Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry As a Rapid and Reliable Technique for Directly Evaluating Bactericidal Activity: Probing the Critical Concentration of ZnO Nanoparticles As Affinity Probes

摘要

The present study was undertaken because ZnO is beingnused as affinity probes for enhancing the signal intensitiesnof bacterial analytes. Since, ZnO is established for itsnbactericidal activity, it is vital that the threshold concentrationsnup to which ZnO does not show bactericidalnactivity and above which concentration the bactericidalnactivity of ZnO becomes pronounced is identified. Thenresults showed that at concentrations below 10 g/L, suchnas 5 and 1 g/L ZnO NPs did not damage the E. coli cellsnmuch but improved the intensity of most of the peaks innthe spectra. For the first time, this paper reports the usenof matrix-assisted laser desorption ionization-time-of-flightnmass spectrometry (MALDI-TOF MS) for assessing thendamage incurred on the bacterial cells. The resultsnshowed significant differences in spectral pattern confirmingnthat MALDI-TOF MS was successful in evaluating thenbactericidal activity. This paper is unique in that itnpresents the results of the comparative study conductednin assessing the capability of MALDI-TOF MS with thenexisting conventional plating technique which is generallynused to estimate bactericidal activity. This study bringsnout the inadequacy of the conventional plating techniquesnused in microbiology to depict antibacterial activity. Onnthe other hand, MALDI-MS analysis led to direct, simple,nand rapid acquisition of data (5 min for each measurement)nwhich promptly reflected the bactericidal activity.