In addition to having limited side effects and being a high-efficiency cancer treatment, photothermal therapy (PTT) has the advantage of minimizing the risk of damage to normal tissues (Doughty et al., 2019). Photothermal agents (PTA) are the principal element in photothermal absorption, which plays an important role in PTT (Hwang and Jung, 2021). The basic principle of PTT is to use PTA to generate enough heat under the irradiation of near-infrared (NIR) and other external light sources to destroy and eliminate cancer cells, in which the strong light absorption and high photothermal conversion efficiency of PTA are the keys to the success of PTT (Nasseri et al., 2022). When the cancer tissue temperature reach to 42°C, this leads to local tissue irreversible damage, and with the increase of the reaction temperature, the following reactions will occur: protein denaturation; DNA synthesis weakening; oxygen-depletion; and pH levels dropping (Yu et al., 2020). Eventually, PTT effectively inhibits tumor recurrence and metastasis. In conclusion, compared with the traditional treatment of tumors, PTT has become one of the most promising and effective cancer treatments.

Photodynamic therapy (PDT) is a therapeutic modality for the local treatment of disease that requires the eradication of pathological cells based on the interaction of light, a photosensitizer (PS), and oxygen (Abrahamse et al., 2017). PDT treatment consists of three steps: first, the controlled PS forms selective endocytosis and retention in tumor cells; second, the PS is excited by light of the appropriate wavelength to release ROS, which includes singlet oxygen (¹O₂), peroxide (O₂ ²⁻), superoxide (O²⁻), and hydroxyl radical (•OH), leading to the apoptosis, necrosis, and autophagy in cancer cells; third, PDT motivates a number of immune responses to cause inflammatory cells (Wang et al., 2021a). The PDT process destroys tumors through a variety of mechanisms, including the apoptosis and necrosis of neoplastic cells, the degeneration or shut-down of tumor blood supply, the stimulation of anti-tumor immune responses, and the induction of inflammation in the treated location. PDT has been regarded as an alternative therapy option, having remarkable therapeutic effects, leading to it being applied in cancers of various types and locations of therapy (Mansoori et al., 2019).

Chemodynamic therapy (CDT) has emerged as a cutting-edge and effective cancer treatment method that can produce highly harmful hydroxyl radicals (•OH) from endogenous hydrogen peroxide (H₂O₂) under the presence of catalysts via a Fenton or Fenton-like reaction utilizing the unique feature of tumor microenvironments to eradicate cancer cells that can cause DNA necrosis, protein inactivation, lipid oxidation, and finally induce cell apoptosis or necrosis (Wang et al., 2020; Yang and Liu, 2020). In addition, Fenton and Fenton-like reactions can also produce O₂, which can relieve the hypoxia and antioxidant capability of the tumor (Li et al., 2021). Furthermore, with a huge influx of “All-in-One” theranostic nano-agents, it is usually combined with chemotherapy, radiotherapy, phototherapy, sonodynamic therapy, and immunotherapy, which can not only improve the comprehensive synergistic therapeutic effect of cancer, but also enhance the anti-cancer therapeutic effect. In short, CDT presents a new route of treatment for highly efficient cancer theranostics.

One of the most important and significant potential opportunities in targeted drug delivery treatment modalities and diagnostic agents is nanoscale drug delivery systems (NDDS). In recent years, numerous chemotherapeutic drugs, inhibitors, vaccinations, proteins, and contrast agents have all been introduced. NDDS may be categorized into pH-sensitive delivery systems, enzyme-sensitive delivery systems, thermo-sensitive delivery systems, redox-sensitive delivery systems, and light-sensitive delivery systems, based on the unique features of the diseased microenvironment (Dheer et al., 2019; Li et al., 2019; Mirhadi et al., 2020). In addition, a variety of NDDS formulations, such as liposomes, nanoparticles, micelles, etc., have been designed as innovative cancer therapies. Especially in the area of tumor-targeted therapy, NDDS can not only resolve MDR and the recurrence of malignant tumors but also modify the immune response to improve the treatment of MDR cancer, providing more inspiration and thoughts for the precise treatment of tumors in the next stage (Wei et al., 2016).

