Polydopamine‐mediated polypyrrole/doxorubicin nanocomplex for chemotherapy‐enhanced photothermal therapy in both NIR‐I and NIR‐II biowindows against tumor cells

Recent advances in smart gold nanoparticles for photothermal therapy

Gold nanoparticles (AuNPs) possess unique properties, including low toxicity and excellent optical characteristics, making them highly appealing for biomedical applications. The plasmonic photothermal effect of AuNPs has been explored to trigger localized hyperthermia. Four commonly explored gold nanoparticles (spheres, rods, stars, and cages) are produced and optimized to present the localized surface plasmon resonance effect in the near-infrared region, exploiting the increased penetration in the human body. Additionally, the production of hybrid AuNPs, combining them with other materials, such as silica, graphene, zinc oxide, polymers, and small molecules has been explored to amplify the photothermal effect (T ≥ 45ºC). This review provides an overview of AuNPs' application in photothermal therapy, describing the general synthesis processes and the main particle parameters that affect their application in photothermal therapy, including the hybrid nanomaterials. Associated with this rapid progress, surface functionalization can also improve colloidal stability, safety, and therapeutic outcomes. In this regard, we also highlight the emerging trend of applying cell-derived vesicles as biomimetic coatings, capable of evading immune recognition, increasing blood circulation, and targeting specific tissues. In addition, the challenges and future developments of AuNPs for accelerating the clinical translations are discussed in light of their therapeutic and theragnostic potential.

Dumbbell-shaped bimetallic AuPd nanoenzymes for NIR-II cascade catalysis-photothermal synergistic therapy

The noble metal NPs that are currently applied to photothermal therapy (PTT) have their photoexcitation location mainly in the NIR-I range, and the low tissue penetration limits their therapeutic effect. The complexity of the tumor microenvironment (TME) makes it difficult to inhibit tumor growth completely with a single therapy. Although TME has a high level of H2O2, the intratumor H2O2 content is still insufficient to catalyze the generation of sufficient hydroxide radicals (‧OH) to achieve satisfactory therapeutic effects. The AuPd-GOx-HA (APGH) was obtained from AuPd bimetallic nanodumbbells modified by glucose oxidase (GOx) and hyaluronic acid (HA) for photothermal enhancement of tumor starvation and cascade catalytic therapy in the NIR-II region. The CAT-like activity of AuPd alleviates tumor hypoxia by catalyzing the decomposition of H2O2 into O2. The GOx-mediated intratumoral glucose oxidation on the one hand can block the supply of energy and nutrients essential for tumor growth, leading to tumor starvation. On the other hand, the generated H2O2 can continuously supply local O2, which also exacerbates glucose depletion. The peroxidase-like activity of bimetallic AuPd can catalyze the production of toxic ‧OH radicals from H2O2, enabling cascade catalytic therapy. In addition, the high photothermal conversion efficiency (η = 50.7 %) of APGH nanosystems offers the possibility of photothermal imaging-guided photothermal therapy. The results of cell and animal experiments verified that APGH has good biosafety, tumor targeting, and anticancer effects, and is a precious metal nanotherapeutic system integrating glucose starvation therapy, nano enzyme cascade catalytic therapy, and PTT therapy. This study provides a strategy for photothermal-cascade catalytic synergistic therapy combining both exogenous and endogenous processes. STATEMENT OF SIGNIFICANCE: AuPd-GOx-HA cascade nanoenzymes were prepared as a potent cascade catalytic therapeutic agent, which enhanced glucose depletion, exacerbated tumor starvation and promoted cancer cell apoptosis by increasing ROS production through APGH-like POD activity. The designed system has promising photothermal conversion ability in the NIR-II region, simultaneously realizing photothermal-enhanced catalysis, PTT, and catalysis/PTT synergistic therapy both in vitro and in vivo. The present work provides an approach for designing and developing catalytic-photothermal therapies based on bimetallic nanoenzymatic cascades.

pH-Responsive Au@Pd bimetallic core-shell nanorods for enhanced synergistic targeted photothermal-augmented nanocatalytic therapy in the second near-infrared window

