometry. The error bars correspond to the s.e.m. of three independent measurements.