Activatable NIR-II Plasmonic Nanotheranostics for Efficient Photoacoustic Imaging and Photothermal Cancer Therapy

A phosphomolybdenum blue nano-photothermal agent with dual peak absorption and biodegradable properties based on ssDNA in near-infrared photothermal therapy for breast cancer

Photothermal therapy (PTT) stands as an emerging and promising treatment modality and is being developed for the treatment of breast cancer, prostate cancer, and a series of superficial tumors. This innovative approach harnesses photothermal agents (PTAs) that convert near-infrared light (NIR) energy into heat, efficiently heating and ablating localized lesion tissue. Notably, the low scattering of NIR-II (1000-1500 nm) band light within biological tissue ensures superior penetration depth, surpassing that of NIR I (700-900 nm) band light. Consequently, developing PTAs with excellent absorption performance and biocompatibility in the NIR-II band has attracted significant attention in photothermal therapy research. We successfully synthesized phosphomolybdenum blue (PMB) nanoparticles using single-strand DNA (ssDNA) as a template in this innovative study. Subsequently, we delved into this material's absorption characteristics and photothermal properties across the NIR-I and NIR-II spectral regions. Furthermore, we evaluated the therapeutic efficacy of PMB on 4T1 cells and tumor-bearing mouse models of breast cancer. Our findings revealed that PMB not only exhibits remarkable biocompatibility but also possesses stellar photothermal performance. Specifically, under 808 nm and 1064 nm laser irradiation, PMB achieved photothermal conversion efficiencies of 21.37% and 28.84%, respectively. Notably, compared to 808 nm laser irradiation, even when transmitting through a 2 mm thick tumor tissue homogenate, the 1064 nm laser irradiation maintained a robust tumor ablation effect. What's more, PMB possesses critical pH-responsive degradation properties. For instance, PMB nanoparticles degrade rapidly under physiological conditions (pH 7.2-7.4) while degrading slower in the acidic tumor microenvironment (pH 6.0-6.9). This unique characteristic significantly mitigates the systemic toxicity of PMB and enhances the safety of photothermal therapy implementation. Moreover, our study represents the first instance of utilizing ssDNA as a template for synthesizing a PMB nano photothermal agent and demonstrating its exceptional tumor thermal ablation efficacy. This groundbreaking work offers novel insights into the development of safe, efficient, and pH-responsive photothermal agents for cancer therapy.

Bipyramidal gold nanoparticles-assisted plasmonic photothermal therapy for ocular applications

Gold nanoparticles (AuNPs) play a key role in the field of nanomedicine due to their fascinating plasmonic properties as well as their great biocompatibility. An intriguing application is the use of plasmonic photothermal therapy (PPTT) mediated by anisotropic AuNPs irradiated with a near-infrared (NIR) laser for treating ocular diseases in ophthalmology. For this purpose, bipyramidal-shaped AuNPs (BipyAu), which were surface-functionalized with three different organic ligands (citrate, polystyrene sulphonate (PSS), and cetyltrimethylammonium bromide (CTAB)), were synthesized. The long-term storage stability was assured, in terms of minimal variation in aspect ratio and localized surface plasmon resonance. Better performance was achieved with BipyAu@citrate and BipyAu@PSS NPs. PPTT experiments mediated with the synthesized BipyAu NPs demonstrated that BipyAu@citrate provided the highest value of temperature increase (40 °C at 2.0 W cm-2) after 15 min of 808 nm NIR laser irradiation. The potential future clinical application in ophthalmology was assessed by in vitro cytotoxicity analysis, confirming that BipyAu@citrate NPs were biocompatible for the three major corneal cell types. Furthermore, ex vivo analysis was performed by treating pig corneas with BipyAu@citrate NPs (0.18 μg Au) and subsequent NIR laser irradiation at 808 nm for 15 min, showing distortions in the collagen type I fibrils at the ultrastructural level and promoting the flattening of the corneal surface after treatment, without inducing cell cytotoxicity. This work suggests that a precise control of the fibril distortions can be provoked by PPTT mediated with BipyAu@citrate in the NIR region, paving the way for nanomedicine to correct common deficiencies in corneal diseases.

Applications of nanotheranostics in the second near-infrared window in bioimaging and cancer treatment

Achieving accurate and efficient tumor imaging is crucial in the field of tumor treatment, as it facilitates early detection and precise localization of tumor tissues, thereby informing therapeutic strategies and surgical interventions. The optical imaging technology within the second near-infrared (NIR-II) window has garnered significant interest for its remarkable benefits, such as enhanced tissue penetration depth, superior signal-to-background ratio (SBR), minimal tissue autofluorescence, reduced photon attenuation, and lower tissue scattering. This review explained the design and optimization strategies of nano-agents responsive to the NIR-II window, such as single-walled carbon nanotubes, quantum dots, lanthanum-based nanomaterials, and noble metal nanomaterials. These nano-agents enable non-invasive, deep-tissue imaging with high spatial resolution in the NIR-II window, and their superior optical properties significantly improve the accuracy, efficiency, and versatility of imaging-guided tumor treatments. And we discussed the characteristics and advantages of fluorescence imaging (FL)/photoacoustic imaging (PA) in NIR-II window, providing a comprehensive overview of the latest research progress of different nano-agents in FL/PA imaging-guided tumor therapy. Furthermore, we exhaustively reviewed the latest applications of multifunctional nano-phototherapy technologies carried out by NIR-II light including photothermal therapy (PTT), photodynamic therapy (PDT), and combined modalities like photothermal-chemodynamic therapy (PTT-CDT), photothermal-chemotherapy (PTT-CT), and photothermal- immunotherapy (PTT-IO). These imaging-guided integrated tumor therapy approaches within the NIR-II window have gradually matured over the past decade and are expected to become a safe and effective non-invasive tumor treatment. Finally, we outlined the prospects and challenges of development and innovation of the NIR-II integrated diagnosis and therapy nanoplatform. This review aims to provide insightful perspectives for future advancements in NIR-II optical tumor diagnosis and integrated treatment platforms.

Recent progress in gold-derived nanomaterials for tumor theranostics

It is widely acknowledged that gold-based materials are of significant interest in the field of biomedicine. Consequently, considerable efforts have been devoted to identifying gold nanoparticles that exhibit effective performance in tumor diagnosis and treatment. However, the underlying reasons for the enhanced efficacy of these gold-based nanomaterials in cancer therapy and diagnosis remain unclear, primarily due to the lack of an in-depth understanding of the mechanisms involved. Therefore, it is essential to summarize the progress in the field to facilitate the rational design of more efficient nanodevices. In this review, we present recent achievements drawn from the latest research to demonstrate the broad applications of gold-based materials. We begin by illustrating the mechanisms of gold-derived nanoparticles during therapeutic and diagnostic processes, including photothermal therapy, photodynamic therapy, sonodynamic therapy, photoacoustic tomography, fluorescence imaging, and X-ray computed tomography. We then summarize the advancements of gold-based nanomaterials in cancer diagnosis and treatment while also analyzing the factors contributing to their enhanced performance. Finally, we highlight key descriptors for evaluating the efficacy and strategies for designing high-performance nanomaterials. This review aims to pave the way for addressing future challenges and outlines directions for the advancement of gold-based biomedicine.

Carrier-Free Biomimetic Organic Nanoparticles with Super-High Drug Loading for Targeted NIR-II Excitable Triple-Modal Bioimaging and Phototheranostics

Multimodal near-infrared II (NIR-II) theranostics combined with nanotechnology have emerged as promising treatments for cancer due to their noninvasive and high spatiotemporal nature. Traditional NIR-II theranostics typically comprise useless and massive inert carriers, resulting in low drug loading capacity, reduced therapeutic effects, and potential biotoxicity. To overcome these limitations, this work reports carrier-free NIR-II theranostics simultaneously with high drug loading capacity and multimodal NIR-II imaging capabilities for cancer phototheranostics in the NIR-II window. Carrier-free BTA nanoparticles (NPs) are prepared by self-assembling the NIR-II responsive conjugated oligomer BTA without adding coating agents; these NPs exhibited 100% drug loading and high-performance NIR-II theranostic capabilities. Cancer cell membranes are camouflaged on carrier-free BTA NPs to provide homologous targeting ability, enhanced stability, and 77.8% drug loading. Both in vitro and in vivo studies have indicated that biomimetic NPs provide efficient triple-modal guidance for NIR-II fluorescence, photoacoustic, and photothermal imaging and complete tumor elimination via photothermal therapy (PTT). Additionally, theranostics-based treatments with good biosecurity are demonstrated. This study contributes a new strategy for the design of high-drug-loading NIR-II theranostics and further promotes the clinical translation of theranostic agents.

