Lanthanide-doped Upconversion Nanoparticles Research Articles

Lanthanide-Sensitized Upconversion Iridium Complex via Triplet Energy Transfer.

Cyclometalated iridium (Ir) complexes demonstrate impressive capabilities across a range of fields, including biology and photocatalysis, due to their tunable optical characteristics and structure flexibility. However, generating upconversion luminescence of Ir complexes under near-infrared light excitation is challenging. Herein, by employing lanthanide-doped upconversion nanoparticles (UCNPs) as the sensitizer, a new strategy is demonstrated to gain upconversion luminescence of Ir complexes via triplet energy transfer. This design relies on a rationally designed hybrid of core-shell structured NaYbF4:Tb@NaTbF4 UCNPs and new Ir phosphonate complexes, in which UCNPs can migrate upconverted energy to the surface of nanoparticles through Tb3+-mediated energy migration and then sensitize the upconversion luminescence of Ir complexes upon 980nm excitation. Both experimental and theoretical investigations highlight the significance of triplet energy transfer from excited Tb3+ ions to the triplet state of Ir complexes in the sensitization of upconversion luminescence of Ir complexes. These findings may open exciting avenues for fabricating hybrid Ir materials with new functions and driving the development of UCNP-based nanomaterials.

Numerical demonstration of an efficient up-conversion enhancement strategy by plasmon excitations in a gap-mode nanocavity

Lanthanide-doped up-conversion nanoparticles (UCNPs) can be widely used as near-infrared absorbing photoactive materials in bioimaging and photovoltaic devices. However, the low absorption cross section and low luminescence quantum rate of UCNPs significantly limit its use. Therefore, a hexagonal gold pillar nano-array structure consisting of UCNPs, gold pillar arrays, gold film and silica layer is proposed. By optimizing the structural parameters, the surface plasmon resonance wavelengths are simultaneously matched with the 808 nm excitation wavelength and 450 nm emission wavelength of the UCNPs. The gap-mode nanocavity confines the incident excitation radiation to nanophotonic hotspots with greatly high field strengths, thus theoretically proposed an efficient strategy to enhance the up-conversion luminescence. The plasmonic structure investigated in this study combines the advantages of ease of processing, high absorption, low loss and good controllability of its localized surface plasmon resonance. It provides a new solution for up-conversion enhancement design of gap-mode nanocavities.

Tumor-associated antigen-specific cell imaging based on upconversion luminescence and nucleic acid rolling circle amplification.

Tumor-associated antigen (TAA)-based diagnosis has gained prominence for early tumor screening, treatment monitoring, prognostic assessment, and minimal residual disease detection. However, limitations such as low sensitivity and difficulty in extracting non-specific binding membrane proteins still exist in traditional detection methods. Upconversion luminescence (UCL) exhibits unique physical and chemical properties under wavelength near-infrared light excitation. Rolling circle amplification (RCA) is an efficient DNA amplification technique with amplification factorsas high as 105. Therefore, the above two excellent techniques can be employed for highly accurate imaging analysis of tumor cells. Herein, we developed a novel nanoplatform for TAA-specific cell imaging based on UCL and RCA technology. An aptamer-primer complex selectively binds to Mucin 1 (MUC1), one of TAA on cell surface, to trigger RCA reaction, generating a large number of repetitive sequences. These sequences provide lots of binding sites for complementary signal probes, producing UCL from lanthanide-doped upconversion nanoparticles (UCNPs) after releasing quencher group. The experimental results demonstrate the specific attachment of upconversion nanomaterials to cancer cells which express a high level of MUC1, indicating the potential of UCNPs and RCA in tumor imaging.

Upconversion Nanoparticles Based Sensing: From Design to Point-of-Care Testing.