Nanotheranostic agents based on plasmonic nanostructures with their resonance wavelengths located in the second near-infrared window (NIR-II) have gained significant attention in profound tumor photothermal therapy. However, the modulation of localized surface plasmon resonance of gold nanomaterials from the first near-infrared (NIR-I) window to the NIR-II window is still challenging. The structures and compositions of the plasmonic nanomaterials have demonstrated promising characteristics in controlling the optical properties of plasmonic nanostructures. Here, gold nanorod (Au NR) coated with an ultrathin palladium (Pd) shell was developed for tumor-targeted NIR-II photothermal-augmented nanocatalytic therapy through the combination of compositional manipulation and structural evolution strategies. These Au@Pd core-shell hybrid NRs (HNRs) were functionalized with biocompatible chitosan (CS) to acquire lower toxicity and higher stability in physiological systems. Further, Au@Pd-CS HNRs were endowed with an excellent targeting ability by conjugating with folic acid (FA). The as-synthesized Au@Pd-CS-FA HNRs show efficient and complete photothermal ablation of tumor cells upon 1064 nm laser irradiation. The remarkable photothermal conversion efficiency of 69.0% was achieved, which is superior to many reported photothermal agents activated in the NIR-II region. Excitingly, Au@Pd-CS-FA HNRs have peroxidase and catalase activities, simultaneously producing ˙OH for catalytic therapy and O₂ for relieving tumor hypoxia and photodynamic therapy. Additionally, in vivo tumor photothermal therapy was carried out, where the biocompatible Au@Pd-CS-FA HNRs penetrate intensely into the tumor cells and consequently show remarkable therapeutic effects. The idea about plasmonic modulation behind the bimetallic core-shell nanostructure in this report can be extended to construct new classes of metal-based nanotheranostic agents with dual-modal combined therapy as an alternative to traditional chemotherapy.

NIR -I and NIR-II irradiation tumor ablation using NbS2 nanosheets as the photothermal agent

Photothermal therapy has been considered a powerful means of cancer therapy due to its minimal invasiveness, effectiveness, and convenience. Although promising, the therapeutic effects are greatly limited as they rely on the photothermal agent (PTA). It is urgent to develop new PTAs with high photothermal conversion performance, especially under irradiation in the long-wavelength biowindows. Herein, a dual-biowindow-responsive PTA made of NbS₂-PVP nanosheets was fabricated to be used both in the first near-infrared (NIR-I) and the second near-infrared (NIR-II) biowindows. With excellent hydrophilicity and biocompatibility, the nanosheets could effectively convert the near-infrared (NIR) light into heat, showing prominent photothermal stability. The calculated photothermal conversion efficiencies reached 59.2% (under NIR-I excitation) and 69.1% (under NIR-II excitation), respectively, which are comparable to those of metallic PTAs. The NbS₂-PVP nanosheets had low cytotoxicity and could trigger strong photothermal treatment and cause cancer cell death upon irradiation by NIR-I or NIR-II light in vitro. Moreover, we have also demonstrated the highly efficient tissue ablation and tumor inhibition capability of NbS₂-PVP nanosheets in vivo. This work explores an effective PTA of two-dimensional nanomaterials in NIR-I and NIR-II biowindows and offers a reference for the design of new kinds of PTAs.

Triformyl cholic acid and folic acid functionalized magnetic graphene oxide nanocomposites: Multiple-targeted dual-modal synergistic chemotherapy/photothermal therapy for liver cancer

