Oxygen Vacancy Enables Markedly Enhanced Magnetic Resonance Imaging-Guided Photothermal Therapy of a Gd3+-Doped Contrast Agent

Structural Defect-Enabled Magnetic Neutrality Nanoprobes for Ultra-High-Field Magnetic Resonance Imaging of Isolated Tumor Cells in Vivo

The identification of metastasis "seeds," isolated tumor cells (ITCs), is of paramount importance for the prognosis and tailored treatment of metastatic diseases. The conventional approach to clinical ITCs diagnosis through invasive biopsies is encumbered by the inherent risks of overdiagnosis and overtreatment. This underscores the pressing need for noninvasive ITCs detection methods that provide histopathological-level insights. Recent advancements in ultra-high-field (UHF) magnetic resonance imaging (MRI) have ignited hope for the revelation of minute lesions, including the elusive ITCs. Nevertheless, currently available MRI contrast agents are susceptible to magnetization-induced strong T2-decaying effects under UHF conditions, which compromises T1 MRI capability and further impedes the precise imaging of small lesions. Herein, this study reports a structural defect-enabled magnetic neutrality nanoprobe (MNN) distinguished by its paramagnetic properties featuring an exceptionally low magnetic susceptibility through atomic modulation, rendering it almost nonmagnetic. This unique characteristic effectively mitigates T2-decaying effect while concurrently enhancing UHF T1 contrast. Under 9 T MRI, the MNN demonstrates an unprecedentedly low r2/r1 value (≈1.06), enabling noninvasive visualization of ITCs with an exceptional detection threshold of ≈0.16 mm. These high-performance MNNs unveil the domain of hitherto undetectable minute lesions, representing a significant advancement in UHF-MRI for diagnostic purposes and fostering comprehensive metastasis research.

Size-Dependent Oxygen Vacancy of Iron Oxide Nanoparticles

Prior research has highlighted the reduction of iron oxide nanoparticle (IONPs) sizes to the "ultra-small" dimension as a pivotal approach in developing T1-MRI contrast agents, and the enhancement in T1 contrast performance with the reducing size is usually attributed to the increased specific surface area and weakened magnetization. Nonetheless, as the size decreases, the variation in surface defects, particularly oxygen vacancy (VO) defects, significantly impacts the T1 imaging efficacy. In this study, the VO on IONPs is meticulously investigated through XPS, Raman, and EPR spectroscopy. As the nanoparticle size decreased, the VO concentration rose initially but subsequently declined, with the peak concentration observed in the size of 8.27 nm. Further insights gained from synchrotron XAS analysis and DFT calculations indicate that both surface tension and phase transition in IONPs contribute to alterations in the Fe─O bond length, thereby influencing the VO formation energy across varying nanoparticle sizes. The MRI tests reveal that the VO in IONPs serve as pivotal sites for the attachment of water molecules to iron ions, and IONPs with fewer VO exhibited a deterioration in T1-MRI contrast effects. This research may provide a deeper understanding of the relationship between T1 contrast performance and the size of IONPs.

Near-Infrared Light-Triggered Thermoresponsive Pyroptosis System for Synergistic Tumor Immunotherapy

Pyroptosis, as an inflammatory cell death, has been widely applied in tumor therapy, but its systemic adverse reactions caused by nonspecific activation still seriously hinder its application. Herein, a near-infrared (NIR) light-triggered thermoresponsive pyroptosis strategy is designed for on-demand initiation of pyroptosis and synergistic tumor immunotherapy. Specifically, glucose oxidase (GOx) loaded and heat-sensitive material p(OEOMA-co-MEMA) (PCM) modified mesoporous Pt nanoparticles (abbreviated as PCM Pt/GOx) are prepared as the mild-temperature triggered pyroptosis inducer. Pt nanoparticles can not only serve as nanozyme with catalase-like activity to promote GOx catalytic reaction, but also act as photothermal agent to achieve mild-temperature photothermal therapy (PTT) and thermoresponsive GOx release on-demand under the irradiation of NIR light, thereby activating and promoting pyroptosis. In vitro and in vivo experiments prove that NIR light-triggered thermoresponsive pyroptosis system exhibits excellent antitumor immunity activity as well as significantly inhibits tumor growth. The precise control of pyroptosis by NIR light as well as pyroptosis cooperated with mild-temperature PTT for synergistically attenuated tumor immunotherapy are reported for the first time. This work provides a new method to initiate pyroptosis on demand, which is of great significance for spatiotemporally controllable pyroptosis and immunotherapy.

Polydopamine Nanostructure-Enhanced Water Interaction with pH-Responsive Manganese Sulfide Nanoclusters for Tumor Magnetic Resonance Contrast Enhancement and Synergistic Ferroptosis-Photothermal Therapy

Rational structure design benefits the development of efficient nanoplatforms for tumor theranostic application. In this work, a multifunctional polydopamine (PDA)-coated manganese sulfide (MnS) nanocluster was prepared. The polyhydroxy structure of PDA enhanced the water interaction with pH-responsive MnS nanoclusters via hydrogen bonds. At pH 5.5 conditions, the spin-lattice relaxation rate of MnS nanoclusters dramatically increased from 5.76 to 19.33 mM-1·s-1 after the PDA coating, which can be beneficial for efficient tumor magnetic resonance imaging. In addition, PDA endowed MnS nanoclusters with excellent biocompatibility and good photothermal conversion efficiency, which can be used for efficient tumor photothermal therapy (PTT). Furthermore, MnS nanoclusters possess the ability to release H2S in the acidic tumor microenvironment, effectively inhibiting mitochondrial respiration and adenosine triphosphate production. As a result, the expression of heat shock protein was obviously reduced, which can reduce the resistance of tumor cells to photothermal stimulation and enhance the efficacy of PTT. The released Mn2+ also displayed efficient peroxidase and glutathione oxidase-like activity, effectively inducing tumor cell ferroptosis and apoptosis at the same time. Therefore, this nanoplatform could be a potential nanotheranostic for magnetic resonance contrast enhancement and synergistic ferroptosis-PTT of tumors.

