Biomolecular logic devices based on stimuli-responsive PNIPAM-DNA film electrodes and bioelectrocatalysis of natural DNA with Ru(bpy)32+ as mediator.

In the present work, PNIPAM-DNA films were fabricated on the surface of electrodes by GOD-induced radical polymerization, where PNIPAM is poly(N-isopropylacrylamide), DNA represents natural DNA from salmon testes, and GOD is glucose oxidase. The prepared film electrodes demonstrated reversible temperature-, SO42--, and pH-switched cyclic voltammetry (CV) and electrochemiluminescence (ECL) behaviors toward tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) in solution. Particularly, both CV and ECL signals at 1.15 V belonging to Ru(bpy)32+ were significantly amplified by the electrocatalysis of DNA in the films. Moreover, the addition of ferrocenemethanol (FcMeOH) into the solution led to the substantial quenching of the ECL signal of the system and produced a new CV peak pair at 0.35 V. Based upon these experiments, a 4-input/7-output logic gate system was successfully built, which also lead to a 2-to-1 encoder and a 1-to-2 decoder. On the same platform, a more complicated logic device, a half-adder, was also constructed. The present system combined electrocatalysis of natural DNA mediated by Ru(bpy)32+ and multiple stimuli-responsive PNIPAM-DNA films together with simultaneously obtained CV and ECL signals as outputs, leading to the development of novel types of biocomputing systems.