excellent photothermal conversion properties. This means they can efciently con­vert absorbed light energy into heat [88]. Surface modication can be employed to optimize their photothermal efciency and improve their application in PTT, a tech­nique that utilizes heat generated by light absorption to selectively destroy cancer cells or deliver heat-sensitive therapeutics. By embedding or connecting these plas­monic NPs onto the surface of 2D materials, light absorption can be signicantly heightened, promising an improved efcacy of PTT [89]. This section of the book chapter provides an overview of the diverse range of NP approaches, including PBB, biomimetic NPs, inorganic NPs, and upconverting NPs, poised to revolution­ize PTT and redene the landscape of medical treatments.

Choi etal. [50] used tiny structures called nanoworms to do a special kind of treat­ment, called photothermal therapy (PTT), on HeLa cells. They mixed the nano­worms with the cells for 24h and then shone a special laser on them that produced heat. This made the cells less alive, and when they checked the cells later, they saw that the higher the amount of nanoworms, the less alive the cells were. Moreover, Li et al. [52] conducted a study using special nanoparticles known as GNRs@ PDA−PEG NPs to treat cancer cells and tumors. They coated these nanoparticles with a substance called DOX.In Fig. 4.1e they examined the light absorption of these nanoparticles, and they noticed a small peak in the spectrum that matched the absorption of DOX.In vitro experiments were involved evaluating the photothermal efciency of GNRs-based nanocomposites upon exposure to an 808nm diode laser. The stability of the photothermal effect was examined through four on/off laser cycles, demonstrating consistent temperatures in Fig.4.1f. The correlation between pH, laser irradiation, and DOX release prole was unveiled in pioneering studies shown in Fig.4.1g. Evaluation in nude mice with xenografts demonstrated the anti­cancer efcacy of GNRs@PDA-PEG-DOX nanocomposites. In vivo photothermal impact and PA imaging led to random grouping of xenograft-bearing mice (Fig.4.1j,

tumor- bearing mice and administered DC@BPBBT dots and BPBBT dots intrave­nously to explore the synergistic effects of mild photothermal therapy and immuno­therapy, as demonstrated in Fig.4.3d. Mice received either DC@BPBBT dots or BPBBT dots (1mgkg−1) through intravenous injection. Subsequently, the tumors were subjected to 808 nm laser treatment after 24 h, maintaining a comfortable temperature (42°C) for 5min. The tumor’s progression was tracked by measuring its size every 2days, as depicted in Fig.4.3e. Remarkably, after treatment with DC@BPBBT dots and mild photothermal therapy (42°C), there were no noticeable uctuations in the body weight of the mice over the course of several days, as illus­trated in Fig.4.3f. This study effectively demonstrated an innovative solution that tackles the challenge of heat-induced resistance and offers a promising approach for cancer treatment by harnessing photothermal therapy and interactions with immune cells. Li etal. [71] employed PTT to induce immunogenic cell death (ICD) in can­cer cells, a phenomenon where dying tumor cells release molecules that attract immune cells and trigger a robust immune response. The researchers delved into the impact of PTT on key ICD-related signals, including calreticulin exposure, HMGB1 release, and ATP secretion. They utilized NPs loaded with indocyanine green (ICG) and NLG919, named CFIN, to enhance the ICD effect driven by PTT. Upon expo­sure to an 808 nm laser, the CFIN NPs effectively targeted and eradicated 4T1 cancer cells, resulting in heightened CRT exposure, HMGB1 release, and ATP secretion, signifying the activation of ICD pathways. These ICD signals play a piv­otal role in drawing immune cells, particularly dendritic cells (DCs), which are instrumental in initiating immune responses. CFIN treatment led to DC maturation and an increase in cytotoxic T lymphocytes (CTLs). Furthermore, CFIN curbed the activity of IDO-1, an enzyme responsible for immune suppression within the TME. The amalgamation of PTT with immunotherapy generated a more potent immune response, evidenced by increased secretion of cytokines TNF-α, IL-6, and IFN-γ, which are associated with activating cellular immunity, fostering immune cell proliferation, and regulating antitumor immunity. In vivo experiments using a bilateral 4T1 tumor model underscored the signicance of CFIN treatment, espe­cially in conjunction with PTT, in markedly impeding the growth of both primary and distant tumors. This approach showcases the potential of synergizing photother­mal and immunotherapeutic effects to enhance antitumor responses. Xiao etal. [72] introduced an innovative approach to enhance colorectal cancer immunotherapy by integrating immune checkpoint blockade and PTT. They developed NPs known as PDA/GNS@aPD-L1 NPs, composed of photothermal nanoparticles coated with a cell membrane containing anti- PD- L1 antibodies. This design aimed to disrupt immunosuppressive signals through PD-1/PD-L1 blockade and induce targeted tumor cell destruction upon laser irradiation. The NPs effectively accumulated at tumor sites due to their tumor-targeting capability. Upon laser irradiation, the NPs generated heat, causing tumor cell ablation and promoting tumor vascular permea­bility. Spectroscopic analysis demonstrated the high NIR absorption of PDA/GNS@ aPD-L1 NPs compared to plain PDA-GNS (Fig.4.4c). Furthermore, the membrane- coated NPs maintained their photothermal conversion efciency. Under 808-nm laser irradiation, the PDA/GNS@aPD-L1 NP solution rapidly reached

Cheng etal. [85] aimed to develop a new class of nanomaterials for cancer treat­ment. They selected 2D nanosheets made of tungsten disulde (WS2), which shows strong near-infrared light absorption capabilities. To enhance their biocompatibility and stability within biological systems they have coated the nanosheets with poly­ethylene glycol (PEG). To determine their potential as cancer treatments, the researchers conducted a series of in-depth studies. They rst tested the nanosheet’s toxicity invitro by exposing various cell lines to it. Surprisingly, the nanosheets