Europium-Doped Nanoparticles for Cellular Luminescence Lifetime Imaging via Multiple Manipulations of Aggregation State

Modulating the Photoluminescence of Europium through Crystalline Assembly Formation with Gold Nanoclusters and Then Phosphate Ions

We report delayed fluorescence enhancement of europium (Eu3+) ions through complexation with ligand-stabilized gold nanoclusters (Au NCs). The different Eu3+-centric emissions following complexation with Au NCs exhibited selective augmentation in the spectral lines attributed to the 5D0 → 7FJ transitions. The photoluminescence (PL) properties, including delayed Eu emission, from each component could be modulated through further functionalization of phosphate ions (Pi), leading to crystallization. The assembled crystalline structure of europium-containing Au NCs (Eu Au NCs) was corroborated by selected area electron diffraction analyses and high-resolution transmission electron microscopy analyses. On the basis of PL measurements and other experimental evidence, the two different lifetimes arising from the components, prompt emission of Au NCs and delayed emission of Eu3+, were affected in the assembled nanostructure. Such a design offers the possibility of developing an optical system by conjugating molecular NCs and atomic luminescent probes that has potential uses.

Beyond Extracellular Vesicles: Hybrid Membrane Nanovesicles as Emerging Advanced Tools for Biomedical Applications

Extracellular vesicles (EVs), involved in essential physiological and pathological processes of the organism, have emerged as powerful tools for disease treatment owing to their unique natural biological characteristics and artificially acquired advantages. However, the limited targeting ability, insufficient production yield, and low drug-loading capability of natural simplex EVs have greatly hindered their development in clinical translation. Therefore, the establishment of multifunctional hybrid membrane nanovesicles (HMNVs) with favorable adaptability and flexibility has become the key to expanding the practical application of EVs. This timely review summarizes the current progress of HMNVs for biomedical applications. Different HMNVs preparation strategies including physical, chemical, and chimera approaches are first discussed. This review then individually describes the diverse types of HMNVs based on homologous or heterologous cell membrane substances, a fusion of cell membrane and liposome, as well as a fusion of cell membrane and bacterial membrane. Subsequently, a specific emphasis is placed on the highlight of biological applications of the HMNVs toward various diseases with representative examples. Finally, ongoing challenges and prospects of the currently developed HMNVs in clinical translational applications are briefly presented. This review will not only stimulate broad interest among researchers from diverse disciplines but also provide valuable insights for the development of promising nanoplatforms in precision medicine.

Pure Organic AIE Nanoscintillator for X-ray Mediated Type I and Type II Photodynamic Therapy

X-ray induced photodynamic therapy (X-PDT) circumvents the poor penetration depth of conventional PDT with minimal radio-resistance generation. However, conventional X-PDT typically requires inorganic scintillators as energy transducers to excite neighboring photosensitizers (PSs) to generate reactive oxygen species (ROS). Herein, a pure organic aggregation-induced emission (AIE) nanoscintillator (TBDCR NPs) that can massively generate both type I and type II ROS under direct X-ray irradiation is reported for hypoxia-tolerant X-PDT. Heteroatoms are introduced to enhance X-ray harvesting and ROS generation ability, and AIE-active TBDCR exhibits aggregation-enhanced ROS especially less oxygen-dependent hydroxyl radical (HO•- , type I) generation ability. TBDCR NPs with a distinctive PEG crystalline shell to provide a rigid intraparticle microenvironment show further enhanced ROS generation. Intriguingly, TBDCR NPs show bright near-infrared fluorescence and massive singlet oxygen and HO•- generation under direct X-ray irradiation, which demonstrate excellent antitumor X-PDT performance both in vitro and in vivo. To the best of knowledge, this is the first pure organic PS capable of generating both 1 O2 and radicals (HO•- ) in response to direct X-ray irradiation, which shall provide new insights for designing organic scintillators with excellent X-ray harvesting and predominant free radical generation for efficient X-PDT.

