## 6 Properties of Breast Cancer Drugs
Additionally, depending on their electrostatic characteristics, they can be classified as either highly charged or neutral. When creating NPs to serve as carriers for particular drug classes, understanding the drug's behaviors and properties is crucial to ensure optimal encapsulation and the desired release traits. NPs that are functionalized or tailored are particularly promising in drug delivery systems due to their unique sizes, adaptable surface properties, and controlled drug release capabilities. Hydrophilic drugs are crucial in treating BC subtypes and encompass both macromolecules and various small molecular compounds. Most therapeutic BC drugs used in clinics are hydrophobic, which poses ongoing delivery challenges to their intended targets [87]. Given their water-insolubility, hydrophobic drugs struggle to traverse through bodily fluids and find it challenging to penetrate cell membranes and reach intracellular targets. Furthermore, administering these drugs intravenously can result in clinical complications, such as tissue damage and embolisms. Existing breast cancer treatments encounter several challenges, including a lack of targeted toxicity, leading to reduced treatment effectiveness and compromised medical diagnosis [91]. These treatments can also cause harm to healthy tissues, requiring reduced doses of anticancer drugs to lessen this toxicity. In solid tumors, there is often inadequate distribution and penetration, and the diverse blood vessels in tumor areas can lead to excessive drug leakage [91]. In comparison to tumor sites, normal organs often receive 10-20 times more drug deposits. Additionally, many chemotherapy drugs cannot spread beyond 40-50 mm from the blood vessels, potentially causing multidrug resistance (MDR) and treatment failure. When tumor cells develop MDR after exposure to one anticancer drug, they may become resistant to multiple drugs due to the heightened expression of drug-removal proteins [92]. The combined innovation of nanoparticle designs with new pharmaceutical components broadens the spectrum of active ingredients beyond those conventionally considered safe or effective. There is also an exploration into immune-boosting components and coatings, acting as supplementary measures to conventional radio- and chemotherapy or as independent treatments. One exciting approach involves crafting nanoparticles as synthetic antigen-presenting cells and in vivo reservoirs of immune-enhancing factors, harnessing the power of nanotech for sustained anticancer activities [92]. Technological advancements in cancer treatment have significantly improved the standard therapeutic strategies for BC, leading to a reduced mortality rate and aiding many patients in their cancer recovery. However, challenges remain in treating BC using the current therapeutic approaches. Chemotherapy is widely recognized as the primary treatment for BC [93]. However, traditional chemotherapy approaches have notable limitations. One major concern is the nonspecific distribution of chemotherapeutic agents to tumors. These agents harm the body's normal cells along with their rapid-dividing cancerous targets. This lack of specificity often leads to unavoidable side effects [93]. The subsequent side effects include hair loss, vomiting, nausea, diarrhea, mouth ulcers, fatigue, heightened vulnerability to infectious diseases, myelosuppression, and issues like leucopenia, anemia, and increased propensity for bruising or bleeding [94]. Moreover, specific drugs have unique side effects, such as cardiotoxicity from anthracyclines and ototoxicity and nephrotoxicity from cisplatin. Secondly, drug resistance poses another challenge for traditional chemotherapeutic agents, diminishing their effectiveness in treating cancer cells [94]. This resistance can be categorized into innate and acquired types, depending on when they appear.