Immunosensors amperometric detection

Figure 3.25 Scheme of a SWNT immunosensor using secondary antibody labeled with HRP enzyme. HRP catalyses H2O2 and generates electrons that can be amperometrically detected, (a) Treatment with a conventional HRP-labeled secondary antibody providing one label per binding event and (b) treatment with an HRP-... 

Figure 26.3 presents the resulting calibration curve of the HRP-immunosensor for the amperometric detection of anti-CT. The values of the detection limit obtained (50 ng/ml) are similar to those obtained with optical fiber immunosensors, based on HRP-labeled secondary antibodies (160 ng/ml) [5-8]. 

Electroenzymatic performances of HRP, GOX-B and PPO-B-immunosensors towards the amperometric detection of anti-CT... 

Baumner, AJ. and R.D. Schmid (1998). Development of a new immunosensor for pesticide detection a disposable system with liposome-enhancement and amperometric detection. Biosens. Bioelectron., 13 519-529. 

Pinacho, D.G., F. Sanchez-Baeza, M.P. Marco, et al. 2009. Development of an amperometric magneto immunosensor for detection of fluoroquinolone antibiotics. J. Agric. Food Chem. submitted. 

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. 

Vetcha S., Abdel-Hamid I., Atanasov R, Ivnitski D., Wilkins E., and Hjelle B., Portable immunosensor for the fast amperometric detection of anti-Hantavirus antibodies, Electroanalysis, 12, 1034-1038, 2000. 

Other researchers have followed related strategies as described above for detection of IL-6. For example, Wang et. al. [75] reported an amperometric immunosensor to detect interleukin-6 (lL-6) using a AuNP-Poly-dopamine sensor platform and multienzyme-antibody functionalized AuNPs on carbon nanotubes. They obtained a DL of 1 pg mL for lL-6 in buffer. Du et. al. [76] used AuNP-modified screen printed carbon electrode to detect p53 phosphorylated at Ser392 (phospho-p53 ) along with multi-enzyme labeled graphene oxide (GO). 

Sharma, M.K., et al. Highly sensitive amperometric immunosensor for detection of Plasmodium falciparum histidine-rich protein 2 in serum of humans with malaria comparison with a commercial kit. J. Clin. Microbiol. 46(11), 3759 (2008)... 

MPCs functionalized with large biomolecules including proteins, enzymes, and antibodies (immunosensors) are also abundant in the literature. A Ti02 nanotube array was decorated with antibody-labeled Au MPCs to allow for binding with a target analyte and amperometric detection. Typically, sensors must achieve detection limits of at least ng mL" to be a viable sensing platform for low-abundance proteins, and this sensor could lead to detection limits as low was 0.01 ng mL". Similar to the vast improvement in sensitivity for the chemiresistor that IDA electrodes made, miniaturization of electrodes into high aspect ratio arrays for this sensor led to enhanced electrochemical detection in comparison to flat electrode surfaces by 10-fold. ... 

A similar study has also been conducted to determine the suitability of ascorbic acid 2-phosphate (AAP) as an alternative substrate to 4-AP for AP under identical conditions [48], Although 4-APP and AAP were suitable substrates for amperometric immunosensors, 4-APP was superior owing to its sixfold faster enzymatic reaction and lower detection potential (approximately 200-400mV). Notably, the lower detection potential for the hydrolysis product of 4-APP minimizes interferences from other species and hence improves the sensitivity of the immunosensor. 

C. Singh, G.S. Agarwal, G.P. Rai, L. Singh, and V.K. Rao, Specific detection of Salmonella typhi using renewable amperometric immunosensor. Electroanalysis 17, 2062-2067 (2005). 

H.S. Jung, J.M. Kim, J.W. Park, H.Y. Lee, and T. Kawai, Amperometric immunosensor for direct detection based upon functional lipid vesicles immobilized on nanowell array electrode. Langmuir 21, 6025-6029 (2005). 

---