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Thursday, 26 July 2012

ICN researchers and colleagues create new cancer cell assay

Reporting in Nano Letters, ICREA Research Professor and ICN Group Leader Arben Merkoci, UAB Group Leader Dr Carme Nogues, and colleagues describe a new method to quantify circulating tumour cells.

The assay is based on tandem use of antibody-coated magnetic beads, which selectively bind to the cancer cells for subsequent magnetic isolation, and antibody-coated gold nanoparticles, to selectively bind to the cancer cells for subsequent electrochemical detection.

A team of researchers from the Nanobioelectronics and Biosensors Group at ICN, led by ICREA and UAB Professor Arben Merkoci, and the group of Dr Carme Nogues, at UAB, have developed a new assay for quantifying circulating tumour cells (CTCs) that is based on tandem use of antibody-coated magnetic beads and antibody-coated gold nanoparticles. Their assay is cheaper, faster, easier to use and more accurate than most existing methods to detect CTCs, and is highly amenable to incorporation in lab-on-a-chip devices. The team has just published their work in Nano Letters.The crux of the new assay is simultaneous use of two types of antibody-coated particles to selectively bind to the tumour cells in a mixed sample: magnetic beads coated with antibodies specific to the known solid-carcinoma marker epithelial cell adhesion molecule (EpCAM), to enable magnetic isolation of the tumour cells from other types of cell; and gold nanoparticles coated with antibodies specific to another well-known tumour marker, carcinoembryonic antigen (CEA), for subsequent electrochemical detection of the isolated cancer cells. As a model tumour cell, Prof Merkoci, Dr Nogues and their colleagues employed the human colon adenocarcinoma cell line Caco2. To test for selectivity, they assayed mixtures of Caco2 cells and control cells (THP-1 monocytes).The researchers optimised the assay by exploring several parameters, including the size and amount of the magnetic beads as well as the antibody coupled to each particle type. The labelled tumour cells were characterised by an array of techniques, including flow cytometry, fluorescence microscopy and scanning electron microscopy (SEM). The cells were detected and quantified electrochemically via the hydrogenevolution reaction (HER), enabled through the electrocatalytic properties of the gold nanoparticles. A detection limit of 1.6 x 102 cells was reached.The team believes that this method could be readily adapted to detection of other cancer types through use of the appropriate antibodies, and should prove viable for use in real human samples, which contain multiple cell types as well as proteins and other biomolecules. Ultimately, they aim to incorporate their method into lab-on-a-chip devices to enable simple, fast and low-cost tools for point-of-care diagnosis.The article, “Simple Monitoring of Cancer Cells Using Nanoparticles”, can be accessed here.