Turn-on fluorometric β-carotene assay based on competitive host-guest interaction between rhodamine 6G and β-carotene with a graphene oxide functionalized with a β-cyclodextrin-modified polyethyleneimine

The authors describe a turn-on fluorometric method for determination of beta-carotene. It is based on competitive host-guest interaction between rhodamine 6G (R6G) and beta-carotene and graphene oxide nanoparticles that were functionalized with beta-cyclodextrin (beta-CD)-modified polyethylenimine (beta-CD-PEI-GO). On addition of R6G to a solution of beta-CD-PEI-GO, its fluorescence is quenched because of the inclusion of R6G into the beta-CD moiety. Both Forster resonance energy transfer and electron transfer are likely to occur. On further addition of a sample containing beta-carotene, it will replace R6G in the cavity, thereby releasing R6G to the bulk solution. This is due to the stronger affinity of beta-carotene for beta-CD in the complex, but also because of repulsion between the positively charged beta-CD-PEI-GO complex and the positively charged R6G dye. The displacement of R6G by beta-carotene leads to fluorescence recovery whose efficiency (expressed as F/F-0) is related to the beta-carotene concentration in the range from 0.1 to 4.0 mu mola <...LaEuro3/4(1). The detection limit for beta-carotene is 5.4 nmola <...LaEuro3/4(1) which is lower than that of any other optical method.