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A patient at the fifth stage of chronic kidney disease usually needs dialysis or transplantation. The adequacy of dialysis can be assessed by the dimensionless parameter Kt/V , which depends on the concentration of urea in the blood. Kt/V is usually measured before and after treatment, or by an indirect measurement of dialysis fluid conductivity. For the real-time monitoring of the urea concentration during dialysis, this paper proposes a disposable biosensor that combines a pH sensitive reduced graphene oxide layer functionalized with 4-amino benzoic acid and urease. Urease is immobilized on reduced graphene oxide and catalyzes the hydrolysis of urea into carbon dioxide and ammonia. This catalysis increases the pH value locally and elicits a sensor response. Urea concentration was assessed in the plasma of five dialyzed patients using a potentiometric measurement. The response time was 120 s and the error was 6 ± 3% compared with standard clinical laboratory analysis.

Monitoring chemical and physical properties of seawater is important to assess the status and predict future changes of marine environment. Among possible parameters, pH and temperature are frequently measured since they directly affect chemical and biological systems. Seawater assessment, conventionally performed in situ, is labour intensive and time consuming, but now remote sensor networks promise to become a viable tool to obtain spatial and temporal information over a wide range. Here we describe the development and validation of an autonomous system for the remote monitoring of pH and temperature in seawater. The device consists of a graphene-based pH sensor, a thermistor, an electronic readout, a smartphone and a power unit. After deployment in a marine testing site at the Livorno harbour in Italy, the system published on the web pH and temperature data for more than a week, whose accuracy was confirmed by comparison with a reference system.

Matrix metalloproteinases (MMPs) have been proposed as markers of many pathological conditions for their ability to degrade extracellular matrix components and remodel tissues. This review presents an overview of biosensors for the measurement of MMPs in serum, sputum and cell cultures. Major benefits and limitations of these technologies are discussed with respect to zymography and immunoassays, which are the reference methods to measure MMP activity and concentration. The paper also compares the analytical performances of sensors to the specific requirements for the application in clinical research, and comments on future trends in this field.

Matrix metalloproteinases (MMPs) are an important factor in cancer progression and metastasis, especially gelatinases MMP-2 and MMP-9. A simple methodology for their detection and monitoring is highly desirable. Molecular probes have been very widely and successfully applied to study the activity of MMPs in cellular processes in vitro. We thus synthesized a small compound library of MMP-2 and MMP-9 binding probes based on drug molecules and endowed with free amine groups for the functionalization of transducer surfaces. In this study, we combined experimental results obtained by a kinetic fluorogenic peptide substrate cleavage assay with molecular modeling studies in order to assess the ability of the probe to bind to their target enzymes. The synthesized biphenyl substituted lysine derivatives showed IC50-values in the low nanomolar concentration range against MMP-2 (ligands 3a-d: 3 nM to 8 µM, ligands 4a-d: 45 nM to 350 µM) and low micromolar range against MMP-9 (ligands 3a-d: 350 nM to 60 µM, ligands 4a-d: 5 µM to 600 µM), with a selectivity up to more than 160-fold for MMP-2. The experimental results correlated well with molecular modelling with FleXAID and X-score functions. We showed that in our compound series, the side chain remained far away from the S1′ cavity and the ligand for all the docked minima. Ligands 4a-d with their free amine group on the side chain may thus be bound to transducer surfaces for the fabrication of sensors, while retaining their activity against their target enzymes.

Quality and safety of the cold chain undergo strict international regulations that identify storage and shipping temperatures. In fact, the improper handling and transportation of temperature-sensitive products such as food and pharmaceuticals may have harmful effects on human health and a negative economic impact. A passive RFID tag modified with a copper-doped ionic liquid was used to detect the crossing of a temperature threshold (8 °C) during the shipping of medical products. The tag was insensitive to humidity variations and irreversibly changed its status once temperature exceeded the ionic liquid melting point, which can be tuned by changing the concentration of dopant.

