## 2 Metallic Nanoparticles in Conjugation with Chlorin Derivatives
### Iron Oxide and Other Magnetic Nanoparticles
BSA coating was responsible for improving biocompatibility and prolonging the internal circulation time, while iron cations can induce the chemodynamic therapy effect by reacting with overexpressed hydrogen peroxide in the tumor to produce cytotoxic hydroxyl radicals. What is more, they can increase the glutathione uptake in the tumor cells. The size of the obtained nanoparticles via electrostatic adsorption and hydrophobic interactions was about 197.5 nm. The in vitro and in vivo studies on murine breast cancer cells and tumor-bearing mice revealed an excellent cytotoxic effect (cell viability at 3% in in vitro studies) after irradiation with light at 660 nm, a standard wavelength for PDT with the use of Ce6 [23]. Interesting nanoparticles, named pH-sensitive magnetic nanogrenades (PMNs), were presented by [PERSON] et al. [24]. Designed nanostructures consisted of chain poly(ethylene glycol)-poly(\(\beta\)-benzyl-L-aspartate) ligands bearing a PS--Ce6 and an imidazole ring sensitive to pH changes. The type A ligands with catechol groups were bound to iron oxide nanoparticles with a dimension of ca. 3 nm, unlike the type B ligands with phenol groups. The PMN particles with a hydrodynamic diameter of 70 nm were well-dispersed in water and consisted of a hydrophobic core with Ce6 ligands and a spherical-shaped PEG shell. The MRI experiments indicated that at pH 7.4, the MR contrast is quenched, whereas it is significantly enhanced at pH 5.5. Thus, the authors concluded that the obtained material could be considered a highly selective cancer imaging tool. Simultaneously, the authors assessed the cellular uptake of PMNs by human colorectal carcinoma (HCT116). Higher uptake of PMNs was noted at pH 6.8 than at pH 7.4. In in vivo experiments, the authors observed the potential of the material for early-stage tumor visualization and noted the cancerous changes of ca. 3 mm in diameter. Moreover, prolonged blood circulation with a t\({}_{1/2}\) value of 2.9 h was noted. The authors also indicated the possibility of applying PMNs for cancer treatment based on the mouse model bearing a homogeneous HCT116 xenograft and for the treatment of highly heterogeneous, drug-resistant CT26 tumors [24]. The combination of magnetic and carbon nanoparticles functionalized with Ce6 and platinum atoms was fabricated by [PERSON] et al. for MRI purposes, as well as photodynamic and photothermal effects [25]. The obtained yolk-shell magnetic Fe\({}_{3}\)O\({}_{4}\)@Carbon@Platinum-Ce6 nanoparticles increased the T2 MRI ability and revealed a high photothermal conversion efficiency and PDT therapeutic effects in acidic and H\({}_{2}\)O\({}_{2}\)-rich microenvironments in the CT26 tumor-bearing mice, after irradiation with a laser at 660 nm and 808 nm. Moreover, in the obtained nanoparticles, the presence of Pt atoms enhanced the catalytic ability of the photocatalyst toward the generation of reactive oxygen species by catalyzing the hydrogen peroxide cleavage to O\({}_{2}\) moieties [25]. Photodynamic and magnetothermal therapies were not the only ones where the conjugates of magnetic nanoparticles and chlorins were utilized in biomedical applications. [PERSON] et al. proposed a core-shell hybrid nanomaterial based on maghemite nanoparticles (\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)) against _Aedes aegypti_ instead of insecticides [26]. The mosquito _Aedes aegypti_ is responsible for spreading dengue and yellow fever. Maghemite nanoparticles are materials with an active surface binding specific molecules, including carboxyl group-bearing organic molecules, i.e., Ce6. The authors estimated that for 6 days, the release of the PS was equal to 25%. Nanoparticles were administered to the mosquito larvae in the feed formulates and accumulated in the gut. Exposing nanoparticles at concentrations 50 and 100 mg/L to the light for 3 and 1.4 h, respectively, caused 100% larvae mortality. Simultaneously, studies on eco-toxicity for aquatic microorganisms were performed.