Enhanced brightness and photostability dye-sensitized Nd-doped rare earth nanocomplex for in vivo NIR-IIb vascular and orthotopic tumor imaging

doi:10.21203/rs.3.rs-4962996/v1

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Enhanced brightness and photostability dye-sensitized Nd-doped rare earth nanocomplex for in vivo NIR-IIb vascular and orthotopic tumor imaging

https://doi.org/10.21203/rs.3.rs-4962996/v1

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Rare-earth doped nanoparticles (RENPs) have shown promise in biomedical imaging, particularly in the NIR-IIb region, due to their deep tissue penetration and minimal light scattering. However, challenges such as low extinction coefficients, narrow excitation spectra, and susceptibility to quenching in aqueous environments limit their effectiveness. To overcome these obstacles, we developed a novel dye-sensitized, onion-like Nd-doped RENP nanocomplex designed to enhance NIR-IIb imaging performance. The onion-like Nd-RENP nanocomplex significantly boosts emission intensity at 1525 nm within the NIR-IIb range by reducing quenching and improving spectral overlap. The integration of an IR783-containing micellar layer further stabilizes the NIR dye, protecting it from quenching and reducing photobleaching. In vivo imaging studies demonstrated a 75-fold increase in luminance and a 9-fold improvement in photostability compared to free NIR dyes in aqueous solutions. Time-dependent in vivo studies confirmed the nanocomplex's capability for prolonged vascular and tumor imaging, maintaining high-resolution images for over an hour. Additionally, the nanocomplex supported successful 3D imaging reconstruction of biological tissues. The dye-sensitized onion-like Nd-RENP nanocomplex presents a significant advancement in NIR-IIb imaging, providing enhanced brightness and photostability. Its ability to maintain clear and stable imaging over extended periods suggests potential applications in dynamic vascular and tumor-targeted imaging. This innovation holds promise for future biomedical imaging technologies, particularly in areas requiring high-resolution and long-duration monitoring.

NIR-IIb bioimaging

rare-earth

core-shells

dye-sensitized

tumor imaging

Near-Infrared II (NIR-II, 1000–1700 nm) and its subset, NIR-IIb (1500–1700 nm) imaging, represent transformative advancements in the field of medical bioimaging. These technologies are distinguished by their deep tissue penetration and minimal invasiveness, significantly outperforming traditional imaging methods by minimizing autofluorescence and light scattering[1–10]. This facilitates high-resolution visualization of deep tissues, offering a clearer and more detailed insight into biological processes within a living organism.[11] NIR-II imaging, particularly in the NIR-IIb spectrum with minimal light scattering, is crucial for real-time, three-dimensional monitoring of disease progression, treatment responses, and the study of complex anatomical structures[12, 13].

Advancing NIR-IIb imaging agents to feature superior brightness, photostability, and biocompatibility is pivotal for addressing the inherent challenges and expanding the applications of inorganic nanomaterials in biomedicine[14–16]. Inorganic nanomaterials have significantly driven progress in biomedical diagnostics and therapies across a variety of modalities, including photoluminescence imaging (PLI)[17, 18], photoacoustic imaging (PAI)[19], photodynamic therapy (PDT)[20], X-ray excited photodynamic therapy (XDT)[21], sonodynamic therapy (SDT)[22], photothermal therapy (PTT)[23], and radioimmunotherapy (RIT)[24]. A critical challenge lies in precisely controlling and monitoring their spatial and temporal distribution within living biological systems, a limitation that hinders academic research and preclinical trial progression.[25] Enhancing their NIR-IIb imaging capabilities could overcome these obstacles, thereby improving the management and utilization of these materials in biomedicine. Owing to specific rare earth ions possessing luminescent energy levels in the NIR-IIb spectral range, rare-earth (lanthanide series) doped nanoparticles (RENPs) have emerged as promising inorganic NIR-II imaging agents[26–29]. However, the main challenges with RENPs include their notably low extinction coefficient, narrow excitation range, and a tendency to quench in aqueous environments, all of which limit their imaging effectiveness. Consequently, achieving high brightness and stability in in vivo NIR-IIb imaging with RENPs is challenging, with the scientific literature on this subject being limited, underscoring the necessity for further advancements in this area[30–34].

Nd as activator could significantly reduce tissue heating, cross-relaxation, and quenching problems, offering a lower heating effect compared to 980 nm excited Yb-RENP, and ensuring enhanced spectral overlap with NIR dyes for improved emission efficacy[35–37]. Recent advancements have focused on using dye-sensitized nanosystems to address the challenge of the low extinction coefficient in rare earth nanoparticles (RENPs). For example, NaYF₄:Yb,Er@NaYF₄:Nd nanoparticles, coated with DSPE-PEG and loaded with Alk-Pi, a modified NIR dye designed to combat aggregation-caused quenching (ACQ), have demonstrated significant improvements in signal-to-noise ratio (SNR) for in vivo NIR-II imaging[38–40]. These important references inspired this study to explore more advanced designs using reduced quenching onion-like (multi-shell) nanostructures and unmodified dyes, identify areas for improving luminescence brightness and photostability, and investigate the duration of tumor imaging capability. To enhance the versatility of this solution, we try to employed a convenient approach that does not require modifying the chemical structure of NIR dye. A polymethine NIR dye IR-783 without further modification, similar to ICG or IR806 and known for its strong NIR-I absorption and emission that overlap with the excitation of Nd, was incorporated.

In tackling the challenges of RENP-based NIR-IIb bioimaging, we aim to developed an innovative NIR-IIb imaging agent, referred to as the onion-like Nd-RENP nanocomplex, as illustrated in Scheme 1. It features a core made of NaYF₄ nanoparticles doped with Yb, Er, and Ce ions (i.e., NaYF₄:Yb,Er,Ce), which is sequentially coated within an onion-like multi-shell nanostructure. It highlights energy transfer within the onion-like Nd-RENP nanocomplex, leading to a 1525 nm emission enhancement, by minimizing quenching and enhance the cross-relaxation energy level of Er³⁺. This nanocomplex is composed of layers of NaYF₄:Yb, NaYF₄:Yb,Nd and undoped NaYF₄, all encased within a micellar layer infused with the IR dye IR783. The design aims to enhance emission intensity in the NIR-IIb range while addressing common RENP challenges, such as back energy transfer in NaYF₄:Yb, spectral mismatch in NaYF₄:Yb,Nd, and quenching inhibition by NaYF₄ outmost shell[41–47]. The critical role of the inert outer shell and the proximity (under 10 nm) between Nd-RENP and the dye is emphasized for boosting Förster Resonance Energy Transfer (FRET) efficiency[48–52]. However, NIR dyes like IR783 are prone to photobleaching, posing limitations for prolonged imaging. Ingeniously, this issue is addressed by embedding IR783 within the hydrophobic layers of 1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly-ethylene glycol)] (DSPE-PEG) onto the nanocomplex. This encapsulation strategy not only shields IR783 from oxygen, reducing photobleaching, but also enhances dye stability. The DSPE-PEG layer is pivotal, offering a biocompatible and protective environment that ensures the dye's stability and functionality, streamlining the approach for more effective NIR-IIb imaging applications[53].

