Detection of leukemia with carbon nanotubes

5 Oct 2014. NUS scientists have demonstrated an ultrasensitive electrochemical nucleic acid assay amplified by carbon nanotubes-based labels for the detection of leukemia oncogene.

A team led by Prof LIM Tit Meng from Department of Biological Sciences in NUS has demonstrated a novel electrochemical assay for simple, sensitive, accurate and quantitative detection of genetic marker in mRNA without RT and PCR amplification. Their method showed a 10³–fold improvement in assay sensitivity, which enables the direct detection of a full-length gene marker for leukemia (blood cancer) at extreme low levels from as little as nanograms of total mRNA population. The electrochemical responses were unambiguously resolved for less than 2-fold difference in gene expression level. The high specificity of the assay successfully discriminated the perfect match targets from a 3-base mismatch sequence and the non-complementary sequences present as pure oligonucleotides or mRNA population extracted from negative cell lines.

The electrochemical analysis using their method is consistently comparable to the chemiluminescent detection and can be readily integrated for the development of point-of-care (POC) systems.His team approach has addressed the shortcomings of the RQ-PCR evidenced by the reduced assay complexity and minimization of assay bias caused by non-ideal RT efficiency. The developed assay could therefore provide new insights if use for clinical disease diagnostic tests.The proposed approach that utilized HRP-tagged CNT-based labels can also be  adapted readily by fluorescent and luminescent methods.

His team has also discovered a novel function of a nuclear protein called nucleophosmin (NPM). It can inhibit caspase-6 and caspase-8 and its mutation is linked to cancer formation, such as found in acute leukemia. They study the protein NPM so as to better understand its role in cell death regulation, cell differentiation and cell division. They have discovered that the mutant form of NPM is overly localized in the cell cytoplasm, as a result it not only prevents cell death from happening when they are due to die, it also inhibits proper blood cell differentiation, thus making acute myeloid leukemia (a form of blood cancer) a severe disease.

Schematic illustration of the branched DNA (bDNA)-amplified electrochemical detection and quantitation of mRNA fusion transcript. [Image credit: LEE Ai Cheng]

References

1. A C, Z Dai, B Chen, H Wu, J Wang, A Zhang, L Zhang, T M Lim, Y Lin. “Electrochemical Branched‑DNA Assay for Polymerase Chain Reaction‑Free Detection and Quantification of Oncogenes in Messenger RNA”. Analytic Chemistry 80 No. 24 (2008) 9402.

2. Leong, S M, B X Tan, B A Baidah, T Yan, LY Chee, S T ANG, K G TAY, LP Koh, Yeoh EJ, E S C Koay, HYK Mok, TM Lim. “Mutant nucleophosmin deregulates cell death and myeloid differentiation through excessive Caspase‑6 and ‑8 inhibition.” Blood 116 (2010) 3286.