Gold Nanoparticle Mediated Phototherapy for Cancer

Figure 16

Physical characteristics of nanoparticles determine in vivo biocompatibility. The three-dimensional phase diagram displays the qualitative biocompatibility trends revealed after in vivo screening of around 130 nanoparticles intended for therapeutic use. The main independent particle variables that determine the in vivo biocompatibility (colour spectrum) are size, zeta potential (surface charge), and dispersibility (particularly the effect of hydrophobicity). Biocompatibility is reflected in the colour spectrum, with red representing likely toxicity, blue likely safety, and blue–green–yellow intermediate levels of safety (in the same order). Cationic particles or particles with high surface reactivity are more likely to be toxic (red hue) than the larger relatively hydrophobic or poorly dispersed particles, which are rapidly and safely (blue hue) removed by the reticuloendothelial system (RES). Particles that promote enhanced permeation and retention (EPR) effects—and are therefore optimal for chemotherapeutic drug delivery to cancers—generally have midrange sizes and relatively neutral surface charges. Reprinted by permission from Macmillan Publishers Ltd.: [Nature Materials] [51]. Copyright 2009.