# Mini-Review: Recent Technologies of Electrode and System in the Enzymatic Biofuel Cell (EBFC)
## 3 Current Development on the Bioanode and Biocathode in EBFC  
A strong interaction between support materials and enzymes is needed to strengthen the enzyme's immobilization and reduce enzyme leaching. A study from [PERSON] et al. [32] showed that the resulting covalent bond of anitrophenyl group on the surface of a modified graphene support strengthens interaction with enzyme, which helps the DET process between the graphene support and enzyme. Meanwhile, the study from [PERSON] et al. [61] modified the CNT surface by functionalizing it with polyimide and ZnO to form an interaction support with enzyme and ferritin as a mediator. A high current density of 4.9 mA/cm\({}^{2}\) produced after consuming 50 mM glucose concentration proves an electron  
Figure 4: Illustration of the magnetic activation of bioelectrocatalytic cascades through channeling of enzyme-modified magnetic nanoparticles onto the surfaces of enzyme-functionalized mesoporous carbon nanoparticles [57]. Copyright 2019 Royal Society of Chemistry. transfer that applies efficiently. The same group's research using nickel oxide and silver nanowires showed a higher current density of 5.4 [16] and 19.9 mA/cm\({}^{2}\)[56]. Investigations that use CNT as support material have been carried out widely in EBFC. For example, [PERSON] et al. [62] investigated pyrene(NHS) and Ni\({}^{2+}\)-NTA as a binder of the enzyme on the CNT surface for the bioanode and biocathode. [PERSON] et al. [39] developed a carbon tube by carbonizing rectangular polypyrrole for both the electrode bioanode and biocathode. Temperature changes cause the rectangular structure to change slightly, as shown in Figure 5. The unique morphology of the carbon tube offers a high power density of 0.350 mW/cm\({}^{2}\) and 0.265 mW/mg (GOx). An exciting study from [PERSON] et al. [14] used MWCNT as a support and cellulose nanofiber sheet as the electrode in EBFC. After combining the bioanode and biocathode, the very thin electrode makes it easier to dispose of but gives a high power, as high as 27 \(\mu\)W/cm\({}^{2}\). To reduce the leaching and optimize GOx on the electrode surface, [PERSON] et al. [28] developed the crosslink with chitosan and genipin as support materials, and with nitrobenzoic acid as a new mediator attached to the electrode by chemical bonding. The authors also modified the surface chitosan by distributing the abundant functional evenly on the chitosan surface structure to help covalently bond the GOx and mediator. Analysis showed that the enzyme loading on the electrode surface reached 17.8 mg/mL and produced a current as high as 331 \(\mu\)A/cm\({}^{2}\) at 0.3 V vs. Ag/AgCl and low onset potential (0.05 V vs. Ag/AgCl). [PERSON] et al. [16] directly modified the carbon cloth (CC) substrate with chitosan, commonly used as a biosensor and in biomedical applications, to support glucose oxidase enzyme. The additive assists electron transfer at the electrode, and the modification of the chitosan over the CC requires appropriate additive testing. In this study, sodium tripolypphosphate (TPP) and Nafion were selected as additives, but the results show good electron transfer using TPP. The biocompatibility of the genipin used in EBECs is because it has lower cytotoxicity and is highly efficient to crosslink between chitosan, glucose oxidase, and the amine-containing osmium redox complex developed by [PERSON] et al. [30]. The authors also increased the current density by adding multi-walled carbon nanotubes on the electrode as high as 4.9 mA/cm\({}^{2}\), higher than the previous, which produced only 440 \(\mu\)A/cm\({}^{2}\). The [PERSON] research group [63] further investigated the electrode's scaffold structure by determining the microstructure, electrochemical property, and enzyme loading. The interplay of the electrodes consists of chitosan, Nafion, and/or tripolypphosphate. The electrode comprising all chitosan, Nafion, and tripolypphosphate produced a high power of 1.077 mW/cm\({}^{2}\), compared with the electrode containing chitosan/tripolypphosphate and chitosan/Nafion.