Nanodots, ranging in size from 2 to 20 nm, are among the most representative LDNs, due to the characteristics of their chemical or physical properties, such as the low cost of synthesis, small size, low toxicity, excellent biocompatibility, chemical stability, and some attractive newly emerging properties, leading to them being at the forefront of cancer diagnostic imaging (Zou et al., 2017; Jia et al., 2018).

Lei et al. (2017) successfully synthesized ultrasmall poly-protected bismuth nanodots via an ultrafine strategy (Table 1). Due to their significant near-infrared absorption, nanodots exhibit outstanding photothermal conversion efficiency and can be used as a nano theranostic agent for PTT. Additionally, PVP-Bi nanodots demonstrate photothermal imaging and computed tomography (CT) imaging characteristics, which might successfully promote the PTT process. Additionally, PVP-Bi nanodots have high biocompatibility and low cytotoxicity in in vitro and in vivo experiments, indicating their excellent reliability for cancer imaging and treatment (Lei et al., 2017). In this direction, Li et al. (2017a) investigated ultrasmall PEG–Bi₂S₃ nanodots prepared according to a “hot injection” method (Table 1). Due to the presence of the Bi element with a larger X-ray attenuation coefficient, PEG–Bi₂S₃ nanodots possess the capacity for CT imaging. Additionally, Bi₂S₃ is a semiconductor with a low energy gap that exhibits significant NIR absorption. As a result, Bi₂S₃ might perform as a highly productive CT/PTT dual-functional agent by itself for imaging-guided photothermal therapy for effective and reliable cancer treatment (Li et al., 2017a). In their study, Xu et al. (2018) suggested that monodisperse Gd/Ru@BSA nanodots could be successfully synthesized through a simple protocol with high photothermal conversion efficiency, which achieved a significant efficacy for anti-cancer therapy under PTT both in vitro and in vivo (Table 1). Meanwhile, Gd/Ru@BSA nanodots exhibit superior T1-weighted magnetic resonance (MR) imaging ability to evaluate the treatment effect (Xu et al., 2018). Furthermore, Xu et al. (2019) found that phthalocyanine-based nanodots (ZnPc-NDs) have dual synergistic photodynamic/photothermal effects to realize the diagnostic function, demonstrated by HeLa tumor both in vitro and in vivo (Table 1). Gd(III) on the surface of nanodots provided magnetic resonance performances, having achieved magnetic resonance imaging-guided tumor phototherapy. The as-prepared nanodots, regarded as powerful and safe nano theranostic agents, have great clinical promise for cancer nano-imaging-guided theranostic nanoplatforms (Xu et al., 2019).

One-dimensional (1D) nanostructures with characteristic surface-to-volume and aspect ratios, such as nanowires (NWs), nanobelts (NBs), nanoneedles (NNs), nanorods (NRs), nanotubes (NTs) (Contreras-Torres et al., 2022), and nanofibers (NFs), which might adsorb or conjugate to various therapeutic compounds, have a significant benefit in terms of disease diagnostics, monitoring, and efficacy evaluation (Roehlecke and Schmidt, 2020).

Chen et al. (2019) discovered that Ag/BaGdF₅: Yb³⁺, Er³⁺ nanocomposites, synthesized by Ag nanowires and PVP-modified BaGdF₅: Yb³⁺, Er³⁺ spherical nanoparticles via convenient solvothermal and hydrothermal procedure, exhibit remarkable performance on photothermal conversion and CT/MR imaging efficiency (Table 1). Further evidence of the PTT effect was validated by Hela cells under a 808 nm laser. Meanwhile, CT/MR was used for the assessment of cancer therapeutic effects. Experimental results showed that the obtained nanoparticles not only possess an extraordinary photothermal conversion effect but also an excellent imaging capability for CT/MR (Chen et al., 2019). In this direction, Sun et al. (2019) investigated silicon nanowires decorated with gold nanoparticles (Si–Au) that were synthesized via a simple and convenient method (Table 1). Si–Au showed a good photothermal effect under NIR-I in in vitro and in vivo experiments, and it also demonstrated highly efficient PA imaging under NIR-II in 4T1 to guide photothermal cancer therapy (Sun et al., 2019). Due to the abundant surface binding sites in 1D nanomaterials, they can conjugate to various therapeutic molecules. In this direction, Peng et al. (2014) synthesized silicon nanowires (SiNWs) of large-area porous structures with high drug-loading capacity through a facile route and loaded doxorubicin (DOX) to remove drug-resistant cancer cells (Table 1). In vitro experiments showed that nanoparticles with a low RF value are extremely effective for reversing drug resistance. SiNWs-DOX solves the question of cancer resistance to the drugs and prevents blindly using the medicine (Peng et al., 2014). Additionally, as observed in some research, 1D nanomaterials have characteristic surface-to-volume and aspect ratios, making them potential carriers of biomolecules and chemotherapeutic medications for various cancer-related treatments (García-Hevia et al., 2016).

