Development of tip-desorption electrospray ionization coupled with ion mobility-mass spectrometry for fast screening of carbapenemase-producing bacteria

A high-throughput platform enables in situ screening of fatty acid-producing strains using laser ablation electrospray ionization mass spectrometry and a Python package

Microbial fatty acid-producing strains are commonly engineered to improve their performance for industrial applications. However, it is challenging to efficiently and rapidly screen target strains for engineering. This study reported an in situ analytical platform using laser ablation electrospray ionization mass spectrometry (LAESI-MS) for fast profiling of triacylglycerols in cellular lipid droplets of Aurantiochytrium sp. colonies cultured on agar plates. LAESI-MS approach allowed for the direct acquisition of a colony cell's characteristic fingerprint mass spectrum and MS/MS facilitated the identification of triacylglycerol species containing three fatty acyl groups. The fatty acid contents of colony cells were calculated based on the intensities of triacylglycerols from their characteristic fingerprint mass spectrum. A Python package called TAFA-LEMS (Triacylglycerol to Fatty Acid by LAESI-MS) was also developed to process the high-throughput MS data and extract fatty acid contents in colony cells. The results demonstrated that the LAESI-MS platform is fast, stable, and reproducible, with a data acquisition rate of ≤2 s per sampling point and ≤13.69% RSDs of the relative contents of fatty acids. In addition, LAESI-MS was successfully performed on the analysis of P. tricornutum and Y lipolytica strains. This in situ MS platform has the potential to become a common biotechnology platform for microbial strain engineering.

Automated high-throughput characterization of microbial metabolites and species using array ballpoint electrospray ionization technique

RATIONALE

Microbial metabolites are widely used in agriculture, food, environment, and medicine. However, there is a lack of high-throughput, nonclogging, and simple methods for the identification of microbial metabolites and their subspecies using ambient mass spectrometry (MS). Here, we proposed a method for analyzing the microbial metabolites and identifying their species using the array ballpoint electrospray ionization (aBPESI) technique.

METHODS

The previously developed BPESI was combined with the array analysis technique to form a high-throughput analysis technique called aBPESI. The bacteria cultured on the plate medium were directly analyzed using MS with aBPESI. Principal component analysis-linear discriminant analysis (PCA-LDA) algorithm was used to analyze the different subspecies groups.

RESULTS

The results showed that aBPESI was capable of completing a sample analysis within 30 s, and the level of metabolite detection was comparable to existing techniques. The accuracy of bacterial subspecies identification was 90% (Pseudomonas aeruginosa) and 100% (Serratia marcescens).

CONCLUSIONS

A new high-throughput and robust MS technique aBPESI was proposed. It does not require sample pretreatment and greatly reduces the sample analysis time. aBPESI shows a strong ability in microbial analysis and is expected to be further applied in other research fields.

Electrospray ionization mass spectrometry with wooden tips: A review

Electrospray ionization (ESI) is a powerful ionization technique in mass spectrometry (MS). There has been an increasing interest for the new development of ESI technique to extend its applications. ESI-MS with wooden tips (wooden-tip ESI-MS), an ESI technique invented in 2011, enabled not only new applications but also new insights into the ESI mechanism. In this review, the technical aspects of wooden-tip ESI-MS are described, the new features of wooden-tip ESI-MS for sampling and ionization of analytes are highlighted, and the important applications of wooden-tip ESI-MS in various fields in the past 10 years, including food safety, forensic investigation, environmental analysis, biomedical analysis and protein study, are summarized. The perspectives on the further development and applications of wooden-tip ESI-MS are also discussed.

Fast-switching high-voltage porous-tip electrospray ionization mass spectrometry for rapid detection of antirheumatic drugs in adulterated herbal dietary supplements

RATIONALE

Herbal dietary supplements (HDSs) adulterated with undeclared synthetic drugs can lead to serious health problems METHODS: A fast-switching positive/negative high-voltage (+/- HV) was developed to apply on electrospray ionization mass spectrometry (ESI-MS) with porous tips for rapid screening of five antirheumatic drugs in antirheumatic HDSs. The fast-switching (switch-time: 100 ms) negative and positive ions were alternately generated to perform full-MS and tandem-MS analysis, providing an effective method for rapid detection of analytes in whichever mode of detection was most suitable (negative or positive ion mode). The use of different tips and solvents was also optimized in this work.

RESULTS

The limits of detection of the five antirheumatic drugs were found to be less than 0.1 ng/g (S/N > 3). The reproducibility of the five drugs was measured to be 10.0-23.3% (n = 5). A single sample analysis could be completed within 1 min. Rapid screening of a total of 28 real HDS samples collected from the market was examined by the fast-switching HV substrate-tip ESI-MS method, and the screening result was further validated by conventional liquid chromatography/mass spectrometry.

CONCLUSIONS

Overall, our results demonstrated that fast-switching HV substrate-tip ESI-MS is a rapid, reliable, and effective method for simultaneous screening of various analytes in complex samples.

Vibrating tip spray ionization mass spectrometry for direct sample analysis

In this work, a vibrating tip spray ionization source was developed for direct mass spectrometric analysis of raw samples under voltage-free condition. A solid tip was mounted on a vibrator, and the solid tip was placed on the front of MS inlet. Liquid, viscous, and bulk solid samples could be directly loaded on the tip-end surface, and then a drop of solvent at microliter level was subsequently loaded on the tip for dissolution and extraction of analytes, and a vibrator was then started to atomize and ionize the analytes under ambient condition. We demonstrated vibrating tip spray mass spectrometry in various applications, including food safety, pharmaceutical analysis, and forensic science. Furthermore, in situ analysis of biological tissues and in vivo analysis of living plants were conveniently performed, due to voltage-free. Different vibration frequencies and solvent compositions were investigated. The analytical performances, including sensitivity, reproducibility, and linear range, were investigated. The ionization process and mechanism were also discussed in this work.