• Silver nanoparticles embedded on clay have now been successfully dispersed inside plastic to create new antimicrobial films, filaments and can also be moulded into other plastic items.
  • Silver nanoparticle-embedded plastics were found to have greater than 99% antibacterial activity against common bacterial pathogens like Escherchia coli and Staphylococcus aureus.
  • Silver nanoparticles of about 10 nanometre size were deposited on clay particles of about 200-300 nanometre length.
  • We used an inorganic clay found in volcanic sites called Montmorillonite.
  • Silver nanoparticles have a tendency of agglomeration or clumping due to high surface area, so we provided clay as a platform for the silver to sit on.
  • The clay–silver compound, containg 10% silver, was then loaded into the high density polyethylene plastic using a melt compounding method.
  • The clay is inorganic and highly hydrophilic, whereas our plastic is organic, hydrophobic and nonpolar.
  • They are highly incompatible.
  • So we use a compatibilizer, which gives the required adhesion between the two phases.
  • Also, inside the twin screw extruder machine, the necessary speed, temperature and time gives uniform mixing and the silver-clay is well embedded inside the plastic.

 Tell us more on Films and filaments

  • They then converted the newly formed silver–clay–plastic nanocomposite into films, filaments and also moulded these into specimens and checked the antibacterial property.
  • The films and filaments showed higher activity than the moulded ones.
  • In the moulded ones, we found that the antimicrobial silver was not available on the surface leading to the reduction in activity.
  • But when the concentration of silver–clay complex was increased from 3% to 5%, the moulded ones also showed excellent activity against the two pathogens.
  • The team also tried other metal ions like zinc and copper in the place of silver.
  • Silver has a high reduction potential, meaning it can quickly go from silver ions to silver nanoparticles without the need of any external reducing agent.
  • These silver nanoparticles interact with the bacterial cell wall and also generate oxidative stress inside the cell, thus killing it.
  • The content of silver is very low in these nanocomposite plastic so no toxicity to human cells.
  • In vivo tests are in progress and we hope that the new plastic can find a wide range of applications in the biomedical field and also in commodity items where this antimicrobial property can be an added advantage.