Topics in Current Chemistry (2020) 378:12
1 3
polymers, thiolated and non thiolated biomolecules) were tested, showing that cell
uptake is influenced by the effect of the exchangeable ligand and thus the NPs can
aggregate within the lipid bilayers. These results represent a step forward in our
understanding of the cellular uptake and cell integrity once NPs are incorporated
into the cell [100]. For biological applications, it is crucial to know the composition of the surface precisely. Locardi et al. [101] prepared 1-dodecanethiol-coated
AuNPs for a posterior ligand exchange using 11-mercaptoundecanoic acid. The
latter authors achieved partial substitution of the hydrophobic coating for a more
hydrophilic one, thus improving the water stability of the NPs for further biological
applications. The layer composition of the NPs obtained by these researchers was
determined by differential thermal analysis/thermogravimetry (DTA/TGA) coupled
with gas chromatography and mass spectrometry (GC–MS) [101].
AgNPs coated with polyvinylpyrrolidone (PVP) were prepared by Sang Cho and
co-workers [102]. Afterward, the capping agent was replaced using propanethiol.
These authors obtained NPs with very low aggregation tendency and high thermal
stability. The final purpose was to incorporate more stable AgNPs inside perovskites
for solar cell applications [102]. The effect of ligand exchange on the crystallite size
of AgNPs coated with oleic acid was further evaluated by Okada [103]. In this latter
work, three ligands were tested: tri-n-octyl phosphine oxide (TOPO), octanoic acid
(OA), and 1-dodecanethiol (DDT). The highest increase in crystallite size of AgNPs
was observed for TOPO as the exchangeable ligand [103].
Likewise, to modify the surface, IONP ligand exchange may also be carried out.
A new and precise synthetic route to obtain magnetite NPs (Fe 3 O 4 NPs) functionalized with polymeric ligands through ligand exchange has been reported recently
[104]; this produced NPs with different surface charges, allowing evaluating their
interaction with cells.
5 Conjugation of Biomolecules to NPs: the Main Key to Further
Applications
The application of NPs requires the stabilization of colloidal systems in a polar
medium, especially water, and the subsequent conjugation of biomolecules. Several
biomolecules, such as proteins [105], polypeptides [106] and antibodies [107] have
been conjugated to the surface of nanomaterials.
Conjugation allows to combine the biological functionality of the biomolecule
with the chemical and mechanical stability of the support, it guarantees the increase
in operational stability, facilitates the separation and purification of biomolecules
and increases their reusability [108, 109]. However, conjugation also causes alteration of the conformation of the biomolecule, which may cause the loss of biological activity and the presence of fractions of immobilized macromolecules with a
different number of junctions to the support [110, 111]. In the case of immobilized
enzymes, despite the fact that conjugation methodologies are expensive, the possibility of recovering biocatalysts from the reaction medium and the development of
continuous operations reduce the overall costs of the process [112].
104
Reprinted from the journal
1 3
polymers, thiolated and non thiolated biomolecules) were tested, showing that cell
uptake is influenced by the effect of the exchangeable ligand and thus the NPs can
aggregate within the lipid bilayers. These results represent a step forward in our
understanding of the cellular uptake and cell integrity once NPs are incorporated
into the cell [100]. For biological applications, it is crucial to know the composition of the surface precisely. Locardi et al. [101] prepared 1-dodecanethiol-coated
AuNPs for a posterior ligand exchange using 11-mercaptoundecanoic acid. The
latter authors achieved partial substitution of the hydrophobic coating for a more
hydrophilic one, thus improving the water stability of the NPs for further biological
applications. The layer composition of the NPs obtained by these researchers was
determined by differential thermal analysis/thermogravimetry (DTA/TGA) coupled
with gas chromatography and mass spectrometry (GC–MS) [101].
AgNPs coated with polyvinylpyrrolidone (PVP) were prepared by Sang Cho and
co-workers [102]. Afterward, the capping agent was replaced using propanethiol.
These authors obtained NPs with very low aggregation tendency and high thermal
stability. The final purpose was to incorporate more stable AgNPs inside perovskites
for solar cell applications [102]. The effect of ligand exchange on the crystallite size
of AgNPs coated with oleic acid was further evaluated by Okada [103]. In this latter
work, three ligands were tested: tri-n-octyl phosphine oxide (TOPO), octanoic acid
(OA), and 1-dodecanethiol (DDT). The highest increase in crystallite size of AgNPs
was observed for TOPO as the exchangeable ligand [103].
Likewise, to modify the surface, IONP ligand exchange may also be carried out.
A new and precise synthetic route to obtain magnetite NPs (Fe 3 O 4 NPs) functionalized with polymeric ligands through ligand exchange has been reported recently
[104]; this produced NPs with different surface charges, allowing evaluating their
interaction with cells.
5 Conjugation of Biomolecules to NPs: the Main Key to Further
Applications
The application of NPs requires the stabilization of colloidal systems in a polar
medium, especially water, and the subsequent conjugation of biomolecules. Several
biomolecules, such as proteins [105], polypeptides [106] and antibodies [107] have
been conjugated to the surface of nanomaterials.
Conjugation allows to combine the biological functionality of the biomolecule
with the chemical and mechanical stability of the support, it guarantees the increase
in operational stability, facilitates the separation and purification of biomolecules
and increases their reusability [108, 109]. However, conjugation also causes alteration of the conformation of the biomolecule, which may cause the loss of biological activity and the presence of fractions of immobilized macromolecules with a
different number of junctions to the support [110, 111]. In the case of immobilized
enzymes, despite the fact that conjugation methodologies are expensive, the possibility of recovering biocatalysts from the reaction medium and the development of
continuous operations reduce the overall costs of the process [112].
104
Reprinted from the journal