Ultrasmall Bi/Cu Coordination Polymer Combined with Glucose Oxidase for Tumor Enhanced Chemodynamic Therapy by Starvation and Photothermal Treatment

Multi-modal combination therapy for tumor is expected to have superior therapeutic effect compared with monotherapy. In this study, a super-small bismuth/copper-gallic acid coordination polymer nanoparticle (BCN) protected by polyvinylpyrrolidone is designed, which is co-encapsulated with glucose oxidase (GOX) by phospholipid to obtain nanoprobe BCGN@L. It shows that BCN has an average size of 1.8 ± 0.7 nm, and photothermal conversion of BCGN@L is 31.35% for photothermal imaging and photothermal therapy (PTT). During the treatment process of 4T1 tumor-bearing nude mice, GOX catalyzes glucose in the tumor to generate gluconic acid and hydrogen peroxide (H2 O2 ), which reacts with copper ions (Cu2+ ) to produce toxic hydroxyl radicals (•OH) for chemodynamic therapy (CDT) and new fresh oxygen (O2 ) to supply to GOX for further catalysis, preventing tumor hypoxia. These reactions increase glucose depletion for starvation therapy , decrease heat shock protein expression, and enhance tumor sensitivity to low-temperature PTT. The in vitro and in vivo results demonstrate that the combination of CDT with other treatments produces excellent tumor growth inhibition. Blood biochemistry and histology analysis suggests that the nanoprobe has negligible toxicity. All the positive results reveal that the nanoprobe can be a promising approach for incorporation into multi-modal anticancer therapy.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Defect Engineering in Biomedical Sciences

With the promotion of nanochemistry research, large numbers of nanomaterials have been applied in vivo to produce desirable cytotoxic substances in response to endogenous or exogenous stimuli for achieving disease-specific therapy. However, the performance of nanomaterials is a critical issue that is difficult to improve and optimize under biological conditions. Defect-engineered nanoparticles have become the most researched hot materials in biomedical applications recently due to their excellent physicochemical properties, such as optical properties and redox reaction capabilities. Importantly, the properties of nanomaterials can be easily adjusted by regulating the type and concentration of defects in the nanoparticles without requiring other complex designs. Therefore, this tutorial review focuses on biomedical defect engineering and briefly discusses defect classification, introduction strategies, and characterization techniques. Several representative defective nanomaterials are especially discussed in order to reveal the relationship between defects and properties. A series of disease treatment strategies based on defective engineered nanomaterials are summarized. By summarizing the design and application of defective engineered nanomaterials, a simple but effective methodology is provided for researchers to design and improve the therapeutic effects of nanomaterial-based therapeutic platforms from a materials science perspective.

Construction of Artificial Controllable Aggregation Trojan Horse-Like Nanoplatform for Enhanced NIR-II Photothermal Therapy

Promoting the aggregation of nanoprobes at tumor sites and realizing precise imaging and treatment of tumors is still one of the important problems to be solved in the field of nanomedicine. Poly-2-phenylbenzobisthiazole (PB) is a novel conjugated polymer with good biocompatibility, excellent photothermal properties in the second near-infrared region (NIR-II), but poor water dispersibility. Herein, a novel self-assembly/polymerization two-in-one strategy was proposed to prepare a new family of poly-2-phenyl-benzobisthiazole-based nanoparticles. Because the hydrophobic polymer PB was well "camouflaged" in the hydrophilic polyphenol-metal networks, the prepared "Trojan horse-like" nanoparticle TF-PB exhibited good water dispersibility. Besides, TF-PB can play a role as a contrast agent for photoacoustic and magnetic resonance dual-modality imaging. When deferoxamine was artificially applied and interacted with TF-PB, the polyphenol-metal networks disintegrated and the hydrophobic material PB was exposed and started hydrophobic aggregation. Thus, it can be applied for precise enhanced photothermal therapy (PTT) in the NIR-II. Meanwhile, the aggregation process enabled non-invasive, fast, and accurate real-time monitoring by self-enhancing photoacoustic imaging. This work has realized the artificially controllable aggregation of photothermal materials in the tumor site, solved the limitations of traditional PTT, and also has good application prospects in clinical therapy.

Tungsten-based Nanomaterials in the Biomedical Field: A Bibliometric Analysis of Research Progress and Prospects

Tungsten-based nanomaterials (TNMs) with diverse nanostructures and unique physicochemical properties have been widely applied in the biomedical field. Although various reviews have described the application of TNMs in specific biomedical fields, there are still no comprehensive studies that summarize and analyze research trends of the field as a whole. To identify and further promote the development of biomedical TNMs, a bibliometric analysis method is used to analyze all relevant literature on this topic. First, general bibliometric distributions of the dataset by year, country, institute, referenced source, and research hotspots are recognized. Next, a comprehensive review of the subjectively recognized research hotspots in various biomedical fields, including biological sensing, anticancer treatments, antibacterials, and toxicity evaluation, is provided. Finally, the prospects and challenges of TNMs are discussed to provide a new perspective for further promoting their development in biomedical research.

Rare-Earth-Metal (Nd3+, Ce3+ and Gd3+)-Doped CaF2: Nanoparticles for Multimodal Imaging in Biomedical Applications

Here, we describe the synthesis of a novel type of rare-earth-doped nanoparticles (NPs) for multimodal imaging, by combining the rare-earth elements Ce, Gd and Nd in a crystalline host lattice consisting of CaF2 (CaF2: Ce, Gd, Nd). CaF2: Ce, Gd, Nd NPs are small (15-20 nm), of uniform shape and size distribution, and show good biocompatibility and low immunogenicity in vitro. In addition, CaF2: Ce, Gd, Nd NPs possess excellent optical properties. CaF2: Ce, Gd, Nd NPs produce downconversion emissions in the second near-infrared window (NIR-II, 1000-1700 nm) under 808 nm excitation, with a strong emission peak at 1056 nm. Excitation in the first near- infrared window (NIR-I, 700-900 nm) has the advantage of deeper tissue penetration power and reduced autofluorescence, compared to visible light. Thus, CaF2: Ce, Gd, Nd NPs are ideally suited for in vivo fluorescence imaging. In addition, the presence of Gd3+ makes the NPs intrinsically monitorable by magnetic resonance imaging (MRI). Moreover, next to fluorescence and MR imaging, our results show that CaF2: Ce, Gd, Nd NPs can be used as imaging probes for photoacoustic imaging (PAI) in vitro. Therefore, due to their biocompatibility and suitability as multimodal imaging probes, CaF2: Ce, Gd, Nd NPs exhibit great potential as a traceable imaging agent in biomedical applications.

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.

