Impedimetric detection of gut-derived metabolites using 2D Germanene-based materials.

Apart from the extensively researched graphene under the Group 14 2D materials, monolayered germanene and its derivatives have been gaining interest lately as alternative class of 2D materials owing to their facile synthesis, and attractive electronic and optical properties. Herein, three different functionalized germanene-based nanomaterials, namely Ge-H, Ge-CH3 and Ge-C3-CN were investigated on their novel incorporation in impedimetric immunosensors for the detection of gut-derived metabolites associated with neurological diseases, such as kynurenic acid (KA) and quinolinic acid (QA). The designed germanene-based immunosensor relies on an indirect competitive mechanism using disposable electrode printed chips. The competition for a fixed binding site of a primary antibody occurs between the bovine serum albumin-conjugated antigens on the electrode surface and the free antigens in the solution. Among the three materials, Ge-H displayed superior bioanalytical performance in KA and QA detection. Lower limits of detection of 5.07-11.38 ng/mL (26.79-68.11 nM) were attained for KA and QA with a faster reaction time than previously reported methods. Also, minimal cross-reactivity with interfering compounds, good reproducibility in impedimetric responses (RSD = 2.43-7.51 %) and long-term stability up to a month at 4 °C were the other attributes that the proposed Ge-H competitive impedimetric immunosensor has accomplished. The application of the developed Ge-H immunosensor to serum samples allowed an accurate KA and QA quantification at physiologically relevant levels. This work serves as a stepping-stone in the development of germanene-based nanomaterials for their implementation into cost-effective, miniaturized, portable and rapid impedimetric immunosensors, which are highly desirable for point-of-care testing in clinical settings.

Full Sails against Cancer.

BACKGROUND: Cancer is very disruptive in adolescence and hospitalizations interfere with this development stage in becoming independent, developing social relationships, and making plans for the future. A major challenge in the care of adolescents with cancer is being able to enhance their quality of life. The aim of this project is to increase our understanding of how adventure therapy influenced quality of life for adolescents with cancer. METHODS: Bambino Gesù Children's Hospital, in collaboration with the Tender to Nave Italia Foundation (TTNI), has been conducting a unique project, located on a beautiful brigantine of the Italian Navy. Adventure therapy is a form of experiential therapy that consists of various types of adventure, in particular outdoor and sailing activities. Ninety teenagers have been the protagonists of this project to date and filled out two questionnaires about quality of life and self-esteem, before and after the sailing experience. RESULTS: The adventure provides the opportunity for the participants to build interpersonal relationships and develop life skills that they can benefit from in the future experiences. All participants report a significant improvement in their quality of life and self-esteem at the end of this experience. CONCLUSION: This collaborative adventure project is a great way to learn and practice new behaviors, improve interpersonal skills, heal painful emotions, overcome personal obstacles and challenges, and help the teenagers to resume their developmental path after an onco-hematological diagnosis.

Electroactive nanocarbon materials as signaling tags for electrochemical PCR.

Electrochemical polymerase chain reaction (PCR) represents a valid alternative to the optical-based PCR due to reduced costs of signaling labels, use of simpler instrumentation, and possibility of miniaturization and portability of the systems, which can facilitate decentralized detection. The high intrinsic electroactivity and strong linear relationship between the material concentration and its redox signal suggest a possible use of oxidized nanocarbon materials as electroactive tags for PCR. Herein, we compared three different nanographene oxide materials namely nGO-1, nGO-2 and nGO-3 as signaling tags for the detection of genetically modified organisms (GMO) by electrochemical PCR. The three materials differ in size, chemical composition as well as type and amount of oxygen functionalities verified by extensive characterization with X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), transmission electron microscopy (TEM) and electrochemical methods. A sense primer sequence belonging to the Cauliflower Mosaic Virus 35S promoter (a common genetic marker for GMO screening) was used to conjugate to the nanocarbon materials by carbodiimide chemistry before PCR amplification with a biotinylated antisense strand. Finally, the amplified electroactive PCR product was detected, where the reduction signal derived from the electrochemically reducible oxygenated functionalities on the nanocarbon material surface was directly correlated to the presence of GMO. Overall, we were able to correlate the different material characteristics with their performance as electroactive labels and identify the nanocarbon material that exhibits the highest potential to be used as innovative electroactive label for PCR in the amplification and detection of the selected target sequence.

