Targeted, Molecular Europium(III) Probes Enable Luminescence-Guided Surgery and 1 Photon Post-Surgical Luminescence Microscopy of Solid Tumors

A Lanthanide Nanoparticle-Aggregation-Induced Emission Photosensitizer Complex System Drives Coupled Triplet Energy Transfer for Enhanced Radio-Photodynamic Therapy

Cerenkov light (CL), utilized as an internal excitation source for photodynamic therapy (PDT), addresses the limitations of laser penetration and has substantial potential for seamlessly integrating clinical radiotheranostics with phototheranostics. Nevertheless, the effectiveness of CL-mediated PDT is significantly hindered by challenges, such as the low intensity of CL and inadequate energy transfer between the CL donor and photosensitizers (PSs). In this study, a novel approach is introduced for enhanced radionuclide-activated radio-photodynamic therapy utilizing a hybrid nanoparticle system composed of lanthanide nanoparticles and an aggregation-induced emission photosensitizer (AIE PS), designated LnNP-TQ NPs. This system enables lanthanide nanoparticles to optimize the decay energy of radionuclides, effectively sensitizing the AIE PS through triplet energy transfer (TET)-mediated processes with an efficiency approaching 100%. When activated by the clinical radionuclide 18F for positron emission tomography imaging, the LnNP-TQ NPs substantially inhibited tumor growth via effective singlet oxygen (1O2) generation. This strategy, which optimally harnesses radionuclide energy and achieves efficient energy transfer, offers a promising pathway for enhancing radiotherapy-phototherapy efficacy in tumor treatment.

Metal-Assisted Synthesis of Extended Polyaromatic Nitrogen-Rich Ligands for Tunable Sensitization of Eu(III) Complexes

We report the metal-assisted synthesis of oligomeric nitrogen-rich DiL1 and PoL1n sensitizers from the monomer L1 via acyclic diene metathesis (ADMET) polymerization for the tuning of the photoluminescence properties of europium-containing complexes by ligand design. The binding of [Eu(hfac)3] cargoes (H-hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) to monomer L1 to give [L1Eu(hfac)3] during metathesis appeared to be essential (i) for protecting the Grubbs ruthenium catalyst to interact with the nitrogen atoms of L1 and (ii) to drive the Ru-catalyzed ADMET reaction toward dimeric {DiL1[Eu(hfac)3]2} and polymeric {PoL1n[Eu(hfac)3]n} assemblies. Compared with the monomeric tridentate L1-L4 ligands, significant electronic delocalization occurs through the π-conjugated benzimidazole-CH═CH-benzimidazole skeletons in the dimer DiL1 and polymers PoL1n, which results in a stepwise red-shift of the excited levels in these extended polyaromatic ligands. As a consequence, the sensitization of bound [Eu(hfac)3] units reveals a decrease of the photoluminescence quantum yields along the [L4Eu(hfac)3] > [L3Eu(hfac)3] > [L2Eu(hfac)3] ≈ [L1Eu(hfac)3] > {DiL1[Eu(hfac)3]2} > {PoL118[Eu(hfac)3]18} series due to unfavorable europium-to-ligand back energy transfers.

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

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

Smart Cancer-Targeting and Super-Sensitive Sensing of Eu3+/Tb3+-Induced Hyaluronan Characteristic Nano-Micelles with Effective Drug Loading and Release

To avoid the critical problems of effective drugs not being carried to their targeted cancers and their quantity and location not being sensed in situ, this work presents a completely new innovative strategy to achieve both smart cancer targeting (SCT) and super-sensitive sensing (SSS), where one drug carrier works for effective drug loading and release. Herein, malignant melanoma treatment is used as an example of reliable detection and effective therapy. We report two characteristic dumbbell-like nano-micelles and spherical-like nano-micelles of hyaluronan induced by the Eu3+/Tb3+ complexes for effective drug loading and release, respectively. These special Eu3+/Tb3+-loaded nano-micelles (marked as ENM and TNM) have strong and sharp red/green luminescence that can sensitively detect the malignant melanoma drug dacarbazine through changes in fluorescence intensity. Cytotoxicity experiments confirmed that both ENM and TNM are not toxic to normal cells at very high concentrations of 4 mM. However, when loaded with cancer drugs (D-ENM and D-ENM), they both killed cancer cells with more than 40% efficacy at this concentration. The in vivo experiments confirmed that D-ENM and D-TNM can effectively target cancer cells in tissue and effectively impede cancer growth. The detection limits of ENM and TNM in sensing cancer drugs can reach 0.456 μg/mL and 0.139 μg/mL, respectively. Therefore, the reported Eu3+/Tb3+-induced hyaluronan nano-micelles (ENM and TNM) are distinguished carriers of this cancer drug and excellent in situ sensors, and they have highly therapeutic effects with extremely low toxicity to normal cells.

The Current Status and Future Directions on Nanoparticles for Tumor Molecular Imaging

Molecular imaging is an advanced technology that utilizes specific probes or markers in conjunction with cutting-edge imaging techniques to observe and analyze the localization, distribution, activity, and interactions of biomolecules within living organisms. Tumor molecular imaging, by enabling the visualization and quantification of molecular characteristics of tumor cells, facilitates a deeper and more comprehensive understanding of tumors, providing valuable insights for early diagnosis, treatment monitoring, and cancer biology research. However, the image quality of molecular imaging still requires improvement, and nanotechnology has significantly propelled the advancement of molecular imaging. Currently, nanoparticle-based tumor molecular imaging technologies encompass radionuclide imaging, fluorescence imaging, magnetic resonance imaging, ultrasound imaging, photoacoustic imaging, and multimodal imaging, among others. As our understanding of the tumor microenvironment deepens, the design of nanoparticle probes for tumor molecular imaging has also evolved, offering new perspectives and expanding the applications of tumor molecular imaging. Beyond diagnostics, there is a marked trend towards integrated diagnosis and therapy, with image-guided treatment playing a pivotal role. This includes image-guided surgery, photodynamic therapy, and chemodynamic therapy. Despite continuous advancements and innovative developments in molecular imaging, many of these remain in the experimental stage and require breakthroughs before they can be fully integrated into clinical practice.

Current Development of Lanthanide Complexes for Biomedical Applications

Luminescent molecule-based bioimaging system is widely used for precise localization and distinction of cancer/tumor cells. Luminescent lanthanide (Ln(III)) complexes offer long-lived (sub-millisecond time scale) and sharp (FWHM <10 nm) emission, arising from the forbidden 4f-4f electronic transitions. Luminescent Ln(III) complex-based bioimaging has emerged as a promising option for both in vitro and in vivo visualizations. In this mini-review, the historical development and recent significant progress of luminescent Ln(III) probes for bioapplications are introduced. The recent studies are mainly focused on three points: (i) the structural modifications of Ln(III) complexes in both macrocyclic and small ligands, (ii) the acquirement of high resolution luminescence images of cancer/tumor cells and (iii) the constructions of ratiometric biosensors. Furthermore, our recent study is explained as a new Cancer GPS (cancer grade probing for determining tumor grade through photophysical property analyses of intracellular Eu(III) complex.