Three pharmacologists from McGill University recently published a paper concerning in vitro biological cell reponse to various types of internalized nanoparticles. Despite its hyperbolic title, the study makes some interesting observations.
First, the paper finds that no categorical conclusions can be drawn from existing testing data and much more research is necessary in this area. At the center of this lack of data, the articled notes several of the many variables affecting cellular response: "Depending on the kind of nanoparticles, the type of cells, the duration of exposure, the concentration of nanoparticles and the conditions under which cell-nanoparticle interaction takes place, different cells will either ‘tolerate’ nanoparticles or succumb to their ‘attack.’" Given these variables and the relative adolescence of nanotechnology, it is easy to understand why is is difficult to draw overall conclusions from existing data.
Next, regarding different kinds of nanoparticles, the study examined five nanoparticles classes: (i) uncoated quantum dots (PbSe, CdTe, ZnSe, and CdSe), (ii) coated quantum dots (CdTe, CdSe), (iii) micelles (PCL), (iv) gold particles (AU4VP), and (v) spiones (Fe). The authors noted numerous characteristics of these classes of nanoparticles affect their alleged cell toxicity, including nanoparticle class, core material, particle size, surface charge, stability, possible ligand attachments, and concentrations. Again, the sheer number of variables helps explain the lack of conclusive data.
Finally, concerning the type of cells actually tested, the authors noted "the fate of cells exposed to nanoparticles will depend on: their tissue of origin and differentiation state, and their redox state. In addition to this, plating, cell density, composition of the medium, presence and absence of serum or defined trophic factors in chemically defined media will also be critical to the final outcome. The combination of the physical and chemical factors of QDs, the cellular environment, and the status of the cells determine cell fate: survival, death or differentiation. " Again, variability is the key.
The "take away" from the article is that some types of cells may react adversley to certain types of internalized nanoparticles under some circumstances. While no global conclusions are readily available, the article nonetheless urges caution in the development of certain nanomaterial applications for use in the human body.
D. Maysinger, et al., "Death by Nanoparticles," NanoPharmaceuticals Online Journal, Vol. 1, Oct. 2006, published by Nanopharmaceuticals.org