.
Angewandte
Communications
vesicles co-assembled from glycolipids and phospholipids,[5d]
carbohydrate ligands are likely randomly distributed on the
surface of vesicles formed from the physical mixture of 51
(0.4 mmolmLÀ1)
and
(3,5)12G1-I-PhE-(3,4,5)-3EO-G1-
(OCH3)3,[6c] while the ligand distribution can be chemically
controlled by twin-mixed 55. The advantage of this type of
chemical control of ligand distribution becomes evident when
considering the highest bioactivity exhibited by the vesicles
derived from twin-mixed topology (Figure 1c) in binding
plant (Figure SF5), bacterial (Figure SF6), and human (Fig-
ure 2c) lectins.
In conclusion, three libraries containing 18 amphiphilic
Janus glycodendrimers with d-mannose, d-galactose, and d-
lactose in the hydrophilic part have been synthesized through
an accelerated modular strategy. These compounds exhibit
three different topologies (Figure 1): ten are twin-twin
carbohydrate amphiphilic Janus glycodendrimers constructed
with two identical hydrophobic dendrons and two identical
carbohydrate headgroups (Library 1), seven are single-single
carbohydrate glycodendrimers built with one hydrophobic
dendron and one carbohydrate (Library 2), and three are
twin-mixed TEG:carbohydrate glycodendrimers endowed
with two identical hydrophobic dendrons, one TEG mono-
methyl ether containing hydrophilic dendron, and one
carbohydrate (Library 3). Monodisperse and stable soft
unilamellar vesicles, denoted glycodendrimersomes, were
prepared by simple injection of THF solutions of the
glycodendrimers into water or buffer. Notably, all 18 of the
Janus compounds self-assemble into soft unilamellar multi-
valent glycodendrimersomes, a result that highlights the
extremely high reliability of the prediction strategy based
on the primary structure of the Janus glycodendrimers.[7] By
performing agglutination assays with the biomedically rele-
vant plant lectin ConA, bacterial lectin PA-IL, and human
galectin-7, specific and potent bioactivity for the glycoden-
drimersomes was demonstrated, which proves the spatial
arrangement of multivalent glycan display of glycodendri-
mersomes. With the multivalent glycan ligands extending out
of the vesicle surface, the glycodendrimersomes formed by
twin-mixed amphiphilic Janus glycodendrimers (Figure 1c)
showed the highest binding affinity for lectins and proved to
have the optimal glycan ligand display. We demonstrated that
the most efficient supramolecular glycan multivalency is
determined by a combination of numbers and topology rather
than only numbers. This novel biological membrane mimic is
expected to be of interest for targeted drug delivery,
vaccines,[11c] and various fundamental and technological
areas of nanomedicine.[13]
Figure 2. Representative cryo-TEM images of glycodendrimersomes
self-assembled by injection of THF solutions of a) 45 (0.5 mgmLÀ1) in
PBS or b) 50a (0.5 mgmLÀ1) in HEPES. c) Agglutination assay with
Lac-containing glycodendrimersomes (in mmolmLÀ1) with different
topologies in the presence of hGal-7 (0.5 mgmLÀ1) in PBS buffer.
effector.[2d,8,12] The absorbance profiles of agglutination assays
with ConA (Figure SF4,5), PA-IL (Figure SF6), and hGal-7
(Figure 2) in HEPES or PBS were recorded by UV/Vis
spectroscopy. The availability of glycodendrimersomes with
different sugar headgroups afforded rigorous specificity
controls, as illustrated by the lack of reactivity of hGal-7
with Man-presenting glycodendrimersome 53 (Figure 2c).
After adding hGal-7 to the solution of Lac-presenting
vesicles, the absorbance increased steadily until a plateau
was reached (Figure 2c). Similar results were obtained from
assays of ConA with vesicles self-assembled by d-Man-
containing dendrimers (Figure SF5) and PA-IL with vesicles
derived from d-Gal-containing dendrimers (Figure SF6).
These results support the hypothesis of maintained selectivity
and bioactivity.
In order to study the effect of the topology of these
glycodendrimers on the bioactivity of the corresponding
glycodendrimersomes, it is reasonable to keep the molar
concentration of the ligand identical in each solution. The
final concentration of twin-mixed molecule 55 and single-
single 51 was adjusted to 0.4 mmolmLÀ1 to give 0.4 mmolmLÀ1
of d-lactose. The concentration of twin-twin 45 had to be set
to 0.2 mmolmLÀ1. Interestingly, the agglutination curve of 51
at 0.4 mmolmLÀ1 overlapped with that of 45 at 0.2 mmolmLÀ1,
which may indicate that the hydrodynamic volume of single-
single glycodendrimers on the vesicle surface is half that of
their twin-twin counterparts. On the other hand, twin-mixed
55 at 0.4 mmolmLÀ1 showed the highest absorbance in the
series, which indicates that a diluted density of glycan ligand
favors the contact between the carbohydrate and protein
because it leads to reduced steric hindrance.[4d] The steric
hindrance can also be reduced in the vesicles co-assembled
with 51 (0.4 mmolmLÀ1) and the nonsugar dendrimer
(3,5)12G1-I-PhE-(3,4,5)-3EO-G1-(OCH3)3,[6c] for which the
density of sugar on the vesicle surface was diluted, thus
leading to higher binding efficiency than with self-assembly
by 51 (0.4 mmolmLÀ1). Similar to carbohydrate-containing
Received: March 10, 2014
Revised: May 2, 2014
Published online: June 12, 2014
Keywords: agglutinins · biomembrane glycans · dendrimers ·
.
lectins · vesicles
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 10899 –10903