Upconversion nanocomposite for programming combination cancer therapy by precise control of microscopic temperature

Metal-Organic Framework-Based Nanoheater with Photo-Triggered Cascade Effects for On-Demand Suppression of Cellular Thermoresistance and Synergistic Cancer Therapy

Nanomedicine with stable light-heat conversion and spatiotemporally controllable drug activation is crucial for the success of photothermal therapy (PTT). Herein, a metal-organic framework (MOF)-based nanoheater with light-triggered multi-responsiveness is engineered to in-situ and on-demand sensitize cancer cells to local hyperthermia. Well-dispersed platinum nanoparticles synthesized inside nanospaces of the MOF are employed as the near-infrared (NIR)-harvesting unit with stable and high light-heat conversion performance. A conformation switchable polymer shell is constructed as a secondary light-responding unit to gate the targeted activation of a molecular inhibitor against thermoresistance. By cascade transformation of light stimuli to downstream signals, the nanoheater enables inhibitor release to go with local heating at the same time restricted in lesion sites to maximize efficacy and minimize systemic toxicity. The efficient photothermal conversion and the blockage of cellular heat-protective pathways provide a dual-mode of action which selectively sensitizes cancer cells to hyperthermia in a spatiotemporally controlled manner. With NIR as the remote switch, the MOF-based nanosystem demonstrates localized and boosted PTT efficacy against cancer both in vitro and in vivo. These results present nanosized MOFs as tailorable and versatile platforms for synergistic and precise cancer therapy.

Ultrasensitive Thermochromic Upconversion in Core-Shell-Shell Nanoparticles for Nanothermometry and Anticounterfeiting

Upconversion nanoparticle based ratiometric nanothermometry has shown many advantages including high relative sensitivity, fast temperature response, and high spatial resolution. However, most of the existing designs are on the basis of thermally coupled upconversion emissions, and it remains a challenge to improve the thermo-sensitivity. Here, we report a new nanoplatform of NaYF₄:Yb/Er/Ce@NaYF₄@NaYF₄:Yb/Tm core-shell-shell nanostructure to improve the thermal sensitivity through the nonthermally coupled upconversion emissions. With the increase of temperature, the green upconversion of Er³⁺ shows a decline while the blue upconversion of Tm³⁺ exhibits a rapid increase, leading to a huge contrast in both intensity ratio and emission colors. The maximum relative sensitivity can reach up to 9.86% K^-1 at 303 K. It is further found that introducing Ce³⁺ is able to improve the sensitivity and expand the thermochromic green-to-blue gamut greatly. These results show great potential in ultrasensitive lanthanide-based nanothermometry and anticounterfeiting.

Fluorescent Imaging-Guided Chemo- and Photodynamic Therapy of Hepatocellular Carcinoma with HCPT@NMOFs-RGD Nanocomposites

Background

Hepatocellular carcinoma (HCC), arising from hepatocytes, is the most common primary liver cancer. It is urgent to develop novel therapeutic approaches to improve the grim prognosis of advanced HCC. 10-hydroxycamptothecin (HCPT) has good antitumor activity in cells; however, its hydrophobicity limits its application in the chemotherapy of HCC. Recently, nanoscale porphyrin metal-organic frameworks have been used as drug carriers due to their low biotoxicity and photodynamic properties.

Methods

Nanoscale zirconium porphyrin metal-organic frameworks (NMOFs) were coated with arginine-glycine-aspartic acid (RGD) peptide to prepare NMOFs-RGD first. The HepG2 cell line, zebrafish embryos and larvae were used to test the biotoxicity and fluorescence imaging capability of NMOFs-RGD both in vitro and in vivo. Then, NMOFs were used as the skeleton, HCPT was assembled into the pores of NMOFs, while RGD peptide was wrapped around to synthesize a novel kind of nanocomposites, HCPT@NMOFs-RGD. The tissue distribution and chemo- and photodynamic therapeutic effects of HCPT@NMOFs-RGD were evaluated in a doxycycline-induced zebrafish HCC model and xenograft mouse model.

Results

NMOFs-RGD had low biotoxicity, good biocompatibility and excellent imaging capability. In HCC-bearing zebrafish, HCPT@NMOFs-RGD were specifically enriched in the tumor by binding specifically to integrin α_vβ₃ and led to a reduction in tumor volume. Moreover, the xenografts in mice were eliminated remarkably following HCPT@NMOFs-RGD treatment with laser irradiation, while little morphological change was found in other main organs.

Conclusion

The nanocomposites HCPT@NMOFs-RGD accomplish tumor targeting and play synergistic chemo- and photodynamic therapeutic effects on HCC, offering a novel imaging-guided drug delivery and theranostic platform.

Luminescent Lifetime Regulation of Lanthanide-Doped Nanoparticles for Biosensing

Lanthanide-doped nanoparticles possess numerous advantages including tunable luminescence emission, narrow peak width and excellent optical and thermal stability, especially concerning the long lifetime from microseconds to milliseconds. Differing from other shorter-lifetime fluorescent nanomaterials, the long lifetime of lanthanide-doped nanomaterials is independent with background fluorescence interference and biological tissue depth. This review presents the recent advances in approaches to regulating the lifetime and applications of bioimaging and biodetection. We begin with the introduction of the strategies for regulating the lifetime by modulating the core-shell structure, adjusting the concentration of sensitizer and emitter, changing energy transfer channel, establishing a fluorescence resonance energy transfer pathway and changing temperature. We then summarize the applications of these nanoparticles in biosensing, including ion and molecule detecting, DNA and protease detection, cell labeling, organ imaging and thermal and pH sensing. Finally, the prospects and challenges of the lanthanide lifetime regulation for fundamental research and practical applications are also discussed.

Engineered lanthanide-doped upconversion nanoparticles for biosensing and bioimaging application

Various fluctuations of intracellular ions, biomolecules, and other conditions in the physiological environment play crucial roles in fundamental biological processes. These factors are of great importance for analysis in biomedical detection. Nevertheless, developments of the simple, rapid, and accurate proof for specific detection still encounter major challenges. Upconversion nanoparticles (UCNPs), which could absorb multiple low-energy near-infrared light (NIR) photon excitation and emits high-energy photons caused by anti-Stokes shift, show unique upconversion luminescence (UCL) properties, for example, sharp emission band, high physicochemical stability like near-zero photobleaching, photo blinking in biological tissues, and long luminescence lifetime. Furthermore, the NIR used for the light source to excite UCNPs enable lower photo-damage effect and deeper penetration of tissue, and in the meantime, it can avoid the auto-fluorescence and light scattering from biological tissue interference. Thus, the lanthanide-doped UCNP-based functional platform with controlled structure, crystalline phase, size, and multicolor emission has become an appropriate nanomaterial for bioapplications such as biosensing, bioimaging, drug release, and therapies. In this review, the recent progress about synthesis and biomedical applications of UCNPs related to sensing and bioimaging is summarized. Firstly, the different luminescence mechanisms of the upconversion process are presented. Secondly, four of the most common methods for synthesizing UCNPs are compared as well as the advantages and disadvantages of these synthetic routes. Meanwhile, the surface modification of lanthanide-doped UCNPs was introduced to pave the way for their biochemistry applications. Next, this review detailed the biological applications of lanthanide-doped UCNPs, particularly in bioimaging, including UCL and multi-modal imaging and biosensing (monitoring intracellular ions and biomolecules). Finally, the challenges and future perspectives in materials science and biomedical fields of UCNPs are concluded: the low quantum yield of the upconversion process should be considered when they are executed as imaging contrast agents. And the biosafety of lanthanide-doped UCNPs needs to be evaluated.

