The RF-AP setup was applied also to Thermofisher Expi293F cells expressing the mNeonGreen monomeric fluorescent protein -the aim here being to demonstrate, via plasma exposure and MSI, the differentiation of cell lysate containing one single 'native' protein from control lysates of the same cell type but which do not express this protein. In this instance, transfected and control cells were washed three times with ammonium acetate, then lysed through repeated freeze-thaw cycles using a -80°C freezer. The lysate was applied to microscope slides, exposed to the RF argon plasma for one minute, then dissolved and filtered before direct injection-ESI analysis. This analysis workflow revealed peaks which were present in the transfected cell lysate which had been exposed to the argon plasma, but were absent in the unexposed mNeonGreen cell lysate and in the exposed control cell lysate (Supplementary 2 & 6). These results were replicated by analysis of the exposed lysates via MALDI imaging, showing localised peak generation (Figure ). The argon plasma setup was subsequently applied to tissue samples. Four mouse kidney samples were washed of lipids by submersion for 30 seconds in 25 mL 70:30 ethanol:water twice, once for 15 seconds in 25 mL 100% ethanol, once for 10 seconds in 25 mL 90:9:1 ethanol:glacial acetic acid:water, and then twice for 2 seconds in 25 mL water. 1 µL of 1 ug/mL mNeon-Green standard was applied to two of the tissues and the RF argon plasma was applied to one control tissue and one spiked tissue for 1 minute each. 7 mg/mL CHCA was then applied to the slides as a matrix and the slides were analysed by MALDI (Figure ). In this manner we were able to not only differentiate plasma-exposed lysates from non-exposed lysates, but were also able to differentiate mNeonGreen standard spiked onto a tissue sample from both exposed unspiked controls and unexposed spiked samples (Figure ). Four intense and relevant peaks -distinguishable between the plasma-exposed standard and the controls -were noted at m/z 158.11, 189.16, 203.17, and 204.17. The m/z 204 peak is likely the C isomer of the m/z 203 peak, which is singly charged.