Nanomaterials-based enzyme electrochemical biosensors operating through inhibition for biosensing applications

In recent years great progress has been made in applying nanomaterials to design novel biosensors. Use of nanomaterials offers to biosensing platforms exceptional optical, electronic and magnetic properties. Nanomaterials can increase the surface of the transducing area of the sensors that in turn bring an increase in catalytic behaviors. They have large surface-to-volume ratio, controlled morphology and structure that also favor miniaturization, an interesting advantage when the sample volume is a critical issue. Biosensors have great potential for achieving detect-to-protect devices: devices that can be used in detections of pollutants and other treating compounds/analytes (drugs) protecting citizens' life. After a long term focused scientific and financial efforts/supports biosensors are expected now to fulfill their promise such as being able to perform sampling and analysis of complex samples with interest for clinical or environment fields. Among all types of biosensors, enzymatic biosensors, the most explored biosensing devices, have an interesting property, the inherent inhibition phenomena given the enzyme-substrate complex formation. The exploration of such phenomena is making remarkably important their application as research and applied tools in diagnostics. Different inhibition biosensor systems based on nanomaterials modification has been proposed and applied. The role of nanomaterials in inhibition-based biosensors for the analyses of different groups of drugs as well as contaminants such as pesticides, phenolic compounds and others, are discussed in this review. This deep analysis of inhibition-based biosensors that employ nanomaterials will serve researchers as a guideline for further improvements and approaching of these devices to real sample applications so as to reach society needs and such biosensor market demands

Low-Cost, User-Friendly, All-Integrated Smartphone-Based Microplate Reader for Optical-Based Biological and Chemical Analyses

The quantitative detection of different molecular targets is of utmost importance for a variety of human activities, ranging from healthcare to environmental studies. Bioanalytical methods have been developed to solve this and to achieve the quantification of multiple targets from small volume samples. Generally, they can be divided into two different classes: point of care (PoC) and laboratory-based approaches. The former is rapid, low-cost, and user-friendly; however, the majority of the tests are semiquantitative, lacking in specificity and sensitivity. On the contrary, laboratory-based approaches provide high sensitivity and specificity, but the bulkiness of experimental instruments and complicated protocols hamper their use in resource-limited settings. In response, here we propose a smartphone-based device able to support laboratory-based optical techniques directly at the point of care. Specifically, we designed and fabricated a portable microplate reader that supports colorimetric, fluorescence, luminescence, and turbidity analyses. To demonstrate the potential of the device, we characterized its analytical performance by detecting a variety of relevant molecular targets (ranging from antibodies, toxins, drugs, and classic fluorophore dyes) and we showed how the estimated results are comparable to those obtained from a commercial microplate reader. Thanks to its low cost (< $3 00), portability (27 cm [length] × 18 cm [width] × 7 cm [height]), commercially available components, and open-source-based system, we believe it represents a valid approach to bring high-precision laboratory-based analysis at the point of care

Graphene-based Janus micromotors for the dynamic removal of pollutants

Persistent organic pollutants (POPs) are ubiquitous in the environment as a result of modern industrial processes. We present an effective POPs decontamination strategy based on their dynamic adsorption at the surface of reduced graphene oxide (rGO)-coated silica (SiO)-Pt Janus magnetic micromotors for their appropriate final disposition. While the motors rapidly move in a contaminated solution, the adsorption of POPs efficiently takes place in a very short time. Characterization of the micromotors both from the materials and from the motion point of view was performed. Polybrominated diphenyl ethers (PBDEs) and 5-chloro-2-(2,4-dichlorophenoxy) phenol (triclosan) were chosen as model POPs and the removal of the contaminants was efficiently achieved. The rGO-coated micromotors demonstrated superior adsorbent properties with respect to their concomitant GO-coated micromotors, static rGO-coated particles and dynamic silica micromotors counterparts. The extent of decontamination was studied over the number of micromotors, whose magnetic properties were used for their collection from environmental samples. The adsorption properties were maintained for 4 cycles of micromotors reuse. The new rGO-coated SiO functional material-based micromotors showed outstanding capabilities towards the removal of POPs and their further disposition, opening up new possibilities for efficient environmental remediation of these hazardous compounds

Iridium oxide (IV) nanoparticle-based lateral flow immunoassay

Lateral flow biosensors are paper-based devices that allow the detection of different types of analytes with quickness, robustness and selectivity, without leaving behind paper sensors benefits as low-cost, recyclability and sustainability. Nanomaterials have been widely reported in lateral flow biosensors, offering new sensing strategies based on optical or electrical detection techniques. Looking for other advantageous nanomaterials, we propose for the first time the use of iridium oxide (IV) nanoparticles in lateral flow assays for the detection of human immunoglobulin as a model protein. These nanoparticles can be easily prepared and conjugated with biomarkers. Their dark blue color gives a high contrast against the white background of the strips being in this way excellent labels

