Naphthalimide based fluorescent organic nanoparticles in selective sensing of Fe3+ and as a diagnostic probe for Fe2+/Fe3+ transition

Fluorescent organic nanoparticles (FONPs) have attracted considerable attention as a practical and effective platform for sensing and imaging applications. The present article delineates the fabrication of FONPs derived from the naphthalimide based histidine appended amphiphile, NID. The self-assembly of NID in 99 vol% water in DMSO Led to the formation of FONPs through J-type aggregation. Aggregation-induced emission (AIE) was observed due to the pre-associated excimer of NID with bluish green emission at 470 nm along with intramolecular charge transfer (ICT). The emission of NID FONPs was utilized for selective sensing of Fe3+ and bioimaging of Fe3+ inside mammalian cells. The fluorescence intensity of the FONPs was quenched with the gradual addition of Fe3+ due to the formation of a 1:1 stoichiometric complex with the histidine residue of NID. The morphology of the FONPs transformed from spherical to spindle upon the complex formation of NID with Fe3+. The Limit of detection (LOD) of this AIE based turn-off chemosensor for Fe3+ was found to be 12.5 +/- 1.2 mu M having high selectivity over other metal ions. On the basis of the very Low cytotoxicity and selective sensing of Fe3+ , NID FONPs were successfully employed for bioimaging of Fe3+ ions through fluorescence quenching within mammalian cells (NIH3T3, B16F10). Considering the varying oxidative stress inside different cells, NID FONPs were used for detecting Fe2+ to Fe3+ redox state transition selectively inside cancer cells (B16F10) in comparison to non-cancerous cells (NIH3T3). Selective sensing of cancer cells was substantiated by co-culture experiment and flow cytometry. Hence, NID FONPs can be a selective diagnostic probe for cancer cells owing to their higher H2O2 content.

Automated summary

Fluorescent organic nanoparticles (FONPs) derived from naphthalimide-based amphiphile NID were fabricated, showing aggregation-induced emission (AIE) and intramolecular charge transfer (ICT) properties. These FONPs were used for selective sensing of Fe3+ and bioimaging within mammalian cells, with a low limit of detection and high selectivity over other metal ions. Additionally, NID FONPs showed promise as a diagnostic probe for cancer cells based on their selective sensing of Fe2+ to Fe3+ redox state transition.