Advances in fluorescence sensing enabled by lanthanide-doped upconversion nanophosphors

Lanthanide-doped upconversion nanoparticles (UCNPs), characterized by converting low-energy excitation to high-energy emission, have attracted considerable interest due to their inherent advantages of large anti-Stokes shifts, sharp and narrow multicolor emissions, negligible autofluorescence background interference, and excellent chemical- and photo-stability. These features make them promising luminophores for sensing applications. In this review, we give a comprehensive overview of lanthanide-doped upconversion nanophosphors including the fundamental principle for the construction of UCNPs with efficient upconversion luminescence (UCL), followed by state-of-the-art strategies for the synthesis and surface modification of UCNPs, and finally describing current advances in the sensing application of upconversion-based probes for the quantitative analysis of various analytes including pH, ions, molecules, bacteria, reactive species, temperature, and pressure. In addition, emerging sensing applications like photodetection, velocimetry, electromagnetic field, and voltage sensing are highlighted.

Rare-Earth Doping in Nanostructured Inorganic Materials

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials. Moreover, rare-earth doping can control the ultimate electronic and catalytic performance of doped nanomaterials in a tunable and scalable manner, enabling significant improvements in energy harvesting and conversion. A better understanding of the critical role of rare-earth doping is a prerequisite for the development of an extensive repertoire of functional nanomaterials for practical applications. In this review, we highlight recent advances in rare-earth doping in inorganic nanomaterials and the associated applications in many fields. This review covers the key criteria for rare-earth doping, including basic electronic structures, lattice environments, and doping strategies, as well as fundamental design principles that enhance the electrical, optical, catalytic, and magnetic properties of the material. We also discuss future research directions and challenges in controlling rare-earth doping for new applications.

Polymeric micelles-based nanoagents enable phototriggering combined chemotherapy and photothermal therapy with high sensitivity

A new type of polymeric nanomicelles-based nanoagent (denoted as PT@MFH hereafter) capable of highly sensitively releasing chemotherapeutic drug paclitaxel (PTX) upon triggering of near-infrared laser was developed by encapsulating PTX...

Fluorescence Thermometer: Intermediation of the Fontal Temperature and Light

The rapid advance of thermal materials and fluorescence spectroscopy has extensively promoted micro-scale fluorescence thermometry development in recent years. Based on the advantages of fast response, high sensitivity, simple operation,...

Near-Infrared Light-Responsive SERS Tags Enable Positioning and Monitoring of the Drug Release of Photothermal Nanomedicines In Vivo

Understanding the in vivo behavior of photothermal nanomedicines (PTNMs) is important for drug development and evaluation. However, it is still very challenging. Herein, two key parameters, i.e., the depth of PTNMs under biological tissue and the drug release ratio of PTNMs in vivo, can be revealed by a near-infrared (NIR) light-responsive surface-enhanced Raman scattering (SERS) strategy. The fabricated PTNMs were composed of waxberry-like gold nanoparticles, model drug curcumin, and an elaborately selected NIR light-responsive Raman reporter (3,3'-diethylthiatricarbocyanine iodide, DTTC). The response mechanism of DTTC to NIR light was investigated as photodegradation. NIR light irradiation heated the gold nanoparticles, triggered the release of a model drug, and simultaneously decreased the SERS intensity of the PTNMs. In vitro experiment results revealed that the SERS intensity decrease could well reflect the depth of PTNMs with a correlation coefficient of more than 0.99. On this basis, after in situ SERS detection, the depth of PTNMs in a tumor could be revealed with satisfactory accuracy. Moreover, the decrease in the SERS intensity of PTNMs showed a highly similar trend to the increase in the drug release, suggesting that it could be used for real-time monitoring of drug release of PTNMs. This study not only opens a new avenue for the release study of many inactive fluorescent and Raman drugs of PTNMs but also provides an effective way for reporting the depth, which greatly promotes the application of PTNMs in vivo.

Luminescence Ratiometric Nanothermometry Regulated by Tailoring Annihilators of Triplet-Triplet Annihilation Upconversion Nanomicelles

Triplet-triplet annihilation (TTA) upconversion is a special non-linear photophysical process that converts low-energy photons into high-energy photons based on sensitizer/annihilator pairs. Here, we constructed a novel luminescence ratiometric nanothermometer based on TTA upconversion nanomicelles by encapsulating sensitizer/annihilator molecules into a temperature-sensitive amphiphilic triblock polymer and obtained good linear relationships between the luminescence ratio (integrated intensity ratio of upconverted luminescence peak to the downshifted phosphorescence peak) and the temperature. We also found chemical modification of annihilators would rule out the interference of the polymer concentration and stereochemical engineering of annihilators would readily regulate the thermal sensitivity.

Temperature-Feedback Nanoplatform for NIR-II Penta-Modal Imaging-Guided Synergistic Photothermal Therapy and CAR-NK Immunotherapy of Lung Cancer

In this study, to visually acquire all-round structural and functional information of lung cancer while performing synergistic photothermal therapy (PTT) and tumor-targeting immunotherapy, a theranostic nanoplatform that introduced upconversion nanoparticles (UCNPs) and IR-1048 dye into the lipid-aptamer nanostructrure (UCILA) is constructed. Interestingly, the IR-1048 dye grafted into the lipid bilayer can serve as the theranostic agent for photoacoustic imaging, optical coherence tomography angiography, photothermal imaging, and PTT in the second near infrared (NIR-II) window. In addition, loaded in the inner part of UCILA, UCNPs possess the superior luminescence property and high X-ray attenuation coefficient, which can act as contrast agents for computed tomography (CT) and thermo-sensitive up-conversion luminescence (UCL) imaging, enabling real-time tracking of metabolic activity of tumor and temperature-feedback PTT. Furthermore, under the complementary guidance of penta-modal imaging and an accurate monitoring of in situ temperature change during PTT, UCILA exhibits its excellent capability for ablating the lung tumor with minimal side effects. Meanwhile, synergistic CAR-NK immunotherapy is carried out specifically to eradicate any possible residual tumor cells after PTT. Therefore, the UCILA nanoplatform is demonstrated as a multifunctional theranostic agent for both penta-modal imaging and temperature-feedback PTT while conducting targeting immunotherapy of lung cancer.

Mapping Drug-Induced Neuropathy through In-Situ Motor Protein Tracking and Machine Learning

Chemotherapy can induce toxicity in the central and peripheral nervous systems and result in chronic adverse reactions that impede continuous treatment and reduce patient quality of life. There is a current lack of research to predict, identify, and offset drug-induced neurotoxicity. Rapid and accurate assessment of potential neuropathy is crucial for cost-effective diagnosis and treatment. Here we report dynamic near-infrared upconversion imaging that allows intraneuronal transport to be traced in real time with millisecond resolution, but without photobleaching or blinking. Drug-induced neurotoxicity can be screened prior to phenotyping, on the basis of subtle abnormalities of kinetic characteristics in intraneuronal transport. Moreover, we demonstrate that combining the upconverting nanoplatform with machine learning offers a powerful tool for mapping chemotherapy-induced peripheral neuropathy and assessing drug-induced neurotoxicity.

