(OH)2_MgSO4, were tested for their antibacterial potential (Pan et al. 2013). The

outcomes of the study demonstrated that the Mg (OH)2_MgSO4 NPs were readily

absorbed and inbound onto the bacterial cell as compared to the Mg (OH)2_MgCl

NPs. This facile interaction can be ascribed based on charged moieties present on the

surface of the NPs. The Mg (OH)2_MgSO4 had a positive charge on their corona

hence were able to form ionic interactions with the charged bacterial cell wall. On

the other hand, the Mg (OH)2_MgCl NPs were negatively charged owing to which

the electrostatic repulsive forces dominated and the NPs were unable to interact with

the negatively charged bacterial cell (Pan et al. 2013).

It has also been portrayed that the accumulation of positively charged (cationic)

NPs can lead to inhibited cell growth and colonization. Another factor, which came

into a light, was that the abundant accumulation of cationic NPs resulted in a

restricted bacterial adhesion. The abovementioned fact was corroborated by the

findings of the study conducted by Fang et al. (2015). They elucidated the underly-

ing mechanism behind the bactericidal effects produced by cationic NPs. The study

pointed out that ion exchange resulted in deeper penetration of these NPs across the

bacterial cell envelope, thus establishing direct communication with the cellular

components. This interaction among the particles and cellular bodies was thought

to be responsible for evoking a bactericidal response (Fang et al. 2015). Apart from

this, it has also been hypothesized that the production of ROS entities is also

significantly enhanced in the presence of positively charged NPs (Wang et al.

2017). This escalated level of ROS production finally allows the bacteria to meet

their final fate, i.e., cell lysis and apoptosis.

11.3

Nanoparticles’ Mode of Action for Combating Bacterial

Resistance

A number of mechanisms have been proposed for elucidating the role of NPs in

overcoming bacterial resistance. Among them, the first and foremost types of NPs

are those which tend to display numerous modes of action in a simultaneous order

(Pelgrift and Friedman 2013). The generation of these simultaneous mechanisms

will prove to be highly beneficial as multiple gene mutations will be required in the

same bacteria to evoke defense mechanism which is deemed to be highly unlikely

possible (Blecher et al. 2011; Huh and Kwon 2011; Knetsch and Koole 2011;

Schairer et al. 2012). Apart from this, another strategy, which has been seamlessly

used, is the simultaneous entrapment of several antibiotics within the corona of

nanoparticles and delivering the active payload cargo to the target bacterial site

(Blecher et al. 2011; Zhang et al. 2010). It is a well-versed fact that a significant

antibacterial activity can only be attained when direct contact between the NPs and

the bacterial cell is maintained (Wang et al. 2017).

NPs possess several alluring physicochemical, biological, and mechanical

properties of diverse nature, which provides them with an intrinsic ability to estab-

lish effective interaction with the target site (cell wall)/pathogens (Farouk et al.

2018). This specific interaction of NPs with the bacterial cell wall is facilitated by

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A. Parmar and S. Sharma