Rare earth-doped upconversion nanoparticles (UCNPs) have achieved a wide range of applications in the sensing field due to their unique anti-Stokes luminescence property, minimized background interference, excellent biocompatibility, and stable physicochemical properties. However, UCNPs-based sensing platforms still face several challenges, including inherent limitations from UCNPs such as low quantum yields and narrow absorption cross-sections, as well as constraints related to energy transfer efficiencies in sensing systems. Therefore, the construction of high-performance UCNPs-based sensing platforms is an important cornerstone for conducting relevant research. This work begins by providing a brief overview of the upconversion luminescence mechanism in UCNPs. Subsequently, it offers a comprehensive summary of the sensors' types, design principles, and optimized design strategies for UCNPs sensing platforms. More cost-effective and promising point-of-care testing applications implemented based on UCNPs sensing systems are also summarized. Finally, this work addresses the future challenges and prospects for UCNPs-based sensing platforms.

Effect of Surface Modification on the Luminescence of Individual Upconversion Nanoparticles.

Lanthanide-doped upconversion nanoparticles (UCNPs) hold promise for single-molecule imaging owing to their excellent photostability and minimal autofluorescence. However, their limited water dispersibility, often from the hydrophobic oleic acid ligand during synthesis, is a challenge. To address this, various surface modification strategies' impact on single-particle upconversion luminescence are studied. UCNPs are made hydrophilic through methods like ligand exchange with dye IR806, HCl or NOBF4 treatment, silica coating (SiO2 or mesoporous mSiO2 ), and self-assembly with polymer of DSPE-PEG or F127. The studies revealed that UCNPs modified with NOBF4 and DSPE-PEG exhibited notably higher single-particle brightness with minimal quenching (3% and 8%, respectively), followed by SiO2 , F127, IR806, mSiO2 , and HCl (84% quenching). HCl disrupted UCNPs's crystal lattice, weakening luminescence, while mSiO2 absorbed solvent molecules, causing luminescence quenching. Energy transfer to IR806 also reduced the brightness. Additionally, a prevalence of upconversion red emission over green is observed, with the red-to-green ratio increasing with irradiance. UCNPs coated with DSPE-PEG exhibited the brightest single-particle luminescence in water, retaining 48% of its original emission due to a lower critical micelle concentration and superior water protection. In summary, the investigation provides valuable insights into the role of surface chemistry on UCNPs at the single-particle level.

Efficient monodisperse upconversion composite prepared using high-density local field and its dual-mode temperature sensing.

Enhanced upconversion via plasmonics has considerable potential in biosensors and solar cells; however, conventional plasmonic configurations such as core-shell assemblies or nanoarray platforms still suffer from the compromise between the enhancement factor and monodispersity, which has failed to meet the requirement of the materials for the in vivo all-solution-prepared solar cells and biosensors. We herein report a monodisperse metal-dielectric-metal (MDM) type upconverted hybrid material with high efficiency. The lanthanide-doped upconversion nanoparticles (UCNPs) were sandwiched by two gold nanodisk mirrors, and the highly localized excitation field around the UCNPs together with the efficient coupling enhanced the upconversion. The upconversion intensity can then be effectively regulated and improved by three to four orders of magnitude. As per the measurement of the temperature-dependent fluorescence intensity and spectra shift, a dual-mode nanothermometer based on our proposed hybrid materials was demonstrated. This MDM-type upconverted hybrid material demonstrated the merits of high efficiency and monodispersity, which demonstrated promise in in vivo biosensors and solar cell fabrication techniques such as spin-coating and roll-to-roll.

