The ability of nanoparticles to deliver payloads of cancer-fighting drugs to tumors could herald a fundamental change in chemotherapy treatment. One problem still to be overcome is that most nanoparticles are removed by the liver and spleen before they reach their target.

Andre Nel and co-workers, University of California, Los Angeles, USA, have significantly increased the percentage of drug-carrying nanoparticles that reach and are retained at tumor sites. The team uses mesoporous silica nanoparticles stabilized by a polyethyleneimine–polyethylene glycol copolymer.

The advance came from the choice of particle size; the particles were 50 nm in diameter, smaller than most nanoparticles used for drug delivery. The preferred particle size is generally 50–100 nm. This simple modification led to 10–12 % of the injected drug reaching the tumor site, compared to the usual 3–10 %.

• Use of Size and a Copolymer Design Feature To Improve the Biodistribution and the Enhanced Permeability and Retention Effect of Doxorubicin-Loaded Mesoporous Silica Nanoparticles in a Murine Xenograft Tumor Model
  H. Meng, M. Xue, T. Xia, Z. Ji, D. Y. Tarn, J. I. Zink, A. E. Nel,
  ACS Nano 2011.
  DOI: 10.1021/nn200809t