## 5 Therapeutic Properties of Nanoparticles in Breast Cancer Treatment  
The challenges posed by conventional therapies, causing indiscriminate damage to body tissues, have been effectively addressed by the rapid advancements in nanotechnology [58]. This technology provides distinct advantages by enhancing the efficacy of radiation therapy and medication while mitigating side effects [59]. Multifunctional nanocarriers leverage the differences between tumor and normal tissue, facilitating the selective transport of therapeutic medications and increasing drug permeability and retention. Moreover, the unique physical and chemical characteristics of the tumor microenvironment (TME), including hypoxia, weak acidity, lower pH, unusual temperature gradient, and overexpressed proteins and enzymes, can be harnessed to control the release rate of pharmaceuticals from nanocarriers [60].  
Nanomaterials are broadly divided into two main subcategories: nanostructured and nanocrystalline. Within the classification of nanostructured materials, lipid-based nanoparticles, along with both nonpolymer and polymer-based nanoparticles, fall under this category [42]. Polymer-based nanoparticles encompass dendrimers, micelles, nanogels, protein nanoparticles, and drug conjugates. Nonpolymeric nanoparticles include silica-based nanoparticles, metallic nanoparticles, quantum dots, carbon nanotubes, and nanodiamonds [61]. Lipid-based nanoparticles are categorized into two types: liposomes  
Figure 2: Common nanomaterials and carrier types utilized as controlled release systems for therapeutic applications. Row 1 (left to right): zero-dimensional (0-D) material, where drugs can be loaded on the surface; one-dimensional (1-D) material (example: carbon nanotube), where drugs are loaded into the tube’s interior; and two-dimensional (2-D) material, where drugs can be loaded in-between the layers. Row 2 (left to right): mesoporous materials, where drugs are loaded onto the porous; liposomes, where drugs can be loaded on the interior lipid bilayer; and micelle, where drugs can be tagged with the polar/nonpolar layer. Row 3 (left to right): dendrimer, where drugs can be loaded into the void spaces; polymeric nanoparticles, where drugs can be functionalized in the terminal layers; and hydrogel, where drugs can be interlinked in the polymer chains [57], reproduced with permission from [PERSON] et al., (2018), © Springer Nature (Creative Commons Attribution 4.0).  
and solid lipid nanoparticles. The nanoparticles clinically approved for therapeutic purposes predominantly consist of polymer- or lipid-based components [62]. In addition to nanostructured particles based on polymers, nonpolymers, or lipids, specific therapeutic applications also involve the use of nanocrystalline particles formed through the crystallization of medicinal substances [42].  
In the selection of therapeutic nanoparticles, the critical factors to consider include uptake, distribution, release, interaction with cells and molecules, modulation of the immune system, prolonged existence, and overall efficiency. The mechanisms mentioned in this section are rooted in the inherent characteristics of nanoparticles [63]. Refer to Figure 3 for a visual representation of systemic drug delivery mechanisms utilizing novel nanomaterials for breast cancer treatment.