Effect of the temperature on the luminescence profile of photonic materials for biological applications

Temperature has a significant impact on the luminescence profile of photonic materials for biological applications. This paper presents the effect of temperature on the luminescence profile of three different photonic materials in the range of the second biological window. The effect of temperature on luminescence properties is shown on glass, glass-ceramics, and phosphors co-doped with Eu3+/Nd3+/Yb3+ under UV laser diode excitation. Each sample has been analyzed for temperature effects on optical parameters in biological window ranges. Moreover the effect of temperature on mechanisms of energy transfer Eu3+ → Nd3+ → Yb3+ in all fabricated photonic materials was analyzed. Full Text: PDF References J. Zhou, J.L. Leano Jr., Z. Liu, D. Jin, K.-L. Wong et al., "Impact of Lanthanide Nanomaterials on Photonic Devices and Smart Applications", Small 14, 1801882 (2018). CrossRef Z. Li, Y. Zhang, G. Han, "Lanthanide-Doped Upconversion Nanoparticles for Imaging-Guided Drug Delivery and Therapy", Springer Series in Biomaterials Science and Engineering 6, 139 (2016). CrossRef A. Zhang, Z. Sun, M.Jia, et al., "Simultaneous luminescence in Ⅰ, Ⅱ and III biological windows realized by using the energy transfer of Yb3+→Er3+/Ho3+→Cr3+", Chemical Engineering Journal 365, 400 (2019). CrossRef M.-F. Tsai, S.-H.G. Chang, F.-Y. Cheng, V. Shanmugam, Y. Cheng et al., "Au Nanorod Design as Light-Absorber in the First and Second Biological Near-Infrared Windows for in Vivo Photothermal Therapy", ACS Nano 7, 5330 (2013). CrossRef S. Ding, L. Lu, Y. Fan, F. Zhang, "Recent progress in NIR-II emitting lanthanide-based nanoparticles and their biological applications", J. Rare Earth. 38, 451 (2020). CrossRef U. Rocha, K.U. Kumar, C. Jacinto, I. Villa, F. Sanz-Rodriguez et al., "Neodymium-Doped LaF3 Nanoparticles for Fluorescence Bioimaging in the Second Biological Window", Small 10, 1141 (2014). CrossRef M. Jia, Z. Sun, H. Xu, X. Jin, Z. Lv et al. "An ultrasensitive luminescent nanothermometer in the first biological window based on phonon-assisted thermal enhancing and thermal quenching", J. Mater. Chem. C 8, 15603 (2020). CrossRef H. Lin, T. Hu, Y. Cheng, M. Chen, Y. Wang, "Glass Ceramic Phosphors: Towards Long-Lifetime High-Power White Light-Emitting-Diode Applications–A Review", Laser Photonic Rev. 12, 1700344 (2018). CrossRef H. Su, Y. Nie, H. Yang, D. Tang, K. Chen, T. Zhang, "Improving the thermal stability of phosphor in a white light-emitting diode (LED) by glass-ceramics: Effect of Al2O3 dopant", J. Eur. Ceram. Soc. 38, 2005 (2018). CrossRef Kenry, Y.Duan, B. Liu, "Recent Advances of Optical Imaging in the Second Near-Infrared Window", Adv. Mater. 30, 1802394 (2018). CrossRef M.L. Debasu, H. Oliveira, J. Rocha, L.D. Carlos, "Colloidal (Gd0.98Nd0.02)2O3 nanothermometers operating in a cell culture medium within the first and second biological windows", J. Rare Earth. 38, 483-491 (2020). CrossRef L. Pavasaryte, A. Katelnikovas, V. Klimavicius, V. Balevicius, A. Krajnc et al., "Eu3+-Doped Y3−xNdxAl3O12 garnet: synthesis and structural investigation", Phys. Chem. Chem. Phys. 19, 3729 (2017). CrossRef K. Sadowska, P. Awramiuk, I Zgłobicka, K Rećko, J. Żmojda, "Quantum efficiency of europium doped LaPO4 phosphors for UV sensing applications", Photonics Lett. Poland 14, 28 (2022). CrossRef P. Lei, J. Feng, H. Zhang, "Emerging biomaterials: Taking full advantage of the intrinsic properties of rare earth elements", Nano Today 35, 100952 (2020). CrossRef K. Sadowska, T. Ragiń, M. Kochanowicz, P. Miluski, J. Dorosz, et al., "Analysis of Excitation Energy Transfer in LaPO4 Nanophosphors Co-Doped with Eu3+/Nd3+ and Eu3+/Nd3+/Yb3+ Ions", Materials 16, 1588 (2023). CrossRef

