Paper-based microfluidic electro-analytical device (PMED) for magneto-assay automation: Towards generic point-of-care diagnostic devices.

Rapid diagnostic tests (RDTs) for point-of-care (POC) testing of infectious diseases are popular because they are easy to use. However, RDTs have limitations such as low sensitivity and qualitative responses that rely on subjective visual interpretation. Additionally, RDTs are made using paper-bound reagents, which leads to batch-to-batch variability, limited storage stability and detection of only the analytes they were designed for. This work presents the development of a versatile technology, based on short magneto-assays and inexpensive paper-based microfluidic electro-analytical devices (PMEDs). PMEDs were produced locally using low-cost equipment, they were stable at room temperature, easy to use, and provided quantitative and objective results. The devices served to detect alternatively a variety of magneto-assays, granting quantitation of streptavidin-HRP, biotinylated HRP and Pasmodium falciparum lactate dehydrogenase (Pf-LDH) in less than 25 min, using either commercial or customized screen-printed electrodes and measurement equipment. Furthermore, Pf-LDH detection in diluted lysed whole blood displayed a linear response between 3 and 25 ng mL-1, detection and quantification limits ranging between 1 and 3 ng mL-1 and 6-12 ng mL-1, respectively, and provided results that correlated with those of the reference ELISA. In short, this technology is versatile, simple, and highly cost-effective, making it perfect for POC testing.

Fuel cell-powered microfluidic platform for lab-on-a-chip applications: Integration into an autonomous amperometric sensing device.

The present paper reports for the first time the integration of a microfluidic system, electronics modules, amperometric sensor and display, all powered by a single micro direct methanol fuel cell. In addition to activating the electronic circuitry, the integrated power source also acts as a tuneable micropump. The electronics fulfil several functions. First, they regulate the micro fuel cell output power, which off-gas controls the flow rate of different solutions toward an electrochemical sensor through microfluidic channels. Secondly, as the fuel cell powers a three-electrode electrochemical cell, the electronics compare the working electrode output signal with a set reference value. Thirdly, if the concentration measured by the sensor exceeds this threshold value, the electronics switch on an integrated organic display. This integrated approach pushes forward the development of truly autonomous point-of-care devices relying on electrochemical detection.

Impedance biosensing using phages for bacteria detection: generation of dual signals as the clue for in-chip assay confirmation.

In the present work, we compare the use of antibodies (Ab) and phages as bioreceptors for bacteria biosensing by Electrochemical Impedance Spectroscopy (EIS). With this aim, both biocomponents have been immobilised in parallel onto interdigitated gold microelectrodes. The produced surfaces have been characterised by EIS and Fourier Transform Infra-Red (FTIR) Spectroscopy and have been applied to bacteria detection. Compared to immunocapture, detection using phages generates successive dual signals of opposite trend over time, which consist of an initial increase in impedance caused by bacteria capture followed by impedance decrease attributed to phage-induced lysis. Such dual signals can be easily distinguished from those caused by non-specific adsorption and/or crossbinding, which helps to circumvent one of the main drawbacks of reagentless biosensors based in a single target-binding event. The described strategy has generated specific detection of Escherichia coli in the range of 10(4)-10(7) CFU mL(-1) and minimal interference by non-target Lactobacillus. We propose that the utilisation of phages as capture biocomponent for bacteria capture and EIS detection allows in-chip signal confirmation.