corresponding monovalent references (500 μM) in most cases. As anticipated, the
overall results suggested that additional interactions with the transferase were
observed with the incorporation of the appropriate functionalization at the 5-position
of the carbohydrate unit, considering multivalent analogues with the same spacers
(14, 17 and 19). The marked decrease in IC 50 values along this series when going
from the hexose to the octose derivative demonstrated this tendency, with the best
inhibition profile for octoside 19. The presence of shorter spacer and the introduction
of aromatic moiety in the aglycone also tended to improve the binding properties.
Although significant levels of multivalent inhibition have been measured for two
different enzymes in the presence of dodecavalent glycosylated C60 fullerenes, more
investigations have to be performed to rationalize these promising results and optimize
the combination of multivalency and glycomimetic for novel antibacterial agents.
4 Glyconanotubes
Carbon nanotubes (CNTs) represent members of the fullerene structural family and
consist exclusively of carbon atoms arranged in a series of condensed benzene rings,
organized as graphite sheets rolled-up into tubular structures [63]. According to
specific nomenclature, single-walled CNTs (SWNTs) are made up of single graphene
layer wrapped into cylindrical structures, whereas multi-walled CNTs (MWNTs) are
generated from a central tubule of nanometric diameter and surrounded by several
graphite layers spaced by a distance of about 0.34 nm. Typically, CNTs form bundles
that are entangled together in the solid state giving rise to highly complex “spaghetti”
networks [64]. Intrinsically, CNTs possess very interesting and unique physicochemical properties such as high surface area, ordered structure with high aspect ratio,
ultralight weight, excellent chemical stability, high electrical conductivity, high thermal conductivity, and metallic or semiconducting behaviors. For these reasons, these
nanomaterials have raised great enthusiasm and expectations in a wide range of
different applications including material, biological, and medical sciences when
suitable functionalizations are realized [65]. In fact, their inherent hydrophobic
properties, associated with their natural propensity to form bundles via aggregation
through van der Waals forces, constitute major technical barriers for their utilization in
medicinal applications. To overcome these drawbacks, the modification of their
surface is typically achieved by adsorption, electrostatic interaction, or covalent
attachment of various appendages to reach the specific targeted properties [66].
Through such modifications, the water solubility of CNTs is generally improved and
the aggregation phenomenon reduced. Furthermore, their biocompatibility and
biodistribution profiles are completely transformed and improved. Particularly, recent
investigations boosted the emergence of functionalized CNTs as new biologically
relevant alternatives for therapeutic and diagnostic applications [67], including their
use as vectors for delivery of therapeutic molecules [68] such as plasmid genes [69],
peptides/proteins [70], and antibiotics [71]. More interestingly in the context of this
chapter, these nanosystems recently acted as useful tridimensional platforms for
carbohydrate presentation. The resulting densely oriented sugars as pendant groups
310
N. Kottari et al.
overall results suggested that additional interactions with the transferase were
observed with the incorporation of the appropriate functionalization at the 5-position
of the carbohydrate unit, considering multivalent analogues with the same spacers
(14, 17 and 19). The marked decrease in IC 50 values along this series when going
from the hexose to the octose derivative demonstrated this tendency, with the best
inhibition profile for octoside 19. The presence of shorter spacer and the introduction
of aromatic moiety in the aglycone also tended to improve the binding properties.
Although significant levels of multivalent inhibition have been measured for two
different enzymes in the presence of dodecavalent glycosylated C60 fullerenes, more
investigations have to be performed to rationalize these promising results and optimize
the combination of multivalency and glycomimetic for novel antibacterial agents.
4 Glyconanotubes
Carbon nanotubes (CNTs) represent members of the fullerene structural family and
consist exclusively of carbon atoms arranged in a series of condensed benzene rings,
organized as graphite sheets rolled-up into tubular structures [63]. According to
specific nomenclature, single-walled CNTs (SWNTs) are made up of single graphene
layer wrapped into cylindrical structures, whereas multi-walled CNTs (MWNTs) are
generated from a central tubule of nanometric diameter and surrounded by several
graphite layers spaced by a distance of about 0.34 nm. Typically, CNTs form bundles
that are entangled together in the solid state giving rise to highly complex “spaghetti”
networks [64]. Intrinsically, CNTs possess very interesting and unique physicochemical properties such as high surface area, ordered structure with high aspect ratio,
ultralight weight, excellent chemical stability, high electrical conductivity, high thermal conductivity, and metallic or semiconducting behaviors. For these reasons, these
nanomaterials have raised great enthusiasm and expectations in a wide range of
different applications including material, biological, and medical sciences when
suitable functionalizations are realized [65]. In fact, their inherent hydrophobic
properties, associated with their natural propensity to form bundles via aggregation
through van der Waals forces, constitute major technical barriers for their utilization in
medicinal applications. To overcome these drawbacks, the modification of their
surface is typically achieved by adsorption, electrostatic interaction, or covalent
attachment of various appendages to reach the specific targeted properties [66].
Through such modifications, the water solubility of CNTs is generally improved and
the aggregation phenomenon reduced. Furthermore, their biocompatibility and
biodistribution profiles are completely transformed and improved. Particularly, recent
investigations boosted the emergence of functionalized CNTs as new biologically
relevant alternatives for therapeutic and diagnostic applications [67], including their
use as vectors for delivery of therapeutic molecules [68] such as plasmid genes [69],
peptides/proteins [70], and antibiotics [71]. More interestingly in the context of this
chapter, these nanosystems recently acted as useful tridimensional platforms for
carbohydrate presentation. The resulting densely oriented sugars as pendant groups
310
N. Kottari et al.