Antimicrobial properties of nanorods: killing bacteria via impalement.

Silver is known to possess anti-microbial 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. Silver nanorods, however, may kill bacteria by another mechanism: it is possible that the sharp tips of the nanorods puncture bacterial cells and kill bacteria via impalement-a physical mechanism. To test if this can indeed happen, we have compared the anti-microbial 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 is indeed likely and therefore nanorods of any material may possess anti-microbial properties. In that case, it is possible to overcome serious short- and long-term health hazard issues which have been posed by silver nanoparticles by replacing them with nanorods of innocuous elements or compounds. A surface containing nanorods of varying heights presents an undulating bed of spikes to microbes and is most inhospitable to bacteria.