Microenvironment-Activatable Probe for Precise NIR-II Monitoring and Synergistic Immunotherapy in Rheumatoid Arthritis

Rheumatoid arthritis (RA) represents an insidious autoimmune inflammatory disorder that severely lowers the life quality by progressively destructing joint functions and eventually causing permanent disability, posing a serious public health problem. Here, an advanced theranostic probe is introduced that integrates activatable second near-infrared (NIR-II) fluorescence imaging for precise RA diagnosis with multi-pronged RA treatments. A novel molecular probe comprising a long-wavelength aggregation-induced emission unit and a manganese carbonyl cage motif is synthesized, which enables NIR-II fluorescence activation and concurrently releasing therapeutic carbon monoxide (CO) gas in inflamed joint microenvironment. This molecular probe self-assembles into a biocompatible nanoprobe, which is subsequently conjugated with anti-IL-6R antibody to afford active-targeting ability of RA. The nanoprobe exhibits significant turn-on NIR-II fluorescence signal at the RA lesion, enabling highly sensitive RA diagnosis and real-time therapeutic monitoring. The combination of ROS scavenging, on-demand CO gas release, and IL-6 signaling blockade results in potent therapeutic effect and synergistic immunomodulation impact, significantly alleviating the RA symptoms and preventing joint destruction. This research introduces a novel paradigm for the development of high-performance, activatable theranostic strategies to facilitate precise detection and enhanced treatment of RA-related diseases.

Self-Regulated Assembly and Disassembly of Gold Nanoparticles for Low-Temperature Time Indication

The color-changing self-assembly and autonomous disassembly of colloidal gold nanoparticles (AuNPs) is reported by simply mixing negatively charged phosphine ligand-capped AuNPs with partially oxidized polyethylene glycol (PEG). The assembly of AuNPs is initiated by PEG adsorption, which disrupts the hydration layer of AuNPs, leading to depletion attraction and reduction of hydration repulsion among the AuNPs. The oxidative species in PEG subsequently oxidize and remove the charged ligands from the AuNP surface, resulting in a decrease and reversal of the negative surface charge. This causes the PEG to adsorb on AuNPs in a tighter and more direct manner, providing strong steric shielding to the AuNPs, thereby triggering the disassembly of the AuNP assemblies. The self-regulated assembly-disassembly process can be tuned widely by controlling chemical conditions of PEG, nanoparticle concentration, and the environmental conditions, suggesting potential applications as colorimetric time-temperature indicators for food and medicine storage conditions. As a proof of concept, it is demonstrated that the lifetime of the color-changing assembly-disassembly process can be extended from tens of minutes to weeks when subjected to a refrigerated environment, with tunability achievable through varying polymer conditions and storage atmospheres.

NIR-II Surface-Enhanced Raman Scattering Nanoprobes in Biomedicine: Current Impact and Future Directions

The field of second near-infrared (NIR-II) surface-enhanced Raman scattering (SERS) nanoprobes has made commendable progress in biomedicine. This article reviews recent advances and future development of NIR-II SERS nanoprobes. It introduces the fundamental principles of SERS nanoprobes and highlights key advances in the NIR-II window, including reduced tissue attenuation, deep penetration, maximized allowable exposure, and improved photostability. The discussion of future directions includes the refinement of nanoprobe substrates, emphasizing the tailoring of optical properties of metallic SERS-active nanoprobes, and exploring non-metallic alternatives. The intricacies of designing Raman reporters for the NIR-II resonance and the potential of these reporters to advance the field are also discussed. The integration of artificial intelligence (AI) into nanoprobe design represents a cutting-edge approach to overcome current challenges. This article also examines the emergence of deep Raman techniques for through-tissue SERS detection, toward NIR-II SERS tomography. It acknowledges instrumental advancements like improved charge-coupled device sensitivity and accelerated imaging speeds. The article concludes by addressing the critical aspects of biosafety, ease of functionalization, compatibility, and the path to clinical translation. With a comprehensive overview of current achievements and future prospects, this review aims to illuminate the path for NIR-II SERS nanoprobes to innovate diagnostic and therapeutic approaches in biomedicine.

Temperature-Responsive "Nano-to-Micro" Transformed Polymersomes for Enhanced Ultrasound/Fluorescence Dual Imaging-Guided Tumor Phototherapy

The perfect integration of microbubbles for efficient ultrasound imaging and nanocarriers for intelligent tumor-targeting delivery remains a challenge in precise tumor theranostics. Herein, we exquisitely fabricated laser-activated and targeted polymersomes (abbreviated as FIP-NPs) for simultaneously encapsulating the photosensitizer indocyanine green (ICG) and the phase change agent perfluorohexane (PFH). The formulated FIP-NPs were nanosize and effectively accumulated into tumors as observed by ICG fluorescence imaging. When the temperature rose above 56 °C, the encapsulated PFH transformed from liquid to gas and the FIP-NPs underwent balloon-like enlargement without structure destruction. Impressively, the enlarged FIP-NPs fused with adjacent polymersomes to form even larger microparticles. This temperature-responsive "nano-to-micro" transformation and fusion process was clearly demonstrated, and FIP-NPs showed greatly improved ultrasound signals. More importantly, FIP-NPs achieved dramatic antitumor efficacy through ICG-mediated phototherapy. Taken together, the novel polymersomes achieved excellent ultrasound/fluorescence dual imaging-guided tumor phototherapy, providing an optimistic candidate for the application of tumor theranostics.

Remote Control of Energy Transformation-Based Cancer Imaging and Therapy

Cancer treatment requires precise tumor-specific targeting at specific sites that allows for high-resolution diagnostic imaging and long-term patient-tailorable cancer therapy; while, minimizing side effects largely arising from non-targetability. This can be realized by harnessing exogenous remote stimuli, such as tissue-penetrative ultrasound, magnetic field, light, and radiation, that enable local activation for cancer imaging and therapy in deep tumors. A myriad of nanomedicines can be efficiently activated when the energy of such remote stimuli can be transformed into another type of energy. This review discusses the remote control of energy transformation for targetable, efficient, and long-term cancer imaging and therapy. Such ultrasonic, magnetic, photonic, radiative, and radioactive energy can be transformed into mechanical, thermal, chemical, and radiative energy to enable a variety of cancer imaging and treatment modalities. The current review article describes multimodal energy transformation where a serial cascade or multiple types of energy transformation occur. This review includes not only mechanical, chemical, hyperthermia, and radiation therapy but also emerging thermoelectric, pyroelectric, and piezoelectric therapies for cancer treatment. It also illustrates ultrasound, magnetic resonance, fluorescence, computed tomography, photoluminescence, and photoacoustic imaging-guided cancer therapies. It highlights afterglow imaging that can eliminate autofluorescence for sustained signal emission after the excitation.

Near-Infrared-II Nanomaterials for Activatable Photodiagnosis and Phototherapy

Near-Infrared-II (NIR-II) spans wavelengths between 1,000 to 1,700 nanometers, featuring deep tissue penetration and reduced tissue scattering and absorption characteristics, providing robust support for cancer treatment and tumor imaging research. This review explores the utilization of activatable NIR-II photodiagnosis and phototherapy based on tumor microenvironments (e. g., reactive oxygen species, pH, glutathione, hypoxia) and external stimulation (e. g., laser, ultrasound, photothermal) for precise tumor treatment and imaging. Special emphasis is placed on the advancements and advantages of activatable NIR-II nanomedicines in novel therapeutic modalities like photodynamic therapy, photothermal therapy, and photoacoustic imaging. This encompasses achieving deep tumor penetration, real-time monitoring of the treatment process, and obtaining high-resolution, high signal-to-noise ratio images even at low material concentrations. Lastly, from a clinical perspective, the challenges faced by activatable NIR-II phototherapy are discussed, alongside potential strategies to overcome these hurdles.

