## 3 Results and Discussion
### Changes in Lipids Associated with Cell Membranes  
We first focused on investigating the changes in lipids associated with the cell membrane. Four classes of lipids predominate in the cell membrane of many mammalian cells: PC, PE, phosphatidylserine (PS), and sphingomyelin (SM). PC, PE, and PS fall under the category of GP, while SM is classified as SP. Other lipids contributing to cell membrane formation include hexosylceramide and ganglioside, both belonging to the SP category, along with cholesterol [20]. In our study, all of the cell membrane-associated GP were detected in both sets of samples. Of the SP category, SM, GM3, monohexosylceramide (Hex1 Cer) and dihexosylceramide (Hex2 Cer) were detected (Tables 2 and 3). However, cholesterol was not detected. This could be due to the fact that cholesterol abundance in epithelial cells is low and it shows poor ionization efficiency under electrospray ionization conditions [21]. In our study, it was found that PC constituted approximately 80% of all GP comprising the cell membrane, with PE, PS, and PI following in decreasing order of abundance (Tables 2 and 3). Our results are consistent with those previously published. It has been evidenced by numerous studies that PC is the most abundant and PE is the second most abundant GP in all mammalian cells [22]. Additionally, SM comprised roughly 5-7% of the total cell membrane lipids and was the most abundant species within the SP category (Tables 2 and 3). \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Lipid Categories**} & \multirow{2}{*}{**Lipid Class**} & \multicolumn{3}{c}{**Number of Species Detected**} \\ \cline{3-4}  & & **Set A** & **Set B** \\ \hline \multirow{3}{*}{Glycerolipids (GL)} & Monoglycerides (MG) & 9 & 14 \\ \cline{2-4}  & Diglycerides (DG) & 96 & 86 \\ \cline{2-4}  & Triglycerides (TG) & 335 & 218 \\ \hline \multirow{9}{*}{Glycerolphospholipids (GP)} & Phosphatidic acid (PA) & 1 & 1 \\ \cline{2-4}  & Phosphatidylcholine (PC) & 461 & 463 \\ \cline{2-4}  & Phosphatidylethanolamine (FE) & 257 & 258 \\ \cline{2-4}  & Phosphatidylserine (PS) & 92 & 71 \\ \cline{2-4}  & Phosphatidylinositol (PI) & 67 & 78 \\ \cline{2-4}  & Phosphatidylglycerol (PG) & 29 & 21 \\ \cline{2-4}  & Lysophosphatidylcholine (LPC) & 50 & 49 \\ \cline{2-4}  & Lysophosphatidylethanolamine (LPE) & 15 & 29 \\ \cline{2-4}  & Lysophosphatidylinositol (LPI) & 1 & 1 \\ \cline{2-4}  & Cardiolipin (CL) & 16 & 17 \\ \hline \multirow{9}{*}{Sphingolipids (SP)} & Ceramide (Cer) & 149 & 139 \\ \cline{2-4}  & Sphingomyelin (SM) & 63 & 63 \\ \cline{2-4}  & Monohexosylceramide (Hex1 Cer) & 25 & 8 \\ \cline{2-4}  & Dihexosylceramide (Hex2 Cer) & 9 & 20 \\ \cline{2-4}  & Sphingosine (SPH) & 7 & 7 \\ \cline{2-4}  & Gangliosides (GM3) & 4 & 2 \\ \hline Sterol lipids (ST) & Cholesteryl ester (CE) & 35 & 28 \\ \hline Preenol lipids (PL) & Coenzyme Q (CoQ) & 3 & 4 \\ \hline Total number of lipid species & 1724 & 1577 \\ \hline \end{tabular}
\end{table} 
Table 1: Lipid categories and classes detected in set A and set B cell samples. Following microplasma irradiation, there was a significant (\(p<0.05\)) increase in total cell membrane lipids within 10 min (A4K0H cells) compared to the control (Figure 2a). Initially, we hypothesized that with further incubation at 37 \({}^{\circ}\)C (with 5% CO\({}_{2}\)) for 1 h post-irradiation, the lipid levels would revert to those of the control group. Contrary to our expectations, even after 1 h of incubation (A4K1H cells), the total cell membrane lipids remained significantly elevated. Notably, among the GP category, PS levels showed the highest increase, approximately 50%, and this elevation persisted during the post-irradiation incubation. PC, PE and PI levels showed similar patterns--they increased in A4K0H cells and then started to decrease in A4K1H cells (Figure 2c). The changes in PC and PE levels were very similar, both experiencing approximately 30% increases in A4K0H cells (Figure 2c). Two SP classes, SM and Hex1 Cer, were increased by approximately 40% in A4K0H cells compared to the control.