traditional antibiotics exhibit their antimicrobial activity by one of these mechanisms: (i) inhibition of cell wall synthesis, (ii) inhibition of fatty acid biosynthesis, (iii) inhibition of protein synthesis, and (iv) compromising the cell membrane functions. Application of either one of the simple mechanisms by the traditional antibiotics is the main reason for the occurrence of bacterial resistance. On the other hand, nanomaterials have different mechanisms of action such as: (i) disputing cell membranes, (ii) causing DNA damage, (iii) interrupting the transmembrane electron transport, and (iv) inducing oxidative stress. Further, nanomaterials can be designed to have multiple mechanisms that act simultaneously against microbes. Hence, it becomes difficult for microbes to develop resistance against nanomaterials as they are unlikely to have many mutated genes. The most commonly exploited antibacterial nanomaterials include nanometals (silver, copper); metal oxides (Zinc oxide, titanium dioxide); carbonaceous materials (graphene, graphene oxide, carbon nanotubes); and cationic polymers (chitosan).5 Among Gram‐negative and Gram‐positive bacteria which has higher resistance over hydrophilic drugs and state the reason?Among these two groups of bacteria, Gram‐negative bacteria have higher resistance over hydrophilic drugs in comparison to Gram‐positive since Gram‐negative bacteria have an extra hydrophobic lipid bilayer over a thin peptidoglycan layer (20–50 nm). The presence of such an extra lipid layer limits the permeability of several hydrophilic antimicrobial agents, which is one of the reasons for high resistance of Gram‐negative bacteria.
6 In general, smaller sized nanomaterials exhibit higher antimicrobial property in comparison to the bigger sized particles of the same material. State the reason.Generally, smaller sized nanomaterials have higher surface area and thus high chance of prolonged interaction with the microbial system and diffuse through the cell membrane in comparison to bigger nanomaterials with smaller surface area. Additionally, it is possible to contain a significantly higher number of smaller NMs in comparison to bigger particles in the same volume. The higher surface area‐to‐volume ratio owing to increased number of particles results in exposure of greater numbers of atoms. Exposure of a greater number of atoms on the surface results in increased interaction of nanomaterial surface with bacteria increasing the number of reactive oxygen species at faster rate followed by inhibition or elimination of the bacteria.
7 Does the shape of the nanomaterial affect the antimicrobial property? If yes explain why?Yes, the shape is also one of the crucial factors that affect the structural behavior and antimicrobial activity of the nanomaterials. Apart from size, shape of the nanomaterials also has influence over the surface area where even same materials with the same size will have different surface area because of a change in shape. The surface area of the nanomaterials strongly determines the level of interaction of the nanomaterial with the microbial surface. Thus, shape plays a crucial role with regard to interaction and the toxic effects on bacterial cell where nanomaterials of different shapes would cause varying degrees of bacterial cell damage and antibacterial property.
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