This novel NIR-IIb imaging agent, onion-like Nd-RENP nanocomplex, which was designed to enhance the spectral efficiency through dye-sensitization and benefits from the protective function of the DSPE-PEG micellar layer. This strategy not only enhances NIR-IIb imaging for vascular visualization but also enables passive tumor targeting, facilitating detailed studies of biodistribution over time. By advancing these capabilities, this approach significantly broadens the range of medical applications for NIR-IIb functional imaging, forging new paths for diagnostic and therapeutic intervention in the medical field.

Synthesis and characterization of RENPs

For precise and consistent control over the uniformity and thickness of the shells, the engineered nanomaterials were fabricated using an optimized thermal decomposition approach. This method employed a stepwise layer-by-layer technique to guarantee uniform coating of the various shells onto the core surfaces. A series of RENP coated with or without shells were synthesized to investigate their structural and optical properties as illustrated in Fig. 1.

The TEM images presented in Fig. 1a-d illustrate the progression of rare-earth-doped nanoparticles (RENPs) from simple cores to complex, onion-like structures. Initially, the core, denoted as NaYF₄:Yb,Er,Ce (composition NaY_0.87F₄:Yb_0.1,Er_0.01,Ce_0.02), in Fig. 1a shows a uniform, round shape with an average diameter of about 15 nm. The co-doping of Ce with Er³⁺ in the core is instrumental in enhancing the 1525 nm emission from Er³⁺, achieved by suppressing upconversion luminescence via cross-relaxation processes. In Fig. 1b, the NaYF₄:Yb,Er,Ce core (C) is encased within a NaYF₄:Yb shell, leading to core-shell (CS) nanoparticles approximately 20 nm in diameter. This increase in size signifies the successful deposition of a 2.5 nm thick shell around the core. The purpose of the NaYF₄:Yb shell is to improve energy transfer efficiency by preventing reverse energy transfer from Er to Nd, while facilitating the forward transfer sequence from Nd to Yb and then to Er. Further evolution is observed in Fig. 1c, where a second shell composed of NaY_0.6F_₄:Nd_0.3,Yb_0.1 (30% Nd and 10% Yb) expands the particle size to around 24 nm. This indicates the formation of a core-double shell (CS3) structure, with the second layer effectively harnessing and transmitting the 793 nm excitation photons to the Er emission center in the core. The 2 nm thickness of the second shell underscores the precision of the coating process. The final stage, as depicted in Fig. 1d, involves the addition of an undoped NaYF₄ shell, culminating in a core-triple shell (CS3) architecture with a size of approximately 27 nm. This outermost layer aims to minimize the quenching effects on the Nd and Yb dopants in the second shell, as evidenced by the uniform 1.5 nm increase in particle size, indicative of a successful coating. The high-resolution TEM (HRTEM) image reveals that the CS3 architecture is of a single-crystalline nature, with well-defined lattice fringes (d₁₀₀ = 0.52 nm) and uniform spherical particle morphology (Fig. S1). The Fig. S2 shows Dynamic Light Scattering (DLS) analysis of nanoparticle size distribution, illustrating progressively larger mean diameters with each additional shell layer, from the core (15.1 ± 4.6 nm), core-shell (20.4 ± 5.5 nm), core-double shell (23.7 ± 6.1 nm) to the core-triple shell (27.3 ± 7.1 nm), with each graph displaying a single, narrow peak indicating consistent results with the TEM images.

X-ray diffraction (XRD) patterns, shown in Fig. 1e, characterize the core and core-shell(s) RENPs, juxtaposed with a standard reference pattern (JCPDS No. 16–0334). These patterns reveal that the nanoparticles retain the hexagonal β-NaYF₄ crystal structure across all stages of layer addition. Identical diffraction peaks at approximately 17°, 30°, 43°, and 53° correspond to the β-NaYF₄ planes (100), (110), (201), and (102), respectively. The consistency of the XRD patterns across the C, CS, CS3, and CS3 samples confirms that the dopants and the layer-by-layer assembly process do not alter the fundamental crystal characteristics of β-NaYF₄.

Luminescent Spectral Characterization of RENPs

Luminescent Spectral Characterization of RENPs for NIR-IIb Imaging Applications To evaluate the synthesized RENPs' NIR-IIb emission potential as an imaging agent, optical analysis was conducted using a photoluminescence spectrometer with an InGaAs detector. The emission spectra, depicted in Fig. 1f, exhibit distinct downshifting luminescence peaks at 975 nm and 1525 nm. These peaks correspond to transitions within Yb³⁺ (975 nm, from ²F_5/2 to ²F_7/2) and Er³⁺ (1525 nm, from ⁴I_13/2 to ⁴I_15/2), respectively, under a 793 nm excitation. The core (NaYF₄:Yb,Er,Ce; C) showed the weakest emission intensity. In contrast, the core-shell (NaYF₄:Yb,Er,Ce@ NaYF₄:Yb; CS) and core-double shell (NaYF₄:Yb,Er,Ce@NaYF₄:Yb@NaYF₄:Nd,Yb; CS3) structures demonstrated progressively stronger emissions. Remarkably, the core-triple shell (NaYF₄:Yb,Er,Ce@NaYF₄:Yb@NaYF₄:Nd,Yb@NaYF₄; CS3) configuration exhibited the highest NIR-IIb luminescence intensity at 1525 nm. This trend indicates that the onion-like multi-shell design boosts luminescence by enabling Nd sensitization, reducing backward energy transfer, and minimizing surface quenching. The excitation spectra showed in Fig. S3, with emission monitored at 1525 nm, further confirmed the augmented photoluminescent characteristics, showcasing prominent peaks at 576 nm, 740 nm, and 793 nm. These peaks are indicative of transitions in neodymium (Nd, from ⁴I_9/2 to ⁴F_5/2, ²H_9/2) and are unique to CS3 and CS3, signaling Nd's incorporation in the second shell of these configurations. The energy transfer mechanism in CS3 and CS3 encompasses the absorption of 793 nm photons, facilitating energy transfer sequentially through Nd to Yb, then to Er, culminating in the 1525 nm emission. The addition of a third, undoped shell significantly curtails the quenching effect, enhancing the 1525 nm luminescence approximately 5-fold when excited at 793 nm.

