## 6 Biomedical Applications of NTP on Biofilm  
A wide variety of research has been published on the use of NTP in biofilm treatment [123; 53; 51; 62; 53; 61] with the help of different plasma systems such as corona discharge, microwave discharges, plasma jet, gliding arc, and dielectric barrier discharge within the past few years. The literature published in 2015 by [PERSON] et al. demonstrated complete inactivation of _Staphylococcus aureus_ biofilms that was grown on borosilicate slices placed in the 24-well plates for 12 h [49]. They used atmospheric pressure plasma jet (APPJ) with helium as a working gas at 6.7 standard liters per minute (SLM) flow rate. Within 10 min of plasma treatment, the reduction in biofilm cells was found to be more than 99.9% in comparison to the untreated biofilm samples. The effect of plasma treatment on biofilm was observed using a confocal microscope, exhibiting many dead bacteria on the biofilm upper layer in comparison to the bottom layer. Further, intra-bacterial ROS in the biofilm was detected by ROS monitoring probe 2, 7-dichlorhydrofluorescein diacetate (DCFH-DA). Their findings also provide insight into the mechanism of biofilm inactivation by plasma reactive species and plasma-induced intracellular ROS. [PERSON] et al. in 2013 studied the antimicrobial efficacy of two surface barrier discharges (SBD) known as SBD-A (structured electrode planar SBD) and SBD-B (a wire electrode SBD), with air plasma in _Pseudomonas aeruginosa_ and _Staphylococcus epidermidis_ biofilms. The biofilm was grown on polycarbonate discs placed into microplate wells for 48 h and treated with plasma from 30-600 s. They achieved a colony reduction factor (CRF) of 7.1 log\({}_{10}\) and 3.81 log\({}_{10}\) for _P. aeruginosa_ by SBD-A andSBD-B plasma. Whereas for _Staphylococcus epidermidis_, CRF of 3.38 log\({}_{10}\) and 2.69 log\({}_{10}\) were found out by SBD-A and SBD-B plasma at 600 s of plasma exposure. The study used a positive control as CHX that is used as a treatment for dental biofilm and found around 1 log reduction in biofilm cells. Furthermore, in a similar study, the cytotoxicity of the plasma system was tested on a mouse fibroblast cell line concluding that the average viability of the cells did not decrease below 50% until 150 s of plasma exposure time [53]. Non-thermal plasma has also been used widely in dentistry to remove dental biofilms. A 2014 study used positive corona (PC) and negative corona (NC) discharges on biofilm contaminated teeth surfaces and tested the effect of water electro-spraying for decontamination [60]. Both discharges were able to reduce the biofilm cell concentration by 1-1.3 orders of magnitude and 2.73 logs in 5 and 10 min of plasma treatment time. In addition, 3.16 orders of biofilm cell reduction were achieved after water electro-spraying through the plasma. The impact of those discharges on tooth surfaces was also studied by FTIR and SEM, but no significant changes were observed. In 2010 and 2011 [PERSON] et al. used three plasma devices named as atmospheric pressure plasma jet, a hollow dielectric barrier discharge electrode (HDBD) and a volume dielectric barrier discharge (VDBD) against dental biofilms. Their results showed log reduction of 5.38 and 5.67 for _Streptococcus mutans_ (_S. mutans_) and saliva biofilm when compared with the CHX as a control which shows a reduction of 3.36 and 1.50 for _S. mutans_ and saliva biofilm [31]. They also achieved 5 log reduction of _Candida albicans_ biofilm cells and suggested the plasma to be more effective than CHX in the treatment of single and multispecies dental biofilms. In comparison to the plasma treated biofilm that has a 5 log reduction, the chemical antiseptics such as CHX or NaOCl had a reduction factor of 1.5, suggesting that this plasma can be used as an alternative to chemical antiseptics for dental practice [54]. This study concluded the plasma could be used as an alternative to chemical antiseptics for dental applications.