10 research outputs found
Supramolecular fibrillation of peptide amphiphiles induces environmental responses in aqueous droplets
One-dimensional (1D) supramolecular polymers are commonly found in natural and synthetic systems to prompt functional responses that capitalise on hierarchical molecular ordering. Despite amphiphilic self-assembly being significantly studied in the context of aqueous encapsulation and autopoiesis, very little is currently known about the physico-chemical consequences and functional role of 1D supramolecular polymerisation confined in aqueous compartments. Here, we describe the different phenomena that resulted from the chemically triggered supramolecular fibrillation of synthetic peptide amphiphiles inside water microdroplets. The confined connection of suitable dormant precursors triggered a physically autocatalysed chemical reaction that resulted in functional environmental responses such as molecular uptake, fusion and chemical exchange. These results demonstrate the potential of minimalistic 1D supramolecular polymerisation to modulate the behaviour of individual aqueous entities with their environment and within communitiesS
Peptide-Based Low Molecular Weight Photosensitive Supramolecular Gelators
Over the last couple of decades, stimuli-responsive supramolecular gels comprising synthetic short peptides as building blocks have been explored for various biological and material applications. Though a wide range of stimuli has been tested depending on the structure of the peptides, light as a stimulus has attracted extensive attention due to its non-invasive, non-contaminant, and remotely controllable nature, precise spatial and temporal resolution, and wavelength tunability. The integration of molecular photo-switch and low-molecular-weight synthetic peptides may thus provide access to supramolecular self-assembled systems, notably supramolecular gels, which may be used to create dynamic, light-responsive âsmartâ materials with a variety of structures and functions. This short review summarizes the recent advancement in the area of light-sensitive peptide gelation. At first, a glimpse of commonly used molecular photo-switches is given, followed by a detailed description of their incorporation into peptide sequences to design light-responsive peptide gels and the mechanism of their action. Finally, the challenges and future perspectives for developing next-generation photo-responsive gels and materials are outlined
Physicochemical Analysis of Mixed Micelles of a Viologen Surfactant: Extended to Water-in-Oil (w/o) Microemulsion and Cucurbit[8]uril-Assisted Vesicle Formation
A systematic study of the self-assembly
process of a viologen-containing
surfactant in aqueous medium is reported. Dodecyl-ethyl-viologendibromide
(DDEV) is mixed in different proportions with dodecyltrimethylammonium
bromide (DTAB), and the physicochemical properties of micellization
are evaluated in order to find a suitable combination which does not
interfere with the micellar properties of DTAB but introduces the
characteristic properties of viologen. In this process, 1% doping
of DDEV with DTAB was found to be the most appropriate, as negligible
changes were observed in the physicochemical behavior of this system
with respect to that of pure DTAB. The 1% DDEV-doped DTAB mixed micellar
system showed the characteristic two-step reduction process for the
viologen units at the interface as revealed by CV experiments. 1%
mixing of DDEV with DTAB also allowed us to prepare stable w/o microemulsions
containing viologen units at the interface which is otherwise unattainable
with pure viologen surfactants. The charge-transfer capability of
the viologen unit to the electron-rich 2,6-dihydroxynaphthalene (DHN)
moiety inside the macrocyclic host, cucurbit[8]Âuril (CB[8]) is also
evaluated for this system, and surprisingly even at this very low
concentration, the ternary complex of DDEV-DHN@CB[8] transformed the
micellar assembly to uniform vesicles. All of these properties have
been further extended to other tetraalkylammonium surfactants, and
similar effects were observed
Self-Assembly of Peptide-Amphiphile Forming Helical Nanofibers and in Situ Template Synthesis of Uniform Mesoporous Single Wall Silica Nanotubes
A lysine based peptide amphiphile
(PA) is designed and synthesized
for efficient water immobilization. The PA with a minimum gelation
concentration (MGC) of 1% w/v in water shows prolonged stability and
can also efficiently immobilize aqueous mixtures of some other organic
solvents. The presence of a free amine induced pH dependency of the
gelation as the PA could form hydrogel at a pH range of 1â8
but failed to do so above that pH. Various spectroscopic and microscopic
experiments such as steady state fluorescence, NMR, IR, CD, and FESEM
reveal the presence of hydrophobic interaction, hydrogen bond, and
ÏâÏ stacking interaction in the self-assembly process.
The self-aggregation has been correlated with the design of the molecule
to show the involvement of supramolecular forces and the hierarchical
pathway. While the L analogue formed left-handed helical nanofibers,
the other enantiomer showed opposite helicity. Interestingly the equimolar
mixture of the isomers failed to form any fibrous aggregate. Although
fibers formed at a subgel concentration, no helical nature was observed
at this stage. The length and thickness of the fibers increased with
increase in the gelator concentration. The nanofibers formed by the
gelator are used as a template to prepare mesoporous single wall silica
nanotubes (SWSNTs) in situ in plain water without the requirement
of any organic solvent as well as any external hydrolyzing agent.
The SWSNTs formed are open at both ends, are few micrometers in length,
and have an average diameter of âŒ10 nm. The BET isotherm showed
a type IV hysteresis loop suggesting mesoporous nature of the nanotubes
Dual Self-Sorting by Cucurbit[8]uril To Transform a Mixed Micelle to Vesicle
A systematic
study on the cucurbit[8]Âuril (CB[8]) assisted transformation
of a mixed micellar system of CTAB and a viologen surfactant to vesicles
is depicted. The micelle to vesicle transformation is assisted by
a charge transfer complex mediated ternary complexation between the
viologen group of the surfactant, CB[8], and 2,6-dihydroxynaphthalene.
In the presence of CB[8], both the surfactants formed U-shaped binary
inclusion complexes inside the CB[8] cavity, and no selective binding
is observed. Upon addition of DHN, CB[8] showed two different self-sorting
mechanisms. The U-shaped binary complex with CTAB breaks down, and
CB[8] moves toward the viologen headgroup of the other surfactant
to form a stable ternary complex. In the case of the viologen surfactant,
CB[8] moved toward the headgroup leaving the hydrophobic tail free
in order to form the ternary complex. The mechanistic detail of this
micelle to vesicle transformation is revealed through methodical studies
using <sup>1</sup>H and DOSY NMR, ESI-MS, ITC, and other instrumental
techniques
Hydrogelation of a Naphthalene Diimide Appended Peptide Amphiphile and Its Application in Cell Imaging and Intracellular pH Sensing
This
study reports the self-assembly and application of a naphthalene
diimide (NDI)-appended peptide amphiphile (PA). H-bonding among the
peptide moiety in conjunction with Ï-stacking between NDI and
hydrophobic interactions within the alkyl chain are the major driving
forces behind the stepwise aggregation of the PA to form hydrogels.
The PA produced efficient self-assemblies in water, forming a nanofibrous
network that further formed a self-supportive hydrogel. The molecule
followed a three-step self-assembly mechanism. At a lower concentration
(50 ÎŒM), it forms extremely small aggregates with a very low
population of the molecules. With an increase in concentration, spherical
aggregates are formed above 450 ÎŒM concentration. Importantly,
this water-soluble conjugate was found to be nontoxic, cell permeable,
and usable for cell imaging. Moreover, the aggregation process and
consequently the emission behavior are highly responsive to the pH
of the medium. Thus, the pH responsive aggregation and emission behavior
has an extended biological application for assessing intracellular
pH. The biocompatibility and intracellular pH determining capability
suggest it is a promising candidate for use as a supramolecular material
in biomedical applications