Smart Manganese Dioxide-Based Lanthanide Nanoprobes for Triple-Negative Breast Cancer Precise Gene Synergistic Chemodynamic Therapy

Small interfering RNA (siRNA)-based gene therapy has been widely studied as a promising treatment for malignant triple-negative breast cancer (TNBC), but efficient delivery of siRNA still remains a challenge. In this study, a smart manganese dioxide (MnO2)-based lanthanide nanoprobe therapeutic nanoplatform (ErNPs@MnO2-siS100A4-RGD) was developed for tumor imaging and precise stimuli-responsive S100A4 siRNA (siS100A4)-mediated gene therapy in synergism with chemodynamic therapy (CDT) of TNBC. ErNPs@MnO2-siS100A4-RGD has a tumor microenvironment-responsive capability attributed to the presence of MnO2, which can be degraded by glutathione (GSH) in the tumor region while releasing siRNA and generating Mn2+ to achieve precise gene therapy and a Fenton-like reaction-mediated CDT effect on TNBC. Subsequently, the lanthanide nanoprobes (ErNPs) are exposed to the second near-infrared region (NIR-II) fluorescence emission to realize the precise tumor location. Both the in vitro and in vivo results demonstrated that the smart nanoplatform possessed high siRNA delivery efficiency and GSH-responsive precise siRNA releasing ability, and compared with individual gene therapy, the GSH-depletion-enhanced CDT effect further reinforced TNBC inhibition, demonstrating excellent GSH-responsive-enhanced NIR-II precise tumor imaging therapy. These results indicate that the nanoplatform provides a crucial foundation for further research on theranostic systems of TNBC.

Y2O3:Yb3+, Tm3+/ZnO composite with a heterojunction structure and upconversion function for the photocatalytic degradation of organic dyes

Endowing photocatalytic materials with a broader range of light responses is important for improving their performance and solar energy utilization. In this study, a simple sol-gel method was used to prepare Yb³⁺/Tm³⁺-co-doped Y₂O₃ upconversion materials and Y₂O₃:Yb³⁺, Tm³⁺/ZnO (Y/Z) composite photocatalysts for the photocatalytic degradation of dyes. The Y/Z composite photocatalyst achieved degradation rates of 38%, 95%, and 89% for methyl orange, methylene blue (MB), and acid chrome blue K dye solutions, respectively, within 30 minutes. The degradation efficiency for MB after three cycles of degradation was 86%. The spherical Y₂O₃:Yb³⁺, Tm³⁺ particles had diameters of 20-50 nm and attached to the ZnO nanosheets, forming a heterojunction structure with ZnO. Fluorescence spectroscopy showed that Y₂O₃:Yb³⁺, Tm³⁺ could convert near-infrared (NIR) light into three sets of ultraviolet light (290, 320, and 360 nm) under NIR excitation. Photoluminescence spectroscopy demonstrated that the photogenerated electron-hole pair recombination probability of the composite photocatalyst was significantly lower than that of ZnO nanosheets, thereby reducing the energy loss during the migration process. Furthermore, the addition of Y₂O₃:Yb³⁺, Tm³⁺ to ZnO substantially improved the absorption capacity for ultraviolet light, which enhanced the photocatalytic activity. A possible mechanism for the enhanced photocatalytic performance of the Y/Z composites was proposed based on the synergistic effect of heterojunction formation and the photoconversion process. The composite photocatalyst with upconversion characteristics and heterogeneous structure provides a new strategy for removing organic pollutants from water.

Customized Photothermal Therapy of Subcutaneous Orthotopic Cancer by Multichannel Luminescent Nanocomposites

Photothermal therapy (PTT) is a potentially advanced strategy for highly precise cancer treatment. Tumor-microenvironment-activatable agents provide useful tools for PTT, but their photothermal conversion capacities vary and cannot be evaluated in vivo; thus, a general PTT prescription does not work with individual activatable agents. Here, glutathione (GSH)-activatable nanocomposites, silicomolybdate-functionalized NaLuF₄ :Yb,Er@NaLuF₄ @NaLuF₄ :Nd are prepared, for customized PTT of subcutaneous orthotopic cancer. By simultaneously determining intratumoral GSH concentration and the amount of accumulated agent using multiple orthogonal luminescent emissions of nanocomposites, near-infrared absorbance of photothermal conversion agents is evaluated in vivo, based on the optimized irradiating prescriptions (irradiating power density and time) established. This allows customized PTT of each individual case with high efficacy and viability. This work also includes a method for investigating individual intratumoral variation, and the development of the next generation of customized nanomedicine for efficacious PTT of subcutaneous orthotopic cancer.

Near-Infrared-Triggered Upconverting Nanoparticles for Biomedicine Applications

Due to the unique properties of lanthanide-doped upconverting nanoparticles (UCNP) under near-infrared (NIR) light, the last decade has shown a sharp progress in their biomedicine applications. Advances in the techniques for polymer, dye, and bio-molecule conjugation on the surface of the nanoparticles has further expanded their dynamic opportunities for optogenetics, oncotherapy and bioimaging. In this account, considering the primary benefits such as the absence of photobleaching, photoblinking, and autofluorescence of UCNPs not only facilitate the construction of accurate, sensitive and multifunctional nanoprobes, but also improve therapeutic and diagnostic results. We introduce, with the basic knowledge of upconversion, unique properties of UCNPs and the mechanisms involved in photon upconversion and discuss how UCNPs can be implemented in biological practices. In this focused review, we categorize the applications of UCNP-based various strategies into the following domains: neuromodulation, immunotherapy, drug delivery, photodynamic and photothermal therapy, bioimaging and biosensing. Herein, we also discuss the current emerging bioapplications with cutting edge nano-/biointerfacing of UCNPs. Finally, this review provides concluding remarks on future opportunities and challenges on clinical translation of UCNPs-based nanotechnology research.

Recent near-infrared light-activated nanomedicine toward precision cancer therapy

Light has been present throughout the history of mankind and even the universe. It is of great significance to human life, contributing to energy, agriculture, communication, and much more. In the biomedical field, light has been developed as a switch to control medical processes with minimal invasion and high spatiotemporal selectivity. During the past three years, near-infrared (NIR) light as long-wavelength light has been applied to more than 3000 achievements in biological applications due to its deep penetration depth and low phototoxicity. Remotely controlled cancer therapy usually involves the conversion of biologically inert NIR light. Thus, various materials, especially nanomaterials that can generate reactive oxygen species (ROS), ultraviolet (UV)/visual light, or thermal energy and so on under NIR illumination achieve great potential for the research of nanomedicine. Here, we offered an overview of recent advances in NIR light-activated nanomedicine for cancer therapeutic applications. NIR-light-conversion nanotechnologies for both directly triggering nanodrugs and smart drug delivery toward tumor therapy were discussed emphatically. The challenges and future trends of the use of NIR light in biomedical applications were also provided as a conclusion. We expect that this review will spark inspiration for biologists, materials scientists, pharmacologists, and chemists to fight against diseases and boost the future clinical-translational applications of NIR technology-based precision nanomedicine.

2D Core/Shell‐Structured Mesoporous Silicene@Silica for Targeted and Synergistic NIR‐II‐Induced Photothermal Ablation and Hypoxia‐Activated Chemotherapy of Tumors

Silicene nanosheets, the emerging 2D nanomaterial, as the third topology of silicon‐composed materials with distinct physicochemical properties, is a desirable candidate for photothermal‐conversion nanoagent (PTA) and drug‐delivery nanosystems. Inspired by the individual physiochemical properties and structure features of mesoporous silica and 2D silicene, a distinctive 2D core/shell‐structured multifunctional silicon‐composed theranostic nanoplatform (Silicene@Silica) is constructed by coating a mesoporous silica layer onto the surface of 2D silicene nanosheets. The well‐defined mesopores originating from mesoporous silica shell provide the reservoirs for guest drug molecules and the core of silicene produces heat shock upon NIR‐II laser irradiation, aiming to induce the synergistic cancer‐therapeutic modality. Importantly, when AQ4N, hypoxia‐activated prodrug, is introduced into this system, this nanoplatform (Silicene@Silica–AQ4N) exhibits tumor microenvironment (TME)‐responsive and synergistic hyperthermia‐augmented therapeutic bioactivity. Such a nanoplatform can amplify the hypoxia of TME by destroying the tumor microcirculation and then further efficiently activate AQ4N, a DNA affinity agent and topoisomerase II inhibitor. The results reveal that this multifunctional theranostic nanoplatform can efficiently eliminate tumors without recurrence.

