Construction Of DNA Supra-Amphiphiles Through Host-Guest Interactions And Their Self-Assembly Behaviors

Design and synthesis of smart DNA nanostructures is crucial owing to their excellent properties such as biocompatibility,nanoscale size,accurate recognition and that can undergo controllable and reversible morphological change in response to environmental stimulis,hence they hold great potential applications in material science and biomedicine.In general,most stimuli-responsive DNA nanostructures are composed of pure DNA strands through base pairing.So far,self-assembly of DNA amphiphiles has been another effective approach to construct smart DNA nanomaterials.Driven by amphiphilicity,these DNA amphiphiles can spontaneously self-assemble into various well-defined DNA nanoarchitectures such as spherical micelles,nanofibers,vesicles and nanosheets.More interestingly,morphological shift of the DNA assemblies has been achieved through external stimuli,such as pH values,temperature,DNA selective enzymatic activity and host-guest recognition.However,due to the solvent incompatibility of DNA strands and hydrophobic molecules,the solution-phase synthes is often fails.And these DNA amphiphiles can be covalently synthesized from hydrophilic DNA strands and hydrophobic molecules through solid phase synthesis,but the coupling efficiency is always poor.Therefore,it is important to explore the simple and effective methods for the synthesis of DNA amphiphiles.Recently,supramolecular host-guest chemistry has been an effective strategy to construct supra-amphiphiles by conjugating hydrophilic and hydrophobic segments.These supra-amphiphiles can assemble into diverse stimuli-responsive nanomaterials,applied in materials science,supramolecular catalysis,and biochemistry.Doubtlessly,the host-guest approach could be an ideal alternative to construct DNA supra-amphiphiles.To date,the construction of DNA supra-amphiphiles through host-guest interactions has been rarely reported.In addition,cucurbit[7]uril(CB[7])possesses excellent recogniton properties and stronger bonding ability compared with other macrocyclic hosts,such as cyclodextrins and calixarenes.Therefore,in this paper,the host-guest chemistry of CB[7]is introduced into the construction of amphiphilic DNA hybrid,which can not only effectively avoid the problem of solvent incompatibility,but also ensure the efficient coupling efficiency.Moreover,the effect of such different topologic guests or stimuli-responsive guests or different conformation of DNA on the assembled morphology is still unknown.Here,we mainly focused on the following two works:firstly,two DNA supra-amphiphiles were modularly constructed via non-covalent recognition based on the host-guest interaction between cucurbit[7]uril(CB[7])and two different topologic guests(ferrocene derivative G1 or adamantane derivative G2)respectively.CB[7]modified DNA(D18-CB[7])is regarded as the hydrophilic host.Driving by the amphiphility,their self-assembly process and mechanism were investageted.The application of the assembled nanostructures has been further demonstrated.Finally,the stimuli-responsiveness of assemblies induced by competitive guest or by the redox properties of ferrocene has been explored.Secondly,a G-rich sequence,containing thrombin binding aptamer(TBA),was utilized in the construction of DNA supra-amphiphile.In the presence of K~+,it is G-quadruplex.In the absence of K~+,it is a flexible single strand.The DNA supra-amphiphile were constructed through the host-guest interaction between G-rich sequence modified CB[7]and the ferrocene derivative G1.Their self-assembly in different conformation state was studied.Finally,the catalytic performance of the G-quadruplex-based assemblies/hemin complex as peroxides mimic enzymes was initially investigated.