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Electrospinning has emerged as a very powerful method combining efficiency, versatility and low cost to elaborate scalable ordered and complex nanofibrous assemblies from a rich variety of polymers. Electrospun nanofibers have demonstrated high potential for a wide spectrum of applications, including drug delivery, tissue engineering, energy conversion and storage, or physical and chemical sensors. The number of works related to biosensing devices integrating electrospun nanofibers has also increased substantially over the last decade. This review provides an overview of the current research activities and new trends in the field. Retaining the bioreceptor functionality is one of the main challenges associated with the production of nanofiber-based biosensing interfaces. The bioreceptors can be immobilized using various strategies, depending on the physical and chemical characteristics of both bioreceptors and nanofiber scaffolds, and on their interfacial interactions. The production of nanobiocomposites constituted by carbon, metal oxide or polymer electrospun nanofibers integrating bioreceptors and conductive nanomaterials (e.g., carbon nanotubes, metal nanoparticles) has been one of the major trends in the last few years. The use of electrospun nanofibers in ELISA-type bioassays, lab-on-a-chip and paper-based point-of-care devices is also highly promising. After a short and general description of electrospinning process, the different strategies to produce electrospun nanofiber biosensing interfaces are discussed.

Polydiacetylene (PDA) inserted in films or in vesicles has received increasing attention due to its property to undergo a blue-to-red colorimetric transition along with a change from non-fluorescent to fluorescent upon application of various stimuli. In this review paper, the principle for the detection of various microorganisms (bacteria, directly detected or detected through the emitted toxins or through their DNA, and viruses) and of antibacterial and antiviral peptides based on these responsive PDA vesicles are detailed. The analytical performances obtained, when vesicles are in suspension or immobilized, are given and compared to those of the responsive vesicles mainly based on the vesicle encapsulation method. Many future challenges are then discussed.

The rapid and sensitive detection of food contaminants is becoming increasingly important for timely prevention and treatment of foodborne disease. In this review, we discuss recent developments of electrochemical biosensors as facile, rapid, sensitive, and user-friendly analytical devices and their applications in food safety analysis, owing to the analytical characteristics of electrochemical detection and to advances in the design and production of bioreceptors (antibodies, DNA, aptamers, peptides, molecular imprinted polymers, enzymes, bacteriophages, etc.). They can offer a low limit of detection required for food contaminants such as allergens, pesticides, antibiotic traces, toxins, bacteria, etc. We provide an overview of a broad range of electrochemical biosensing designs and consider future opportunities for this technology in food control.

Arsenic is ubiquitous in the biosphere and frequently reported to be an environmental pollutant. Global cycling of arsenic is affected by microorganisms. This paper describes a new bacterial strain which is able to efficiently oxidize arsenite (As[III]) into arsenate (As[V]) in liquid medium. The rate of the transformation depends on the cell density. Arsenic species were separated by high performance liquid chromatography (HPLC) and quantified by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The strain also exhibits high minimum inhibitory concentrations (MICs) for As[III] (6.65 mM (500 mg L-1)) and other heavy metals, such as cadmium (1.42 mM (160 mg L-1)) or lead (1.20 mM (250 mg L-1)). Partial identification of the strain revealed a chemoorganotrophic, Gram-negative and motile rod. The results presented here demonstrate that this strain could represent a good candidate for arsenic remediation in heavily polluted sites.

In this work, the method of enzyme adsorption on different zeolites and mesoporous silica spheres (MSS) was investigated for the creation of conductometric biosensors. The conductometric transducers consisted of gold interdigitated electrodes were placed on the ceramic support. The transducers were modified with zeolites and MSS, and then the enzymes were adsorbed on the transducer surface. Different methods of zeolite attachment to the transducer surface were used; drop coating with heating to 200°C turned out to be the best one. Nanozeolites beta and L, zeolite L, MSS, and silicalite-1 (80 to 450 nm) were tested as the adsorbents for enzyme urease. The biosensors with all tested particles except zeolite L had good analytical characteristics. Silicalite-1 (450 nm) was also used for adsorption of glucose oxidase, acetylcholinesterase, and butyrylcholinesterase. The glucose and acetylcholine biosensors were successfully created, whereas butyrylcholinesterase was not adsorbed on silicalite-1. The enzyme adsorption on zeolites and MSS is simple, quick, well reproducible, does not require use of toxic compounds, and therefore can be recommended for the development of biosensors when these advantages are especially important.