Mapping Elevated Temperatures with a Micrometer Resolution Using the Luminescence of Chemically Stable Upconversion Nanoparticles

The temperature-sensitive luminescence of nanoparticles enables their application as remote thermometers. The size of these nanothermometers makes them ideal to map temperatures with a high spatial resolution. However, high spatial resolution mapping of temperatures >373 K has remained challenging. Here, we realize nanothermometry with high spatial resolutions at elevated temperatures using chemically stable upconversion nanoparticles and confocal microscopy. We test this method on a microelectromechanical heater and study the temperature homogeneity. Our experiments reveal distortions in the luminescence spectra that are intrinsic to high-resolution measurements of samples with nanoscale photonic inhomogeneities. In particular, the spectra are affected by the high-power excitation as well as by scattering and reflection of the emitted light. The latter effect has an increasing impact at elevated temperatures. We present a procedure to correct these distortions. As a result, we extend the range of high-resolution nanothermometry beyond 500 K with a precision of 1-4 K. This work will improve the accuracy of nanothermometry not only in micro- and nanoelectronics but also in other fields with photonically inhomogeneous substrates.

Self-Triggered Thermomechanical Metamaterials with Asymmetric Structures for Programmable Response under Thermal Excitations

In this study, we propose self-triggered thermomechanical metamaterials (ST-MM) by applying thermomechanical materials in mechanical metamaterials designed with asymmetric structures (i.e., microstructural hexagons and chiral legs). The thermomechanical metamaterials are observed with programmable mechanical response under thermal excitations, which are used in mechanical metamaterials to obtain chiral tubes with negative Poisson's ratio and microgrippers with temperature-induced grabbing response. Theoretical and numerical models are developed to analyze the thermomechanical response of the ST-MM from the material and structural perspectives. Finally, we envision advanced applications of the ST-MM as chiral stents and thermoresponsive microgrippers with maximum grabbing force of approximately 101.7 N. The emerging ST-MM provide a promising direction for the design and perception of smart mechanical metamaterials.

A Spontaneous Membrane-Adsorption Approach to Enhancing Second Near-Infrared Deep-Imaging-Guided Intracranial Tumor Therapy

Herein, a functional class of microenvironment-associated nanomaterials is reported for improving the second near-infrared (NIR-II) imaging and photothermal therapeutic effect on intracranial tumors via a spontaneous membrane-adsorption approach. Specific peptides, photothermal agents, and biological alkylating agents were designed to endow the nanogels with high targeting specificity, photothermal properties, and pharmacological effects. Importantly, the frozen scanning electron microscopy technology (cryo-SEM) was utilized to observe the self-association of nanomaterials on tumor cells. Interestingly, the spontaneous membrane-adsorption behavior of nanomaterials was captured through direct imaging evidence. Histological analysis showed that the cross-linking adhesion in intracranial tumor and monodispersity in normal tissues of the nanogels not only enhanced the retention time but also ensured excellent biocompatibility. Impressively, in vivo data confirmed that the microenvironment-associated nanogels could significantly enhance brain tumor clearance rate within a short treatment timeframe (only two weeks). In short, utilizing the spontaneous membrane-adsorption strategy can significantly improve NIR-II diagnosis and phototherapy in brain diseases while avoiding high-risk complications.

Solvent- and Temperature-Driven Photoluminescence Modulation in Porous Hofmann-Type SrII-ReV Metal-Organic Frameworks

A unique family of three-dimensional (3D) luminescent Sr^II-Re^V metal-organic frameworks (MOFs), {[Sr^II(MeOH)₅][Re^V(CN)₄(N)(bpen)_0.5]·MeOH}_n [1·MeOH; N^3- = nitrido ligand, bpen = 1,2-bis(4-pyridyl)ethane, and MeOH = methanol], {[Sr^II(MeOH)₄][Re^V(CN)₄(N)(bpee)_0.5]·2MeOH}_n [2·MeOH; bpee = 1,2-bis(4-pyridyl)ethylene], and {[Sr^II(bpy)_0.5(MeOH)₂][Re^V(CN)₄(N)(bpy)_0.5]}_n (3·MeOH; bpy = 4,4'-bipyridine), is reported. They are obtained by the molecular self-assembly of Sr²⁺ ions with tetracyanidonitridorhenate(V) metalloligands, [Re^V(CN)₄(N)]^2-, and pyridine-based organic spacers (L = bpen, bpee, bpy). Such a combination of molecular precursors results in bimetallic Sr^II-Re^V cyanido-bridged layers further bonded by organic ligands into pillared Hofmann-type coordination skeletons. Because of the formation of {Re^V-(L)-Re^V} moieties providing emissive metal-to-ligand charge-transfer states, 1·MeOH-3·MeOH exhibit solid-state room-temperature photoluminescence tunable from green to orange by the applied organic ligand. The most stable MOF of 3·MeOH, based on the alternating {Re^V-(bpy)-Re^V} and {Sr^II-(bpy)-Sr^II} linkages, exhibits three interconvertible, variously solvated phases, methanol-solvated 3·MeOH, hydrated {[Sr^II(bpy)_0.5(H₂O)₂][Re^V(CN)₄(N)(bpy)_0.5]·0.6H₂O}_n (3·H₂O), and desolvated {[Sr^II(bpy)_0.5][Re^V(CN)₄(N)(bpy)_0.5]}_n (3). Their formation was correlated with water and methanol vapor sorption properties investigated for 3·H₂O. The solvent content affects the luminescence mainly by tuning the emission energy within the series of 3·MeOH, 3·H₂O, and 3. All of the obtained compounds exhibit temperature-driven modulation of luminescence, including the shift of the emission maximum and lifetime. The thermochromic luminescent response was found to be sensitive to the presence and type of solvent in the crystal lattice. This work shows that the construction of [Re^V(CN)₄(N)]^2--based MOFs is an efficient route toward advanced solid luminophores tunable by external stimuli such as solvent or temperature.

Aptamer-Functionalized Upconverting Nanoformulations for Light-Switching Cancer-Specific Recognition and In Situ Photodynamic-Chemo Sequential Theranostics

Biomarker-activatable theranostic formulations offer the potential for removing specific tumors with a high diagnostic accuracy and a significant pharmacological effect. Herein, we developed a novel activatable theranostic nanoformulation UAS-PD [upconversion nanophosphor (UCNP)-aptamer/ssDNA-pyropheophorbide-a (PPA)-doxyrubicin (DOX)], which can recognize specific cancer cells with sensitivity and trigger the localized photodynamic destruction and enhanced chemotherapy. UAS-PD was constructed by the conjugation of UCNPs and aptamer probes containing the photosensitizer PPA and the chemotherapeutic drug DOX. When cancer cells are present, the UAS-PD specifically binds to PTK7, an overexpressed protein present on the surface of cancer cells, through conformational recombination of the aptamer structure and switches its upconversion luminescence from 655 to 540 nm. This long-lived ratiometric optical signal provides an ultrasensitive detection limit as low as 3.9 nM for PTK7. Changes in the conformation of UAS-PD can also induce PPA to approach UCNPs, which can produce cytotoxic singlet oxygens under near-infrared excitation to destroy the cell membrane and enhance its permeability for the simultaneously released DOX that targets cellular DNA degradation, which results in a highly effective tumor-killing effect by synergistic extra-intracellular sequential damage.