Molecular imaging nanoprobes for theranostic applications

As a non-invasive imaging monitoring method, molecular imaging can provide the location and expression level of disease signature biomolecules in vivo, leading to early diagnosis of relevant diseases, improved treatment strategies, and accurate assessment of treating efficacy. In recent years, a variety of nanosized imaging probes have been developed and intensively investigated in fundamental/translational research and clinical practice. Meanwhile, as an interdisciplinary discipline, this field combines many subjects of chemistry, medicine, biology, radiology, and material science, etc. The successful molecular imaging not only requires advanced imaging equipment, but also the synthesis of efficient imaging probes. However, limited summary has been reported for recent advances of nanoprobes. In this paper, we summarized the recent progress of three common and main types of nanosized molecular imaging probes, including ultrasound (US) imaging nanoprobes, magnetic resonance imaging (MRI) nanoprobes, and computed tomography (CT) imaging nanoprobes. The applications of molecular imaging nanoprobes were discussed in details. Finally, we provided an outlook on the development of next generation molecular imaging nanoprobes.

Recent advances in biological applications of nanomaterials through defect engineering

In recent years, defect engineering sprung up in the artificial nanomaterials (NMs) has attracted significant attention, since the physical and chemical properties of NMs could be largely optimized based on the rational control of different defect types and densities. Defective NMs equipped with the improved electric and catalytic ability, would be widely utilized as the photoelectric device and catalysts to alleviate the growing demands of industrial production and environmental treatments. In particular, considering that the features of targeting, adsorptive, loading and optical could be adjusted by the introduction of defects, numerous defective NMs are encouraged to be applied in the biological fields including bacterial inactivation, cancer therapy and so on. And this review is devoted to summarize the recent biological applications of NMs with abundant defects. Moreover, the opportunity of these defective NMs released into the surrounding environment continue to increase, the direct and indirect contact with biological molecules and organisms would be inevitable. Due to its high reactivity and adsorption triggered by defects, NMs tend to exhibit overestimate biological behaviors and effects on organisms. Thus, the sections regarding toxicological effects of NMs with abundant defects are also carried out to supplement the safety assessments of NMs and guide further applications in the industrial production and living.

Photoinduced Superhydrophilicity of Gd-Doped TiO2 Ellipsoidal Nanoparticles Boosts T1 Contrast Enhancement for Magnetic Resonance Imaging

The unsatisfactory performance of current gadolinium chelate based T₁ contrast agents (CAs) for magnetic resonance imaging (MRI) stimulates the search for better alternatives. Herein, we report a new strategy to substantially improve the capacity of nanoparticle-based T₁ CAs by exploiting the photoinduced superhydrophilic assistance (PISA) effect. As a proof of concept, we synthesized citrate-coated Gd-doped TiO₂ ellipsoidal nanoparticles (GdTi-SC NPs), whose r₁ increases significantly upon UV irradiation. The reduced water contact angle and the increased number of surface hydroxyl groups substantiate the existence of the PISA effect, which considerably promotes the efficiency of paramagnetic relaxation enhancement (PRE) and thus the imaging performance of GdTi-SC NPs. In vivo MRI of SD rats with GdTi-SC NPs further demonstrates that GdTi-SC NPs could serve as a high-performance CA for sensitive imaging of blood vessels and accurate diagnosis of vascular lesions, indicating the success of our strategy.

Boosting Vascular Imaging-Performance and Systemic Biosafety of Ultra-Small NaGdF4 Nanoparticles via Surface Engineering with Rationally Designed Novel Hydrophilic Block Co-Polymer

Revealing the anatomical structures, functions, and distribution of vasculature via contrast agent (CA) enhanced magnetic resonance imaging (MRI) is crucial for precise medical diagnosis and therapy. The clinically used MRI CAs strongly rely on Gd-chelates, which exhibit low T₁ relaxivities and high risks of nephrogenic systemic fibrosis (NSF) for patients with renal dysfunction. It is extremely important to develop high-performance and safe CAs for MRI. Herein, it is reported that ultra-small NaGdF₄ nanoparticles (UGNs) can serve as an excellent safe MRI CA via surface engineering with rationally designed novel hydrophilic block co-polymer (BP_n ). By optimizing the polymer molecular weights, the polymer-functionalized UGNs (i.e., UGNs-BP₁₄ ) are obtained to exhibit remarkably higher relaxivity (11.8 mm^-1 s^-1 at 3.0 T) than Gd-DTPA (3.6 mm^-1 s^-1 ) due to their ultracompact and abundant hydrophilic surface coating. The high performance of UGNs-BP₁₄ enables us to sensitively visualize microvasculature with a small diameter of ≈0.17 mm for up to 2 h, which is the thinnest blood vessel and the longest time window for low field (1.0 T) MR angiography ever reported, and cannot be achieved by using the clinically used Gd-DTPA under the same conditions. More importantly, renal clearable UGNs-BP₁₄ show lower risks of inducing NSF in comparison with Gd-DTPA due to their negligible release of Gd³⁺ ions after modification with the novel hydrophilic block copolymer. The study presents a novel avenue for boosting imaging-performance and systemic biosafety of UGNs as a robust MRI CA with great potential in precise diagnosis of vasculature-related diseases.

A one-pot synthesis of PEGylated plasmonic WO3−x@Eugenol nanoflowers with NIR-controllable antioxidant activities for synergetically combating bacterial biofilm infection

Schematic diagram of dual treatment of bacterial infection.

2D Gadolinium Oxide Nanoplates as T1 Magnetic Resonance Imaging Contrast Agents

Millions of people a year receive magnetic resonance imaging (MRI) contrast agents for the diagnosis of conditions as diverse as fatty liver disease and cancer. Gadolinium chelates, which provide preferred T₁ contrast, are the current standard but face an uncertain future due to increasing concerns about their nephrogenic toxicity as well as poor performance in high-field MRI scanners. Gadolinium-containing nanocrystals are interesting alternatives as they bypass the kidneys and can offer the possibility of both intracellular accumulation and active targeting. Nanocrystal contrast performance is notably limited, however, as their organic coatings block water from close interactions with surface Gadoliniums. Here, these steric barriers to water exchange are minimized through shape engineering of plate-like nanocrystals that possess accessible Gadoliniums at their edges. Sulfonated surface polymers promote second-sphere relaxation processes that contribute remarkable contrast even at the highest fields (r₁ = 32.6 × 10^-3 m Gd^-1 s^-1 at 9.4 T). These noncytotoxic materials release no detectable free Gadolinium even under mild acidic conditions. They preferentially accumulate in the liver of mice with a circulation half-life 50% longer than commercial agents. These features allow these T₁ MRI contrast agents to be applied for the first time to the ex vivo detection of nonalcoholic fatty liver disease in mice.