The relevance of pH assessment in clinical analysis, environmental and industrial control, has raised the demand for the development of portable, low cost and easy-to-use monitoring systems. This paper proposes a pH sensor printed on a paper support passivated with a solid-ink coating. The sensor exploits the pH sensitivity of a reduced graphene oxide functionalized with 3-(4-aminophenil)propionic acid. The sensor responded in the pH range [4], [10] and had a sensitivity of 46 mV/pH. Tests on human plasma and seawater proved this pH sensor to have similar performances than those of a commercial pH-meter with an uncertainty of 0.1 and 0.2 pH unit in plasma and seawater, respectively.

Biofilm development on surfaces represents one of the most challenging issues in the medical field. The irreversibility of the biofilm developmental process, and the peculiar characteristics of biofilms (including the low permeability to antibacterial compounds), make biofilm associated infections difficult to treat and prone to relapse. Thanks to the short response time, low-cost, easy fabrication and potential for miniaturization, electrochemical sensors are expected to play an important role in monitoring biofilm formation. Here, we describe the use of a potentiometric sensor based on functionalized reduced graphene oxide for monitoring the formation and growth of biofilms from three bacterial species (Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus) in liquid and semisolid culture media. The Open Circuit Potential (OCP) between an Ag/AgCl pseudo reference electrode and a working electrode, both screen-printed on a flexible polyethylene terephthalate film, was measured during the growth of bacteria. The OCP decreased over time as bacteria grew on the sensor surface exhibiting a negative correlation.

The field of capacitive biosensors has grown significantly since the last comprehensive assessment by Daniels et al. in 2007. Here we how new trends in molecular imprinting, nanotechnology and microfluidics are now being exploited and demonstrate how capacitive biosensors are on the verge of becoming clinically relevant. We also shed light on recent developments in terms of test-setup, surface chemistry and test solutions.

Acetylcholine is a neurotransmitter and a neuromodulator found in the autonomic, peripheral and central nervous systems. Diazinon is a pesticide with toxic effects on humans, such as the inhibition of acetylcholine. In this paper, a biosensor is proposed for the detection of acetylcholine (range 70 - 1000 μM) and diazinon (range 0.3 - 20000 ppb). This biosensor combines a pH-sensitive layer of reduced graphene oxide functionalized with 4-aminobenzoic acid and acetylcholinesterase. This enzyme was immobilized on reduced graphene oxide and it catalyzed the conversion of acetylcholine into choline and acetic acid, locally decreasing the pH value and triggering the sensor response. The limit of detection for the acetylcholine and diazinon were 70 μM and 0.3 ppb, respectively.

Graphical abstract, A main challenge in the development of biosensing devices for the identification and quantification of nucleic acids is to avoid the amplification of the genetic material from the sample by polymerase chain reaction (PCR), which is at present necessary to enhance sensitivity and selectivity of assays. PCR has undoubtedly revolutionized genetic analyses, but it requires careful purification procedures that are not easily implemented in point of care (POC) devices. In recent years, a new strategy for nucleic acid detection based on clustered regularly interspaced short palindromic repeats (CRISPR) and associated protein systems (Cas) seems to offer unprecedented possibilities. The coupling of the CRISPR/Cas system with recent isothermal amplification methods is fostering the development of innovative optical and electrochemical POC devices. In this review, the mechanisms of action of several new CRISRP/Cas systems are reported together with their use in biosensing of nucleic acids.

