pH-induced on/off-switchable graphene bioelectronics

Abstract

Switchable interfaces can deliver functionally reversible reactivity with their corresponding analytes, which allows one to positively respond to the activity of biological elements, including enzymes and other biomolecules, through an encoded stimulus. We have realized this by the design of stimuli-responsive graphene interfaces for the pH-encoded operation of bioelectronics. Herein, we have demonstrated stimuli-responsive graphene interfaces for the pH-encoded operation of bioelectronics. The resulting switchable interfaces are capable of the highly specific, on-demand operation of biosensors, which has significant potential in a wide range of analytical applications.

pH-Controllable Bioelectrocatalysis Based on Surface Charge and Conformation Switching of Nonelectroactive Protein

“…The result is apparently opposite to that of the nonelectroactive protein modified on electrode in previous reports [10,24]. But, it exactly proves that the protonated Lys exhibits a strong electrostatic attraction with negatively charged Fe(CN) 6 3 at pH 6.19, leading to the decrease of semicircle R et on the Lys/L-Cys/Au electrode.…”

“…In this work, Lys was used as a model protein and immobilized onto a gold electrode by incorporation of covalent bond and self assembly, which are easy, stable, effective, and frequently-used methods to fabricate electrochemical sensors. The resulted interface exhibited good pH-sensitive on-off behavior towards the electroactive Fe(CN) 6 3 probe and showed high sensitivity for the bioelectrocatalytic reduction of H 2 O 2 . Furthermore, for better understanding the mechanism of the pH-dependent properties, the conformation of Lys was explored and evaluated by changing the surrounding pH.…”

“…N-hydroxysuccinimidyl sodium salt (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) were obtained from Aldrich. Potassium ferricyanide (K 3 Fe(CN) 6 ) and H 2 O 2 (30%) were purchased from Sinopharm Chemical Reagent Co. Ltd (Shanghai). K 3 Fe(CN) 6 solution (1.0 mM) containing 0.1 M KCl was used as an electrolyte and its pH was adjused by HCl and NaOH.…”

“…The resulted Lys/L-Cys/Au electrode exhibits the onoff switching property at two typical pH values, pH 6.19 and 12.13. Generally, as shown in Scheme 1, at pH 6.19, the protonated amino acid residues of Lys are positively charged due to its isoelectronic point (pI) at about 11.0 [23], which consequently causes a strong electrostatic attraction with negatively charged Fe(CN) 6 3 . This will make the probe go though the Lys/L-Cys film and the film turns to "on state".…”

“…For this researching objective, one of the major challenges is to realize the controllable or stimuli-responsive bioelectrocatalysis [2]. Among various external stimuli such as pH [1], ionic strength [3], temperature [4], and electric field [5], pH has been frequently used due to the simplicity and accuracy [1,6]. At the same time, a lot of functional materials, electron-transfer mediators, redox enzymes, and proteins have been used to modify electrodes and amplify the electrical signal [710].…”