Single-Atom Gadolinium Anchored on Graphene Quantum Dots as a Magnetic Resonance Signal Amplifier

A single-atom metal doped on carbonaceous nanomaterials has attracted increasing attention due to its potential applications as high-performance catalysts. However, few studies focus on the applications of such nanomaterials as nanotheranostics for simultaneous bioimaging and cancer therapy. Herein, it is pioneeringly demonstrated that the single-atom Gd anchored onto graphene quantum dots (SAGd-GQDs), with dendrite-like morphology, was successfully prepared. More importantly, the as-fabricated SAGd-GQDs exhibits a robustly enhanced longitudinal relaxivity (r₁ = 86.08 mM^-1 s^-1) at a low Gd³⁺ concentration of 2 μmol kg^-1, which is 25 times higher than the commercial Gd-DTPA (r₁ = 3.44 mM^-1 s^-1). In vitro and in vivo studies suggest that the obtained SAGd-GQDs is a highly potent and contrast agent to obtain high-definition MRI, thereby opening up more opportunities for future precise clinical theranostics.

Full-spectrum responsive WO3−x@HA nanotheranostics for NIR-II photoacoustic imaging-guided PTT/PDT/CDT synergistic therapy

A WO_3−x-based nanotheranostic has been successfully fabricated for photoacoustic imaging-guided synergistic tumor targeting therapy in the second near-infrared (NIR-II) biological window.

Dual-Mode Fluorescence and Magnetic Resonance Imaging by Perylene Diimide-Based Gd-Containing Magnetic Ionic Liquids

Bioimaging plays a key role in the diagnosis/treatment of diseases and in scientific research studies. Compared with single imaging techniques, dual-mode and multimode imaging techniques facilitate high accuracy. In this work, a perylene diimide (PDI)-based Gd-containing magnetic ionic liquid, Per-6-Diimi[Gd(NO₃)₄], is reported for dual-modal imaging, in which a Gd(III) complex was used for magnetic resonance imaging (MRI), while PDI was used for fluorescence imaging. Because of the difference in the biological microenvironment, there is a switch between dispersed and aggregated states of Per-6-Diimi[Gd(NO₃)₄] molecules in hydrophobic and hydrophilic media. When it was in the aqueous solution, the intensive π-π interaction of PDI cores made Per-6-Diimi[Gd(NO₃)₄] aggregates to form particles. The paramagnetic nanoparticles ensure prolonging the rotational correlation time, which results in a strong enhancement of MRI with a longitude relaxation coefficient of 14.94 mM^-1 s^-1. In an in vivo MRI experiment, the tumor site is imaged by MRI through the enhanced permeability and retention effect. However, when the molecule is present on the hydrophobic membrane of the cells, the dispersed Per-6-Diimi[Gd(NO₃)₄] showed good fluorescence imaging capabilities due to the high fluorescence quantum yield of PDI. Thus, the fluorescence imaging of cells can be carried out. Moreover, ex vivo fluorescence imaging of organs is performed after MRI. Per-6-Diimi[Gd(NO₃)₄] is enriched in the liver, kidneys, and tumors.

Effect of conducting/thermoresponsive polymer ratio on multitasking nanogels

Semi-interpenetrated nanogels (NGs) able to release and sense diclofenac (DIC) have been designed to act as photothermal agents with the possibility to ablate cancer cells using mild-temperatures (<45 °C). Combining mild heat treatments with simultaneous chemotherapy appears as a very promising therapeutic strategy to avoid heat resistance or damaging the surrounding tissues. Particularly, NGs consisted on a poly(N-isopropylacrylamide) (PNIPAM) and dendritic polyglycerol (dPG) mesh containing a semi-interpenetrating network (SIPN) of poly(hydroxymethyl 3,4-ethylenedioxythiophene) (PHMeEDOT). The PHMeEDOT acted as photothermal and conducting agent, while PNIPAM-dPG NG provided thermoresponsivity and acted as stabilizer. We studied how semi-interpenetration modified the physicochemical characteristics of the thermoresponsive SIPN NGs and selected the best condition to generate a multifunctional photothermal agent. The thermoswitchable conductiveness of the multifunctional NGs and the redox activity of DIC could be utilized for its electrochemical detection. Besides, as proof of the therapeutic concept, we investigated the combinatorial effect of photothermal therapy (PTT) and DIC treatment using the HeLa cancer cell line in vitro. Within 15 min NIR irradiation without surpassing 45 °C we were able to kill 95% of the cells, demonstrating the potential of SIPN NGs as drug carriers, sensors and agents for mild PTT.

pH-responsive Ag2S nanodots loaded with heat shock protein 70 inhibitor for photoacoustic imaging-guided photothermal cancer therapy

Heat-treated cancer cells have thermo-resistance due to the up-regulated levels of heat shock proteins (HSP) resulting in low therapeutic efficiency and ineffective ablation of tumors. In this work, we report pH-responsive Ag₂S nanodots (Ag₂S NDs) loaded with HSP70 inhibitor (QE-PEG-Ag₂S) for enhanced photothermal cancer therapy. QE-PEG-Ag₂S was easily prepared via self-assembly of hydrophobic Ag₂S NDs, amphiphilic pH-responsive PEG_5k-PAE_10k polymer, and an HSP70 inhibitor quercetin (QE). QE-PEG-Ag₂S has ideal water-solubility and biocompatibility, can rapidly enter cells, and preferentially accumulate in cell lysosomes. The slightly acidic environment of tumor cells and the acidity of lysosomes as well as the high temperature generated by photothermal therapy under irradiation of NIR light (808 nm) promote the release of the inhibitor molecules to reduce the heat resistance of cancer cells and improve the in vivo photothermal therapy efficiency. Moreover, QE-PEG-Ag₂S has good photoacoustic imaging (PAI) ability; this QE-PEG-Ag₂S concentration dependent signal can precisely follow the accumulation of the nanomaterials in tumors and dictate the correct time for light therapy. As a result, QE-PEG-Ag₂S achieved complete tumor ablation effect with no recurrence when only irradiated with NIR light for 10 min. This approach offers a new approach for the theranostic applications of Ag₂S NDs. STATEMENT OF SIGNIFICANCE: In this work, pH-responsive Ag₂S nanodots loaded with the heat shock protein inhibitor for enhanced photothermal cancer therapy have been simply prepared via self-assembly process. This nanoagent possesses ideal water-solubility and biocompatibility, can rapidly enter cells, and preferentially accumulate in cell lysosomes. The acidic environment of tumor cells and the acidity of lysosomes, as well as the high temperature generated by photothermal therapy under irradiation of NIR light promote the release of the inhibitor molecules from the nanoagent to improve the in vivo photothermal therapy efficiency. Moreover, the photoacoustic imaging (PAI) of the nanoagent can precisely follow the accumulation of the nanomaterials in tumors and dictate the light therapy time to guarantee the complete tumor ablation effect with no recurrence.

