Motoki Ueda

Transformation of peptide nanotubes into a vesicle via fusion driven by stereo-complex formation.

Two types of peptide nanotubes, one is prepared from an amphiphilic peptide having a right-handed helix segment and the other from that having a left-handed helix segment, are shown to transform the morphology into a vesicle by membrane fusion due to stereo-complex formation between these helical segments.

Suppressive immune response of poly-(sarcosine) chains in peptide-nanosheets in contrast to polymeric micelles†

Nanoparticles are expected to be applicable for the theranostics as a carrier of the diagnostic and therapeutic agents. Lactosome is a polymeric micelle composed of amphiphilic polydepsipeptide, poly(sarcosine)64‐block‐poly(l‐lactic acid)30, which was found to accumulate in solid tumors through the enhanced permeability and retention effect. However, lactosome was captured by liver on the second administration to a mouse. This phenomenon is called as the accelerated blood clearance phenomenon. On the other hand, peptide‐nanosheet composed of amphiphilic polypeptide, poly(sarcosine)60‐block‐(l‐Leu‐Aib)6, where the poly(l‐lactic acid) block in lactosome was replaced with the (l‐Leu‐Aib)6 block, abolished the accelerated blood clearance phenomenon. The ELISA and in vivo near‐infrared fluorescence imaging revealed that peptide‐nanosheets did not activate the immune system despite the same hydrophilic block being used. The high surface density of poly(sarcosine) chains on the peptide‐nanosheet may be one of the causes of the suppressive immune response. Copyright

Rational design of peptide nanotubes for varying diameters and lengths.

Amphiphilic helical peptides (Sar)m‐b‐(L‐Leu‐Aib)n (m = 22–25; n = 7, 8, 10) with a hydrophobic block as a right‐handed helix were synthesized and their mixtures with (Sar)25‐b‐(D‐Leu‐Aib)6 containing the hydrophobic block as a left‐handed helix were examined in their molecular assembly formation. The single component (Sar)25‐b‐(D‐Leu‐Aib)6 forms peptide nanotubes of 70 nm diameter and 200 nm length. The two‐component mixtures of (Sar)25‐b‐(D‐Leu‐Aib)6 with (Sar)24‐b‐(L‐Leu‐Aib)7, (Sar)22‐b‐(L‐Leu‐Aib)8, and (Sar)25‐b‐(L‐Leu‐Aib)10 yield peptide nanotubes of varying dimensions with 200 nm diameter and 400 nm length, 70 nm diameter and several micrometer length (maximum 30 µm), and 70 nm diameter and 100–600 nm length, respectively. The right‐handed and the left‐handed helix were thus found to be molecularly mixed due to the stereo‐complex formation and to generate nanotubes of different sizes. When the mismatch of the hydrophobic helical length between the two components was of four residues, the longest nanotube was generated. Correspondingly, the hydrophobic helical segments have to interdigitate with an anti‐parallel orientation at the hydrophobic core region of the nanotube. Copyright

Morphology Control between Twisted Ribbon, Helical Ribbon, and Nanotube Self-Assemblies with His-Containing Helical Peptides in Response to pH Change

pH-Responsive molecular assemblies with a variation in morphology ranging from a twisted ribbon, a helical ribbon, to a nanotube were prepared from a novel A3B-type amphiphilic peptide having three hydrophilic poly(sarcosine) (A block) chains, a hydrophobic helical dodecapeptide (B block), and two histidine (His) residues between the A3 and B blocks. The A3B-type peptide adopted morphologies of the twisted ribbon at pH 3.0, the helical ribbon at pH 5.0, and the nanotube at pH 7.4, depending upon the protonation states of the two His residues. On the other hand, another A3B-type peptide having one His residue between the A3 and B blocks showed a morphology change only between the helical ribbon and the relatively planar sheets with pH variation in this range. The morphology change is thus induced by one- or two-charge generation at the linking site of the hydrophilic and hydrophobic blocks of the component amphiphiles but in different ways.

Tubulation on peptide vesicles by phase-separation of a binary mixture of amphiphilic right-handed and left-handed helical peptides

A binary mixture of amphiphilic polypeptides with right- and left-handed helical blocks was self-assembled into a morphology of a nano round-bottom flask shape upon heat treatment. The tubulation occurred as a result of phase-separation into the tubule domain of the single component and the vesicle domain of the stereo-complex.