Near-infrared-responsive nanoplatforms integrating dye-sensitized upconversion and heavy-atom effect for enhanced photodynamic therapy efficacy

The development of near-infrared (NIR)-responsive upconversion nanoplatforms for photodynamic therapy (PDT) has attracted considerable attention in recent years, but is still limited by the low PDT efficacy. Herein, we designed and synthesized a NIR-responsive nanoplatform through the integration of lanthanide-doped upconversion nanoparticles (UCNPs), Pt-decorated porphyrin metal-organic frameworks (PMOFs) and NIR dye IR808 into a core-shell structure for highly efficient antibacterial PDT. The PMOF shell can function not only as a photosensitizer to absorb the upconversion luminescence (UCL) of UCNPs for singlet oxygen (1O2) generation, but also as a porous host material for loading of IR808. Remarkably, we demonstrated that the heavy-atom effect of Pt(II) can simultaneously enhance the intersystem crossing (S1→T1) efficiencies of the IR808 and the porphyrin ligand Pt-TCPP, resulting in the enhancement of dye-triplet-sensitized UCL of UCNPs and 1O2 production capacity of the photosensitizer. As a result, the proposed nanoplatform exhibited excellent 1O2 production and a significant bactericidal activity against methicillin-resistant Staphylococcus aureus (MRSA) with 5.27 log10 (> 99.999%) killing efficacy. These findings will pave the way for designing highly efficient PDT nanoplatforms and accelerate their biomedical applications.

Excitation pulse width-dependent luminescence decay of lanthanide-doped upconversion nanoparticles

Upconversion luminescence decay, a key feature of lanthanide-doped upconversion nanoparticles (UCNPs) that is crucial for both the fundamental studies and practical applications of UCNPs, typically is obtained under pulsed excitation. However, little attention has been paid to the influence of pulsed excitation on the luminescence decay of UCNPs. Herein, using NaYF4:Yb/Er (5/2 mol%) UCNPs as an archetype, we show that the luminescence decay of UCNPs can be largely affected by the excitation pulse width. With the increase of excitation pulse width, the lifetime, derived from the luminescence decay, can increase by ∼100 %. Our experimental studies, together with numerical simulations, reveal that the excitation pulse width-dependent luminescence decay can be due to the presence of luminescent centers with multi-decay properties in UCNPs. These results can pave new ways to the modulation of upconversion luminescence decay and offer new opportunities for the application of UCNPs in the temporal domain.

Flexible composite film with enhanced upconversion emission for ultrasensitive gas detection

Lanthanide-doped upconversion nanoparticles (UCNPs) were found promising in photovoltaic devices and nanoscale sensing due to their excellent optical properties. However, the low quantum yields severely limit their practical applications. In this work, we reported the enhanced upconversion emission by near-field modulation on all dielectric interfaces. The flexible polystyrene (PS) sphere array @UCNPs composite was fabricated by self-assembly and the NIR excitation can be highly localized and amplified in the array with proper sphere size, thus promoting the upconversion process. Based on this efficient upconversion composite film, the sensing performance on acetic acid gas were discussed in detail. The good linear relationship between the upconversion luminescence intensity and acetic acid concentration can be achieved with a detection limit of 5.2 ppm at room temperature, which is comparable with the best level reported so far. In addition, such optical signal-based sensors possessed other unique advantages such as easy fabrication, high sensitivity, long-term stability, reusability and flexibility. And the fluorescence signal enhancement factor showed less dependence on the excitation power and can emit effectively at low pump power. This all dielectric fluorescent composite with high efficiency and sensing performance can be helpful in biosensor and flexible security label applications.