Exploring graphene oxide intrinsic electroactivity to elucidate the non-covalent interactions with DNA oligonucleotides.

We show here how the electrochemical reduction signal of graphene oxide nanocolloids is inhibited upon the formation of non-covalent interactions with single stranded DNA oligonucleotides. The drop in the reduction current intensity is strongly influenced by the nucleobase sequence, and can therefore be directly correlated to the specific DNA homo-oligonucleotide.

How 3D printing can boost advances in analytical and bioanalytical chemistry.

3D printing fabrication methods have received lately an enormous attention by the scientific community. Laboratories and research groups working on analytical chemistry applications, among others, have advantageously adopted 3D printing to fabricate a wide range of tools, from common laboratory hardware to fluidic systems, sample treatment platforms, sensing structures, and complete fully functional analytical devices. This technology is becoming more affordable over time and therefore preferred over the commonly used fabrication processes like hot embossing, soft lithography, injection molding and micromilling. However, to better exploit 3D printing fabrication methods, it is important to fully understand their benefits and limitations which are also directly associated to the properties of the materials used for printing. Costs, printing resolution, chemical and biological compatibility of the materials, design complexity, robustness of the printed object, and integration with commercially available systems represent important aspects to be weighted in relation to the intended task. In this review, a useful introductory summary of the most commonly used 3D printing systems and mechanisms is provided before the description of the most recent trends of the use of 3D printing for analytical and bioanalytical chemistry. Concluding remarks will be also given together with a brief discussion of possible future directions.

Effect of surface chemistry on bio-conjugation and bio-recognition abilities of 2D germanene materials.

The interest of the scientific community for 2D graphene analogues has been recently focused on 2D-Xene materials from Group 14. Among them, germanene and its derivatives have shown great potential because of their large bandgap and easily tuneable electronic and optical properties. With the latter having been already explored, the use of chemically modified germanenes for optical bio-recognition is yet to be investigated. Herein, we have synthesized two germanene materials with different surface ligands namely hydrogenated germanene (Ge-H) and methylated germanene (Ge-Me) and used them as an optical platform for the label-free biorecognition of Ochratoxin A (OTA), a highly carcinogenic food contaminant. It was discovered that firstly the surface ligands on chemically modified germanenes have strong influence on the intrinsic fluorescence of the material; secondly they also highly affect both the bio-conjugation ability and the bio-recognition efficiency of the material towards the detection of the analyte. An improved calibration sensitivity, together with superior reproducibility and linearity of response, was obtained with a methylated germanene (Ge-Me) material, indicating also the better suitability of the latter for real sample analysis. Such research is highly beneficial for the development and optimization of 2D material based optical platforms for fast and cost-effective bioassays.

The potential of electrochemistry for the detection of coronavirus-induced infections.

Human coronaviruses (HCoV) are no stranger to the global environment. The etiology of previous outbreaks with reported symptoms of respiratory tract infections was attributed to different coronavirus strains, with the latest global pandemic in 2019 also belonging to the coronavirus family. Timely detection, effective therapeutics and future prevention are stake key holders in the management of coronavirus-induced infections. Apart from the gold standard clinical diagnostics, electrochemical techniques have also demonstrated their great potentials in the detection of different viruses and their correlated antibodies and antigens, showing high sensitivities and selectivities, and faster times for the analysis. This article aims to critically review the multifaceted electrochemical approaches, not only in the development of point-of-care portable devices but also as alternative detection strategies that can be coupled with traditional methods for the detection of various strains of coronaviruses.

