Supra-Amphiphiles for Controlled Self-Assembly and Disassembly - Molecular Self-Assembly: Advances and Applications - page 216

6.4.2 Responsive Carriers

Supra-amphiphiles are new building blocks for self-assemblies
and these self-assemblies can be used for the incorporation of
guest molecules. If the amphiphilicity of the supra-amphiphile
can be weakened by environmental stimuli, the self-assembled
nanostructures will disassemble and the loaded guest molecules
can be released from the assemblies subsequently, providing new
carriers for cargoes or drugs.
For example, we have designed and prepared a photo-
responsive supra-amphiphile using a double hydrophilic block
copolymer, polyglycol-b-polyvinyl acid (PEG-b-PAA), and a small
organic amphiphile containing a positively charged headgroup
and an azobenzene at the end (Azo) [14]. PEG-b-PAA and Azo can
be complexed into a supra-amphiphile (PEG-b-PAA-Azo) driven
by electrostatic attractions. PEG-b-PAA-Azo can self-assemble in
water to form vesicles. Upon UV irradiation, the azobenzene groups
transfer from trans-form to cis-form, inducing the disassembly of
the vesicles and then releasing the loaded guest molecules.
The similar idea can be extended to a redox-responsive supra-
amphiphiles by complexing a double hydrophilic polymer with a
redox-responsive moiety [35]. An oxidation-responsive polymeric
supra-amphiphile is fabricated on the basis of the electrostatic
interaction between the double hydrophilic block copolymer of
poly(ethylene glycol)-b-acrylic acid (PEG-b-PAA) and a selenium-
containing surfactant. The polymeric supra-amphiphile self-
assembles to form micelles in solution, which can be disassembled
under very mild oxidation like 0.1% H because the selenium-

containing surfactant is very sensitive to oxidation (Fig. 6.8). Such
micelles can be used as nanocontainers to load guest molecules, and
the guest molecules can be released in a controlled way under mild
oxidation. The advantages of such system include the avoidance of
organic solvents, a simple preparation procedure, and the decrement
of surfactants.
Besides synthetic building blocks, many natural molecules are
alternatives for fabricating responsive supra-amphiphiles. Let us
take adenosine triphosphate (ATP), the “energy currency” in living
bodies, as an example. A natural ATP molecule, which contains four

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