Fluorescent Polymer Nanoparticles Based on Dyes: Seeking Brighter Tools for Bioimaging

To see or not to see: In vivo nanocarrier detection methods in the brain and their challenges

Nanoparticles have a great potential to significantly improve the delivery of therapeutics to the brain and may also be equipped with properties to investigate brain function. The brain, being a highly complex organ shielded by selective barriers, requires its own specialized detection system. However, a significant hurdle to achieve these goals is still the identification of individual nanoparticles within the brain with sufficient cellular, subcellular, and temporal resolution. This review aims to provide a comprehensive summary of the current knowledge on detection systems for tracking nanoparticles across the blood-brain barrier and within the brain. We discuss commonly employed in vivo and ex vivo nanoparticle identification and quantification methods, as well as various imaging modalities able to detect nanoparticles in the brain. Advantages and weaknesses of these modalities as well as the biological factors that must be considered when interpreting results obtained through nanotechnologies are summarized. Finally, we critically evaluate the prevailing limitations of existing technologies and explore potential solutions.

Exciton annihilation and diffusion length in disordered multichromophoric nanoparticles

Efficient exciton transport is the essential property of natural and synthetic light-harvesting (LH) devices. Here we investigate exciton transport properties in LH organic polymer nanoparticles (ONPs) of 40 nm diameter. The ONPs are loaded with a rhodamine B dye derivative and bulky counterion, enabling dye loadings as high as 0.3 M, while preserving fluorescence quantum yields larger than 30%. We use time-resolved fluorescence spectroscopy to monitor exciton-exciton annihilation (EEA) kinetics within the ONPs dispersed in water. We demonstrate that unlike the common practice for photoluminescence investigations of EEA, the non-uniform intensity profile of the excitation light pulse must be taken into account to analyse reliably intensity-dependent population dynamics. Alternatively, a simple confocal detection scheme is demonstrated, which enables (i) retrieving the correct value for the bimolecular EEA rate which would otherwise be underestimated by a typical factor of three, and (ii) revealing minor EEA by-products otherwise unnoticed. Considering the ONPs as homogeneous rigid solutions of weakly interacting dyes, we postulate an incoherent exciton hoping mechanism to infer a diffusion constant exceeding 0.003 cm2 s-1 and a diffusion length as large as 70 nm. This work demonstrates the success of the present ONP design strategy at engineering efficient exciton transport in disordered multichromophoric systems.

Photophysics of fluorescent nanoparticles based on organic dyes - challenges and design principles

Fluorescent nanoparticles have become attractive for bioanalysis and imaging, due to their high brightness and photostability. Many different optical materials have been applied in fluorescent nanoparticles with a broad range of properties and characteristics. One appealing approach is the incorporation of molecular organic fluorophores in nanoparticles with the intention of transferring their known attractive solution-state properties directly to the nanoparticles. However, as molecular dyes are packed closely together in the nanoparticles their interactions most often result in fluorescence quenching and change in spectral properties making this approach challenging. In this perspective we will first discuss the origins of quenching and spectral shifts observed in dye based nanoparticles. On this background, we will then describe various designs of dye based NPs and how they address the challenges of dye-dye interactions and quenching. Our aim is to provide a general framework for understanding the supramolecular mechanisms that determine the photophysics of dye based nanoparticles. This framework of molecular photophysics and its relation to the internal structure of dye based nanoparticles can hopefully serve to assist rational design and optimization of new and improved dye based nanoparticles.

Nanomaterial-Based Strategies for Attenuating T-Cell-Mediated Immunodepression in Stroke Patients: Advancing Research Perspectives

