We present here a new, label-free, real time and noninvasive method to detect parasites infecting water and quantify their concentration by electrochemical impedance spectroscopy (E.I.S.). As far as we know, it is the first time parasites are directly detected by E.I.S.. This work comes within the scope of world water crisis whose one of main obstacles is parasite infection. As a model for waterborne parasite, cryptosporidium parvum is studied. Sensors consist in interdigitated microelectrodes. It is shown that parasite detection requires low conductive buffer. Impedance spectrums from parasites suspended with various concentrations in purified water are fitted with an electric circuit to extract sample conductance. Sample conductance increases linearly with parasite concentration. This relation shows E.I.S. enables to know parasite concentration and can be used in water treatment process. A new method to achieve total diagnosis by identifying dead and living parasites is also presented.

Nanoscale probes have been developed for the online characterization of the electrical properties of biological cells by dielectric spectroscopy. Two types of sensors have been designed and fabricated. The first one is devoted to low ( 10 MHz) frequency range analysis and consists of gold nanoelectrodes. The second one works for high (> 40 Hz) frequency range analysis and consists of a gold nanowire. The patterning of the sensors is performed by electron beam lithography. These devices are integrated in a microfluidic channel network for the manipulation of the cells and for the improvement of the performances of the sensors. These devices are used for the analysis of a well-characterized biological model in the area of the ligand - receptor interaction. The purpose is to monitor the interaction between the lactoferrin (the ligand) and the nucleolin and sulfated proteoglycans (the receptors) present or not on a set of mutant Chinese hamster ovary cell lines and their following internalization into the cytoplasm. Initial measurements have been performed with this microsystem and they demonstrate its capability for label-free, real-time, analysis of a dynamic mechanism involving biological cells.

The integration of semiporous membranes into poly(dimethylsiloxane) (PDMS) microfluidic devices is useful for mass transport control. Several methods such as plasma oxidation and manual application of PDMS prepolymer exist to sandwich such membranes into simple channel structures, but these methods are difficult to implement with reliable sealing and no leakage or clogging for devices with intricate channel features. This paper describes a simple but robust strategy to bond semiporous polyester and polycarbonate membranes between layers of PDMS microchannel structures effectively without channel clogging. A thin layer of PDMS prepolymer, spin-coated on a glass slide, is transferred to PDMS substrates with channel features as well as to the edges of the semiporous membrane by stamping. This thin PDMS prepolymer serves as "mortar" to strongly bond the two PDMS layers and seal off the crevices generated from the thickness of the membranes. This bonding method enabled the fabrication of an 8 x 12 criss-crossing microfluidic channel array with 96 combinations of fluid interactions. The capability of this device for bioanalysis was demonstrated by measuring responses of cells to different color fluorescent reagents.