Intracellular localisation, geno- and cytotoxic response of polyN-isopropylacrylamide (PNIPAM) nanoparticles to human keratinocyte (HaCaT) and colon cells (SW 480)

PNIPAM nanoparticles, with and without a covalently linked fluorescent label, were prepared by a free radical polymerisation technique. The cyto- and genotoxicity of PNIPAM nanoparticles were analysed in two representative mammalian cell lines, SW480, a colon, and HaCaT, a dermal cell line. Physical characterisation in terms of particle size and zeta potential of the PNIPAM nanoparticles was carried out both in aqueous solution and in the appropriate cell culture media. Uptake and co-localisation of fluorescently labelled PNIPAM nanoparticles was monitored in both cell lines using confocal laser scanning microscope. Genotoxicity analysis using the Comet assay was performed in both cell lines to evaluate any DNA damage. It was observed that the PNIPAM nanoparticles were internalized and localised in lysosomes within 24 h. No significant cytotoxic response (p ≤ 0.05) was observed in either cell line over concentration ranges from 25 to 1000 mg/l for all exposure time periods. Furthermore, no significant genotoxic response (p ≤ 0.05) was observed in either cell line over concentration ranges from 12.5 to 800 mg/l for all exposure time periods. The results suggest that the PNIPAM nanoparticles show excellent biocompatibility in vitro.