Ultrabright Terbium Nanoparticles for FRET Biosensing and in Situ Imaging of Epidermal Growth Factor Receptors**

Boosting Excited-State Energy Transfer by Anchoring Dipole Orientation in Binary Thermally Activated Delayed Fluorescence/J-Aggregate Assemblies

Förster resonance energy transfer (FRET) has been widely applied in fluorescence imaging, sensing and so on, while developing useful strategy of boosting FRET efficiency becomes a key issue that limits the application. Except optimizing spectral properties, promoting orientation factor (κ2) has been well discussed but rarely utilized for boosting FRET. Herein, we constructed binary nano-assembling of two thermally activated delayed fluorescence (TADF) emitters (2CzPN and DMAC-DPS) with J-type aggregate of cyanine dye (C8S4) as doping films by taking advantage of their electrostatic interactions. Time-resolved spectroscopic measurements indicated that 2CzPN/Cy-J films exhibit an order of magnitude higher kFRET than DMAC-DPS/Cy-J films. Further quantitative analysing on kFRET and kDET indicated higher orientation factor (κ2) in 2CzPN/Cy-J films play a key role for achieving fast kFRET, which was subsequently confirmed by anisotropic measurements. Corresponding DFT/TDDFT calculation revealed strong "two-point" electrostatic anchoring in 2CzPN/Cy-J films that is responsible for highly orientated transitions. We provide a new strategy for boosting FRET in nano-assemblies, which might be inspired for designing FRET-based devices of sensing, imaging and information encryption.

Pro-angiogenic Terbium Hydroxide Nanorods Improve Critical Limb Ischemia in Part by Amelioration of Ischemia-Induced Endothelial Injury

Critical limb ischemia (CLI) refers to a severe condition resulting from gradual obstruction in the supply of blood, oxygen, and nutrients to the limbs. The most promising clinical solution to CLI is therapeutic angiogenesis. This study explored the potency of pro-angiogenic terbium hydroxide nanorods (THNR) for treatment of CLI, with a major focus on their impact on ischemia-induced maladaptive alterations in endothelial cells as well as on vascularization in ischemic limbs. This study demonstrated that, in hypoxia-exposed endothelial cells, THNR improve survival and promote proliferation, migration, restoration of nitric oxide production, and regulation of vascular permeability. Based on molecular studies, these attributes of THNR can be traced to the stimulation of PI3K/AKT/eNOS signaling pathways. Besides, Wnt/GSK-3β/β-catenin signaling pathways may also play a role in the therapeutic actions of THNR. Furthermore, in the murine model of CLI, THNR administration can integrally re-establish blood perfusion with concomitant reduction of muscle damage and inflammation. Additionally, improvement of locomotor activities and motor coordination in ischemic limbs in THNR treated mice is also evident. Overall, the study demonstrates that THNR have the potential to be developed as an efficacious and cost-effective alternative clinical therapy for CLI, using a nanomedicine approach.

Potential Biomedical Applications of Terbium-Based Nanoparticles (TbNPs): A Review on Recent Advancement

The scientific world is increasingly focusing on rare earth metal oxide nanomaterials due to their consequential biological prospects, navigated by breakthroughs in biomedical applications. Terbium belongs to rare earth elements (lanthanide series) and possesses remarkably strong luminescence at lower energy emission and signal transduction properties, ushering in wide applications for diagnostic measurements (i.e., bioimaging, biosensors, fluorescence imaging, etc.) in the biomedical sectors. In addition, the theranostic applications of terbium-based nanoparticles further permit the targeted delivery of drugs to the specific site of the disease. Furthermore, the antimicrobial properties of terbium nanoparticles induced via reactive oxygen species (ROS) cause oxidative damage to the cell membrane and nuclei of living organisms, ion release, and surface charge interaction, thus further creating or exhibiting excellent antioxidant characteristics. Moreover, the recent applications of terbium nanoparticles in tissue engineering, wound healing, anticancer activity, etc., due to angiogenesis, cell proliferation, promotion of growth factors, biocompatibility, cytotoxicity mitigation, and anti-inflammatory potentials, make this nanoparticle anticipate a future epoch of nanomaterials. Terbium nanoparticles stand as a game changer in the realm of biomedical research, proffering a wide array of possibilities, from revolutionary imaging techniques to advanced drug delivery systems. Their unique properties, including luminescence, magnetic characteristics, and biocompatibility, have redefined the boundaries of what can be achieved in biomedicine. This review primarily delves into various mechanisms involved in biomedical applications via terbium-based nanoparticles due to their physicochemical characteristics. This review article further explains the potential biomedical applications of terbium nanoparticles with in-depth significant mechanisms from the individual literature. This review additionally stands as the first instance to furnish a "single-platted" comprehensive acquaintance of terbium nanoparticles in shaping the future of healthcare as well as potential limitations and overcoming strategies that require exploration before being trialed in clinical settings.