Dual-Targeting Peptide-Guided Approach for Precision Delivery and Cancer Monitoring by Using a Safe Upconversion Nanoplatform

Using Epstein-Barr virus (EBV)-induced cancer cells and HeLa cells as a comparative study model, a novel and safe dual-EBV-oncoproteins-targeting pH-responsive peptide engineering, coating, and guiding approach to achieve precision targeting and treatment strategy against EBV-associated cancers is introduced. Individual functional peptide sequences that specifically bind to two overexpressed EBV-specific oncoproteins, EBNA1 (a latent cellular protein) and LMP1 (a transmembrane protein), are engineered in three different ways and incorporated with a pH-sensitive tumor microenvironment (TME)-cleavable linker onto the upconversion nanoparticles (UCNP) NaGdF4:Yb3+, Er3+@NaGdF4 (UCNP-P n , n = 5, 6, and 7). A synergistic combination of the transmembrane LMP1 targeting ability and the pH responsiveness of UCNP-P n is found to give specific cancer differentiation with higher cellular uptake and accumulation in EBV-infected cells, thus a lower dose is needed and the side effects and health risks from treatment would be greatly reduced. It also gives responsive UC signal enhancement upon targeted dual-protein binding and shows efficacious EBV cancer inhibition in vitro and in vivo. This is the first example of simultaneous imaging and inhibition of two EBV latent proteins, and serves as a blueprint for next-generation peptide-guided precision delivery nanosystem for the safe monitoring and treatment against one specific cancer.

Dual-Channel Theranostic System for Quantitative Self-Indication and Low-Temperature Synergistic Therapy of Cancer

A conventional theranostic system usually employs a single fluorescence channel to show the pharmacokinetic events, which usually fails to quantitatively reveal the true cumulative drug release and with low accuracy. Herein, indocyanine green (ICG) and chlorins e6 (Ce6) are selected not only as conventional photothermal/photodynamic agents, but also to offer two independent fluorescence channels to cross validate the authenticity of pharmacokinetic events and to quantitatively reveal cumulative drug release in tumor tissues in a "turn on" manner. Employing the Ca²⁺ of amorphous calcium carbonate as a reversible linker, the photosensitivity and fluorescence of Ce6 are physically quenched by ICG during circulation to reduce the side effect of photodynamic therapy (PDT) while being readily restored in tumor tissue to reveal the quantitative drug release. Most importantly, the combination of photothermal therapy (PTT) and PDT allows low-temperature synergistic therapy of cancer through the controlled expression of heat shock protein in cells and mild hyperthermia enhanced reactive oxygen species diffusion/penetration among cells. This work not only develops a facile approach to fabricate a dual-channel theranostic system to precisely indicate the accumulation and quantitative drug release in tumor tissue, but also presents a unique low-temperature synergistic strategy to destroy tumor in an effective and minimally invasive manner.

Optical whispering-gallery mode barcodes for high-precision and wide-range temperature measurements

Temperature is one of the most fundamental physical properties to characterize various physical, chemical, and biological processes. Even a slight change in temperature could have an impact on the status or dynamics of a system. Thus, there is a great need for high-precision and large-dynamic-range temperature measurements. Conventional temperature sensors encounter difficulties in high-precision thermal sensing on the submicron scale. Recently, optical whispering-gallery mode (WGM) sensors have shown promise for many sensing applications, such as thermal sensing, magnetic detection, and biosensing. However, despite their superior sensitivity, the conventional sensing method for WGM resonators relies on tracking the changes in a single mode, which limits the dynamic range constrained by the laser source that has to be fine-tuned in a timely manner to follow the selected mode during the measurement. Moreover, we cannot derive the actual temperature from the spectrum directly but rather derive a relative temperature change. Here, we demonstrate an optical WGM barcode technique involving simultaneous monitoring of the patterns of multiple modes that can provide a direct temperature readout from the spectrum. The measurement relies on the patterns of multiple modes in the WGM spectrum instead of the changes of a particular mode. It can provide us with more information than the single-mode spectrum, such as the precise measurement of actual temperatures. Leveraging the high sensitivity of WGMs and eliminating the need to monitor particular modes, this work lays the foundation for developing a high-performance temperature sensor with not only superior sensitivity but also a broad dynamic range.

Upconversion luminescence and temperature sensing properties of NaGd(WO4)2:Yb3+/Er3+@SiO2 core-shell nanoparticles

Optical thermometry based on the fluorescence intensity ratio (FIR) of two thermally coupled levels in lanthanide ions has potential application in non-contact optical temperature sensing techniques. In this work, a shell of SiO2 with tunable thickness was uniformly coated on NaGd(WO4)2:Yb3+/Er3+ core upconversion nanoparticles (UCNPs). The effects of the silica shell on UC luminescence and thermal sensing properties of core-shell NaGd(WO4)2:Yb3+/Er3+@SiO2 UCNPs were investigated. Under 980 nm laser excitation, the temperature-dependent UC emission spectra of obtained samples were measured. The FIR was analyzed based on the thermally coupled 2H11/2 and 4S3/2 levels of Er3+ in the biological temperature range of 300-350 K, in which the Boltzmann distribution is applied. The emission from the upper 2H11/2 state within Er3+ was enhanced as temperature increased due to the thermal effect. Absolute sensitivities (S A) and relative sensitivities (S R) of the core and core-shell UCNPs were calculated. It was found that after SiO2 coating, the maximum S A was enhanced by ∼2-fold (1.03% K-1 at 350 K). Especially, S A was as high as 2.14% K-1 at 350 K by analyzing the FIR of the non-thermally coupled 2H11/2 and 4F9/2 levels.

Uncovering the Metabolic Origin of Aspartate for Tumor Growth Using an Integrated Molecular Deactivator

Reprogrammed glucose metabolism is vital for cancer cells, but aspartate, an intermediate metabolic product, is the limiting factor for cancer cell proliferation. However, due to the complexity of metabolic pathways, it remains unclear whether glucose is the primary source of endogenous aspartate. Here, we report the design of an innovative molecular deactivator, based on a multifunctional upconversion nanoprobe, to explore the link between glucose and aspartate. This molecular deactivator mainly works in the acidic, hypoxic tumor microenvironment and deactivates multiple types of glucose transporters on cancer cell membranes upon illumination at 980 nm. Cancer cell proliferation in vivo is strongly inhibited by blocking glucose transporters. Our experimental data confirm that the cellular synthesis of aspartate for tumor growth is glucose-dependent. This work also demonstrates the untapped potential of molecularly engineered upconversion nanoprobes for discovering hidden metabolic pathways and improving therapeutic efficacy of conventional antitumor drugs.

Local-structure-dependent luminescence in lanthanide-doped inorganic nanocrystals for biological applications

This feature article overviews the recent advances in the local-structure-dependent luminescence in lanthanide-doped inorganic nanocrystals for various biological applications.

