X-ray-activated persistent luminescence nanomaterials for NIR-II imaging

A Novel Afterglow Molecular Probe for Monitoring of pH and Viscosity in Infected Wounds with Two-Dimensional Signal

Organic afterglow materials have shown tremendous potential in the field of biomedical imaging. However, reports on small-molecule afterglow probes, particularly those with multitarget detection capabilities, remain limited. Here, we report a novel afterglow molecule probe (Hcy-Br-SO) that effectively responds to changes in pH and viscosity during wound infection, based on a two-dimensional (2D) signal. In this design, the enhancement of molecular afterglow performance was achieved through molecular engineering, and the underlying mechanism of afterglow emission was derived. Additionally, the synergistic enhancement of the afterglow intensity of Hcy-Br-SO by the increase in the pH and viscosity was confirmed. Besides, we observed that viscosity could retard the photoreaction process, thereby extending the duration of afterglow emission. Based on this phenomenon, we transformed the traditional time-dependent characteristics of afterglow into a measurable parameter for monitoring viscosity changes. It is noteworthy that the introduction of the time dimension not only facilitates the separation of signal sources but also explores the application potential of afterglow molecular probes. To the best of our knowledge, this is the first afterglow small-molecule probe that uses 2D signals (intensity and half-life) to monitor binocular targets. Furthermore, the Hcy-Br-SO probe was successfully used to distinguish between normal and infected wounds. This work may be useful to unravel the pathological mechanisms of chronic wounds and provide guidance for intervention.

An Exploration into the Safe and Precise In Vivo Fluorescence Visualization of Uteroplacental Circulation in the NIR-II Window

The uteroplacental circulation is essential for maintaining normal placental physiology and ensuring fetal development. Imaging this circulation is crucial for a comprehensive understanding of its physiological characteristics and associated pathological processes. Fluorescence imaging in the second near-infrared window (NIR-II, 900-1880 nm) offers significant advantages, including high resolution and deep tissue penetration, facilitating more accurate in vivo assessments. In this study, we employed nanoparticles composed of organic fluorescent dyes with NIR-II emission for precise imaging of the uteroplacental circulation. This approach enabled visualization of the uterine artery and placental blood perfusion in pregnant mice with high resolution. We successfully examined the developmental status across different pregnancy stages and assessed pathological alterations associated with inflammation-induced injury. Furthermore, the maternal and fetal safety of the nanoparticles was validated through comprehensive evaluations. These investigations present a novel approach for studying the formation and development of uteroplacental circulation, as well as related pathological conditions.

Self-Assembly versus Coassembly: An Amphiphilic NIR-II Aggregation-Induced Emission Luminogen for Phototheranostics of Orthotopic Glioblastoma

Glioblastoma (GBM) is the most lethal form of malignant brain tumor, known for its high infiltration, aggressiveness, and poor prognosis. Second near-infrared (NIR-II, 1000-1700 nm) phototheranostic agents bring intriguing opportunities for GBM management owing to their noninvasive nature, controllability, and deeper tissue penetration. Herein, an amphiphilic NIR-II luminogen (PEG-TD) with aggregation-induced emission (AIE) characteristics, along with its hydrophobic counterpart (C6-TD), was meticulously synthesized. Specifically, PEG-TD nanoparticles (NPs), formed through straightforward self-assembly, exhibited superior stability, simplicity, robust reactive oxygen species production efficiency, and excellent photothermal conversion compared to C6-TD NPs, which were fabricated via coassembly with DSPE-mPEG, primarily attributed to the distinct molecular arrangements within the forming aggregates. The inherent advantages of PEG-TD NPs led to significant therapeutic efficacy against GL261 cells under 808 nm laser irradiation. Eventually, NIR-II fluorescence/photothermal duplex imaging-guided combined photodynamic/photothermal therapy was successfully performed in an orthotopic glioblastoma mouse model with minimal adverse effects.

Nonconjugated Structural Distortion Promoting the Formation of NIR Triplet States in Phenothiazine Dyes for Cancer Photoimmunotherapy

Near-infrared (NIR) triplet-state dyes are pivotal for advanced biomedical and material science applications. Although numerous strategies have been proposed to enhance the photosensitization efficiency of dyes, significant challenges remain. Herein, we propose a novel strategy leveraging nonconjugated structural distortion to enhance triplet-state formation. This strategy, achieved by introducing steric groups at the edges of the phenothiazine (PTZ) dye framework, notably enhances intersystem crossing (ISC) and prolongs triplet-state lifetime. Based on this strategy, HNBS and HNBSe are synthesized, which exhibit exceptional triplet-state quantum yields (47.2% for HNBS and 87.7% for HNBSe) and prolonged triplet-excited-state lifetimes (21.1 µs for HNBS and 6.3 µs for HNBSe). These values substantially exceed those of conventional dyes, such as NBS (negligible and NBSe (3.2 µs). Under ultralow-light doses (0.45 J cm- 2 in vitro, and 6 J cm- 2 in vivo), these photosensitizers demonstrate robust tumor cell inhibition, highlighting their exceptional photosensitizing ability. Mechanistically, HNBS possesses lysosomal-targeting ability, and upon light irradiation, it induces lysosomal damage, triggering pyroptosis and immunogenic cell death. These processes promote dendritic cell maturation and T-cell differentiation, augmenting the immune response and enabling effective photoimmunotherapy.

Blue-excited broadband near-infrared emission from zero-dimensional organic-inorganic hybrid metal halides

Luminescent metal halides have garnered significant attention due to their tunable emission characteristics and exceptional optoelectronic properties. Nevertheless, achieving metal halides that exhibit near-infrared (NIR) emission upon blue-light excitation remains a significant challenge. In this study, blue-light-induced NIR emission was successfully realized in the zero-dimensional (0D) (BTP)2ZnBr4:Sb3+ single crystal [BTP+:(3-Bromopropyl) triphenylphosphonium cation] via a straightforward energy transfer from the host (BTP)2ZnBr4 to the self-trapped exciton (STE) state generated by Sb3+. Upon excitation with blue light, (BTP)2ZnBr4:12.5 % Sb3+ exhibits broad NIR emission characterized by a peak at approximately 725 nm, a Stokes shift of about 295 nm, and a notably large full width at half maximum (FWHM) of 179 nm. Additionally, the analysis of experimental data in conjunction with density functional theory (DFT) calculations elucidated the blue light emission mechanism of the host as well as the doped NIR emission. The study demonstrated potential night vision applications by utilizing the (BTP)2ZnBr4:12.5 % Sb3+ phosphor combined with a 430 nm light-emitting diode (LED) chip in the dark.

X-ray-Induced Photodegradation of Hydrogels by the Incorporation of X-ray-Activated Long Persistent Luminescent Nanoparticles

The development of on-demand degradable hydrogels remains an important challenge. Even though photodegradable hydrogels offer spatiotemporal control over degradation, it is difficult to use ultraviolet, visible, or near-infrared light as a tool for noninvasive triggering in vivo due to the poor tissue-penetration capacity. In contrast, X-ray irradiation can penetrate deep tissue and has virtually no penetration limitations for biological soft tissues. In this study, we propose an X-ray-photodegradation cascade system for hydrogel degradation by incorporating X-ray-activated persistent luminescence nanoparticles (X-PLNPs) into photodegradable hydrogels. A photodegradable 9,10-dialkoxyanthracene-based cross-linker was synthesized and used to prepare photodegradable hydrogels, of which the degradation behavior can be triggered by visible green light. Next, Tb3+-doped β-NaLuF4 was introduced as an X-PLNP that can convert X-rays into visible light centered at 544 nm. The afterglow can even be detected for 4 × 103 s after switching off the X-ray irradiation. The X-ray-induced green light emission was demonstrated to trigger photodegradation of the hydrogel. This proof-of-concept system for X-ray irradiation-induced on-demand hydrogel degradation was used to demonstrate X-ray-sensitive drug delivery inside a chicken breast as the in vitro tissue model. As this X-ray-induced cascade degradation of hydrogels can penetrate deep tissues, it is a promising platform for future in vivo applications requiring on-demand triggered hydrogel degradation, such as drug delivery or removal of hydrogel patches, hydrogel adhesives, or hydrogel tissue engineering scaffolds. It should, however, be noted that the hydrogel's X-ray and photoresponsiveness should be further improved to enable future in vivo use.

