Direct Electron Transfer of Enzymes in a Biologically Assembled Conductive Nanomesh Enzyme Platform

Significance Statement

Recently, wearable biomedical sensors that enable non-invasive monitoring of health condition have been attracting drastically increasing interest. In particular, a non-invasive device that can measure glucose levels in bio-fluid such as tear, saliva, and sweat is regarded as one of the most promising biosensor platforms for future healthcare application. Bio-fluids have been known to contain informative indicators (i.e., glucose). Moreover, they are naturally and continuously excreted from the human body. Therefore, a wearable glucose sensor that is placed or attached on a body could continuously measure glucose levels in a non-invasive manner and real rime. Thus, patients do not have to prick their fingers for blood collection every time, and it would ultimately reduce the pain of diabetes patients and prevent the possible secondary infection.

Current blood glucometers best work for measuring glucose level in blood. Meanwhile, the glucose concentration in tear, saliva, or sweat, are about 20~100 times lower than that in blood glucose. In addition, at this low glucose level, the interfering redox species, such as ascorbic acid, uric acid or acetaminophen, greatly influence the sensor performance. Therefore, to realize non-invasive and wearable monitoring of glucose levels, the flexible biosensor platform must own much more enhanced sensitivity and selectivity than current blood glucometers. Furthermore, the biosensor has to be non-toxic for wearable purpose. Considering all these requirements for wearable biomedical sensors, the 3rd generation biosensor platform that employs the direct-electron-transfer (DET) mechanism of enzymes would be a promising candidate. Owing to the direct electrical communication with enzymes at the negative potential range, being apart from the oxidation potential of interfering redox species by -600 mV, the sensor can achieve both high sensitivity at sub-millimolar level and excellent selectivity on target analytes. Moreover, since the electrode and the enzyme directly communicate, no chemical mediator is required. Therefore, DET obviates the toxicity issues involved in the chemicals.

To achieve efficient DET of enzymes, realizing intimate electrical contacts with redox biomolecules at nanoscale is of crucial importance. In this work, we report a new approach that enables highly facilitated biomolecular electron transfer with unprecedented versatility and applicability. Enzymes are intimately interfaced with a conductive nanomesh made of single-walled carbon nanotubes (SWNTs) via a rationally designed interlayer. SWNTs are hydro-dynamically assembled into a conductive nanomesh by using a filamentous phage that shows a strong binding affinity toward SWNTs. The nanostructure of the nanomesh is extremely well controlled over large area. The filamentous phage controls the nanostructure and at the same time serves as a biological glue to stabilize the nanomesh structure in solution. The conductive nanomesh is then transferred onto metallic electrodes to produce a nanostructured electrical platform for biomolecular direct electron transfer (DET). The conductive nanomesh is then rationally interfaced with enzymes by using a polyelectrolyte layer with appropriate charge characteristics. This interfacial layer enables both intimate nanoscale electrical contacts to biomolecules for facilitated electron transfer and highly porous nanostructures for high sensitivity.

Using this layered conductive nanomesh enzyme platform, we successfully achieve DET for eight different enzymes (including glucose oxidase and lactate oxidase) with various types of catalytic activities. The direct electrical communication of enzymes on the conductive nanomesh enables not only the high sensitivity at sub-millimolar level of target (i.e, glucose or lactate), but also the high selectivity of the sensor due to the operation at negative potential range. We further demonstrate a flexible DET-based glucose-biosensor, for the first time, to the best of our knowledge. The electron transfer efficiency and sensitivity of these flexible integrated biosensors are comparable to those obtained using commercialized screen printed electrodes.

We believe that the biologically assembled conductive nanomesh enzyme platform presents a promising solution for future health-monitoring systems. 

Direct Electron Transfer of Enzymes in a Biologically Assembled Conductive Nanomesh Enzyme Platform- Global Medical Discovery

About the author

Dr. Hyunjung Yi received her B.S. and M.S. degrees from Pohang University of Science and Technology (POSTECH), Pohang, Korea, in the department of Material Science and Engineering and Ph. D. degree from Massachusetts Institute of Technology (MIT), Cambridge, USA in the department of Material Science and Engineering in 2001, 2003, and 2011, respectively.

Dr. Hyungjung Yi joined Korea Institute of Science and Technology (KIST), Seoul, Korea, in 2003 as a research scientist and is currently a Principal Investigator and a Senior Research Scientist.

Dr. Hyunjung Yi’s research focuses on developing nano-bio hybrid materials for wearable biosensors, electronics, tactile sensors, and flexible energy devices. Biotechnology to genetically engineer biomaterials and processes to assemble and fabricate nano-bio hybrid are also being developed.

About the author

Dr. Seung-Woo Lee received B.E. in Fine chemical engineering & Applied chemistry at Chungnam National University in 2006, and Ph.D. in chemical and biomolecular engineering at University of Nebraska-Lincoln in 2013, respectively.

He joined Dr. Hyunjung Yi’s Lab at Korea Institute of Science and Technology (KIST) in 2014.

His research mainly focuses on the electrochemical biosensor, wearable/flexible nano-bio electronics, non-destructively assembly of nano-bio hybrid biosensing materials, and electrochemical bio-energy generation.


Adv Mater. 2016 Feb;28(8):1577-84.

Lee SW1, Lee KY1, Song YW1, Choi WK2, Chang J1, Yi H1.

[expand title=”Show Affiliations”]

1Post-Silicon Semiconductor Institute, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.

2Materials and Life Science Research Division, Korea Institute of Science and Technology, Seoul, 136-791, Republic of Korea.




Nondestructive assembly of a nanostructured enzyme platform is developed in combination of the specific biomolecular attraction and electrostatic coupling for highly efficient direct electron transfer (DET) of enzymes with unprecedented applicability and versatility. The biologically assembled conductive nanomesh enzyme platform enables DET-based flexible integrated biosensors and DET of eight different enzyme with various catalytic activities.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


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