Functional gadolinium-based nanoscale systems for cancer theranostics

Cancer theranostics is a new strategy for combating cancer that integrates cancer imaging and treatment through theranostic agents to provide an efficient and safe way to improve cancer prognosis. Design and synthesis of these cancer theranostic agents are crucial since these agents are required to be biocompatible, tumor-specific, imaging distinguishable and therapeutically efficacious. In this regard, several types of gadolinium (Gd)-based nanomaterials have been introduced to combine different therapeutic agents with Gd to enhance the efficacy of therapeutic agents. At the same time, the entire treatment procedure could be monitored via imaging tools due to incorporation of Gd ions, Gd chelates and Gd/other imaging probes in the theranostic agents. This review aims to overview recent advances in the Gd-based nanomaterials for cancer theranostics and perspectives for Gd nanomaterial-based cancer theranostics are provided.

Fe@Fe3Ge2 nanoparticles for MR imaging-guided NIR-driven photodynamic therapy in vivo

Photodynamic therapy (PDT) has attracted much attention as a useful technique for disease therapy, considering its minimum invasiveness, high spatial-temporal control, and specific lesion destruction. However, the limited generation of singlet oxygen (1O2) in PDT has restricted the practical biomedical applications of photosensitizers. To overcome this issue, we first developed iron nanoparticles as an Fe nanotemplate to synthesize iron germanium nanoalloy coated iron nanoparticles (Fe@Fe3Ge2 NPs), which possess strong near-infrared (NIR) absorption, as a highly stable photosensitizer and to generate 1O2 effectively under irradiation by an 808 nm laser for NIR-PDT via the mitochondrial apoptotic pathway. Taking advantage of the strong magnetic properties of the Fe nanotemplates and the effective generation of 1O2 by Fe3Ge2 nanoshells, Fe@Fe3Ge2 NPs could be applicable for efficient targeted magnetic resonance imaging-guided NIR-PDT in an αvβ3-positive U87MG glioblastoma model. This work marks an important step forward in developing a novel nanoparticulated theranostic agent for accurate clinical cancer theranostics in the future.

Cu3BiS3 Nanocrystals as Efficient Nanoplatforms for CT Imaging Guided Photothermal Therapy of Arterial Inflammation

Cardio-cerebrovascular diseases caused by chronic inflammatory atherosclerosis seriously damage human health. Nano-photothermal technology has been proven to inhibit the development of vascular inflammation, but the currently reported photothermal agents cannot efficient monitor it during the development of the disease. Herein, we designed and prepared an efficient bifunctional nanoplatform for CT imaging guided photothermal therapy of arterial inflammation. Cu₃BiS₃ nanocrystals with a size of about 12 nm were synthesized by a simple hydrothermal method. The as-prepared Cu₃BiS₃ nanocrystals showed intense absorption in the NIR region, thus exhibited amazing photothermal effect. The photothermal conversion efficiency of Cu₃BiS₃ nanocrystals was reach up to 58.6% under the excitation of an 808 nm laser with a power density of 0.4 W cm^–2. Cu₃BiS₃ nanocrystals can efficiently kill the macrophages both in vitro and in vivo, which plays an important role in the development of atherosclerosis, thus can be used as an effective way to inhibit the occurrence of hypertension. Importantly, Cu₃BiS₃ nanocrystals can be used as an efficient CT contrast agent to monitor carotid inflammation. Our work provides an insight for imaging guided photothermal therapy of arterial inflammation.

Dual-Stimuli-Responsive Multifunctional Gd2Hf2O7 Nanoparticles for MRI-Guided Combined Chemo-/Photothermal-/Radiotherapy of Resistant Tumors

The design and synthesis of a novel generation of a nanoscaled platform with imaging-guided therapy remain a real challenge. It can not only improve the imaging sensitivity of tumor tissues for guiding all kinds of treatments but also reduce the harm for healthy tissues. Here, polydopamine (PDA), polyethylene glycol (PEG), and c(RGDyK) peptide (RGD)-modified and cisplatin-loaded Gd₂Hf₂O₇ nanoparticles (Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs) are designed for magnetic resonance imaging (MRI)-guided combined chemo-/photothermal-/radiotherapy of resistant tumors. The as-prepared NPs display high relaxivity (r₁ = 38.28 mM^-1 s^-1) as an MRI contrast agent because of their ultrasmall size and surface modification with polyacrylic acid and PDA. Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs exhibit pH and NIR dual-stimuli responsiveness for cisplatin release. Based on competent NIR absorption and high X-ray attenuation efficiency, Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs show potential photothermal effect by exposing to an 808 nm NIR laser and significantly improve the generation of reactive oxygen species after X-ray radiation. Combined chemo-/photothermal-/radiotherapy can effectively treat the resistant A549R cells, providing the enhanced therapeutic efficiency to cancer tissues and the reduced side effect to healthy tissues. Furthermore, Gd₂Hf₂O₇@PDA@PEG-Pt-RGD NPs present no obvious toxicity during the treatment, which demonstrates the potential as an efficient MRI-guided combined chemo-/photothermal-/radiotherapy nanoplatform for drug-resistant tumors.

Hollow Mesoporous Bi@PEG-FA Nanoshell as a Novel Dual-Stimuli-Responsive Nanocarrier for Synergistic Chemo-Photothermal Cancer Therapy

The development of stimuli-responsive multifunctional nanocarriers for therapeutic drug delivery is extremely desirable for highly specific treatment of disease. Herein, thiol-polyethylene glycol-folate acid-modified hollow mesoporous bismuth nanoshells (HM-Bi@PEG-FA NSs) were developed as the new dual-stimuli-responsive single-"elemental" photothermal nanocarriers for synergistic chemo-photothermal therapy of tumor. The designed hollow-mesoporous-type nanocarriers present excellent photothermal conversion capacity (∼34.72%) and good biocompatibility. Meanwhile, acidic pH and near-infrared (NIR) laser dual-stimulated doxorubicin (DOX) release is successfully achieved. More importantly, the DOX-loaded HM-Bi@PEG-FA NSs hold an efficient in vitro/in vivo antitumor effect through the synergistic chemo-photothermal therapy. Therefore, our findings provide the possibility of designing a dual-stimuli-responsive hollow mesoporous Bi-based photothermal nanocarrier for synergistically enhanced antitumor therapy.