Doping Engineering To Modulate Surface Plasmon Resonance and Enzyme-like Activities for Enhancing Photoacoustic Imaging-Guided Targeted Cancer Therapy in the Second Near-Infrared Window

Biological imaging-guided targeted tumor therapy has been a soughtafter goal in the field of cancer diagnosis and treatment. To this end, we proposed a strategy to modulate surface plasmon resonance and endow WO3-x nanoparticles (NPs) with enzyme-like catalytic properties by doping Fe2+ in the structure of the NPs. Doping of the Fe2+ introduced oxygen vacancies into the structure of the NPs, inducing a red shift of the maximum absorption wavelength into the near-infrared II (NIR-II) region and enhancing the photoacoustic (PA) and photothermal properties of the NPs for more effective imaging-guided cancer therapy. Under NIR-II laser irradiation, the Fe-WO3-x NPs produced very strong NIR-II PA and photothermal effects, which significantly enhanced the PA imaging and photothermal treatment effects. On the other hand, Fe2+ in Fe-WO3-x could undergo Fenton reactions with H2O2 in the tumor tissue to generate ·OH for chemodynamic therapy. In addition, Fe-WO3-x can also catalyze the above reactions to produce more reactive oxygen species (ROS) and induce the oxidation of NADH to interfere with intracellular adenosine triphosphate (ATP) synthesis, thereby further improving the efficiency of cancer therapy. Specific imaging of tumor tissue and targeted synergistic therapy was achieved after ligation of a MUC1 aptamer to the surface of the Fe-WO3-x NPs by the complexing of -COOH in MUC1 with tungsten ions on the surface of the NPs. These results demonstrated that Fe-WO3-x NPs could be a promising diagnosis and therapeutic agent for cancer. Such a study opens up new avenues into the rational design of nanodiagnosis and treatment agents for NIR-II PA imaging and cancer therapy.

Fused Azulenyl Squaraine Derivatives Improve Phototheranostics in the Second Near-Infrared Window by Concentrating Excited State Energy on Non-Radiative Decay Pathways

The second near-infrared (NIR-II) theranostics offer new opportunities for precise disease phototheranostic due to the enhanced tissue penetration and higher maximum permissible exposure of NIR-II light. However, traditional regimens lacking effective NIR-II absorption and uncontrollable excited-state energy decay pathways often result in insufficient theranostic outcomes. Herein a phototheranostic nano-agent (PS-1 NPs) based on azulenyl squaraine derivatives with a strong NIR-II absorption band centered at 1092 nm is reported, allowing almost all absorbed excitation energy to dissipate through non-radiative decay pathways, leading to high photothermal conversion efficiency (90.98 %) and strong photoacoustic response. Both in vitro and in vivo photoacoustic/photothermal therapy results demonstrate enhanced deep tissue cancer theranostic performance of PS-1 NPs. Even in the 5 mm deep-seated tumor model, PS-1 NPs demonstrated a satisfactory anti-tumor effect in photoacoustic imaging-guided photothermal therapy. Moreover, for the human extracted tooth root canal infection model, the synergistic outcomes of the photothermal effect of PS-1 NPs and 0.5 % NaClO solution resulted in therapeutic efficacy comparable to the clinical gold standard irrigation agent 5.25 % NaClO, opening up possibilities for the expansion of NIR-II theranostic agents in oral medicine.

NIR-Active Gold Dogbone Nanorattles Impregnated in Cationic Dextrin Nanoparticles for Cancer Nanotheranostics

Theranostic systems, which integrate therapy and diagnosis into a single platform, have gained significant attention as a promising approach for noninvasive cancer treatment. The field of image-guided therapy has revolutionized real-time tumor detection, and within this domain, plasmonic nanostructures have garnered significant attention. These structures possess unique localized surface plasmon resonance (LSPR), allowing for enhanced absorption in the near-infrared (NIR) range. By leveraging the heat generated from plasmonic nanoparticles upon NIR irradiation, target cancer cells can be effectively eradicated. This study introduces a plasmonic gold dogbone-nanorattle (AuDB NRT) structure that exhibits broad absorption in the NIR region and demonstrates a photothermal conversion efficiency of 35.29%. When exposed to an NIR laser, the AuDB NRTs generate heat, achieving a maximum temperature rise of 38 °C at a concentration of 200 μg/mL and a laser power density of 3 W/cm2. Additionally, the AuDB NRTs possess intrinsic electromagnetic hotspots that amplify the signal of a Raman reporter molecule, making them an excellent probe for surface-enhanced Raman scattering-based bioimaging of cancer cells. To improve the biocompatibility of the nanorattles, the AuDB NRTs were conjugated with mPEG-thiol and successfully encapsulated into cationic dextrin nanoparticles (CD NPs). Biocompatibility tests were performed on HEK 293 A and MCF-7 cell lines, revealing high cell viability when exposed to AuDB NRT-CD NPs. Remarkably, even at a low laser power density of 1 W/cm2, the application of the NIR laser resulted in a remarkable 80% cell death in cells treated with a nanocomposite concentration of 100 μg/mL. Further investigation elucidated that the cell death induced by photothermal heat followed an apoptotic mechanism. Overall, our findings highlight the significant potential of the prepared nanocomposite for cancer theranostics, combining effective photothermal therapy along with the ability to image cancer cells.

Plasmonic silver and gold nanoparticles: shape- and structure-modulated plasmonic functionality for point-of-caring sensing, bio-imaging and medical therapy

Silver and gold nanoparticles have found extensive biomedical applications due to their strong localized surface plasmon resonance (LSPR) and intriguing plasmonic properties. This review article focuses on the correlation among particle geometry, plasmon properties and biomedical applications. It discusses how particle shape and size are tailored via controllable synthetic approaches, and how plasmonic properties are tuned by particle shape and size, which are embodied by nanospheres, nanorods, nanocubes, nanocages, nanostars and core-shell composites. This article summarizes the design strategies for the use of silver and gold nanoparticles in plasmon-enhanced fluorescence, surface-enhanced Raman scattering (SERS), electroluminescence, and photoelectrochemistry. It especially discusses how to use plasmonic nanoparticles to construct optical probes including colorimetric, SERS and plasmonic fluorescence probes (labels/reporters). It also demonstrates the employment of Ag and Au nanoparticles in polymer- and paper-based microfluidic devices for point-of-care testing (POCT). In addition, this article highlights how to utilize plasmonic nanoparticles for in vitro and in vivo bio-imaging based on SERS, fluorescence, photoacoustic and dark-field models. Finally, this article shows perspectives in plasmon-enhanced photothermal and photodynamic therapy.

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.

Recent Progress on Tumor Microenvironment-Activated NIR-II Phototheranostic Agents with Simultaneous Activation for Diagnosis and Treatment

Malignant tumors seriously threaten human life and well-being. Emerging Near-infrared II (NIR-II, 1000-1700 nm) phototheranostic nanotechnology integrates diagnostic and treatment modalities, offering merits including improved tissue penetration and enhanced spatiotemporal resolution. This remarkable progress has opened promising avenues for advancing tumor theranostic research. The tumor microenvironment (TME) differs from normal tissues, exhibiting distinct attributes such as hypoxia, acidosis, overexpressed hydrogen peroxide, excess glutathione, and other factors. Capitalizing on these attributes, researchers have developed TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic attributes concurrently. Therefore, developing TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic activation holds significant research importance. Currently, research on TME-activatable NIR-II phototheranostic agents is still in its preliminary stages. This review examines the recent advances in developing dual-functional NIR-II activatable phototheranostic agents over the past years. It systematically presents NIR-II phototheranostic agents activated by various TME factors such as acidity (pH), hydrogen peroxide (H2 O2 ), glutathione (GSH), hydrogen sulfide (H2 S), enzymes, and their hybrid. This encompasses NIR-II fluorescence and photoacoustic imaging diagnostics, along with therapeutic modalities, including photothermal, photodynamic, chemodynamic, and gas therapies triggered by these TME factors. Lastly, the difficulties and opportunities confronting NIR-II activatable phototheranostic agents in the simultaneous diagnosis and treatment field are highlighted.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Mitochondrial Disruption Nanosystem Simultaneously Depressed Programmed Death Ligand-1 and Transforming Growth Factor-β to Overcome Photodynamic Immunotherapy Resistance

Currently, limited photosensitizers possess the capacity to reverse tumor hypoxia and reduce programmed death ligand-1 (PD-L1) and transforming growth factor-β (TGF-β) expression simultaneously, hindering the perfect photodynamic therapy (PDT) effect due to acquired immune resistance and the tumor hypoxic microenvironment. To tackle these challenges, in this research, we demonstrated that mitochondrial energy metabolism depression can be utilized as an innovative and efficient approach for reducing the expression of PD-L1 and TGF-β simultaneously, which may offer a design strategy for a more ideal PDT nanosystem. Through proteomic analysis of 5637 cells, we revealed that tamoxifen (TMX) can incredibly regulate PD-L1 expression in tumor cells. Then, to selectively deliver clinically used mitochondrial energy metabolism depressant TMX to solid tumors as well as design an ideal PDT nanosystem, we synthesized MHI-TMX@ALB by combining a mitochondria-targeted heptamethine cyanine PDT-dye MHI with TMX through self-assembly with albumin (ALB). Interestingly enough, the MHI-TMX@ALB nanoparticle demonstrated effective reversion of tumor hypoxia and inhibition of PD-L1 protein expression at a lower dosage (7.5 times to TMX), which then enhanced the efficacy of photodynamic immunotherapy via enhancing T-cell infiltration. Apart from this, by leveraging the heptamethine dye's targeting capacity toward tumors and TMX's role in suppressing TGF-β, MHI-TMX@ALB also more effectively mitigated 4T1 tumor lung metastasis development. All in all, the MHI-TMX@ALB nanoparticle could be used as a multifunctional economical PD-L1 and TGF-β codepression immune-regulating strategy, broadening the potential clinical applications for a more ideal PDT nanosystem.

