Two South Korean scientists recently published a research paper on the issue of whether different shapes of nanosilver particles have different antibacterial properties. The short answer is apparently “yes.”

See Pal, S., et al., "Does Antibacterial Activity of Silver Nanoparticles Depend on the Shape of Nanoparticle? A Study of the Gram-Negative Bacterium Eschericha coli," Applied Environmental Microbiology, Vol. 73, No. 6, 1712-20 (March 2007).

The authors started the article by noting that “silver has been employed most extensively since ancient times to fight infections and control spoilage,” and “ . . . in minute concentrations, silver is nontoxic to human cells. The epidemiological history of silver has established its non toxicity in normal use.” Their specific experiment exposed E. coli bacteria to three different shapes of nanoparticles: (1) truncated triangular nanoplates; (2) spherical; and (3) rods. Of the three shapes, the truncated triangular nanoplates had the greatest antibacterial properties.

The authors concluded that “[t]he difference in the observed trends in E. coli inhibition can be explained in terms of the percent of active facets present in nanoparticles of different shapes. Truncated triangular silver nanoplates, with {111} active facets, exhibited higher inhibition than spherical nanoparticles and pentagonal rods, both of which have primarily {100} active facets (with lesser amounts of {111} active facets). The authors speculate that "silver nanoparticles with the same surface areas but with different shapes may also have different effective surface areas in terms of active facets.”