Mechanisms of nanophase-induced desorption in LDI-MS. A short review

Nanomaterials are frequently used in laser desorption ionization mass spectrometry (LDI-MS) as DI enhancers, providing excellent figures of merit for the analysis of low molecular weight organic molecules. In recent years, literature on this topic has benefited from several studies assessing the fundamental aspects of the ion desorption efficiency and the internal energy transfer, in the case of model analytes. Several different parameters have been investigated, including the intrinsic chemical and physical properties of the nanophase (chemical composition, thermal conductivity, photo-absorption efficiency, specific heat capacity, phase transition point, explosion threshold, etc.), along with morphological parameters such as the nanophase size, shape, and interparticle distance. Other aspects, such as the composition, roughness and defects of the substrate supporting the LDI-active nanophases, the nanophase binding affinity towards the target analyte, the role of water molecules, have been taken into account as well. Readers interested in nanoparticle based LDI-MS sub-techniques (SALDI-, SELDI-, NALDI- MS) will find here a concise overview of the recent findings in the specialized field of fundamental and mechanistic studies, shading light on the desorption ionization phenomena responsible of the outperforming MS data offered by these techniques

Electrochemical and X-ray Photoelectron Spectroscopy Surface Characterization of Interchain-Driven Self-Assembled Monolayer (SAM) Reorganization

Herein, we report a combined strategy encompassing electrochemical and X-ray photoelectron spectroscopy (XPS) experiments to investigate self-assembled monolayer (SAM) conformational reorganization onto an electrode surface due to the application of an electrical field. In particular, 3-mercaptopriopionic acid SAM (3MPA SAM) modified gold electrodes are activated with a 1-ethyl-3- (3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysulfosuccinimide (NHSS) (EDC-NHSS) mixture by shortening the activation time, from 2 h to 15/20 min, labelled as Protocol-A, -B and -C, respectively. This step, later followed by a deactivation process with ethanolamine (EA), plays a key role in the reaction yields (formation of N-(2-hydroxyethyl)-3-mercaptopropanamide, NMPA) but also in the conformational rearrangement observed during the application of the electrical field. This study aims at explaining the high performance (i.e., single-molecule detection at a large electrode interface) of bioelectronic devices, where the 3MPA-based SAM structure is pivotal in achieving extremely high sensing performance levels due to its interchain interaction. Cyclic voltammetry (CV) experiments performed in K4Fe(CN)6:K3Fe(CN)6 for 3MPA SAMs that are activated/deactivated show similar trends of anodic peak current (IA) over time, mainly related to the presence of interchain hydrogen bonds, driving the conformational rearrangements (tightening of SAMs structure) while applying an electrical field. In addition, XPS analysis allows correlation of the deactivation yield with electrochemical data (conformational rearrangements), identifying the best protocol in terms of high reaction yield, mainly related to the shorter reaction time, and not triggering any side reactions. Finally, Protocol-C’s SAM surface coverage, determined by CV in H2SO4 and differential pulse voltammetry (DPV) in NaOH, was 1.29 * 1013 molecules cm2, being similar to the bioreceptor surface coverage in single-molecule detection at a large electrode interface

Enhanced stability of organic field-effect transistor biosensors bearing electrosynthesized ZnO nanoparticles

Herein electrosynthesized ZnO nanoparticles (ZnO NPs) agents to largely improve functional bio-interlayer organic field-effect transistor (FBI-OFET) biosensors stability are investigated. For a proof-of-principle, streptavidin (SA) was chosen as the capturing biomolecule to sense biotin and poly-3-hexylthiophene (P3HT) served as channel material. The ZnO NPs were prepared and integrated into the FBI-OFET architecture by means of a straightforward and versatile procedure. To this end, ZnO NPs were mixed with an SA solution and the resulting aqueous suspension was readily spin-coated onto the SiO2gate dielectric. The P3HT film was spin-coated on the SA-ZnO NPs layer afterwards with the whole fabrication procedure taking no more than 30 min. The FBI-OFET biosensors bearing the ZnO NPs exhibited a shelf life exceeding one year, while the bare ones failed to work after few weeks. Moreover, the ZnO NPs enabled a two orders of magnitude increase in field-effect mobility while the already proven very good sensing performances were retained. The electrical and XPS characterization of the ZnO NPs based functional bio-interlayer provided information about the role of the nanostructured oxide on the improved device stability and a plausible mechanism for this occurrence is derived accordingly

