amount of undigested probes on the electrode surface was obviously dependent on
the concentration of active hOGG 1, which allowed the quantitative assay of target
DNA glycosylase.
9.2.5 Small Molecule Determination
With the advancement of supermolecular chemistry, indicator displacement assay
(IDA) via the competitive recognization between a test substance and an indicator
with the same binding site on the host has aroused considerable research interest for
optical (mostly fluorescent and colorimetric) sensing applications [69–71]. For
instance, a novel pillararene-indicator system between WP6 and AO was proposed
[14]. As shown in Fig. 10a, the complexation between WP6 and AO (WP6 ' AO)
gave rise to a significant decrease in the fluorescence emission of AO due to the hostguest charge-transfer interactions. Upon subsequent introduction of choline (Ch), the
yellow-green fluorescence of AO recovered. With the similar binding affinity for
WP6, the analogical phenomenon also could be observed after the addition of
acetylcholine (ACh). When the host molecule was replaced by WP5, AO exhibited
a size-selective complexation and could not enter into the electron-rich cavity of
WP5. Moreover, the constructed pillararene-indicator system was further employed
in the monitoring of enzymatic reactions catalyzed by choline oxidase (Fig. 10b). It
is clear that WP6 showed distinctly different binding affinities with a substrate
(Ch) and a product (betaine, Bt) in the catalytic process of choline oxidase. Thus,
the different displacement efficiencies of Bt and Ch from WP6 ' AO complex
motivated the IDA-induced fluorescence variation mechanism. By adopting the IDA
system, van der Wall et al. also designed a supermolecular colorimetric sensing
strategy for drug detection in urine of a model therapeutic peptide drug octreotide
based on the cucurbit[7]uril/neutral red (CB[7]/NR) host-indicator complexes [72].
Wang’s group constructed a stable and sensitive supermolecular fluorescent
nanoparticles system via the multiple noncovalent interactions for the detection of
intracellular H 2 O 2 (Fig. 11) [73]. Rhodamine B-modified ferrocene derivative
(Fc-RB) in aqueous solution was able to form an inclusion complex with fluorescein
isothiocyanate-modified β-CD (FITC-β-CD) by the host-guest interaction between
β-CD host and Fc guest. Due to the collaborative stabilization of hydrophobic
interaction, FITC-β-CD/Fc-RB complex with inherent amphiphilicity could selfassemble into stable supermolecular nanoparticles under physiological conditions
and exhibit strong fluorescence resonance energy transfer (FRET) effect, accompanied with the strong emission from RB (acceptor) and low emission from FITC
(donor). When the supermolecular nanoparticles were internalized by cancer cells,
the endogenous H 2 O 2 could disrupt FITC-β-CD/Fc-RB amphiphilicity and inhibit
FRET effect, which finally led to the decrease in acceptor emission and increase in
donor emission. In terms of the remarkable fluorescence changes, the formed
supermolecular nanoparticles realized the sensitive monitoring of H 2 O 2 in cancer
cells and might have potentials in cell imaging. Li and coworkers established a
tunable fluorescent supermolecular system in aqueous solution via the host-guest
9 Preparation of Biosensor Based on Supermolecular Recognization
243
the concentration of active hOGG 1, which allowed the quantitative assay of target
DNA glycosylase.
9.2.5 Small Molecule Determination
With the advancement of supermolecular chemistry, indicator displacement assay
(IDA) via the competitive recognization between a test substance and an indicator
with the same binding site on the host has aroused considerable research interest for
optical (mostly fluorescent and colorimetric) sensing applications [69–71]. For
instance, a novel pillararene-indicator system between WP6 and AO was proposed
[14]. As shown in Fig. 10a, the complexation between WP6 and AO (WP6 ' AO)
gave rise to a significant decrease in the fluorescence emission of AO due to the hostguest charge-transfer interactions. Upon subsequent introduction of choline (Ch), the
yellow-green fluorescence of AO recovered. With the similar binding affinity for
WP6, the analogical phenomenon also could be observed after the addition of
acetylcholine (ACh). When the host molecule was replaced by WP5, AO exhibited
a size-selective complexation and could not enter into the electron-rich cavity of
WP5. Moreover, the constructed pillararene-indicator system was further employed
in the monitoring of enzymatic reactions catalyzed by choline oxidase (Fig. 10b). It
is clear that WP6 showed distinctly different binding affinities with a substrate
(Ch) and a product (betaine, Bt) in the catalytic process of choline oxidase. Thus,
the different displacement efficiencies of Bt and Ch from WP6 ' AO complex
motivated the IDA-induced fluorescence variation mechanism. By adopting the IDA
system, van der Wall et al. also designed a supermolecular colorimetric sensing
strategy for drug detection in urine of a model therapeutic peptide drug octreotide
based on the cucurbit[7]uril/neutral red (CB[7]/NR) host-indicator complexes [72].
Wang’s group constructed a stable and sensitive supermolecular fluorescent
nanoparticles system via the multiple noncovalent interactions for the detection of
intracellular H 2 O 2 (Fig. 11) [73]. Rhodamine B-modified ferrocene derivative
(Fc-RB) in aqueous solution was able to form an inclusion complex with fluorescein
isothiocyanate-modified β-CD (FITC-β-CD) by the host-guest interaction between
β-CD host and Fc guest. Due to the collaborative stabilization of hydrophobic
interaction, FITC-β-CD/Fc-RB complex with inherent amphiphilicity could selfassemble into stable supermolecular nanoparticles under physiological conditions
and exhibit strong fluorescence resonance energy transfer (FRET) effect, accompanied with the strong emission from RB (acceptor) and low emission from FITC
(donor). When the supermolecular nanoparticles were internalized by cancer cells,
the endogenous H 2 O 2 could disrupt FITC-β-CD/Fc-RB amphiphilicity and inhibit
FRET effect, which finally led to the decrease in acceptor emission and increase in
donor emission. In terms of the remarkable fluorescence changes, the formed
supermolecular nanoparticles realized the sensitive monitoring of H 2 O 2 in cancer
cells and might have potentials in cell imaging. Li and coworkers established a
tunable fluorescent supermolecular system in aqueous solution via the host-guest
9 Preparation of Biosensor Based on Supermolecular Recognization
243