Near-Infrared-II-Activatable Self-Assembled Manganese Porphyrin-Gold Heterostructures for Photoacoustic Imaging-Guided Sonodynamic-Augmented Photothermal/Photodynamic Therapy

Porphyrins and their derivatives are widely used as photosensitizers and sonosensitizers in tumor treatment. Nevertheless, their poor water solubility and low chemical stability reduce their singlet oxygen (1O2) yield and, consequently, their photodynamic therapy (PDT) and sonodynamic therapy (SDT) efficiency. Although strategies for porphyrin molecule assembly have been developed to augment 1O2 generation, there is scope for further improving PDT and SDT efficiencies. Herein, we synthesized ordered manganese porphyrin (SM) nanoparticles with well-defined self-assembled metalloporphyrin networks that enabled efficient energy transfer for enhanced photocatalytic and sonocatalytic activity in 1O2 production. Subsequently, Au nanoparticles were grown in situ on the SM surface by anchoring the terminal alkynyl of porphyrin to form plasmonic SMA heterostructures, which showed the excellent near-infrared-II (NIR-II) region absorption and photothermal properties, and facilitated electron-hole pair separation and transfer. With the modification of hyaluronic acid (HA), SMAH heterostructure nanocomposites exhibited good water solubility and were actively targeted to cancer cells. Under NIR-II light and ultrasound (US) irradiation, the SMAH generates hyperthermia, and a large amount of 1O2, inducing cancer cell damage. Both in vitro and in vivo studies confirmed that the SMAH nanocomposites effectively suppressed tumor growth by decreasing GSH levels in SDT-augmented PDT/PTT. Moreover, by utilizing the strong absorption in the NIR-II window, SMAH nanocomposites can achieve NIR-II photoacoustic imaging-guided combined cancer treatment. This work provides a paradigm for enhancing the 1O2 yield of metalloporphyrins to improve the synergistic therapeutic effect of SDT/PDT/PTT.

Reactive Oxygen Species Scavenging Nanozymes: Emerging Therapeutics for Acute Liver Injury Alleviation

Acute liver injury (AIL), a fatal clinical disease featured with a swift deterioration of hepatocyte functions in the short term, has emerged as a serious public health issues that warrants attention. However, the effectiveness of existing small molecular antioxidants and anti-inflammatory medications in alleviating AIL remains uncertain. The unique inherent structural characteristics of liver confer it a natural propensity for nanoparticle capture, which present an opportunity to exploit in the formulation of nanoscale therapeutic agents, enabling their selective accumulation in the liver and thereby facilitating targeted therapeutic interventions. Significantly increased reactive oxygen species (ROS) accumulation and inflammation response have been evidenced to play crucial roles in occurrence and development of AIL. Nanozymes with ROS-scavenging capacities have demonstrated considerable promise in ROS elimination and inflammation regulation, thereby offering an appealing therapeutic instrument for the management of acute liver injury. In this review, the mechanisms of different type of ALI were summarized. In addition, we provide a comprehensive summary and review of the available ROS-scavenging nanozymes, including transition metal-based nanozymes, noble metal nanozymes, carbon-based nanozymes, and some other nanozymes. Furthermore, the challenges still need to be solved in the field of ROS-scavenging nanozymes for ALI alleviation are also discussed.

Tunable Interparticle Connectivity in Gold Nanosphere Assemblies for Efficient Photoacoustic Conversion

Manipulating matter at the nanometer scale to create desired plasmonic nanostructures holds great promise in the field of biomedical photoacoustic (PA) imaging. We demonstrate a strategy for regulating PA signal generation from anisotropic nano-sized assemblies of gold nanospheres (Au NSs) by adjusting the inter-particle connectivity between neighboring Au NSs. The inter-particle connectivity is controlled by modulating the diameter and inter-particle spacing of Au NSs in the nanoassemblies. The results indicate that nanoassemblies with semi-connectivity, i.e., assemblies with a finite inter-particle spacing shorter than the theoretical limit of repulsion between nearby Au NSs, exhibit 3.4-fold and 2.4-fold higher PA signals compared to nanoassemblies with no connectivity and full connectivity, respectively. Furthermore, due to the reduced diffusion of Au atoms, the semi-connectivity Au nanoassemblies demonstrate high photodamage threshold and, therefore, excellent photostability at fluences above the current American National Standards Institute limits. The exceptional photostability of the semi-connectivity nanoassemblies highlights their potential to surpass conventional plasmonic contrast agents for continuing PA imaging. Collectively, our findings indicate that semi-connected nanostructures are a promising option for reliable, high-contrast PA imaging applications over multiple imaging sessions due to their strong PA signals and enhanced photostability.

Small-Molecule Phototheranostic Agent with Extended π-Conjugation for Efficient NIR-II Photoacoustic-Imaging-Guided Photothermal Therapy

Photoacoustic imaging (PAI) and photothermal therapy (PTT) conducted over the near-infrared-II (NIR-II) window offer the benefits of noninvasiveness and deep tissue penetration. This necessitates the development of highly effective therapeutic agents with NIR-II photoresponsivity. Currently, the predominant organic diagnostic agents used in NIR-II PAI-guided PTT are conjugated polymeric materials. However, they exhibit a low in vivo clearance rate and long-term biotoxicity, limiting their clinical translation. In this study, an organic small molecule (CY-1234) with NIR-II absorption and nanoencapsulation (CY-1234 nanoparticles (NPs)) for PAI-guided PTT is reported. Extended π-conjugation is achieved in the molecule by introducing donor-acceptor units at both ends of the molecule. Consequently, CY-1234 exhibits a maximum absorption peak at 1234 nm in tetrahydrofuran. Nanoaggregates of CY-1234 are synthesized via F-127 encapsulation. They exhibit an excellent photothermal conversion efficiency of 76.01% upon NIR-II light irradiation. After intravenous injection of CY-1234 NPs into tumor-bearing mice, strong PA signals and excellent tumor ablation are observed under 1064 nm laser irradiation. This preliminary study can pave the way for the development of small-molecule organic nanoformulations for future clinical applications.

Assembly and Healing: Capacitive and Conductive Plasmonic Interfacing via a Unified and Clean Wet Chemistry Route

Solution-based nanoparticle assembly represents a highly promising way to build functional metastructures based on a wealth of synthetic nanomaterial building blocks with well-controlled morphology and crystallinity. In particular, the involvement of DNA molecular programming in these bottom-up processes gradually helps the ambitious goal of customizable chemical nanofabrication. However, a fundamental challenge is to realize strong interunit coupling in an assembly toward emerging functions and applications. Herein, we present a unified and clean strategy to address this critical issue based on a H2O2-redox-driven "assembly and healing" process. This facile solution route is able to realize both capacitively coupled and conductively bridged colloidal boundaries, simply switchable by the reaction temperature, toward bottom-up nanoplasmonic engineering. In particular, such a "green" process does not cause surface contamination of nanoparticles by exogenous active metal ions or strongly passivating ligands, which, if it occurs, could obscure the intrinsic properties of as-formed structures. Accordingly, previously raised questions regarding the activities of strongly coupled plasmonic structures are clarified. The reported process is adaptable to DNA nanotechnology, offering molecular programmability of interparticle charge conductance. This work represents a new generation of methods to make strongly coupled nanoassemblies, offering great opportunities for functional colloidal technology and even metal self-healing.

