Encapsulation in cooling-induced coacervates augments DNA enzyme activity

When two types of polymers are mixed in aqueous media, liquid droplets resulting from liquid-liquid phase separation are formed. These complex coacervates can entrap biomolecules including protein enzymes. Nucleic acid enzymes entrapped in coacervates have altered activities relative to those in dilute solution. We previously reported that the ureido polymer alone can form a simple coacervate that dissolves upon heating and reforms upon cooling. In this study, we examined the effect of entrapment of a DNA enzyme, the 10-23 DNAzyme, in the simple coacervate induced by cooling of a ureido polymer functionalized with amino groups, poly(allylamine-co-allylurea) (PAU). The copolymer formed coacervate droplets containing DNAzyme and its substrate upon cooling. The activity of the DNAzyme in the droplets was markedly enhanced compared to the reaction in the absence of polymer due to a significant decrease in Km, implying that entrapment promotes formation of the enzyme-substrate complex. Thus, cooling-induced liquid droplets formed by the PAU are efficient reaction media for DNAzymes. The activity of a DNAzyme is enhanced by entrapment in cooling-inducible liquid droplets of UCST-type ureido polymers.