## 4 Applications of CDs in Cancer Theranosis
### Cancer Therapy via Drug Delivery, PTT, PDT, PTT+PDT, siRNA Delivery, SDT, and Gas Therapy
#### 4.2.4 Synergistic PDT+PTT  
As discussed above, CDs can be used for both PDT and PTT, providing multiple choices for therapeutic applications. Recently, synergistic PTT and PDT using CDs have shown great promise in improving monotherapy mode by simultaneously generating heat and ROS [39; 172; 173; 174; 175; 176]. In a study by [PERSON] et al., a small amount of photosensitizer Ce6 was anchored onto CDs to enhance the efficacy of cancer phototherapy with a relatively low laser irradiation power [39]. They demonstrated the superior efficacy of the synergistic PDT+PTT mode compared to either single mode of PDT and PTT under a relatively low-power laser irradiation. The in vivo assessments of the PDT and PTT efficacy of Ce6-modified red emissive CDs (Ce6-RCDs) were performed using 4T1 cancer-bearing nude mice. The mice were separated into four treatment groups: a blank group (PBS + laser), a PDT group (free Ce6 + laser), a PTT group (RCDs + laser), and a combined PDT + PTT group (Ce6-RCDs + laser), in which a 671 nm laser was irradiated for 10 min. The results revealed that the PDT group exhibited negligible cancer growth inhibition, with cancer volumes increasing to about 6.5 times their initial size after 13 days of treatment, similar to the blank group (Figure 13a-c). The PTT group showed some cancer growth inhibition, but the cancer volume still increased to approximately 3.5 times the initial size. In contrast, the PDT + PTT group demonstrated a significant cancer growth suppression, with cancer volumes shrinking to around 30% of their initial size after 13 days of treatment and also exhibited signs of cancer necrosis and black scars at the cancer site just three days after treatment (Figure 13b,c), whereas the blank and PDT groups showed a rapid cancer growth three days after treatment. Recently, an injectable CD-based hydrogel was developed for simultaneous PTT and PDT [177; 178; 175]. [PERSON] et al. prepared a novel injectable hydrogel  
Figure 12: (**a**) Photographs of excised cancers after two weeks of PDT and (**b**) cancer volume changes in 4T1-bearing mice over time after PDT (*** \(p<\) 0.001) [171]. (**c**) Photographs of excised cancers on the 13 th day after PDT and (**d**) cancer volume changes in H22-bearing mice over time after PDT (** \(p<\) 0.01; *** \(p<\) 0.001) [168]. (**e**) Photographs of mice and excised cancers from the sacrificed mice on the 16 th day after PDT and (**f**) cancer volume changes in A549-bearing mice over time after PDT [165]. (**g**) Photographs of excised cancers on the 15 th day after PDT, (**h**) cancer volume changes in CT26-bearing mice over time after PDT, (**i**) cancer weights on the 15 th day after PDT, and (**j**) body weight changes in CT26-bearing mice over time after PDT (*** \(p<\) 0.0001) [59]. \(p\)-values were calculated by Student’s \(t\)-test. using CDs and HA (CD@ Hydrogel) for PTT and PDT of cancer in which HA was used as a hydrogel precursor [177]. The anticancer activity of CD@Hydrogel in vivo was evaluated using 4T1 cancer-bearing mice. As shown in Figure 13d,e, the CD@Hydrogel + NIR (660 nm for 600 s) group exhibited the most pronounced inhibitory effect on cancer growth, with no significant inhibitory effect in the other three groups. In addition, there were no significant changes in body weight for all groups, offering a simple and efficient strategy for cancer phototherapy. [PERSON] et al. evaluated the anticancer efficacy of sulfur (S) and nitrogen (N)-codoped CDs, N-doped CDs, and CDs using HeLa cancer-bearing mice [179]. As illustrated in Figure 13f,g, the PBS + laser (660 nm and 5 min irradiation), S and N-CDs, and CDs + laser groups showed no significant anticancer effects, and the N-CDs + laser group exhibited limited cancer inhibition. However, the S and N-CDs + laser group exhibited almost complete ablation of cancer. [PERSON] et al. synthesized hypocrella bambusae (HB)-derived R-CDs (HBCDs) for imaging-based PTT and PDT (635 nm and 10 min laser irradiation) [176]. The study involved five groups of 4T1 cancer-bearing nude mice.