EGFR and neoplasm: To visualize whether pre-targeting can facilitate the uptake and retention of PEGylated compounds in tumours, mice bearing established high EGFR expression levels (MDA-MB-468 and A431) or low EGFR expression levels (HepG2) tumours were intravenously injected with 6 mg kg−1 PEG engager and then subsequently intravenously injected with 4armPEG10k-NIR-797 probe 5 h later.