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A New Route to the Considerable Enhancement of Glucose Oxidase (GOx) Activity: The Simple Assembly of a Complex from CdTe Quantum Dots and GOx, and Its Glucose Sensing
Author(s) -
Cao Lihua,
Ye Jian,
Tong Lili,
Tang Bo
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800681
Subject(s) - glucose oxidase , quantum dot , simple (philosophy) , nanotechnology , chemistry , materials science , biosensor , philosophy , epistemology
A new complex consisting of CdTe quantum dots (QDs) and glucose oxidase (GOx) has been facilely assembled to achieve considerably enhanced enzymatic activity and a wide active temperature range of GOx; these characteristics are attributed to the conformational changes of GOx during assembly. The obtained complex can be simultaneously used as a nanosensor for the detection of glucose with high sensitivity. A mechanism is put forward based on the fluorescence quenching of CdTe QDs, which is caused by the hydrogen peroxide (H 2 O 2 ) that is produced from the GOx‐catalyzed oxidation of glucose. When H 2 O 2 gets to the surface of the CdTe QDs, the electron‐transfer reaction happens immediately and H 2 O 2 is reduced to O 2 , which lies in electron hole traps on CdTe QDs and can be used as a good acceptor, thus forming the nonfluorescent CdTe QDs anion. The produced O 2 can further participate in the catalyzed reaction of GOx, forming a cyclic electron‐transfer mechanism of glucose oxidation, which is favorable for the whole reaction system. The value of the Michaelis–Menton constant of GOx is estimated to be 0.45 m M L −1 , which shows the considerably enhanced enzymatic activity measured by far. In addition, the GOx enzyme conjugated on the CdTe QDs possesses better thermal stability at 20–80 °C and keeps the maximum activity in the wide range of 40–50 °C. Moreover, the simply assembled complex as a nanosensor can sensitively determine glucose in the wide concentration range from micro‐ to millimolar with the detection limit of 0.10 μ M , which could be used for the direct detection of low levels of glucose in biological systems. Therefore, the established method could provide an approach for the assembly of CdTe QDs with other redox enzymes, to realize enhanced enzymatic activity, and to further the design of novel nanosensors applied in biological systems in the future.