Effect of the pH on the Antibacterial Potential and Cytotoxicity of Different Plasma-Activated Liquids

Abstract

In this study, different plasma-activated liquids were evaluated for their antimicrobial effects against Escherichia coli, as well as for their cytotoxicity on mammalian cells. The PALs were prepared from distilled (DIS), deionized (DI), filtered (FIL), and tap (TAP) water. Additionally, 0.9% NaCl saline solution (SAL) was plasma-activated. These PALs were prepared using 5 L/min air gliding arc plasma jet for up to 60.0 min of exposure. Subsequently, the physicochemical properties, such as, the oxidation-reduction potential (ORP), the pH, the conductivity, and the total dissolved solids (TDS) were characterized by a water multiparameter. The PALs obtained showed a drastic decrease in the pH with increasing plasma exposure time, in contrast, the conductivity and TDS increased. In a general trend, the UV-vis analyses identified a higher production of the following reactive species of nitrogen and oxygen (RONS), HNO2, H2O2, NO3−, and NO2−. Except for the plasma-activated filtered water (PAW-FIL), where there was a change in the position of NO2− and NO3− at some pHs, The higher production of HNO2 and H2O2-reactive species was observed at a low pH. Finally, the standardized suspensions of Escherichia coli were exposed to PAL for up to 60.0 min. The plasma-activated deionized water (PAW-DI pH 2.5), plasma-activated distilled water (PAW-DIS pH 2.5 and 3), and plasma-activated tap water (PAW-TAP 3.5) showed the best antimicrobial effects at exposure times of 3.0, 10.0, and 30.0 min, respectively. The MTT analysis demonstrated low toxicity of all of the PAL samples. Our results indicate that the plasma activation of different liquids using the gliding arc system can generate specific physicochemical conditions that produce excellent antibacterial effects for E. coli with a safe application, thus bringing future contributions to creating new antimicrobial protocols.

Effect of Plasma On-Time with a Fixed Duty Ratio on Reactive Species in Plasma-Treated Medium and Its Significance in Biological Applications

“…The pH of the PTM remained unchanged after NTAPP, which is identical to our results [ 46 , 47 ]. The DMEM has the capacity to maintain the pH and temperature of the PTM [ 48 ]. Despite whether the effects of the plasma are direct or indirect, the right amount of time must be allowed for irradiation.…”

A review on plasma‐activated water and its application in the meat industry

“…In contrast, the concentrations of nitrite and nitrate in PAW prepared with tap water were unaffected by the storage time (Figure 8b) because of the absence of acidification and the buffer effect of carbonates in tap water (Wartel et al., 2021). Moreover, it was reported that PAW (pH = 3.5) prepared from tap water performed the best inactivation efficacy against E. coli compared to distilled, deionized, filtered, and saline water as shown in Figure 9 (Sampaio et al., 2022).…”

“…Overview of the antibacterial effects of Escherichia coli exposure in contact with plasma-activated water prepared from distilled, deionized, filtered, 0.9% saline and tap water over time at pH = 3.5. Reproduced fromSampaio et al (2022) with the permission of MDPI.…”

Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet

“…APPJs generate plasma plumes in open spaces, enabling the direct treatment of samples of different shapes and sizes [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. Over the years, APPJs have been successfully tested in many applications, such as material treatment, sterilization, cancer and wound treatment, aesthetic applications, and dentistry [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. Many different configurations of APPJs are reported in the literature.…”