Near-Infrared Thermally Activated Delayed Fluorescence Nanoparticle: A Metal-Free Photosensitizer for Two-Photon-Activated Photodynamic Therapy at the Cell and Small Animal Levels

Thermally activated delayed fluorescence (TADF) materials with extremely small singlet-triplet energy offsets have opened new horizons for the development of metal-free photosensitizers for photodynamic therapy (PDT) in recent years. However, the exploration of near-infrared (NIR) TADF emitters for efficient two-photon-excited (TPE) PDT is still a formidable challenge, thus it has not been reported yet. In this study, purely organic photosensitizers (PSs) based on the TADF nanoparticles (NIR-TADF NPs) are designed for efficient TPE-PDT, which show excellent singlet oxygen generation ability. Thanks to the intrinsic two-photon excitation and NIR emission characteristics, the NIR-TADF NPs demonstrate promising potential in both single-photon-excited (SPE) and TPE NIR imaging. More importantly, the anti-tumor efficiency and biosafety of TADF-based PSs at the small animal level are confirmed in A549 tumor xenograft models under TPE laser irradiance, which will facilitate the practical biomedical applications of TADF materials. This work not only provides a promising strategy to develop metal-free PSs, but also expands the applied scope of TADF-based nanotherapeutics and advances their possible clinical translation in cancer therapy.

Thermally Activated Delayed Fluorescence Material: An Emerging Class of Metal-Free Luminophores for Biomedical Applications

The development of simple, efficient, and biocompatible organic luminescent molecules is of great significance to the clinical transformation of biomaterials. In recent years, purely organic thermally activated delayed fluorescence (TADF) materials with an extremely small single-triplet energy gap (ΔEST ) have been considered as the most promising new-generation electroluminescence emitters, which is an enormous breakthrough in organic optoelectronics. By merits of the unique photophysical properties, high structure flexibility, and reduced health risks, such metal-free TADF luminophores have attracted tremendous attention in biomedical fields, including conventional fluorescence imaging, time-resolved imaging and sensing, and photodynamic therapy. However, there is currently no systematic summary of the TADF materials for biomedical applications, which is presented in this review. Besides a brief introduction of the major developments of TADF material, the typical TADF mechanisms and fundamental principles on design strategies of TADF molecules and nanomaterials are subsequently described. Importantly, a specific emphasis is placed on the discussion of TADF materials for various biomedical applications. Finally, the authors make a forecast of the remaining challenges and future developments. This review provides insightful perspectives and clear prospects towards the rapid development of TADF materials in biomedicine, which will be highly valuable to exploit new luminescent materials.

Synthesis of water-soluble europium-containing nanoprobes via polymerization-induced self-assembly and their cellular imaging applications

Lanthanide nanoprobes have attracted extensive attention for applications in cellular imaging and biological sensing. Herein, water-dispersible europium (III)-based (Eu(III)-based) nanoprobes were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of hydrophobic monomers (Eu(III)-containing monomer and methyl methacrylate (MMA)) using hydrophilic macro-chain transfer agent poly(PEGMA)-CTA. The resulted poly(PMEu) nanoprobes showed spherical in shape in good monodispersity with average diameters of around 210 nm. The poly(PMEu) nanoprobles excellent aqueous dispersity, high aqueous stability and good luminescence properties with quantum yields of 37.21% and fluorescence lifetime of 312.4 μs. Moreover, the poly(PMEu) nanoprobes exhibited good cellular biocompatibility with cell viabilities of 88.2% and high fluorescence intensity for in vitro cellular imaging. The present approach provides a facile strategy for fabrication of luminescent Eu(III)-based nanoprobes with great potential applications for biological imaging.

Europium(iii)-containing nanohydrogels for cellular imaging and drug delivery applications

By employing the excellent luminescence of Eu(iii) complexes and the versatility of nanohydrogels, Eu(iii)-containing nanohydrogels were prepared as a potential theranostic nanoplatform for cancer therapy.

Self-Assembled Organic Nanomaterials for Drug Delivery, Bioimaging, and Cancer Therapy

Over the past few decades, tremendous progress has been made in the development of engineering nanomaterials, which opened new horizons in the field of diagnosis and treatment of various diseases. In particular, self-assembled organic nanomaterials with intriguing features including delicate structure tailoring, facile processability, low cost, and excellent biocompatibility have shown outstanding potential in biomedical applications because of the enhanced permeability and retention (EPR) effect and multifunctional properties. In this review, we briefly introduce distinctive merits of self-assembled organic nanomaterials for biomedical applications. The main focus will be placed on summarizing recent advances in self-assembled organic nanomedicine for drug delivery, bioimaging, and cancer phototherapy, followed by highlighting a critical perspective on further development of self-assembled organic nanomaterials for future clinical translation. We believe that the above themes will appeal to researchers from different fields, including material, chemical, and biological sciences, as well as pharmaceutics.