## 2 Metallic Nanoparticles in Conjugation with Chlorin Derivatives
### Iron Oxide and Other Magnetic Nanoparticles
This procedure yielded 92 nm diameter nanoclusters of Fe\({}_{3}\)O\({}_{4}\) stabilized in water by the excellent loading of Ce6 molecules assembled on their surface (also reaching over 50% of the mass of the nanoclusters). The material was tested in vivo based on athymic nude mice bearing xenograft breast cancer tumors (4T1 cell line) and tended to accumulate in tumors upon intravenous injection. Due to the paramagnetic properties of the Fe\({}_{3}\)O\({}_{4}\), the nanoclusters could be used as a contrast agent in MRI, and although the fluorescence from Ce6 was quenched in solution, the nanoclusters in vivo exhibited increased fluorescence and enabled fluorescence imaging. Another property of this material was related to its ability to generate singlet oxygen, which allowed for the performance of the PDT experiment in vitro in the dark conditions on 4T1 cells and healthy human umbilical vein endothelial cells (HUVECs). The material was found to be non-toxic without irradiation. The viability of 4T1 cells, which were irradiated with a 665 nm laser, was lower than 10% compared to that of the non-irradiated cells. The in vivo PDT experiment showed a significant decrease in the tumor volume in mice in which nanoclusters were administered compared to Ce6-treated mice [18]. Another method was proposed by [PERSON] et al., where a complex nanocluster material, by combining poly(isobutylene-alt-maleic anhydride), PEGs, dopamine, cystamine, Ce6, and Fe\({}_{3}\)O\({}_{4}\) nanoparticles, was prepared [19]. The nanosystems were studied for their in vitro PDT utility based on MDA-MB-231 cells (metastatic mammary gland adenocarcinoma) and were found more effective than Ce6 alone. The same effect was also observed in the in vivo experiment using mice bearing MDA-MB-231 cell line tumors. The authors suggested that the obtained material can be useful for in vivo MRI and fluorescent imaging [19]. Figure 4: Chemical structure of the Fe\({}_{3}\)O\({}_{4}\) nanoparticles that were modified with Ce6 molecules through alkyl chains [17]. The coordination of Ce6 to iron atoms on the surfaces of magnetic nanoparticles coated with glucose was proposed by [PERSON] et al. to improve the distribution of Ce6 in lung cancer [20]. The in vitro and in vivo studies performed with the Lewis cell line (LLC) and an LLC-tumor-bearing mouse model revealed that the obtained nanosystems significantly damaged the DNA code of the lung cancer cells and activated the mechanism of augmented immunogenicity leading to tumor cell death. [PERSON] et al. conjugated a novel unsymmetrically substituted chlorin, also with dextran-coated iron oxide nanoparticles [21]. The intent was to propose a new method of atherosclerosis treatment. The material was initially tested for its non-toxicity in dark conditions using RAW 264.7 murine macrophages, and when confirmed, it was applied in vivo to apolipoprotein E-deficient mice, which were fed a high-cholesterol diet. The material was primarily found to accumulate in the inflammatory macrophages and exhibited significant photocytotoxicity (LD\({}_{50}\) = 14 nM). It was concluded that the material shows promising features for stabilizing arteriosclerotic lesions [21]. The Fe\({}_{3}\)O\({}_{4}\) magnetic nanoparticles were also successfully functionalized with aptamers, graphene oxide, Ce6, and paclitaxel for the selective killing of MCF-7 tumor cells, by [PERSON] et al. [22]. The researchers proved that the photothermal impact of the fabricated nanocomposite could be used to perform the Ce6 release when irradiated to a near-infrared laser at a low-power density. A synergistic therapeutic effect was observed when 660 and 808 nm lasers were used, significantly enhancingMCF-7 cell death (83.67%). Bovine serum albumin-coated iron peroxide nanoparticles conjugated with Ce6 was invented by [PERSON] et al. [23].