## 8 Metallic-Based Nanocarriers
### Metallic Nanoparticles
Among these metallic nanoparticles, silver and gold have become notable for their potent antimicrobial effects against a broad spectrum of microorganisms, including those resistant to multiple drugs, both in planktonic and biofilm-forming bacteria. Furthermore, these NPs can be easily functionalized with ligands, enhancing their biocompatibility and chemical stability [144]. Silver nanoparticles (AgNPs) have demonstrated effectiveness against a wide range of pathogens, including fungi, viruses, and various bacterial species [138]. Additionally, AgNPs have demonstrated potential as antimicrobial agents against drug-resistant bacteria [143]. Proposed mechanisms include contact killing and ion-mediated killing, membrane damage induction, reactive oxygen species (ROS) production, and cellular activity disruption such as ATP production and DNA replication [135]. AgNPs' antimicrobial activity is credited both to the released silver ions and to the nanoparticles themselves. AgNPs can attach to bacterial cell membranes and penetrate the cells, causing damage by interacting with phosphorus- and sulfur-containing compounds like DNA. They specifically target the respiratory chain and cell division processes, ultimately leading to cell death [147]. Gold nanoparticles (AuNPs) have recently garnered significant attention due to their biocompatibility. Moreover, their anti-biofilm activity has been documented in recent studies [139]. While the precise mechanism by which they inhibit bacterial growth is still unclear, some reports suggest that damage to the bacterial cell wall is a contributing factor to bacterial cell death [137]. AuNPs are believed to interact with functional groups on the bacterial cell surface, leading to the inactivation and destruction of the bacteria [133]. Metal oxide nanoparticles, such as zinc oxide (ZnO) and titanium dioxide (TiO\({}_{2}\)) nanoparticles, are also being extensively studied as potential antimicrobial agents. Zinc oxide nanoparticles exhibit antimicrobial properties by strongly adhering to bacterial cell membranes and disrupting the lipids and proteins, leading to the leakage of intracellular contents and eventual cell death [174]. Additionally, the generation of hydrogen peroxide and Zn\({}^{2+}\) ions, which damage bacterial cells, is considered a key antibacterial mechanism of ZnO nanoparticles (ZnONPs) [146]. Titanium dioxide nanoparticles are studied for their photocatalytic antimicrobial properties. In a process known as photocatalysis, TiO\({}_{2}\) nanoparticles generate reactive oxygen species (ROS), including hydrogen peroxide and hydroxyl radicals, upon exposure to ultraviolet (UV) light. These ROS damage bacterial cell membranes, disrupt their semipermeability, interfere with oxidative phosphorylation, and can sometimes lead to cell death [142]. The magnetic characteristics of iron oxide nanoparticles (NPs) have been researched for their uses in diagnosis and treatment [134]. Consequently, magnetic nanoparticles (MNPs) present a promising targeted nanosystem as they can be maneuvered by a magnetic field gradient to reach specific biological targets [141]. Moreover, these particles are economical, stable both physically and chemically, biocompatible, and environmentally friendly [134]. The bactericidal action mechanism is the generation of ROS leading to cell death by necrosis or apoptosis [145]. Superparamagnetic iron oxide nanoparticles (SPIONs) are widely utilized in various medical applications, such as imaging, biodetection, and the delivery of drugs and genes [140]. These nanoparticles have also been researched for biofilm eradication [136]. Table 6 summarizes the information concerning polymeric-based formulations to eradicate biofilms. Metallic-based nanocarriers, such as those composed of silver, gold, or zinc oxide, are widely used in drug delivery, imaging, and diagnostic applications due to their unique optical, magnetic, and conductive properties. However, their biocompatibility and potential toxicity are major concerns.