Luminescence properties of Ba4Yb3F17:Er3+ nanocrystals embedded in glass ceramics for optical thermometry

Transparent glass ceramics (GCs) containing Ba₄Yb₃F₁₇:Er³⁺ nanocrystals were successfully fabricated by a traditional melt-quenching method. The formation of Ba₄Yb₃F₁₇ nanocrystals was confirmed by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. Compared with the precursor glass, the enhanced emission intensity and lifetime of GCs indicate that the Er³⁺ ions incorporate into the Ba₄Yb₃F₁₇ nanocrystals after crystallization. The color tuning properties with doping under 980 nm excitation have been systematically discussed. It was found that the red/green ratio increased with Er³⁺ ion doping and the corresponding color changed from greenish-yellow to yellow-green. Furthermore, the temperature-dependent luminescence properties were studied in detail by the fluorescence intensity ratio (FIR) technique. The monotonic change of FIR with temperature indicates that this material is suitable for temperature sensing. At a temperature of 450 K, the relative sensitivity of the prepared sample reached its maximal value of 0.20% K⁻¹. The results show that the GCs containing Ba₄Yb₃F₁₇:Er³⁺ nanocrystals are candidate materials for temperature sensing.

Transparent glass ceramic embedded with Ba₄Yb₃F₁₇:Er³⁺ nanocrystals can be applied as a promising temperature sensor.

A porous material excited by near-infrared light for photo/chemodynamic and photothermal dual-mode combination therapy

Photodynamic therapy (PDT) and photothermal therapy (PTT) are well-developed light therapy methods for cancer; however, both have a few areas that need improvement. A sustained PDT effect depends on the sustained generation of reactive oxygen species (ROS); therefore, adjusting the type of photosensitizer or the reaction mechanism to prolong the duration of the oxidation-reduction reaction is a possible solution for the continuation of the PDT effect. Further, if PTT could be combined with other treatments, it would bring about a more satisfactory therapeutic effect. To increase the treatment effect of the above two therapeutic methods, a collaborative treatment model of photo/chemodynamic therapy (PCDT) and PTT is needed and is the focus of this study. On the one hand, PCDT is a therapy that integrates PDT with Fenton-like reactions, and Fenton-like reactions can help PDT to produce more ROS by making better use of H₂O₂ in the tumor microenvironment. On the other hand, the PTT effect can also promote PCDT effects to some extent because rising temperature can elevate the redox reaction rate. Therefore, a copper oxide semiconductor photosensitizer was selected in this research to realize the abovementioned therapeutic purposes and experimental concepts. A porous silica carrier can facilitate the uniform attachment of the copper oxide photosensitizer to the SiO₂ surface to form a relatively uniform nanostructure, and the nanoporous structure can increase the performance of the whole material to a certain extent. Based on these perspectives, SiO₂@CuO nanotube (NT), an agent of both Fenton-like photosensitization and photothermal reagent, is synthesized by the hydrothermal co-precipitation template approach to shrink the tumor through the combined effect of PCDT and PTT. In this system, copper ions can participate in the Fenton-like reactions and make better use of H₂O₂ to generate more ROS. Herein, 808 nm light was chosen for irradiation because of its suitable excitation ability, applicable penetration and low intrinsic damage. The experimental results show that SiO₂@CuO NT is a promising agent that combines PCDT and PTT for cancer treatment. This work provides guidance for the synthesis of Fenton-like photosensitizers for the PCDT effect.

Lanthanide-Activated Nanoparticles: A Toolbox for Bioimaging, Therapeutics, and Neuromodulation

Owing to their unique features, the past decade has witnessed rapid developments of lanthanide-activated nanoparticles for biological applications. These include highly tunable upconverting and downshifting photoluminescence when illuminated in deep tissue, excellent photostability against blinking and bleaching effects, biocompatibility through versatile surface modification, and ease of achieving multifunctionality, as well as satisfactory signal output. These attributes make lanthanide-doped nanoparticles an ideal toolbox for advanced bioimaging and next-generation therapeutics.The interest in lanthanide-doped nanoparticles for biomedical research arises from their unique optical properties in response to deep-tissue-penetrable light sources. Upon near-infrared irradiation, these nanoparticles with properly doped emitters display photon upconversion with large anti-Stokes shifts and broad-spectrum tunability from the ultraviolet to the visible. It is also possible to achieve orthogonal photoluminescence with variations in wavelength and lifetime. Coupled with surface ligands, dyes, biomolecules, or other types of functional nanomaterials, lanthanide-doped nanoparticles offer new opportunities for applications in bioimaging, advanced oncotherapy, and neuromodulation. Given the possibility of locating downshifting luminescence at "biological transmission windows", exquisite design of lanthanide-doped nanoparticles also enables deep-tissue imaging with high spatial resolution. In addition, these nanoparticles can respond to high-energy photons, such as X-rays, to trigger nonradioactive and radiative pathways, making it possible to develop high-sensitivity X-ray detectors. Precise control of paramagnetic lanthanide ions in nanocrystal lattices also provides advanced materials for high-performance magnetic resonance imaging in medical diagnostics and biomedical research. Full consideration of fundamental attributes of lanthanide-doped nanoparticles will facilitate the design of multifunctional and sensitive probes and improve diagnostic and therapeutic outcomes.In this Account, we categorize various lanthanide-activation strategies into three modes: near-infrared excitation, X-ray irradiation, and magnetic field stimulation. We introduce energy manipulations in upconverting, downshifting, and persistence luminescence in spectral and time domains and discuss how they can be applied in biological practices. We assess general design principles for lanthanide-activated nanosystems with multiple modalities of bioimaging, oncotherapy, and neuromodulation. We also review the current state-of-the-art in the field of lanthanide-based theranostic nanoplatforms, with particular emphasis on energy conversion and nano-/biointerfacing as well as emerging bioapplications. In this context, we also highlight recent advances in controlling optical properties of nanoplatforms for single- or multimodal bioimaging, stimulus-responsive phototherapy, and optogenetics. Finally, we discuss future opportunities and challenges of this exciting research field.

Mapping intracellular thermal response of cancer cells to magnetic hyperthermia treatment

Temperature is a key parameter for optimal cellular function and growth. Temperature perturbation may directly lead to cell death. This can be used in cancer therapies to kill cells in tumors, a therapeutic approach called hyperthermia. To avoid overheating of tumors that may damage healthy tissues, a knowledge of the intracellular temperature reached during the hyperthermia treatment of cancer cells is relevant. Recently, several luminescent intracellular nanothermometers have been proposed; however an application to sense temperature during a hyperthermia treatment is lacking. Here we present a technique to measure intracellular temperature changes in in vitro cancer cell models. For this purpose, we study for the first time the temperature dependence of the green fluorescent protein (GFP)'s fluorescence lifetime parameter. We find the fluorescence lifetime of GFP can be used for nanothermosensing. We use GFP in a bound form to actin filaments as an intracellular thermal reporter. Furthermore, we assess intracellular temperature during in vitro magnetothermal therapy on live HeLa cells incubated with polyacrylic acid-coated iron oxide nanoparticles. Compared to other thermosensitive materials and formulations reported so far, the GFP nanothermosensor is easily expressed via transfection and various GFP variants are commercially available. We foresee that the nanothermometer developed might find widespread applications in cancer therapy research and development.