Surface Modification and Dye-Encapsulation onto Onion-Like Nd-RENPs

To be utilized as an imaging agent within biological entities, the nanomaterial necessitates surface modification to achieve a hydrophilic surface while preserving its intrinsic optical properties. The sequential surface modification and dye encapsulation strategy for the onion-like Nd-RENPs (CS3), aimed at NIR-IIb imaging applications, is depicted in Fig. 2a. The oleic acid-coated CS3 (CS3) nanoparticles were synthesized through a thermal decomposition method and suspended in n-hexane. Modifying CS3's surface with DSPE-mPEG3.4k transforms it into a hydrophilic entity (CS3-PEG nanoparticles), facilitating its dispersion in aqueous media and making it suitable for biomedical applications. Subsequently, the CS3-PEG nanoparticles were loaded with the NIR dye IR783, producing CS3-PEG/IR783 (i.e., onion-like Nd-RENP nanocomplex), which amplifies brightness via a dye-sensitized mechanism. The encapsulation of IR783 within the hydrophobic layer of DSPE shifts its absorption peak from 777 nm (when in water) to 793 nm, as demonstrated in Fig. 2b. This red shift validates the successful integration of IR783 into the DSPE-PEG micellar layer, indicating an altered environmental influence compared to its aqueous solubility. Dynamic Light Scattering (DLS) analysis, illustrated in Fig. 2c, reveals that the CS3-PEG/IR783 nanoparticles possess an average diameter of 32 nm in aqueous dispersion. This particle size analysis confirms that the nanoparticles exhibit minimal aggregation and are well-dispersed in water following the modification process. This underscores the efficacy of the surface modification and dye encapsulation strategy in enhancing the applicability of Nd-RENPs for biological imaging applications.

Upon 793 nm excitation, the luminescent emission spectra depicted in Fig. 2d show that the PEGylated core nanoparticles (C-PEG), both with and without IR783, exhibit weak luminescent emissions following surface modification and dye encapsulation. Conversely, the CS3-PEG demonstrates significant NIR-IIb emission at 1525 nm, suggesting that the emissions are primarily directly excited by Nd in the second shell, even without the NIR dye. Among all groups, CS3-PEG/IR783 (i.e., onion-like Nd-RENP nanocomplex) shows the strongest NIR-IIb luminescence, about 3 to 4 times greater than that of CS3-PEG alone. This amplification is indicative of the efficient energy transfer from the high extinction coefficient IR783 dye to the CS3 structure. The excitation spectra, presented in Fig. 2e, further affirm the effective integration, as evidenced by the broad excitation band of CS3-PEG/IR783 in the 600–850 nm range. This band closely aligns with the absorption spectrum of IR783 loaded in CS3, as shown in Fig. 2b, serving as evidence of Förster Resonance Energy Transfer (FRET) between IR783 and the emitters in CS3. However, as clearly shown in Fig. 2e, the excitation spectrum of IR783 can be transferred to 1525 nm emission, which provides preliminary evidence of the energy transfer process. The emission intensity at 1525 nm of CS3-PEG/IR783 is approximately 28-fold, 12-fold, and 3.75-fold higher than that of C-PEG, C-PEG/IR783, and CS3-PEG, respectively, due to dye sensitization. The emission and excitation spectra results corroborate each other. This interaction is crucial for the enhanced brightness of the dye-sensitized RENP within the NIR-IIb region. The functionalization process not only makes CS3-PEG/IR783 biocompatible and water-dispersible but also enhances its luminescent properties, as evidenced by the spectral data. The presence of the IR783 dye around the CS3 is pivotal in this enhancement, likely owing to the dye's absorption and emission capabilities in the NIR range, which complements the excitation profile of Nd in the RENP.

NIR-II Imaging Test in tubes and phantoms

We further investigated the optical properties of the IR783 within various PEGylated RENP with or without different shells, focusing on the NIR-IIb imaging centered at 1525 nm emitted from Er³⁺ and its penetration capabilities in tissue-mimicking phantoms. As depicted in Fig. 3a and 3b, the inclusion of IR783 in different PEGylated RENP constructs (C-PEG, CS-PEG, CS3-PEG, and CS3-PEG, corresponding to the structure of Fig. 1) markedly enhanced the luminescence signal, confirming the active role of IR783 sensitized RENPs in the NIR-II imaging. This enhancement was quantitatively demonstrated in Fig. 3c, where each PEGylated RENP constructs with IR783 exhibited significant increases in 1525 nm NIR-IIb luminescence intensity when compared to their counterparts without the IR783 loading. The result illustrates the significant enhancement in luminescence intensity at 1525 nm achieved by combining different PEGylated RENP constructs with the NIR dye IR783. Specifically, the enhancement factors for C-PEG, CS-PEG, CS3-PEG, and CS3-PEG are 5.1, 5.8, 12.8, and 3.3 times, respectively, when integrated with IR783. Remarkably, CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) exhibits a 75-fold increase in luminescence compared to the C-PEG without dye, a RENP (NaYF₄:Yb,Er,Ce) widely used in related research. The data reveals that the enhancement factor of CS3-PEG/IR783 is approximately four times greater than that of CS3-PEG/IR783 (12.8 to 3.3 times). This discrepancy highlights the sensitivity of Förster Resonance Energy Transfer (FRET) efficiency to the spatial proximity between the donor (IR783) and the acceptor (Nd). Despite the FRET distance for CS3-PEG/IR783 being roughly above 2.5 nm slightly greater than that for CS3-PEG/IR783, the CS3-PEG/IR783 achieves the highest overall brightness. This superior luminosity is attributed to the reduced quenching effect on Nd by the 3rd undoped shell, underlining the importance of quenching mitigation in amplifying luminescence intensity. This study demonstrates that having the 3rd shell significantly enhances efficiency, a key factor that has not been explored in previous related research[38, 39].

