Topics in Current Chemistry (2020) 378:12
1 3
Hence, selection of the most appropriate strategy constitutes a crucial aspect in the
design and construction of functional nanobioconjugates [30, 31].
This contribution aims to highlight the virtues of conjugating diverse biomolecules with NPs. Herein, we focus on gold, silver and iron oxide NPs. Other nanometric systems such as quantum dots, carbon nanotubes, fullerenes, graphene, reduced
graphene oxide (RGO), Janus and core–shell NPs are outside the scope of this
review. The purpose of this contribution is to provide a pedagogic overview of the
topic, with emphasis on the progressive presentation of the contents. Accordingly,
we begin with simpler and more general concepts, such as the preparation, structural
description and physicochemical characterization of the three kinds of NPs, later
on covering the most advanced and up-to-date bioelectrochemical applications of
NP–biomolecule conjugates. Our intention was to review the most recent advances
in nanobioconjugation chemistry; consequently, 70% of the work reviewed here
comes from the last 3 years (2017–2019), 86% from the last 5 years (2015–2019)
and 93% from the last decade (2009–2019), thus assuring a current view of the most
recent developments in the field.
This review is organized into five sections in addition to this Introduction. The
following section presents the general properties of gold, silver and iron oxide NPs.
Thereafter, a section on synthetic routes summarizes the main methods used to
obtain these nanomaterials. We then discuss stabilization and surface functionalization of NPs with different functional groups, which allows their further bioconjugation to diverse biomolecules, as described in the next section, Conjugation of biomolecules to NPs: the main key to further application. Finally, Nanobioconjugates
and their electrochemical application offers a review of the most recent trends in the
design of electrochemical biosensors based on the conjugation of gold, silver, and
iron oxide NPs with biomolecules. The use of different electrode architectures, and
preparation protocols and biosensor performances are discussed, in order to provide
a contemporary outline of current trends in the utilization of bioconjugated nanosystems in bioelectrochemical applications.
2 General Properties of Gold, Silver and Iron Oxide NPs
2.1 Gold and Silver NPs
NPs are atomic aggregates with a diameter between 1 and 100 nm [32]. Such dimensions determine their unique properties, which differ from individual atoms and bulk
materials. These differences are explained by their high surface to volume ratio and
quantum size effects [33]. Both gold and silver NPs (herein referred to as AuNPs
and AgNPs, respectively) present unique colors that have made them attractive for
developing new analytical assays [34]. The colors of these colloids are caused by a
phenomenon known as surface plasmon resonance (SPR) [35, 36]. This is a feature
typical of many metallic NPs, including AuNPs and AgNPs. SPR consists of the
collective oscillation of conduction electrons across the NP due to the resonance that
occurs with incident radiation (Fig. 1).
96
Reprinted from the journal
1 3
Hence, selection of the most appropriate strategy constitutes a crucial aspect in the
design and construction of functional nanobioconjugates [30, 31].
This contribution aims to highlight the virtues of conjugating diverse biomolecules with NPs. Herein, we focus on gold, silver and iron oxide NPs. Other nanometric systems such as quantum dots, carbon nanotubes, fullerenes, graphene, reduced
graphene oxide (RGO), Janus and core–shell NPs are outside the scope of this
review. The purpose of this contribution is to provide a pedagogic overview of the
topic, with emphasis on the progressive presentation of the contents. Accordingly,
we begin with simpler and more general concepts, such as the preparation, structural
description and physicochemical characterization of the three kinds of NPs, later
on covering the most advanced and up-to-date bioelectrochemical applications of
NP–biomolecule conjugates. Our intention was to review the most recent advances
in nanobioconjugation chemistry; consequently, 70% of the work reviewed here
comes from the last 3 years (2017–2019), 86% from the last 5 years (2015–2019)
and 93% from the last decade (2009–2019), thus assuring a current view of the most
recent developments in the field.
This review is organized into five sections in addition to this Introduction. The
following section presents the general properties of gold, silver and iron oxide NPs.
Thereafter, a section on synthetic routes summarizes the main methods used to
obtain these nanomaterials. We then discuss stabilization and surface functionalization of NPs with different functional groups, which allows their further bioconjugation to diverse biomolecules, as described in the next section, Conjugation of biomolecules to NPs: the main key to further application. Finally, Nanobioconjugates
and their electrochemical application offers a review of the most recent trends in the
design of electrochemical biosensors based on the conjugation of gold, silver, and
iron oxide NPs with biomolecules. The use of different electrode architectures, and
preparation protocols and biosensor performances are discussed, in order to provide
a contemporary outline of current trends in the utilization of bioconjugated nanosystems in bioelectrochemical applications.
2 General Properties of Gold, Silver and Iron Oxide NPs
2.1 Gold and Silver NPs
NPs are atomic aggregates with a diameter between 1 and 100 nm [32]. Such dimensions determine their unique properties, which differ from individual atoms and bulk
materials. These differences are explained by their high surface to volume ratio and
quantum size effects [33]. Both gold and silver NPs (herein referred to as AuNPs
and AgNPs, respectively) present unique colors that have made them attractive for
developing new analytical assays [34]. The colors of these colloids are caused by a
phenomenon known as surface plasmon resonance (SPR) [35, 36]. This is a feature
typical of many metallic NPs, including AuNPs and AgNPs. SPR consists of the
collective oscillation of conduction electrons across the NP due to the resonance that
occurs with incident radiation (Fig. 1).
96
Reprinted from the journal