Advances in Lanthanide-Based NIR-IIb Probes for In Vivo Biomedical Imaging

The past decades have witnessed the significant development and practical interest of in vivo biomedical imaging technologies and optical materials in the second-near infrared (NIR-II, 1000-1700 nm) window. Imaging with the extended emission wavelength toward the long-wavelength end (NIR-IIb, 1500-1700 nm) further offers micrometer imaging resolution and centimeter tissue penetration depth by taking advantage of the much-reduced photon scattering and near-zero tissue autofluorescence background, which have become a very hot research area. This review focuses on the recent advances in the development of lanthanide-based NIR-IIb probes for in vivo biomedical applications. The progress including ratiometric imaging, multiplexed imaging for wide-field and microscopy, lifetime multiplexing and sensing, persistent luminescence, and multimodal imaging is summarized. Challenges and future directions concerning the investigation of the photophysical and photochemical properties of NIR-IIb probes, the selection of near-infrared cameras as well as the potential extension of the NIR-IIb imaging sub-window are pointed out. This review will inspire readers who have a strong interest in developing optical imaging technology and long-wavelength fluorescence probes for high-contrast in vivo biomedical applications.

X-ray-activated nanoscintillators integrated with tumor-associated neutrophils polarization for improved radiotherapy in metastatic colorectal cancer

Radiotherapy, employing high-energy rays to precisely target and eradicate tumor cells, plays a pivotal role in the treatment of various malignancies. Despite its therapeutic potential, the effectiveness of radiotherapy is hindered by the tumor's inherent low radiosensitivity and the immunosuppressive microenvironment. Here we present an innovative approach that integrates peroxynitrite (ONOO-)-mediated radiosensitization with the tumor-associated neutrophils (TANs) polarization for the reversal of immunosuppressive tumor microenvironment (TME), greatly amplifying the potency of radiotherapy. Our design employs X-ray-activated lanthanide-doped scintillators (LNS) in tandem with photosensitive NO precursor to achieve in-situ ONOO- generation. Concurrently, the co-loaded TGF-β inhibitor SB525334, released from the LNS-RS nanoplatform in response to the overexpressed GSH in tumor site, promotes the reprogramming of TANs from N2 phenotype toward N1 phenotype, effectively transforming the tumor-promoting microenvironment into a tumor-inhibiting state. This 'one-two punch' therapy efficiently trigger a robust anti-tumor immune response and exert potent therapeutic effects in orthotopic colorectal cancer and melanoma mouse model. Meanwhile, it also significantly prevents liver metastasis and recurrence in metastatic colorectal cancer. The development of X-ray-controlled platforms capable of activating multiple therapeutic modalities may accelerate the clinical application of radiotherapy-based collaborative therapy.

Non-Invasive Diagnosis of Early Colorectal Cancerization via Amplified Sensing of MicroRNA-21 in NIR-II Window

Accurate, sensitive, and in situ visualization of aberrant expression level of low-abundant biomolecules is crucial for early colorectal cancer (CRC) detection ahead of tumor morphology change. However, the clinical used colonoscopy and biopsy methods are invasive and lack of sensitivity at early-stage of cancerization. Here, an amplified sensing strategy is developed in the second near-infrared long-wavelength subregion (NIR-II-L, 1500-1900 nm) by integrating DNAzyme-triggered signal amplification technology and lanthanide-dye hybrid system. In the early-stage of CRC, the overexpressed biomarker microRNA-21 initiates the NIR-II-L luminescence ratiometric signal amplification of the CRCsensor. The high sensitivity with a limit of detection (LOD) of 1.26 pm allows non-invasive visualization of orthotopic colorectal cancerization via rectal administration, which achieves early and accurate in situ diagnosis at 2 weeks ahead of the in vitro histological results. This innovative approach offers a promising tool for early diagnosis and long-term monitoring of carcinogenesis progression, with potential applications in other cancer-related biomarkers.

Optothermal-Stimulated Persistent Luminescence Imaging and Therapy (OSPLIT)

Persistent luminescent nanomaterials have significantly advanced in vivo bioimaging and biosensing by emitting photons after excitation ceases, effectively minimizing tissue autofluorescence. However, their application in biomedical fields such as tumor theranostics is limited by low brightness and rapid signal decay. To address these issues, OSPLIT (optothermal-stimulated persistent luminescence imaging therapy), a dual-function strategy for imaging and treatment is introduced. The OSPLIT approach enhances the release of charge carriers from deep traps in lanthanide-doped nanoparticles, resulting in a 73 fold increase in persistent luminescence within the second near-infrared (NIR-II) window. In living mice, it enables high-contrast imaging of lymph node metastases, with a signal-to-background ratio 11.8 times greater than conventional NIR-II fluorescence. Optothermal-boosted nanoparticles are effective in ablating lymph node metastasis and preventing tumor spread. These findings highlight the potential of optothermal stimulation to enhance persistent luminescence for both imaging and therapeutic applications.

Thermally activated delayed phosphorescence triggered by charge separation state carrier storage in an organic scintillator

Organic scintillators are among the most promising due to their inherent merits in terms of heavy metal-free constituents, synthesis designability, affordability of raw materials, and low usage costs. However, the limited X-ray excited luminescence (XEL) property of organic scintillators affects their application. To date, the main approaches for improving the XEL property of organic scintillators have focused on introducing heavy atoms to increase the absorbance of X-rays and establishing new luminescence pathways, such as thermally activated delayed fluorescence (TADF), to increase the exciton utilization efficiency. Even so, the XEL property of organic scintillators is not ideal compared with that of commercial inorganic scintillators. In this work, a highly stable charge separation (CS) state trap was introduced into the design of an organic scintillator. Combined with a unique thermally activated delayed phosphorescence (TADP) process, highly efficient capture and conversion of high-energy carriers are realized. As a result, the exciton generation efficiency dramatically increases, with an ultrahigh XEL intensity, and X-ray afterglow imaging at room temperature is achieved for the first time. This work provides a brand-new strategy for the design of high-performance organic scintillators.

Multicolor Rare-Earth Film with Ultra-Long Afterglow for Diverse Energy-Saving Applications

Rare-earth afterglow materials, with their unique light-storage properties, show great promise for diverse applications. However, their broader applicability is constrained by challenges such as poor solvent compatibility, limited luminescent efficiency, and monochromatic emissions. In this study, these limitations are addressed by blending ZnS with various rare-earth phosphors including (Sr0.75Ca0.25)S:Eu2+; SrAl2O4:Eu2+, Dy3+ and Sr2MgSi2O7:Eu2+, Dy3+ to modulate deep trap mechanisms and significantly enhance both the afterglow and light capture capabilities. Using electrospinning, a large-area (0.4 m × 3 m) afterglow film is successfully fabricated with tunable colors and an extended afterglow duration exceeding 30 h. This film demonstrates thermoluminescence, enabling potential integration into fire-rescue protective clothing for enhanced emergency visibility. In greenhouse settings, it effectively supports chlorophyll synthesis and optimizes conditions for plant growth over a 24-h cycle. For tunnel and garage applications, the film captures and stores light from vehicle headlights at distances of up to 70 meters. The scalability and cost-effectiveness of this afterglow film underscore its considerable potential for real-world applications across multiple fields, marking a significant advancement in sustainable illumination technology.

Persistent- and Mechanoluminescence of Er3+-Doped NaYF4 for Multipurpose Use

Advanced functional materials that possess both persistent luminescence (PersL) and mechanoluminescence (ML) have gained considerable attention during the past few years owing to their potential applications in many fields such as two-dimensional stress sensing, energy-saving lighting, and optical bioimaging. However, combined investigation of PersL and ML is still in its infancy. Here, the optical property of Er3+-doped NaYF4, mainly focusing on the PersL and ML characteristic and their correlation, is studied in detail. It is shown that microscaled NaYF4:Er3+ has advantages against nanoscaled counterpart in terms of PersL and ML, consistent with the photoluminescence results. By means of pre-charging and trap-emptying cycle and thermoluminescence test, it is confirmed that the PersL and ML of NaYF4:Er3+ come from the same trapped charge carriers, and the ML belongs to the trap-controlled ML. Furthermore, the good repeatability is proven, and regulation of the PersL and ML of NaYF4:Er3+ is realized. Finally, the potential of NaYF4:Er3+ for dynamic anti-counterfeiting and dual-mode detection of X-ray radiation dose is demonstrated.

