13 research outputs found
Complex Consisting of Ī²āGlucan and Antigenic Peptides with Cleavage Site for Glutathione and Aminopeptidases Induces Potent Cytotoxic T Lymphocytes
The
efficient induction of antigen-specific immune responses requires
not only promotion of the uptake of antigens and adjuvant molecules
into antigen-presenting cells but also control of their intracellular
behavior. We previously demonstrated that the Ī²-glucan schizophyllan
(SPG) can form complexes with CpG oligonucleotides with attached dA<sub>40</sub> (CpG-dA/SPG), which can accumulate in macrophages in the
draining inguinal lymph nodes and induce strong immune responses.
In this study, we prepared various conjugates composed of antigenic
peptide (OVA<sub>257ā264</sub>) and dA<sub>40</sub> and made
complexes with SPG. The conjugates with a disulfide bond between OVA<sub>257ā264</sub> and dA<sub>40</sub> were easily cleaved by glutathione.
The resultant peptides with a hydrophobic amino acid at the C-terminal
end was recognized by puromycin-insensitive leucine aminopeptidase
(PILS-AP), which trims antigenic peptide precursors and prepares peptides
of eight or nine amino acids in length, which is the optimal length
for binding to major histocompatibility complex (MHC)-I. The conjugate
exposed to such enzymes induced a high antigen presentation level.
The antigen presentation level was almost the same before and after
the complexation with SPG. Immunization with a mixture of dAāOVA<sub>257ā264</sub>/SPG and CpGādA/SPG induced high antigen-specific
cytotoxic T-lymphocyte activity at a much lower peptide dose than
in previous studies. These results can be strongly ascribed to not
only the cell-specific delivery by SPG but also the control of the
intracellular behavior by the introduction of cleavage sites. Therefore,
peptideādA/SPG complexes could be used as potent vaccine antigens
for the treatment of cancers and infectious diseases
Glutamic Acids Bearing Calix[4]arene Micelles: pH-Controllable Aggregation Number Corresponding to Regular Polyhedra
We
have prepared a new calix[4]Āarene-based lipid containing glutamic
acid as the hydrophilic group. The Ī±-amine and the Ī³-carboxylic
acid groups of the glutamic acid moiety allowed a continuous change
in the state of the headgroup from cationic to zwitterionic and then
to anionic with increasing pH. Accompanying this headgroup change,
micelles of the lipid underwent a morphological transformation from
spherical to cylindrical and again to spherical. The morphological
transition was ascribed to the change in the lipid conformation corresponding
to the pH conditions. Interestingly, at acidic and basic pH, the spherical
micelles demonstrated monodispersity in terms of the aggregation number,
which agreed with the vertex numbers of Platonic solids, indicating
the formation of Platonic micelles. At acidic and basic pH, the lipid
conformations were almost identical, but there was a slight difference
in the hydrophilic volume, which might affect the packing behavior
of the lipid in micelles and account for the difference in the aggregation
number. This study clearly demonstrates the precise pH-controllable
aggregation number of micelles, which belong to the Platonic micelle
systems
Supramolecular Chirality: Vesicle-to-Chiral Helix Transition of the Micelles Consisting of a Sugar-Bearing Calix[4]arene Surfactant
Supramolecular
self-assembly and the resulting chiral transfer
from the molecular level to the nanoscale is a major topic in modern
supramolecular chemistry. We synthesized a galactose-bearing calix[4]Āarene
surfactant (chiral) and mixed it with a primary amine-bearing analogue
(achiral). The mixture showed strong induced circular dichroism (ICD)
at an almost 3:2 molar ratio of the two surfactants, and exothermic
heat was observed upon mixing. The magnitude of Ī<i>H</i> was comparable to that of van der Waals interactions. This phenomenon
indicated that the ICD can be ascribed to the formation of a new supramolecular
assembly in which the stoichiometric interaction between the two molecules
leads to complexation and the resultant complex has chiral morphology.
