SERS-Based Flavonoid Detection Using Ethylenediamine-β-Cyclodextrin as a Capturing Ligand

Abstract

Ethylenediamine-modified β-cyclodextrin (Et-β-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO2@Ag@Et-β-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) signals. Et-β-CD was immobilized on Ag NPs to capture flavonoids via host-guest inclusion complex formation, as indicated by enhanced ultraviolet absorption spectra. The resulting SiO2@Ag@Et-β-CD NPs were used as the SERS substrate for detecting flavonoids, such as hesperetin, naringenin, quercetin, and luteolin. In particular, luteolin was detected more strongly in the linear range 10−7 to 10−3 M than various organic molecules, namely ethylene glycol, β-estradiol, isopropyl alcohol, naphthalene, and toluene. In addition, the SERS signal for luteolin captured by the SiO2@Ag@Et-β-CD NPs remained even after repeated washing. These results indicated that the SiO2@Ag@Et-β-CD NPs can be used as a rapid, sensitive, and selective sensor for flavonoids.

Functionalized β-Cyclodextrin Immobilized on Ag-Embedded Silica Nanoparticles as a Drug Carrier

“…To allow the stable and dense immobilization of β -CD derivatives, Ag NPs were embedded on the SiO 2 NP surface by the reduction of silver nitrate with octylamine. Three kinds of ligands (cysteinyl- β -CD, EDA- β -CD, and methoxypoly(ethylene glycol)sulfhydryl [m-PEG-SH]), prepared following previously reported methods [25,28], were added after the synthesis of SiO 2 @Ag NPs. Cysteinyl- β -CD and EDA- β -CD (Figure 1b) were selected as functionalized β -CDs because they are known to effectively capture DOX and the thiol group of cysteinyl- β -CD and diamine of EDA- β -CD have strong affinity to metal surfaces [23].…”

“…However, the loading of DOX depends on types of the functional group of β -CD previously reported by our group. Ethylenediamine β -CD derivative can captured various flavonoids [25]. We believed that not only cavity but also the exterior part of β -CD can interact selectively with DOX.…”

“…Ethyl alcohol (EtOH) and aqueous ammonium hydroxide (NH 4 OH, 27%) were purchased from Daejung (Siheung, Korea). Designed cysteinyl- β -CD and EDA- β -CD were obtained from the Microbial Carbohydrate Resource Bank (MCRB) at Konkuk University, Korea [25,28], and m-PEG-SH (M.W. 5000) was purchased from Sunbio (Anyang, Korea).…”

“…Using the SiO 2 @Ag NP structure, a target material can be detected by introducing β -CD, which is used as a capture ligand. Functionalized β -CD included amine (ethylenediamine) and thiol (cysteinyl) group was introduced on the metal surface [24,25]. Detection using the assembled structure and β -CD has been reported, but subsequent analyses of drug delivery are lacking.…”

Mono-6-Deoxy-6-Aminopropylamino-β-Cyclodextrin on Ag-Embedded SiO2 Nanoparticle as a Selectively Capturing Ligand to Flavonoids

“…Ag-embedded silica nanostructures also produced a highly reproducible SERS signals and could be scaled up [21]. As a result, highly sensitive detection of polycyclic aromatic hydrocarbons (PAHs), flavonoids, and the like was successfully developed [23,24,25,26,27]. Subsequently, β -CD dimer was attached on the surface of Ag-embedded SiO 2 NPs to develop the detection of PAHs in our group.…”