Holmium(iii) molecular nanomagnets for optical thermometry exploring the luminescence re-absorption effect

Coordination complexes of lanthanide(3+) ions can combine Single-Molecule Magnetism (SMM) with thermally modulated luminescence applicable in optical thermometry. We report an innovative approach towards high performance SMM-based optical thermometers which explores tunable anisotropy and the luminescence re-absorption effect of HoIII complexes. Our concept is shown in dinuclear cyanido-bridged molecules, {[HoIII(4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, 1; Rh, 2; Ir, 3) and their magnetically diluted analogues, {[HoIII x YIII 1-x (4-pyridone)4(H2O)2][MIII(CN)6]}·nH2O (M = Co, x = 0.11, 1@Y; Rh, x = 0.12, 2@Y; Ir, x = 0.10, 3@Y). They are built of pentagonal bipyramidal HoIII complexes revealing the zero-dc-field SMM effect. Experimental studies and the ab initio calculations indicate an Orbach magnetic relaxation with energy barriers varying from 89.8 to 86.7 and 78.7 cm-1 K for 1, 2, and 3, respectively. 1-3 also differ in the strength of quantum tunnelling of magnetization which is suppressed by hyperfine interactions, and, further, by the magnetic dilution. The YIII-based dilution governs the optical properties as 1-3 exhibit poor emission due to the dominant re-absorption from HoIII while 1@Y-3@Y show room-temperature blue emission of 4-pyridone. Within ligand emission bands, the sharp re-absorption lines of the HoIII electronic transitions were observed. Their strong thermal variation was used in achieving highly sensitive ratiometric optical thermometers whose good performance ranges, lying between 25 and 205 K, are adjustable by using hexacyanidometallates. This work shows that HoIII complexes are great prerequisites for advanced opto-magnetic systems linking slow magnetic relaxation with unique optical thermometry exploiting a luminescence re-absorption phenomenon.

What determines the performance of lanthanide-based ratiometric nanothermometers?

Luminescence intensity ratio (LIR) nanothermometers are ideally suited for noninvasive temperature detection of microelectronic devices and living cells, and the painstaking pursuit of new nanothermometers with higher absolute temperature sensitivity (Sa) or relative temperature sensitivity (Sr) has dominated recent research. However, whether higher Sa and Sr values can intrinsically improve the performance of LIR nanothermometers and what factors essentially determine their accuracy have rarely been considered; these considerations are instructive for their design and application while reducing time and costs. Here, we clarify that the accuracy of lanthanide-based LIR nanothermometers is essentially determined by Sr and the relative error of the luminescence intensity (σI/I) but not Sa based on lanthanide-doped NaYF4, YPO4, YVO4, CaF2, YF3, Y2O3, BaTiO3, LaAlO3 and Y3Al5O12 temperature sensors, meaning that our previous pursuit of higher Sa does not contribute to the accuracy of lanthanide-based LIR nanothermometers. Further research reveals that σI/I is primarily influenced by energy level splitting, which can deteriorate the temperature uncertainty. For actual temperature detection of biological tissues, in addition to the above intrinsic factors, we shed light on the effects of probe self-heating, excitation power density, emission intensity and penetration depth on temperature readouts via a polyethyleneimine-modified NaYF4:Er3+/Yb3+@NaYF4-PEI aqueous solution, implying that we will continue to optimize nanothermometers and calibrate readouts according to the local environment. This work unifies the metrics of lanthanide-based LIR nanothermometers, corrects the previous misunderstanding of Sa to mitigate invalid work, and provides careful guidance for their development.

Endogenous H2S-Activable Liposomal Nanoplatform for Synergistic Colorectal Tumor Ablation at Mild Apparent Temperature

Photoinduced hyperthermia possesses great potential in photothermal therapy and thermal-responsive chemotherapy of tumors. However, traditional thermal-triggered drug release requires high temperature, which results in unpleasant activation of thermal-induced cellular self-protection. In this work, a Cu-complex modified and drug-loaded liposomal nanoplatform was constructed for endogenous H₂S-activated synergistic ablation of colorectal tumors. In response to H₂S, the incorporated Cu-complex contributed to the formation of semiconductor CuS on the surface of the as-designed liposomal nanoplatform, which led to local heating under near-infrared (NIR) laser irradiation to achieve simultaneous photothermal therapy and drug release. It is noteworthy that although the drug release occurred at a mild apparent temperature, it was actually triggered by the high eigen temperature on the surface of the liposomal nanoplatform. Therefore, efficient and synergistic photothermal and chemotherapy was achieved under mild apparent temperatures. This work provides insights into achieving selective and bioactivated photothermal therapy and therefore thermal-controlled drug release without using excessive hyperthermia.

Advances and challenges for fluorescence nanothermometry

Fluorescent nanothermometers can probe changes in local temperature in living cells and in vivo and reveal fundamental insights into biological properties. This field has attracted global efforts in developing both temperature-responsive materials and detection procedures to achieve sub-degree temperature resolution in biosystems. Recent generations of nanothermometers show superior performance to earlier ones and also offer multifunctionality, enabling state-of-the-art functional imaging with improved spatial, temporal and temperature resolutions for monitoring the metabolism of intracellular organelles and internal organs. Although progress in this field has been rapid, it has not been without controversy, as recent studies have shown possible biased sensing during fluorescence-based detection. Here, we introduce the design principles and advances in fluorescence nanothermometry, highlight application achievements, discuss scenarios that may lead to biased sensing, analyze the challenges ahead in terms of both fundamental issues and practical implementations, and point to new directions for improving this interdisciplinary field.

Largely enhanced luminescence intensity and improved optical temperature sensing properties in CaWO4-La2(WO4)3: Er3+, Yb3+ via regulating cations composition

High temperature sensing sensitivity and luminescence intensity of phosphors are crucial factors for excellent optical temperature sensing performance. Based on material design, the pure phase and two-phase solid solutions were prepared by regulating the relative content of cations Ca2+ and La3+ in CaWO4-La2(WO4)3, respectively. The up-conversion luminescence (UCL) and optical temperature sensing performance of rare earth ions Er3+/Yb3+ co-doped CaWO4-La2(WO4)3 were studied. As guided by regulating cation composition through partial substituting Ca2+ ions by La3+ ions, the UCL intensity of two-phase solid solutions at 552 nm is much higher than that of pure phase material. The UCL intensity of 0.2La2(WO4)3-0.8CaWO4: 1%Er3+, 5%Yb3+ is as 33.5 times as that of CaWO4: 1%Er3+, 5%Yb3+ material. More importantly, the high temperature sensing sensitivity (0.01026 K-1) is achieved in a wider temperature range 83-683 K in optimal UCL material 0.2La2(WO4)3-0.8CaWO4: 1%Er3+, 5%Yb3+. It is suggested that material design theory can be used as a powerful tool to accelerate discovery of novel optical temperature sensing materials, with implications even for the design of other optoelectronic materials.

Remote Control of Neural Stem Cell Fate Using NIR-Responsive Photoswitching Upconversion Nanoparticle Constructs

Light-mediated remote control of stem cell fate, such as proliferation, differentiation, and migration, can bring a significant impact on stem cell biology and regenerative medicine. Current UV/vis-mediated control approaches are limited in terms of nonspecific absorption, poor tissue penetration, and phototoxicity. Upconversion nanoparticle (UCNP)-based near-infrared (NIR)-mediated control systems have gained increasing attention for vast applications with minimal nonspecific absorption, good penetration depth, and minimal phototoxicity from NIR excitations. Specifically, 808 nm NIR-responsive upconversion nanomaterials have shown clear advantages for biomedical applications owing to diminished heating effects and better tissue penetration. Herein, a novel 808 nm NIR-mediated control method for stem cell differentiation has been developed using multishell UCNPs, which are optimized for upconverting 808 nm NIR light to UV emission. The locally generated UV emissions further toggle photoswitching polymer capping ligands to achieve spatiotemporally controlled small-molecule release. More specifically, with 808 nm NIR excitation, stem cell differentiation factors can be released to guide neural stem cell (NSC) differentiation in a highly controlled manner. Given the challenges in stem cell behavior control, the developed 808 nm NIR-responsive UCNP-based approach to control stem cell differentiation can represent a new tool for studying single-molecule roles in stem cell and developmental biology.

