A biophotoelectrode based on boronic acid-modified Chlorella vulgaris cells integrated within a redox polymer.

Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm-2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices.

Screen-printed microsystems for the ultrasensitive electrochemical detection of alkaline phosphatase.

Screen printing technique has been used to manufacture a microsystem where the graphite-based electrodes hold both a functional and an architectural task. The thick film manufacturing technique has proved valid to develop a very low volume (ca. 20 microL) device where different electrochemical operations can be very efficiently performed. Biomolecule immobilisation within the microsystem for biosensors applications has been explored by inducing and optimizing the in situ generation of a potential pulse polypyrrole electropolymerised film entrapping either glucose oxidase or glucose dehydrogenase. This biomodified microsystem was applied to the ultrasensitive electrochemical detection of alkaline phosphatase yielding limits of detection below 10(-12) M for glucose oxidase and of 10(-15) M for glucose dehydrogenase modified systems, within 15 min of incubation time. The results obtained showed the advantages of using low volume microsystems in combination with an optimised polypyrrole-enzyme film, which displayed a good immobilisation efficiency in conjunction with a good diffusion of species through. Ultrasensitive detection of AP in combination with a stable and reproducible surface modification for entrapping of biomolecules opens the window for new electrochemical detection platform with great potential for integrated biosensor applications.

Microfluorimeter with disposable polymer chip for detection of coeliac disease toxic gliadin.

Coeliac disease is an inflammatory disease of the upper small intestine and results from gluten ingestion in genetically susceptible individuals, and is the only life-long nutrient-induced enteropathy. The only treatment is a strict gluten-free diet and the longer the individual fails to adhere to this diet, the greater the chance of developing malnutrition and other complications. The existence of reliable gluten free food is crucial to the well-being of the population. Here we report on a microfluorimeter device for the in situ detection of gliadin in foodstuffs, which could be used for a rapid control of raw materials in food processing, as well as for process control of gliadin contamination. The microfluorimeter is based on a reflector that is used inside a microfluidic chip, exploiting various strategically placed reflective or totally metallised mirrors for efficient collection of the fluorescent light emitted in a large solid angle. The chip is capable of executing five assays in parallel and has been demonstrated to possess detection sensitivity applicable to fluoroimmunoassays. Various immunoassay formats exploiting fluorescence detection, using enzyme/fluorophore labels were developed and compared in terms of sensitivity, ease of assay, assay time and compatibility with buffer used to extract gliadin from raw and cooked foodstuffs, with the best performance observed with an indirect competition assay using a fluorophore-labelled anti-mouse antibody. This assay was exploited within the microfluorimeter device, and a very low detection limit of 4.1 ng/mL was obtained. The system was observed to be highly reproducible, with an RSD of 5.9%, for a concentration of 50 ng/mL of gliadin applied to each of the five channels of the microfluorimeter. Biofunctionalised disposable strips incorporated into the microfluorimeter were subjected to accelerated Arrhenius thermal stability studies and it was demonstrated that strips pre-coated with gliadin could be stored for approximately 2 years at 4 degrees C, with no discernable loss in sensitivity or detectability of the assay. Finally, the microfluorimeter was applied to the analysis of commercial gluten-free food samples, and an excellent correlation with routine ELISA measurements was obtained. The developed microfluorimeter should find widespread application for on-site execution of fluoroimmunoassays.