## 2 Metallic Nanoparticles in Conjugation with Chlorin Derivatives
### Other Metallic Nanoparticles
The authors confirmed singlet oxygen formation upon nanoparticle irradiation with light at 671 nm and a photothermal effect upon irradiation with light at 808 nm. Moreover, the particles revealed high photothermal stability. The biocompatibility were noted in the experiments in vitro with CD44-overexpressing cancer B16F1 cells and with CD44-deficient HeLa cells. Moreover, in an in vivo experiment with zebrafish embryos, no influence of nanoparticles on development was observed. In the assessment of photodynamic activity, the fabricated nanoparticles at a concentration \(\geq\)50 ppm activated with light at 671 nm caused the death of 60% of the B16F1 cell population. A similar result was observed for photothermal therapy when particles were activated with light at 808 nm. The authors combined these methods, which led to an 80% reduction in the cancer cell population. Cellular uptake experiments indicated that the HA component interacts with the CD44 receptor and promotes the entry of nanoparticles into the cells [52]. The multifunctional ultra-small FeS\({}_{2}\) nanodots with a Ce6 of a diameter ca. 7 nm were obtained by [PERSON] et al. [53]. Nanoparticles facilitated three-way tumor imaging according to photoacoustic, magnetic resonance, and fluorescence imaging protocols. Cancerous lesions can be treated by combining photothermal and photodynamic therapies. The authors obtained nanodots via FeS\({}_{2}\) precipitation on bovine serum albumin (BSA) and the subsequent conjugation of Ce6 with the amide coupling method. Singlet oxygen production after irradiation with light at 660 nm was confirmed, and the photothermal effect after excitation with 808 nm was noted. The authors assessed cytotoxicity and biocompatibility in dark conditions both in vitro and in vivo and did not notice any toxic effects. Additionally, the high efficacy of combined photothermal and photodynamic treatment on 4T1 murine breast cancer cells in vitro was observed. In the in vivo model, the authors noted that combining these therapeutic approaches led to the complete eradication of the tumor, whereas when PTT and PDT were used separately, only a slight response was obtained [53]. [PERSON] et al. presented another approach for cancer treatment with combined therapy [54]. In their studies, chemotherapy, photodynamic therapy, and photothermal therapy were combined together via the fabrication of nanomaterial consisting of doxorubicin and Ce6 loaded onto CuS nanoparticles. Phase change material--1-tetradeanol was used as a stabilizing and triggering agent. Under irradiation with light at 808 nm, the photothermal effect was observed, and a temperature increase up to 43 \({}^{\circ}\)C (100 \(\upmu\)g/mL) was noted. This caused the ablation of the tumor and melting of 1-tetradeanol, accompanied by the release of doxorubicin and Ce6. Furthermore, a light at 660 nm was provided to turn on the photodynamic process. In vitro studies indicated high activity of the nanomaterial against 4T1 cancer cells. Combined irradiation with light at 808 nm and 660 nm reduced cell viability significantly (ca. 1% cells left), whereas nanoparticles irradiated only with 660 nm, due to the absence of free Ce6, revealed no activity. Doxorubicin and Ce6 were released and accumulated in the nuclei and the cytoplasm, respectively. In vivo trialswere performed on BALB/c nude mouse models bearing 4T1 tumors. The obtained nanodrug was administrated intravenously and accumulated selectively in the tumor within 24 h. The treatment was performed with the same optical parameters adjusted to in vitro studies--irradiation with 808 nm prior to 660 nm. The vital signs of mice were monitored, and similar to that in in vitro experiments, the high biocompatibility of light-unaffected nanoparticles was noticed. Interestingly, the authors observed a reduction in the tumor volume by about 80% with a single treatment cycle. The performed in vitro and in vivo experiments indicated a high level of cancer cell death based on the apoptosis pathway [54].