A new biocatalyst employing pyrenecarboxaldehyde as an anodic catalyst for enhancing the performance and stability of an enzymatic biofuel cell

Abstract

A new enzyme catalyst consisting of pyrenecarboxaldehyde (PCA) and glucose oxidase (GOx) immobilized on polyethyleneimine (PEI) and a carbon nanotube supporter (CNT/PEI/[PCA/GOx]) is suggested, and the performance and stability of an enzymatic biofuel cell (EBC) using the new catalyst are evaluated. Using PCA, the amount of immobilized GOx increases (3.3 U mg − 1 ) and the electron transfer rate constant of the CNT/PEI/[PCA/GOx] is promoted (11.51 s − 1 ). Also, the catalyst induces excellent EBC performance (maximum power density (MPD) of 2.1 mW cm − 2 ), long-lasting stability (maintenance of 93% of the initial MPD after 4 weeks) and superior catalytic activity (flavin adenine dinucleotide redox reaction rate of 0.62 mA cm − 2 and Michaelis-Menten constant of 0.99 mM). These characteristics are ascribed to effects of (i) electron collection due to hydrophobic interactions, (ii) electron transfer pathways due to π-conjugated bonds and (iii) enzyme stabilization due to π-hydrogen bonds that are newly induced by the PCA/GOx composite. The existence of such positive interactions is properly verified using X-ray photoelectron spectroscopy and enzyme activity measurements. NPG Asia Materials (2017) 9, e386; doi:10.1038/am.2017.75; published online 2 June 2017 INTRODUCTIONThe demand for clean electrical energy is increasing as a result of weather changes caused by the greenhouse effect and depletion of fossil fuels. 1 To meet this demand, related research and development efforts are being eagerly pursued. As one of the efforts, enzymatic biofuel cells (EBCs) that convert bioenergy into electrical energy are being considered. 2,3 In particular, EBC systems employing glucose oxidase (GOx) as a biocatalyst have emerged because of their advantageous properties, such as biocompatibility, excellent selectivity toward specific substrates and strong activity near neutral pH and room temperature. 2 In addition, because EBC systems use human body-friendly fuels, such as glucose, glycerol, water and oxygen, for electricity generation, they can be embedded as power generators for the operation of artificial internal organs, such as artificial hearts and brains, insulin pumps or bone stimulators. [4][5][6][7][8] However, in spite of such promising facets of EBC systems, the commercialization of EBCs using GOx has been limited because of their low EBC performance and poor durability. 9 The disadvantages are attributed to the low immobilization ratio of GOx molecules, slow GOx-related reaction rate, low GOx activity and easy GOx denaturation. Of them, low GOx immobilization has been considered the main problem.

Recent Advances in the Direct Electron Transfer-Enabled Enzymatic Fuel Cells

“…Polyethyleneimine (PEI) is also widely used to immobilize enzymes while exhibiting water miscibility and high biocompatibility as well as offering various surface chemistries for stable binding to electrode surfaces or other nanomaterials ( Figure 4 ) (Christwardana et al, 2017 ; Sapountzi et al, 2017 ; Tavahodi et al, 2017 ). PEI is typically used along with carbon nanotubes (Christwardana et al, 2016 , 2017 ) or metallic nanoparticles (Zeng et al, 2015 ; Chung et al, 2017a ; Christwardana et al, 2018 ) to increase the stability of enzyme immobilization.…”

“… Schematic of (A) fabrication of various GOx-functionalized electrodes and their mechanism of immobilization; (B) comparison between native GOx and GOx/PCA composite (Christwardana et al, 2017 ). …”

Electrochemical Study of Enzymatic Glucose Sensors Biocatalyst: Thermal Degradation after Long-Term Storage

“…GOx is attached on the surface of the CNT surface by hydrophobic interaction and a little bit of adsorption, but leakage over time is more prone to happen when the bonding between them is not strong. The electron transfer mechanism and efficiency of CNT/GOx and CNT/PEI/GOx was investigated by CV measurements, at scan rates from 100 to 1600 mV•s −1 , according to [22]. The obtained current peaks were plotted vs. scan rate as shown in Figure 2b.…”

“…These values are higher if compared to other GOx-based catalyst structures. For instance, ITO/CzS/GOx has Γ value of 2.5-2.8 × 10 −12 mol•cm −2 [25], GOx/Ag@MWCNT-IL-Fe3O4/MGCE The electron transfer mechanism and efficiency of CNT/GOx and CNT/PEI/GOx was investigated by CV measurements, at scan rates from 100 to 1600 mV•s −1 , according to [22]. The obtained current peaks were plotted vs. scan rate as shown in Figure 2b.…”

Maximizing the enzyme immobilization of enzymatic glucose biofuel cells through hierarchically structured reduced graphene oxide

“…[18][19][20] One of the most common enzymes used in EBFCs is GOx. [21][22][23] Because GOx has excellent catalytic stability and good glucose selectivity, many studies have utilized GOx as catalyst in applications such as blood glucose sensors and EBFCs. [24][25][26][27][28] Another important attribute of GOx is that this does not decompose glucose by itself; thus, to complete the decomposition of glucose, a mediator is needed.…”