Metal Nanoparticles for Photodynamic Therapy: A Potential Treatment for Breast Cancer

Abstract

Breast cancer (BC) is the most common malignant tumor in women worldwide, which seriously threatens women’s physical and mental health. In recent years, photodynamic therapy (PDT) has shown significant advantages in cancer treatment. PDT involves activating photosensitizers with appropriate wavelengths of light, producing transient levels of reactive oxygen species (ROS). Compared with free photosensitizers, the use of nanoparticles in PDT shows great advantages in terms of solubility, early degradation, and biodistribution, as well as more effective intercellular penetration and targeted cancer cell uptake. Under the current circumstances, researchers have made promising efforts to develop nanocarrier photosensitizers. Reasonably designed photosensitizer (PS) nanoparticles can be achieved through non-covalent (self-aggregation, interfacial deposition, interfacial polymerization or core-shell embedding and physical adsorption) or covalent (chemical immobilization or coupling) processes and accumulate in certain tumors through passive and/or active targeting. These PS loading methods provide chemical and physical stability to the PS payload. Among nanoparticles, metal nanoparticles have the advantages of high stability, adjustable size, optical properties, and easy surface functionalization, making them more biocompatible in biological applications. In this review, we summarize the current development and application status of photodynamic therapy for breast cancer, especially the latest developments in the application of metal nanocarriers in breast cancer PDT, and highlight some of the recent synergistic therapies, hopefully providing an accessible overview of the current knowledge that may act as a basis for new ideas or systematic evaluations of already promising results.

Recent Developments in Metallic Nanomaterials for Cancer Therapy, Diagnosing and Imaging Applications

“…Gold nanoparticles (Au NPs) represent one of the most investigated metal-based NPs in medicine [15]. The appealing features of Au NPs count low toxicity and immunogenicity, good biocompatibility, excellent stability, enhanced permeability and retention, inherent immune activation properties, and easily modifiable surface [1,8,11,16]. Moreover, the developments achieved in various chemical and biological synthesis methods allowed the fabrication of Au NPs with tailored sizes, shapes, and structures (Figure 2), endowing them with desired properties.…”

“…However, conventional PS may face a poor specific uptake in tumor cells, posing a threat on healthy neighboring tissues. Thus, involving nanotechnology in this type of therapy became fundamental for obtaining maximum results while avoiding side effects [11,16,178].…”

“…Metal-based NPs are particularly appealing in nanomedicine due to their relatively narrow size and shape distribution, long activity period, dense surface functionalization, and capability for optical or heat-based therapeutic strategies. Compared to nonmetallic NPs of similar sizes, the higher density of metallic NPs allows them to be more readily taken up by cells, thus proving advantageous for cancer management strategies [8,11]. In addition, metal NPs were reported to offer better targeting, gene silencing, and drug delivery, especially when functionalized with targeting ligands that provide controlled deposition into tumor cells [6].…”

Fundamentals and applications of metal nanoparticle- enhanced singlet oxygen generation for improved cancer photodynamic therapy

“…The breakthrough observation of plasmon-mediated electron emission from the metallic NPs mainly gold and silver, into the surrounding media leading to 1 O 2 generation upon direct light irradiation made them a potential PS candidate for PDT (Lv, Zhang, Li, Wang, He). Furthermore, as discussed, metallic NPs offer several advantages over organic PSs of high stability, high loading or conjugation efficiency, adjustable size, optical properties, easy surface functionalization, slow degradation, and long cycle time, making them more biocompatible and resistant to decomposition in biological applications, which allows tumor targeting, delivery and controllable release of PSs (Sun et al, 2018;Shang et al, 2021). The metallic NPs exhibit high extinction coefficient which generally compensates for the somewhat low 1 O 2 yield and reduces the overall excitation power, thus, slowing down the depletion of tissue oxygen and promoting the reperfusion of tissue oxygen.…”

Photodynamic therapy in breast cancer treatment

“…Photosensitizers accu-mulate within cell organelles, contributing to their damage (García Calavia et al, 2018), which entails cell death in a typical mechanism of apoptosis, necrosis, or autophagy. Metal nanoparticles (Ashkbar et al, 2020), photodynamic and photothermal approaches with the aid of curcumin photosensitizer and magnetic nanoparticles (Shang et al, 2021) have already been used.…”