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Highly fluorescent N-substituted1-cyanobenz[f]isoindole chitosans (CBI-CSs) withvarious degrees of N-substitution(DS) were synthesized by reacting chitosan (CS) with naphthalene-2,3-dicarboxaldehyde(NDA) in the presence of cyanide under mild acidic conditions. Introductionof 1-cyanobenz[f]isoindole moieties into the CS backboneresulted in lowering of polymer thermal stability and crystallinity.The fluorescence quantum yield (Φf) of CBI-CS wasfound to be DS- and molecular-weight-dependent, with Φfdecreasing as DS and molecular weight were increased. At similarDS values, CBI-CS exhibited 26 times higher Φfincomparison with fluorescein isothiocyanate-substituted chitosan (FITC-CS).CBI-CS/TPP nanoparticles were fabricated using an ionotropic gelationmethod in which pentasodium triphosphate (TPP) acted as a cross-linkingagent. CS and CBI-CS exhibited low cytotoxicity to normal skin fibroblastcells over a concentration range of 0.1–1000 μg/mL, whilean increased cytotoxicity level was evident in CBI-CS/TPP nanoparticlesat concentrations greater than 100 μg/mL. In contrast with CBI-CSpolymers, the CBI-CS/TPP nanoparticles exhibited lower fluorescence;however, confocal microscopy results showed that living normal skinfibroblast cells became fluorescent on nanoparticle uptake. Theseresults suggest that CBI-CS and fabricated nanoparticles thereof maybe promising fluorescence probes for live cell imaging. [ABSTRACT FROM AUTHOR]