Biosensors and Bioelectronics 26 (2010) 1701–1705 Contents lists available at ScienceDirect Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios Short communication Versatile label free biochip for the detection of circulating tumor cells from peripheral blood in cancer patients Swee Jin Tan a,b , Rumkumar Lalitha Lakshmi c , Pengfei Chen c , Wan-Teck Lim d , Levent Yobas b,e , Chwee Teck Lim a,c,f,∗ a NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, 12 Medical Drive, Singapore 117598, Singapore b Institute of Microelectronics, A*STAR (Agency for Science, Technology and Research), 11 Science Park Road, Singapore 117685, Singapore c Division of Bioengineering and Department of Mechanical Engineering, 9 Engineering Drive 1, Singapore 117576, Singapore d Department of Medical Oncology, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610, Singapore e Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Kowloon, Hong Kong f Mechanobiology Institute, T-Lab 5A Engineering Drive 1, Singapore article info Article history: Received 14 April 2010 Received in revised form 6 July 2010 Accepted 15 July 2010 Available online 22 July 2010 Keywords: Circulating tumor cells (CTCs) Microfluidics Cancer cell isolation Physical separation Cell mechanical properties abstract The isolation of circulating tumor cells (CTCs) using microfluidics is attractive as the flow conditions can be accurately manipulated to achieve an efficient separation. CTCs are rare events within the peripheral blood of metastatic cancer patients which makes them hard to detect. The presence of CTCs is likely to indicate the severity of the disease and increasing evidences show its use for prognostic and treatment monitoring purposes. We demonstrated an effective separation using a microfluidic device to utilize the unique differences in size and deformability of cancer cells to blood cells. Using physical structures placed in the path of blood specimens in a microchannel, CTCs which are generally larger and stiffer are retained while most blood constituents are removed. The placements of the structures are optimized by computational analysis to enhance the isolation efficiency. With blood specimens from metastatic lung cancer patients, we confirmed the successful detection of CTCs. The operations for processing blood are straightforward and permit multiplexing of the microdevices to concurrently work with different sam- ples. The microfluidic device is optically transparent which makes it simple to be integrated to existing laboratory microscopes and immunofluorescence staining can be done in situ to distinguish cancer cells from hematopoietic cells. This also minimizes the use of expensive staining reagents, given the small size of the microdevice. Identification of CTCs will aid in the detection of malignancy and disease stage as well as understanding the phenotypic and genotypic expressions of cancer cells. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Cancer is a leading cause of death, and in most cases, cancer deaths are the result of metastasis (Steeg, 2006) with malignant cancer cells spreading to distant sites. The lack of early warning at initial stages of the disease limits the effectiveness for cancer treatment (Chambers et al., 2002). Circulating tumor cells (CTCs) are disseminated from solid tumors that enter the blood circula- tion during hematogenous metastasis (Poste and Fidler, 1980) and recent clinical studies show that the quantity of CTCs in circulation is a good measure for prognosis and overall survival (de Bono et al., 2008; Pantel and Riethdorf, 2009; Slade and Coombes, 2007). It is also reported to have association to disease progression (Cohen et ∗ Corresponding author at: Nano Biomechanics Laboratory, Division of Bio- engineering, National University of Singapore, 2 Engineering Drive 3, E3-05-16, Singapore 117576, Singapore. Tel.: +65 6516 7801; fax: +65 6773 2205. E-mail address: ctlim@nus.edu.sg (C.T. Lim). al., 2009; Cristofanilli et al., 2004) and treatment efficacy (Reuben et al., 2008; Urtishak et al., 2008). Hence, the blood specimens of cancer patients are a potential source of tumor cells. Furthermore, blood extraction is routinely performed for various health tests and also less invasive compared to surgical biopsies. The availability of blood samples is attractive for CTC enumeration to complement current techniques in the detection and monitoring of cancer. The technical challenge to detect CTCs in peripheral blood lies in the rarity of these cells (Zieglschmid et al., 2005). The cell count can be as low as 1 cancer cell to 1 ml of blood which contains approxi- mately 4.8–5.4 billion erythrocytes; 7.4 million leukocytes and 280 million thrombocytes (Fournier, 1998). Leading technologies in CTC enrichment from blood specimen uses affinity based techniques which employ antibodies that are expressed only on cancer cells (Cohen et al., 2008; Riethdorf et al., 2007). These methods face var- ious drawbacks such as the need for pre-sample preparation and more importantly the specificity of the antibody selected for enrich- ment. Additional preparatory steps are likely to incur CTC losses while the lack of a universal biomarker for CTC enrichment limits 0956-5663/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2010.07.054