Cationic polymers usually form nanoparticles with DNA or siRNA via ionic interactions.These nanoparticles are easily destabilized by polyanionic molecules abundant in cell culture medium and blood.Though the use of high molecular weight and highly charged polymers can make the nanoparticles more stable to the polyanionic molecules,it results in increased cytotoxicity on the Wansfected cells.There is an urgent need to break up the mnsfection efficacy-cytotoxicity correlation for these cationic polymers in gene delivery.As a result,low molecular weight polymers were fabricated into degradable nanoaggregates to improve their DNA binding capacity without inducing additional cytotoxicity [1].Here,we present a facile strategy to improve stability and transfection efficacy ofpolymer/DNA nanoparticles through specific hydrogen-bond recognition (Fig.1a).