"Nanoantibiotics": a new paradigm for treating infectious diseases using nanomaterials in the antibiotics resistant era.

Endometriosis

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

Paper spray for direct analysis of complex mixtures using mass spectrometry.

A low-temperature plasma (LTP) probe has been developed for ambient desorption ionization. An ac electric field is used to induce a dielectric barrier discharge through use of a specially designed electrode configuration. The low-temperature plasma is extracted from the probe where it interacts directly with the sample being analyzed, desorbing and ionizing surface molecules in the ambient environment. This allows experiments to be performed without damage to the sample or underlying substrate and, in the case of biological analysis on skin surfaces, without electrical shock or perceptible heating. Positive or negative ions are produced from a wide range of chemical compounds in the pure state and as mixtures in the gaseous, solution, or condensed phases, using He, Ar, N2, or ambient air as the discharge gas. Limited fragmentation occurs, although it is greater in the cases of the molecular than the atomic discharge gases. The effectiveness of the LTP probe has been demonstrated by recording characteristi...

Low-temperature plasma probe for ambient desorption ionization.

https://link.springer.com/content/pdf/10.1016%2Fj.jasms.2009.07.025.pdf

What can we learn from ambient ionization techniques

Electrospray ionization (ESI) is a mass spectrometric technique widely used in various fields including chemistry, biology, medicine, pharmaceutical industry, clinical assessment, and forensic science. In this study, we report a simple and economical ESI-mass spectrometry (MS) technique, which makes use of disposable wooden tips (wooden toothpicks) for loading and ionization of samples. Samples could be loaded by normal pipetting onto the tip or simply dipping the tip into sample solutions. The hydrophilic and porous nature of wood allows effective adhesion of the sample solution for durable ion signals. The tip can be directly connected to nano-ESI ion sources of various mass spectrometers. Upon application of high voltage to the tip, desirable mass spectra could be obtained. We demostrated that this new technique is applicable for analysis of various samples, including organic compounds, organometallic compounds, peptides, proteins, and samples that cannot be directly analyzed by conventional ESI techni...

Electrospray Ionization Using Wooden Tips

Quantitative analysis of trace constituents in exhaled gas can provide useful insights into biochemical processes in the body, thus revealing information about metabolic dynamics and providing, theoretically, a scientific base for biomarker research or clinical diagnoses. 9] Breath, however, is rarely used practically for diagnostic purposes in clinical medicine because of analytical difficulties. 8] Numerous attempts have been made for fast breath analysis by using methods that include proton transfer reaction mass spectrometry (PTR-MS), selected ion flow tube (SIFT) mass spectrometry, and exhaled breath condensate (EBC) analysis, 13,14] the latter being based on chromatographic separation. However, these methods require tedious sample collection and sample pretreatment procedures. PTR-MS and SIFT-MS have been used for direct breath analysis, but require specially designed instruments that are not widely available. To date, only lowmolecular-weight compounds (up to ca. 100 Da), almost exclusively volatile species, have been detected in breath. With the exception of SIFT-MS, measurements are also compromised by the high water content in breath. 3,8] Actually, breath is a type of aerosol, and, in addition to volatile constituents, contains a vast variety of nonvolatile compounds dissolved in the microdroplets. We herein report an extractive electrospray ionization (EESI) quadrupole time-of-flight mass spectrometry (QTOF-MS) method that has been established without modification of a commercial ESI interface (shown schematically in Figure 1) for the rapid in vivo fingerprinting of human breath. It presents a direct way to probe the dynamics of body metabolism and a simple, experimentally convenient method for the fast clinical diagnosis of oral malodors, based on Figure 1. Schematic illustration of the concept and setup of EESIQTOF-MS. I: desolvation gas inlet, used for sampling of breath; H: heating region in the desolvation gas outlet; HV=high voltage; QTOF=quadrupole time-of-flight; breath compounds are ionized in the region between the ESI spray and the breath stream. Note the intrinsic flexibility of EESI allows ambient ion/molecule reactions, including—but not limited to—protonation and cationization.

Rapid in vivo fingerprinting of nonvolatile compounds in breath by extractive electrospray ionization quadrupole time-of-flight mass spectrometry.

Neutral Desorption Sampling of Living Objects for Rapid Analysis by Extractive Electrospray Ionization Mass Spectrometry

Ambient mass spectrometry, pioneered with desorption electrospray ionization (DESI) technique, is of increasing interest in recent years. In this study, a corona discharge ionization source is adapted for direct surface desorption chemical ionization of compounds on various surfaces at atmospheric pressure. Ambient air, with about 60% relative humidity, is used as a reagent to generate primary ions such as H(3)O(+), which is then directed to impact the sample surface for desorption and ionization. Under experimental conditions, protonated or deprotonated molecules of analytes present on various samples are observed using positive or negative corona discharge. Fast detection of trace amounts of analytes present in pharmaceutical preparations, viz foods, skins and clothes has been demonstrated without any sample pretreatment. Taking the advantage of the gasless setup, powder samples such as amino acids and mixtures of pharmaceutical preparations are rapidly analyzed. Impurities such as sudan dyes in tomato sauce are detected semiquantitatively. Molecular markers (e.g. putrescine) for meat spoilage are successfully identified from an artificially spoiled fish sample. Chemical warfare agent stimulants, explosives and herbicides are directly detected from the skin samples and clothing exposed to these compounds. This provides a detection limit of sub-pg (S/N > or = 3) range in MS2. Metabolites and consumed chemicals such as glucose are detected successfully from human skins. Conclusively, surface desorption atmospheric pressure chemical ionization (DAPCI) mass spectrometry, without toxic chemical contamination, detects various compounds in complex matrices, showing promising applications for analyses of human related samples.

Huanwen Chen

Papers

What can we learn from ambient ionization techniques

Electrospray Ionization Using Wooden Tips

Rapid in vivo fingerprinting of nonvolatile compounds in breath by extractive electrospray ionization quadrupole time-of-flight mass spectrometry.

Neutral Desorption Sampling of Living Objects for Rapid Analysis by Extractive Electrospray Ionization Mass Spectrometry

Surface desorption atmospheric pressure chemical ionization mass spectrometry for direct ambient sample analysis without toxic chemical contamination.