Unravelling the Aptamer-Analyte Interaction Dynamics through Fluorescence Quenching in Graphene Quantum Dots (GQDs) Based Homogeneous Assays.

Graphene quantum dots (GQDs) are used here as a biosensing platform for the recognition of the major food contaminant ochratoxin A (OTA), with a fluorescently labelled DNA aptamer (FAM OTA aptamer) functioning as the biorecognition element. The detection principle lies in the formation of noncovalent interactions between the FAM OTA aptamer and the GQD surface, and the consequent fluorescence quenching. The further change in the fluorescence signal, induced by the formation of the FAM OTA Aptamer/OTA conjugate during the detection step, could then be correlated to the presence and concentration of the target analyte. Upon tuning the concentration of GQDs, a switch in the biorecognition mechanism occurred. Specifically, while a lower GQD concentration (0.060 mg/mL) resulted in a restoration of the fluorescence intensity upon incubation with OTA, a higher GQD concentration (0.150 mg/mL) provided a further quenching of the final fluorescence intensity. Upon further calibration study, it was discovered that the latter mechanism provided a better option in terms of linearity of response, detection limit and selectivity.

All-in-One: Electroactive Nanocarbon as Simultaneous Platform and Label for Single-Step Biosensing.

We demonstrate here that an electroactive nanocarbon material can simultaneously work as both platform and label for the detection of mycotoxins. The versatility of the material for the immobilization of biorecognition elements was combined with its ability to provide an intrinsic electrochemical signal upon reduction of the oxygen functionalities on its surface. The intensity of peak current reflects the availability of oxygen functionalities for reduction, which can be directly correlated to the specific biorecognition event. We show that the use of electroactive nanocarbon as all-in-one biosensing component enables sensitive quantification of Fumonisin B1 (FB1 ) as model mycotoxin analyte, but it can be easily implemented to develop label-free, cost-effective and fast bioanalytical devices for universal biosensing.

Investigation on the ability of heteroatom-doped graphene for biorecognition.

Doped graphene platforms have been attracting considerable attention due to their improved electrochemical performances. Recent studies have shown the advantage of using either p-type or n-type doped graphene materials as transducers for the detection of various electroactive probes. Here we wanted to take a step forward and extend the study to investigate the ability of heteroatom doped graphene as an electrochemical platform for biorecognition. To this aim, a boron-doped graphene, a nitrogen-doped graphene and an undoped graphene material prepared under similar conditions were employed for the detection of fumonisin B1, a highly carcinogenic mycotoxin found in food commodities. We found that the material structural features, such as the amount of oxygen functionalities, had a stronger influence on the sensitivity of biorecognition rather than the kind and amount of dopant. Our findings may be essential for the choice of a proper platform for the assessment of food safety.

Chemically Reduced Graphene Oxide for the Assessment of Food Quality: How the Electrochemical Platform Should Be Tailored to the Application.

Graphene platforms have been drawing considerable attention in electrochemistry for the detection of various electroactive probes. Depending on the chemical composition and properties of the probe, graphene materials with diverse structural features may be required to achieve an optimal electrochemical performance. This work comprises a comparative study on three chemically modified graphenes, obtained from the same starting material and with different oxygen functionalities and structural defects (graphene oxide (GO), chemically reduced graphene oxide (CRGO), and thermally reduced graphene oxide (TRGO)) towards the electrochemical detection of quinine, an important flavoring agent present in tonic-based beverages. In general, the reduced graphenes, namely CRGO and TRGO, showed enhanced performance in terms of calibration sensitivity and selectivity, due to the improved heterogeneous electron-transfer rates on their surfaces. In particular, CRGO provided the best overall electrochemical performance, which can be attributed to its higher density of structural defects and reduced amount of oxygen functionalities. For this reason, CRGO was employed for the electrochemical detection of quinine in commercial tonic drink samples, showing high sensitivity and selectivity, and therefore representing a valid low-cost alternative to more complicated and time consuming traditional analytical methods.