A novel ratiometric fluorescent approach for the modulation of the dynamic range of lateral flow immunoassays

The majority of lateral flow assays (LFAs) use single-color optical labels to provide a qualitative naked-eye detection, however this detection method displays two important limitations. First, the use of a single-color label makes the LFA prone to results misinterpretation. Second, it does not allow the precise modulation of the sensitivity and dynamic range of the test. To overcome these limitations, a ratiometric approach is developed. In particular, using anti-HIgG functionalized red-fluorescent quantum dots on the conjugate pad (as target dependent labels) and blue-fluorescent nanoparticles fixed on the test line (as target independent reporters), it is possible to generate a wide color palette (blue, purple, pink, red) on the test line. It is believed that this strategy will facilitate the development of LFAs by easily adjusting their analytical properties to the needs required by the specific application

Iridium oxide (IV) nanoparticle-based electrocatalytic detection of PBDE

Polybrominated diphenyl ethers (PBDEs) are a type of flame retardants which are currently banned in EU and USA due their hazardousness for humans and mammals. However, these compounds were highly used during more than 30 years and still persist in the environment since they are resistant to degradation. Herein we present a biosensor for the detection of PBDEs using screen printed carbon electrodes (SPCEs) based on the electrochemical monitoring of water oxidation reaction (WOR) catalyzed by iridium oxide (IV) nanoparticles (IrO NPs). Our assay shows a limit of detection of 21.5 ppb of PBDE in distilled water. We believe that such an IrO NPs-based electrocatalytic sensing system can lead to a rapid, sensitive, low cost and miniaturizable device for the detection of PBDEs

Hybrid self-assembled materials constituted by ferromagnetic nanoparticles and tannic acid : A theoretical and experimental investigation

Hybrid magnetite materials are interesting for both biomedical and catalytic applications due to their well-known biocompatibility, as well as their magnetic and electric properties. In this work we prepared Fe O nanoparticles (NPs) coated with tannic acid (TA), a natural polyphenol, through two different synthetic routes, aiming to understand the influence of TA in the synthesis step and contribute to the development of water-dispersible magnetic materials. The coating process was verified by information obtained from transmission electron microscopy (TEM), zeta-potential and Fourier transform infrared (FTIR) spectroscopy. The incorporation of TA after Fe O NPs production generated spherical NPs smaller than 10 nm, suggesting that TA plays a fundamental role in the nucleation and organization of Fe O NPs. Data from both density functional theory (DFT) and FTIR allowed us to infer that Fe O interacts mainly with the carbonyl groups of TA. Hybrid materials having improved water-dispersibility are very attractive for biomedical applications

Nanomaterial-based Sensors for the Study of DNA Interaction with Drugs

The interaction of drugs with DNA has been searched thoroughly giving rise to an endless number of findings of undoubted importance, such as a prompt alert to harmful substances, ability to explain most of the biological mechanisms, or provision of important clues in targeted development of novel chemotherapeutics. The existence of some drugs that induce oxidative damage is an increasing point of concern as they can cause cellular death, aging, and are closely related to the development of many diseases. Because of a direct correlation between the response, strength/ nature of the interaction and the pharmaceutical action of DNA-targeted drugs, the electrochemical analysis is based on the signals of DNA before and after the interaction with the DNA-targeted drug. Nowadays, nanoscale materials are used extensively for offering fascinating characteristics that can be used in designing new strategies for drug-DNA interaction detection. This work presents a review of nanomaterials (NMs) for the study of drug-nucleic acid interaction. We summarize types of drug-DNA interactions, electroanalytical techniques for evidencing these interactions and quantification of drug and/or DNA monitoring

Superhydrophobic Alkanethiol-Coated Microsubmarines for Effective Removal of Oil

We demonstrate the use of artificial nanomachines for effective interaction, capture, transport, and removal of oil droplets. The simple nanomachine-enabled oil collection method is based on modifying microtube engines with a superhydrophobic layer able to adsorb oil by means of its strong adhesion to a long chain of self-assembled monolayers (SAMs) of alkanethiols created on the rough gold outer surface of the device. The resultant SAM-coated Au/Ni/PEDOT/Pt microsubmarine displays continuous interaction with large oil droplets and is capable of loading and transporting multiple small oil droplets. The influence of the alkanethiol chain length, polarity, and head functional group and hence of the surface hydrophobicity upon the oil–nanomotor interaction and the propulsion is examined. No such oil–motor interactions were observed in control experiments involving both unmodified microengines and microengines coated with SAM layers containing a polar terminal group. These results demonstrate that such SAM-Au/Ni/PEDOT/Pt micromachines can be useful for a facile, rapid, and efficient collection of oils in water samples, which can be potentially exploited for other water–oil separation systems. The integration of oil-sorption properties into self-propelled microengines holds great promise for the remediation of oil-contaminated water samples and for the isolation of other hydrophobic targets, such as drugs