1 3
Topics in Current Chemistry (2020) 378:12
surfaces can be switched by means of functionalized IONPs in the presence of an
external magnet [233]. In addition, the Fe 3 O 4 NPs possesses peroxidase-like activity that could catalyze the electrochemical oxidation–reduction of H 2 O 2 , similar to
HRP [234]. It is worth noting that both the oxidation reaction and the reduction of
H 2 O 2 , depending on the applied potential, can be used as a transduction reaction in
a biosensor [235].
Tian et al. [236] have designed an ultrasensitive electrochemical cytosensor to
detect MCF-7 CTCs—a tumor marker in human breast carcinoma. The electrochemical cytosensor was developed based on magnetic field-induced, targeted separation,
and enrichment, and RGO/molybdenum disulfide (RGO/MoS 2 ) composites and
Fe 3 O 4 NPs with a synergistic effect on the catalysis of H 2 O 2 . The proposed cytosensor exhibited a linear range from 15 to 45 cells mL
−1
with a lower detection limit of
6 cells mL
−1
for MCF-7 detection.
Pakapongpan and Poo-arporn [211] describe a novel strategy for obtaining an
enzyme biosensor based on direct electrochemistry. In this case, nanomaterials such
as RGO and Fe 3 O 4 NPs were used to increase the specific area of the electrode,
to create a favorable environment to immobilize the enzyme GOx and to facilitate
electron transfer between the enzyme and the surface of the electrode. Initially, the
authors obtained the RGO-Fe 3 O 4 nanocomposite by means of covalent bonding
through the coupling agent, EDC, and NHS (see Scheme 1), while for immobilization of the enzyme they used electrostatic interactions since GOx is negatively
charged at pH 7 and on the surface of the Fe 3 O 4 NPs there is a positive environment
of amino groups.
Recently, Fe 3 O 4 /graphene composites have attracted great interest in the manufacture of biosensors. Teymourian et al. [237] established a novel label-free nanocomposite, using an indicator-free strategy of electrochemical DNA sensor based
on Fe 3 O 4 NPs/RGO (Fe 3 O 4 /RGO) nanocomposite. In the functioning of the sensor, Fe 3 O 4 /RGO nanocomposite was used as a substrate to immobilize probe DNA
and hybridization with the target sequence to form dsDNA, which achieved a better
analytical signal through measuring changes in the differential pulse voltammetric
(DPV) peak current of the underlying Fe(II)/Fe(III) redox system.
Tufa et al. [238] described an electrochemical immunosensor using GQD, Fe 3 O 4 ,
and AgNPs for the detection of Mycobacterium tuberculosis. In this device, the synergic effect of three nanomaterials is used to achieve better electrochemical performance. A core–shell Fe 3 O 4 @Ag/GQDs nanotriplex was synthesised for immobilization of Ab1, and by means of the Ab2-AuNPs conjugate as the label for detection of
the culture filtrate protein (CFP-10). Fe 3 O 4 NPs were used to improve mass transport and increase the surface to volume ratio, while AgNPs enhanced electrical conductivity, helping prevent Fe 3 O 4 NPs from aggregating and helping GQD load more
of the anti-CFP-10 antibody onto the electrode. The immunosensor showed a wide
linear range (0.005–500 μg/mL) with a limit of detection (signal/noise = 3) reaching 0.33 ng/mL, resulting in a reliable and robust performance with high selectivity
toward CFP-10.
An electrochemical biosensor based on Fe 3 O 4 NPs–PVA nanocomposite for glucose detection has also been reported by Sanaeifar et al. [207]. The polyvinyl alcohol-Fe 3 O 4 nanocomposite acted as a modifier of the surface of an Sn electrode and
117
Reprinted from the journal
Topics in Current Chemistry (2020) 378:12
surfaces can be switched by means of functionalized IONPs in the presence of an
external magnet [233]. In addition, the Fe 3 O 4 NPs possesses peroxidase-like activity that could catalyze the electrochemical oxidation–reduction of H 2 O 2 , similar to
HRP [234]. It is worth noting that both the oxidation reaction and the reduction of
H 2 O 2 , depending on the applied potential, can be used as a transduction reaction in
a biosensor [235].
Tian et al. [236] have designed an ultrasensitive electrochemical cytosensor to
detect MCF-7 CTCs—a tumor marker in human breast carcinoma. The electrochemical cytosensor was developed based on magnetic field-induced, targeted separation,
and enrichment, and RGO/molybdenum disulfide (RGO/MoS 2 ) composites and
Fe 3 O 4 NPs with a synergistic effect on the catalysis of H 2 O 2 . The proposed cytosensor exhibited a linear range from 15 to 45 cells mL
−1
with a lower detection limit of
6 cells mL
−1
for MCF-7 detection.
Pakapongpan and Poo-arporn [211] describe a novel strategy for obtaining an
enzyme biosensor based on direct electrochemistry. In this case, nanomaterials such
as RGO and Fe 3 O 4 NPs were used to increase the specific area of the electrode,
to create a favorable environment to immobilize the enzyme GOx and to facilitate
electron transfer between the enzyme and the surface of the electrode. Initially, the
authors obtained the RGO-Fe 3 O 4 nanocomposite by means of covalent bonding
through the coupling agent, EDC, and NHS (see Scheme 1), while for immobilization of the enzyme they used electrostatic interactions since GOx is negatively
charged at pH 7 and on the surface of the Fe 3 O 4 NPs there is a positive environment
of amino groups.
Recently, Fe 3 O 4 /graphene composites have attracted great interest in the manufacture of biosensors. Teymourian et al. [237] established a novel label-free nanocomposite, using an indicator-free strategy of electrochemical DNA sensor based
on Fe 3 O 4 NPs/RGO (Fe 3 O 4 /RGO) nanocomposite. In the functioning of the sensor, Fe 3 O 4 /RGO nanocomposite was used as a substrate to immobilize probe DNA
and hybridization with the target sequence to form dsDNA, which achieved a better
analytical signal through measuring changes in the differential pulse voltammetric
(DPV) peak current of the underlying Fe(II)/Fe(III) redox system.
Tufa et al. [238] described an electrochemical immunosensor using GQD, Fe 3 O 4 ,
and AgNPs for the detection of Mycobacterium tuberculosis. In this device, the synergic effect of three nanomaterials is used to achieve better electrochemical performance. A core–shell Fe 3 O 4 @Ag/GQDs nanotriplex was synthesised for immobilization of Ab1, and by means of the Ab2-AuNPs conjugate as the label for detection of
the culture filtrate protein (CFP-10). Fe 3 O 4 NPs were used to improve mass transport and increase the surface to volume ratio, while AgNPs enhanced electrical conductivity, helping prevent Fe 3 O 4 NPs from aggregating and helping GQD load more
of the anti-CFP-10 antibody onto the electrode. The immunosensor showed a wide
linear range (0.005–500 μg/mL) with a limit of detection (signal/noise = 3) reaching 0.33 ng/mL, resulting in a reliable and robust performance with high selectivity
toward CFP-10.
An electrochemical biosensor based on Fe 3 O 4 NPs–PVA nanocomposite for glucose detection has also been reported by Sanaeifar et al. [207]. The polyvinyl alcohol-Fe 3 O 4 nanocomposite acted as a modifier of the surface of an Sn electrode and
117
Reprinted from the journal