Ultrabright and ultrafast afterglow imaging in vivo via nanoparticles made of trianthracene derivatives

Low sensitivity, photobleaching, high-power excitation and long acquisition times constrain the utility of afterglow luminescence. Here we report the design and imaging performance of nanoparticles made of electron-rich trianthracene derivatives that, on excitation by room light at ultralow power (58 μW cm-2), emit afterglow luminescence at ~500 times those of commonly used organic afterglow nanoparticles. The nanoparticles' ultrabright afterglow allowed for deep-tissue imaging (up to 6 cm), for ultrafast afterglow imaging (at short acquisition times down to 0.01 s) of naturally behaving mice with negligible photobleaching, even after re-excitation for over 15 cycles, and for the accurate visualization of subcutaneous and orthotopic tumours and of plaque in carotid arteries. We also show that an afterglow nanoparticle that is activated only in the presence of granzyme B allowed for the tracking of granzyme-B activity in the context of therapeutic monitoring. The high sensitivity and negligible photobleaching of the organic afterglow nanoparticles offer advantages for real-time in vivo monitoring of physiopathological processes.

Endogenous Near-Infrared Chemiluminescence: Imaging-Guided Non-Invasive Thrombolysis and Anti-Inflammation Based on a Heteronuclear Transition Metal Complex

Conventional therapy to treat thrombi (blood clots) has significant limitations: i) inflammation; ii) bleeding side effects; iii) re-embolisation, and iv) in situ thrombi that are not visible. Here it is reported that Cu2Ir nanoparticles (NPs) with a Cu-coordinated tetraphenylporphyrin (TPP) core and cyclometalated Ir(C^N)2(N^N) substituents integrate long-lived near-infrared (NIR) chemiluminescence (CL) imaging, photothermal therapy (PTT) and photodynamic therapy (PDT) for thrombolysis, with antioxidant and anti-inflammatory properties. Based on density functional theory calculations the chemiluminescent reaction site between TPP and peroxynitrite (ONOO-) is confirmed for the first time. The presence of the transition metal significantly improves the chemiluminescent properties of TPP. Upon specific activation by ONOO-, Cu2Ir NPs exhibited more than 30-fold NIR CL intensity than TPP NPs, and the luminescence lasted for 60 min allowing for precise and long-lasting dynamic tracking of thrombi. Cu2Ir NPs achieved non-invasive safe thrombolytic therapy triggered by NIR irradiation at the signaling site. 72.3% blood reperfusion is obtained for nearly complete restoration of blood flow, and re-embolism is prevented in a mouse carotid artery model. Furthermore, Cu2Ir NPs scavenged excess reactive oxygen/nitrogen species (RONS) and reduced inflammatory factors. Cu2Ir NPs hold promise as a single-molecule strategy for diagnosing and treating diseases associated with thrombosis.

Bioengineered nanomaterials for dynamic diagnostics in vivo

In vivo diagnostics obtains real-time physiological information directly from the site of interest in a patient's body, providing more accurate disease diagnosis compared with ex vivo diagnostics. Particularly, in vivo dynamic diagnostics allows the continuous monitoring of physiological signals over a period of time, offering deeper insights into disease pathogenesis and progression. However, achieving in situ dynamic diagnostics in deep tissues presents challenges related to energy and signal penetration as well as dynamic monitoring. Bioengineered nanomaterials serve as an ideal platform for in vivo dynamic diagnostics, leveraging energy conversion and biofunctionalization to enable continuous acquisition of physiological information across temporal and spatial scales. In this review, with reference to the studies from the last five years, we summarize the fundamental components that are essential for dynamic diagnosis in vivo. Firstly, an input energy source with high tissue penetration is needed, such as near-infrared (NIR) light, X-rays, magnetic field and ultrasound. Secondly, a nanomaterial class that is responsive to such an energy source to provide a readable output signal is chosen. Thirdly, bioengineered nanoprobes are designed to exhibit spatial, temporal or spatiotemporal changes in the output signal. Finally, different methods are used to analyse the output signal of nanoprobes, such as detecting changes in optical, radiation, magnetic and ultrasound signals. This review also discusses the obstacles and potential solutions for advancing these bioengineered nanomaterials toward clinical translational applications.

Copper(I) Halide Complex Featuring Blue Thermally Activated Delayed Fluorescence and Aggregate Induced Emission for Efficient X-ray Scintillation and Imaging

Developing solution-processable and stable scintillators with high light yields, low detection limits and high imaging resolutions holds great significance for flexible X-ray imaging. However, attaining an optimal equilibrium among X-ray absorption capacity, exciton utilization efficiency, and decay lifetime of scintillators remains a substantial challenge. Here, a new Cu(I) halide complex was synthesized in a mild condition. It exhibits intense blue thermally activated delayed fluorescence (TADF), remarkable aggregation-induced emission (AIE) characteristic, as well as good water-oxygen stability and photochemical stability. Notably, the complex shows excellent radiation resistance and efficient radioluminescence (RL) with an ultra-low detection limit of 42.5 nGyairs-1. This superior scintillation performance can be attributed to the synergistic effect of effective X-ray absorption by the heavy Cu2I2 core, the high radiation-induced exciton utilization rate in TADF process, and the remarkable suppression of non-radiative transitions by the restriction of intramolecular motions in solid state. Furthermore, the favourable solution processability of the complex facilitates the successful fabrication of a flexible film, achieving high-quality X-ray imaging with a resolution of 17.3 lp mm-1. This work highlights the potential of hybrid Cu(I) halides with AIE-TADF effects for high-energy radiation detection and imaging, opening up new avenues for the exploration of cost-effective and high-performance scintillators.

Radionuclide-Activated Luminescence for Cancer Theranostics

Within dielectric media, charged particles emitted from medical radionuclides induce polarization of surrounding molecules, which subsequently generate Cerenkov luminescence (CL) upon returning to their ground state. This CL emission confers clinically approved radiotracers with distinctive potential for applications in phototheranostics. However, the utility of CL in vivo has been severely constrained by its ultraviolet-weighted emission spectrum and extremely low photon flux, particularly in living imaging and triggering photodynamic therapy. Certain optical probes, encompassing fluorescent agents and nanoparticle scintillators, can be activated by radionuclides to generate red-shifted emissions with amplified luminescence intensity compared to CL. This phenomenon, termed radionuclide-activated luminescence (RL), represents a promising strategy for enhancing radionuclide-induced tumor phototheranostic outcomes. This review systematically summarizes the advances in RL technology, highlighting the development of various RL probes and their innovative applications in laser-free optical bioimaging and cancer phototherapy. It further delves into the confronting challenges and prospects of RL technology, aiming to provide a comprehensive overview and practical insights to advance the integration of radiotheranostics and phototheranostics in clinical practice.

The develop of persistent luminescence nanoparticles with excellent performances in cancer targeted bioimaging and killing: a review

The use of fluorescent nanomaterials in tumor imaging and treatment effectively avoids the original limitations of traditional tumor clinical diagnostic methods. The PLNPs emitted persistent luminescence after the end of excitation light. Owing to their superior optical properties, such as a reduced laser irradiation dose, spontaneous fluorescence interference elimination, and near-infrared imaging, PLNPs show great promise in tumor imaging. Moreover, they also achieve excellent anti-tumor therapeutic effects through surface modification and drug delivery. However, their relatively large size and limited surface modification capacity limit their ability to kill tumors effectively enough for clinical applications. Thus, this article reviews the synthesis and modification of PLNPs and the research progress in targeted tumor imaging and tumor killing. We also discuss the challenges and prospects of their future applications in these fields. This review has value for accelerating the design of PLNPs based platform for cancer diagnosis and treatment.

Enabling Persistent Luminescence of Eu3+ in Nanoparticles through Interfacial Energy Transfer for Advanced X-ray Imaging

Persistent luminescence (PersL) emerged recently in nanoparticles which greatly promotes and expands their frontier applications. However, achieving X-ray-activated PersL of Eu3+ in fluoride nanoparticles has remained a huge challenge. Here, we propose a conceptual model to realize this aim by constructing the interfacial energy transfer in a core-shell nanostructure. We show that the terbium sublattice is a good sensitizer to absorb X-ray energy and activate Eu3+ in the shell with its resultant intense PersL. A gradual color change from red to yellow and green is achieved by a fine manipulation of interfacial interactions between Tb3+ and Eu3+. Moreover, the presence of Eu3+ in the Tb lattice annihilates the PersL of Tb3+ with only its radioluminescence, being helpful to avoid ghost imaging. Our findings gain a deep insight into the PersL mechanism in nanoparticles, which help design new classes of PersL materials and provide new possibilities for advanced flexible imaging applications.

