## 6 Biomedical Applications of NTP on Biofilm
One of our study [70] showed 2.43 log reduction of biofilm when treated with CHX in compare to more than 3 log reduction after plasma treatment. We also found some disruption of biofilm cells when treated with CHX, however the biofilm destruction caused by plasma was more severe. A 2010 study used glass coverslips for growing biofilm and achieved complete inactivation (7 log reduction) of _Neisseria gonorrhoeae_ biofilm after treating with jet plasma for 20 min [42]. A mixture of helium and oxygen were used as a working gas to generate plasma. In the similar study, the effect of plasma on biofilm was visualized by transmission electron microscopy (TEM). The images show disruption and damage to the cell wall and dispersed nucleoid region. In 2014, [PERSON] et al. established complete inactivation of _Pseudomonas aeruginosa_ biofilm after 30 min of plasma jet treatment. The biofilm in this study was grown for 24 h on borosilicate glass coupons under continuous culture system [56]. Their atomic force microscopy (AFM) results show significant loss of the biofilm structure when treated with plasma for a longer time. They also concluded that changes in biofilm structure that leads to the loss of culturability and viability are related to a decrease of the biofilm matrix adhesiveness. Similarly, [PERSON] et al. claimed 100% inactivation of the _P. aeruginosa_ biofilm cells after 5 min of applying plasma jet. They used batch culture to grow \(1,3\), and 7 day old biofilm on borosilicate glass coupons [62]. They also showed a decrease in adhesiveness to borosilicate and biofilm thickness after plasma treatment by AFM. Another study by [PERSON] et al. in 2012 achieved complete eradication and more than 4 log (99.99%) reduction in the number of biofilm cells when treated with 40 and 20 kHz plasma jets. Their confocal microscopy results indicate this from the biofilm thickness after 240 s of plasma treatment suggesting the penetration of reactive species into the biofilm inner layer. This study demonstrated the potential to completely remove biofilms formed on inanimate surfaces employed in the manufacture of indwelling medical devices [3]. Similarly, another study in 2012 showed 6 log reduction of _Candida albicans_ biofilms after treating with surface micro-discharge (SMD) plasma for 8 min. This contact-free application of plasma to kill biofilm cells could be beneficial for the eradication of nosocomial infections in hospital settings [55]. [PERSON] et al. in 2017 evaluated the bactericidal effects of non-thermal argon/oxygen plasma on _S. mutans_ and/or _S. sanguinis_ biofilms [124]. The 7 days old biofilm grown on 48-well plate showed 99% of bacterial cells reduction after 2 min plasma treatment. Their study further suggested the virulence properties of _A. oris_ by altering its hydrophobicity and capability to co-aggregate with _S. sanguinis_. A study by [PERSON] et al. in 2018 used a novel argon plasma-activated gas (PAG) for the treatment of different biofilm species such as _S. aureus_, _P. aeruginosa_, and _E. coli_. These biofilms were grown on polytetrafluoroethylene channel segments similar to the GI endoscopic channels for 48 h and treated with PAG for 9 min. Their results demonstrated effective killing of biofilm (8 log reduction) that have a potential alternative to the high-level disinfectants (HLDs) and/or ethylene oxide in the endoscope reprocessing procedure [125]. A study by [PERSON] et al. in 2018 investigated the ability to disrupt and limit biofilms growth of _P. aeruginosa_ by helium cold atmospheric pressure plasma (CAP) jet. 4-5 log reduction in viable bacterial cells were found when 8 h grown biofilms were treated with plasma, whereas only 2 log reduction were achieved after treating biofilms grown for 12 h. The plasma treatment time was 5 min. This study concludes that using CAP in a time-dependent manner is important for reducing the formation of biofilms [126]. Another interesting study by [PERSON] et al. in 2018 used helium porous plasma jet on _P.