Multifunctional Nanoplatform for NIR-II Imaging-Guided Synergistic Oncotherapy

Tumors are a major public health issue of concern to humans, seriously threatening the safety of people's lives and property. With the increasing demand for early and accurate diagnosis and efficient treatment of tumors, noninvasive optical imaging (including fluorescence imaging and photoacoustic imaging) and tumor synergistic therapies (phototherapy synergistic with chemotherapy, phototherapy synergistic with immunotherapy, etc.) have received increasing attention. In particular, light in the near-infrared second region (NIR-II) has triggered great research interest due to its penetration depth, minimal tissue autofluorescence, and reduced tissue absorption and scattering. Nanomaterials with many advantages, such as high brightness, great photostability, tunable photophysical properties, and excellent biosafety offer unlimited possibilities and are being investigated for NIR-II tumor imaging-guided synergistic oncotherapy. In recent years, many researchers have tried various approaches to investigate nanomaterials, including gold nanomaterials, two-dimensional materials, metal sulfide oxides, polymers, carbon nanomaterials, NIR-II dyes, and other nanomaterials for tumor diagnostic and therapeutic integrated nanoplatform construction. In this paper, the application of multifunctional nanomaterials in tumor NIR-II imaging and collaborative therapy in the past three years is briefly reviewed, and the current research status is summarized and prospected, with a view to contributing to future tumor therapy.

A Stable Open-Shell Conjugated Diradical Polymer with Ultra-High Photothermal Conversion Efficiency for NIR-II Photo-Immunotherapy of Metastatic Tumor

Massive efforts have been concentrated on the advance of eminent near-infrared (NIR) photothermal materials (PTMs) in the NIR-II window (1000-1700 nm), especially organic PTMs because of their intrinsic biological safety compared with inorganic PTMs. However, so far, only a few NIR-II-responsive organic PTMs was explored, and their photothermal conversion efficiencies (PCEs) still remain relatively low. Herein, donor-acceptor conjugated diradical polymers with open-shell characteristics are explored for synergistically photothermal immunotherapy of metastatic tumors in the NIR-II window. By employing side-chain regulation, the conjugated diradical polymer TTB-2 with obvious NIR-II absorption was developed, and its nanoparticles realize a record-breaking PCE of 87.7% upon NIR-II light illustration. In vitro and in vivo experiments demonstrate that TTB-2 nanoparticles show good tumor photoablation with navigation of photoacoustic imaging in the NIR-II window, without any side-effect. Moreover, by combining with PD-1 antibody, the pulmonary metastasis of breast cancer is high-effectively prevented by the efficient photo-immunity effect. Thus, this study explores superior PTMs for cancer metastasis theranostics in the NIR-II window, offering a new horizon in developing radical-characteristic NIR-II photothermal materials.

Tumor microenvironment-mediated NIR-I-to-NIR-II transformation of Au self-assembly for theranostics

The misdiagnosis of tumors due to insufficient penetration depth or signal interference and damage to normal tissues due to indiscriminate treatment are the biggest challenges in using photothermal agents for clinical translation. To overcome these limitations, a strategy of switching from the near-infrared (NIR)-I region to the NIR-II region was developed based on tumor microenvironment (TME)-mediated gold (Au) self-assembly. Using zeolitic imidazolate framework-8 (ZIF-8) metal-organic framework-coated gold nanorods (AuNRs@ZIF-8) as a model photothermal agent, we demonstrated that only a NIR-I photoacoustic imaging signal was observed in normal tissue because ZIF-8 could prevent the aggregation of AuNRs. However, when ZIF-8 dissociated in the TME, the AuNRs aggregated to activate NIR-II photoacoustic imaging and attenuate the NIR-I signal, thereby allowing an accurate diagnosis of tumors based on signal transformation. Notably, TME-activated NIR-II photothermal therapy could also inhibit tumor growth. Therefore, this TME-activated NIR-I-to-NIR-II switching strategy could improve the accuracy of deep-tumor diagnoses and avoid the injury caused by undifferentiated treatment. STATEMENT OF SIGNIFICANCE: Photothermal agents used for photoacoustic imaging and photothermal therapy have garnered great attention for tumor theranostics. However, always "turned on" near-infrared (NIR)-I laser (700-1000 nm)-responsive photothermal agents face issues of penetration depth and damage to normal tissues. In contrast, tumor microenvironment-activated NIR-II "smart" photothermal agents exhibit deeper penetration depth and tumor selectivity. Therefore, a NIR-I-to-NIR-II switching strategy was developed based on tumor microenvironment-mediated Au self-assembly. This work provides a new strategy for developing tumor microenvironment-activated NIR-II smart photothermal agents.

Hot-Electron Dynamics Mediated Medical Diagnosis and Therapy

Surface plasmon resonance excitation significantly enhances the absorption of light and increases the generation of "hot" electrons, i.e., conducting electrons that are raised from their steady states to excited states. These excited electrons rapidly decay and equilibrate via radiative and nonradiative damping over several hundred femtoseconds. During the hot-electron dynamics, from their generation to the ultimate nonradiative decay, the electromagnetic field enhancement, hot electron density increase, and local heating effect are sequentially induced. Over the past decade, these physical phenomena have attracted considerable attention in the biomedical field, e.g., the rapid and accurate identification of biomolecules, precise synthesis and release of drugs, and elimination of tumors. This review highlights the recent developments in the application of hot-electron dynamics in medical diagnosis and therapy, particularly fully integrated device techniques with good application prospects. In addition, we discuss the latest experimental and theoretical studies of underlying mechanisms. From a practical standpoint, the pioneering modeling analyses and quantitative measurements in the extreme near field are summarized to illustrate the quantification of hot-electron dynamics. Finally, the prospects and remaining challenges associated with biomedical engineering based on hot-electron dynamics are presented.

Palladium Nanocapsules for Photothermal Therapy in the Near-Infrared II Biological Window

Recent developments in nanomaterials with programmable optical responses and their capacity to modulate the photothermal effect induced by an extrinsic source of light have elevated plasmonic photothermal therapy (PPTT) to the status of a favored treatment for a variety of malignancies. However, the low penetration depth of near-infrared-I (NIR-I) lights and the need to expose the human body to a high laser power density in PPTT have restricted its clinical translation for cancer therapy. Most nanostructures reported to date exhibit limited performance due to (i) activity only in the NIR-I region, (ii) the use of intense laser, (iii) need of large concentration of nanomaterials, or (iv) prolonged exposure times to achieve the optimal hyperthermia state for cancer phototherapy. To overcome these shortcomings in plasmonic nanomaterials, we report a bimetallic palladium nanocapsule (Pd Ncap)─with a solid gold bead as its core and a thin, perforated palladium shell─with extinction both in the NIR-I as well as the NIR-II region for PPTT applications toward cancer therapy. The Pd Ncap demonstrated exceptional photothermal stability with a photothermal conversion efficiency of ∼49% at the NIR-II (1064 nm) wavelength region at a very low laser power density of 0.5 W/cm2. The nanocapsules were further surface-functionalized with Herceptin (Pd Ncap-Her) to target the breast cancer cell line SK-BR-3 and exploited for in vitro PPTT applications using NIR-II light. Pd Ncap-Her caused more than 98% cell death at a concentration of just 50 μg/mL and a laser power density of 0.5 W/cm2 with an output power of only 100 mW. Flow cytometric and microscopic analyses revealed that Pd Ncap-Her-induced apoptosis in the treated cancer cells during PPTT. Additionally, Pd Ncaps were found to have reactive oxygen species (ROS) scavenging ability, which can potentially reduce the damage to cells or tissues from ROS produced during PPTT. Also, Pd Ncap demonstrated excellent in vivo biocompatibility and was highly efficient in photothermally ablating tumors in mice. With a high photothermal conversion and killing efficiency at very low nanoparticle concentrations and laser power densities, the current nanostructure can operate as an effective phototherapeutic agent for the treatment of different cancers with ROS-protecting ability.

Nanoparticle-Based Photothermal Therapy for Breast Cancer Noninvasive Treatment

Rapid advancements in materials science and nanotechnology, intertwined with oncology, have positioned photothermal therapy (PTT) as a promising noninvasive treatment strategy for cancer. The breast's superficial anatomical location and aesthetic significance render breast cancer a particularly pertinent candidate for the clinical application of PTT following melanoma. This review comprehensively explores the research conducted on the various types of nanoparticles employed in PTT for breast cancer and elaborates on their specific roles and mechanisms of action. The integration of PTT with existing clinical therapies for breast cancer is scrutinized, underscoring its potential for synergistic outcomes. Additionally, the mechanisms underlying PTT and consequential modifications to the tumor microenvironment after treatment are elaborated from a medical perspective. Future research directions are suggested, with an emphasis on the development of integrative platforms that combine multiple therapeutic approaches and the optimization of nanoparticle synthesis for enhanced treatment efficacy. The goal is to push the boundaries of PTT toward a comprehensive, clinically applicable treatment for breast cancer.

