Carbon Nanotube Amplification Strategies for Highly Sensitive Immunodetection of Cancer Biomarkers

We describe the combination of electrochemical immunosensors using single-wall carbon nanotube forest platforms with multi-label secondary antibody-nanotube bioconjugates for highly sensitive detection of a cancer biomarker in serum and tissue lysates

Xin Yu; Bernard Munge; Vyomesh Patel; Gary Jensen; Ashwin Bhirde; Joseph D. Gong; Sang N. Kim; John Gillespie; J. Silvio Gutkind; Fotios Papadimitrakopoulos; James F. Rusling


Scholarcy highlights

  • prostate specific antigen in human serum was measured with single-wall carbon nanotube immunosensors with ±5% accuracy for human serum samples compared to a referee ELISA method
  • The best sensitivity is obtained using the Ab2-CNTHRP bioconjugates with high enzyme label/ Ab2 ratios for signal amplification
  • nonspecific binding was effectively controlled by using bovine serum albumin and Tween-20 in blocking buffers, providing sensitivity to PSA at concentrations as low as 4 pg mL−1 in only 10 μL of undiluted calf serum, which contains ∼1010 times more unrelated protein than the cancer biomarker being detected
  • SWNT immunosensors were capable of sensitive quantitative measurement of PSA in 1000 prostate cancer cells, in tissue samples that cannot be distinguished from one another with the best immunostaining methodologies
  • Good accuracy was demonstrated by excellent correlation of SWNT immunosensor results obtained in two different ways for PSA in human serum samples with standard ELISA results on the same samples
  • PSA in human serum was measured with SWNT immunosensors with ±5% accuracy for human serum samples compared to a referee ELISA method
  • The high sensitivity of the SWNT immunosensors using the Ab2-carbon nanotubes-horseradish peroxidase bioconjugates relies upon three types of amplification: the labeling protocol allows several hundred labels per binding event provided by using Ab2-CNT-HRP bioconju-gates in place of conventional Ab2-HRP; SWNT forest properties including excellent conductivity and high surface area that provides a high density of primary antibodies, and the catalytic nature of the enzyme label, in which HRP is activated by hydrogen peroxide to a ferryloxy form of the enzyme that is electrochemically reduced in a catalytic cycle
  • We have demonstrated highly sensitive and selective electrochemical detection of a protein cancer biomarker with single-wall carbon nanotube immunosensors, as exemplified by the measurement of prostate specific antigen in complex biomedical samples such as human serum and tissue lysates

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