A nanocomposite-based biosensor for bovine haptoglobin on a 3D paper-based analytical device

Bovine haptoglobin, recognized as an acute phase protein following tissue injury and inflammation, has been shown to increase during the acute phase response. In this study, a nanocomposite-based, vertical flow, immunochromatographic biosensor was developed for rapid determination of bovine haptoglobin. The detection was performed on a paper-based device by using the competitive immunoreaction between the haptoglobin protein and the anti-haptoglobin antibody on the gold nanoparticle–decorated, multi-walled, carbon nanotube nanocomposite probe. Standard haptoglobin protein was immobilized on the test zone in advance. In the absence of the target haptoglobin in the sample, a strong color would appear in the test zone due to the accumulation of nanocomposite, while the presence of the target may result in weaker color. Quantitative results was obtained by analysis of the color intensity of the test zone. Under optimal conditions, a linear relationship between the decreased color intensity and haptoglobin protein over the range of 0.01 ∼ 0.9 mg/mL was achieved with a limit of detection of 28 μg/mL. The feasibility of the biosensor was further investigated by the detection of haptoglobin in spiked bovine serum, and the performance showed good agreement with the commercial ELISA kit. The proposed paper-based, immunochromatographic competitive detection schematic with combination of nanocomposites is simple, rapid and highly efficient, while no additional excessive washing and separation steps are required. It provides an alternative path for rapid on-farm diagnosis of diseases associated with haptoglobin.