Abstract
Separative extended gate field effect transistor (SEGFET) type devices have been used as an ion sensor or biosensor as an alternative to traditional ion sensitive field effect transistors (ISFETs) due to their robustness, ease of fabrication, low cost and possibility of FET isolation from the chemical environment. The layer-by-layer technique allows the combination of different materials with suitable properties for enzyme immobilization on simple platforms such as the extended gate of SEGFET devices enabling the fabrication of biosensors. Here, glucose biosensors based on dendrimers and metallophthalocyanines (MPcs) in the form of layer-by-layer (LbL) films, assembled on indium tin oxide (ITO) as separative extended gate material, has been produced. NH3+ groups in the dendrimer allow electrostatic interactions or covalent bonds with the enzyme (glucose oxidase). Relevant parameters such as optimum pH, buffer concentration and presence of serum bovine albumin (BSA) in the immobilization process were analyzed. The relationship between the output voltage and glucose concentration shows that upon detection of a specific analyte, the sub-products of the enzymatic reaction change the pH locally, affecting the output signal of the FET transducer. In addition, dendritic layers offer a nanoporous environment, which may be permeable to H+ ions, improving the sensibility as modified electrodes for glucose biosensing.
Highlights
The field effect transistor (FET) concept, combined with the high specificity of enzymes, has led to the development of a series of sensing devices to measure analytes of clinical and environmental interest [1,2]
The measuring principle of FET-based glucose biosensor proposed in this work is based on pH deviation, caused by the following reaction [6]: glucose oxidase (GOx)
We have introduced a separative extended gate FET (SEGFET) pH sensor based on LbL films of poly(propylene imine) dendrimer (PPI) and nickel tetrasulphonated phthalocyanine (NiTsPc) self-assembled on indium tin oxide (ITO) or gold (Au) as separative extended gate [10]
Summary
The field effect transistor (FET) concept , combined with the high specificity of enzymes, has led to the development of a series of sensing devices to measure analytes of clinical and environmental interest [1,2]. Inorganic and some biomolecules, with oppositely reactive groups, can be combined resulting in composites with distinct and unique properties when self-assembled into substrates of different kinds and sizes In this way suitable systems are formed on the last layer for enzyme immobilization and these self-assembled platforms can be implemented as extended gates to be applied in FET-based biosensors. We have introduced a SEGFET pH sensor based on LbL films of poly(propylene imine) dendrimer (PPI) and nickel tetrasulphonated phthalocyanine (NiTsPc) self-assembled on indium tin oxide (ITO) or gold (Au) as separative extended gate [10] This system exhibited good sensitivity over a pH range from 4 to 10.
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