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

Abstract

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

“Turn-On” Fluorescence Determination of β-Glucosidase Activity Using Fluorescent Polymer Nanoparticles Formed from Polyethylenimine Cross-Linked with Hydroquinone

“…Nonemissive PEI was treated with hydroquinone at different concentrations at 60 °C for 90 min. Hyperbranched PEI, a dendritic polymer, contains abundant active amine groups on both the backbone and branch chains . It has previously been found that phenolic compounds in an alkaline solution are easily oxidized by ambient O 2 . − Hydroquinone was oxidized to p -benzoquinone when PEI was added to the solution.…”

Targeted Delivery of Sucrose‐Coated Nanocarriers with Chemical Cargoes to the Plant Vasculature Enhances Long‐Distance Translocation

“…To assess the potential of targeted nanocarriers for chemical delivery to the plant vasculature, we used a model fluorescent chemical cargo, rhodamine 6G (R6G), that can be loaded in β‐cyclodextrins and delivered by nanocarriers ( Figure a). The quenching response of R6G caused by the reaction with β‐cyclodextrin through electron transfer, [ 99 ] indicates loading of R6G into these molecular baskets (Figure 5b). As the concentration of β‐cyclodextrin increases, the R6G fluorescence intensity decreases up to 0.02 µM concentration where there is a saturation of chemical cargo loaded on β‐cyclodextrins (Figure 5c).…”

Colorimetric Detection of Aliphatic Alcohols in β-Cyclodextrin Solutions

“…The higher signal dispersion that was observed when using 2-HP-β-CD is likely due to strong binding between the dyes and 2-HP-β-CD as well as the high flexibility and water solubility of 2-HP-β-CD compared to the other hosts investigated . High binding constants between the alcohol analytes and cyclodextrin hosts increase the strength of interactions between the analyte, host, and dye, resulting in more sensitive analyte-induced signal changes, whereas greater flexibility and water solubility increase the availability of this host to participate in the desired interactions. − Of note, control experiments conducted in the absence of cyclodextrin resulted in markedly lower dispersion of the signals with significant misclassification of the analytes observed.…”