The Brookhaven team, has been refin­ing tech­niques to use strands of arti­fi­cial DNA as a highly spe­cific kind of Vel­cro or glue to link up nanopar­ti­cles. Such DNA-based self-assembly holds promise for the ratio­nal design of a range of new mate­ri­als for appli­ca­tions in mol­e­c­u­lar sep­a­ra­tion, elec­tron­ics, energy con­ver­sion, and other fields. But none of these struc­tures has had the abil­ity to change in a pro­gram­ma­ble man­ner in response to mol­e­c­u­lar stim­uli — until now. “Now we’re using a spe­cial type of DNA-linking device — a kind of ‘smart glue’ — that affects how the par­ti­cles con­nect to make struc­tures that are switch­able between dif­fer­ent con­fig­u­ra­tions,” says Oleg Gang a team lead. This reli­able, reversible switch­ing could be used to reg­u­late func­tional prop­er­ties — for exam­ple, a material’s flu­o­res­cence and energy trans­fer prop­er­ties — to make new mate­ri­als that are respon­sive to chang­ing con­di­tions, or to alter their func­tions on demand.

a) Ide­al­ized schematic illus­trat­ing the struc­ture of the device (l_d) link­age, with A’, D’ and B’ recog­ni­tion sequences. b) A bcc unit cell rep­re­sen­ta­tion of a bulk three-dimensional super­lat­tice con­sist­ing of nanopar­ti­cles A–p and B–p inter­con­nected by l_d. © Nature Pub­lish­ing Group.

Such respon­sive­ness to changes in envi­ron­men­tal con­di­tions and the abil­ity to adopt new forms are hall­marks of liv­ing sys­tems. In that way, these new nano­ma­te­ri­als more closely mimic bio­log­i­cal sys­tems than any pre­vi­ous nanos­truc­tures. Though far from any form of truly “arti­fi­cial life,” these mate­ri­als could lead to the design of nanoscale machines that, at a very sim­ple level, mimic cel­lu­lar processes such as con­vert­ing sun­light into use­ful energy, or sens­ing the pres­ence of other mol­e­cules. Respon­sive mate­ri­als would also have ben­e­fits in the field of optics or to pro­duce reg­u­lated porous mate­ri­als for mol­e­c­u­lar sep­a­ra­tions, Gang says. The sci­en­tists achieved the goal of respon­sive­ness by cre­at­ing struc­tures where the dis­tance between nanopar­ti­cles could be care­fully con­trolled with nanome­ter accuracy.

Nanoscale com­po­nents can be self-assembled into sta­tic three-dimensional struc­tures arrays and clus­ters using bio­mol­e­c­u­lar motifs. The struc­tural plas­tic­ity of bio­mol­e­cules and the reversibil­ity of their inter­ac­tions can also be used to make nanos­truc­tures that are dynamic, recon­fig­urable and respon­sive. DNA has emerged as an ideal bio­mol­e­c­u­lar motif for mak­ing such nanos­truc­tures, partly because its ver­sa­tile mor­phol­ogy per­mits in situ con­for­ma­tional changes using mol­e­c­u­lar stim­uli. This has allowed DNA nanos­truc­tures to exhibit recon­fig­urable topolo­gies and mechan­i­cal move­ment. Recently, researchers have begun to trans­late this approach to nanopar­ti­cle inter­faces where, for exam­ple, the dis­tances between nanopar­ti­cles can be mod­u­lated, result­ing in a distance-dependent plas­monic response. Here, we report the assem­bly of nanopar­ti­cles into three-dimensional super­lat­tices and dimer clus­ters, using a recon­fig­urable DNA device that acts as an inter­par­ti­cle link­age. The inter­par­ti­cle dis­tances in the super­lat­tices and clus­ters can be mod­i­fied, while pre­serv­ing struc­tural integrity, by adding mol­e­c­u­lar stim­uli (sim­ple DNA strands) after the self-assembly processes has been com­pleted. Both sys­tems were found to switch between two dis­tinct rigid states, but a tran­si­tion to a flex­i­ble device con­fig­u­ra­tion within a super­lat­tice showed a sig­nif­i­cant hysteresis.

The pre­sented approach may poten­tially offer the post-assembly reg­u­la­tion of sys­tems with use­ful opto­elec­tronic, energy con­ver­sion and bio-diagnostic prop­er­ties. In addi­tion, the abil­ity to manip­u­late a nanos­truc­ture global sys­tem state opens new oppor­tu­ni­ties for the for­ma­tion of dynam­i­cally self-assembled struc­tures that more closely mimic bio­log­i­cal systems.

Maye, M., Kumara, M., Nyky­panchuk, D., Sher­man, W., & Gang, O. (2009). Switch­ing binary states of nanopar­ti­cle super­lat­tices and dimer clus­ters by DNA strands Nature Nan­otech­nol­ogy DOI: 10.1038/nnano.2009.378

22nd December, 2009