Ratiometric upconversion luminescence sensing platform for visual monitoring of antiarrhythmic drug level in serum

Arrhythmia seriously threatens life and health, it requires long-term use of antiarrhythmic drugs such as mexiletine and needs to monitor the dosage of drugs in the body to ensure efficacy and avoid serious side effects. Here, we designed a sensing platform for real-time visual monitoring of drug efficacy using a ratiometric upconversion probe, which overcomes the fluorescence background interference in the serum, and improves the resolution and accuracy of visual detection. By combining lanthanide-doped upconversion nanoparticles (UCNPs) with readily available organic dyes, an efficient upconversion nanoprobe was constructed under the reaction mechanism of internal filtration effect (IFE) to realize the quantitative detection of mexiletine in serum. Due to the addition of mexiletine, the characteristic emission peak of the probe at 540 nm changes, while the fluorescence intensity at 655 nm is unchanged. Therefore, the visual detection of mexiletine in serum is realized according to the fluorescence intensity changes of I540/I655. In addition, the designed sensing platform is combined with a smartphone to realize real-time visualization and quantitative monitoring of mexiletine, and the detection limits in fluorescence and colorimetric modes are as low as 55.6 nM and 469.75 nM respectively, consequently resulting in sensitive monitoring the effective dosage of drugs in the serum. The proposed detection platform provides a new sensing strategy for the visual determination of antiarrhythmic drugs and an instant device to warn the treatment process of the disease immediately.

Dual-band polarized upconversion photoluminescence enhanced by resonant dielectric metasurfaces

Lanthanide-doped upconversion nanoparticles emerged recently as an attractive material platform underpinning a broad range of innovative applications such as optical cryptography, luminescent probes, and lasing. However, the intricate 4f-associated electronic transition in upconversion nanoparticles leads only to a weak photoluminescence intensity and unpolarized emission, hindering many applications that demand ultrabright and polarized light sources. Here, we present an effective strategy for achieving ultrabright and dual-band polarized upconversion photoluminescence. We employ resonant dielectric metasurfaces supporting high-quality resonant modes at dual upconversion bands enabling two-order-of-magnitude amplification of upconversion emissions. We demonstrate that dual-band resonances can be selectively switched on polarization, endowing cross-polarization controlled upconversion luminescence with ultra-high degrees of polarization, reaching approximately 0.86 and 0.91 at dual emission wavelengths of 540 and 660 nm, respectively. Our strategy offers an effective approach for enhancing photon upconversion processes paving the way towards efficient low-threshold polarization upconversion lasers.

Improving dispersibility of lanthanide-doped upconversion nanoparticles for luminescence applications in medium polarity solvents

The dispersibility of lanthanide-doped upconversion nanoparticles (UCNPs) is related to the polarity of solvents. Typically, the as-synthesized UCNPs are poorly dispersed in medium and high polarity solvents. Here, we investigated the dispersibility of oleate-capped UCNPs in different solvents and improved the dispersibility of the nanoparticles in medium polarity solvents by a ligand exchange process. 2-naphthoxyacetic acid and α-hydroxyhippuric acid were selected as ligands to improve the dispersion of UCNPs in long-chain alcohol and ester solvents, respectively. The improvement of dispersibility was confirmed by dynamic light scattering measurements and transmission electron microscope images. In parallel, the luminescence features of the UCNPs dispersed in different solvents were measured to understand the influence of solvents on the luminescence lifetime, red-green emission ratio and power dependent properties of UCNPs. Additionally, the ligand exchange rendered an improved dispersibility of UCNPs in medium polarity media, which prevented aggregation of UCNPs in polydimethylsiloxane (PDMS) matrix improving transmittance of UCNPs-polydimethylsiloxane (PDMS). This study provides an effective method to improve the dispersion of UCNPs in organic polymer media expanding the applicability of nanoparticles in displays and anticounterfeiting.