Optical and Photoacoustic Imaging In Vivo: Opportunities and Challenges

Optical and photoacoustic imaging plays an important role in biomedical applications owing to its noninvasiveness and high resolution. Fluorescence imaging and photoacoustic imaging emerge as powerful tools to deconstruct molecular information and investigate biological processes in vivo. Despite great progress has been achieved in chemical probe synthesis, how to design probes with optimal fluorescence or photoacoustic imaging performance to dynamically visualize the biological process in vivo still faces challenges. From this perspective, we will focus on the advanced development of fluorescence and photoacoustic imaging in vivo. Furthermore, concerns and prospects for future imaging in vivo will be demonstrated.

Nanomaterials for photothermal cancer therapy

Cancer has emerged as a pressing global public health issue, and improving the effectiveness of cancer treatment remains one of the foremost challenges of modern medicine. The primary clinical methods of treating cancer, including surgery, chemotherapy and radiotherapy, inevitably result in some adverse effects on the body. However, the advent of photothermal therapy offers an alternative route for cancer treatment. Photothermal therapy relies on photothermal agents with photothermal conversion capability to eliminate tumors at high temperatures, which offers advantages of high precision and low toxicity. As nanomaterials increasingly play a pivotal role in tumor prevention and treatment, nanomaterial-based photothermal therapy has gained significant attention owing to its superior photothermal properties and tumor-killing abilities. In this review, we briefly summarize and introduce the applications of common organic photothermal conversion materials (e.g., cyanine-based nanomaterials, porphyrin-based nanomaterials, polymer-based nanomaterials, etc.) and inorganic photothermal conversion materials (e.g., noble metal nanomaterials, carbon-based nanomaterials, etc.) in tumor photothermal therapy in recent years. Finally, the problems of photothermal nanomaterials in antitumour therapy applications are discussed. It is believed that nanomaterial-based photothermal therapy will have good application prospects in tumor treatment in the future.

Self-Propelled Ultrasmall AuNPs-Tannic Acid Hybrid Nanozyme with ROS-Scavenging and Anti-Inflammatory Activity for Drug-Induced Liver Injury Alleviation

Developing nanomedicines with superior reactive oxygen species (ROS) scavenging capability has emerged as a promising strategy in treating ROS-related diseases, for example, drug-induced liver injury. However, designing nanoscavengers with the self-propelling ability to scavenge ROS actively remains challenging. Here, a self-propelled silica-supported ultrasmall gold nanoparticles-tannic acid hybrid nanozyme (SAuPTB) is designed that can effectively alleviate acetaminophen (APAP)-induced liver injury by scavenging excessive ROS and regulating inflammation. SAuPTB exhibits multienzyme activity and displays significantly enhanced diffusion under hydrogen peroxide (H₂ O₂ ). This in vitro research shows that SAuPTB can effectively eliminate ROS, increasing the viability of H₂ O₂ -stimulated cells and reducing the cytotoxicity of APAP/H₂ O₂ -treated AML12 cells. The in vivo studies show that SAuPTB can accumulate at inflammatory sites in mouse liver, resulting in the decrease of alanine aminotransferase, aspartate aminotransferase, and ROS, reduction in pro-inflammatory cytokines and chemokines, hence reduced hepatocyte necrosis, liver injury, and mortality. Furthermore, SAuPTB activates the nuclear erythroid 2-related factor 2 pathway to upregulate antioxidative genes and reduce oxidative stress. Finally, the liver shows decreased high mobility group box 1 and F4/80⁺ macrophages, suggesting an anti-inflammatory response. This work provides a novel design strategy of nanozymes for ROS-related disease treatment.

Second Near-Infrared Plasmonic Nanomaterials for Photoacoustic Imaging and Photothermal Therapy

Photoacoustic imaging (PAI) and imaging-guided photothermal therapy (PTT) in the second near-infrared window (NIR-II, 1000-1700 nm) have received increasing attention owing to their advantages of greater penetration depth and higher signal-to-noise ratio. Plasmonic nanomaterials with tunable optical properties and strong light absorption provide an alternative to dye molecules, showing great prospects for phototheranostic applications. In this review, the research progress in principally modulating the optical properties of plasmonic nanomaterials, especially affecting parameters such as size, morphology, and surface chemical modification, is introduced. The commonly used plasmonic nanomaterials in the NIR-II window, including noble metals, semiconductors, and heterostructures, are then summarized. In addition, the biomedical applications of these NIR-II plasmonic nanomaterials for PAI and PTT in phototheranostics are highlighted. Finally, the perspectives and challenges for advancing plasmonic nanomaterials for practical use and clinical translation are discussed.

Bioactive inorganic nanomaterials for cancer theranostics

Bioactive materials are a special class of biomaterials that can react in vivo to induce a biological response or regulate biological functions, thus achieving a better curative effect than traditional inert biomaterials. For cancer theranostics, compared with organic or polymer nanomaterials, inorganic nanomaterials possess unique physical and chemical properties, have stronger mechanical stability on the basis of maintaining certain bioactivity, and are easy to be compounded with various carriers (polymer carriers, biological carriers, etc.), so as to achieve specific antitumor efficacy. After entering the nanoscale, due to the nano-size effect, high specific surface area and special nanostructures, inorganic nanomaterials exhibit unique biological effects, which significantly influence the interaction with biological organisms. Therefore, the research and applications of bioactive inorganic nanomaterials in cancer theranostics have attracted wide attention. In this review, we mainly summarize the recent progress of bioactive inorganic nanomaterials in cancer theranostics, and also introduce the definition, synthesis and modification strategies of bioactive inorganic nanomaterials. Thereafter, the applications of bioactive inorganic nanomaterials in tumor imaging and antitumor therapy, including tumor microenvironment (TME) regulation, catalytic therapy, gas therapy, regulatory cell death and immunotherapy, are discussed. Finally, the biosafety and challenges of bioactive inorganic nanomaterials are also mentioned, and their future development opportunities are prospected. This review highlights the bioapplication of bioactive inorganic nanomaterials.

Selenide Heterostructure Nanosheets with Efficient Near-Infrared Photothermal Conversion for Therapy

Photothermal therapy has been regarded as one of promising ways for tumor treatment. However, nanoagents with highly efficient thermal conversion and good bio-compatibility are still needed to be developed in biomedicine. In this work, we prepared two-dimensional heterostructures with bismuth selenide and tungsten selenide nanosheets as photothermal nanoagents. Near-infrared photothermal conversion of selenide heterostructure nanosheets can reach up to 40.75% under 808 nm excitation. It is known that selenium is a critical element to human health. More importantly, our experiments with mice show that the heterostructure nanosheets have low toxicity and high biocompatibility both in vitro and in vivo. The nanoagents based on heterostructures can effectively realize photothermal tumor ablation. It is suggested that the developed selenide nanosheets have great potential application in cancer therapy.

Fluorescence, ultrasonic and photoacoustic imaging for analysis and diagnosis of diseases

Biomedical imaging technology, which allows us to peer deeply within living subjects and visually explore the delivery and distribution of agents in living things, is producing tremendous opportunities for the early diagnosis and precise therapy of diseases. In this feature article, based on reviewing the latest representative examples of progress together with our recent efforts in the bioimaging field, we intend to introduce three typical kinds of non-invasive imaging technologies, i.e., fluorescence, ultrasonic and photoacoustic imaging, in which optical and/or acoustic signals are employed for analyzing various diseases. In particular, fluorescence imaging possesses a series of outstanding advantages, such as high temporal resolution, as well as rapid and sensitive feedback. Hence, in the first section, we will introduce the latest studies on developing novel fluorescence imaging methods for imaging bacterial infections, cancer and lymph node metastasis in a long-term and real-time manner. However, the issues of imaging penetration depth induced by photon scattering and light attenuation of biological tissue limit their widespread in vivo imaging applications. Taking advantage of the excellect penetration depth of acoustic signals, ultrasonic imaging has been widely applied for determining the location, size and shape of organs, identifying normal and abnormal tissues, as well as confirming the edges of lesions in hospitals. Thus, in the second section, we will briefly summarize recent advances in ultrasonic imaging techniques for diagnosing diseases in deep tissues. Nevertheless, the absence of lesion targeting and dependency on a professional technician may lead to the possibility of false-positive diagnosis. By combining the merits of both optical and acoustic signals, newly-developed photoacoustic imaging, simultaneously featuring higher temporal and spatial resolution with good sensitivity, as well as deeper penetration depth, is discussed in the third secretion. In the final part, we further discuss the major challenges and prospects for developing imaging technology for accurate disease diagnosis. We believe that these non-invasive imaging technologies will introduce a new perspective for the precise diagnosis of various diseases in the future.

