A new class of hydrogels utilizing DNA (DNA quadruplex gel) has been constructed by directly and symmetrically coupling deoxynucleotide phosphoramidite monomers to the ends of polyethylene glycols (PEGs) in liquid phase, and using the resulting DNA‐PEG‐DNA triblock copolymers as macromonomers. Elongation of merely four deoxyguanosine residues on PEG, which produces typically ≈10 grams of desired DNA‐PEG conjugates in one synthesis, resulted in intelligent and biodegradable hydrogels utilizing DNA quadruplex formation, which are responsive to various input signals such as Na+, K+, and complementary DNA strand. Gelation of DNA quadruplex gels takes place within a few seconds upon the addition of a trigger, enabling free formation just like Ca+‐alginate hydrogels or possible application as an injectable polymer (IP) gel. The obtained hydrogels show good thermal stability and rheological properties, and even display self‐healing ability.
A new
pH-responsive hydrogel biomaterial, that is composed of solely
two popular biocompatible materials, oligodeoxynucleotides (ODN) and
polyethylene glycol (PEG) have been prepared. Merely five deoxycytidine
residues were elongated to the ends of linear or 4-arm PEG in ×1000
larger scale than conventional systems by using liquid-phase DNA synthesis
technique, and applied them as a macromonomer for the preparation
of hydrogels. The syntheses of the conjugates are simply elongating
ODN onto the ends of PEG as a semisolid phase substrate using standard
phosphoramidite chemistry. The resulting dC5-PEG conjugates gave quite
stable and stiff hydrogels triggered by the formation of a unique
DNA quadruplex, i-motif. Introduction of only one chemical linkage
between two linear conjugates resulted in unexpectedly high thermal
stabilities for the melting temperatures of i-motifs themselves. Nonlinearly
improved rheological properties compared to the original linear conjugates
were also observed, probably because of topological entanglement between
macromonomers of fused circles.
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