Three species multiplexing of fluorescent dyes and gold nanoclusters recovered with fluorescence lifetime correlation spectroscopy

Biosensor applications often require the simultaneous detection of multiple analytes, with a clear need to go beyond the traditional multiplexing relying on distinct fluorescent dyes across the visible spectrum. Fluorescence lifetime correlation spectroscopy (FLCS) is a powerful approach taking advantage of the fluorescence lifetime information to separate the contributions of different fluorescent species with overlapping emission spectra. However, so far FLCS detection has been demonstrated only on binary mixtures of two fluorescent dyes, limiting its multiplexing capabilities. Here, we report the first quantitative FLCS measurements within a ternary mixture composed of three different fluorescent emitters with near-identical emission spectra. Two organic fluorescent dyes, Alexa Fluor 647 and CF640R, are combined with water-soluble Au18(SG)14 gold nanoclusters. Our experimental data establish that FLCS allows to accurately determine individual concentrations within intricate ternary mixtures. Another major aspect of interest concerns the assessment of the suitability of gold nanoclusters for FLCS multiplexing applications. With their microsecond lifetime and stable emission characteristics, gold nanoclusters add a valuable new aspect to the array of FLCS probes. Extending FLCS multiplexing beyond binary mixtures paves the way for further progress in the simultaneous highly parallel biosensing of multiple species.

Molecular mapping of neuronal architecture using STORM microscopy and new fluorescent probes for SMLM imaging

Imaging neuronal architecture has been a recurrent challenge over the years, and the localization of synaptic proteins is a frequent challenge in neuroscience. To quantitatively detect and analyze the structure of synapses, we recently developed free SODA software to detect the association of pre and postsynaptic proteins. To fully take advantage of spatial distribution analysis in complex cells, such as neurons, we also selected some new dyes for plasma membrane labeling. Using Icy SODA plugin, we could detect and analyze synaptic association in both conventional and single molecule localization microscopy, giving access to a molecular map at the nanoscale level. To replace those molecular distributions within the neuronal three-dimensional (3D) shape, we used MemBright probes and 3D STORM analysis to decipher the entire 3D shape of various dendritic spine types at the single-molecule resolution level. We report here the example of synaptic proteins within neuronal mask, but these tools have a broader spectrum of interest since they can be used whatever the proteins or the cellular type. Altogether with SODA plugin, MemBright probes thus provide the perfect toolkit to decipher a nanometric molecular map of proteins within a 3D cellular context.

Therapeutic potentials of terbium hydroxide nanorods for amelioration of hypoxia-reperfusion injury in cardiomyocytes

Myocardial hypoxia reperfusion (H/R) injury is the paradoxical exacerbation of myocardial damage, caused by the sudden restoration of blood flow to hypoxia affected myocardium. It is a critical contributor of acute myocardial infarction, which can lead to cardiac failure. Despite the current pharmacological advancements, clinical translation of cardioprotective therapies have proven challenging. As a result, researchers are looking for alternative approaches to counter the disease. In this regard, nanotechnology, with its versatile applications in biology and medicine, can confer broad prospects for treatment of myocardial H/R injury. Herein, we attempted to explore whether a well-established pro-angiogenic nanoparticle, terbium hydroxide nanorods (THNR) can ameliorate myocardial H/R injury. For this study, in vitro H/R-injury model was established in rat cardiomyocytes (H9c2 cells). Our investigations demonstrated that THNR enhance cardiomyocyte survival against H/R-induced cell death. This pro-survival effect of THNR is associated with reduction of oxidative stress, lipid peroxidation, calcium overload, restoration of cytoskeletal integrity and mitochondrial membrane potential as well as augmentation of cellular anti-oxidant enzymes such as glutathione-s-transferase (GST) and superoxide dismutase (SOD) to counter H/R injury. Molecular analysis revealed that the above observations are traceable to the predominant activation of PI3K-AKT-mTOR and ERK-MEK signalling pathways by THNR. Concurrently, THNR also exhibit apoptosis inhibitory effects mainly by suppression of pro-apoptotic proteins like Cytochrome C, Caspase 3, Bax and p53 with simultaneous restoration of anti-apoptotic protein, Bcl-2 and Survivin. Thus, considering the above attributes, we firmly believe that THNR have the potential to be developed as an alternative approach for amelioration of H/R injury in cardiomyocytes.