The negative impact of biofilms in both the industry and the human health, demands the development of strategies for the in situ and early detection of biofilm formation. In this review we describe potentiometric, voltammetric and impedance-based sensors as to provide an overview of the different electrochemical techniques applied in biofilm detection and monitoring.

pH measuring and monitoring is fundamental to understand or control many chemical processes in biological, industrial or environmental fields. Potentiometric measurements by a glass electrode is the most common method to measure pH, although single-use paper strips are also widely used. Other methods include the use of hydrogen, quinhydron, and antimony electrodes, the imaging using pH-sensitive indicators such as dyes or proteins, and the use of ion-selective field effect transistor (ISFET). Due to the chemical reactivity of both sides of its 2D structure, nanometer thickness, high electron mobility, high reactivity to oxygen groups such as OH − , and ultrafast optical response, graphene has the potential to be used for the fabrication of nanoscale, wide-range, high-sensitivity and flexible pH sensors. This review describes how graphene, graphene oxide and reduced graphene oxide can be used to fabricate pH-sensitive devices (e.g. solution-gated FETs, solid-gate FETs, electrochemical sensors, and pH-sensitive quantum dots). The various configurations are reported along with the advantages and current limitations.

The longer life expectancy in Western countries brings forth the challenge of a growing burden [...]

The small amounts of chlorine dioxide that are routinely supplemented to drinking water as a disinfectant also cause a degradation of the polyolefin pipes that are used for distribution of the water. Commonly used phenolic antioxidants can extend the service life of the polymer but the expected lifetime is still much shorter than desired (50 years) due to depletion of the antioxidant in the surface zone exposed to the aqueous solution. In search for better stabilizers for the pipes, we have tested an organotellurium compound, 4-( N , N -dimethylamino)phenyl 3-phenoxypropyl telluride ( 1 ), as well as its corresponding selenium and sulphur analogues and a series of organotellurium compounds where the electron density at the heteroatom was varied. Stabilizers were dissolved in squalane, which is a liquid hydrocarbon that could serve as a model for a polyolefin. The oxidation induction time (OIT), determined after exposure of the squalane solution to an aqueous solution of 10 ppm of chlorine dioxide for various times was determined by DSC to indicate the loss of antioxidant protection. Whereas Irganox 1010 was only effective as a stabilizer for a few hours, many of the organochalcogen compounds were considerably more resistant (>91 h for compound 1 ) towards chlorine dioxide. Thermogravimetric analyses of antioxidants indicated insignificant decomposition below 200 °C and increasing stability for the lighter chalcogen compounds (telluride 125 Te NMR-spectroscopy, organotellurium compound 1 in the presence of an excess of chlorine dioxide failed to produce an oxidation product. This may be the clue to its long-lasting protective effect in the squalane-assay.

Wound assessment is usually performed in hospitals or specialized labs. However, since patients spend most of their time at home, a remote real time wound monitoring would help providing a better care and improving the healing rate. This review describes the advances in sensors and biosensors for monitoring the concentration of C-reactive protein (CRP), temperature and pH in wounds. These three parameters can be used as qualitative biomarkers to assess the wound status and the effectiveness of therapy. CRP biosensors can be classified in: (a) field effect transistors, (b) optical immunosensors based on surface plasmon resonance, total internal reflection, fluorescence and chemiluminescence, (c) electrochemical sensors based on potentiometry, amperometry, and electrochemical impedance, and (d) piezoresistive sensors, such as quartz crystal microbalances and microcantilevers. The last section reports the most recent developments for wearable non-invasive temperature and pH sensors suitable for wound monitoring.

K4 [BS4 O15 (OH)], Ba[B2 S3 O13 ], and Gd2 [B2 S6 O24 ] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid H[B(HSO4 )4 ] which is subsequently reacted in an open system with anhydrous chlorides of K, Ba, and Gd to the respective borosulfates and a volatile molecule (HCl). Furthermore, protonated borosulfates should be accessible by appropriate stoichiometry of the starting materials, particularly in closed systems, which inhibit deprotonation of H[B(HSO4 )4 ] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (Ba[B2 S3 O13 ] with band-silicate topology and Gd2 [B2 S6 O24 ] with cyclosilicate topology) and the first hydrogen borosulfate K4 [BS4 O15 (OH)].