Fig. 2.

Application of linear DNA polymeric topologies in molecular diagnosis and gene regulation. (A) Oligonucleotide detection based on aggregation of DNA-modified AuNPs. Introduction of a target ssDNA into a solution containing AuNPs functionalized with complementary DNA sequences resulted in the formation of an aggregated network of nanoparticles with a corresponding red-to-purple color change. Reproduced from reference [33] with permission. (B) DNA-AuNP conjugates as biobarcodes. Each target molecule is coded by ssDNA with specific sequences and lengths. The target molecule binds specifically to a monoclonal antibody on a magnetic microparticle and is sandwiched by the DNA-AuNP containing the corresponding polyclonal antibody and the ssDNA barcodes. The ssDNA barcodes are subsequently released for specific identification of the target molecule. Reproduced from reference [47] with permission. (C) DNA-mediated reversible sol-gel transitions. Polyacrylamide modified with DNA sequences SA1 and SA2 crosslinks with the addition of a target sequence, L2, partially complementary to both SA1 and SA2. Upon addition of a removal strand that hybridizes completely with L2, the crosslinking is disrupted and the gel reverts to a liquid state.