An intracellular glucose biosensor based on nanoflake ZnO

Abstract

Abstract:In this study, a potentiometric intracellular glucose biosensor was fabricated by immobilization of glucose oxidase on nanoflake ZnO. Nanoflake ZnO with a wall thickness around 200 nm was grown on the tip of a borosilicate glass capillary and used as a selective intracellular glucose biosensor for the measurement of glucose concentrations in human adipocytes and frog oocytes. The results showed a fast response within 4 s and a logarithmic linear glucose-dependent electrochemical potential difference over a wide range of glucose concentration (500 nM-10 mM). Our measurements of intracellular glucose were consistent with the values of intracellular glucose concentrations reported in the literature. The monitoring capability of the sensor was demonstrated by following the increase in the intracellular glucose concentration induced by insulin in frog oocytes. In addition, the nanoflake ZnO material provided 1.8 times higher sensitivity than previously used ZnO nanorods under the same conditions. Moreover, the fabrication method in our experiment is simple and the resulting nanosensor showed good performance in sensitivity, stability, selectivity, reproducibility, and anti-interference. All these results demonstrate that the nanoflake ZnO can provide a promising material for reliable measurements of intracellular glucose concentrations within single living cells. Key Words:Glucose oxidase (GOD), Intracellular, Potentiometric biosensor, Nanoflake ZnO, Nafion membrane Among all glucose biosensors, enzyme-based electrochemical glucose biosensors have been in the main focus of biosensor research because of their simplicity, relatively low cost, and high sensitivity [14][15][16]. The intrinsic advantages of electrochemical biosensors are their robustness, easy miniaturization, excellent detection limits, also with small sample volumes, and ability to be used in 3 turbid biofluids. In enzyme-based electrochemical biosensors, enzyme immobilization is regarded to be one of the most important issues. Since proper immobilization of enzymes on a suitable matrix and their stability are important factors in the fabrication of biosensors, the search of support materials that provide large surface area for higher enzyme loading and a compatible microenvironment that helps enzyme bioactivity is thus of great importance.Recently, zinc oxide (ZnO) nanostructures have attracted considerable interest in the applications of biosensors due to many advantages, including non-toxicity, bio-safety, excellent biological compatibility, high electron-transfer rates, enhanced analytical performance, increased sensitivity, and easy preparation [17][18][19][20][21][22]. In addition, it is important to note that ZnO is relatively stable around biological pH-values, which makes ZnO compatible with biological fluids and species [23].Furthermore, the high isoelectric point (IEP) of ZnO (IEP 9.5) makes it a good matrix for immobilizing low IEP acidic proteins or DNA by electrostatic interactions with high binding stability [24][25][26]. This wi...

ZnO nanostructures in enzyme biosensors

“…The effect of the coupling agents, (3-aminopropyl) trimethoxysilane, (3-aminopropyl) triethoxysilane, and (3-aminopropyl) methyldiethoxysilane (APS), on the covalent immobilization of GOx on ZnO nanorods was studied [36]. The APS-treated glucose sensor exhibited the highest sensitivity and lowest K M app , which was attributed to the APS-treated ZnO nanowires containing the largest number of C-N Immobilizing GOx on more complex ZnO nanostructures as working electrodes to detect glucose has also been investigated [12,[37][38][39][40][41][42][43]. Yang et al [37] prepared a highly oriented single-crystal ZnO nanotube array (Fig.…”

“…For a practical serum sample, the biosensors exhibited good accuracy and practicability, with recoveries of 95%-103%. A potentiometric intracellular glucose biosensor was fabricated, by immobilizing GOx on nanoflake ZnO grown on the tip of a borosilicate glass capillary [40]. The nanoflake ZnO (Fig.…”

An electrochemical DNA biosensor based gold-thiolate conjugation utilizing ruthenium complex [Ru(dppz)2(qtpy)]Cl2

“…A considerable amount of literature has been published on ZnO nanostructure in sensors, such as glucose sensor (Fulati et al 2010;Usman Ali et al 2010), ultraviolet detector (Chai et al 2009;Foo et al 2013b) and chemical and gas sensors Kashif et al 2013a). However, ZnO nanostructure with its high isoelectric point (IEP) is the main feature for the low isoelectric point of DNA to immobilize on ZnO nanostructure surface through electrostatic interaction.…”

Characterization of Nanocrystalline ZnO Flakes Synthesized by a Simple Reaction Process

“…ZnO nanoflake structures possess lots of interesting unique proper ties such as porous structures and large surface areas. It is reported that sensors based on ZnO nanoflake structures have an improved performance and a higher sensitivity compared to ZnO nanorods/nanowires 15) . To synthesize uniform nanosized ZnO particles and control their sizes and morphology, a variety of techniques have been used such as thermal oxidation of metallic zinc, hydrothermal methods, plasma chemical synthesis, laser ablation and vapor condensation [16][17][18] .…”