Antimicrobial properties of nanorods: Chemical or physical kill?

Silver is known to possess antimicrobial properties that are of chemical origin. It is believed that either Ag atoms bind to thiol groups in bacterial enzymes, or Ag+ ions enter bacterial cells and denature the DNA molecule, to kill bacteria. In the case of silver nanorods, it is also possible that the tips of nanorods puncture bacterial cells and kill bacteria via a physical mechanism. To test this conjecture, we have compared the antimicrobial properties of silver and CdS nanorods. No significant difference is found between the two even though CdS does not possess the chemical properties of silver. This indicates that the physical kill mechanism may be more important than the chemical one and that nanorods of any material may possess antimicrobial properties. In that case, it is possible to overcome serious short and long term health hazard issues which have been posed by silver nanoparticles.