Calcein as a fluorescent iron chemosensor for the determination of low molecular weight iron in biological fluids

Aktar Ali, Qi Zhang, Jisen Dai, Xi Huang

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


The fluorescence quenching of calcein (CA) is not iron specific and results in a negative calibration curve. In the present study, deferoxamine (DFO), a strong iron chelator, was used to regenerate the fluorescence quenched by iron. Therefore, the differences in fluorescence reading of the same sample with or without addition of DFO are positively and specifically proportional to the amounts of iron. We found that the same iron species but different anions (e.g. ferric sulfate or ferric citrate) differed in CA fluorescence quenching, so did the same anions but different iron (e.g. ferrous or ferric sulfates). Excessive amounts of citrate competed with CA for iron and citrate could be removed by barium precipitation. After optimizing the experimental conditions, the sensitivity of the fluorescent CA assay is 0.02 μM of iron, at least 10 times more sensitive than the colorimetric assays. Sera from 6 healthy subjects were tested for low molecular weight (LMW) chelator bound iron in the filtrates of 10 kDa nominal molecular weight limit (NMWL). The LMW iron was marginally detectable in the normal sera. However, increased levels of LMW iron were obtained at higher transferrin (Tf) saturation (1.64-2.54 μM range at 80% Tf saturation, 2.77-3.15 μM range at 100% Tf saturation and 3.09-3.39 μM range at 120% Tf saturation). The application of the assay was further demonstrated in the filtrates of human liver HepG2 and human lung epithelial A549 cells treated with iron or iron-containing dusts.

Original languageEnglish (US)
Pages (from-to)285-293
Number of pages9
Issue number2
StatePublished - Jun 2003


  • Calcein
  • Iron
  • Iron overload
  • Low molecular weight iron
  • Non-transferrin bound iron

ASJC Scopus subject areas

  • Biomaterials
  • General Biochemistry, Genetics and Molecular Biology
  • General Agricultural and Biological Sciences
  • Metals and Alloys


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