- 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.
