Optical PMMA chip for multianalyte detection F. Baldini ∗a , A. Carloni a , R. Falciai a , A. Giannetti a , A. Mencaglia a , G. Porro b , C. Trono a a Institute of Applied Physics, CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy b Datamed S.r.L., Via Papa Giovanni XXIII 45, 20090 RODANO (MI) Italy ABSTRACT In the present work an optical platform is described for the interrogation of a multichannel array for chemical and biochemical parameters. A fluorescent sensing layer is immobilised on the internal wall of the channel and the emitted light travels along the thickness of the channel and is detected with an optical fibre connected with a spectrum analyzer. Keywords: optical sensor, multichannel array, PMMA chip, fluorescence anisotropy, pH 1. INTRODUCTION Optical biochips can be considered an array of individual biosensors that can be individually monitored and generally are used for the analysis of multiple analytes 1 . They are generally designed for biomedical or environmental analysis. Because of their miniaturization, low cost, and potential for large-scale automation, they can perform analysis more efficiently than currently available laboratory equipment. a distinction can be made between label-free system 2-4 , in which the interaction analyte/sensitive layer gives rise to a modification of the optical signal due to the change of the refractive index of the layer deposited on the substrate, and label-based system 5-8 , in which fluorescent labelling is used to get an optical signal depending on the investigated analyte. Both these methods present advantages and disadvantages. Direct optical detection can boast the capability of analysis without the labels application; in fact fluorescence-based biosensors require either multi-step detection protocols or delicately balanced affinities of interacting biomolecules for displacement assays, causing sensor cross-sensitivity to non-target analytes. However, for monitoring complex samples, the label-free methods continue to be susceptible to problems such as low sensitivity and increased backgrounds due to non-specific binding. The five-year integrated project “healthCARE by biosensor Measurements And Networking” (CARE-MAN) has the aim to develop an intelligent and fully automated optcal diagnostic device on a modular technological system. It will combine successful transduction principles, biochemical recognition methods and communication capabilities to allow a multi parameter measurement characterising diseases defined by doctors and needs in hospitals. In the present work a multichannel array for chemical and biochemical parameters, which has to be part of the modular part of the diagnostic device, is described. It consists of a plastic chip formed by two pieces of polymethylmethacrylate (PMMA) opportunely shaped in order to obtain several flow channels. Light from a laser or a LED is used to excite the fluorescent sensing layer immobilized on the internal wall of the channel. The emitted light travels along the thickness of the channel and is detected with an optical fibre connected with a photodetector. Preliminary tests were carried out immobilising a pH indicator, fluorescein, in the PMMA channel and evaluating the optical efficiency of the system. 2. EXPERIMENTAL SETUP The first prototype of the flow cell consists of four channels obtained by combining two PMMA pieces: a lower piece which includes the four micro-channels and the inlet and outlet for the fluidic, and a cover, where the fluorophore was immobilized. The dimensions of a single flow-channel are: 0.5 mm in width, 0.4 mm in height and 18 mm in length. The longitudinal cross section of the flow cell is reported in Figure 1a and the cross section related to two channels is reported in Figure 1b. A photo of the first prototype realized is shown in Figure 2. The fluorophore immobilized on bottom surface of the cover is in contact with the fluid under investigation. The excitation radiation travels transversally ∗ f.baldini@ifac.cnr.it; phone +39-055-5226323; fax +39-055-5226400; ifac.cnr.it