Modulating the rigidity of nanoparticles for tumor penetration.

How the rigidity of nanoparticles affects their penetration into tumors is unclear. Core-shell nanoparticles were prepared with amphipathic poly(ethylene glycol)-b-(poly ε-caprolactone-g-poly butyl acrylate) (PEG-(PCL-g-PBA)) so that the mechanical stiffness of their cores could be varied in order to test the relationship between their rigidity and penetration through tumors. The rigidity of the nanoparticles was adjusted by the changeable crystallinity of the core, which was altered by varying the ratio of ε-caprolactone and butyl acrylate.