Neutral Desorption Extractive Electrospray Ionization Research Articles

Unveiling the Antibacterial Mechanism of Gold Nanoparticles by Analyzing Bacterial Metabolism at the Molecular Level.

The threat of drug-resistant bacteria is challenging, and it is urgent to explore new antibiotics. Gold nanoparticles (AuNPs) are known to be a group of promising antibacterial agents for replacing conventional antibiotics. Nevertheless, their antibacterial mechanism remains to be elucidated. Herein, we directly observed the interaction between antibacterial AuNPs and bacteria at the molecular level using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS). We monitored and analyzed the dynamic changes of bacterial metabolites in real time after AuNP treatment. Ten substances representing 3 major metabolic pathways, including protein and nucleic acid synthesis, energy metabolism, and quorum sensing, were identified, indicating that AuNPs may exert antibacterial effects through multiple mechanisms influencing bacterial metabolism and communication. This study deepens the understanding of the antibacterial mechanism of AuNPs and is insightful for designing and screening new antibacterial agents.

Direct Analysis of Human Sputum for Differentiating Non-small Cell Lung Cancer by Neutral Desorption Extractive Electrospray Ionization Mass Spectrometry.

Human sputum, a typical highly viscous biosample, was directly characterized at the molecular level using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) without multi-step sample pretreatment, in an attempt to provide a method for constructing the pattern recognition of rapid diagnosis of lung cancer. Under the optimal experiment conditions, glucose, amino acids, phosphoric lipids and other typical analytes in the sputum sample could be used to conduct qualitative or quantitative (in arginine) analysis. More interestingly, the full scan mass spectra from 50 patients of non-small cell lung cancer, recording the mass spectral fingerprints of sputum samples, were differentiated from the control group (50 healthy individuals) through principal component analysis (PCA). These findings suggest that valuable molecular information concealed in human sputum could be easily revealed and applied for conducting qualitative or quantitative analysis by direct ND-EESI-MS analysis.

Altered phosphatidylcholines expression in sputum for diagnosis of non-small cell lung cancer.

Non–small cell lung cancer (NSCLC) is a leading cause of cancer mortality worldwide, and early diagnosis needs to be improved. We examined whether neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) could be used to detect sputum lipids expression changes to enable earlier diagnosis. Overall, 167 NSCLC patients and 140 controls were enrolled. The main peaks in the sputum of patients with NSCLC patients differed from controls (83.3% of total variability), and the signals were not associated with pathological type, TNM stage or smoking history. The relative abundance of peaks at m/z734, m/ z756, m/z772, m/z782, m/z798 and m/z803 reliably distinguished NSCLC sputum from control. Collision-induced dissociation confirmed that m/z734, m/z756, and m/z772 represented [DPPC + H]+, [DPPC + Na]+, and [DPPC + K]+, respectively, and m/z782, m/z798, and m/z803 represented sphingomyelin, phosphatidylglycerol, and phosphatidylglycerolphosphate, respectively. The relative abundance of DPPC was clearly lower in NSCLC sputum than in control, and the relative abundances of phosphatidylglycerol and phosphatidylglycerolphosphate were higher in NSCLC sputum than in control. The detection of changes in sputum lipids with ND-EESI-MS may be a noninvasive, radiation-free, relatively inexpensive, repeatable, and efficient method for diagnosis of NSCLC.

Extractive electrospray ionization mass spectrometry for direct characterization of cosmetic products

As daily necessities in large populations, quality control is mandatory for cosmetic products in order to guarantee their efficacy and safety. Traditionally, analysis of cosmetics is slow due to the dedicated sample pretreatment steps required. With neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS), trace illicit additives including sunscreens, hormones, and antibiotics etc. in many types of cosmetics can be quantitatively detected at sub-low-ppb levels, requiring no sample pretreatment. This review briefly summarizes the technique development and application of ND-EESI-MS for the rapid analysis of cosmetic products. The future trend of ND-EESI-MS for cosmetic analysis is also concisely discussed.

