Label-free immunosensors

S. Grant, F. Davis, K.A. Law, A.C. Barton, S.D. Collyer, S.P.J. Higson, and T.D. Gibson, Label-free and reversible immunosensor based upon an AC impedance interrogation protocol. Anal. Chim. Acta 537, 163-168 (2005). 

Z.H. Wang and G. Jin, A label-free multisensing immunosensor based on imaging ellipsometry. Anal. Chem. 75, 6119-6123 (2003). 

Electrochemical immunosensors are a powerful tool for the analysis of antibacterials in food and different configurations have been presented during recent years. For example, an amperometric immunosensor was reported by Wu et al. [182], for penicillin quantification in milk, with a linear range from 0.25 to 3 ng/ml and a limit of detection of 0.3 pg/L [182]. Other types of transduction have been also explored, like a label-free impedimetric flow injection immunosensor for the detection of penicillin G. 

Ionescu, R.E., N. Jaffrezic-Renault, L. Bouffier, et al. 2007. Impedimetric immunosensor for the specific label free detection of ciprofloxacin antibiotic. Biosens. Bioelectron. 23 549-555. 

Engstrom HA, Andersson PO, Ohlson S (2006) A label-free continuous total-intemal-reflection-fluorescence-based immunosensor. Anal Biochem 357 159-166 Sapsford KE, Rasooly A, Taitt CR et al (2004) Detection of Campylobacter and Shigella species in food samples using an array biosensor. Anal Chem 76 433 140 Sapsford KE, Taitt CR, Loo N et al (2005) Biosensor detection of botulinum toxoid A and staphylococcal enterotoxin B in food. Appl Environ Microbiol 71 5590-5592... 

A label-free electrochemical impedance immunosensor for the rapid detection of E. coli 0157 H7 consists of immobilized anti- . coli antibodies on an indium-tin oxide IDA microelectrode [123]. The binding of E. coli cells to the IDA microelectrode surface increases the electron-transfer resistance, which is directly measured with electrochemical impedance spectroscopy in the presence of [Fe(CN)(6)] as a redox probe. The electron-transfer resistance correlates with the concentration of E. coli cells in a range from 4.36 X 10 to 4.36 X 10 cfu ml with a detection Umit of 10 cfu ml . ... 

At present, a variety of label-free detection strategies are available for biomedical research, such as surface plasmon resonance (SPR), CNTs, cantilevers, surface-enhanced laser desorption ionization (SELDI)-time of flight (TOF)-mass spectrometry (MS), microfluidic purification chips, immunosensors... 

The use of enzyme labels in ELIS A-type immunosensors and simple amperometric detection schemes resulted in simple and cost-effective alternatives to fluorescence immunosensors. In particular, the use of alkaline phosphatase as enzyme label allowed for the fabrication of advanced immunosensors with signal amphfi-cation by means of redox cycling, which has been a success story of its own. This detection scheme has been used in immunosensors and other biosensors and has stimulated significant developments in electrode fabrication. Instrumental electroanalysis, namely capacitance measurements and EIS allow for label-free detection of immunoreactions. 

Gobi, K.V., Iwasaka, H., and Miura, N. (2007) Self-assembled PEG monolayer based SPR immunosensor for label-free detection of insulin. Biosensors S. Bioelectronics, 22, 1382-1389. 

Pacholski C, Yu C, Miskelly GM, Godin D, Sailor MJ (2006) Reflective interferometric Fourier transform spectroscopy a self-compensating label-free immunosensor using doublelayers of porous Si02. J Am Chem Soc 128 4250-4252... 

Direct capture assays are the most common format used in piezoelectric immunosensors. Primarily, because its simplistic format exploits the label-free advantages of piezoelectric transducers. 

SPR is a representative physical phenomenon that is widely utilized for label-free characterization of molecules on thin metal films. The basic principle and operation of SPR has been described in more detail in several review articles [77, 78]. The reports on SPR-based immune sensors have steeply increased for detection of analytes with low molecular weights in recent years. SPR detection in microfluidic systems can provide various advantages. Immunoreactions are completed within a short time due to small sample volumes down to the nanolitre scale. Kim et al. developed a simple and versatile miniaturized SPR immunosensor enabling parallel analyses of multiple analytes [79]. Their SPR sensor was claimed to exhibit good stability and reusability for 40 cycles and more than 35 days. Feltis et al. demonstrated a low-cost handheld SPR-based immunosensor for the toxin Ricin [80]. Springer et al. reported a dispersion-free microfluidic system with a four-channel SPR sensor platform, which considerably improved the response time and sensitivity [81]. The sensor was able to detect short sequences of nucleic acids down to a femtomole level for 4 min. Waswa et al. demonstrated the immunological detection of E. coli 0157 H7 in milk, apple juice, and meat juice extracted from... 

Isoproturon Label-free immunosensor using reflectometric interference spectroscopy 0.7pgl-> water [148]... 

Okuno, 1., Maehashi, K., Kerman, K., Takamura, Y., Matsumoto, K., Tamiya, E. (2007b). Label-free immunosensor for pro state-specific antigen based on single-walled carbon nanotube array-modified microelectrodes. Biosens Bioelectron 22, 2377-2381. 

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