Tetramodal Imaging and Synergistic Cancer Radio-Chemotherapy Enabled by Multiple Component-Encapsulated Zeolitic Imidazolate Frameworks

The abundant species of functional nanomaterials have attracted tremendous interests as components to construct multifunctional composites for cancer theranostics. However, their distinct chemical properties substantially require a specific strategy to integrate them in harmony. Here, we report the preparation of a distinctive multifunctional composite by encapsulating small-sized semiconducting copper bismuth sulfide (CBS) nanoparticles and rare-earth down-conversion (DC) nanoparticles in larger-sized zeolitic imidazolate framework-8 (ZIF8) nanoparticles, followed by loading an anticancer drug, doxorubicin (DOX). Such composites can be used for tetramodal imaging, including traditional computed tomography and magnetic resonance imaging and, recently, for photoacoustic imaging and fluorescence imaging. With a pH-responsive release of the encapsulated components, synergistic radio-chemotherapy with a high (87.6%) tumor inhibition efficiency is achieved at moderate doses of the CBS&DC-ZIF8@DOX composite with X-ray irradiation. This promising strategy highlights the extending capacity of zeolitic imidazolate frameworks to encapsulate multiple distinct components for enhanced cancer imaging and therapy.

Moderate cooling coprecipitation for extremely small iron oxide as a pH dependent T1-MRI contrast agent

Iron based nanomedicine (IBNM) has been one powerful diagnostic tool as a magnetic resonance imaging (MRI) contrast agent (CA) in the clinic for years. Conventional IBNMs are generally employed as T₂-MRI CAs, but most of them are constrained in clinical indication expansion by magnetic susceptibility artifacts. In comparison, extremely small iron oxide (ESIO) with a core size less than 5 nm has demonstrated the T₁-MRI effect, which provides prospects for a Gd-based agent alternative. Nevertheless, currently developed ESIOs for T₁-MRI CAs always require harsh conditions such as a high temperature and high boiling point reagent. Moreover, very few of the currently developed ESIOs meet the stringent pharmaceutical standard. Herein, on the basis of a crystal nuclear precipitation-dissolution equilibrium mechanism and outer/inner sphere T₁-MRI theory, monodisperse ESIOs with an average size of 3.43 nm (polydispersity index of 0.104) are fabricated using a moderate cooling procedure with mild coprecipitation reaction conditions. The as-synthesized ESIOs display around 3-fold higher T₁ MRI signal intensity than that of commercial Ferumoxytol (FMT), comparable to that of Gd-based CAs in vitro. Additionally, the T₁-MRI performance of the ESIOs is pH dependent and delivers bright signal augmentation. Eventually, the internalization into mesenchymal stem cells of the ESIO is realized in the absence of a transferring agent. Considering the identical structure and composition of the ESIOs as compared to that of FMT, they could meet the pharmaceutical criteria, thus providing great potential as T₁-MRI Cas, for instance as stem cell tracers.

Ag@TiO2 Nanoprisms with Highly Efficient Near-Infrared Photothermal Conversion for Melanoma Therapy

Melanoma is a primary reason of death from skin cancer and associated with high lethality. Photothermal therapy (PTT) has been developed into a powerful cancer treatment technique in recent years. Here, we created a low-cost and high-performance PTT agent, Ag@TiO₂ NPs, which possesses a high photothermal conversion efficiency of ≈65 % and strong near-infrared (NIR) absorption about 808 nm. Ag NPs were synthesized using a two-step method and coated with TiO₂ to obtain Ag@TiO₂ NPs by a facile sol-gel method. Because of the oxide, Ag@TiO₂ NPs exhibit remarkable high photothermal conversion efficiencies and biocompatibility in vivo and in vitro. Cytotoxicity and therapeutic efficiency of photothermal cytotoxicity of Ag@TiO₂ NPs were tested in B16-F10 cells and C57BL/6J mice. Under light irradiation, the elevated temperature causes cell death in Ag NPs-treated (100 μg mL^-1 ) cells in vitro (both p<0.01). In the case of subcutaneous melanoma tumor model, Ag@TiO₂ NPs (100 μg mL^-1 ) were injected into the tumor and irradiated with a 808 nm laser of 2 W cm^-2 for 1 minute. As a consequence, the tumor volume gradually decreased by NIR laser irradiation with only a single treatment. The results demonstrate that Ag@TiO₂ NPs are biocompatible and an attractive photothermal agent for cutaneous melanoma by local delivery.

Multivalency-assisted membrane-penetrating siRNA delivery sensitizes photothermal ablation via inhibition of tumor glycolysis metabolism

The success of photothermal therapy (PTT) is often hampered by the thermo-resistance of tumor cells mediated by over-expressed heat shock proteins (HSPs). Herein, we developed a guanidine-rich, spherical helical polypeptide (DPP) with multivalency-assisted strong membrane penetrating capability, which mediated effective RNAi against tumor glycolysis metabolism to sensitize PTT. ICG was loaded into the internal cavity of DPP, and siRNA against pyruvate kinase M2 (siPKM2) was condensed by DPP to form positively charged nanocomplexes (NCs). The NCs were further coated with human serum albumin to enhance serum stability, prolong blood circulation, and improve tumor targeting. Due to its multivalent topology, DPP exhibited stronger membrane activity yet lower cytotoxicity than its linear analogue (LPP), thus enabling efficient PKM2 silencing in MCF-7 cells in vitro (~75%) and in vivo (~70%). The PKM2 silencing inhibited tumor glycolysis metabolism and further depleted the energy supply for HSPs production, thus overcoming the heat endurance of tumor cells to strengthen ICG-mediated photothermal ablation. Additionally, siPKM2-mediated energy depletion led to tumor cell starvation, which imparted synergistic anti-cancer effect with PTT. This study therefore provides a promising strategy for designing membrane-penetrating siRNA delivery materials, and it renders a unique RNAi-mediated anti-metabolic mechanism in sensitizing PTT and enabling starvation therapy.

