Nanomonitor: A Miniature Electronic Biosensor for Glycan Biomarker Detection

Abstract

Aim: The goal of our research is to develop an ultrasensitive diagnostic platform called ‘NanoMonitor’ to enable rapid label-free analysis of a highly promising class of biomarkers called glycans (oligosaccharide chains attached to proteins) with high sensitivity and selectivity. The glycosylation of fetuin – a serum protein – and extracts from a human pancreatic cancer line was analyzed to demonstrate the capabilities of the NanoMonitor. Material & methods: The NanoMonitor device consists of a silicon chip with an array of gold electrodes forming multiple sensor sites and works on the principle of electrochemical impedance spectroscopy. Each sensor site is overlaid with a nanoporous alumina membrane that forms a high density of nanowells on top of each electrode. Lectins (proteins that bind to and recognize specific glycan structures) are conjugated to the surface of the electrode. When specific glycans from a test sample bind to lectins at the base of each nanowell, a perturbation of electrical double-layer occurs, which results in a change in the impedance. Using the lectins Sambucs nigra agglutinin (SNA) and Maackia amurensis agglutinin (MAA), subtle variations to the glycan chains of fetuin were investigated. Protein extracts from BXPC-3, a cultured human pancreatic cancer cell line were also analyzed for binding to SNA and MAA lectins. The performance of the NanoMonitor was compared to a conventional laboratory technique: lectin-based enzyme linked immunosorbent assay (ELISA). Results & discussion: The NanoMonitor was used to identify glycoform variants of fetuin and global differences in glycosylation of protein extracts from cultured human pancreatic cancerous versus normal cells. While results from NanoMonitor correlate very well with results from lectin-based ELISA, the NanoMonitor is rapid, completely label free, requires just 10 µl of sample, is approximately five orders of magnitude more sensitive and highly selective over a broad dynamic range of glycoprotein concentrations. Conclusion: Based on its performance metrics, the NanoMonitor has excellent potential for development as a point-of-care handheld electronic biosensor device for routine detection of glycan biomarkers from clinical samples.

Keywords::

• cancer glycoprofiling
• electrochemical impedance spectroscopy glycoprotein analysis
• glycosensor
• label-free glycosylation analysis
• lectin

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Financial & competing interests disclosure

Financial support from Office of Naval Research, Nanoelectronics and Nanometrology Program N00014–07–1–0457 and The Biodesign Institute at Arizona State University (ASU). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Acknowledgements

Gaurav Chatterjee, Ian William Blong, Jamison Rupnik, Vindhya Kunduru and colleagues at Center for Bioelectronics and Biosensors, The Biodesign Institute at Arizona State University (BB) & Center for Solid State Electronics Research at Arizona State University (CSSER).

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Funding

Financial support from Office of Naval Research, Nanoelectronics and Nanometrology Program N00014–07–1–0457 and The Biodesign Institute at Arizona State University (ASU). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.