3 research outputs found
Protein-Induced Supramolecular Disassembly of Amphiphilic Polypeptide Nanoassemblies
Mimicking
noncovalent interaction based processes in nature has been an important
goal of supramolecular chemistry. Here, we report on amphiphilic polypeptides
that self-assemble to form nanoscale supramolecular assemblies and
are programmed to disassemble in response to a specific protein. Benzenesulfonamide
and carbonic anhydrase have been chosen as the ligand and protein,
respectively, to demonstrate this possibility. Since the amphiphilic
nanoassembly sequesters hydrophobic guest molecules, the protein-specific
disassembly event provides a protein-sensitive molecular release as
well. We envision that the binding induced disassembly and guest release
might open up new opportunities for the next generation of supramolecular
assemblies for protein-specific delivery and diagnostics
Understanding the Role of H‑Bonding in Aqueous Self-Assembly of Two Naphthalene Diimide (NDI)-Conjugated Amphiphiles
Supramolecular
architectures with the synchronized combination
of various directional noncovalent forces are ubiquitous in biological
systems. However, reports of such abiotic synthetic systems involving
H-bonding in aqueous medium are rare due to the challenge faced in
the formation of such structures by overcoming the competition from
the water molecules. In this paper we have studied self-assembly of
two structurally related naphthalene-diimide (NDI) conjugated bola-amphiphiles
(NDI-1 and NDI-2) in water with an aim to realize the specific role
of H-bonding among the hydrazide units present in one of the two building
blocks (NDI-2) on the self-assembly. Both chromophores showed vesicular
assembly in aqueous solution driven primarily by π-stacking
among the NDI chromophores, which could be probed by UV–vis
absorption spectra. Contrary to common belief, the lack of an H-bonding
group in NDI-1 was found to be a boon in disguise in terms of the
stability of the aggregates. Whereas NDI-2 aggregates showed LCST
around 65–70 °C owing to the breaking of the H-bonds with
increased temperature, the NDI-1 aggregates were found to be structurally
intact until 90 °C, which may be attributed to the increased
hydrophobicity introduced by the absence of the polar hydrazide group.
Further concentration- and solvent-dependent UV–vis studies
showed that NDI-1 formed assembled structure at greatly dilute solution
and also in a solvent such as THF, confirming greater propensity for
its self-assembly. As both bola-amphiphiles contain an electron-deficient
NDI chromophore, interaction of their vesicles was studied with an
externally added electron-rich pyrene derivative. Surprisingly, NDI-1
did not show any charge-transfer interaction with the donor, whereas
NDI-2 could effectively intercalate, leading to a functional membrane
with tunable surface functionalities. This was attributed to the additional
stability of the intercalated state by H-bonding among the hydrazide
units
Stabilizing Entropically Driven Self-Assembly of Self-Immolative Polyurethanes in Water: A Strategy for Tunable Encapsulation Stability and Controlled Cargo Release
Stimuli-responsive amphiphilic polymer
assemblies are of great
interest in the area of targeted drug delivery applications as they
can sequester guest molecules in one set of conditions and release
them under another. Hence, developing a strategy of molar mass controlled
synthesis, in-depth understanding of the thermodynamics of the self-assembly
process, stabilization, and triggered guest release in a controlled
fashion would be highly anticipated in the field of drug delivery
applications. As polymer molar mass has a significant impact on the
self-assembly process or material property of polymers, we focused
on a methodology of controlled molar mass polyurethane synthesis using
recycled plastic waste and synthesized a series of self-immolative
amphiphilic polyurethanes of varying molar masses and polydispersity
indexes. All of the polymers were equipped with periodically grafted
triethyleneglycol monomethyl ether as a pendant, a redox-responsive
disulfide bond, a tertiary amine, and an aromatic moiety on the backbone.
In aqueous milieu, these polymers are found to form entropically driven
nanoassemblies (ΔS > 0), which were further
stabilized by supramolecular cross-linking via the synergistic effect
of π–π stacking (aromatic moiety), H-bonding (urethane
functionality), and hydrophobic interactions, which eventually amplifies
the guest encapsulation stability. A guest release profile in the
presence of a redox environment shows ∼65% release in a controlled
fashion. Furthermore, the tertiary amine on the polymer backbone leads
to the formation of positively charged nanoassemblies at the tumor-relevant
pH (pH ∼ 6.5–6.8), which could potentially enhance the
cellular uptake of nanocarriers in tumor cells. Thus, a strategy for
molar mass controlled polyurethane synthesis, understanding the effect
of polymer molar mass on thermodynamics of self-assembly, establishing
a stable micellar nanostructure endowed with environment-specific
surface charge modulation, and controlled guest release, we believe,
will significantly contribute to the development of robust chemotherapeutics