A new conductometric enzyme-based biosensor was developed for the determination of formaldehyde (FA) in aqueous solutions. The biosensor was prepared by cross-linking formaldehyde dehydrogenase from Pseudomonas putida with bovine serum albumin in saturated glutaraldehyde vapours (GA) at the surface of interdigitated gold microelectrodes. Nicotinamide adenine dinucleotide cofactor ([NAD.sup.+]) was added in solution at each measurement to maintain enzyme activity. Addition of a Nafion layer over the enzyme modified electrode resulted in a significant increase of biosensor signal due to enhanced accumulation of protons generated by enzymatic reaction at the electrode surface. Different parameters affecting enzyme activity or playing a role in ionic transfer through the Nafion membrane were optimised. In optimal conditions (0.045 mg enzyme, 30 min exposure to GA, 0.3 µLofa1%(v/v) Nafion solution deposit, measurement in 5 mM phosphate buffer pH 7 containing 20 µM [NAD.sup.+]), the biosensor signal was linear up to 10 mM FA, and the detection limit was 18 µM. Relative standard deviations calculated from five consecutive replicates of FA solutions were lower than 5 % in the 1-10 mM range. The biosensor was successfully applied to the determination of FA in spiked water samples (tap water and Rhone river water), with recoveries in the 95-110 % range.

The application of silicalite for improvement of working characteristics of conductometric enzyme biosensors for determination of sucrose was studied in this research. Biosensors based on different types of silicalite-modified electrodes were studied and compared according to their analytical characteristics. Polyethylenimine/glutaraldehyde/silicalite-modified biosensors showed higher sensitivity compared with others type of biosensors. Moreover, the polyethylenimine/glutaraldehyde/silicalite sucrose biosensors were characterized by high selectivity and signal reproducibility (relative standard deviation (RSD) = 2.78% for glucose measurements and RSD = 3.2% for sucrose measurements). Proposed biosensors were used for determination of sucrose in different samples of beverages. The obtained results had good correlation with results obtained by HPLC. Thus, polyethylenimine/glutaraldehyde/silicalite-modified biosensors have shown perspective characteristics for the development of effective conductometric enzyme biosensors.

An efficient, inexpensive microplate colorimetric assay for screening of bacteria which can be used in bioremediation of arsenic was developed. The assay is based on the colorimetric analysis of the precipitates formed upon reaction of silver nitrate with arsenic. The method proved reliable and sensitive for the detection of As[III] oxidizers and As[V] reducers and can be used over a large pH range (5.8–8.4). Seventy-eight bacterial strains isolated from different environments were tested by this method. It also showed agreement with results obtained by high-performance liquid chromatography coupled with inductively coupled plasma atomic emission spectrometry.

A new conductometric enzyme-based biosensor was developed for the determination of formaldehyde (FA) in aqueous solutions. The biosensor was prepared by cross-linking formaldehyde dehydrogenase from Pseudomonas putida with bovine serum albumin in saturated glutaraldehyde vapours (GA) at the surface of interdigitated gold microelectrodes. Nicotinamide adenine dinucleotide cofactor (NAD + ) was added in solution at each measurement to maintain enzyme activity. Addition of a Nafion layer over the enzyme modified electrode resulted in a significant increase of biosensor signal due to enhanced accumulation of protons generated by enzymatic reaction at the electrode surface. Different parameters affecting enzyme activity or playing a role in ionic transfer through the Nafion membrane were optimised. In optimal conditions (0.045 mg enzyme, 30 min exposure to GA, 0.3 μL of a 1 % ( v/v ) Nafion solution deposit, measurement in 5 mM phosphate buffer pH 7 containing 20 μM NAD + ), the biosensor signal was linear up to 10 mM FA, and the detection limit was 18 μM. Relative standard deviations calculated from five consecutive replicates of FA solutions were lower than 5 % in the 1–10 mM range. The biosensor was successfully applied to the determination of FA in spiked water samples (tap water and Rhone river water), with recoveries in the 95–110 % range. Figure ᅟ

Separation and quantification of six arsenic species have been performed in cod, tuna and mussel samples by high performance liquid chromatography (HPLC) using inductively coupled plasma-optical emission spectrometry (ICP-OES) and hydride generation-quartz furnace atomic absorption spectrometry (HG-QFAAS) as detection techniques. It has been shown that arsenic extraction with a water-methanol (1∶1) mixture is sufficiently quantitative for the cod and tuna, in which arsenic is mainly present as arsenobetaine (about 90% of total As extracted). In contrast, only 60% of the element is extracted from the mussels and the chromatograms obtained reveal the presence of an unknown compound. Detection limits are in the μg ml−1 range for the HPLC-ICP-OES technique (quantification of arsenobetaine and arsenocholine) and in the ng ml−1 range for the HPLC-HG-QFAAS system (quantification of arsenite, arsenate, monomethylarsonic and dimethylarsinic acids).