EGFR and cancer: In a study by Kim et al. (2021), Gd(III)-DOTA protein cage nanoparticles were post-functionalized with multiple HER2 or EGFR-specific affibodies using a SpyTag/SpyCatcher system, enabling target-switchable T1 contrast in high-field MRI with selective binding to HER2 or EGFR-overexpressing cells for highly specific and sensitive cancer diagnosis [68].