Real-Time Intracellular Temperature Imaging Using Lanthanide-Bearing Polymeric Micelles

Measurement of thermogenesis in individual cells is a remarkable challenge due to the complexity of the biochemical environment (such as pH and ionic strength) and to the rapid and yet not well-understood heat transfer mechanisms throughout the cell. Here, we present a unique system for intracellular temperature mapping in a fluorescence microscope (uncertainty of 0.2 K) using rationally designed luminescent Ln³⁺-bearing polymeric micellar probes (Ln = Sm, Eu) incubated in breast cancer MDA-MB468 cells. Two-dimensional (2D) thermal images recorded increasing the temperature of the cells culture medium between 296 and 304 K shows inhomogeneous intracellular temperature progressions up to ∼20 degrees and subcellular gradients of ∼5 degrees between the nucleolus and the rest of the cell, illustrating the thermogenic activity of the different organelles and highlighting the potential of this tool to study intracellular processes.

H2 S-Scavenged and Activated Iron Oxide-Hydroxide Nanospindles for MRI-Guided Photothermal Therapy and Ferroptosis in Colon Cancer

Overproduced hydrogen sulfide (H₂ S) is of vital importance for the progress of colon cancer and promotes cancer cellular proliferation. Devising pharmacological nanomaterials for tumor-specific H₂ S activation will be significant for precise colon cancer treatment. Herein, a biocompatible fusiform iron oxide-hydroxide nanospindles (FeOOH NSs) nanosystem for magnetic resonance imaging (MRI), ferroptosis, and H₂ S based cascade reaction-enhanced combinational colon cancer treatment is developed. The FeOOH NSs can effectively scavenge endogenous H₂ S via the reduction reaction to prohibit the growth of CT26 colon cancer. The cascade produced FeS driven by overexpressed H₂ S exhibits near-infrared-triggered photothermal therapy capability and Fe²⁺ -mediated ferroptosis functionality. Meanwhile, the as-prepared FeOOH NSs can light up tumor tissues as a potent MRI contrast agent. Additionally, FeOOH NSs present desirable biosafety in a murine model for up to three months and avoid any long-term toxicity. Furthermore, it is found that these H₂ S-responsible nanotheranostics do not cause any cure effects on other cancer types, such as 4T1 breast cancer. Overall, the findings illustrate that the biocompatible FeOOH NSs can be successfully employed as a theranostic for specifically treating colon cancer, which may promote the clinical translation and development of H₂ S-responsive nanoplatforms.

X-ray and NIR light dual-triggered mesoporous upconversion nanophosphor/Bi heterojunction radiosensitizer for highly efficient tumor ablation

Developing a multi-functional radiosensitizer with high efficiency and low toxicity remains challenging. Herein, we report a mesoporous heterostructure radiosensitizer (UCNP@NBOF-FePc-PFA) containing Lu-based upconversion nanophosphor (UCNP) and Bi-based nanomaterial loaded with iron phthalocyanine for X-ray and NIR light dual-triggered tri-modal tumor therapy. NaLuF₄:Yb,Tm, a Lu-based UCNP, offers radiosensitization and upconversion luminescence for optical bio-imaging. However, Bi has a higher X-ray mass attenuation coefficient than Lu. Thus, after stepwise fabrication, Na_0.2Bi_0.8O_0.35F_1.91:Yb (NBOF) was assembled with the UCNP to form a mesoporous heterostructure composite. This enhanced the radiosensitization effect and drug load to realize multi-modal tumor therapy. After coating it with folate-conjugated amphiphilic PEG (PFA), UCNP@NBOF-FePc-PFA realized tumor photothermal/photodynamic/radio-therapy. The structure of UCNP@NBOF-FePc-PFA was well characterized. Different properties triggered by X-ray and NIR light were evaluated. Finally, a highly efficient tumor ablation effect was demonstrated in vitro and in vivo. Consequently, this kind of nanocomposite provides a unique strategy for designing a theranostic platform for oncotherapy. STATEMENT OF SIGNIFICANCE: The synergy of enhanced radiotherapy and photothermal/photodynamic therapy is found to improve tumor therapeutic efficacy. On that basis, a heterostructure nanohybrid containing Lu-based UCNP and Bi-based mesoporous material is synthesized. The heterostructure nanohybrid can be loaded with FePc and decorated with folate-modified amphiphilic PEG to form a multi-functional theranostic nano-platform. The platform exhibits upconversion luminescence capacity, X-ray attenuation property, photothermal effect, and X-ray and NIR dual-light triggered ROS generation capability. These features can not only enable upconversion luminescence/CT bioimaging of living beings but also be applied to the photothermal/photodynamic/radio- synergistic tumor ablation. To sum up, the nanomaterial offers a novel method for the construction of a new theranostic platform.

Novel Carbon-Based Magnetic Luminescent Nanocomposites for Multimodal Imaging

Multifunctional nanocomposites can combine multiple functions into a single nanosystem and thus have attracted extensive interest in various fields. The combination of magnetic and upconversion luminescent nanoparticles into one single nanoplatform, which have a good application in biomedical fields such as bio-magnetic separation, magnetic resonance imaging (MRI), and optical imaging, is highly desirable. Here we reported multifunctional nanocomposites by using hollow carbon sphere to integrate magnetic Fe₃O₄ and upconversion nanoparticles (UCNPs) into one nanosystem. The as-prepared UCNPs/Fe₃O₄@h-C have near-infrared (NIR) luminescence under 980 nm excitation and superparamagnetism. In addition, since the carbon layer can absorb NIR light and transfer it into heat with high efficiency, the nanocomposites can realize photo thermal (PT), upconversion luminescence (UCL) and MRI tri-mode imaging. The UCNPs/Fe₃O₄@h-C might be further utilized as a potential theranostic agent, including its in-depth monitoring through luminescent imaging and MRI diagnosis, as well as its direct use in tumors as a photothermal therapy (PTT) agent.

Tuning epitaxial growth on NaYbF4 upconversion nanoparticles by strain management

Core-shell structural engineering is a common strategy for tuning upconversion luminescence in lanthanide-doped nanoparticles. However, epitaxial growth on hexagonal phase NaYbF₄ nanoparticles typically suffers from incomplete shell coverage due to the large and anisotropic interfacial strain. Herein, we explore the effects of core particle size and morphology as well as reaction temperature on controlling the epitaxial growth of NaGdF₄ shells on NaYbF₄ nanoparticles with misfit parameters of f_a = 1.58% and f_l = 2.24% for axial and lateral growth, respectively. Rod-like core particles with a long length and a large diameter are found to promote shell growth with high surface coverage by facilitating the relaxation of lattice strains. Furthermore, the primary NaGdF₄ shell can serve as a transition layer to mediate the growth of additional NaNdF₄ coating layers that display an even larger lattice misfit with the core (f_a = 2.98%; f_l = 4.32%). The resultant NaYbF₄@Na(Gd/Nd)F₄ core-shell nanostructures simultaneously show strong multiphoton upconversion luminescence and superior magnetic resonance T₁ ionic relaxivity. Our findings are important for the rational design of core-shell upconversion nanoparticles with optimized properties and functionality for technological applications.