(PAMAM) dendrimers to prevent nanoparticle aggregation [38, 39], PAMAMencapsulated Au nanoparticles (PAMAM-Au) acted as nanocarriers anchored large
amounts of amine-terminated β-CD by the chemical absorption interaction. With the
unique structure of two ferrocene units, the as-synthesized N,N-bis(ferrocenoyl)
diaminoethane (Fc-Fc) as a bridge could bind two β-CD molecules via the hostguest recognization and form the supermolecular net structure of Fc-Fc/β-CD/
PAMAM-Au signal probe. Finally, secondary antibody (Ab 2 ) was attached to the
netlike probe for the generation of Fc-Fc/β-CD/PAMAM-Au-labeled Ab 2
bioconjugates. The electrochemical immunosensing platform was prepared by the
stepwise modification of electrochemically deposited Au nanoflower (DpAu), primary antibody (Ab 1 ), and bovine serum albumin (BSA) on the surface of glassy
carbon electrode (GCE). After PCT was introduced to the sensing system,
Fc-Fc/β-CD/PAMAM-Au-labeled Ab 2 bioconjugates could be captured by the sandwich conformation-dependent immunoreaction, and then a “signal-on” differential
pulse voltammetry (DPV) oxidation peak of ascorbic acid (AA) was obtained by the
enzyme-free dual amplification strategy, which was composed of the synergetic
catalytic activity of PAMAM-Au and Fc-Fc (Fig. 4b). Under the optimal experimental conditions, the electrochemical immunosensor toward the detection of PCT
exhibited a wide linear range of 1.8 pg mL
–1
–500 ng mL
À1 with a low detection limit
of 0.36 pg mL
À1 . Bimetallic alloy nanoparticle often exhibits enhanced selectivity
and catalytic activity in comparison to their single-metallic components, and both
magnetic and optical characteristics can be fine-regulated via changing the metal
ratios in alloy systems [40, 41]. Based on this, Du et al. firstly selected a facile
microwave-assisted approach to synthesize N-doped graphene nanoribbons
(N-GNRs) from N-doped multi-walled carbon nanotubes (N-MWCNTs), and PdNi
alloy nanoparticles with an average size of 10 nm were reduced in situ on the surface
of N-GNRs to produce PdNi/N-GNRs nanocomposites in the presence of ethylene
glycol and glutamate [42]. The electrochemical immunosensing biosensor was
constructed through the sequential assembly of β-CD-functionalized graphene sheets
(CD-GS), adamantine-1-carboxylic acid-functionalized Ab 1 (ADA-Ab 1 ), and BSA
on GCE surface, and subsequent addition of alpha fetoprotein (AFP) resulted in the
catch of PdNi/N-GNRs-immobilized Ab 2 (PdNi/N-GNRs-Ab 2 ) to generate a distinct
amperometric response via the catalysis of the reduction of H 2 O 2 . Taking advantages
of the high electrocatalytic activity of PdNi/N-GNRs and enhanced recognization
capability and electronic conductivity of CD-GS, the proposed sandwich-type
immunosensor exhibited an attractive sensing property with a detection limit down
to 0.03 pg mL
À1 . Different from the traditional electroanalysis device, lightweight
paper-based equipment has drawn tremendous attention in recent years, because of
its extraordinary merits, such as low cost, simple operation, convenient surface
functionalization, and easy large-scale production [43–45]. In this arrangement,
Ge’s group developed an enzyme-free microfluidic paper-based analytical device
(μPAD) for the determination of two tumor markers, carcinoembryonic antigen
(CEA) and prostate-specific antigen (PSA) (Fig. 5) [46]. In order to improve the
defect of poor longitudinal conduction of paper chips, a porous structure of gold
nanoparticle (AuNP)-modified paper working electrode (Au-PWE) with all-round
9 Preparation of Biosensor Based on Supermolecular Recognization
237
amounts of amine-terminated β-CD by the chemical absorption interaction. With the
unique structure of two ferrocene units, the as-synthesized N,N-bis(ferrocenoyl)
diaminoethane (Fc-Fc) as a bridge could bind two β-CD molecules via the hostguest recognization and form the supermolecular net structure of Fc-Fc/β-CD/
PAMAM-Au signal probe. Finally, secondary antibody (Ab 2 ) was attached to the
netlike probe for the generation of Fc-Fc/β-CD/PAMAM-Au-labeled Ab 2
bioconjugates. The electrochemical immunosensing platform was prepared by the
stepwise modification of electrochemically deposited Au nanoflower (DpAu), primary antibody (Ab 1 ), and bovine serum albumin (BSA) on the surface of glassy
carbon electrode (GCE). After PCT was introduced to the sensing system,
Fc-Fc/β-CD/PAMAM-Au-labeled Ab 2 bioconjugates could be captured by the sandwich conformation-dependent immunoreaction, and then a “signal-on” differential
pulse voltammetry (DPV) oxidation peak of ascorbic acid (AA) was obtained by the
enzyme-free dual amplification strategy, which was composed of the synergetic
catalytic activity of PAMAM-Au and Fc-Fc (Fig. 4b). Under the optimal experimental conditions, the electrochemical immunosensor toward the detection of PCT
exhibited a wide linear range of 1.8 pg mL
–1
–500 ng mL
À1 with a low detection limit
of 0.36 pg mL
À1 . Bimetallic alloy nanoparticle often exhibits enhanced selectivity
and catalytic activity in comparison to their single-metallic components, and both
magnetic and optical characteristics can be fine-regulated via changing the metal
ratios in alloy systems [40, 41]. Based on this, Du et al. firstly selected a facile
microwave-assisted approach to synthesize N-doped graphene nanoribbons
(N-GNRs) from N-doped multi-walled carbon nanotubes (N-MWCNTs), and PdNi
alloy nanoparticles with an average size of 10 nm were reduced in situ on the surface
of N-GNRs to produce PdNi/N-GNRs nanocomposites in the presence of ethylene
glycol and glutamate [42]. The electrochemical immunosensing biosensor was
constructed through the sequential assembly of β-CD-functionalized graphene sheets
(CD-GS), adamantine-1-carboxylic acid-functionalized Ab 1 (ADA-Ab 1 ), and BSA
on GCE surface, and subsequent addition of alpha fetoprotein (AFP) resulted in the
catch of PdNi/N-GNRs-immobilized Ab 2 (PdNi/N-GNRs-Ab 2 ) to generate a distinct
amperometric response via the catalysis of the reduction of H 2 O 2 . Taking advantages
of the high electrocatalytic activity of PdNi/N-GNRs and enhanced recognization
capability and electronic conductivity of CD-GS, the proposed sandwich-type
immunosensor exhibited an attractive sensing property with a detection limit down
to 0.03 pg mL
À1 . Different from the traditional electroanalysis device, lightweight
paper-based equipment has drawn tremendous attention in recent years, because of
its extraordinary merits, such as low cost, simple operation, convenient surface
functionalization, and easy large-scale production [43–45]. In this arrangement,
Ge’s group developed an enzyme-free microfluidic paper-based analytical device
(μPAD) for the determination of two tumor markers, carcinoembryonic antigen
(CEA) and prostate-specific antigen (PSA) (Fig. 5) [46]. In order to improve the
defect of poor longitudinal conduction of paper chips, a porous structure of gold
nanoparticle (AuNP)-modified paper working electrode (Au-PWE) with all-round
9 Preparation of Biosensor Based on Supermolecular Recognization
237