BMP-2-Loaded HAp:Ln3+ (Ln = Yb, Er, Gd) Nanorods with Dual-Mode Imaging for Efficient MC3t3-E1 Cell Differentiation Regulation

Effective bone tissue reconstitution improves the treatment success rate of dental implantation and preserves natural teeth during periodontal tissue repair. Hydroxyapatite (HAp) has received much attention in bone remodeling field because its mineralized structure is similar to that of the natural bone tissue. For this reason, it has been used as a carrier for growth factors. Although HAp possesses outstanding biomedical properties, its capacity of loading and releasing bone growth factors and promoting osteogenesis is not well understood. In this study, Ln³⁺ (Ln = Yb³⁺, Er³⁺, Gd³⁺)-doped HAp (HAp:Ln³⁺) nanorods were synthesized by one-step hydrothermal method. To improve its biocompatibility and surface properties, bone morphogenetic protein-2 (BMP-2) was loaded onto the surface of HAp:Ln³⁺ nanorods. The results showed that BMP-2 incorporation promoted bone formation and enhanced the expression of early bone-related gene and protein (RunX2, SP7, OPN). In addition, Yb³⁺- and Er³⁺-doped HAp nanorods were examined by upconversion luminescence with 980 nm near-infrared laser irradiation to monitor the delivery position of BMP-2 protein. Furthermore, due to the positive magnetism correlated with the concentration of Gd³⁺, HAp:Ln³⁺ with enhanced contrast brightening can be deemed as T₁ MIR contrast agents. These findings indicate that HAp doped with rare-earth ions and loaded with BMP-2 has the potential to promote bone tissue repair and execute dual-mode imaging.

Hollow mesoporous carbon nanospheres for imaging-guided light-activated synergistic thermo-chemotherapy

Carbon-based light-activated materials can absorb optical energy to generate photoacoustic (PA) signals for imaging or transduce optical photons to thermal energy, which holds great promise for biomedical applications. Herein, we synthesize hollow and mesoporous carbon nanospheres (HMCNs) with uniform size on a large scale. The properties of hollow cavity and mesoporous structures make the HMCNs achieve high drug loading (480 mg DOX per g HMCNs). The present intense near infrared (NIR) absorbance achieves excellent photoacoustic imaging ability and photothermal conversion efficacy (32.0%). More interestingly, the encapsulated drugs can have a triggered release under NIR irradiation. The investigations in vitro and in vivo demonstrate that HMCNs have excellent biocompatibility, and accumulate in tumors by the enhanced permeability and retention (EPR) effect. Moreover, under NIR irradiation, in vivo evaluation shows that HMCNs can perform strong PA imaging, and induce great tumor inhibition by the combination of chemotherapy and PTT under the guidance of photoacoustic imaging. The present study provides new insight for design of novel biocompatible light-activated carbons for cancer nanotheranostics.

Nanocatalytic Medicine

Catalysis and medicine are often considered as two independent research fields with their own respective scientific phenomena. Promoted by recent advances in nanochemistry, large numbers of nanocatalysts, such as nanozymes, photocatalysts, and electrocatalysts, have been applied in vivo to initiate catalytic reactions and modulate biological microenvironments for generating therapeutic effects. The rapid growth of research in biomedical applications of nanocatalysts has led to the concept of "nanocatalytic medicine," which is expected to promote the further advance of such a subdiscipline in nanomedicine. The high efficiency and selectivity of catalysis that chemists strived to achieve in the past century can be ingeniously translated into high efficacy and mitigated side effects in theranostics by using "nanocatalytic medicine" to steer catalytic reactions for optimized therapeutic outcomes. Here, the rationale behind the construction of nanocatalytic medicine is eludicated based on the essential reaction factors of catalytic reactions (catalysts, energy input, and reactant). Recent advances in this burgeoning field are then comprehensively presented and the mechanisms by which catalytic nanosystems are conferred with theranostic functions are discussed in detail. It is believed that such an emerging catalytic therapeutic modality will play a more important role in the field of nanomedicine.

Biomodal Tumor-Targeted and Redox-Responsive Bi2 Se3 Hollow Nanocubes for MSOT/CT Imaging Guided Synergistic Low-Temperature Photothermal Radiotherapy

Hyperthemia (>50 °C) induced heating damage of nearby normal organs and inflammatory diseases are the main challenges for photothermal therapy (PTT) of cancers. To overcome this limitation, a redox-responsive biomodal tumor-targeted nanoplatform is synthesized, which can achieve multispectral optoacoustic tomography/X-ray computed tomography imaging-guided low-temperature photothermal-radio combined therapy (PTT RT). In this study, Bi₂ Se₃ hollow nanocubes (HNCs) are first fabricated based on a mild cation exchange way and Kirkendall effect and then modified with hyaluronic acid (HA) through redox-cleavable linkage (-s-s-), thus enabling the HNC to target cancer cells overexpressing CD-44 and control the cargo release profile. Finally, gambogic acid (GA), a type of heat-shock protein (HSP) inhibitor, which is vital to cells resisting heating-caused damage is loaded, into Bi₂ Se₃ HNC. Such HNC-s-s-HA/GA under a mild NIR laser irradiation can induce efficient cancer cell apoptosis, achieving PTT under relatively low temperature (≈43 °C) with remarkable cancer cell damage efficiency. Furthermore, enhanced radiotherapy (RT) can also be experienced without depth limitation based on RT sensitizer Bi₂ Se₃ HNC. This research designs a facile way to synthesize Bi₂ Se₃ HNC-s-s-HA/GA possessing theranostic functionality and cancer cells-specific GSH, but also shows a low-temperature PTT RT method to cure tumors in a minimally invasive and highly efficient way.

Lanthanide-Doped Photoluminescence Hollow Structures: Recent Advances and Applications

Lanthanide-doped nanomaterials have attracted significant attention for their preeminent properties and widespread applications. Due to the unique characteristic, the lanthanide-doped photoluminescence materials with hollow structures may provide advantages including enhanced light harvesting, intensified electric field density, improved luminescent property, and larger drug loading capacity. Herein, the synthesis, properties, and applications of lanthanide-doped photoluminescence hollow structures (LPHSs) are comprehensively reviewed. First, different strategies for the engineered synthesis of LPHSs are described in detail, which contain hard, soft, self-templating methods and other techniques. Thereafter, the relationship between their structure features and photoluminescence properties is discussed. Then, niche applications including biomedicines, bioimaging, therapy, and energy storage/conversion are focused on and superiorities of LPHSs for these applications are particularly highlighted. Finally, keen insights into the challenges and personal prospects for the future development of the LPHSs are provided.