Probing structural defects and X-ray induced persistent luminescence mechanisms on rare earth-doped strontium sulfide materials

Persistent luminescence is related to the existence of point defects in the crystal structure, which can be induced by the insertion of dopant ions to create trap levels for charge carriers. Strontium sulfide (SrS) is a promising host for X-ray activated phosphors due to its high luminescence yield and X-ray absorption efficiency. While the mechanisms of UV- and visible light-induced luminescence in rare-earth doped SrS have been previously explored, this work focuses on understanding X-ray induced mechanisms using synchrotron radiation techniques. Extended X-ray absorption fine structure (EXAFS) analysis suggested that rare-earth ions incorporate into the SrS lattice primarily as substitutional defects, with structural distortions depending on the differences in ionic radii between Sr2+ and RE2+/3+. X-ray absorption near edge structure (XANES) spectra revealed the mixed-valence nature of Ce in SrS:Ce and SrS:Eu,Ce materials, and also that X-ray irradiation triggers complex charge transfer processes. The X-ray excited optical luminescence (XEOL) results showed that co-doped samples exhibited longer persistent luminescence decay times than their single-doped counterparts due to the increased number of defects. These findings provide new insights into the interplay between crystal defects and persistent luminescence in X-ray-activated phosphors, contributing to the design of more efficient materials for applications such as medical imaging, optical information storage, and industrial sensing.

Modulation of Near-Infrared Afterglow Luminescence in Inorganic Nanomaterials for Biological Applications

Near-infrared afterglow luminescent inorganic nanomaterials (NIR-ALINs) possess the unique property of continuing to emit near-infrared (NIR) luminescence after excitation ceases. They demonstrate excellent photostability, deep tissue penetration, and high imaging signal-to-noise ratio (SNR). Additionally, NIR-ALINs can be re-excited in vivo using visible (Vis), NIR light or X-rays, which avoids the need for continuous in situ excitation, thus eliminating autofluorescence of biological tissues and reducing the tediousness of multiple injections. These features make NIR-ALINs particularly attractive for biological applications. In recent years, a series of NIR-ALINs with prolonged afterglow time and enhanced luminescence intensity have been discovered. However, the development of NIR-ALINs still faces significant challenges, as their NIR afterglow performance is usually insufficient to satisfy practical biological applications. There is still a lack of systematic analysis of the strategies for the regulation of NIR afterglow luminescence in inorganic nanomaterials. This review highlights the rational design and modulation strategies of NIR-ALINs, focusing on host substrate selection, trap engineering modulation and surface modification. Moreover, the biological applications of NIR-ALINs in bioimaging, bio-detection and disease therapy are summarized. Finally, the present challenges and perspectives in biological applications, such as insufficient afterglow properties and unclear biosafety, are also discussed.

PhotoChem Interplays: Lighting the Way for Drug Delivery and Diagnosis

Light, a non-invasive tool integrated with cutting-edge nanotechnologies, has driven transformative advancements in imaging-based diagnosis and drug delivery for cancer and bacterial treatments. This review discusses recent progress in these areas, beginning with emerging imaging technologies. Unlike traditional photosensors activated by visible light, alternative energy sources such as near-infrared (NIR) light, X-rays, and ultrasound have been extensively investigated to activate various photosensors, achieving high sensitivity, wavelength versatility, and spatial resolution for deep-tissue imaging. Moreover, to address challenges like tissue autofluorescence in real-time fluorescence imaging, afterglow luminescent nanoparticles are being developed by integrating these alternative energy sources for real-time imaging and sensing in deep tissue for precise cancer diagnosis and treatment beyond superficial tissues. In addition to deep tissue imaging, light-responsive nanomedicines are revolutionizing anticancer and antimicrobial phototherapy by enabling spatially and temporally controlled drug release. These smart nanoparticles are engineered to release therapeutic cargo at target sites in response to microenvironmental cues specific to tumors or infections. In anticancer phototherapy, these nanoparticles facilitate controlled drug release via photoisomerization, photothermal, and photodynamic processes. To enhance circulation time and specific targeting, biomimetic nanoparticles, which mimic natural anti-tumor responses by our body, have attracted increasing attention. In antimicrobial phototherapy, research has been focused on the chemical modification of the photosensitizer to enable targeted drug delivery. An intriguing strategy has recently emerged involving the development of "pro-photosensitizers" that are specifically activated within bacterial cells upon light irradiation, offering a high margin of safety. These advancements leverage photochemical reactions and nanotechnology to enhance precision therapy and diagnosis in addressing critical health challenges.

EBNA1 Targeted Ultra-Small Near-Infrared Persistent Luminescent Nano-Inhibitor for Theranostics of EBV-Associated Cancer

Epstein-Barr virus (EBV) is a well-recognized oncogenic virus that promotes several lymphoid and epithelial cancers. The Epstein-Barr nuclear antigen 1 (EBNA1), which is known to be expressed in all EBV-positive cancers, plays a vital role in viral genome replication and maintenance and is therefore emerged as an attractive target for clinical intervention. Several EBNA1 inhibitors have shown potency in the growth inhibition of EBV-positive cancers, yet low bioavailability and in vivo unmonitored nature hamper their further implementation. Here a novel EBNA1 nano-inhibitor based on EBNA1-specific peptide inhibitor (P4) functionalized ZnGa2O4:Cr3+ ultra-small near-infrared persistent luminescent (NIR-PL) nanoparticles (ZGOC-P4) is developed. Owing to the specific binding to EBNA1, ZGOC-P4 nano-inhibitor can quickly achieve nuclear internalization in EBV-positive nasopharyngeal carcinoma (NPC) cells (C666-1) and selectively inhibit their growth. In sharp contrast, ZGOC-P4 nano-inhibitor shows no inhibition effect on EBV-negative NPC cells (HK-1). Moreover, the results indicate that the well-designed nano-inhibitor enables efficient tumor-targeting accumulation in NPC xenograft model under the monitoring of autofluorescence interference-free NIR-PL imaging in vivo and suppresses EBV-associated tumor growth with an inhibition rate of 61.6%. This work highlights the potency of ZGOC-P4 on NPC treatment and may provide new sight into future research on EBV-associated diseases.

Ultrabright difuranfluoreno-dithiophen polymers for enhanced afterglow imaging of atherosclerotic plaques

Cardiovascular diseases, including stroke driven by atherosclerosis, remain a leading global health concern. Current diagnostic imaging modalities such as magnetic resonance imaging fail to characterize oxidative stress within atherosclerotic plaques. Here, we introduce difuranfluoreno-dithiophen-based polymers designed for afterglow imaging, offering ultrabright luminescence, ultralow-power excitation (0.087 milliwatts per square centimeter), and ultrashort acquisition times (0.01 seconds). Through a molecular engineering strategy, we have optimized polymers for enhanced reactive oxygen species (ROS) generation capability, ROS capturing capability, and fluorescence quantum yield, resulting in an increase in afterglow intensity (~130-fold) compared to commonly used 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene polymer (MEHPPV). Additionally, we have developed ratiometric afterglow nanoparticles doped with oxidative stress-responsive molecules, enabling imaging of oxidative stress markers in atherosclerotic plaque. This approach provides a tool for cardiovascular imaging and diagnostics, which is conducive to the auxiliary diagnosis and risk stratification of atherosclerosis.

Strong Persistent Luminescence NaYF4-based Nanoparticles Combined with Manipulated Hyperfractionated Irradiation for X-ray-Excited Photodynamic Therapy Enhancement

X-ray-excited photodynamic therapy (X-PDT), a novel synergistic therapy combining radiotherapy (RT) with photodynamic therapy (PDT), demonstrates not only more effective therapeutic outcomes but also overcomes the limitation of PDT's shallow penetration depth. Persistent luminescence nanoparticles (PLNPs) have been employed in X-PDT due to their unique afterglow emission, which yields more light to achieve more effective PDT outcomes using the same irradiation dose. However, at present, persistent luminescent materials used in X-PDT are mainly bulk crystals characterized by a nonuniform size and morphology, which are not suitable for biomedical applications, and the presence of excessive surface defects reduces the luminescence efficiency and the persistent luminescence duration. Herein, the NaYF4:Tb@NaYF4 core-shell nanoparticles with enhanced luminescence and afterglow performance and uniform morphology were prepared via the optimized solvothermal method. Their X-ray excitation optical luminescence (XEOL) and persistent luminescence (XEPL) intensities were enhanced more than 5.2 times and 3.5 times, respectively. The PLNPs were modified with a water-soluble AEP ligand and piggybacked with the photosensitizer Rose Bengal (RB) to construct an efficient X-PDT nanocoupling system. To fully utilize the afterglow of PLNPs, a unique hyperfractionated irradiation plan was designed, and the ROS yield was increased by nearly 50% at the same irradiation dose. In vivo therapeutic efficacy validation using the B16-F10-bearing C57 mouse model demonstrated that hyperfractionated irradiation combined with PLNPs showed significant therapeutic advantages. At a total dose of 2 Gy, the tumor inhibition rate was enhanced from 67.5% to 85% compared to the conventional irradiation strategy. Pathological analysis showed no significant histological damage in major organs, attesting to its negligible side effects. This study offers a novel modality, with both nanoparticles and irradiation strategy improvement, to further improve the X-PDT therapeutic efficacy and reduce side effects.

Doped magnetic nanoparticles: From synthesis to applied technological frontiers

Doped magnetic nanoparticles (DMNPs) have become a fascinating class of nanomaterials with important implications in science and technology. The comprehensive review focuses on the synthetic methods, types of doping elements, distinctive properties, and extensive applications of DMNPs. The synthesis section highlights different methods, highlighting their benefits and drawbacks, such as chemical precipitation, co-precipitation, thermal breakdown, sol-gel, and other processes. Strategies for increasing the stability and functioning of DMNP are also reviewed, including surface functionalization and ligand exchange. An in-depth study is done to clarify how doping materials including transition metals, non-metals, and rare earth elements affect the chemical stability and magnetic characteristics of DMNP. Applications in various fields, such as biomedicine (MRI contrast agents, medication transport, antibacterial activity), environmental remediation (water purification, heavy metal removal), and sensing technologies, heavily rely on these features. DMNPs offer much potential in a variety of disciplines. Still, there are several challenges to their adoption, including regulatory and safety concerns, cost-effectiveness issues, and scalability issues. More research is required to overcome these difficulties and maximize the use of MDNPs for ensuring food safety.

Luminescent Lanthanides in Biorelated Applications: From Molecules to Nanoparticles and Diagnostic Probes to Therapeutics

Lanthanides are particularly effective in their clinical applications in magnetic resonance imaging and diagnostic assays. They have open-shell 4f electrons that give rise to characteristic narrow, line-like emission which is unique from other fluorescent probes in biological systems. Lanthanide luminescence signal offers selection of detection pathways based on the choice of the ion from the visible to the near-infrared with long luminescence lifetimes that lend themselves to time-resolved measurements for optical multiplexing detection schemes and novel bioimaging applications. The delivery of lanthanide agents in cells allows localized bioresponsive activity for novel therapies. Detection in the near-infrared region of the spectrum coupled with technological advances in microscopies opens new avenues for deep-tissue imaging and surgical interventions. This review focuses on the different ways in which lanthanide luminescence can be exploited in nucleic acid and enzyme detection, anion recognition, cellular imaging, tissue imaging, and photoinduced therapeutic applications. We have focused on the hierarchy of designs that include luminescent lanthanides as probes in biology considering coordination complexes, multimetallic lanthanide systems to metal-organic frameworks and nanoparticles highlighting the different strategies in downshifting, and upconversion revealing some of the opportunities and challenges that offer potential for further development in the field.

Design strategies and biomedical applications of organic NIR-IIb fluorophores

The introduction of fluorescence imaging (FLI) in near-infrared II sub-channels (NIR-IIb, 1500-1700 nm) has revolutionized the ability to explore complex patho-physiological settings in vivo. Despite the transformative potentials, the development of organic NIR IIb dyes encounters considerable difficulties, and only a limited number of such fluorophores have been developed so far. This review systematically introduces design strategies of organic NIR-IIb fluorophores classified by molecular scaffolds, mainly including cyanine dyes and D-A-D small molecule dyes. The design strategies of cyanine dyes involve repurposing of the existing NIR dyes, conjugate reinforcement and regulation of the aggregation state. For D-A-D small molecule dyes, strategies mainly incorporate the extension of the conjugate skeleton, introduction of shielding units, and acceptor/donor engineering. We further describe recent biomedical applications including biomedical imaging and imaging-guided therapy, and conclude by clarifying the current challenges and prospects of NIR-IIb FLI.

Amplifying Persistent Luminescence in Heavily Doped Nanopearls for Bioimaging and Solar-to-Chemical Synthesis

Lanthanides are widely codoped in persistent luminescence phosphors (PLPs) to elevate defect concentration and enhance luminescence efficiency. However, the deleterious cross-relaxation between activators and lanthanides inevitably quenches persistent luminescence, particularly in heavily doped phosphors. Herein, we report a core-shell engineering strategy to minimize the unwanted cross-relaxation but retain the charge trapping capacity of heavily doped persistent luminescence phosphors by confining the activators and lanthanides in the core and shell, respectively. As a proof of concept, we prepared a series of codoped ZnGa2O4:Cr, Ln (CD-Ln, Ln = Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) and core-shell structured ZnGa2O4:Cr@ZnGa2O4:Ln (CS-Ln) nanoparticles. First-principles investigations suggested that lanthanide doping elevated the electron trap concentration for enhancing persistent luminescence, but energy transfer (ET) from Cr3+ to Ln3+ ions quenched the persistent luminescence. The spatial separation of Cr3+ and Ln3+ ions in the core-shell structured CS-Ln nanoparticles suppressed the ET from Cr3+ to Ln3+. Due to the efficient suppression of deleterious ET, the optimal doping concentration of Ln in CS-Ln was elevated 50 times compared to CD-Ln. Moreover, the persistent luminescence intensity of CS-5%Ln was up to 60 times that of the original ZnGa2O4:Cr. The CS-5%Ln displayed significantly improved signal-to-noise ratios in bioimaging. Further, the CS-Ln was interfaced with the lycopene-producing bacteria Rhodopseudomonas palustris for solar-to-chemical synthesis, and the lycopene productivity was increased by 190%. This work provides a reliable solution to fulfill the potential of lanthanides in enhancing persistent luminescence and can further promote the applications of persistent luminescence phosphors in biomedicine and solar-to-chemical synthesis.

Dual-Ligand Assisted Anisotropic Assembly for the Construction of NIR-II Light-Propelled Mesoporous Nanomotors

The advent of autonomous nanomotors presents exciting opportunities for nanodrug delivery. However, significant potential remains for enhancing the asymmetry of nanomotors and advancing the development of second near-infrared (NIR-II) light-propelled nanomotors capable of operating within deep tissues. Herein, we developed a dual-ligand assisted anisotropic assembly strategy that enables precise regulation of the interfacial energy between selenium (Se) nanoparticle and periodic mesoporous organosilica (PMO). This strategy facilitates the controllable anisotropic growth of PMO on the Se nanoparticle, leading to the formation of Se&PMO Janus nanohybrids. The exposure ratio of the Se subunit within the Janus nanohybrids can be finely tuned from 0% to 75%. Leveraging the transformability of the Se subunit, a variety of functional MxSe&PMO Janus nanocomposites (MxSe denotes metal selenide) were further derived. As a proof of concept, CuSe&PMO Janus nanohybrids, with NIR-II photothermal properties, were employed as NIR-II light-driven nanomotors. By precisely controlling the exposure ratio of the CuSe subunit within the Janus nanostructure, these CuSe&PMO nanomotors achieved optimal self-propulsion, thus enhancing cellular uptake and promoting deep tumor penetration. Furthermore, the high loading capacity and hydrophobic framework of the PMO subunit enabled the incorporation of hydrophobic disulfiram, thereby significantly boosting the efficacy of synergistic active-motion photothermal therapy.

Recent advances and design strategies for organic afterglow agents to enhance autofluorescence-free imaging performance

Long-lasting afterglow luminescence imaging that detects photons slowly being released from chemical defects has emerged, eliminating the need for real-time photoexcitation and enabling autofluorescence-free in vivo imaging with high signal-to-background ratios (SBRs). Organic afterglow nano-systems are notable for their tunability and design versatility. However, challenges such as unsatisfactory afterglow intensity, short emission wavelengths, limited activatable strategies, and shallow tissue penetration depth hinder their widespread biomedical applications and clinical translation. Such contradiction between promising prospects and insufficient properties has spurred researchers' efforts to improve afterglow performance. In this review, we briefly outline the general composition and mechanisms of organic afterglow luminescence, with a focus on design strategies and an in-depth understanding of the structure-property relationship to advance afterglow luminescence imaging. Furthermore, pending issues and future perspectives are discussed.

Bio-Inspired Multiple Responsive NIR II Nanophosphors for Reversible and Environment-Interactive Information Encryption

Inspired by the natural responsive phenomena, herein the multiple responsive persistent luminescent Zn1.2Ga1.6Ge0.2O4:Ni2+ (ZGGO:Ni) nanoparticles with near-infrared  (NIR) II emission peak ≈1330 nm derived from the Ni2+ doping through controlled synthesis based on hydrothermal method are obtained. The obtained NIR II persistent luminescent ZGGO:Ni can not only respond to temperature but also the specific solvent stimulus. The results demonstrate that the NIR II persistent luminescence intensity decreases in hydroxyl containing solvent such as water (H2O) and ethyl alcohol (C2H6O), while the PL intensity remains in solvent without hydroxyl groups such as n-hexane (C6H14) and deuterated water (D2O). This NIR II luminescence quenching is attributed to the adsorption of interaction hydroxyl groups in specific solvents with the amino group on the surface of ZGGO:Ni and the subsequent fluorescence resonance energy transfer mechanism. Benefiting from the multiple responsive properties, the obtained NIR II persistent luminescent ZGGO:Ni is utilized for high-order dynamic optical information encryption, providing increased security level. The multi-responsive NIR II persistent luminescence strategy outlined in this study is anticipated to offer a straightforward methodology for optimizing the optical characteristics of NIR II persistent luminescent materials. Moreover, it is set to expand the scope of their applications in the realm of dynamic and environment-interactive information encryption, thereby opening frontiers for their utilization in advanced security measures.

Activatable red/near-infrared aqueous organic phosphorescence probes for improved time-resolved bioimaging

Organic red/near-infrared (NIR) room-temperature phosphorescence (RTP) holds significant potential for autofluorescence-free bioimaging and biosensing due to its prolonged persistent luminescence and exceptional penetrability. However, achieving activatable red/NIR organic RTP probes with tunable emission in aqueous solution remains a formidable challenge. Here we report on aqueous organic RTP probes with red/NIR phosphorescence intensity and lifetime amplification. These probes consist of supramolecular assemblies comprising macrocyclic cucurbit[8]uril and amine-containing alkyl-bridged pyridiniums, exhibiting viscosity-activatable phosphorescence with enhanced quantum yield (≤20%) and lifetime. Notably, by utilizing this activatable organic RTP probe, we successfully achieve two-photon imaging of lysosomal viscosity and millisecond-scale time-resolved cell imaging. Moreover, intravital phosphorescence imaging by using an RTP probe enables the monitoring of viscosity variations in inflammatory mice, demonstrating a significantly improved signal-to-background ratio compared with fluorescence imaging. This activatable red/NIR supramolecular platform facilitates versatile high-resolution phosphorescence imaging for in vivo tracking of specific biomarkers and physiological events.

A cascade X-ray energy converting approach toward radio-afterglow cancer theranostics

Leveraging X-rays to initiate prolonged luminescence (radio-afterglow) and stimulate radiodynamic 1O2 production from optical agents provides opportunities for diagnosis and therapy at tissue depths inaccessible to light. However, X-ray-responsive organic luminescent materials are rare due to their intrinsic low X-ray conversion efficiency. Here we report a cascade X-ray energy converting approach to develop organic radio-afterglow nanoprobes (RANPs) for cancer theranostics. RANPs comprise a radiowave absorber that down-converts X-ray energy to emit radioluminescence, which is transferred to a radiosensitizer to produce singlet oxygen (1O2). 1O2 then reacts with a radio-afterglow substrate to generate an active intermediate that simultaneously decomposes to emit radio-afterglow. Through finetuning such a cascade, intraparticle radioluminescence energy transfer and the 1O2 transfer process, RANPs possess tunable wavelengths and long half-lives, and generate radio-afterglow and 1O2 at tissue depths of up to 15 cm. Moreover, we developed a biomarker-activatable nanoprobe (tRANP) that produces a tumour-specific radio-afterglow signal, leading to ultrasensitive detection and the possibility of surgical removal of diminutive tumours (1 mm3) under an X-ray dosage 20 times lower than inorganic materials. The efficient radiodynamic 1O2 generation of tRANP permits complete tumour eradication at an X-ray dosage lower than clinical radiotherapy and a drug dosage one to two orders of magnitude lower than most existing inorganic agents, leading to prolonged survival rates with minimized radiation-related adverse effects. Thus, our work reveals a generic approach to address the lack of organic radiotheranostic materials and provides molecular design towards precision cancer radiotherapy.

High Defect Tolerance Breaking the Design Limitation of Full-Spectrum Multimodal Luminescence Materials

With the development of optical anti-counterfeiting and the increasing demand for high-level information encryption, multimodal luminescence (MML) materials attract much attention. However, the discovery of these multifunctional materials is very accidental, and the versatile host suitable for developing such materials remains unclear. Here, a grossite-type fast ionic conductor CaGa4O7, characterized by layered and tunnel structure with excellent defect tolerance, is found to meet the needs of various luminescent processes. Almost all luminescent modes, including down/up-conversion luminescence (DCL/UCL), long persistent luminescence (LPL), mechanoluminescence (ML), and X-ray excited optical luminescence (XEOL), are realized in this single host. Full-spectrum (from violet to near-infrared) photoluminescence and ML as well as multicolor XEOL are achieved by simply changing the doped luminescent center. A series of anti-counterfeiting devices, including the quasi-dynamic display of famous paintings, digital information encryption, and multi-color handwritten signatures, are designed to show the encryption of information in temporal and spatial dimensions. This study clarifies the importance of defect tolerance of the host for the development of MML materials, and provides a unique insight into the cross-field applications of special functional materials, which is a new strategy to accelerate the development of novel MML materials.

Broadband Near-Infrared Fibers Derived from Nanocrystal-Glass Composites for Miniature Arrays Light Sources

Broadband near-infrared (NIR) fiber arrays are highly desirable for multiplexed fluorescence endoscopic, however, there is a challenge for the development of miniature light sources with highly efficient broadband NIR emissions. Here the synthesis of a MgAl2O4:Cr3+ nanocrystal-glass composite (NGC) with an Cr3+-clusters-induced broadband NIR emission possessing is presented and external quantum efficiency of 44% and a full width at half maximum of 297 nm, and the NGC fiber is further fabricated through a template solidification strategy, resulting in the construction of an all-fiber coupling system by fusing them with commercial quartz fiber that achieves an optical coupling efficiency of 95.2%. Furthermore, these NGC fibers are regularly arranged into fiber bundle as an array light source to enhance NIR luminescence and imaging ability, and the fluorescence imaging of 4 mm biological tissue penetration is realized, as well as the multiplexed fluorescence imaging, under the irradiation of the NIR fiber bundle. This study provides general and efficient fiber fabrication guidelines toward NIR array light sources, opening the new routes for fluorescence endoscopes.

Spatial confinement growth of high-performance persistent luminescence nanoparticles for image-guided sonodynamic therapy

Near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) have significant potential in diagnostic and therapeutic applications owing to their unique persistent luminescence (PersL). However, obtaining high-performance NIR PLNPs remains challenging because of the limitations of current synthesis methods. Herein, we introduce a spatial confinement growth strategy for synthesizing high-performance NIR PLNPs using hollow mesoporous silica (hmSiO2). By calcining precursor ions in the hollow cavity, the yolk size of NIR PLNPs was regulated, yielding well-dispersed Zn1.3Ga1.4Sn0.3O4: Cr0.005, Y0.003@hmSiO2 (ZS) with a yolk-shell structure. Compared to the conventional template method, ZS synthesized via the spatial confinement growth strategy exhibited a 7.7-fold increase in PersL intensity and a threefold increase in specific surface area. As a proof of concept, ZS@PpIX@CaP-AMD (ZPSC-AMD) nanoparticles, with potential for sonodynamic therapy (SDT), were synthesized by loading the sonosensitizer protoporphyrin IX (PpIX) into ZS, coating it with a calcium phosphate (CaP) shell, and modifying it with a tumor-targeting molecule plerixafor (AMD-3100). The tumor enrichment behavior of ZPSC-AMD was monitored by sensitive NIR PersL to guide SDT. Simultaneously, ZPSC-AMD enabled the precise monitoring of tumor accumulation, thereby guiding effective SDT. In addition, Ca2+ released from CaP degradation increased the level of reactive oxygen species during SDT, promoting tumor cell apoptosis. This study outlines a reliable design and synthesis approach for high-performance NIR PLNPs and promotes their development in biomedical applications. STATEMENT OF SIGNIFICANCE: The potential of near infrared (NIR) persistent luminescence nanoparticles (PLNPs) in bio applications is hindered by limitations in the synthesis method. In this article, we proposed a spatial confinement growth strategy of high-performance NIR PLNPs. The obtained PLNPs with yolk-shell structure showed a 7.7-fold increase in PersL intensity and a threefold increase in specific surface area, compared with the commonly used template method. Due to the advantages, sonodynamic therapeutic nanoparticles were constructed based on the above PLNPs, where persistent luminescence was used for ultrasensitive imaging to determine the optimal timing in sonodynamic therapy. In addition, the multifunctional calcium phosphate shell elevated the intracellular reactive oxygen species level to promote tumor cell apoptosis.

Molecular Engineering of Direct Activated NIR-II Chemiluminescence Platform for In Vivo Chemiluminescence-fluorescence Duplex Imaging

Chemiluminescence (CL) is a self-illuminating phenomenon fueled by chemical energy instead of extra excited light, which features superiority in sensitivity, signal-to-background ratios, and imaging depth. Strategies to synthesize a CL emission unimolecular skeleton in the second near-infrared window (NIR-II) and a unimolecular probe with direct duplex NIR-II [CL/fluorescence (FL)] emission are lacking. Here, we employ modular synthesis routes to construct a series of directly activated NIR-II CL emission unimolecular probes with a maximum emission wavelength of up to 1060 nm, and use them for real-time and continuous detection of the superoxide anion generated in acetaminophen induced liver injury in a female mice model under both NIR-II CL and NIR-II FL imaging channels. Thus, this study establishes a directly activatable NIR-II CL emission unimolecular skeleton, validating the scalability of this duplex NIR-II CL/FL imaging platform in bioactive molecule detection and disease diagnosis.

Advancements in nanotechnology for diagnostics: a literature review, part II: advanced techniques in nuclear and optical imaging

Modern molecular imaging routes, such as nuclear imaging and optical imaging, derive significant advantages from nanoparticles, where multimodality use and multipurpose are key benefits. Nanoparticles also showcase benefits over traditional imaging agents in nuclear and optical imaging, including improved resolution, penetration, and specificity. The goal of this literature review was to explore recent advancements in nanomaterials within these molecular imaging techniques to expand on the current state of nanomedicine in these modalities. This review derives findings from relevant reviews, original research papers, in-human clinical trials, and patents in the literature. Au- and Fe oxide-based nanosystems are just as ubiquitous within more modern modalities due to their multimodal diagnostic and therapeutic potential. It is also repeatedly highlighted in the literature, patents, and clinical trials that the use of nanoparticles, specifically in multimodal imaging techniques and theranostics, present innovative methods in recent years, enabling researchers and clinicians to overcome the limitations of unimodal imaging modalities and further advancing accuracy in the diagnosis and treatment of important pathologies, particularly cancer. Overall, nanoparticle-based imaging represents a transformative approach in advanced imaging modalities, offering new approaches to limitations of conventional agents currently being applied in clinical settings.

Recent Advances in NIR or X-ray Excited Persistent Luminescent Materials for Deep Bioimaging

Due to their persistent luminescence, persistent luminescent (PersL) materials have attracted great interest. In the biomedical field, the use of persistent luminescent nanoparticles (PLNPs) eliminates the need for continuous in situ excitation, thereby avoiding interference from tissue autofluorescence and significantly improving the signal-to-noise ratio (SNR). Although persistent luminescence materials can emit light continuously, the luminescence intensity of small-sized nanoparticles in vivo decays quickly. Early persistent luminescent nanoparticles were mostly excited by ultraviolet (UV) or visible light and were administered for imaging purposes through ex vivo charging followed by injection into the body. Limited by the low in vivo penetration depth, UV light cannot secondary charge PLNPs that have decayed in vivo, and visible light does not penetrate deep enough to reach deep tissues, which greatly limits the imaging time of persistent luminescent materials. In order to address this issue, the development of PLNPs that can be activated by light sources with superior tissue penetration capabilities is essential. Near-infrared (NIR) light and X-rays are widely recognized as ideal excitation sources, making persistent luminescent materials stimulated by these two sources a prominent area of research in recent years. This review describes NIR and X-ray excitable persistent luminescence materials and their recent advances in bioimaging.

Tm3+-Based Downshifting Nanoprobes with Enhanced Luminescence at 1680 nm for In Vivo Vascular Growth Monitoring

Optical imaging in the 1500-1700 nm region, known as near-infrared IIb (NIR-IIb), shows potential for noninvasive in vivo detection owing to its ultrahigh tissue penetration depth and spatiotemporal resolution. Rare earth-doped nanoparticles have emerged as widely used NIR-IIb probes because of their excellent optical properties. However, their downshifting emissions rarely exhibit sufficient brightness beyond 1600 nm. This study presents tetragonal-phase thulium-doped nanoparticles (Tm3+-NPs) with core-shell-shell structures (CSS, LiYbF4:3%Tm@LiYbF4@LiYF4) that exhibit bright downshifting luminescence at 1680 nm. Enhanced luminescence is attributed to (1) the promoted nonradiative relaxation between the doping ions and (2) the maximized sensitization process. Additionally, this strategy was validated for NIR-IIb luminescence enhancement of erbium (Er3+)-doped NPs. After surface modification with PEGylated liposomes, tetragonal-phase Tm3+-NPs exhibited a prolonged blood cycle time, high colloidal stability, and good biocompatibility. Owing to the advantages of Tm3+-based probes in NIR-IIb imaging, in vivo thrombus detection and monitoring of angiogenesis and arteriogenesis were successfully performed in a mouse model of ischemic hind limbs.

pH-Responsive Persistent Luminescent Nanosystem with Sensitized NIR Imaging and Ratiometric Imaging Modes for Tumor Surgery Navigation

Owing to autofluorescence-free feature, persistent luminescent (PersL) nanoparticles (PLNPs) become potential materials for tumor surgical navigation. However, it is still challenging to enhance PersL intensity, contrast ratio, and imaging stability so as to meet clinical demand and avoid missed detection of microlesions. Herein, integrating a tumor microenvironment (TME)-responsive strategy, sensitization enhancement, and internal-standard ratiometric method, a dual-mode PersL imaging strategy is proposed: After loading pH-responsive fluorescent molecule Rh-ADM on PLNPs ZnGa2O4:Cr3+,Mn2+ (ZGCM-Rh8), the fluorescence resonance energy transfer (FRET) pathways between Cr3+ and Rh-ADM, as well as Mn2+ and Rh-ADM, could sensitize the NIR PersL emitted by Cr3+ and quench the green PersL from Mn2+ at acidic TME, respectively. As a result, ZGCM-Rh8 is endowed with WLED (white light LED)-excited NIR imaging mode and UV-excited ratiometric imaging mode. Under WLED, ZGCM-Rh8 realizes 4.5-fold PersL enhancement and 97.9 as the maximum tumor contrast after precise control of Rh-ADM contents, helping with the preoperative diagnosis of deep lesions. Under UV, ZGCM-Rh8 conducts ratiometric PersL imaging steadily, and the "NIR/Vis" ratios at the tumor keep larger than 110, succeeding in detecting out a 1.5 mm small lesion and serving thorough surgical elimination of H22 ectopic intramuscular tumor in balb/c mice. To our knowledge, ZGCM-Rh8 is the first to realize pH-responsive PersL sensitization and apply ratiometric PersL imaging technology to surgical navigation.

