Rhodopsin-Like Ionic Gate Fabricated with Graphene Oxide and Isomeric DNA Switch for Efficient Photocontrol of Ion Transport.

Rhodopsin, composed of opsin and isomeric retinal, acts as the primary photoreceptor by converting light into electric signals. Inspired by rhodopsin, we have fabricated a light-regulated ionic gate on the basis of the design of a graphene oxide (GO)-biomimetic DNA-nanochannel architecture. In this design, photoswitchable azobenzene (Azo)-DNA is introduced to the surface of porous anodic alumina (PAA) membrane. With modulation of the interaction between the GO blocker and Azo-DNA via flexibly regulating trans and cis states of Azo under the irradiation of visible and ultraviolet light, alternatively, the ionic gate is switched between ON and OFF states. This newly constructed ionic gate can possess high efficiency for the control of ion transport because of the high blocking property of GO and the rather tiny path within the barrier layer which are both first employed to fabricate ionic gate. We anticipate that this rhodopsin-like ionic gate may provide a new model and method for the investigation of ion channel, ion function, and ion quantity. In addition, because of the advantages of simple fabrication, good biocompatibility, and universality, this bioinspired system may have potential applications as optical sensors, in photoelectric transformation, and in controllable drug delivery.

Modularization of three-dimensional gold nanoparticles/ferrocene/liposome cluster for electrochemical biosensor.

For electrochemical biosensors, just like a computer, the modularization and coordinated operation of different components will facilitate the development of versatile biosensors and effectively reduce costs. However, the efficient synergy between different modules is always difficult. It would be a beneficial way to construct the multi-functional module. In this work, a three-dimensional gold nanoparticles/ferrocene/liposome cluster (GFLC) is fabricated and explored as a building block for the fabrication of an electrochemical biosensor, in which gold nanoparticles, ferrocene and liposome cluster work as a signal amplification component, a signal output component and a molecular recognition component, respectively. With the synergy of multi-functions, GFLC has been successfully applied for electrochemical analysis of lipopolysaccharide (LPS) in food samples. LPS can be linearly assayed in the range from 2 × 10-9 µg/mL to 8 µg/mL with a detection limit of 0.51 × 10-10 µg/mL. In view of the favorable modularization effect, GFLC shows a great potential in the development of electrochemical biosensor with considerable versatility and cost-efficiency.