## 7 Polymeric-Based Nanocarriers
### Dendrimers  
Dendrimers are highly branched, tree-like macromolecules with a well-defined, three-dimensional architecture. These synthetic polymers are characterized by their multiple layers, called generations, surrounding a central core. The unique structure of dendrimers provides a high degree of surface functionality and versatility, making them suitable for various biomedical applications, including antibacterial treatments [131]. Dendrimers are constituted by a core (the central part of the dendrimer from which branches emanate), branches (repeatedly branched structures extending from the core), and surface groups (functional groups located on the outermost branches, which can be modified to enhance interactions with bacterial cells) [127].  
Dendrimers can destroy bacteria through several mechanisms, which can be categorized into direct antibacterial activity and delivery of antibacterial agents [171]. Concerning the direct antibacterial activity, dendrimers can disrupt cell membranes, leading to cell lysis. For example, cationic dendrimers can interact with negatively charged bacterial cell membranes, causing structural damage [128]. Moreover, certain dendrimers can induce the production of reactive oxygen species (ROS), which can damage bacterial DNA, proteins, and lipids, leading to cell death [126]. With regard to the delivery of antibacterial agents, dendrimers can encapsulate or conjugate with antibiotics, enhancing the solubility, stability, and bioavailability of these drugs. The dendrimer structure allows for the controlled release of the antibiotic, targeting the bacteria more effectively [130]. Also, functional groups on the dendrimer surface can be modified to target specific bacterial strains or biofilms. This targeted approach helps in delivering the antibacterial agents directly to the site of infection, reducing the required dosage and minimizing side effects [132]. Poly(amidoamine) (PAMAM) is among the most studied dendrimers for antibacterial applications. PAMAM dendrimers can be functionalized with various antibacterial agents or modified to have intrinsic antibacterial properties [128]. Cationic dendrimers, due to their positive charge, can effectively interact with the negatively charged bacterial cell walls, leading to membrane disruption and bacterial death [129]. Carbohydrate-functionalized dendrimers can target specific bacterial lectins, enhancing the binding and uptake by bacterial cells and delivering antibacterial agents more effectively [132].  
Table 5 summarizes the information concerning polymeric-based formulations used to eradicate biofilms. Polymeric-based nanocarriers, such as polymeric nanoparticles, micelles, and dendrimers, are popular in drug delivery systems due to their tunable properties, stability, and controlled release capabilities. While they generally exhibit good biocompatibility, potential toxicity can arise from the polymers themselves or their degradation products, which may cause inflammatory responses or toxicity if not fully metabolized. Additionally, the size, surface charge, and composition of these nanocarriers can influence their interaction with cells and tissues, impacting their safety profile. To enhance biocompatibility, it is  
crucial to carefully design these nanocarriers, using biodegradable and non-immunogenic materials, and to thoroughly evaluate their long-term effects in vivo [172].  
Figure 3 depicts a schematic representation of polymeric nanoparticles, polymeric micelles, and dendrimers.