Pre-activated nanoparticles with persistent luminescence for deep tumor photodynamic therapy in gallbladder cancer

Phototherapy of deep tumors still suffers from many obstacles, such as limited near-infrared (NIR) tissue penetration depth and low accumulation efficiency within the target sites. Herein, stimuli-sensitive tumor-targeted photodynamic nanoparticles (STPNs) with persistent luminescence for the treatment of deep tumors are reported. Purpurin 18 (Pu18), a porphyrin derivative, is utilized as a photosensitizer to produce persistent luminescence in STPNs, while lanthanide-doped upconversion nanoparticles (UCNPs) exhibit bioimaging properties and possess high photostability that can enhance photosensitizer efficacy. STPNs are initially stimulated by NIR irradiation before intravenous administration and accumulate at the tumor site to enter the cells through the HER2 receptor. Due to Pu18 afterglow luminescence properties, STPNs can continuously generate ROS to inhibit NFκB nuclear translocation, leading to tumor cell apoptosis. Moreover, STPNs can be used for diagnostic purposes through MRI and intraoperative NIR navigation. STPNs exceptional antitumor properties combined the advantages of UCNPs and persistent luminescence, representing a promising phototherapeutic strategy for deep tumors.

Plasmon modulated luminescent modes of upconversion nanoparticle by coupling with AuNR@SiO2 nanostructure

Lanthanide-doped upconversion nanoparticles (UCNPs) can convert near-infrared light into visible light emission, and have attracted more and more interests due to their great potential in ultrasensitive biosensors. However, it is still a huge challenge to manipulate the intensity ratio between different emission lines and realize the modulated up-conversion. In this work, the upconversion luminescence performance of UCNPs was regulated by coupling with Au nanorod-silicon core–shell (AuNR@SiO2) nanostructures. By changing the thickness and surface charge of the silica shell, the influence of the thickness and surface charge on the energy transfer of the UCNPs was explored. It is expected that the up-conversion luminescence effect of this composite nanostructure regulated by plasmons can provide a basis for the extensive exploration of biological detection and sensing applications.

Tm3+-doped upconversion nanoparticles water probing

Water probing based on lanthanide-doped upconversion nanoparticles (UCNPs) has aroused great interest due to the advantages of high photostability, short response time, no autofluorescence background, and low toxicity. Compared with widely used Er3+-doped UCNPs, Tm3+-doped UCNPs are not considered as efficient water probes due to the phonon energy mismatch. Here, we demonstrate the water probing based on Tm3+-doped UCNPs with excellent sensitivity and linearity, and reveal that the fractional photon-assisted Förster resonance energy transfer could play a significant role in the mechanism. The recorded sensitivities of up to 6.141%/vol% and 3.932%/vol% were achieved for the hydrogen oxide and deuterium oxide detection. Based on the developed UCNPs, we developed two sensing devices, namely, an UCNPs-coated micro-fiber and UCNPs-embedded silk, for distributed and wearable humidity sensing. Our study opens an unprecedented avenue to develop real-time, high-sensitivity, high-stability, biocompatible water probes serving the fields of cytobiology, pharmaceutics, environmental health and safety, fine chemical industry, and precision agriculture.

Self-assembled ratiometric sensor for specific detection of hypoxia in living cells based on lanthanide-doped upconversion nanoparticles and gold nanoparticles

We describes the development of a self-assembled nanoprobe for ratiometric sensing of hypoxia in living cells. The probe, UC-AuNPs, is composed of azo-functionalized upconversion nanoparticles (azo-UCNPs) and gold nanoparticles functionalized with β-cyclodextrin (CD-AuNPs). Under hypoxic conditions, reductases reduce azo derivatives on the UCNPs, leading to detachment of the CD-AuNPs and subsequent fluorescence recovery of the green emission. The ratiometric measurement incorporated into the strategy reduces the impact of external factors and improves sensitivity of the probe. The use of NIR excitation effectively minimizes interference from strong luminescence backgrounds in biosystems. The UC-AuNPs nanoprobe is able to effectively sense and monitor hypoxia conditions in living cells and has the potential to distinguish hypoxia-related diseases from healthy tissue, making it a valuable tool for early clinical diagnosis.