Photo-chemotherapy (PCT) reveals great potential in hepatocellular carcinoma (HCC) treatment, therefore the construct of smart PCT nano-agents with high photothermal conversion efficiency and accurate drug delivery is of great significant. Herein, a novel hybrid nanomaterial MGO-TCA-FA has been designed and constructed by grafting the triformyl cholic acid (TCA) and folic acid (FA) on the surface of Fe3O4 modified graphene oxide (MGO). The doxorubicin hydrochloride (DOX) as a model drug could be effectively loaded on the MGO-TCA-FA via hydrogen bonding and π-π stacking (the drug loading amount was 1040 mg/g). The formed MGO-TCA-FA@DOX has been developed to be an effective PCT nanoplatform with the advantages of multiple-targeted drug delivery, near-infrared light (NIR) and pH triggered drug release, and photothermal conversion efficiency. In vitro experiments showed that compared with other cancer cells and normal liver cells, MGO-TCA-FA@DOX could specifically target liver cancer cells and presented significant killing ability to liver cancer cells. More importantly, in vivo experiments indicated that PCT synergistic therapy (MGO-TCA-FA@DOX) revealed the best tumor inhibition (the tumor inhibition rate was about 85%) compared with chemotherapy and photothermal therapy alone. Thus, this study supplied a viable multiple-targeted PCT nano-agent for chemo-photothermal combination therapy of liver cancer.

Gold Nanorod-Melanin Hybrids for Enhanced and Prolonged Photoacoustic Imaging in the Near-Infrared-II Window

Photoacoustic (PA) imaging holds great promise as a noninvasive imaging modality. Gold nanorods (GNRs) with absorption in the second near-infrared (NIR-II) window have emerged as excellent PA probes because of their tunable optical absorption, surface modifiability, and low toxicity. However, pristine GNRs often undergo shape transition upon laser illumination due to thermodynamic instability, leading to a reduced PA signal after a few seconds of imaging. Here, we report monodisperse GNR-melanin nanohybrids where a tunable polydopamine (PDA) coating was conformally coated on GNRs. GNR@PDAs showed a threefold higher PA signal than pristine GNRs due to the increased optical absorption, cross-sectional area, and thermal confinement. More importantly, the PA signal of GNR@PDAs only decreased by 29% during the 5 min of laser illumination in the NIR-II window, while significant attenuation (77%) was observed for GNRs. The GNR@PDAs maintained 87% of its original PA signal in vivo even after 10 min of laser illumination. This PDA-enabled strategy affords a rational design for robust PA imaging probes and provides more opportunities for other types of photomediated biomedicines, such as photothermal and photodynamic regimens.

Polydopamine-Coated Laponite Nanoplatforms for Photoacoustic Imaging-Guided Chemo-Phototherapy of Breast Cancer

Theranostic nanoplatforms combining photosensitizers and anticancer drugs have aroused wide interest due to the real-time photoacoustic (PA) imaging capability and improved therapeutic efficacy by the synergistic effect of chemotherapy and phototherapy. In this study, polydopamine (PDA) coated laponite (LAP) nanoplatforms were synthesized to efficiently load indocyanine green (ICG) and doxorubicin (DOX), and modified with polyethylene glycol-arginine-glycine-aspartic acid (PEG-RGD) for PA imaging-guided chemo-phototherapy of cancer cells overexpressing α_vβ₃ integrin. The formed ICG/LAP-PDA-PEG-RGD/DOX nanoplatforms showed significantly higher photothermal conversion efficiency than ICG solution and excellent PA imaging capability, and could release DOX in a pH-sensitive and NIR laser-triggered way, which is highly desirable feature in precision chemotherapy. In addition, the ICG/LAP-PDA-PEG-RGD/DOX nanoplatforms could be uptake by cancer cells overexpressing α_vβ₃ integrin with high specificity, and thus serve as a targeted contrast agent for in vivo PA imaging of cancer. In vivo experiments with 4T1 tumor-bearing mouse model demonstrated that ICG/LAP-PDA-PEG-RGD/DOX nanoplatforms exhibited much stronger therapeutic effect and higher survival rate than monotherapy due to the synergetic chemo-phototherapy under NIR laser irradiation. Therefore, the reported ICG/LAP-PDA-PEG-RGD/DOX represents a promising theranostic nanoplatform for high effectiveness PA imaging-guided chemo-phototherapy of cancer cells overexpressing α_vβ₃ integrin.

Second near-infrared photothermal materials for combinational nanotheranostics

This review summarizes the recent development of second near-infrared photothermal combinational nanotheranostics for cancer, infectious diseases and regenerative medicine.