Highly Responsive Plasmon Modulation in Dopant-Segregated Nanocrystals

Electron transfer to and from metal oxide nanocrystals (NCs) modulates their infrared localized surface plasmon resonance (LSPR), revealing fundamental aspects of their photophysics and enabling dynamic optical applications. We synthesized and chemically reduced dopant-segregated Sn-doped In₂O₃ NCs, investigating the influence of radial dopant segregation on LSPR modulation and near-field enhancement (NFE). We found that core-doped NCs show large LSPR shifts and NFE change during chemical titration, enabling broadband modulation in LSPR energy of over 1000 cm^-1 and of peak extinction over 300%. Simulations reveal that the evolution of the LSPR spectra during chemical reduction results from raising the surface Fermi level and increasing the donor defect density in the shell region. These results establish dopant segregation as a useful strategy to engineer the dynamic optical modulation in plasmonic semiconductor NC heterostructures going beyond what is possible with conventional plasmonic metals.

Smart Biomimetic Nanozymes for Precise Molecular Imaging: Application and Challenges

New nanotechnologies for imaging molecules are widely being applied to visualize the expression of specific molecules (e.g., ions, biomarkers) for disease diagnosis. Among various nanoplatforms, nanozymes, which exhibit enzyme-like catalytic activities in vivo, have gained tremendously increasing attention in molecular imaging due to their unique properties such as diverse enzyme-mimicking activities, excellent biocompatibility, ease of surface tenability, and low cost. In addition, by integrating different nanoparticles with superparamagnetic, photoacoustic, fluorescence, and photothermal properties, the nanoenzymes are able to increase the imaging sensitivity and accuracy for better understanding the complexity and the biological process of disease. Moreover, these functions encourage the utilization of nanozymes as therapeutic agents to assist in treatment. In this review, we focus on the applications of nanozymes in molecular imaging and discuss the use of peroxidase (POD), oxidase (OXD), catalase (CAT), and superoxide dismutase (SOD) with different imaging modalities. Further, the applications of nanozymes for cancer treatment, bacterial infection, and inflammation image-guided therapy are discussed. Overall, this review aims to provide a complete reference for research in the interdisciplinary fields of nanotechnology and molecular imaging to promote the advancement and clinical translation of novel biomimetic nanozymes.

Photomagnetically Powered Spiky Nanomachines with Thermal Control of Viscosity for Enhanced Cancer Mechanotherapy

Nanomachines with active propulsion have emerged as an intelligent platform for targeted cancer therapy. Achieving an efficient locomotion performance using an external energy conversion is a key requirement in the design of nanomachines. In this study, inspired by diverse spiky structures in nature, a photomagnetically powered nanomachine (PMN) with a spiky surface and thermally dependent viscosity tunability is proposed to facilitate mechanical motion in lysosomes for cancer mechanotherapy. The hybrid nanomachine is integrated with magnetic nanoparticles as the core and covered with gold nanotips. Physical simulations and experimental results prove that the spiky structure endows nanomachines with an obvious photomagnetic coupling effect in the NIR-II region through the alignment and orienting movement of plasmons on the gold tips. Using a coupling-enhanced magnetic field, PMNs are efficiently assembled into chain-like structures to further elevate energy conversion efficiency. Notably, PMNs with the thermal control of viscosity are efficiently propelled under simultaneously applied dual external energy sources in cell lysosomes. Enhanced mechanical destruction of cancer cells via PMNs is confirmed both in vitro and in vivo under photomagnetic treatment. This study provides a new direction for designing integrated nanomachines with active adaptability to physiological environments for cancer treatment.

PDGFB-targeted functional MRI nanoswitch for activatable T1-T2 dual-modal ultra-sensitive diagnosis of cancer

As one of the most significant imaging modalities currently available, magnetic resonance imaging (MRI) has been extensively utilized for clinically accurate cancer diagnosis. However, low signal-to-noise ratio (SNR) and low specificity for tumors continue to pose significant challenges. Inspired by the distance-dependent magnetic resonance tuning (MRET) phenomenon, the tumor microenvironment (TME)-activated off-on T₁-T₂ dual-mode MRI nanoswitch is presented in the current study to realize the sensitive early diagnosis of tumors. The tumor-specific nanoswitch is designed and manufactured on the basis of PDGFB-conjugating ferroferric oxide coated by Mn-doped silica (PDGFB-FMS), which can be degraded under the high-concentration GSH and low pH in TME to activate the T₁-T₂ dual-mode MRI signals. The tumor-specific off-on dual-mode MRI nanoswitch can significantly improve the SNR and is used successfully for the accurate diagnosis of early-stage tumors, particularly for orthotopic prostate cancer. In addition, the systemic delivery of the nanoswitch did not cause blood or tissue damage, and it can be excreted out of the body in a timely manner, demonstrating excellent biosafety. Overall, the strategy is a significant step in the direction of designing off-on dual-mode MRI nanoprobes to improve imaging accuracy, which opens up new avenues for the development of new MRI probes.

Photoresponsive Inorganic Nanomaterials in Oncology

The diagnosis and treatment of cancer are continuously evolving in search of more efficient, safe, and personalized approaches. Therapies based on nanoparticles or physical stimuli-responsive substances have shown great potential to overcome the inherent shortcomings of conventional cancer therapies. In fact, nanoparticles may increase the half-life of chemotherapeutic agents or promote the targeting in cancer tissues while physical stimuli-responsive substances are more effective and safer with respect to traditional chemotherapeutic agents because of the possibility to be switched on only when needed. These 2 approaches can be combined by exploiting the ability of some inorganic nanomaterials to be activated by light, ultrasounds, magnetic fields, or ionizing radiations. Albeit the development of stimuli-responsive materials is still at the early stages, research in this field is rapidly growing since they have important advantages with respect to organic nanoparticles or molecular substances, like higher stability, and higher efficiency in converting the stimulus in heat or, in some cases, reactive oxygen species. On the other hand, the translation process is slowed down by issues related to safety and quality of the formulations. This literature review summarizes the current advancements in this research field, analysing the most promising materials and applications.

Acoustic-Based Theranostic Probes Activated by Tumor Microenvironment for Accurate Tumor Diagnosis and Assisted Tumor Therapy

Acoustic-based imaging techniques, including ultrasonography and photoacoustic imaging, are powerful noninvasive approaches for tumor imaging owing to sound transmission facilitation, deep tissue penetration, and high spatiotemporal resolution. Usually, imaging modes were classified into "always-on" mode and "activatable" mode. Conventional "always-on" acoustic-based probes often have difficulty distinguishing lesion regions of interest from surrounding healthy tissues due to poor target-to-background signal ratios. As compared, activatable probes have attracted attention with improved sensitivity, which can boost or amplify imaging signals only in response to specific biomolecular recognition or interactions. The tumor microenvironment (TME) exhibits abnormal physiological conditions that can be used to identify tumor sections from normal tissues. Various types of organic dyes and biomaterials can react with TME, leading to obvious changes in their optical properties. The TME also affects the self-assembly or aggregation state of nanoparticles, which can be used to design activatable imaging probes. Moreover, acoustic-based imaging probes and therapeutic agents can be coencapsulated into one nanocarrier to develop nanotheranostic probes, achieving tumor imaging and cooperative therapy. Satisfactorily, ultrasound waves not only accelerate the release of encapsulated therapeutic agents but also activate therapeutic agents to exert or enhance their therapeutic performance. Meanwhile, various photoacoustic probes can convert photon energy into heat under irradiation, achieving photoacoustic imaging and cooperative photothermal therapy. In this review, we focus on the recently developed TME-triggered ultrasound and photoacoustic theranostic probes for precise tumor imaging and targeted tumor therapy.

Biomedical Photoacoustic Imaging for Molecular Detection and Disease Diagnosis: "Always-On" and "Turn-On" Probes

Photoacoustic (PA) imaging is a nonionizing, noninvasive imaging technique that combines optical and ultrasonic imaging modalities to provide images with excellent contrast, spatial resolution, and penetration depth. Exogenous PA contrast agents are created to increase the sensitivity and specificity of PA imaging and to offer diagnostic information for illnesses. The existing PA contrast agents are categorized into two groups in this review: "always-on" and "turn-on," based on their ability to be triggered by target molecules. The present state of these probes, their merits and limitations, and their future development, is explored.