Enhanced upconversion of sub20 nm core/shell/shell nanophosphors for temperature and rhodamine B sensing

Lanthanide-doped upconversion (UC) nanoparticles (NPs) have attracted great attention in many emerging applications. Although multilayer structures have been employed to strengthen UC intensity, balancing the energy transfer (ET) efficiency from sensitizer to activator as well as the back energy transfer (BET) efficiency remains a critical issue. Herein, the ET processes in the BaYF5-based core/shell/shell NPs are comprehensively manipulated, resulting in greatly enhanced UC intensity. By using the sub20 nm BaYF5:2Yb2Er@BaYbF5@BaYF5 nanostructure, the efficiencies of incident light absorption and ET from the sensitizer in the interlayer to the activator in the core are improved, while the BET is limited. The UC intensity of this nanostructure was approximately 3.7 times that of normal BaYF5:20Yb2Er@BaYF5 NPs. The isolation of Yb and Er can remarkably restrict the negative thermal quenching (NTQ) effect, resulting in improved temperature sensing performance. Moreover, the BaYF5:2Yb2Er@BaYbF5@BaYF5 NPs can be used for selective sensing of rhodamine B. Our results highlight the comprehensive manipulation of ET processes in a core/shell/shell nanostructure to significantly improve the UC intensity.

Activating ultralow upconversion nanothermometry in neodymium sublattice for heart tissue imaging rapid-responsive

The fields of biosensitivity and biological imaging have received a lot of attention from rare earth-doped upconversion nanoparticles (UCNPs). However, owing to the relatively large energy difference of rare earth ions, biological sensitivity based on UCNPs is restricted to detect at low temperature. Here, we design core-shell-shell NaErF4:Yb@Nd2O3@SiO2 UCNPs as a dual-mode bioprobe that produces blue, green, and red multi-color upconversion emissions at extremely low temperatures between 100 K and 280 K. Based on the thermally coupled energy levels (TCELs) of Er3+ (2H11/2 and 4S3/2) and Nd3+ (4F5/2 and 4F3/2) at 100 K, the greatest relative sensitivity (SR) approaches 12.7% K−1. NaErF4:Yb@Nd2O3@SiO2 injection is used to achieve blue upconversion emission imaging of frozen heart tissue, showing that this UCNP can serve as a low-temperature sensitive biological fluorescence.

Biomimetic Upconversion Nanoplatform Synergizes Photodynamic Therapy and Enhanced Radiotherapy against Tumor Metastasis.

The easy recurrence and high metastasis of fatal tumors require the development of a combination therapy, which is able to overcome the drawbacks of monomodal strategies such as surgery, photodynamic therapy (PDT), and radiotherapy (RT). Taking the complementary advantages of PDT and RT, we present herein the integration of lanthanide-doped upconversion nanoparticles (UCNPs) with chlorin e6 (Ce6)-imbedded RBC membrane vesicles as a near-infrared-induced PDT agent for achieving synchronous depth PDT and RT with reduced radiation exposure. In such a nanoagent, gadolinium-doped UCNPs with strong X-ray attenuation ability act not only as a light transductor to activate the loaded photosensitizer Ce6 to allow PDT but also as a radiosensitizer to enhance RT. PDT with enhanced low-dose RT can achieve synergistic inhibition of tumor growth by producing reactive oxygen species to destroy local tumor cells and inducing strong T-cell-dependent immunogenic cell death to arrest systemic cancer metastasis. This combination of PDT and RT might be a potential appealing strategy for tumor eradication.