PEGylated viral nanoparticles for biomedicine: the impact of PEG chain length on VNP cell interactions in vitro and ex vivo.

PEGylation is an effective strategy for reducing biospecific interactions for pharmaceuticals. The plant virus Cowpea mosaic virus (CPMV) has been studied for potential nanobiomedical applications by virtue of its natural interactions with mammalian endothelial cells. To investigate the degree of PEGylation required to retarget CPMV-based formulations to other destinations, two CPMV-PEG formulations, CPMV-PEG1000 (P1) and CPMV-PEG2000 (P2) were tested. Modeling suggested that the PEG chains were displayed as flattened mushrooms on the particle with an estimated surface grafting area of 0.53% for P1 and 0.83% for P2. Only the P2 formulation effectively shielded the particles from interacting with cells or tissues, suggesting that either key interacting regions on the particle surface were blocked or that a sufficient hydration shell had been generated to inhibit cellular interactions. The large CPMV surface area available after PEGylation allows further attachment of imaging and therapeutic molecules to the particle to generate multifunctionality.