Factors Influencing in Vivo Disposition of Polymeric Micelles on Multiple Administrations

Lactosome is a polymeric micelle composed of amphiphilic polydepsipeptide, poly(sarcosine)64-block-poly(l-lactic acid)30 (AB-type), which accumulates in solid tumors through the enhanced permeability and retention (EPR) effect. However, lactosome on multiple administrations changed its pharmacokinetics from accumulation in tumors to liver due to the production of antilactosome IgM, which was triggered by the first administration. This phenomenon is called the accelerated blood clearance (ABC). In order to reduce the production of antilactosome IgM, a novel nanoparticle composed of (poly(sarcosine)23)3-block-poly(l-lactic acid)30 (A3B-type) was prepared. The A3B-type lactosome at the second administration showed an in vivo disposition similar to that at the first administration due to suppression of antibody production. This study involving the AB- and A3B-type lactosomes, with variation of conditions, revealed that the high local density of poly(sarcosine) chains of the A3B-type lactosome should relate to the prevention of a polymeric micelle from interacting B-cell receptors.

Temperature-triggered fusion of vesicles composed of right-handed and left-handed amphiphilic helical peptides.

Vesicles prepared from a mixture of (Sar)(25)-b-(L-Leu-Aib)(6) (SLL) and (Sar)(25)-b-(D-Leu-Aib)(6) (SDL) fused with themselves upon heating to 90 °C. The vesicles also fused with (Sar)(28)-b-(L-Leu-Aib)(8) vesicles upon heating to 90 °C. The temperature-triggered fusion was due to the phase transition of the mixed membrane of SLL and SDL at 90 °C and should be driven by the bending energy stored in the stereocomplex membrane upon taking a vesicular structure.

Facile and precise formation of unsymmetric vesicles using the helix dipole, stereocomplex, and steric effects of peptides.

Unsymmetrical vesicular membranes were prepared from a binary mixture of the A3B-type and the AB-type host polypeptides, which were composed of the hydrophilic block (A) and the hydrophobic helical block (B) but with a different helix sense between the two host polypeptides. TEM and DLS revealed the formation of vesicles with ca. 100 nm diameter. The molecular assembly was driven by hydrophobic interaction, stereocomplex formation, and dipole-dipole interaction between hydrophobic helices. Furthermore, the A3B-type host polypeptide extended the hydrophilic block to the outer surface of vesicles as a result of the steric effect, resulting in the formation of unsymmetrical vesicular membranes. As a result, a functionalized AB-type guest polypeptide having the same helix sense with the A3B-type host polypeptide exposed the hydrophilic block to the outer surface. In contrast, an AB-type guest polypeptide having the same helix sense with the AB-type host polypeptide oriented the hydrophilic block to the inner surface. Functionalization of either the outer or inner surface of the binary vesicle is therefore facile to achieve when using either the right- or the left-handed helix of the functionalized guest polypeptide.

Molecular assembly composed of a dendrimer template and block polypeptides through stereocomplex formation.

A 2nd generation polyamideamine (PAMAM) dendrimer bearing right-handed helices to its eight terminals was shown to accommodate eight left-handed helices via stereocomplex formation to generate molecular assemblies of disk structure with 13-14 nm diameter and 6 nm thickness.

Self-assemblies of triskelion A2B-type amphiphilic polypeptide showing pH-responsive morphology transformation.

A pH-responsive rolled-sheet morphology was prepared from a triskelion A(2)B-type amphiphilic polypeptide having a histidine residue as a pH-responsive unit. The dimensions of the rolled sheet were 85 nm diameter and 210 nm length with a sheet turn number of 2.0 at pH 7.4. Upon decreasing the pH from 7.4 to 5.0, the layer spacing of the rolled sheets was widened from ca. 9 to ca. 19 nm due to electrostatic repulsion caused by histidine protonation. This morphology change occurred reversibly with a pH change between 7.4 and 5.0. The molecular packing in the rolled sheets was shown to be loosened at pH 5.0 on the basis of electron diffraction measurements. The tightness of the rolled sheets was thus controlled reversibly by a pH change due to a single protonation in the amphiphilic polypeptide.