NIR-II Imaging test in tubes and phantoms

Figure 3d presents the penetration depth test of CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex), showcasing the nanomaterial's ability to emit the luminescence signal from various depths within a controlled phantom environment. A clear trend was observed where the luminescence intensity diminished as the depth increased, indicative of the inherent limitations posed by tissue scattering and absorption. Nonetheless, the sustained visibility at greater depths for extended exposure times and higher dynamic range suggests that careful optimization of these parameters could enhance the performance of CS3-PEG/IR783 in deep tissue imaging. The SNR analysis in Fig. 3e illustrates a predictable decline in signal clarity with increasing depth. The signal-to-noise ratios (SNRs) for CS3-PEG/IR783 at various tissue depths decrease progressively, measuring approximately 700 at 1 mm, 240 at 2 mm, 60 at 3 mm, 27 at 4 mm, 8.2 at 5 mm, and 4 at 6 mm. Luminescence signals of CS3-PEG/IR783 can be detected up to a depth of 6 mm. The linear scale emphasizes the sharp fall-off in SNR, which is critical for practical imaging applications where maintaining a high SNR is essential for accurate detection and visualization. Meanwhile, the logarithmic scale delineates the decay more subtly, providing insights into the potential for image processing and enhancement techniques to salvage useful imaging data from lower-SNR signals at greater depths.

Photostability test of onion-like Nd-RENPs nanocomplex

The series of images in Fig. 4a depict two samples: IR783 dye and CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex), subjected to luminescent imaging over a period of 180 minutes. For the free IR783 dispersed in water, there is a pronounced decrease in luminescence intensity over time, with the signal becoming barely detectable after 60 minutes. In contrast, the CS3-PEG/IR783 shows a much more gradual decline in luminescence, maintaining a detectable signal even after 180 minutes in water. The plots of Fig. 4b provides a quantitative analysis of the luminescence intensity decay over time. The open circles representing the IR783 sample exhibit a steep decline, with the intensity dropping sharply within the first 20 minutes and continuing to decrease thereafter. The filled squares representing the CS3-PEG/IR783 sample show a more gradual decline, with a notable plateau from approximately 50 minutes onwards, indicating a sustained luminescence intensity. The results from both the luminescence images and the quantitative plot clearly demonstrate that CS3-PEG/IR783 maintains its luminescence significantly longer than the IR783 dye alone. This suggests that the CS3-PEG encapsulation provides a protective effect, possibly by shielding the IR783 from photobleaching agents present in the environment or by stabilizing the dye within its matrix, thus preventing rapid decay of luminescence. It is also notable that the photon counts for the CS3-PEG and IR783 combination does not fall below 80% within the timeframe observed, whereas the IR783 alone drops to around 10%. The sharp decline in luminescence of the IR783 sample is likely due to the absence of protective encapsulation, leading to rapid photobleaching when exposed to the excitation source or environmental factors that quench the luminescence. The stark difference in the luminescence decay profiles between the two samples underscores the effectiveness of the CS3-PEG/IR783 in prolonging the functional lifetime of the luminescent dye. The time taken for the luminescence to decay to 80% of its initial value is 20 minutes for free IR783 and 180 minutes for CS3-PEG/IR783. This significant 9-folds difference suggests that CS3-PEG/IR783 may play a crucial role in sustaining the photonic property of IR783 over time, which could be beneficial for applications requiring prolonged or stable photonic emissions, such as in bioimaging or photodynamic therapy. After 24 hours, CS3-PEG/IR783 still retained 66% of its stability, indicating that the primary factor contributing to photobleaching during the first 180 minutes was the laser exposure during testing. This suggests that under light-protected conditions, its stability can be maintained over a prolonged period. This prolonged luminescence of CS3-PEG/IR783 is particularly advantageous for applications that require long-term imaging or monitoring, such as in vivo biological tracking, where a consistent and reliable signal is crucial. The data supports the potential use of CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) in practical applications, as it offers enhanced stability and persistence of the luminescent signal.

As shown in Fig. 2e, 75% of the total luminescence at 1525 nm from CS3-PEG/IR783 is attributed to the brightness enhancement from IR783 dye sensitization (original emission emission = 1:4). The optical properties of CS3-PEG are very stable and do not show significant degradation over time. If the IR783 within CS3-PEG/IR783 were as prone to degradation as free IR783, this increased emission would diminish as rapidly as the fluorescence of free IR783. However, when comparing the luminescence at the 60-minute mark, free IR783's intensity has decreased to 20% (-80%), while CS3-PEG/IR783 has only decreased to 90% (-10%). Given that 75% of the CS3-PEG/IR783 luminescence is due to IR783 sensitization, normalizing the data results in (-10/0.75) = -13.3%. This indicates that the stability of IR783 within CS3-PEG/IR783 is more than six times greater than that of free IR783. Nevertheless, our focus here is on the overall brightness. The optical properties of CS3-PEG are very stable and do not show significant degradation over time.

Temporal dynamics of luminescent agents in murine model

The CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) exhibits high biocompatibility with no significant toxicity from the cell viability test in Fig. S4, making it suitable for biomedical applications. In Fig. 5, we evaluate the efficacy of NIR-IIb imaging for detailed anatomical visualization in a murine model, employing a 1400 longpass filter (LPF) to delineate vascular structures with high clarity. Figure 5a and 5c offer whole-body ventral and cranial images of a mice, respectively, where the vascular architecture is prominently visible, serving as a proof to the resolving power of NIR-IIb imaging at 1400 LPF of CS3-PEG/IR783. The quantitative analysis of these images, depicted in Fig. 5e and 5g, exhibits signal-to-background (S/B) ratios that accentuate the stark contrast between the vasculature and the surrounding tissue. The full-body Fig. 5a with an S/B ratio of ~ 2–7 and a FWHM of ~ 1.1 mm in Fig. 5e indicates a reasonable contrast suitable for mapping out the general anatomy and vasculature. The cranial image Fig. 5c with an S/B ratio of ~ 4 in Fig. 5g show that the NIR-IIb imaging can provide detailed information about deeper tissues of brain. Figure 5b and Fig. 5d present magnified views obtained with a 10X objective lens, offering an augmented perspective of the vascular clarity possible with NIR-IIb imaging. The accompanying quantitative analyses, shown in Fig. 5f and Fig. 5h, further reinforce the superior spatial resolution achieved, as evidenced by the distinct peak values and narrow FWHM metrics, underscoring the ability to discern fine vascular details. The detailed Fig. 5f and 5h reveal fine vascular structures with high clarity, which is further supported by the S/B ratios of ~ 1.6 and ~ 4, respectively, and FWHM values of 0.11 mm in Fig. 5f and 0.6 mm in Fig. 5h, demonstrating high-resolution imaging capabilities. The application of a 1400 LPF in NIR-IIb imaging has demonstrated a profound ability to enhance the resolution and contrast of vascular structures within a biological system. This is particularly evident in the full-body images of the mouse, where the vasculature is rendered with exceptional clarity. The magnified images further highlight the potential of NIR-IIb imaging in medical diagnostics and research, where such detailed visualization can significantly contribute to the understanding of complex vascular networks.

