A cell-on-paper system for the study of secretion

A simple and generally applicable system was designed to detect and quantify electroactive molecules released from cells grown on paper

Cathodic pretreatment improves the resistance of boron-doped diamond electrodes to dopamine fouling

The resistance of cathodically and anodically treated boron-doped diamond electrodes to dopamine fouling was investigated. It was found, using cyclic voltammetry and electrochemical impedance spectroscopy, that the cathodic preparation offers an increased resistance to fouling, in addition to an enhanced electrochemical response

Nanocalorimetric platform for accurate thermochemical studies in microliter volumes

A straightforward and general way for monitoring chemical reactions is via their thermal signature. Such approach requires however an experimental setup with a high thermal stability that simultaneously allows time-resolved heat detection with high sensitivity. We present a nanocalorimetric platform for accurate thermochemical studies of (bio-)chemical reactions in a miniaturized format (tens of microliter volume), characterized by a fast thermalization time to a preset temperature (<30 minutes), an excellent base temperature stability (±1 mK) and a fast sensing response time (few seconds). The platform is built around a commercial thermopile-based sensor chip, on which an open-well reservoir holding the sample is directly positioned. The sample is, prior to the experiment, pipetted into the reservoir, in which small aliquots of reagents are injected subsequently and sequentially via thermalized microfluidic conducts. The design of the platform is optimized by means of numerical simulations. Via thermoelectric calibration using a resistive heater positioned either on the sensor chip or in the reservoir, we obtain a maximum power sensitivity of 2.7 V W−1 and a heat limit of detection of 70 nW. The excellent functionality of the platform is demonstrated by measuring the reaction enthalpy of 1-propanol in water and the rate constant k and enthalpy change of the oxidation reaction of glucose catalyzed by glucose oxidase, showing good agreement with literature data. Our versatile platform may be applied to many thermochemical studies, including thermodynamic analysis and kinetic reaction analysis, and its ease of use will allow implementation of many different experimental protocols

Study of constrained Brownian motion of nanoparticles near an interface using optical tweezers

We demonstrate a method to determine the Brownian motion and the diffusion coefficient of a nanoparticle in water in a plane that is parallel to a solid boundary and as function of the distance normal to that boundary by using an optical tweezers instrument. A solution of 190 nm-diameter fluorescent polystyrene nanoparticles in de-ionized (DI) water is introduced in a micro-chamber built from two thin glass substrates. A single particle is trapped by the tweezers and optically moved in the z-direction normal to a substrate. By analyzing a scatter plot of the time-dependent positions of the nanoparticle in the x-y plane in a histogram, the diffusion coefficient parallel to the substrate of the Brownian particle constrained by the substrate is determined as a function of the distance between the substrate and the nanoparticle. The experimental results indicate the increased drag effect on the nanoparticle when it is close to the substrate, as evidenced by an experimental diffusion coefficient nearby the substrate that is about half of that of the particle in the bulk fluid

FLUORESCENCE IN SITU HYBRIDIZATION (FISH) ENHANCEMENT USING MICROFLUIDIC FLOW FOR AN ACCURATE, FAST AND ECONOMICAL ASSESSMENT OF HER2 STATUS IN BREAST CANCER

The fluorescence in situ hybridization (FISH) is the gold standard in human epidermal growth factor receptor 2 (HER2) status assessment in breast cancer. The dissemination of the technique is impeded by the cost of reagents and long experimental time. For overcoming these limitations, we have developed a new method for implementing FISH for HER2 assessment for tissue analysis based on microfluidic technology

Extra short incubation microfluidic assisted – fluorescence in situ hybridization (ESIMA-FISH)

Fluorescence in situ hybridization (FISH) is a powerful technique for evaluating the HER2 gene status in breast cancer specimen (1). However, most of FISH assays currently used in clinical laboratories are expensive and require long experimental time, up to two days with an overnight incubation (2). Indeed, despite the development of faster FISH probes (HER2 IQFISH pharmDxTM from DAKO, Denmark) cutting the assay time to one day (3), the cost of these new probes is still high (more than 200$/test) and impedes the dissemination of this technique. In this study, we present the extra short incubation microfluidic assisted- fluorescence in situ hybridization (ESIMA-FISH) technique that uses microfluidics to improve FISH for HER2 assessment in breast cancer samples. ESIMA-FISH requires a very short incubation time (35 minutes) and uses 4-fold less probe solution per test. The system is based on a microfluidic chip, developed in our laboratory (4), that is clamped against a microscope slide containing a breast cancer tissue specimen (figure 1). A fluorescent DNA probe solution, specific to the target DNA, is then applied to the tissue section within a thin chamber using the microfluidic system. The probe solution used is obtained by diluting 4 times the standard HER2 IQFISH pharmDxTM probe solution (DAKO, Denmark). Oscillating flows can then be implemented using syringe pumps to improve the delivery of the probe to the tissue. Thanks to this hydrodynamic enhancement of mass transport, the probe-target hybridization efficiency is increased, resulting in overall reductions in the cost and duration of the assay. To validate the ESIMA-FISH technique, several tissue specimens were blindly tested with ESIMA-FISH and standard IQFISH. The results from these two techniques were comparable (figure 2, 3), supporting the possibility of a future clinical use of ESIMA-FISH

Delayed voltammetric with respect to amperometric electrochemical detection of concentration changes in microchannels

The time response of an electrode incorporated into a fluidic channel to variations in analyte concentration of the outer-sphere redox probe ferrocenemethanol was investigated both for amperometry (AMP) and cyclic voltammetry (CV). The experimental data show that the temporal resolution of CV is not as good as that of AMP, as CV cannot properly detect fast concentration transients. The delayed response of CV was previously reported, for neurotransmitters, and mostly attributed to the adsorption of the analyte on the electrode surface. By using an outer-sphere redox couple, we show that mass transport also significantly delays the response of CV. The experimental delay time in CV was understood from mass transfer limitations due to the relaxation of the diffusion layer during repeated potential scanning. Furthermore, a robust protocol for the analysis of fast concentration transients was established, using the impulse and modulation transfer functions of the system. This method was found to be more precise than the mere analysis of undifferentiated traces in the time domain. As a proof of concept, the effect of increased viscosity was investigated, showing that AMP was more sensitive than CV to these variations. Overall, this analysis underlines further the enhanced temporal sensitivity of AMP over CV, at the expense of decreased chemical resolution, potentially having implications for in situ electrochemical detection of biologically relevant molecules