Bovine serum albumin-templated nanoplatform for magnetic resonance imaging-guided chemodynamic therapy

BACKGROUND

Nanotechnology in medicine has greatly expanded the therapeutic strategy that may be explored for cancer treatment by exploiting the specific tumor microenvironment such as mild acidity, high glutathione (GSH) concentration and overproduced hydrogen peroxide (H2O2). Among them, tumor microenvironment responsive chemodynamic therapy (CDT) utilized the Fenton or Fenton-like reaction to produce excess hydroxyl radical (·OH) for the destruction of tumor cells. However, the produced ·OH is easily depleted by the excess GSH in tumors, which would undoubtedly impair the CDT's efficiency. To overcome this obstacle and enhance the treatment efficiency, we design the nanoplatforms for magnetic resonance imaging (MRI)-guided CDT.

RESULTS

In this study, we applied the bovine serum albumin (BSA)-templated CuS:Gd nanoparticles (CuS:Gd NPs) for MRI-guided CDT. The Cu2+ in the CuS:Gd NPs could be reduced to Cu+ by GSH in tumors, which further reacted with H2O2 and triggered Fenton-like reaction to simultaneously generate abundant ·OH and deplete GSH for tumor enhanced CDT. Besides, the Gd3+ in CuS:Gd NPs endowed them with excellent MRI capability, which could be used to locate the tumor site and monitor the therapy process preliminarily.

CONCLUSIONS

The designed nanoplatforms offer a major step forward in CDT for effective treatment of tumors guided by MRI.

CuCo2S4 nanocrystals as a nanoplatform for photothermal therapy of arterial inflammation

Ultrasmall CuCo2S4 nanocrystals (NCs) have been demonstrated as an effective agent in the photothermal therapy (PTT) of tumors, but have not been investigated for treatment of arterial inflammation, which is critical in the initiation and development of atherosclerosis (AS), a leading cause of vascular diseases worldwide. In this study, CuCo2S4 NCs were synthesized and used as an efficient PTT nanoplatform for arterial inflammation. In vitro experiments illustrated an effective ablation of inflammatory macrophages by CuCo2S4 incubation combined with the irradiation with an 808 nm near-infrared (NIR) laser. In vivo experiments in an apolipoprotein E knockout (Apo E-/-) mouse model showed that the local injection with CuCo2S4 followed by irradiation with an 808 nm NIR laser notably ablated infiltrating inflammatory macrophages and effectively reduced arterial inflammation and arterial stenosis. This work provides a new strategy for treatment of AS by exploring bimetal sulfides as effective PTT agents.

Ultrathin Tellurium Oxide/Ammonium Tungsten Bronze Nanoribbon for Multimodality Imaging and Second Near-Infrared Region Photothermal Therapy

Developing nanophotothermal agents (PTAs) with satisfied photothermal conversion efficiency (PTCE) in the second NIR window (1000-1350 nm, NIR II) holds great promise for enhanced photothermal therapy effect. Herein, we develop a NIR-II PTA with advanced PTCE, based on a new two-dimensional ultrathin tellurium oxide/ammonium tungsten bronze (TeO₂/(NH₄) _xWO₃) nanoribbons (TONW NRs). The doped ammonia ions-mediated-free-electrons injection into the lowest unoccupied molecular orbital band of WO₃ combined with the electronic transitions between W⁶⁺ ions and the lone pair of electrons in Te atoms achieve excellent NIR absorption of TONW NRs resulting from localized surface plasmon resonance. The polyethylene glycol functionalized TONW NRs (PEG-TONW NRs) exhibit good stability and biocompatibility, displaying a PTCE high to 43.6%, surpassing many previous nano-PTAs active in the NIR II region, leading to remarkable tumor ablation ability both in vitro and in vivo. Meanwhile, advanced X-ray computed tomography (CT) and photoacoustic (PA) imaging capability of PEG-TONW NRs were also realized. Given the admirable photothermal effect in NIR II region, good biocompatibility, and advanced CT/PA imaging diagnosis capability, the novel PEG-TONW NRs is promising in future personalized medicine applications.

Structure-Relaxivity Relationships of Magnetic Nanoparticles for Magnetic Resonance Imaging

Magnetic nanoparticles (MNPs) have been extensively explored as magnetic resonance imaging (MRI) contrast agents. With the increasing complexity in the structure of modern MNPs, the classical Solomon-Bloembergen-Morgan and the outer-sphere quantum mechanical theories established on simplistic models have encountered limitations for defining the emergent phenomena of relaxation enhancement in MRI. Recent progress in probing MRI relaxivity of MNPs based on structural features at the molecular and atomic scales is reviewed, namely, the structure-relaxivity relationships, including size, shape, crystal structure, surface modification, and assembled structure. A special emphasis is placed on bridging the gaps between classical simplistic models and modern MNPs with elegant structural complexity. In the pursuit of novel MRI contrast agents, it is hoped that this review will spur the critical thinking for design and engineering of novel MNPs for MRI applications across a broad spectrum of research fields.

Oxygenated theranostic nanoplatforms with intracellular agglomeration behavior for improving the treatment efficacy of hypoxic tumors

Hypoxia plays vital roles in the development of tumor resistance against typical anticancer therapies and local reoxygenation has proved effective to overcome the hypoxia-induced chemoresistance. Perfluorocarbon (PFC) is an FDA approved oxygen carrier and currently vigorously investigated for oxygen delivery to tumors. This study reports a perfluorocarbon and etoposide (EP) loaded porous hollow Fe₃O₄-based theranostic nanoplatform capable of delivering oxygen to solid tumors to enhance their susceptibility against EP. Results show that oxygen could be released at a moderate rate from the porous hollow magnetic Fe₃O₄ nanoparticles (PHMNPs) over an extended period of time, therefore effectively reducing the hypoxia-induced EP resistance of tumor cells. Moreover, the surface of PHMNPs was modified with lactobionic acid (LA)-containing amphiphilic polymers via hydrophobic interaction, which could provide targeting effect against certain types of tumors. The hydrophilic moiety would be subsequently shed by the intratumoral GSH after cellular internalization and result in the agglomeration of nanocarriers inside tumor cells, consequently impeding the nanoparticle exocytosis to enhance their intracellular retention. The enhanced retention could elevate the intracellular EP level and effectively boost the tumor cell killing effect. In addition to the therapeutic benefits, the Fe₃O₄ nanocage could also be used for the magnetic resonance imaging of the tumor area. The assorted benefits of the composite nanosystem are anticipated to be advantageous for the treatment of drug-resistant hypoxic tumors.