Figure 5i through 5l chronicle the imaging performance of the FDA-approved contrast agent ICG in a prone mouse, captured across a spectrum of LPF settings. These images elucidate a correlation between increasing wavelength and image clarity, albeit with a concurrent diminution in brightness. Notably, at longer wavelengths where scattering is minimal, the comparison with the CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) of Fig. 5m reveals that the latter provides markedly sharper NIR-IIb imaging. The comparative analysis with ICG illustrates the limitations of conventional imaging agents, particularly at longer wavelengths where the inherent properties of CS3-PEG/IR783 afford a more robust imaging modality. This is indicative of CS3-PEG/IR783's superior photophysical attributes, which may include higher absorption cross-sections and quantum yields in the NIR-IIb window, potentially revolutionizing in vivo imaging applications.

The results bolster the argument for CS3-PEG/IR783 as a superior contrast agent for NIR-IIb imaging, particularly in scenarios where high-resolution and high-contrast images are imperative. Moreover, the decrease in brightness at longer wavelengths with ICG underscores the need for imaging agents that can maintain both luminosity and clarity, as exemplified by CS3-PEG/IR783. Future studies should focus on optimizing CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) formulations for preclinical applications, with an emphasis on safety, biodistribution, and pharmacokinetics to facilitate translation from bench to bedside. These data are system-related, and the precision of the instrument configurations (camera quality/algorithms/lenses) used by each team varies, making direct comparisons difficult. However, in similar studies to ours, the highest reported SNR is only ~ 2, whereas our study achieved a maximum SNR of ~ 7.

NIR-IIb imaging in different murine models using onion-like Nd-RENPs nanocomplex

A diverse set of NIR-IIb imaging modalities in Fig. 6 to assess the biodistribution, delivery, and excretion of onion-like Nd-RENPs nanocomplex (CS3-PEG/IR783) in various murine models. The normal mice images in Fig. 6a and 6b, CS3-PEG/IR783 is initially present in the cerebral vasculature but is cleared within 24 hours, leaving no significant accumulation in brain. This rapid clearance indicates efficient renal or hepatic excretion pathways and minimal retention in the brain. The clearance of CS3-PEG/IR783 from the normal brain vasculature suggests it has a favorable profile for transient imaging without long-term retention, which is desirable for quick diagnostic applications.

The in-situ injection model images in Fig. 6c and 6d involves direct injection of CS3-PEG/IR783 into the mouse brain. After 24 hours, the majority of the material remains at the injection site, albeit with reduced brightness, suggesting partial CS3-PEG/IR783 migration into the vasculature and subsequent hepatic excretion. No luminescence is observed in other regions, indicating a lack of systemic distribution. The retention of the nanoagent at the brain injection site in the in-situ model suggests potential for localized imaging, although the partial clearance observed implies a need for careful dosing and imaging timing to optimize signal visibility.

The stroke simulated model images in Fig. 6e and 6f, which CS3-PEG/IR783 is intravenously administered post-cerebral puncture, initial vascular distribution is akin to that in normal mice. However, after 24 hours, CS3-PEG/IR783 accumulates at the suture site of the surgical wound, while the rest is cleared from the vasculature. The persistent optical signal at the suture site likely results from the nanoagent's permeation with blood into the wound. The stroke simulated model's results are particularly intriguing, as they demonstrate the agent's potential to highlight areas of vascular compromise. The accumulation at the suture site may have implications for post-surgical imaging or monitoring therapeutic interventions in neurovascular injuries.

The vessel ligation experiments in Fig. 6g and 6h simulate blood flow obstruction and reperfusion using an elastic band. Upon ligation, the posterior tibial vein exhibits no signal due to blocked flow; once the band is released, blood reperfusion is indicated by the return of the luminescent signal. The vessel ligation experiments provide a clear demonstration of CS3-PEG/IR783's utility in visualizing blood flow dynamics, with potential applications in assessing vascular patency or the success of surgical interventions.

Figure 6i examines feces of mice to determine if CS3-PEG/IR783 is excreted via the fecal route. The presence of NIR-IIb signals in feces confirms that at least a portion of the nanocomplex is indeed excreted hepatically. This result underscores the agent's biodistribution, confirming hepatic clearance with fecal excretion, a critical consideration for the clinical translation of any imaging agent, as it influences both the imaging window and the safety profile. The observation of NIR-IIb luminescent signals in the excreta provides compelling evidence that the structure of the CS3-PEG/IR783 nanocomplex remains intact even after systemic circulation and subsequent excretion. This finding is consistent with the in vitro test results, where the nanocomplex demonstrated remarkable stability, retaining its luminescent property even after 24 hours. The sustained stability observed in both in vitro and in vivo conditions underscores the robustness of the design, ensuring that the nanocomplex can maintain its structural integrity and functional performance over extended periods, both within biological systems and in controlled environments.

Time-dependent NIR-IIb imaging of normal mice and tumor-bearing mice using onion-like Nd-RENPs nanocomplex

The dynamic NIR-IIb imaging capability of the CS3-PEG/IR783 (onion-like Nd-RENP nanocomplex) were systematically evaluated through a series of time-dependent imaging studies in murine models (normal mice and 4T1 tumor model). The results in Fig. 7a and 7b demonstrated that immediately following administration, the nanocomplex rapidly disseminates throughout the vascular system, with significant luminescence observed as early as 1-minute post-injection. This early-phase imaging clearly visualizes the systemic circulation of the nanocomplex, providing a high-contrast view of the vascular network.