Trace detection of hormones and sulfonamides in viscous cosmetic products by neutral desorption extractive electrospray ionization tandem mass spectrometry

A sensitive method based on a geometry-independent neutral desorption (GIND) in combination with extractive electrospray ionization mass spectrometry (EESI-MS) has been developed for fast detection of illicit additives such as sulfonamides and hormones in highly viscous cosmetic products. The method gave a low limit of detection (LOD) (in the range of 0.001-1 ng/g), acceptable relative standard deviation (RSD=6.8-11.4%) and reasonable recovery (87-116%) for direct measuring of nine types of hormones and sulfonamides in the cosmetic products. The average measurement time for two types of samples was less than 1 min. Trace amounts of analytes in commercial cosmetic products have been quantitatively detected, without any sample pretreatment. The experimental results showed that non-volatile illicit additives such as sulfonamides and hormones could be sensitively liberated using the GIND device for quantitative detection from the highly viscous cosmetic products, demonstrating that GIND-EESI-MS is a promising tool for high throughput, sensitive and quantitative analysis of highly complex viscous samples.

Neutral desorption extractive electrospray ionization mass spectrometry for fast screening sunscreen agents in cream cosmetic products

High throughput analysis of sunscreen agents present in cream cosmetic has been demonstrated, typically 2 samples per minute, using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) without sample pretreatment. For the targeted compounds such as 4-Aminobenzoic acid and oxybenzone, ND-EESI-MS method provided linear signal responses in the range of 1–100ppb. Limits of detection (LOD) of the method were estimated at sub-ppb levels for the analytes tested. Reasonable relative standard deviation (RSD=8.4–16.0%) was obtained as a result of 10 independent measurements for commercial cosmetics samples spiked with each individual sunscreen agents at 1–10ppb. Acceptable recoveries were achieved in the range of 87–116% for direct analysis of commercial cream cosmetic samples. The experimental data demonstrate that ND-EESI-MS is a useful tool for high throughput screening of sunscreen agents in highly viscous cream cosmetic products, with the capability to obtain quantitative information of the analytes.

Rapid characterization of complex viscous samples at molecular levels by neutral desorption extractive electrospray ionization mass spectrometry

In this protocol, the sample (which could be a bulk or heterogeneous fluid, or a greasy surface) is treated with a neutral desorption (ND) sampling gas beam, and the resulting analyte mixtures are directly characterized by extractive electrospray ionization mass spectrometry (EESI-MS). The ND device can be specifically constructed such that the sampling gas beam is bubbled through the liquid sample (microjet sampling) or directed to impact the sample surface (e.g., for the analysis of a material like cheese). The ND-EESI-MS analysis process requires no sample pretreatment because it can tolerate an extremely complex matrix. ND-EESI-MS allows real-time, online chemical profiling of highly viscous samples under ambient conditions. Both volatile and nonvolatile analytes from viscous samples can easily be detected and quantified by ND-EESI-MS, thereby providing an MS-based analytical platform for multiple disciplines (e.g., for the food industry, for drug discovery, and for the biological and life sciences). Here we describe the ND-EESI-MS protocol for viscous sample analysis, including the experimental design, equipment setup, reagent preparation, data acquisition and analysis steps. The data collection process takes <1 min per sample, although the time required for the whole procedure, which largely depends on the experimental preparation processes, might be considerably longer.

Sampling analytes from cheese products for fast detection using neutral desorption extractive electrospray ionization mass spectrometry

The development of analytical techniques suitable for sensitive, high-throughput, and nondestructive food analysis has been of increasing interest in recent years. In this study, mass-spectral fingerprints of various cheese products were rapidly recorded in the mass range of m/z 50-300 Da without any sample pretreatment, using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) in negative ion mode. The results demonstrate that both volatile and nonvolatile analytes on greasy cheese surfaces can be directly sampled by a neutral desorption gas beam. The influence of the neutral desorption gas flow on the analyte signal was systematically investigated. Under optimized experimental conditions, reproducible results were obtained using ND-EESI-MS. Principal component analysis was applied to differentiate a total of 49 individual cheese samples (four different types), which were purchased from three different supermarkets. All samples were successfully classified according to their types; but distributors and sensory properties were not distinguishable from the spectra data. The principal components 2, 3, and 4 scores showed an excellent capacity of distinguishing types of cheese. Molecular markers of interest can be identified using tandem mass spectrometry and matching the data with those from reference compounds. The experimental data show that ND-EESI-MS is able to sensitively and directly detect analytes on greasy surfaces without chemical contamination, providing a convenient method for high-throughput food analysis with a high degree of safety.