Figure. 4. The size effect of nanoparticles: A. Large-size nanoparticles will cause more significant cell membrane deformation, reproduced from Reference44 with permission from Copyright © 2016, Springer Nature. B. As the size is smaller than the optimal size, large-size nanoparticles are more likely to be wrapped by cell membranes than small-size particles, reproduced from Reference50 with permission from Copyright © 2014, Taylor & Francis.