As time progresses, the nanocomplex’s distribution in normal mice remains predominantly within the vasculature for up to 1-hour post-injection, a duration significantly longer than the 10-minute window reported in previous related studies.[38–40] After this period, the signal intensity begins to gradually decrease, particularly in the peripheral regions. By 2 to 4 hours post-injection, a noticeable reduction in luminescence is observed, consistent with the onset of clearance mechanisms. After 24 hours, the luminescent signal is significantly diminished, indicating that the majority of the nanocomplex has been cleared from the circulatory system, likely through hepatic and renal pathways.

In contrast, tumor-bearing mice of 4T1 orthotopic tumor model exhibit a different pattern of biodistribution. The NIR-IIb imaging reveals a preferential accumulation of the CS3-PEG/IR783 nanocomplex at tumor sites, which becomes increasingly apparent from 10 minutes post-injection and persists for the duration of the study. The enhanced permeability and retention (EPR) effect of the nanocomplex at 4T1 orthotopic tumor sites demonstrates that the size of CS3-PEG/IR783 is suitable for tumor-targeted imaging applications. This results in a strong and sustained signal, facilitating clear delineation of tumor boundaries.

Further analysis using 3D reconstruction techniques offers a detailed view of the vascular system. The right and left views, along with the depth-encoded 3D imaging, highlight the nanocomplex's ability to provide high-resolution images of the vasculature at various depths, with the color-coded depth map offering precise spatial information. This depth-resolved imaging underscores the utility of the CS3-PEG/IR783 nanocomplex for comprehensive vascular mapping, essential for both diagnostic and therapeutic purposes in the future[54].

These findings collectively suggest that the CS3-PEG/IR783 nanocomplex not only facilitates effective NIR-IIb imaging of systemic circulation and tumor localization but also provides valuable depth information, enhancing its potential of RENP nanocomplex as a versatile imaging agent in cutting-edge biomedical imaging.

In this study, we successfully developed an innovative new dye sensitized near- NIR-IIb imaging nano-agent, the onion-like Nd-doped rare-earth nanoparticle complex (Nd-RENP), which demonstrated enhanced brightness and photostability for dynamic vascular and tumor-targeted imaging applications. The significant improvement in brightness and photostability is attributed to the multi-shell architecture and micellular encapsulation of the nanocomplex, which effectively mitigates quenching, enhances spectral overlap, and reduces the photobleaching of organic dye, thereby optimizing emission efficiency and photostability. Moreover, in vivo studies confirmed the ability of this onion-like Nd-RENP nanocomplex to maintain high-resolution imaging of mice for over an hour post-injection, with clear visibility of both vascular and tumor-targeted images in murine model with orthotopic tumor.

The superior performance of the nanocomplex, coupled with its extended imaging capabilities, highlights its potential to significantly impact the study of biological processes, disease progression, and therapeutic monitoring in a variety of biomedical applications. These findings set a new benchmark for NIR-IIb bioimaging technologies, emphasizing the promise of the onion-like Nd-RENP nanocomplex as a versatile and powerful imaging agent for future clinical and preclinical applications.

Acknowledgments
This research was generously supported by the National Science and Technology Council of Taiwan (ROC) through grants NSTC 12-2221-E-A49 -034 -, MOST 111-2811-M-A49A-002-, MOST 110-2811-M-A49A-001-, and MOST 110(111,112)-2124-M-A49A-501-. The authors sincerely appreciate the Council's continuous support, which was instrumental in the successful completion of this work.

Author contributions

SLL: conceptualization, investigation, methodology, writing original draft. SPS, YZY, HYC: investigation, methodology. CAC: writing—review. TYL: writing—review and editing. HKC: writing—review and editing, funding acquisition, supervision. All authors read and approved the final manuscript.

Data Availability

All data needed to support the conclusions are present in the paper and/or the Supplementary Information. Additional data related to this study are available from the corresponding authors upon reasonable.

Ethics approval and consent to participate

All animal experiments were approved by Institutional Animal Care and Use Committee of the National Yang Ming Chiao Tung University (1100509n, approved date Aug 1, 2021). All the procedures conformed to the Guide for the Care and Use of Laboratory Animals, NIH publication (8th edition, 2011).

Consent for publication

All authors agree for publication.

Competing interests

The authors declare no competing interests.