Among nanomaterials, 2D nanomaterials (2D-NMs) have gained considerable interest from researchers due to their physical and chemical properties, including their planar structure, ultra-thin thickness, and ease of functionalization (Mohammadpour and Majidzadeh, 2020). Furthermore, 2D-NMs are capable of adsorbing or conjugating various contrast agents, enabling rapid multimodal imaging with a quick turnaround time, as well as the detection of tumors and metastases (Ashfaq et al., 2022).

Chen et al. (2017) summarized Pd@Au, Pd@Ag nanoplates, and mesocrystalline Pd nanocorolla applications in cancer diagnosis and therapy (Table 1). The different forms of 2D Pd nanosheets were used to carry out extensive research because of their many benefits. The main advantages are a large surface area, strong absorption in the NIR region, high photothermal conversion efficiency, high photothermal stability, and excellent PA or CT imaging capability. Experimental results indicated that the combination of PTT/chemotherapy and PTT/PDT therapy achieved high synergistic therapeutic effects, realizing PA and CT imaging-guided PTT for cancer treatment (Chen et al., 2017). Another successful implementation of manganese dioxide nanosheets (MnO₂ NSs) is presented in the work of Zhao et al. (2014), where MnO₂ NSs were employed for MRI bimodal tumor cell imaging (Table 1). Moreover, Xie et al. (2019) discovered that Ti nanosheets (NSs) exfoliated through simple methods (Table 1). The experiment confirmed that TiNSs-PEG possesses excellent light absorbance, preeminent photothermal performance, and stability. Therefore, TiNSs-PEG combined with PTT can achieve high tumor cell-killing efficiency. The effectiveness of treatment can be assessed using dual-modal contrast-enhanced PA and CT imaging (Xie et al., 2019). Tang et al. (2019) synthesized MnO₂ nanosheets (M-NSs) for a tumor-targeted multimodal diagnostic imaging probe via a one-step wet-chemical method. Through the surface functionalization of the M-NSs, 64Cu radionuclides were successfully chelated onto nanoparticles to achieve PET imaging. In addition, the obtained nanomaterials not only possessed a good photothermal therapeutic effect but also realized effective photoacoustic-imaging-guided synergistic starvation-enhanced photothermal therapy (Tang et al., 2019). Zhang et al. (2020) designed MUCNPs@BPNs-Ce6 nanocomposites for tumor phototherapy guided by multimodal imaging. BPNs and Ce6, as a component of nanomaterials with high photothermal conversion efficiency, were employed to promote PTT and PDT under a single irradiation light of 808 nm. In addition, Fe₃O₄ and MnO₂ nanoparticles realized T1/T2-weighted magnetic resonance imaging, and Ce6 has the capability of fluorescence imaging. It was proved by experiments that the bubbles produced by H₂O₂ decomposition in the tumor microenvironment could be used for ultrasound imaging. Further, MnO₂ can transform excess H₂O₂ in the tumor microenvironment into O₂ to enhance PDT. The obtained MUCNPs@BPNs-Ce6 not only enhances the therapeutic effect of PDT/PTT but also enables multimodal imaging to evaluate the therapeutic effect of cancer in real-time (Zhang et al., 2020). The development of effective diagnostic and cancer therapies relies on the development of 2D nanomaterials, which are constantly expanding. Therefore, the development of 2D-NMs will improve clinical decision-making and advance precision medicine (Li et al., 2017b; Wang et al., 2017; Zhao et al., 2022; Zhao et al., 2023).