Transmission electron microscopy and small-angle X-ray scattering
showed that the galactose-bearing surfactant forms vesicles, and the
mixing induces a transition from the vesicles to threadlike cylinders
with a diameter of ā¼3.0 nm. We presume that these cylinder
are twisted because of chiral transfer from the chiral galactose moiety
and show ICD
Rediscovering the Monodispersity of Sulfonatocalix[4]arene-Based Micelles
When
the micellar aggregation number (<i>N</i><sub>agg</sub>)
is small enough (<30), the <i>N</i><sub>agg</sub> matches
the value of vertexes of a regular polyhedron: Platonic solids, and
demonstrates perfect monodispersity. These micelles are named Platonic
micelles and are particularly found in the system of calix[4]Āarene-based
micelles due to the rigid structure of the backbone molecule. Although
sulfonatocalix[4]Āarene-based micelles are among the most studied host
molecules in supramolecular chemistry, their micellar properties as
Platonic micelles have thus far been overlooked. In this study, we
prepared various sulfonatocalix[4]Āarene-based amphiphiles bearing
alkyl chains with different lengths and investigated their aggregation
behavior. When the amphiphiles formed spherical micelles, they demonstrated
monodispersity in terms of <i>N</i><sub>agg</sub>, whose
value changed from 4 to 17, and then to 24, upon increasing the carbon
number in each alkyl chain from C5 to C6, and then to C7, respectively.
Although the numbers 17 and 24 do not match the vertices of regular
polyhedra, these values can be reasonably explained by the Thomson
problem, which considers the Coulomb potential for calculating the
best packing on a sphere with multiple identical spherical caps. This
study describes rediscovery of the monodispersity of sulfonatocalix[4]Āarene-based
micelles, which is consistent with the idea of Platonic micelles
A Stimulus-Responsive Shape-Persistent Micelle Bearing a Calix[4]arene Building Block: Reversible pH-Dependent Transition between Spherical and Cylindrical Forms
A series of cationic calix[4]Āarene-based lipids with
alkyl chains
of varying length were newly synthesized, and the ones with propyl
and hexyl tails, denoted by CaL[4]ĀC3 and C6, respectively, were found
to form spherical micelles at low pH (protonated state of the amine
headgroup). Upon deprotonation with increasing pH, CaL[4]ĀC3 showed
a sphere-to-cylinder transition, while CaL[4]ĀC6 changed from sphere,
to cylinder, to monolayer vesicle. Synchrotron small-angle X-ray scattering
(SAXS) patterns from both spherical and cylindrical CaL[4]ĀC3 micelles
exhibited a sharp intensity minimum, indicating shape monodispersity.
The monodispersity of the CaL[4]ĀC3 spherical micelles was further
confirmed by analytical ultracentrifugation (AUC). SAXS, AUC, and
static light scattering agreeingly indicated an aggregation number
of 6. In contrast, CaL[4]ĀC6 exhibited polydispersity with an average
aggregation number of 12. When the number of carbons of the alkyl
chain was increased to 9 (CaL[4]ĀC9), cylinder formed at low pH, while
at high pH, no clear morphology could be observed. The present results
indicate that a very precise combination of tail length, head volume,
and rigidity of the building block is required to produce shape-persistent
micelles and that the shape-persistence can be maintained upon a structural
transition. An attempt to reconstruct a molecular model for the spherical
CaL[4]ĀC3 micelle was made with an ab initio shape determining program
Adjuvant Activity Enhanced by Cross-Linked CpG-Oligonucleotides in Ī²āGlucan Nanogel and Its Antitumor Effect
Cancer vaccine has the ability to
directly eradicate tumor cells
by creating and activating cytotoxic T lymphocytes (CTLs). To achieve
efficient CTL activity and to induce Th1 responses, it is essential
to administer an appropriate adjuvant as well as an antigen. CpG-ODN
is known as a ligand of Toll-like receptor 9 (TLR9) and strongly induces
Th1 responses. In our previous study, we developed a CpG-ODN delivery
system by use of the formation of complexes between ODN and a Ī²-glucan
SPG, denoted as CpG/SPG, and demonstrated that CpG/SPG induces high
Th1 responses. In this study, we created a nanogel made from CpG/SPG
complexes through DNAāDNA hybridization (cross-linked (CL)-CpG).
Immunization with CL-CpG induced much stronger antigen-specific Th1
responses in combination with the antigenic protein ovalbumin (OVA)
than that with CpG/SPG. Mice preimmunized with CL-CpG and OVA exhibited
a long delay in tumor growth and an improved survival rate after tumor
inoculation. These immune inductions can be attributed to the improvement
of cellular uptake by the combination of increased size and the cluster
effect of the Ī²-glucan recognition site in the nanogel structure.
In other words, the particle nature of CL-CpG, instead of the semiflexible
rod conformation of CpG/SPG, enhanced the efficacy of a cancer vaccine.
The present results indicate that CL-CpG can be used as a potent vaccine
adjuvant for the treatment of cancers and infectious diseases
Self-Assembly of Calix[4]arene-Based Amphiphiles Bearing Polyethylene Glycols: Another Example of āPlatonic Micellesā
The
aggregation number of classical micelles exhibits a certain
distribution, which is a recognizable feature of conventional micelles.
