1.Amperometric immunosensor for the detection of Escherichia coli O157:H7 in food specimens.
Li Y1, Cheng P, Gong J, Fang L, Deng J, Liang W, Zheng J. Anal Biochem. 2012 Feb 1;421(1):227-33. doi: 10.1016/j.ab.2011.10.049. Epub 2011 Nov 4.
A novel, label-free amperometric immunosensor has been developed for the rapid detection of heat-killed Escherichia coli O157:H7 (E. coli O157:H7). This immunosensor was prepared as follows. First, the long-chain, amine-terminated alkanethiol 11-amino-1-undecanethiol hydrochloride (AUT) was self-assembled onto a gold electrode surface to form an ordered, oriented, compact, and stable monolayer possessing -NH(2) functional groups that could immobilize massive gold nanoparticles (GNPs). Next, chitosan-multiwalled carbon nanotubes-SiO(2)/thionine (CHIT-MWNTs-SiO(2)@THI) nanocomposites and GNPs multilayer films were prepared via layer-by-layer (LBL) assembly. The surface area enhancement from the LBL assembly of the multilayer films improves the stability of the immobilized CHIT-MWNTs-SiO(2)@THI. More important, the sensitivity and stability of the immunosensor can be enhanced proportionally to the quantity of the THI mediator immobilized on the electrode surface.
2.Cholesterol biosensor based on amino-undecanethiol self-assembled monolayer using surface plasmon resonance technique.
Solanki PR1, Arya SK, Nishimura Y, Iwamoto M, Malhotra BD. Langmuir. 2007 Jun 19;23(13):7398-403. Epub 2007 May 25.
Cholesterol oxidase has been covalently immobilized onto 11-amino-1-undecanethiol hydrochloride (AUT) self-assembled monolayer (SAM) fabricated on gold (Au) substrates using glutaraldehyde as a cross-linker. These ChOx/AUT/Au bioelectrodes characterized using contact angle (CA) measurements; electrochemical technique and atomic force microscopy (AFM) have been utilized for the estimation of cholesterol in solution using the surface plasmon resonance (SPR) technique. These biosensing electrodes exhibiting linearity from 50 to 500 mg/dL of cholesterol in solution and sensitivity of 1.23 m0/(mg dL), can be used more than 20 times and have a shelf life of about 10 weeks when stored at 4 degrees C.
3.Effect of self-assembled monolayers (SAMs) in binding glucose oxidase for electro-enzymatic glucose sensor with gold electrodes.
Patel JN1, Kaminska B, Gray B, Gates BD. Conf Proc IEEE Eng Med Biol Soc. 2007;2007:2677-80.
In this paper, a new approach to improve long term stability of electro-enzymatic glucose sensors is presented. Self-assembled monolayers (SAMs) are employed for surface treatment of the gold electrodes to improve adhesion. Three types of functional alkylthiols, namely 11-amino-1-undecanethiol hydrochloride, 1-hexadecanethiol (1-hydrochloride, and 1,9-nonanedithiol, and bovine serum albumin (BSA) are investigated in our study. Alkylhiols are used for surface treatment of gold electrodes and BSA is mixed in enzyme (glucose oxidase) solution to realize the proposed sensors. Furthermore, gold is investigated as an electrode material. Both reference and active electrodes are fabricated using only gold. The current response of the modified sensors showed long term stability. However, the unmodified sensors showed very short term stability because glucose oxidase does not adhere well to the electrodes. The proposed modified sensors also show lower drift than the unmodified sensors without surface treatment and BSA.