A microbial sensor platform based on bacterial bioluminescence (luxAB) and green fluorescent protein (gfp) reporters for in situ monitoring of toxicity of wastewater nitrification process dynamics.

To avoid the upset of nitrification process in wastewater treatment plants, monitoring of influent toxic chemicals is essential for stable operation. Toxic chemical compounds can interfere with the biological nitrogen removal, thus affecting plant efficiency and effluent water quality. Here we report the development of fluorescence and bioluminescence bioassays, based on E. coli engineered to contain the promoter region of ammonia oxidation pathway (AmoA1) of Nitrosomonas europaea and a reporter gene (lux or gfp). The fluorescence or bioluminescence signal was measured with newly designed optical devices. The microbial sensors were tested and validated at different concentrations of nitrification-inhibiting compounds such as allylthiourea, phenol, and mercury. The signal decrease was immediate and proportional to inhibitor concentration. The developed bacterial bioassays could detect the inhibition of the nitrification process in wastewater for allylthiourea concentrations of 1 µg/L for E.coli pMosaico-Pamo-gfp and 0.5 µg/L for E.coli pMosaico-Pamo-luxAB. The results were confirmed using water from a wastewater plant, containing nitrification-inhibiting compounds.

Quantum dots functionalised artificial peptides bioinspired to the D1 protein from the Photosystem II of Chlamydomonas reinhardtii for endocrine disruptor optosensing.

Herein we describe the design and synthesis of novel artificial peptides mimicking the plastoquinone binding niche of the D1 protein from the green photosynthetic alga Chlamydomonas reinhardtii, also able to bind herbicides. In particular, molecular dynamics (MD) simulations were performed to model in silico the behaviour of three peptides, D1Pep70-H, D1Pep70-S264K and D1Pep70-S268C, as genetic variants with different affinity towards the photosynthetic herbicide atrazine. Then the photosynthetic peptides were functionalised with quantum dots for the development of a hybrid optosensor for the detection of atrazine, one of the most employed herbicides for weed control in agriculture as well as considered as a putative endocrine disruptor case study. The excellent agreement between computational and experimental results self consistently shows resistance or super-sensitivity toward the atrazine target, with detection limits in the µg/L concentration range, meeting the requirements of E.U. legislation.

ZnO/polyaniline composite based photoluminescence sensor for the determination of acetic acid vapor.

In this study, we report a novel ZnO/polyaniline (PANI) nanocomposite optical gas sensor for the determination of acetic acid at room temperatures. ZnO nanorods, synthesized in powder form were coated by PANI (ZnO/PANI) by chemical polymerization method. The obtained nanocomposites were deposited on glass substrate and dried overnight at room temperature. Structure and optical properties of ZnO/PANI nanocomposite have been studied by using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, diffuse reflectance and photoluminescence spectroscopy. Tests towards acetic acids were performed in the range of concentrations 1-13 ppm. The adsorption of acetic acid on the sensor's surface resulted in the decrease of ZnO/PANI photoluminescence. The response and recovery time of the sensor were in the range of 30-50 s and 5 min, respectively. The developed sensors showed sensitivity towards acetic acid in a range of 1-10 ppm with the limit of detection of 1.2 ppm. Specially designed miniaturized sensing system based on integrated sensing layer, light emission diode as excitation source and optical fiber spectrometer was developed for the measurement of the sensor signal. The developed sensing system was applied for the investigation of some real sample assessment including the evaluation of storage conditions of ancient cellulose acetate films, which during the degradation are releasing acetic acid. The obtained results suggest that the developed novel optical ZnO/PANI nanocompsite based sensor shows great potential for acetic acid determination in various samples.

Fast pesticide pre-screening in marine environment using a green microalgae-based optical bioassay.

The present study evaluates an optical bioassay based on green photosynthetic microalgae as a promising alternative for monitoring of relevant seawater pollutants. Photosystem II fluorescence parameters from several microalgae species were examined in the presence of three common marine pesticides that act as photosynthesis inhibitors. The three pollutants were detected within 10 min in concentrations between ng/L-µg/L. The different algae species showed slightly diverse pesticide sensitivities, being Chlorella mirabilis the most sensitive one. Potential interferences due to oil-spill pollutants were discarded. The lipid content was characterized to identify microorganisms with suitable mechanisms that could facilitate stress acclimatization. C. mirabilis presented elevated content of unsaturated lipids, showing a promising potential for biosensing in saline stress conditions. The optimized microalgae-based bioassay was preliminarily incorporated into a marine buoy for autonomous pre-screening of pesticides in coastal areas, demonstrating its suitability for real-time monitoring of marine water and quantitative evaluation of total biotoxicity.

Better together: Strategies based on magnetic particles and quantum dots for improved biosensing.

Novel technologies and strategies for sensitive detection of biological responses in healthcare, food and environmental monitoring continue to be a priority. The present review focuses on bioassay development based on the simultaneous use of quantum dots and magnetic beads. Due to the outstanding characteristics of both particles for biosensing applications and the large number of publications using a combined approach, we aim to provide a comprehensive overview of the literature on different bioassays, the most recent advances and innovative strategies on the topic, together with an analysis of the main drawbacks encountered and potential solutions offered, with a special emphasis on the requirements that the transfer of technologies from the laboratory to the market will demand for future commercialization of biodevices. Several procedures used in immunoassays and nucleic acid-based bioassays for the detection of pathogens and biomarkers are discussed. The improvement of current approaches together with novel multiplex detection systems and nanomaterials-based research, including the use of multimodal nanoparticles, will contribute to simpler and more sensitive bioanalyses.

Voltammetric determination of epinephrine by White rot fungi (Phanerochaete chrysosporium ME446) cells based microbial biosensor.

The lyophilized biomass of White rot fungi (Phanerochaete chrysosporium ME446) was immobilized in gelatine using glutaraldehyde crosslinking agent on a Pt working electrode. The fungal cells retained their laccase activity under entrapped state. The immobilized cells were used as a source of laccase to develop amperometric epinephrine biosensor. The catalytic action of the laccase in the biosensor released an epinephrinequinone as a result of redox activity, thereby causing an increase in the current. The optimal working conditions of the biosensor were carried out at pH 4.5 (50 mM acetate buffer containing 100 mM K(3)Fe(CN)(6)), and 20°C. The sensor response was linear over a range of 5-100 µM epinephrine. The detection limit of the biosensor was found to be 1.04 µM. In the optimization and characterization studies of the microbial biosensor some parameters such as effect of fungi and gelatine amount, percentage of glutaraldehyde on the biosensor response and substrate specificity were carried out. In the application studies of the biosensor, sensitive determination of epinephrine in pharmaceutical ampules was investigated.