Synthesis and Fluorescence Properties of N-Substituted 1-Cyanobenz[f]isoindole Chitosan Polymers and Nanoparticles for Live Cell Imaging

Abstract

Highly fluorescent N-substituted 1-cyanobenz[f]isoindole chitosans (CBI-CSs) with various 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. Introduction of 1-cyanobenz[f]isoindole moieties into the CS backbone resulted in lowering of polymer thermal stability and crystallinity. The fluorescence quantum yield (Φf) of CBI-CS was found to be DS- and molecular-weight-dependent, with Φf decreasing as DS and molecular weight were increased. At similar DS values, CBI-CS exhibited 26 times higher Φf in comparison with fluorescein isothiocyanate-substituted chitosan (FITC-CS). CBI-CS/TPP nanoparticles were fabricated using an ionotropic gelation method in which pentasodium triphosphate (TPP) acted as a cross-linking agent. CS and CBI-CS exhibited low cytotoxicity to normal skin fibroblast cells over a concentration range of 0.1-1000 μg/mL, while an increased cytotoxicity level was evident in CBI-CS/TPP nanoparticles at concentrations greater than 100 μg/mL. In contrast with CBI-CS polymers, the CBI-CS/TPP nanoparticles exhibited lower fluorescence; however, confocal microscopy results showed that living normal skin fibroblast cells became fluorescent on nanoparticle uptake. These results suggest that CBI-CS and fabricated nanoparticles thereof may be promising fluorescence probes for live cell imaging.

Fluorescent Property of Chitosan Oligomer and Its Application as a Metal Ion Sensor

“…Also, the degree of substitution (DS) of the complexes is ascertained by recording 1 H nuclear magnetic resonance (1H NMR) spectra on a NMR spectrometer (300 MHz, FT-NMR, Bruker). The DS (%) values were expressed as (I AR /9)/(I H2-H6 /6) × 100 [7]. I AR and I H2-H6 indicated peak areas of aromatic protons in FITC and C2-C6 protons in the chitosan backbone, respectively.…”

“…Some dyes, such as Alexa Fluor, Cibacron Blue, and fluorescein isothiocyanate (FITC), have been used to create a dye-labeled chitosan particulate system [6]. However, a significant part of such approaches uses chemical reagents in the synthesis of dye-labeled chitosan due to its low solubility in water [7]. Numerous studies have addressed the utilization of chitosan as a fluorescence probe [8,9].…”

Fluorescent Chitosan Modified with Heterocyclic Aromatic Dyes

“…A 2% solution of chitosan (in 1% CH 3 COOH) at a volume of 20 mL was mixed with a 1% methanolic solution of dye (10 mL). The synthesis was carried out according to the described procedure in [ 44 ] ( Scheme 2 ). The combined solutions were vigorously stirred with a magnetic stirrer for 24 h in darkness at room temperature.…”

“…The degree of N -substitution (DS) was calculated using NMR spectroscopy according to the methodology proposed by Gonil [ 44 ] and Jatunov et al [ 45 ].…”

Fluorescent imino and secondary amino chitosans as potential sensing biomaterials

“…So far, fluorescent chitosan amino complexes and derivatives have been prepared for drug releasing (Cui et al, 2011), tissue engineering applications (Cunha-Reis, El Haj, Yang, & Yang, 2013), and live cell imaging (Gonil et al, 2014), among other applications.…”