Weissleder R. A clearer vision for in vivo imaging. Nat Biotechnol. 2001;19:316–7.
Smith AM, Mancini MC, Nie S. Second window for in vivo imaging. Nat Nanotechnol. 2009;4:710–1.
Hong G, Lee JC, Robinson JT, Raaz U, Xie L, Huang NF, Cooke JP, Dai H. Multifunctional in vivo vascular imaging using near-infrared II fluorescence. Nat Med. 2012;18:1841–6.
Hong G, Antaris AL, Dai H. Near-infrared fluorophores for biomedical imaging. Nat Biomed Eng. 2017;1:0010.
Kenry, Duan Y, Liu B. Recent Advances of Optical Imaging in the Second Near-Infrared Window. Adv Mater. 2018;30:1802394.
Diao S, Blackburn JL, Hong G, Antaris AL, Chang J, Wu JZ, Zhang B, Cheng K, Kuo CJ, Dai H. Fluorescence Imaging In Vivo at Wavelengths beyond 1500 nm. Angew Chem Int Ed. 2015;54:14758–62.
Yang Y, Jiang Q, Zhang F. Nanocrystals for Deep-Tissue In Vivo Luminescence Imaging in the Near-Infrared Region. Chem Rev 2023.
Luo Z, Hu D, Gao D, Yi Z, Zheng H, Sheng Z, Liu X. High-Specificity In Vivo Tumor Imaging Using Bioorthogonal NIR-IIb Nanoparticles. Adv Mater. 2021;33:2102950.
Ren F, Liu H, Zhang H, Jiang Z, Xia B, Genevois C, He T, Allix M, Sun Q, Li Z, Gao M. Engineering NIR-IIb fluorescence of Er-based lanthanide nanoparticles for through-skull targeted imaging and imaging-guided surgery of orthotopic glioma. Nano Today. 2020;34:100905.
Lin H, Lin Z, Zheng K, Wang C, Lin L, Chen J, Song J. Near-Infrared-II Nanomaterials for Fluorescence Imaging and Photodynamic Therapy. Adv Opt Mater. 2021;9:2002177.
Sun B, Fang D, Li W, Li M, Zhu S. NIR-II nanoprobes for investigating the glymphatic system function under anesthesia and stroke injury. J Nanobiotechnol. 2024;22:200.
Su S-P, Lin S-L, Chan Y-H, Lee Y-J, Lee Y-C, Zeng P-X, Li Y-X, Yang M-H, Chiang HK. Development of Stereo NIR-II Fluorescence Imaging System for 3D Tumor Vasculature in Small Animals. Biosensors. 2022;12:85.
Su S-P, Lee Y-C, Lin S-L, Li Y-X, Lin M-Y, Chan Y-H, Lee Y-J, Yang M-H, Chiang HK. Realization of NIR-II 3D whole-body contour and tumor blood vessels imaging in small animals using rotational stereo vision technique. J Biomed Opt. 2023;28:094807.
Wu J, Shi Z, Zhu L, Li J, Han X, Xu M, Hao S, Fan Y, Shao T, Bai H, et al. The Design and Bioimaging Applications of NIR Fluorescent Organic Dyes with High Brightness. Adv Opt Mater. 2022;10:2102514.
Li B, Zhao M, Lin J, Huang P, Chen X. Management of fluorescent organic/inorganic nanohybrids for biomedical applications in the NIR-II region. Chem Soc Rev. 2022;51:7692–714.
Mu J, Xiao M, Shi Y, Geng X, Li H, Yin Y, Chen X. The Chemistry of Organic Contrast Agents in the NIR-II Window. Angew Chem Int Ed. 2022;61:e202114722.
Kim D, Kim J, Park YI, Lee N, Hyeon T. Recent development of inorganic nanoparticles for biomedical imaging. ACS Cent Sci. 2018;4:324–36.
Yang Y, Chen M, Wang P, Sai L, Chen C, Qian P, Dong S, Feng S, Yang X, Wang H, et al. Highly thermal stable RNase A@PbS/ZnS quantum dots as NIR-IIb image contrast for visualizing temporal changes of microvasculature remodeling in flap. J Nanobiotechnol. 2022;20:128.
Fu Q, Zhu R, Song J, Yang H, Chen X. Photoacoustic imaging: contrast agents and their biomedical applications. Adv Mater. 2019;31:1805875.
Colombeau L, Acherar S, Baros F, Arnoux P, Gazzali AM, Zaghdoudi K, Toussaint M, Vanderesse R, Frochot C. Inorganic nanoparticles for photodynamic therapy. Light-responsive nanostructured Syst Appl Nanomed 2016:113–34.
Chen H, Wang GD, Chuang Y-J, Zhen Z, Chen X, Biddinger P, Hao Z, Liu F, Shen B, Pan Z. Nanoscintillator-mediated X-ray inducible photodynamic therapy for in vivo cancer treatment. Nano Lett. 2015;15:2249–56.
Sun L, Wang P, Zhang J, Sun Y, Sun S, Xu M, Zhang L, Wang S, Liang X, Cui L. Design and application of inorganic nanoparticles for sonodynamic cancer therapy. Biomater Sci. 2021;9:1945–60.
Fernandes N, Rodrigues CF, Moreira AF, Correia IJ. Overview of the application of inorganic nanomaterials in cancer photothermal therapy. Biomater Sci. 2020;8:2990–3020.
Wang Y-C, Tsai S-h, Chen M-H, Hsieh F-Y, Chang Y-C, Tung F-I, Liu T-Y. Mineral Nanomedicine to Enhance the Efficacy of Adjuvant Radiotherapy for Treating Osteosarcoma. ACS Appl Mater Interfaces. 2022;14:5586–97.
Ferreira CA, Goel S, Ehlerding EB, Rosenkrans ZT, Jiang D, Sun T, Aluicio-Sarduy E, Engle JW, Ni D, Cai W. Ultrasmall Porous Silica Nanoparticles with Enhanced Pharmacokinetics for Cancer Theranostics. Nano Lett. 2021;21:4692–9.
Ding S, Lu L, Fan Y, Zhang F. Recent progress in NIR-II emitting lanthanide-based nanoparticles and their biological applications. J Rare Earth. 2020;38:451–63.
Yan J, Li B, Yang P, Lin J, Dai Y. Progress in Light-Responsive Lanthanide Nanoparticles toward Deep Tumor Theranostics. Adv Funct Mater. 2021;31:2104325.
Lv R, Raab M, Wang Y, Tian J, Lin J, Prasad PN. Nanochemistry advancing photon conversion in rare-earth nanostructures for theranostics. Coord Chem Rev. 2022;460:214486.
Xu D, Li C, Li W, Lin B, Lv R. Recent advances in lanthanide-doped up-conversion probes for theranostics. Front Chem 2023, 11.
Zou W, Visser C, Maduro JA, Pshenichnikov MS, Hummelen JC. Broadband dye-sensitized upconversion of near-infrared light. Nat Photonics. 2012;6:560.
Wu X, Zhang Y, Takle K, Bilsel O, Li Z, Lee H, Zhang Z, Li D, Fan W, Duan C, et al. Dye-Sensitized Core/Active Shell Upconversion Nanoparticles for Optogenetics and Bioimaging Applications. ACS Nano. 2016;10:1060–6.
Garfield DJ, Borys NJ, Hamed SM, Torquato NA, Tajon CA, Tian B, Shevitski B, Barnard ES, Suh YD, Aloni S, et al. Enrichment of molecular antenna triplets amplifies upconverting nanoparticle emission. Nat Photonics. 2018;12:402–7.
Han S, Deng R, Gu Q, Ni L, Huynh U, Zhang J, Yi Z, Zhao B, Tamura H, Pershin A, et al. Lanthanide-doped inorganic nanoparticles turn molecular triplet excitons bright. Nature. 2020;587:594–9.
Zhao F, Hu J, Guan D, Liu J, Zhang X, Ling H, Zhang Y, Liu Q. Boosting Dye-Sensitized Luminescence by Enhanced Short-Range Triplet Energy Transfer. Adv Mater. 2023;35:2304907.
Matulionyte M, Skripka A, Ramos-Guerra A, Benayas A, Vetrone F. The Coming of Age of Neodymium: Redefining Its Role in Rare Earth Doped Nanoparticles. Chem Rev. 2023;123:515–54.
Chen G, Shao W, Valiev RR, Ohulchanskyy TY, He GS, Ågren H, Prasad PN. Efficient Broadband Upconversion of Near-Infrared Light in Dye-Sensitized Core/Shell Nanocrystals. Adv Opt Mater. 2016;4:1760–6.
Shao W, Chen G, Kuzmin A, Kutscher HL, Pliss A, Ohulchanskyy TY, Prasad PN. Tunable Narrow Band Emissions from Dye-Sensitized Core/Shell/Shell Nanocrystals in the Second Near-Infrared Biological Window. J Am Chem Soc. 2016;138:16192–5.
Liang T, Wang Q, Li Z, Wang P, Wu J, Zuo M, Liu Z. Removing the Obstacle of Dye-Sensitized Upconversion Luminescence in Aqueous Phase to Achieve High-Contrast Deep Imaging In Vivo. Adv Funct Mater. 2020;30:1910765.
Wang Q, Liang T, Wu J, Li Z, Liu Z. Dye-Sensitized Rare Earth-Doped Nanoparticles with Boosted NIR-IIb Emission for Dynamic Imaging of Vascular Network-Related Disorders. ACS Appl Mater Interfaces. 2021;13:29303–12.
Li Z, Wu J, Wang Q, Liang T, Ge J, Wang P, Liu Z. A universal strategy to construct lanthanide-doped nanoparticles-based activable NIR-II luminescence probe for bioimaging. Iscience 2020, 23.
Xie X, Gao N, Deng R, Sun Q, Xu Q-H, Liu X. Mechanistic Investigation of Photon Upconversion in Nd3+-Sensitized Core–Shell Nanoparticles. J Am Chem Soc. 2013;135:12608–11.
Wang Y-F, Liu G-Y, Sun L-D, Xiao J-W, Zhou J-C, Yan C-H. Nd3+-Sensitized Upconversion Nanophosphors: Efficient In Vivo Bioimaging Probes with Minimized Heating Effect. ACS Nano. 2013;7:7200–6.
Chen X, Peng D, Ju Q, Wang F. Photon upconversion in core–shell nanoparticles. Chem Soc Rev. 2015;44:1318–30.
Hao S, Chen G, Yang C, Shao W, Wei W, Liu Y, Prasad PN. Nd3+-Sensitized multicolor upconversion luminescence from a sandwiched core/shell/shell nanostructure. Nanoscale. 2017;9:10633–8.
Zuo J, Sun D, Tu L, Wu Y, Cao Y, Xue B, Zhang Y, Chang Y, Liu X, Kong X, et al. Precisely Tailoring Upconversion Dynamics via Energy Migration in Core–Shell Nanostructures. Angew Chem Int Ed. 2018;57:3054–8.
Wang T, Zhou H, Yu Z, Zhou G, Zhou J, Huang D, Sun L, Gao P, Sun Y, Hu J. 808 nm Excited Multicolor Upconversion Tuning through Energy Migration in Core–Shell–Shell Nanoarchitecture. J Phys Chem C. 2018;122:10113–24.
Fan Y, Liu L, Zhang F. Exploiting lanthanide-doped upconversion nanoparticles with core/shell structures. Nano Today. 2019;25:68–84.
Zhang X, Chen W, Xie X, Li Y, Chen D, Chao Z, Liu C, Ma H, Liu Y, Ju H. Boosting Luminance Energy Transfer Efficiency in Upconversion Nanoparticles with an Energy-Concentrating Zone. Angew Chem Int Ed. 2019;58:12117–22.
Lin S-L, Chang CA. Optimising FRET-efficiency of Nd3+-sensitised upconversion nanocomposites by shortening the emitter–photosensitizer distance. Nanoscale. 2020;12:8742–9.
Lin S-L, Chen H-C, Chang CA. Enhancing Förster Resonance Energy Transfer (FRET) Efficiency of Titania–Lanthanide Hybrid Upconversion Nanomaterials by Shortening the Donor–Acceptor Distance. Nanomaterials. 2020;10:2035.
Ren J, Ding Y, Zhu H, Li Z, Dai R, Zhao H, Hong X, Zhang H. Emitter-Active Shell in NaYF4:Yb,Er/NaYF4:Er Upconversion Nanoparticles for Enhanced Energy Transfer in Photodynamic Therapy. ACS Appl Nano Mater. 2022;5:559–68.
Pilch-Wrobel A, Kotulska AM, Lahtinen S, Soukka T, Bednarkiewicz A. Engineering the Compositional Architecture of Core-Shell Upconverting Lanthanide-Doped Nanoparticles for Optimal Luminescent Donor in Resonance Energy Transfer: The Effects of Energy Migration and Storage. Small. 2022;18:2200464.
Gao D, Luo Z, He Y, Yang L, Hu D, Liang Y, Zheng H, Liu X, Sheng Z. Low-Dose NIR-II Preclinical Bioimaging Using Liposome-Encapsulated Cyanine Dyes (Small 17/2023). Small. 2023;19:2370116.
Jia R, Xu H, Wang C, Su L, Jing J, Xu S, Zhou Y, Sun W, Song J, Chen X, Chen H. NIR-II emissive AIEgen photosensitizers enable ultrasensitive imaging-guided surgery and phototherapy to fully inhibit orthotopic hepatic tumors. J Nanobiotechnol. 2021;19:419.