However, we recently identified perfectly monodisperse calix[4]Āarene-based
micelles whose aggregation numbers agree with the vertex numbers of
regular polyhedra, that is, Platonic solids, and thus they are named
āPlatonic micellesā. Regarding our hypothesis of the
formation mechanism of Platonic micelles, both repulsive interactions
including steric hindrance and electrostatic repulsions among the
headgroups are important for determining their aggregation number;
however, neither of these is necessarily needed to consider. In this
study, we employed polyethylene glycols (PEGs) as the nonionic headgroup
of calix[4]Āarene-based amphiphiles to study the effects of only repulsive
interactions caused by steric hindrance on the formation of Platonic
micelles. The amphiphiles containing relatively low-molecular-weight
PEGs (550 or 1000 g mol<sup>ā1</sup>) form dodecamer or octamer
micelles, respectively, with no variation in the aggregation number.
However, relatively high-molecular-weight PEGs (2000 g mol<sup>ā1</sup>) produce polydispersed micelles with a range of aggregation number.
PEG 2000 exhibits a greater affinity for water than PEG 550 and 1000,
resulting in fewer hydrophobic interactions in micelle formation,
as indicated by the drastic increase of the critical micelle concentration
(CMC) value in the PEG 2000 system. The instability of the structure
of PEG<sub>2k</sub>CaL5 micelles might contribute to the higher mobility
of PEG in the micellar shell, resulting in a non-Platonic aggregation
number with polydispersity
Ī²-1,3-d-Glucan Schizophyllan/Poly(dA) Triple-Helical Complex in Dilute Solution
A certain length of poly(deoxyadenylic acid) (dA<sub><i>X</i></sub>) can form a novel complex with Ī²-1,3-d-glucan schizophyllan (SPG) with a stoichiometric composition of one dA binding two main chain glucoses. We measured dilute solution properties for the complex with light and small-angle X-ray scattering as well as intrinsic viscosity and found that the complex behaves as a semiflexible rod without branching or cross-linking. We analyzed the data with the wormlike cylinder model, and the chain dimensions and the persistence length for the complexes were consistently determined. The chain flexibility was reduced to almost 25% upon complexation for dA/SPG and to 15% for S-dA/SPG, where S-dA denotes the phosphorothioated DNA analogue. The changes in the molar mass per unit length and the diameter indicated that the helix was elongated or stretched along the axis direction upon the complexation
CoreāShellāCorona Micelles from a Polyether-Based Triblock Terpolymer: Investigation of the pH-Dependent Micellar Structure
Coreāshell-corona
micelles featuring a pH-responsive shell
have been characterized in dilute aqueous solution at different pH
values (4ā8) by using dynamic light scattering (DLS), field-flow
fractionation coupled with multiangle light scattering detector (FFF-MALS),
steady-state fluorescence, small-angle X-ray scattering (SAXS), and
cryogenic transmission electron microscopy (cryo-TEM). The micelles
are formed by self-assembly of a polyether-based triblock terpolymer
consisting of a hydrophobic polyĀ(<i>tert</i>-butyl glycidyl
ether) block (P<i>t</i>BGE), a pH-responsive modified polyĀ(allyl
glycidyl ether) segment (PAGE<sub>COOH</sub>), and a neutral hydrophilic
polyĀ(ethylene oxide) block (PEO). Because of the side-chain carboxylic
acids in the middle block, the micellar structure and size depends
on the solution pH. Hereby, we show that an increase in pH induces
a decrease in the aggregation number (<i>N</i><sub>agg</sub>). In addition, the combination of the above measurements revealed
an unexpected morphological change from spherical to ellipsoidal micelles
by increasing pH
Ultraviolet Patterned Calixarene-Derived Supramolecular Gels and Films with Spatially Resolved Mechanical and Fluorescent Properties
Supramolecular
assemblies have in the past been considered mechanically
weak and in most cases unable to withstand their own weight. Calixarene-derived
networks can, however, provide robust supramolecular gels. Incorporating
a photoreactive stilbene moiety, we show that the aggregation state
of the material can be tuned by heating and UV exposure in order to
control the mechanical as well as the fluorescent properties. Regulating
the extent of heating to control the proportion of H-aggregates and
J-aggregates and further cross-linking of H-aggregates by control
over UV exposure allows for adjustable photopatterning of the fluorescence
as well as the material stiffness in the range from ā¼100 to
450 kPa. We expect this straightforward supramolecular system will
be suitable for advanced prototyping in applications where modulus
and shape are important design criteria