Doped Graphene for DNA Analysis: the Electrochemical Signal is Strongly Influenced by the Kind of Dopant and the Nucleobase Structure.

Doping graphene with heteroatoms can alter the electronic and electrochemical properties of the starting material. Contrasting properties should be expected when the doping is carried out with electron donating species (n-type dopants) or with electron withdrawing species (p-type dopants). This in turn can have a profound influence on the electroanalytical performance of the doped material being used for the detection of specific probes. Here we investigate the electrochemical oxidation of DNA bases adenine, guanine, thymine and cytosine on two heteroatom-doped graphene platforms namely boron-doped graphene (p-type dopant) and nitrogen-doped graphene (n-type dopant). We found that overall, boron-doped graphene provided the best response in terms of electrochemical signal sensitivity for all bases. This is due to the electron deficiency of boron-doped graphene, which can promote the oxidation of DNA bases, as opposed to nitrogen-doped graphene which possesses an excess of electrons. Moreover, also the structure of the nucleobase was found to have significant influence on the obtained signal. Our study may open new frontiers in the electrochemical detection of DNA bases which is the first step for label-free DNA analysis.

Strong dependence of fluorescence quenching on the transition metal in layered transition metal dichalcogenide nanoflakes for nucleic acid detection.

In recent years, the application of transition metal dichalcogenides for the development of biosensors has been receiving widespread attention from researchers, as demonstrated by the surge in studies present in the field. While different transition metal dichalcogenide materials have been employed for the fabrication of fluorescent biosensors with superior performance, no research has been conducted to draw comparisons across materials containing different transition metals. Herein, the performance of MoS2 and WS2 nanoflakes for the fluorescence detection of nucleic acids is assessed. It is discovered that, at the optimal amount, MoS2 and WS2 nanoflakes exhibit a similar degree of fluorescence quenching, at 75% and 71% respectively. However, MoS2 nanoflakes have better performance in the areas of detection range and selectivity than WS2 nanoflakes. The detection range achieved with MoS2 nanoflakes is 9.60-366 nM while 13.3-143 nM with WS2 nanoflakes. In the context of selectivity, MoS2 nanoflakes display a signal difference of 97.8% between complementary and non-complementary DNA targets, whereas WS2 nanoflakes only exhibit 44.3%. Such research is highly beneficial as it delivers vital insights on how the performance of a fluorescent biosensor can be affected by the transition metal present. Furthermore, these insights can assist in the selection of suitable transition metal dichalcogenide materials for utilization in biosensor development.

Graphene and its electrochemistry - an update.

The electrochemistry of graphene and its derivatives has been extensively researched in recent years. In the aspect of graphene preparation methods, the efficiencies of the top-down electrochemical exfoliation of graphite, the electrochemical reduction of graphene oxide and the electrochemical delamination of CVD grown graphene, are currently on par with conventional procedures. Electrochemical analysis of graphene oxide has revealed an unexpected inherent redox activity with, in some cases, an astonishing chemical reversibility. Furthermore, graphene modified with p-block elements has shown impressive electrocatalytic performances in processes which have been historically dominated by metal-based catalysts. Further progress has also been achieved in the practical usage of graphene in sensing and biosensing applications. This review is an update of our previous article in Chem. Soc. Rev. 2010, 39, 4146-4157, with special focus on the developments over the past two years.

Doped and undoped graphene platforms: the influence of structural properties on the detection of polyphenols.

There is a huge interest in doped graphene and how doping can tune the material properties for the specific application. It was recently demonstrated that the effect of doping can have different influence on the electrochemical detection of electroactive probes, depending on the analysed probe, on the structural characteristics of the graphene materials and on the type and amount of heteroatom used for the doping. In this work we wanted to investigate the effect of doping on graphene materials used as platform for the detection of catechin, a standard probe which is commonly used for the measurement of polyphenols in food and beverages. To this aim we compared undoped graphene with boron-doped graphene and nitrogen doped graphene platforms for the electrochemical detection of standard catechin oxidation. Finally, the material providing the best electrochemical performance was employed for the analysis of real samples. We found that the undoped graphene, possessing lower amount of oxygen functionalities, higher density of defects and larger electroactive surface area provided the best electroanalytical performance for the determination of catechin in commercial beer samples. Our findings are important for the development of novel graphene platforms for the electrochemical assessment of food quality.