Dye-sensitized lanthanide containing nanoparticles for luminescence based applications

Due to their exceptional luminescent properties, lanthanide (Ln) complexes represent a unique palette of probes in the spectroscopic toolkit. Their extremely weak brightness due to forbidden Ln electronic transitions can be overcome by indirect dye-sensitization from the antenna effect brought by organic ligands. Despite the improvement brought by the antenna effect, (bio)analytical applications with discrete Ln complexes as luminescent markers still suffers from low sensitivity as they are limited by the complex brightness. Thus, there is a need to develop nano-objects that cumulate the spectroscopic properties of multiple Ln ions. This review firstly gives a brief introduction of the spectral properties of lanthanides both in complexes and in nanoparticles (NPs). Then, the research progress of the design of Ln-doped inorganic NPs with capping antennas, Ln-complex encapsulated NPs and Ln-complex surface functionalized NPs is presented along with a summary of the various photosensitizing ligands and of the spectroscopic properties (excited-state lifetime, brightness, quantum yield). The review also emphasizes the problems and limitations encountered over the years and the solutions provided to address them. Finally, a comparison of the advantages and drawbacks of the three types of NP is provided as well as a conclusion about the remaining challenges both in the design of brighter NPs and in the luminescence based applications.

A Tb3+ functionalized triazine-porous organic framework as a ratiometric fluorescent sensor for determination of ciprofloxacin in aquatic products

A Tb3+ functionalized triazine-porous organic framework (Tb3+/TAPOF) was prepared by introducing Tb3+ into a triazine-porous organic framework through a coordination bond.

Biomedical Applications of Lanthanide Nanomaterials, for Imaging, Sensing and Therapy

The application of nanomaterials made of rare earth elements within biomedical sciences continues to make significant progress. The rare earth elements, also called the lanthanides, play an essential role in modern life through materials and electronics. As we learn more about their utility, function, and underlying physics, we can contemplate extending their applications to biomedicine. This particularly applies to diagnosis and radiation therapy due to their relatively unique features, such as an ultra-wide Stokes shift in the luminescence, variable magnetism and potentially tunable properties, due to the library of lanthanides available and their multivalent oxidation state chemistry. The ability to prepare nanomaterials of relatively smaller sizes has increased the likelihood of use in vivo. In this review, we summarize the different emerging applications of nanoparticles with rare earth elements as the host or doped elements for biomedical applications in the past three to four years, especially in the area of imaging and disease diagnosis. Researchers have made progress in utilizing surfactants and polymers to modify the surface of lanthanide nanoparticles to enhance biocompatibility. At the same time, specific antibodies and proteins can also be conjugated to these nanoparticles to increase targeting efficiency for specific tumor models. Finally, in the near-infrared II imaging window, lanthanide nanoparticles have been shown to exhibit extraordinary bright emission, which is an exciting development for image-guided surgery.

Switching to the brighter lane: pathways to boost the absorption of lanthanide-doped nanoparticles

Lanthanide-doped nanoparticles (LNPs) are speedily colonizing several research fields, such as biological (multimodal) imaging, photodynamic therapy, volumetric encoding displays, and photovoltaics. Yet, the electronic transitions of lanthanide ions obey the Laporte rule, which dramatically hampers their light absorption capabilities. As a result, the brightness of these species is severely restricted. This intrinsic poor absorption capability is the fundamental obstacle for untapping the full potential of LNPs in several of the aforementioned fields. Among others, three of the most promising physicochemical approaches that have arisen during last two decades to face the challenges of increasing LNP absorption are plasmonic enhancement, organic-dye sensitization, and coupling with semiconductors. The fundamental basis, remarkable highlights, and comparative achievements of each of these pathways for absorption enhancement are critically discussed in this minireview, which also includes a detailed discussion of the exciting perspectives ahead.

Enhancing FRET biosensing beyond 10 nm with photon avalanche nanoparticles

Förster Resonance Energy Transfer (FRET) between donor (D) and acceptor (A) molecules is a phenomenon commonly exploited to study or visualize biological interactions at the molecular level. However, commonly used organic D and A molecules often suffer from photobleaching and spectral bleed-through, and their spectral properties hinder quantitative analysis. Lanthanide-doped upconverting nanoparticles (UCNPs) as alternative D species offer significant improvements in terms of photostability, spectral purity and background-free luminescence detection, but they bring new challenges related to multiple donor ions existing in a single large size UCNP and the need for nanoparticle biofunctionalization. Considering the relatively short Förster distance (typically below 5-7 nm), it becomes a non-trivial task to assure sufficiently strong D-A interaction, which translates directly to the sensitivity of such bio-sensors. In this work we propose a solution to these issues, which employs the photon avalanche (PA) phenomenon in lanthanide-doped materials. Using theoretical modelling, we predict that these PA systems would be highly susceptible to the presence of A and that the estimated sensitivity range extends to distances 2 to 4 times longer (i.e. 10-25 nm) than those typically found in conventional FRET systems. This promises high sensitivity, low background and spectral or temporal biosensing, and provides the basis for a radically novel approach to combine luminescence imaging and self-normalized bio-molecular interaction sensing.