The development of plant viral nanoparticles (VNP) loaded with different molecular versions of a photodynamic drug is described. Specifically， tobacco mosaic virus (TMV) and tobacco mild green mosaic virus (TMGMV) are developed as drug carriers that encapsulate the monocationic， dicationic， tricationic， and tetracationic versions of a porphyrin-based photosensitizer drug (Zn-Por). While TMV has been extensively explored for various nanotechnology applications， this is the first study investigating TMGMV for medical applications. Light-activated cancer cell killing of Zn-Por-loaded VNPs is studied in vitro using melanoma and cervical cancer models. Native and nucleolin-targeted VNP drug carriers are developed and their efficacy assessed. A fivefold increase in cancer cell killing is observed using nucleolin-targeted TMV loaded with tricationic Zn-Por and displaying the nucleolin-specific F3 peptide.