Carboxylic Carbon Quantum Dots as a Fluorescent Sensing Platform for DNA Detection.

The demand for simple, sensitive, affordable, and selective DNA biosensors is ubiquitous, due to the important role that DNA detection performs in the areas of disease diagnostics, environment monitoring, and food safety. A novel application of carboxylic carbon quantum dots (cCQD) is highlighted in this study. Herein, cCQD function as a nanoquencher in the detection of nucleic acid based on a homogeneous fluorescent assay. To that purpose, the performance of two types of cCQD, namely, citric acid QD and malic acid QD, is evaluated. The principle behind the sensing of nucleic acid lies in the different propensity of single-stranded DNA and double-stranded DNA to adsorb onto the surface of cCQD. For both types of cCQD, a superior range of detection of at least 3 orders of magnitude is achieved, and the potential to distinguish single-base mismatch is also exhibited. These findings are anticipated to provide valuable insights on the employment of cCQD for the fabrication of future DNA biosensors.

Improving the Analytical Performance of Graphene Oxide towards the Assessment of Polyphenols.

The presence of oxygen functionalities on graphene surface has enormous influence on its electrochemical and electroanalytical properties. The oxygen-containing groups on graphene platforms can strongly affect the electrochemical response, being either detrimental for the heterogeneous charge transfer or promoting a favourable interaction with the specific analyte. In this study, by electrochemically reducing graphene oxide material at increasing negative potentials (from -0.25 to -1.50 V) we obtained eight electrochemically reduced graphene oxide (ERGO) platforms carrying a decreasing amount of oxygen functionalities. Subsequently, we analysed the electroanalytical response of each ERGO material for the detection of gallic acid, a standard polyphenol that is correlated to the antioxidant activity of food and beverages. The graphene platform providing the best electroanalytical performance in terms of sensitivity, selectivity and linearity of response was then employed for the analysis of commercial fruit juice samples. Herein we demonstrated that graphene materials can be electrochemically tuned to optimise their electrochemical response towards the detection of biologically important analytes.

Chemically Modified Graphene: The Influence of Structural Properties on the Assessment of Antioxidant Capacity.

Graphene materials obtained by different synthetic routes possess dissimilar amount of defects and surface functionalities, which can influence their electrochemical performance towards the detection of electroactive probes. Oxygen-containing groups can be either detrimental to the heterogeneous charge transfer or promote favorable interactions between the graphene surface and the analyte of interest, depending on the structure of the latter. Here, we compared three chemically modified graphenes, obtained by various procedures and carrying different amounts of oxygen functionalities, for the detection of standard gallic acid, a compound commonly used as an index of the antioxidant capacity of food and beverages. We found that electrochemically reduced graphene provided the best electrochemical performance in terms of calibration sensitivity, selectivity, and linearity of response. Our findings are important in order to understand the suitability of graphene platforms for the assessment of food quality.

Transitional Metal/Chalcogen Dependant Interactions of Hairpin DNA with Transition Metal Dichalcogenides, MX2.

Owing to the attractive properties that transition metal dichalcogenides (TMDs) display, they have found recent application in the fabrication of biosensing devices. These devices involve the immobilization of a recognition element such as DNA onto the surface of TMDs. Therefore, it is imperative to examine the interactions between TMDs and DNA. Herein, we explore the effect of different transition metals (Mo and W) and chalcogens (S and Se) on the interactions between hairpin DNA and TMDs of both bulk and t-BuLi exfoliated forms. We discovered that the interactions are strongly dependent on the metal/chalcogen composition in TMDs.

The dopant type and amount governs the electrochemical performance of graphene platforms for the antioxidant activity quantification.

Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry.