A high performance Sc-based nanoprobe for through-skull fluorescence imaging of brain vessels beyond 1500 nm

Less Is More: Donor Engineering of a Stable Molecular Dye for Bioimaging in the NIR-IIb Window

Fluorescence molecular imaging aims to enhance clarity in the region of interest, particularly in the near-infrared IIb window (NIR-IIb, 1500-1700 nm). To achieve this, we developed a novel small-molecule dye, named DA-5, based on classic cyanine dyes (heptamethine or pentamethine is essential for wavelengths beyond 1000 nm). By reducing excessive polymethine to a single methine and disrupting symmetry to form an asymmetric donor-π-acceptor (D-π-A) architecture, we enhanced the donor's electron-donating capability, yielding emission at 1088 nm. DA-5 exhibits superior properties, including excellent chemo- and photostability, resistance against solvatochromism-caused quenching, and antiaggregation in aqueous solution. With a large Stokes shift (241 nm) and high brightness (321 M-1 cm-1), DA-5 enables high-performance imaging of the lymphatic system, intestinal vessels, whole-body angiography, and cerebral and hindlimb microvasculature in NIR-IIb. This molecular design strategy offers a promising platform for advancing in vivo biophotonics.

Rational Design of NIR-II Ratiometric Fluorescence Probes for Accurate Bioimaging and Biosensing In Vivo

Intravital fluorescence imaging in the second near-infrared window (NIR-II, 900-1700 nm) has emerged as a promising method for non-invasive diagnostics in complex biological systems due to its advantages of less background interference, high tissue penetration depth, high imaging contrast, and sensitivity. However, traditional NIR-II fluorescence imaging, which is characterized by the "always on" or "turn on" mode, lacks the ability of quantitative detection, leading to low reproducibility and reliability during bio-detection. In contrast, NIR-II ratiometric fluorescence imaging can realize quantitative and reliable analysis and detection in vivo by providing reference signals for fluorescence correction, generating new opportunities and prospects during in vivo bioimaging and biosensing. In this review, the current design strategies and sensing mechanisms of NIR-II ratiometric fluorescence probes for bioimaging and biosensing applications are systematically summarized. Further, current challenges, future perspectives and opportunities for designing NIR-II ratiometric fluorescence probes are also discussed. It is hoped that this review can provide effective guidance for the design of NIR-II ratiometric fluorescence probes and promote its adoption in reliable biological imaging and sensing in vivo.

Synthesis on NIR-II Multifunctional Imaging and Photothermal Therapy of a Novel Water-Soluble Molecule

The synthesis of water-soluble symmetric molecules with donor-acceptor-donor (D-A-D) structure is reported. The compound is connected by π bridge with 2-bromofluorene external polyethylene glycol 2000 as the shielding unit, and donor component and pyrrolopyrrole (DPP) as the acceptor unit. The D-A-D double donor fluorescent molecule P2-DPP is obtained by coupling reaction. The absorption peak and emission peak of the fluorescent molecule P2-DPP are 600 and 1020 nm, respectively. It has potential excellent imaging characteristics. It does not need to use nanoparticles formed by the DSPE-MPEG amphiphilic block to form micelles. The quantum yield reaches 0.6% and the penetration depth can reach 10 mm. The chemical is capable of achieving liver and renal metabolism. It has a good application prospect in the photothermal therapy of mouse tumors and realizes the integration of biological diagnosis and treatment.

Preparation of rare earth-doped nano-fluorescent materials in the second near-infrared region and their application in biological imaging

Second near-infrared (NIR-II) fluorescence imaging (FLI) has gained widespread interest in the biomedical field because of its advantages of high sensitivity and high penetration depth. In particular, rare earth-doped nanoprobes (RENPs) have shown completely different physical and chemical properties from macroscopic substances owing to their unique size and structure. This paper reviews the synthesis methods and types of RENPs for NIR-II imaging, focusing on new methods to enhance the luminous intensity of RENPs and multi-band imaging and multi-mode imaging of RENPs in biological applications. This review also presents an overview of the challenges and future development prospects based on RENPs in NIR-II regional bioimaging.

Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region

In vivo imaging technologies have emerged as a powerful tool for both fundamental research and clinical practice. In particular, luminescence imaging in the tissue-transparent near-infrared (NIR, 700-1700 nm) region offers tremendous potential for visualizing biological architectures and pathophysiological events in living subjects with deep tissue penetration and high imaging contrast owing to the reduced light-tissue interactions of absorption, scattering, and autofluorescence. The distinctive quantum effects of nanocrystals have been harnessed to achieve exceptional photophysical properties, establishing them as a promising category of luminescent probes. In this comprehensive review, the interactions between light and biological tissues, as well as the advantages of NIR light for in vivo luminescence imaging, are initially elaborated. Subsequently, we focus on achieving deep tissue penetration and improved imaging contrast by optimizing the performance of nanocrystal fluorophores. The ingenious design strategies of NIR nanocrystal probes are discussed, along with their respective biomedical applications in versatile in vivo luminescence imaging modalities. Finally, thought-provoking reflections on the challenges and prospects for future clinical translation of nanocrystal-based in vivo luminescence imaging in the NIR region are wisely provided.

Fabrication of tumor targeting rare-earth nanocrystals for real-time NIR-IIb fluorescence imaging-guided breast cancer precise surgery

The near-infrared fluorescence imaging has been integrated into the operating room to guide tumor resection, potentially reducing the positive margin rates in breast-conserving surgery (BCS). Relative to the widely used first near-infrared fluorescence imaging, imaging in the second near-infrared (NIR-II) region possesses higher contrast and deeper tissue penetration, particularly in the NIR-IIb window, offering many new opportunities for imaging-guided BCS. Here, we fabricated the c(RGDfC) functionalized erbium-based rare-earth nanoparticles (ErNPs@cRGD) with superior optical property in NIR-IIb region. Owing to deeper tissue penetration and efficient tumor targeting, ErNPs@cRGD-based NIR-IIb fluorescence imaging achieved enhanced signal-to-background ratios in tumor visualization, which was able to guide more complete tumor resection, identify multiple microtumors and distinguish malignant lesions from normal tissues in various mice models. Based on these, this NIR-IIb imaging strategy for surgical navigation can significantly reduce positive margin rates and improve prognosis, laying a foundation for the clinical resection of breast cancer.

PDA modified NIR-II NaEr0.8Yb0.2F4nanoparticles with high photothermal effect

Polydopamine (PDA)-modified NaEr_0.8Yb_{0.2 F4}nanoparticles were synthesized, with strong NIR-II emission, quantum yield of 29.63%, and excellent photothermal performance. Crystal phases and microstructures are characterized. Optical properties such as absorption, NIR-II emission, and light stability are studied, and the luminescence mechanism is discussed in detail. Key factors in NIR-II imaging were evaluated in fresh pork tissue, including penetration depth, spatial resolution, and signal-to-noise ratio (SNR). A high penetration depth of 5 mm and a high spatial resolution of 1 mm were detected. Mice are imaged in vivo afterintravenousinjection. Due to the accumulation of nanoparticles in the liver, high image quality with an SNR of 5.2 was detected in the abdomen of KM mice with hair. The photothermal conversion effect of PDA-modified NPs was twice that of the reported material. These NIR-II nanoparticles have superior optical properties, high photothermal efficiency and low cytotoxicity, and are potential fluorescent probes for further disease diagnosis and treatment.

Rare-earth based materials: an effective toolbox for brain imaging, therapy, monitoring and neuromodulation

Brain diseases, including tumors and neurodegenerative disorders, are among the most serious health problems. Non-invasively high-resolution imaging methods are required to gain anatomical structures and information of the brain. In addition, efficient diagnosis technology is also needed to treat brain disease. Rare-earth based materials possess unique optical properties, superior magnetism, and high X-ray absorption abilities, enabling high-resolution imaging of the brain through magnetic resonance imaging, computed tomography imaging, and fluorescence imaging technologies. In addition, rare-earth based materials can be used to detect, treat, and regulate of brain diseases through fine modulation of their structures and functions. Importantly, rare-earth based materials coupled with biomolecules such as antibodies, peptides, and drugs can overcome the blood-brain barrier and be used for targeted treatment. Herein, this review highlights the rational design and application of rare-earth based materials in brain imaging, therapy, monitoring, and neuromodulation. Furthermore, the development prospect of rare-earth based materials is briefly introduced.

Rare earth nanoparticles for sprayed and intravenous NIR II imaging and photodynamic therapy of tongue cancer

In this research, rare earth nanoparticles coupled with dihydroartemisinin (DHA) and a targeted antibody (RENP-DHA-Cap) for sprayed NIR II imaging and photodynamic therapy (PDT) of tongue cancer were designed. Genetic algorithms combined with combinatorial chemistry were proposed and successfully achieved in a single optimized luminescent phosphor with enhanced NIR II and high upconversion luminescence (UCL) under a NIR laser of wavelength 980 nm or/and 808 nm. In particular, T1 magnetic resonance imaging (MRI) signals can be adjusted with the Gd ion concentration. In combination with the targeted antibody of capmatinib (Cap), precise NIR II imaging for in situ tongue cancer by a simple spray method can be achieved. Most importantly, NIR II imaging and PDT treatment can be realized with RENP-DHA-capmatinib injected intravenously. This orthogonal theranostic mode with precise diagnosis under 808 nm and targeted effective treatment under 980 nm may promote tongue cancer theranostics.

Expanding the toolbox of photon upconversion for emerging frontier applications

Photon upconversion in lanthanide-based materials has recently shown compelling advantages in a wide range of fields due to their exceptional anti-Stokes luminescence performances and physicochemical properties. In particular, the latest breakthroughs in the optical manipulation of photon upconversion, such as the precise tuning of switchable emission profiles and lifetimes, open up new opportunities for diverse frontier applications from biological imaging to therapy, nanophotonics and three-dimensional displays. A summary and discussion on the recent progress can provide new insights into the fundamental understanding of luminescence mechanisms and also help to inspire new upconversion concepts and promote their frontier applications. Herein, we present a review on the state-of-the-art progress of lanthanide-based upconversion materials, focusing on the newly emerging approaches to the smart control of upconversion in aspects of light intensity, colors, and lifetimes, as well as new concepts. The emerging scientific and technological discoveries based on the well-designed upconversion materials are highlighted and discussed, along with the challenges and future perspectives. This review will contribute to the understanding of the fundamental research of photon upconversion and further promote the development of new classes of efficient upconversion materials towards diversities of frontier applications in the future.

Dual-molecular targeted NIR II probe with enhanced response for head and neck squamous cell carcinoma imaging

In this research, a fluorescent probe of 7-(diethylamine) coumarin derivatives with multiple binding sites to detect biothiols in tumor cell with strong NIR II luminescencein vivowas synthesized. The biothiols include cysteine (Cys) and glutathione (GSH) in tumor cells, and the tumor-response luminescence was proved by the cell experiment. Importantly, the monolayer functional phospholipid (DSPE-PEG) coating and aggregation induced emission (AIE) dye of TPE modification made the probe have good stability and biocompatibility with little luminescence quenching in aqueous phase, which was proved byin vitroandin vivoexperiments. The final aqueous NIR II probe combined with bevacizumab (for VEGF recognition in the cancer cells) and Capmatinib (for Met protein recognition in the cancer cells) has stronger targeted imaging on head and neck squamous cell carcinoma (HNSCC) cancer with intravenous injection. This GSH/Cys detection in the tumor cell and strong dual-molecular NIR II bioimagingin vivomay provide new strategy to tumor detection.

Synergistic strategy of rare-earth doped nanoparticles for NIR-II biomedical imaging

Featuring simultaneous multicolor imaging for multiple targets, a synergistic strategy has become promising for fluorescence imaging applications. Visible and first near infrared (NIR-I, 700-900 nm) fluorophores have been explored for multicolor imaging to achieve good multi-target capacity, but they are largely hampered by the narrow imaging bands available (400-900 nm, bandwidth 500 nm), the broad emission spectra of many fluorophores, shallow tissue penetration and scattering loss. With attractive characteristic emission peaks in the second NIR window (NIR-II, 1000-1700 nm), a narrow emission spectrum, and deeper tissue penetration capability, rare-earth doped nanoparticles (RENPs) have been considered by us to be outstanding candidates for multicolor bioimaging. Herein, two RENPs, NaYF4:Yb20Er2@NaYF4 and NaYF4:Nd5@NaYF4, were prepared and modified with polyethylene glycol (PEG) to explore simultaneous imaging in the NIR-IIb (1530 nm, under 980 nm laser excitation) and the NIR-II (1060 nm, under 808 nm laser excitation) windows. The PEGylated-RENPs (RENPs@PEG) were able to simultaneously visualize the circulatory system, trace the lymphatic system, and evaluate the skeletal system. Our study demonstrates that RENPs have high synergistic imaging capability in multifunctional biomedical applications using their NIR-II fluorescence. Importantly, the two RENPs@PEG are complementary to each other for higher temporal resolution in NaYF4:Nd5@NaYF4@PEG and higher spatial resolution in NaYF4:Yb20Er2@NaYF4@PEG, which may provide more comprehensive and accurate imaging diagnosis. In conclusion, RENPs are highly promising nanomaterials for multicolor imaging in the NIR-II window.

Versatile Types of Inorganic/Organic NIR-IIa/IIb Fluorophores: From Strategic Design toward Molecular Imaging and Theranostics

In vivo imaging in the second near-infrared window (NIR-II, 1000-1700 nm), which enables us to look deeply into living subjects, is producing marvelous opportunities for biomedical research and clinical applications. Very recently, there has been an upsurge of interdisciplinary studies focusing on developing versatile types of inorganic/organic fluorophores that can be used for noninvasive NIR-IIa/IIb imaging (NIR-IIa, 1300-1400 nm; NIR-IIb, 1500-1700 nm) with near-zero tissue autofluorescence and deeper tissue penetration. This review provides an overview of the reports published to date on the design, properties, molecular imaging, and theranostics of inorganic/organic NIR-IIa/IIb fluorophores. First, we summarize the design concepts of the up-to-date functional NIR-IIa/IIb biomaterials, in the order of single-walled carbon nanotubes (SWCNTs), quantum dots (QDs), rare-earth-doped nanoparticles (RENPs), and organic fluorophores (OFs). Then, these novel imaging modalities and versatile biomedical applications brought by these superior fluorescent properties are reviewed. Finally, challenges and perspectives for future clinical translation, aiming at boosting the clinical application progress of NIR-IIa and NIR-IIb imaging technology are highlighted.

Second near-infrared (NIR-II) imaging: a novel diagnostic technique for brain diseases

Imaging in the second near-infrared II (NIR-II) window, a kind of biomedical imaging technology with characteristics of high sensitivity, high resolution, and real-time imaging, is commonly used in the diagnosis of brain diseases. Compared with the conventional visible light (400-750 nm) and NIR-I (750-900 nm) imaging, the NIR-II has a longer wavelength of 1000-1700 nm. Notably, the superiorities of NIR-II can minimize the light scattering and autofluorescence of biological tissue with the depth of brain tissue penetration up to 7.4 mm. Herein, we summarized the main principles of NIR-II in animal models of traumatic brain injury, cerebrovascular visualization, brain tumor, inflammation, and stroke. Simultaneously, we encapsulated the in vivo process of NIR-II probes and their in vivo and in vitro toxic effects. We further dissected its limitations and following optimization measures.

Er3+ self-sensitized nanoprobes with enhanced 1525 nm downshifting emission for NIR-IIb in vivo bio-imaging

Traditional sensitizer (Yb³⁺ or Nd³⁺) and activator (Er³⁺) co-doped lanthanide-based nanoprobes possessing emission of Er³⁺ at 1525 nm have attracted much attention in NIR-IIb bio-imaging. However, the 1525 nm fluorescence efficiency was not high enough in such co-doped systems due to the serious back energy transfer from the activator to the sensitizer, resulting in a lot of excitation energy loss. Herein, we have designed an efficient NIR-IIb nanoprobe Er³⁺ self-sensitized NaErF₄:0.5%Tm³⁺@NaLuF₄, where substantially all the excitation energy could contribute to Er³⁺ ions and most energy transfer processes were confined among Er³⁺ ions, avoiding the energy dissipation by heterogeneous sensitizer ions. The influence of the types of epitaxial heterogeneous shells, the doping effect and optimal doping concentration of Tm³⁺ ions, as well as the critical shell thickness for obtaining the surface quenching-assisted downshifting emission are systematically investigated to acquire the most efficient 1525 nm luminescence under 800 nm excitation. The quantum yield in the 1500-1700 nm region reached 13.92%, enabling high-resolution through-skull cerebrovascular microscopy imaging and large-depth in vivo physiological dynamic imaging with an extremely low excitation powder density of 35 mW cm^-2. The designed nanoprobe can be potentially used for brain science research and clinical diagnosis.

Incorporation of Planar Blocks into Twisted Skeletons: Boosting Brightness of Fluorophores for Bioimaging beyond 1500 Nanometer

The brightness of organic fluorescence materials determines their resolution and sensitivity in fluorescence display and detection. However, strategies to effectively enhance the brightness are still scarce. Conventional planar π-conjugated molecules display excellent photophysical properties as isolated species but suffer from aggregation-caused quenching effect when aggregated owing to the cofacial π-π interactions. In contrast, twisted molecules show high photoluminescence quantum yield (Φ_PL) in aggregate while at the cost of absorption due to the breakage in conjugation. Therefore, it is challenging to integrate the strong absorption and high solid-state Φ_PL, which are two main indicators of brightness, into one molecule. Herein, we propose a molecular design strategy to boost the brightness through the incorporation of planar blocks into twisted skeletons. As a proof-of-concept, twisted small-molecule TT3-oCB with larger π-conjugated dithieno[3,2-b:2',3'-d]thiophene unit displays superb brightness at the NIR-IIb (1500-1700 nm) than that of TT1-oCB and TT2-oCB with smaller thiophene and thienothiophene unit, respectively. Whole-body angiography using TT3-oCB nanoparticles presents an apparent vessel width of 0.29 mm. Improved NIR-IIb image resolution is achieved for femoral vessels with an apparent width of only 0.04 mm. High-magnification through-skull microscopic NIR-IIb imaging of cerebral vasculature gives an apparent width of ∼3.3 μm. Moreover, the deeply located internal organ such as bladder is identified with high clarity. The present molecular design philosophy embodies a platform for further development of in vivo bioimaging.

Novel small-molecule fluorophores for in vivo NIR-IIa and NIR-IIb imaging

Near-infrared fluorescence imaging in the 1000-1700 nm-wavelength window (NIR-II) has exhibited great potential for deep-tissue bioimaging due to its diminished auto-fluorescence, suppressed photo-scattering, deep penetration, and high spatial and temporal resolutions. Various kinds of inorganic nanomaterials have been extensively developed for NIR-IIa (1300-1400 nm) and NIR-IIb (1500-1700 nm) bioimaging. However, the development of small-molecule NIR-IIa and NIR-IIb fluorophores is still in its infancy. Herein, we designed and synthesized a novel NIR-II organic aggregation-induced emission (AIE) fluorophore (HQL2) with a fluorescence tail extending into the NIR-IIa and NIR-IIb region based on our previous reported skeleton Q4. The encapsulated NIR-II AIE nanoparticles (HQL2 dots) exhibited water solubility and biocompatibility, and high brightness for NIR-IIa and NIR-IIb vascular imaging in vivo, a first for NIR-II AIE dots.

Synthesis and optical properties of a Y3(Al/Ga)5O12:Ce3+,Cr3+,Nd3+ persistent luminescence nanophosphor: a promising near-infrared-II nanoprobe for biological applications

Persistent luminescence nanophosphors (PLNPs) emitting in the second near-infrared window (1000-1700 nm, NIR-II) are emerging as one promising class of in vivo bio-imaging agents due to their unique advantages including non-autofluorescence and low optical scattering in tissues. Currently, it remains a great challenge to synthesize nanosized lanthanide-doped inorganic NIR-II phosphors with a good persistent luminescence performance. Herein, we present a salt microemulsion method for synthesizing Ce³⁺, Cr³⁺, Nd³⁺ codoped Y₃(Al/Ga)₅O₁₂ nanocrystals, which generate multi-wavelength persistent luminescence in the visible (∼508 nm, 5d₁→ 4f of Ce³⁺), the first near-infrared window (∼890 nm, ⁴F_3/2→⁴I_9/2 of Nd³⁺) and NIR-II (∼1063 nm, ⁴F_3/2→⁴I_11/2 of Nd³⁺) regions. Under illumination of a 410 nm diode (3 W) for 10 min, the observed duration time of NIR-II persistent luminescence is as long as 60 min at room temperature. Moreover, the persistent luminescence can be excited efficiently by multiple excitation sources including a blue diode, white LEDs and an X-ray generator, which is crucial for deep tissue imaging applications. By comparing the penetration depth between NIR-I and NIR-II persistent luminescence through chicken breast, we prove that NIR-II photons exhibit a deeper optical penetration length (3.9 mm) than that of the NIR-I ones (2.5 mm). In addition, the NIR signals can still be detected 3 min after ceasing the excitation source by a small animal imaging system (InGaAs detector) when the thickness of the covering chicken breast is 20 mm. These results show great promise for Y₃(Al/Ga)₅O₁₂:Ce³⁺,Cr³⁺,Nd³⁺ nanocrystals as a PLNP for bio-imaging applications with deep penetration depth and a high signal-to-noise ratio.

Recent Advances in Rare-Earth-Doped Nanoparticles for NIR-II Imaging and Cancer Theranostics

Fluorescence imaging in the second near infrared window (NIR-II, 1,000-1,700 nm) has been widely used in cancer diagnosis and treatment due to its high spatial resolution and deep tissue penetration depths. In this work, recent advances in rare-earth-doped nanoparticles (RENPs)-a novel kind of NIR-II nanoprobes-are presented. The main focus of this study is on the modification of RENPs and their applications in NIR-II in vitro and in vivo imaging and cancer theranostics. Finally, the perspectives and challenges of NIR-II RENPs are discussed.

A general strategy for designing NIR-II emissive silk for the in vivo monitoring of an implanted stent model beyond 1500 nm

Silk fibroin-based materials spun by silkworms present excellent biocompatible and biodegradable properties, endowing them with broad applications for use in in vivo implanted devices. Therefore, it is highly desirable to explore functionalized silk with additional optical bioimaging abilities for the direct in situ monitoring of the status of implanted devices in vivo. Herein, a new type of silk material with a second near-infrared (NIR-II, 1000-1700 nm) emission is explored for the real-time observation of a biological stent model using a general route of feeding larval silkworms with lanthanide-based NaYF₄:Gd³⁺/Yb³⁺/Er³⁺@SiO₂ nanocrystals. After being fed lanthanide nanocrystals, the silk spun by silkworms shows efficient NIR-II emission beyond 1500 nm. Moreover, NIR-II bio-imaging guided biological stent model monitoring presents a superior signal-to-noise (S/N) ratio compared to the traditional optical imaging by utilizing the upconversion (UC) region. These findings open up the possibility of designing NIR-II optically functionalized silk materials for highly sensitive and deep-tissue monitoring of the in vivo states of the implanted devices.

Small molecular interaction-based fluorescence enhancement for second near-infrared imaging

Aim: This study described a new strategy to enhance second near-infrared (NIR-II) fluorescence intensity. Materials & methods: NIR-II liposomes were prepared by thin film hydration method and their fluorescence properties were evaluated. The efficacy of the optimized liposome was then evaluated in vivo with low dose and irradiation. Results: Indocyanine green-IR1061 liposome exhibited higher fluorescence intensity (∼fourfold than IR1061 liposome) with the red-shifted emission. The intensity of indocyanine green-IR1061 cationic liposome was enhanced to approximately tenfold, which allowed us to perform angiography with lower doses and less exposure time. Conclusion: We report a new and efficient way to enhance NIR-II fluorescence intensity. This could be used to acquire high temporal resolution and signal-to-background ratio fluorescence imaging.

An Sc-based coordination polymer with concaved superstructures: preparation, formation mechanism, conversion, and their electrochemistry properties

Scandium-based coordination polymer octahedrons with concaved surfaces have been fabricated. The formation mechanism was also investigated. Sc₂O₃ octahedrons were obtained after simple calcination in a N₂ atmosphere.

Novel NIR-II organic fluorophores for bioimaging beyond 1550 nm

Novel NIR-II organic fluorophores were designed and synthesized using an AIE and highly twisted donor–acceptor distortion strategy for bio-imaging beyond 1550 nm.

One-pot synthesis of SiO2-coated Gd2(WO4)3:Yb3+/Ho3+ nanoparticles for simultaneous multi-imaging, temperature sensing and tumor inhibition

Rare earth ion-doped fluoride upconversion nanoparticles (UCNPs), emerging as a novel class of probes and drug carriers, exhibit superior promise for bio-applications in diagnostics and treatment on account of their strong luminescence, fine biocompatibility, and high drug loading. However, the fine control and manipulation of particle size and the distribution of rare earth ion-doped oxides has remained an insurmountable challenge to date. In this work, we construct and synthesize silica-coated Gd2(WO4)3:Yb3+/Ho3+ nanoparticles by one-pot co-precipitation, with uniform distribution (∼130 nm) and enhanced yellow fluorescence. Particularly, the nanoparticles not only possess outstanding temperature sensing performance at biological temperatures in water by utilizing the fluorescence intensity ratio (FIR) method, but also allow a further serviceable contrast effect in vitro and in vivo based on the prominent T1-weighted magnetic resonance (MR) signal of Gd3+. Compared with cisplatin and platinum(iv) (DSP), the Gd2(WO4)3@SiO2 nanoparticles functionalized with DSP (Gd2(WO4)3@SiO2-Pt-PEG) exert higher lethality against CT26 cells and significantly inhibit the growth of tumors at the same concentration of Pt. This effect occurs through the greater level of cell endocytosis. The lethality value of the latter is 10 times higher than the former after the same length of time according to inductively coupled plasma-mass spectrometry (ICP-MS) results. In short, the monodisperse and strongly fluorescent Gd2(WO4)3@SiO2-Pt-PEG nanoparticles are endowed with dual-mode imaging, temperature sensing and anticancer functions, which provide a significant guide for synthesis and bio-application of lanthanide ion-doped oxides.

Noninvasive and real-time pharmacokinetics imaging of polymeric nanoagents in the thoracoepigastric vein networks of living mice

Noninvasive and real-time visualization of the thoracoepigastric veins (TVs) of living mice was demonstrated by using two-photon excitation (TPE) optical imaging with a Eu-luminescent polymeric nanoagent as the angiographic contrast. The spatiotemporal evolution of the polymeric nanoagent in TVs was monitored for up to 2 h by TPE time-resolved (TPE-TR) bioimaging, which is free from the interference of tissue autofluorescence. A wide field-of-view covering the thoracoabdominal region allowed the visualization of the entire TV network with an imaging depth of 1 to 2 mm and a lateral resolution of 80 μm at submillimeter. Detailed analysis of the uptake, transport, and clearance processes of the polymeric nanoagent revealed a clearance time constant of ∼30  min and an apparent clearance efficiency of 80% to 90% for the nanoagent in both axial and lateral TVs. TPE-TR imaging of the dissected internal organs proved that the liver is mainly responsible for the sequestration of the nanoagent, which is consistent with the apparent retention efficiency of liver, ∼32  %  , as determined by the real-time in vivo TV imaging. We demonstrate the potency of TPE-TR modality in the pharmacokinetics imaging of the peripheral vascular systems of animal models, which can be beneficial for related nanotheranostics study.

A broad-range temperature sensor dependent on the magnetic and optical properties of SrF2:Yb3+, Ho3+

Co-doped SrF₂: Yb³⁺, Ho³⁺ nanoparticles (NPs) have been successfully synthesized and upconversion luminescence (UCL) was demonstrated under excitation at 980 nm.

Multifunctional BiF3:Ln3+ (Ln = Ho, Er, Tm)/Yb3+ nanoparticles: an investigation on the emission color tuning, thermosensitivity, and bioimaging

Pure cubic phase and uniform BiF₃:Ln³⁺ (Ln = Ho, Er, Tm)/Yb³⁺ nanoparticles (NPs) were prepared by coprecipitation. The growth mechanism of BiF₃:2%Er³⁺/20%Yb³⁺ NPs was proposed based on evolution analysis of the time-dependent morphology, in which BiF₃:2%Er³⁺/20%Yb³⁺ was formed through the growth process of “nucleation to crystallization and Ostwald ripening”. The upconversion luminescence (UCL) properties and mechanism of BiF₃:Ln³⁺ (Ln = Ho, Er, Tm)/Yb³⁺ under dual-wavelength excitation were also systematically investigated. The emission intensity of BiF₃:2%Er³⁺/20%Yb³⁺ by dual-wavelength excitation (λ = 980 nm + 1550 nm) was 1.49 times more than that excited by 1550 nm or 980 nm individually. Furthermore, the properties of the bright white and multicolor UCL showed that yellow, purple, green, or pinkish light could be observed by controlling the doping concentration of Ln³⁺ (Ln = Yb, Er, Tm, and Ho), indicating that they had potential applications in backlight sources of color displays and security labeling. The temperature sensitivity of BiF₃:2%Er³⁺/20%Yb³⁺ exhibited a downward tendency and its max value was about 0.0036 K⁻¹ at 273 K. Cell toxicity tests showed that the UCNPs in phospholipid aqueous solution presented low cytotoxicity. Also, in vivo imaging and X-ray imaging revealed that the BiF₃:2%Er³⁺/20%Yb³⁺ NPs had deep penetration and high contrast, which meant it could be used as a potential probe and contrast agent in in vivo optical bioimaging.

Multifunctional BiF₃:Ln³⁺(Ln = Ho, Er, Tm)/Yb³⁺ UCLNPs presented better performances in dual-wavelength synergy, thermosensitivity, emission color tuning, and bioimaging.