Development of an opto-microfluidic flow cytometer for the sorting of stem cells from blood samples Md. Z. Islam *a , Xuantao Su a , Sean E. Kirkwood a , Kirat Singh a , James N. McMullin a , Wojciech Rozmus b , Anna Janowska-Wieczorek c , and Ying Y. Tsui a a Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB b Department of Physics, University of Alberta, Edmonton, AB c Department of Medicine, University of Alberta & Canadian Blood Services, Edmonton, AB ABSTRACT In this paper, we report the preliminary development of a fiber coupled microfluidic flow cytometer with its potential application of sorting the very small embryonic like (VSEL) stem cells out of a mixture of platelets and VSEL stem cells. The identification of a VSEL stem cell from a platelet is based on the large difference of their abilities to scatter light. A simple cytometer prototype was built by cutting the fluidic and other channels into a polymer sheet and bonding it with epoxy between two standard glass slides. Standard photolithography was used to expose an observation window over the upper coated glass to reduce background scattered light. Liquid sample containing micro-particles (such as cells) is injected into the microfluidic channel. Light from a 532-nm CW diode laser is coupled into the optical fiber that delivers the light to the detection region in the channel to interrogate the flowing-by micro-particles. The scattering light from the interrogated micro-particle is collected by a photodiode placed over the observation window. The device sorts the micro-particle into the sort or waste outlet depending on the level of the photodiode signal. We used fluorescent latex beads to test the detection and sorting functionalities of the device. It was found that the system could only detect about half of the beads but could sort almost all the beads it detected. Keywords: Microfluidic flow cytometer, stem cell sorting 1. INTRODUCTION Cytometry is a set of methods that allows us to quantitatively or semi-quantitatively examine the physiochemical and morphological characteristics of biological cells. Flow cytometry is a kind of cytometry in which counting, examining and sorting of cells or microscopic particles suspended in a stream of fluid are carried out. They are routinely used in clinical settings for everything from simple blood counts to the study of proteomics, genomics and the monitoring of HIV patients [1-4]. They are also used in biological labs for cellomics and in different biochemical industries for determining the content of micro-particles, e.g. bacteria [5, 6]. In flow cytometry, cells or micro-particles are arranged to flow sequentially through a monochromatic incident light beam in a sensing region and some characteristic parameters of the sample, for example, scattered light and/or fluorescence property, are measured to get information about the cells or particles of interest [7]. As flow cytometers became commercially available they began to increase in complexity, employing multiple lasers and detectors to meet requirements for multicolor fluorescence analyses. This has led to the growing interest toward miniaturized flow cytometer research. The development of miniaturized microfluidic flow cytometers offers the potential for disposable assays, cost and size reductions and portable point-of-care diagnostics [7]. A variety of microfluidic flow cytometers have been reported in the literature, as reviewed in [8] and [9]. In this paper, we describe a simple flow cytometer/cell- sorter. *mzislam@ualberta.ca; phone 1 780 492-3905; fax 1 780 492-1811; www.ece.ualberta.ca/~mzislam Photonics North 2009, edited by Réal Vallée, Proc. of SPIE Vol. 7386, 73860C © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.839802 Proc. of SPIE Vol. 7386 73860C-1