(Invited) DNA Quadruplex Hydrogels: An Application of Synthetic DNA As Bulk Material

Abstract

DNA is a water-soluble and biodegradable polymer, which forms right-handed double helices and carries genetic information in life. Because of its high structure regularity and sequence programmability, DNA has been used as a key component in development of functional nanomaterial. Despite such success in nanoscience, reports on application of DNA to typical material, i.e. hydrogels, are very few, except for some excellent achievements, because preparation of DNA in gram scales usually requires unreasonable costs. One solution for this problem is liquid-phase DNA synthesis method developed by Bonora et al. They used monofunctional MeO-PEG as a soluble polymeric support, which enables coupling reaction of phosphoramidite monomers in liquid phase and can be easily precipitated by ether addition for product separation. We have applied this system to synthesize DNA-PEG-DNA tri-block copolymer in grams, and successfully prepared biodegradable PEG hydrogels by using higher-order DNA structures, such as G-quadruplexes, for cross-linking points. Aqueous solution of a tri-block copolymer bearing multiple guanosines at the ends, for example, immediately turns into gel upon addition of Na+ or K+ ions at reasonable concentration. Various body-related fluids such as PBS, artificial saliva, sweat, or tear can trigger gelation. The resulting hydrogels are self-healable since the crosslinking points are stable but still reversible structure. Moreover, introduction of toehold sequence realized complete control of such sol-gel transition by the addition of complementary DNA strand.