"We have shown that coating MWCNTs with the polymer Pluronic F108 makes the tubes disperse more easily and also reduces their surface reactivity," team member Xiang Wang told nanotechweb.org. "Surface reactivity is responsible for inflammatory reactions in lung cells, for example."

The researchers say that such potentially hazardous interactions take place inside cellular structures called lysosomes. Damaged lysosomes in lung macrophages switch on pathways that ultimately lead to chronic inflammation and fibrosis, explains Wang.

The team also coated the nanotubes with bovine serum albumin and a phospholipid, but these coatings had the opposite effect, with the tubes inducing high levels of inflammatory biomarkers in mice lung cells.

Brush-like protective structure

According to the team, PF108 forms a protective brush-like structure on the surface of the nanotubes that stabilizes the tubes inside lysosomes and prevents the nanomaterials from interacting with the lysosomal membrane.

"We believe that PF108 could be used as a coating for MWCNTs so that they can be more safely used in nanotherapeutics, diagnosis and imaging," said Wang. "Our study also demonstrates the principle of ‘safe-by-design’ strategies for nanomaterials in general by rationally changing the surface properties of a material."

The same group has already performed similar experiments on zinc oxide nanoparticles and silver nanoplates and has found that certain shapes are safer than others. The researchers plan to continue their studies on a wider range of nanomaterials still, such as those routinely being used in industry.

The present work is described in Nano Letters.