Constructing a Facile Biocomputing Platform Based on Smart Supramolecular Hydrogel Film Electrodes with Immobilized Enzymes and Gold Nanoclusters

Abstract

Herein, fluorescent gold nanoclusters (AuNCs) and horseradish peroxidase (HRP) were simultaneously embedded into self-assembled dipeptide supramolecular films of N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF) on the surface of ITO electrodes (Fmoc-FF/AuNCs/HRP) by using a simple single-step process. In the films, both the fluorescence property of AuNCs and the bioelectrocatalytic property of HRP were well maintained and could be reversibly regulated by pH-sensitive structural changes in the Fmoc-FF hydrogel films. Cu­(II)/EDTA in the solution could lead to the aggregation/disaggregation of AuNCs and further quenching/dequenching the fluorescence signal from the films. Meanwhile, the blue complexes formed by Cu­(II) and EDTA could produce a UV–vis signal in the solution. In addition, the coordinated Cu­(II) in the films enhanced the electrocatalytic capacity toward the reduction of H2O2 and could switch the current signal. A biomolecular logic circuit was built based on the smart film electrode system by using pH, the concentrations of EDTA, Cu­(II) and H2O2 as inputs, while the fluorescence intensity (FL), current (I) and UV–vis extinction (E) of the solution as outputs. Various logic devices were fabricated using the uniform platform, consisting of an encoder/decoder, demultiplexer, dual-transfer gate, keypad lock, digital comparator, half adder, and controlled NOT (CNOT) gate. Specifically, an electronic three-value logic gate, gullibility (ANY) gate, was first mimicked in this biocomputing system. This work not only demonstrated the construction of a new type of multivalued logic gate by using a dipeptide micromolecular matrix but also provided a new approach for designing sophisticated biologic functions, establishing smart multianalyte biosensing or fabricating biology information processing through the use of a simple film system.

Implementation of novel boolean logic gates for IMPLICATION and XOR functions using riboregulators

“…When both input trigger RNAs were added, the RBS of the toehold switch would be exposed and allow ribosome binding, which would break to open the stable 3WJ hairpin, allowing downstream genes to translate ( Figure 5(a,b) ). The output was divided into 0 and 1 according to the threshold (relative fluorescence intensity: 50%) [ 4 , 5 ]. Measurements of IMP gate was shown a high GFP fluorescence intensity in the logical TRUE condition (Output = 1), which was at least six times higher than the logical FALSE condition (Output = 0) that only trigger-RNA B was inputted ( Figure 5(c,d) ).…”

“…However, when both triggers were input simultaneously, they pair with each other and form a ring in the middle, so the switch remains in the OFF state ( Figure 6(a,b) ). The outputs which were larger than the threshold value (relative fluorescence intensity: 50%) were in the ‘0’ state and others were in the ‘1’ state [ 4 , 5 ]. GFP fluorescence intensity was significantly reduced when no input or both inputs are present.…”

“…The negative control is the competent BL21 Star DE3 strain without any plasmid. The outputs are identified as ‘0’ and ‘1’ according to the threshold (relative fluorescence intensity: 50%) [ 4 , 5 ].…”

“…DNA, RNA, and proteins all have the potential to be assembled into circuits for the design of programmable modules [ 1–3 ]. In addition, biocomputing systems can be developed with multiple stimulus-responsive film electrodes and bioelectrocatalysis based Boolean logic gates [ 4–6 ]. However, the standardization of such modules is still facing many problems, including cross-talk, noise, and mutations [ 7 ].…”

The Construction of Stimulus‐responsive Film Electrode by the Cu‐catalyzed Radical Polymerization and its Application in Multi‐valued Biologic Systems

“…In general, the reported systems with pH-responsive behavior relied heavily on polyelectrolyte films. The response mechanisms included changes in the structure or surface charge of the films caused by changes in the pH of the solution, which affect the transfer process of the probe to the electrode [30]. However, in the present work, our attention is focused on the properties of Fc(COOH), which is not only an electroactive probe but also a weak acid [24].…”