Scheme 1 is available in the Supplementary Files section.

No competing interests reported.

20240815RENP783SI.docx
Additional file 1: Experimental section and supporting figures associated with this article can be found in the online version.
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Graphical abstract
floatimage2.png
Scheme 1 Illustration of the proposed near-Infrared IIb (NIR IIb) imaging agent, referred to as the onion-like Nd-RENP nanocomplex, designed to enhance the brightness and photostable NIR-IIb in vivo 3D imaging.

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Enhanced brightness and photostability dye-sensitized Nd-doped rare earth nanocomplex for in vivo NIR-IIb vascular and orthotopic tumor imaging

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Abstract

Figures

Background

Results and Discussion

Synthesis and characterization of RENPs

Luminescent Spectral Characterization of RENPs

Surface Modification and Dye-Encapsulation onto Onion-Like Nd-RENPs

NIR-II Imaging Test in tubes and phantoms

NIR-II Imaging test in tubes and phantoms

Photostability test of onion-like Nd-RENPs nanocomplex

Temporal dynamics of luminescent agents in murine model

NIR-IIb imaging in different murine models using onion-like Nd-RENPs nanocomplex

Time-dependent NIR-IIb imaging of normal mice and tumor-bearing mice using onion-like Nd-RENPs nanocomplex

Conclusion

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References

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Additional Declarations

Supplementary Files

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