3, 10, 50, and 100 nm Ag and Au nanoparticles seems best for cancer treatment, while 8−37 nm AuNPs induced fatigue, loss of appetite, change of fur color, and weight loss in mice.

Ref: Functional Nanomaterials for Phototherapies of Cancer published in Chemical Reviews ( dx.doi.org/10.1021/cr400532z | Chem. Rev. 2014, 114, 10869−10939 ) Also go through Ref. 116 in this publication.

Maria-Dolores Rivera , I hope that following publication will be helpful:

Article Silver nanoparticles exhibit size-dependent differential tox...

Maria-Dolores Rivera There are no conclusive experiments to prove particular size of AgNP is good to treat cancers. The optimal size to their use in cancer is largely contingent on type of cancer and molecular background of carcinogenesis. Moreover, shape of AgNPs is also a significant determinant of their activity. AgNPs of same size with different shapes may not be equally effective.

In our recent experiments on AgNP size dependent inhibition of MDR1 in MDR breast cancer cells, we observed that 5 nm AgNPs were more cytotoxic and potent mitotoxicity inducers but poor inhibitors of MDR1. In contrast 75 nm AgNPs were potent inhibitors of MDR1 but poor inducers of cytotoxicity and mitotoxicity.

Hope this answer helps you.

Mohana Krishna Gopisetty Thanks much for adding much details and clarification. I would like to add, in case of different shapes, they are supposed to be called nanostructures rather than nanoparticles. Nanoparticles is specifically termed for spherical nanostructures.

For the preparation of nanodevices, from silver or gold nanoparticles work as drug delivery systems, the best size distribution is so small as possible (< 10 nm if you are looking for the uptake of nanocarrier by the cell). However, this size range is not the best for studying the adsorption of each component of the preparation (nanodevice) through SERS spectroscopy, since resonance conditions with higher enhancements are in visible excitations, with nanoparticle sizes around 30-50 nm (J. Raman Spectr., v. 40, p. 183-190, 2009).

Muhammad Abbas yes I agree with you. they are nano-structures if their shape greatly varies from exact spheres. little variations like in Quasi spherical nano structures are frequently referred as nanoparticles and even this small variety in shape greatly varies their biological properties.

I am a bit confused with this discussion. Personally, I don't think the size of the nanoparticle is the critical issue. The important thing is what you do with them- how you tag the chemotherapeutic agent, how you direct the functionalised nanoparticle to the cancer tissue, the mechanics of drug release, the mode of cell kill (chemotherapy or thermal or something else) and the fate of the nanoparticle after it has done its job. Cancer therapy is multi-facetted and focusing on one aspect of the therapy (size of the particle) may be ill advised..

Thank you.

Any nanocarrier in the size range of 100 to 150 nm including metal nanoparticles will accumulate in cancers tissue more (EPR effect) because the endothelial which layer to tumor has more pore size e.i. 100 nm (extravasation) as compare to normal tissue.

One or more external dimensions are in the size range 1–100 nm

Reference:

D. R. Boverhof, C. M. Bramante, J. H. Butala et al., “Comparative assessment of nanomaterial definitions and safety evaluation considerations,” Regulatory Toxicology and Pharmacology, vol. 73, no. 1, pp. 137–150, 2015. View at Publisher · View at Google Scholar · View at Scopus

S. Darby, P. McGale, C. Correa et al., “Effect of radiotherapy after breast-conserving surgery on 10-year recurrence and 15-year breast cancer death: meta-analysis of individual patient data for 10 801 women in 17 randomised trials,” The Lancet, vol. 378, no. 9804, pp. 1707–1716, 2011. View at Publisher · View at Google Scholar · View at Scopus