Ion Addition by Electrolysis to Improve the Quantitative Analysis of Bacteria with MALDI-TOF MS

Abstract

Matrix-assisted laser desorption/ionization time-offlight mass spectrometry (MALDI-TOF MS) is commonly applied to the identification of bacteria but rarely used for quantitative detection due to the inhomogeneous crystallization of the matrix leading to the unsatisfactory linear relationship between the sample amount and the mass spectrum signals. Herein, we proposed a noninterference ion addition (NIA) method by electrolysis to improve homogeneous crystallization during the evaporation progress of sample droplets on the target plates. The active metal wire was inserted in the droplet as the anode electrode, and metal ions were released through electrolysis. The directional migration of metal ions under the electric field can hinder the migration of matrix molecules to the boundary and homogenize the matrix crystals by forming spherical crystals. Simultaneously, trace cationic surfactant was added to the droplet for pinning the contact surface to define the circle crystallization region. The metal ions from the anode electrode wire were deposited on the surface of the target plates which served as the cathode. Therefore, ion addition has no interference effect on ionization during MALDI-MS detection. This NIA method benefits the homogeneous crystallization and so improves the quantitative analysis. NIA is suitable for biological samples with different matrices, and bacterial samples could be quantitatively analyzed.

Rapid Detection of Broad-Spectrum Pathogenic Bacteria Based on Highly Sensitive Proton Response of the Nucleic Acid Amplification SPQC Platform

“…2,3 Time-of-flight mass spectrometry provides faster bacterial identification but necessitates pure cultured bacteria and expensive equipment, hindering point-of-care testing (POCT). 4,5 Furthermore, immunological methods pose challenges due to low detection sensitivity and difficulties in procuring monoclonal antibodies. 6,7 Nucleic acid-based molecular biology methods such as gene sequencing demand bulky instruments and trained operators, restricting their application to centralized laboratories.…”

“…The culture method continues to be the gold standard for the clinical detection of bacteria in hospitals. However, this method has significant limitations including a slow process time, low detection rates, which are a result of generational time delay, and the inability to cultivate certain bacteria. , Time-of-flight mass spectrometry provides faster bacterial identification but necessitates pure cultured bacteria and expensive equipment, hindering point-of-care testing (POCT). , Furthermore, immunological methods pose challenges due to low detection sensitivity and difficulties in procuring monoclonal antibodies. , Nucleic acid-based molecular biology methods such as gene sequencing demand bulky instruments and trained operators, restricting their application to centralized laboratories. , Despite the ongoing evolution of molecular hybridization, , DNA chips, , and nucleic acid biosensors, , technologies are advancing toward expedited response, reduced costs, and simplified miniaturization, the absence of a universal target compels patients with bacterial infections to undergo a complex pathogen identification procedure, thus delaying treatment.…”