NIR-II Imaging for Tracking the Spatiotemporal Immune Microenvironment in Atherosclerotic Plaques

The inflammatory immune microenvironment is responsible for atherosclerotic plaque erosion and rupture. Near-infrared-II (NIR-II) fluorescence imaging has the potential to continuously monitor the spatiotemporal changes in the plaque immune microenvironment. Herein, we constructed three different NIR-II probes based on benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole-4,7-bis(9,9-dioctyl-9H-fluoren-2-yl)thiophene (denoted as BBT-2FT): VHPK/BBT-2FT NPs, where VHPK is a specific peptide targeting vascular cell adhesion molecule-1; iNOS/BBT-2FT NPs for modulating the polarization of M1 macrophages by inducible NO synthase (iNOS) antibodies; and Arg-1/BBT-2FT for counterbalancing the inflammatory responses of M1 macrophages. These tracers enable precise tracking of atherosclerotic plaques and M1 and M2 macrophages through NIR-II imaging. VHPK/BBT-2FT NPs can accurately trace atherosclerotic plaques at various stages. Arg-1/BBT-2FT NPs precisely located M2 macrophages in the early plaque microenvironment with upregulation of peroxisome proliferator-activated receptor γ (PPAR-γ), signal transducer and activator of transcription (STAT) 6, and ATP-binding cassette transporter A1 (ABCA1), indicating that M2 macrophage polarization is crucial for early plaque lipid clearance. Meanwhile, iNOS/BBT-2FT NPs accurately tracked M1 macrophages in the advanced plaque microenvironment. The results showed that M1 macrophage polarization induces the formation of an inflammatory microenvironment through anaerobic glycolytic metabolism and pyroptosis in the advanced hypoxic plaque microenvironment, as indicated by the upregulation of hypoxia-inducible factor 1 alpha (HIF-1α), STAT1, NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3), pyruvate dehydrogenase kinase 1 (PDK1), and glucose transporter 1 (GLUT-1). Combining immunological approaches with NIR-II imaging has revealed that hypoxia-induced metabolic reprogramming of macrophages is a key factor in dynamic changes in the immune microenvironment of atherosclerotic plaques. Furthermore, our strategy shows the potential for real-time diagnosis and clinical prevention of unstable plaque rupture in atherosclerosis.

Shortening the early diagnostic window of Hg2+-induced liver injury with a H2O2-activated fluorescence/afterglow imaging assay

Mercury ions (Hg2+) and mercury derivatives are a serious threat to ecosystems and human health due to their toxicity, and their toxicological effects are associated with a burst of reactive oxygen species (ROS) due to the oxidative stress. Endogenous hydrogen peroxide (H2O2), a featured ROS in vivo, plays an irreplaceable role in a significant number of pathological processes. However, the exact bioeffect role that H2O2 plays in Hg2+-induced oxidative stress in a specific disease has not been well answered. In particular, optical imaging probes for H2O2 endowed with afterglow emission properties are very rare. Here, the first fluorescence/afterglow probe (FA-H2O2) for accurate and specific detection of H2O2 in cells, zebrafish, and mice under Hg2+-induced oxidative stress is reported. Moreover, FA-H2O2 in its afterglow emission enables efficient monitoring of endogenous H2O2 with a higher signal-to-noise ratio (SNR) in comparison to its fluorescence signals. More importantly, by virtue of the merits of afterglow emission that can eliminate autofluorescence, thus for the first time, shortening the diagnostic window of Hg2+-induced liver injury with FA-H2O2 via noninvasive afterglow emission tracking of H2O2 is achieved, which definitely provides a new opportunity and promising tool for early diagnosis of Hg2+-induced liver injury.

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

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

Single-Atom Iridium Nanozyme-Based Persistent Luminescence Nanoparticles for Multimodal Imaging-Guided Combination Tumor Therapy

Persistent luminescence nanoparticles (PLNPs) can achieve autofluorescence-free afterglow imaging, while near-infrared (NIR) emission realizes deep tissue imaging. Nanozymes integrate the merits of nanomaterials and enzyme-mimicking activities with simple preparation. Here PLNPs are prepared of Zn1.2Ga1.6Ge0.2O4:Cr0.0075 with NIR emission at 700 nm. The PLNPs are then incubated with IrCl3 solution, and the nanoparticles are collected and annealed at 750 °C to obtain iridium@PLNPs. Iridium is observed on the PLNPs at the atomic level as a single-atom nanozyme with peroxidase-like catalytic activity, photothermal conversion, and computed tomography (CT) contrast capability. After coating with exosome membrane (EM), the Ir@PLNPs@EM composite exhibits long-lasting NIR luminescence, peroxidase-like catalytic activity, photothermal conversion, and CT contrast capability, with the targeting capability and biocompatibility from EM. Thus, NIR afterglow/photothermal/CT trimodal imaging-guided photothermal-chemodynamic combination therapy is realized as validated with the in vitro and in vivo inhibition of tumor growth, while toxicity and side effects are avoided as drug-free treatment. This work offers a promising avenue for advanced single-atom nanozyme@PLNPs to promote the development of nanozymes and PLNPs for clinical applications.

ZGSO:Cr3+,Ni2+ Persistent Phosphors with Dual Emission in NIR-I and SWIR Ranges for Bio-Imaging Applications

Persistent luminescence (PersL) is widely used for near infrared (NIR-I, 650-950 nm) imaging as they allow getting images without background. Bio-imaging in the second shortwave-infrared region SWIR-II (NIR-II, 1000-1400 nm) is less widespread but is growing as it offers the advantages of low photon scattering, increased in vivo penetration depth, and improved imaging clarity. In this work, the preparation and the complete optical properties of a new material is reported, Zn1.33Ga1.33Ni0.005Cr0.005Sn0.33O3.995 (ZGSO:Cr3+, Ni2+) able of emitting in both deep-red/NIR-I and SWIR (NIR-II) and shows its potential in bioimaging. ZGSO:Cr3+, Ni2+ can be excited using different sources such as X-rays, UV, and visible light to emit persistent signals in dual biological windows (dual-BW). By integrating an energy transfer process from Cr3+ to Ni2+ within this newly synthesized material, the influence of co-dopants on signal intensity and emission wavelengths is sought to explore. PersL at ≈700 nm (NIR-I) and ≈1300 nm (NIR-II) have been tested in preliminary bioimaging experiments using different protocols, allowing signal detection with good spatial resolution and depth sensitivity. The dual-BW PersL imaging strategy expands the toolbox for highly accurate analysis and has, for the first time, allowed access to accurately high-resolution sensing, and tracing.

NIR-II Orthogonal Fluorescent Ratiometric Nanoprobe for In Situ Bioimaging of Carbon Monoxide

Carbon monoxide (CO) functions as a significant endogenous cell signaling molecule and is strongly associated with many physiological and pathological processes. However, conventional fluorescence imaging in the visible and near-infrared (NIR) I regions suffers autofluorescence background and photon scattering, hindering the accurate detection of CO in vivo. In addition, the complexity of physiological environments leads to fluctuating fluorescence emission. To solve these problems, herein, the NIR-II fluorescent nanoprobe NP-Pd for in vivo ratiometric bioimaging of CO is developed. In the presence of CO, NP-Pd exhibits responsive enhancement in absorption at 808 nm, which amplifies the fluorescence signal of down-conversion nanoparticles (DCNP) at 1060 nm under 808 nm excitation, while the fluorescence signal of DCNP at 1525 nm under 980 nm excitation remains unchanged and serves as an internal standard. Through this orthogonally ratiometric fluorescence strategy, accurate CO bioimaging and precise diagnosis of acute liver injury diseases are achieved in the mouse model experiments, providing a novel tool for the in vivo detection of CO-related diseases.

Advances in the Development of Gradient Scaffolds Made of Nano-Micromaterials for Musculoskeletal Tissue Regeneration

The intricate hierarchical structure of musculoskeletal tissues, including bone and interface tissues, necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes. This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes. Building on the anatomical characteristics of bone and interfacial tissues, this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues, specifically focusing on methods used to construct compositional and structural gradients within the scaffolds. The latest applications of gradient scaffolds for the regeneration of bone, osteochondral, and tendon-to-bone interfaces are presented. Furthermore, the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed, as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.