Algal fluorescence sensor integrated into a microfluidic chip for water pollutant detection Florent Lef  evre, ab Annie Chalifour, c Luping Yu, d Vamsy Chodavarapu, e Philippe Juneau * c and Ricardo Izquierdo * b Received 14th October 2011, Accepted 12th December 2011 DOI: 10.1039/c2lc20998e We report the first miniaturized fluorescent sensor based on algae, with an organic light emitting diode (OLED) and an organic photodetector (OPD) integrated into a microfluidic chip. The blue emission OLED was used as the excitation source, while a blend of PTB3/PC 61 BM was used for the fabrication of the organic photodetector. Excitation and emission color filters based on acid/base dyes and a metal complex were developed and assembled with the organic optoelectronic components in order to complete the fluorescent detection system. The detection system was then integrated in a microfluidic chip made from (poly)dimethylsiloxane (PDMS). The complete sensor is designed to detect algal fluorescence in the microfluidic chamber. Algal chlorophyll fluorescence enables evaluation of the toxicity of pollutants like herbicides and metals-ions from agricultural run-offs. The entirely organic bioassay here presented allowed detection of the toxic effects of the herbicide Diuron on Chlamydomonas reinhardtii green algae that gave 50% inhibition of the algae photochemistry (EC 50 ) with a concentration as low as 11 nM. Introduction There exists an urgent and great need for a portable system to monitor water quality in both developed and developing coun- tries. Currently, there is no commercial test available to satisfy this demand, as only accredited laboratories can perform such evaluations. Conventional physicochemical techniques like chromatography must be performed by qualified technicians, and require large, bulky and expensive equipment. Therefore, despite their high sensitivity and accuracy, they are inappropriate for monitoring water quality onsite. Whole cell biosensors and bioassays are a good candidate solution to satisfy such demands. 1 They offer portability and significant cost reductions, in addition to performance gains in terms of speed, analytical efficiency, automation and reproducibility. The use of unicellular micro-organisms like algae and bacteria has already proven useful in evaluating water toxicity. 2,3 In this work, we have chosen to use algae because they are very sensitive to stressors, even those found in small concentrations. Because a large number of pollutants are capable of affecting photo- system activity, photosynthesis inhibition is a good, rapid indi- cator of toxic effects. Thus, an algal biosensor would be sensitive enough to detect the presence of small quantities of pollutants, and could serve as an easy and cost efficient way to effectuate a qualitative pre-screen test on-site. Algal bio-test would complement traditional laboratory tests, if needed. Fluorescence is a sensitive and reliable method to measure algal photosynthesis inhibition. 4 Several algal fluorescence bioassays have been developed 5,6 and are commercially avail- able. 7 However, such tests are currently expensive and although technically portable, they still cumbersome and not easily transported for on field use. Recently, several amperometric biosensors have also been developed to detect the presence of pesticides, herbicides and metals. 8,9 These devices overcome the portability issues associated with traditional algal fluorescence detectors. However, they are inferior in terms of sensitivity, 10 which makes them unsuitable when very low concentrations of pollutants need to be detected. Herein, we propose to integrate a fluorescence sensor based on organic optoelectronic components and designed for algal fluo- rescence measurement in order to make a truly portable device capable of measuring global water quality onsite, while retaining the high sensitivity of algal fluorescence tests. To do so, we have integrated three major compatible techniques based on thin film a Department of Chemistry and Biochemistry, Resmiq, NanoQAM, Universit e du Qu ebec  a Montr eal, Montr eal, QC, H3C 3P8, Canada b Department of Computer Science, Resmiq, NanoQAM, Universit e du Qu ebec  a Montr eal, Montr eal, QC, H3C 3P8, Canada. E-mail: izquierdo.ricardo@uqam.ca; Tel: +1 514-987-3000 c Department of Biological Science, TOXEN, Universit e du Qu ebec  a Montr eal, Montr eal, QC, H3C 3P8, Canada. E-mail: juneau.philippe@ uqam.ca; Tel: +1 514-987-3000 d Department of Chemistry and the James Franck Institute, The University of Chicago, 929 E. 57th Street, Chicago, Illinois, 60637, U.S.A e Department of Electrical and Computer Engineering, Resmiq, McGill University, 3480 University St., Room 642, Montr eal, QC, H3A 2A7, Canada This journal is ª The Royal Society of Chemistry 2012 Lab Chip, 2012, 12, 787–793 | 787 Dynamic Article Links C < Lab on a Chip Cite this: Lab Chip, 2012, 12, 787 www.rsc.org/loc PAPER