## 8 Metallic-Based Nanocarriers  
### Metallic Nanoparticles  
Metallic nanoparticles (NPs) can be used as drug delivery systems because they protect drugs until they reach their target site and avoid triggering the immune system, all while exhibiting low cytotoxicity [1]. Additionally, many metallic NPs have been researched for their inherent antimicrobial properties and the low likelihood of bacteria  
Figure 3: Representative structure of various polymeric-based nanocarriers. (**A**) Polymeric nanoparticles, (**B**) polymeric micelles, and (**C**) dendrimers. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of** & **Composition** & **Encapsulated** & **Bacteria** & **Mechanism of Action** & **References** \\
**Nanocarrier** & **Composition** & **Compound** & **Bacteria** & **Mechanism of Action** & **References** \\ \hline \multirow{6}{*}{Polymeric nanoparticles} & PLGA & Ciprofloxacin & _S. aureus_ and _P. aeruginosa_ & Enhance drug & \multirow{6}{*}{[173]} \\  & PVA & Ciprofloxacin & _S. aureus, P. aeruginosa_ & & & \\  & & Carvacrol, & _S. aureus, P. aeruginosa_, and & & & \\  & & rifampicin, & _S. epidermidis_ & & & \\  & & & & & \\  & & Clarithromycin, & & & & \\  & PLGA & rifampicin, & - & & & \\  & & ciprofloxacin & & & \\ \hline Polymeric & PLGA-b-mPEG and & \multirow{2}{*}{Terpyridine} & _P. aeruginosa_ & Fe(II) chelating by & \multirow{2}{*}{[125]} \\ micelles & PLGA-b-p(Typy)\({}_{\text{S}}\) & & & & \\  & Liquid crystalline & & & & \\  & dendrimers, & & & & \\  & core–shell tecto & & & & \\  & dendrimer, & & & & \\  & glycoloadrimers, & - & _S. aureus, E. coli_, & Enhanced & \multirow{2}{*}{[132]} \\ Dendrimers & glycoloadrimers, & - & _P. aeruginosa_ & encapsulation & \\  & polyglycerol, & & & & \\  & PAMAM, PEPE, & & & & \\  & PPI, PAMAMOS & & & & \\  & & & _B. cereus, E. coli, P. aeruginosa_, & & \\  & & & _aeruginosa, S. aureus, & & \\  & & & _S. oralis_ & antimicrobial activity & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Examples of polymeric-based nanocarriers developed to eradicate biofilms. developing resistance to them [96]. Table 6 provides an overview of metallic NPs developed to eradicate biofilms. While the precise antibacterial mechanisms of metallic nanoparticles are still under study, theories include the following: (i) Disruption of the biofilm structure. This can be accomplished by physical interaction (metallic NPs can penetrate and disrupt the extracellular matrix of biofilms due to their small size, effectively breaking down the biofilm structure) or by chemical interaction (NPs can interact with EPS, destabilizing them). (ii) Generation of reactive oxygen species (ROS) by oxidative stress (metallic NPs, particularly silver and zinc oxide NPs, can generate reactive oxygen species, which cause oxidative stress to bacterial cells, leading to cell damage and death) or by localized damage (ROS can damage cellular components such as DNA, proteins, and lipids, leading to the breakdown of the biofilm's protective environment). (iii) Release of metal ions, not only because of their antibacterial properties (many metallic NPs release metal ions (e.g., Ag\({}^{+}\), Zn\({}^{2+}\), Cu\({}^{2+}\)) that have potent antibacterial properties by disrupting bacterial cell membranes, interfering with enzyme function and inhibiting essential cellular processes), but also because of their sustained release ability (the slow release of metal ions ensures prolonged antibacterial activity, preventing biofilm formation and recurrence). (iv) Synergistic effects caused by combination therapy (metallic NPs can be combined with antibiotics or other antimicrobial agents to enhance their effectiveness. The NPs can facilitate better penetration of the antibiotics into the biofilm and reduce the likelihood of bacterial resistance) and functionalization (NPs can be functionalized with ligands, peptides, or other molecules to target specific bacterial strains or biofilm components, improving their efficacy) [148].