A Review on Montmorillonite-Based Nanoantimicrobials: State of the Art

One of the crucial challenges of our time is to effectively use metal and metal oxide nanoparticles (NPs) as an alternative way to combat drug-resistant infections. Metal and metal oxide NPs such as Ag, Ag2O, Cu, Cu2O, CuO, and ZnO have found their way against antimicrobial resistance. However, they also suffer from several limitations ranging from toxicity issues to resistance mechanisms by complex structures of bacterial communities, so-called biofilms. In this regard, scientists are urgently looking for convenient approaches to develop heterostructure synergistic nanocomposites which could overcome toxicity issues, enhance antimicrobial activity, improve thermal and mechanical stability, and increase shelf life. These nanocomposites provide a controlled release of bioactive substances into the surrounding medium, are cost effective, reproducible, and scalable for real life applications such as food additives, nanoantimicrobial coating in food technology, food preservation, optical limiters, the bio medical field, and wastewater treatment application. Naturally abundant and non-toxic Montmorillonite (MMT) is a novel support to accommodate NPs, due to its negative surface charge and control release of NPs and ions. At the time of this review, around 250 articles have been published focusing on the incorporation of Ag-, Cu-, and ZnO-based NPs into MMT support and thus furthering their introduction into polymer matrix composites dominantly used for antimicrobial application. Therefore, it is highly relevant to report a comprehensive review of Ag-, Cu-, and ZnO-modified MMT. This review provides a comprehensive overview of MMT-based nanoantimicrobials, particularly dealing with preparation methods, materials characterization, and mechanisms of action, antimicrobial activity on different bacterial strains, real life applications, and environmental and toxicity issues

Electrostatic Catalysis of a Click Reaction in a Microfluidic Cell

Electric fields have been highlighted as a smart reagent in nature's enzymatic machinery, as they can directly trigger or accelerate redox and/or non-redox chemical processes with stereo- and regio-specificity. In natural catalysis, controlled mass transport of chemical species in confined spaces is also key in facilitating the transport of reactants into the active reaction site. Despite the opportunities the above offers in developing strategies for a new, clean electrostatic catalysis exploiting oriented electric fields, research in this area has been mostly limited to theoretical and experimental studies at the level of single molecules or small molecular ensembles, where both the control over mass transport and scalability cannot be tested. Here, we quantify the electrostatic catalysis of a prototypical Huisgen cycloaddition in a large-area electrode surface and directly compare its performance to the traditional Cu(I)-catalyzed method of the same reaction. Mass diffusion control is achieved in a custom-built microfluidic cell, which enhances reagent transport towards the electrified reactive interface while avoiding both turbulent flow conditions and poor control of the convective mass transport. This unprecedented electrostatic continuous-flow microfluidic reactor is an example of an electric-field driven platform where clean large-scale electrostatic catalytic processes can be efficiently implemented and regulated.Comment: Main Manuscript part includes 12 pages, 4 figures, 1 table and Supporting Information part includes 20 pages, 8 figures, 1 tabl

About the amplification factors in organic bioelectronic sensors

A systematic comparison between electrochemical and organic bioelectronic sensors reveals a unified rational description for a transistor amplified detection

Correction: Printed, cost-effective and stable poly(3-hexylthiophene) electrolyte-gated field-effect transistors

Correction for 'Printed, cost-effective and stable poly(3-hexylthiophene) electrolyte-gated field-effect transistors' by Davide Blasi et al., J. Mater. Chem. C, 2020, DOI: 10.1039/d0tc03342a

Diagnosis, treatment and prevention of pediatric obesity: consensus position statement of the Italian Society for Pediatric Endocrinology and Diabetology and the Italian Society of Pediatrics

The Italian Consensus Position Statement on Diagnosis, Treatment and Prevention of Obesity in Children and Adolescents integrates and updates the previous guidelines to deliver an evidence based approach to the disease. The following areas were reviewed: (1) obesity definition and causes of secondary obesity; (2) physical and psychosocial comorbidities; (3) treatment and care settings; (4) prevention.The main novelties deriving from the Italian experience lie in the definition, screening of the cardiometabolic and hepatic risk factors and the endorsement of a staged approach to treatment. The evidence based efficacy of behavioral intervention versus pharmacological or surgical treatments is reported. Lastly, the prevention by promoting healthful diet, physical activity, sleep pattern, and environment is strongly recommended since the intrauterine phase

Synthesis and Characterization of Imprinted {TiO}2 Nanoparticles: Preliminary results

The synthesis of TiO2 nanoparticles (TiO2-NPs) in the presence of a target analyte (l-tyrosine) has been developed to prepare imprinted nanostructured materials. The effective growth of TiO2-NPs and their size distribution in stable dispersions has been evaluated by HRTEM analysis. UV-Vis spectroscopic characterization has been performed to study interactions between TiO2-NPs and l-tyrosine

Synthesis of a Molecularly Imprinted Polymer for Dioxin

Abstract: A molecularly imprinted polymer for recognising selectively 2,3,7,8tetrachlorodibenzodioxin (TCDD) was made by a new non-covalent method employing a “dummy ” template. The proposed way represents a simplification of a synthetic scheme proposed by Lübke et al.[1] for covalent imprinting. Comparison of extraction yields of the novel polymer, a non imprinted polymer and an imprinting polymer, prepared by the original procedure demonstrates the binding capacity of the proposed polymer, which is in principle applicable to solid phase extraction (SPE) of dioxin