Vacancy defect-promoted nanomaterials for efficient phototherapy and phototherapy-based multimodal Synergistic Therapy

Phototherapy and multimodal synergistic phototherapy (including synergistic photothermal and photodynamic therapy as well as combined phototherapy and other therapies) are promising to achieve accurate diagnosis and efficient treatment for tumor, providing a novel opportunity to overcome cancer. Notably, various nanomaterials have made significant contributions to phototherapy through both improving therapeutic efficiency and reducing side effects. The most key factor affecting the performance of phototherapeutic nanomaterials is their microstructure which in principle determines their physicochemical properties and the resulting phototherapeutic efficiency. Vacancy defects ubiquitously existing in phototherapeutic nanomaterials have a great influence on their microstructure, and constructing and regulating vacancy defect in phototherapeutic nanomaterials is an essential and effective strategy for modulating their microstructure and improving their phototherapeutic efficacy. Thus, this inspires growing research interest in vacancy engineering strategies and vacancy-engineered nanomaterials for phototherapy. In this review, we summarize the understanding, construction, and application of vacancy defects in phototherapeutic nanomaterials. Starting from the perspective of defect chemistry and engineering, we also review the types, structural features, and properties of vacancy defects in phototherapeutic nanomaterials. Finally, we focus on the representative vacancy defective nanomaterials recently developed through vacancy engineering for phototherapy, and discuss the significant influence and role of vacancy defects on phototherapy and multimodal synergistic phototherapy. Therefore, we sincerely hope that this review can provide a profound understanding and inspiration for the design of advanced phototherapeutic nanomaterials, and significantly promote the development of the efficient therapies against tumor.

Multifunctional Gold Helix Phototheranostic Biohybrid That Enables Targeted Image-Guided Photothermal Therapy in Breast Cancer

The preparation of multifunctional smart theranostic systems is commonly achieved through complicated strategies, limiting their biomedical applications. Spirulina platensis (SP) microalgae, as a natural helix with some of the intrinsic theranostic functionalities (e.g., fluorescent and photosensitizer pigments), not only facilitates the fabrication process but also guarantees their biosafety for clinical applications. Herein, the helical architecture of gold nanoparticles (AuNPs) based on a SP biotemplate was engineered as a safe, biodegradable, and tumor-targeted biohybrid for imaging-guided photothermal therapy (PTT) to combat triple-negative breast cancer. The quasi-spherical AuNPs were embedded throughout the SP cell (Au-SP) with minimally involved reagents, only by controlling the original morphological stability of SP through pH adjustment of the synthesis media. SP thiolation increased the localization of AuNPs selectively on the cell wall without using a reducing agent (Au-TSP). SP autofluorescence, along with the high X-ray absorption of AuNPs, was employed for dual-modal fluorescence and computed tomography (FL/CT) imaging. Furthermore, the theranostic efficacy of Au-SP was improved through a targeting process with folic acid (Au-SP@CF). High tumor inhibition effects were obtained by the excellent photothermal performance of Au-SP@CF in both in vitro and in vivo analyses. Of particular note, a comparison of the photothermal effect of Au-SP@CF with the naked SP and calcined form of Au-SP@CF not only indicated the key role of the helical architecture of AuNPs in achieving a high photothermal effect but also led to the formation of new gold microspiral biohybrids (Au-MS) over the calcination process. In short, well-controllable immobilization of AuNPs, appropriate biodegradability, good hemocompatibility, long-term biosafety, accurate imaging, high tumor suppression, and low tumor metastasis effects under laser irradiation are an array of intriguing attributes, making the proposed biohybrid a promising theranostic system for FL/CT-imaging-guided PTT.

Advancements in redox-sensitive micelles as nanotheranostics: A new horizon in cancer management

World Health Organisation (WHO) delineated cancer as one of the foremost reasons for mortality with 10 million deaths in the year 2020. Early diagnosis and effective drug delivery are of utmost importance in cancer management. The entrapment of both bio-imaging dyes and drugs will open novel avenues in the area of tumor theranostics. Elevated levels of reactive oxygen species (ROS) and glutathione (GSH) are the characteristic features of the tumor microenvironment (TME). Researchers have taken advantage of these specific TME features in recent years to develop micelle-based theranostic nanosystems. This review focuses on the advantages of redox-sensitive micelles (RSMs) and supramolecular self-assemblies for tumor theranostics. Key chemical linkers employed for the tumor-specific release of the cargo have been discussed. In vitro characterisation techniques used for the characterization of RSMs have been deliberated. Potential bottlenecks that may present themselves in the bench-to-bedside translation of this technology and the regulatory considerations have been deliberated.

An NIR-II Photothermally Triggered "Oxygen Bomb" for Hypoxic Tumor Programmed Cascade Therapy

Hypoxia, as a characteristic feature of solid tumors, has a close relationship with tumor resistance to photodynamic therapy (PDT) and chemotherapy. Perfluorocarbon (PFC) is reported to relieve hypoxic in solid tumors by acting as an oxygen carrier via several nanostructures. However, the oxygen delivery process is mostly driven by a concentration gradient, which is uncontrollable. Herein, a photothermally controlled "oxygen bomb" PSPP-Au₉₈₀ -D is designed by encapsulating a PFC core within a functionalized bilayer polymer shell. Near-infrared second window photothermal agent gold nanorods with excellent photo-to-heat energy-conversion ability are fabricated on the surface of the polymer shell via an innovative modified two-step seedless ex situ growth process to thermally trigger O₂  release. Then, a programmed cascade therapy strategy is customized for hypoxic orthotopic pancreatic cancer. First, PSPP-Au₉₈₀ -D is irradiated by a 980 nm laser to photothermally trigger O₂  infusing into the hypoxic tumor microenvironment, which is accompanied by local hyperemia and doxorubicin release. Subsequently, a 680 nm laser is used to generate singlet oxygen in the oxygenated tumor microenvironment for PDT. This choreographed programmed cascade therapy strategy will provide a new route for suppressing hypoxic tumor growth under mild conditions based on controllable and effective oxygen release.

A "Dual-Source, Dual-Activation" Strategy for an NIR-II Window Theranostic Nanosystem Enabling Optimal Photothermal-Ion Combination Therapy

The activatable imaging technique in the second near-infrared window (NIR-II) utilizes the stimulation of cancer-associated biomarkers for specific imaging to guide precise NIR-II photothermal therapy. However, most activatable nanoprobes with single-source stimulation are insufficient in providing comprehensive information regarding the tumor, severely restricting the therapeutic optimization, especially in NIR-II photothermal therapy (PTT)-based combination therapy. Herein, a "dual-source, dual-activation" strategy-based multifunctional nanosystem, PPAC, is reported as a promising tool for activatable NIR-II fluorescence (FL)/ratiometric photoacoustic (PA) imaging-guided "localization-timing" photothermal-ion therapy (PTIT). A fibroblast activation protein (FAP)-responsive peptide to modify the surface of Pd nanosheets with excellent NIR-II absorption ability can efficiently cross-link BSA-CQ4T to realize NIR-II FL quenching, followed by the loading of Ag to construct the PPAC. Triggered by the specific cleavage with FAP on the perivascular cancer-associated fibroblasts (first source), the PPAC can correspondingly release BSA-CQ4T for rapid fluorescence recovery. The nanosystems are subsequently taken up by tumor cells, where the overexpressed H₂ O₂ (second source) promotes the oxidation of Ag shell to Ag⁺ , and further leads the real-time ratiometric PA signals (Ag-PA660/Pd-PA1050) that can monitor the Ag⁺ ions-related production efficiency and therapeutic performance. Intelligent integration of dual-modality imaging information can comprehensively provide the right time-point and site-specificity for selective NIR-II PTT.

Macromolecular conjugated cyanine fluorophore nanoparticles for tumor-responsive photo nanotheranostics

For photothermal therapy (PTT), the improved targeting can decrease the dosage and promote the therapeutic function of photothermal agents, which would effectively improve the antitumor effect. The tumor microenvironment (TME) and cells are targets in designing intelligent and responsive theranostics. However, most of these schemes have been limited to the traditional visible and first near-infrared (NIR-I) regions, eager to expand to the second near-infrared (NIR-II) window. We designed and synthesized a polyethylene glycol conjugated and disulfide-modified macromolecule fluorophore (MPSS). MPSS could self-assemble into core-shell micelles in an aqueous solution (MPSS-NPS), while the small molecule probes were in a high aggregation arrangement inside the nanoparticle. The pronounced aggregation quenching (ACQ) effect caused them to the "sleeping" state. After entering the tumor cells, the disulfide bonds in MPSS-NPS broke in response to a high concentration of glutathione (GSH) in TME, and the molecule probes were released. The highly aggregated state was effectively alleviated, resulting in distinct absorption enhancement in the near-infrared region. Therefore, the fluorescence signal was recovered, and the photothermal performance was triggered. In vitro and in vivo studies reveal that the Nano-system is efficient for the smart NIR-II fluorescence imaging-guided PTT, even at a low dosage and density of irradiation.