This review article discusses the potential of nanomaterials in targeted therapy and immunomodulation for stroke-induced immunosuppression. Although nanomaterials have been extensively studied in various biomedical applications, their specific use in studying and addressing immunosuppression after stroke remains limited. Stroke-induced neuroinflammation is characterized by T-cell-mediated immunodepression, which leads to increased morbidity and mortality. Key observations related to immunodepression after stroke, including lymphopenia, T-cell dysfunction, regulatory T-cell imbalance, and cytokine dysregulation, are discussed. Nanomaterials, such as liposomes, micelles, polymeric nanoparticles, and dendrimers, offer advantages in the precise delivery of drugs to T cells, enabling enhanced targeting and controlled release of immunomodulatory agents. These nanomaterials have the potential to modulate T-cell function, promote neuroregeneration, and restore immune responses, providing new avenues for stroke treatment. However, challenges related to biocompatibility, stability, scalability, and clinical translation need to be addressed. Future research efforts should focus on comprehensive studies to validate the efficacy and safety of nanomaterial-based interventions targeting T cells in stroke-induced immunosuppression. Collaborative interdisciplinary approaches are necessary to advance the field and translate these innovative strategies into clinical practice, ultimately improving stroke outcomes and patient care.

Magnetic Silica-Coated Fluorescent Microspheres (MagSiGlow) for Simultaneous Detection of Tumor-Associated Proteins

Multiplexed bead assays for solution-phase biosensing often encounter cross-over reactions during signal amplification steps, leading to unwanted false positive and high background signals. Current solutions involve complex custom-designed and costly equipment, limiting their application in simple laboratory setup. In this study, we introduce a straightforward protocol to adapt a multiplexed single-bead assay to standard fluorescence imaging plates, enabling the simultaneous analysis of thousands of reactions per plate. This approach focuses on the design and synthesis of bright fluorescent and magnetic microspheres (MagSiGlow) with multiple fluorescent wavelengths serving as unique detection markers. The imaging-based, single-bead assay, combined with a scripted algorithm, allows the detection, segmentation, and co-localization on average of 7500 microspheres per field of view across five imaging channels in less than one second. We demonstrate the effectiveness of this method with remarkable sensitivity at low protein detection limits (100 pg/mL). This technique showed over 85 % reduction in signal cross-over to the solution-based method after the concurrent detection of tumor-associated protein biomarkers. This approach holds the promise of substantially enhancing high throughput biosensing for multiple targets, seamlessly integrating with rapid image analysis algorithms.

Expanding the Palette of SWIR Emitting Nanoparticles Based on Au Nanoclusters for Single-Particle Tracking Microscopy

Single-molecule localization microscopy has proved promising to unravel the dynamics and molecular architecture of thin biological samples down to nanoscales. For applications in complex, thick biological tissues shifting single-particle emission wavelengths to the shortwave infrared (SWIR also called NIR II) region between 900 to 2100 nm, where biological tissues are more transparent is key. To date, mainly single-walled carbon nanotubes (SWCNTs) enable such applications, but they are inherently 1D objects. Here, 0D ultra-small luminescent gold nanoclusters (AuNCs, <3 nm) and ≈25 nm AuNC-loaded-polymeric particles that can be detected at the single-particle level in the SWIR are presented. Thanks to high brightness and excellent photostability, it is shown that the dynamics of the spherical polymeric particles can be followed at the single-particle level in solution at video rates for minutes. We compared single particle tracking of AuNC-loaded-polymeric particles with that of SWCNT diffusing in agarose gels demonstrating the specificity and complementarity of diffusion properties of these SWIR-emitting nano-objects when exploring a complex environment. This extends the library of photostable SWIR emitting nanomaterials to 0D nano-objects of variable size for single-molecule localization microscopy in the second biological window, opening unprecedented possibilities for mapping the structure and dynamics of complex biological systems.

Magneto-optical nanosystems for tumor multimodal imaging and therapy in-vivo

Multimodal imaging, which combines the strengths of two or more imaging modalities to provide complementary anatomical and molecular information, has emerged as a robust technology for enhancing diagnostic sensitivity and accuracy, as well as improving treatment monitoring. Moreover, the application of multimodal imaging in guiding precision tumor treatment can prevent under- or over-treatment, thereby maximizing the benefits for tumor patients. In recent years, several intriguing magneto-optical nanosystems with both magnetic and optical properties have been developed, leading to significant breakthroughs in the field of multimodal imaging and image-guided tumor therapy. These advancements pave the way for precise tumor medicine. This review summarizes various types of magneto-optical nanosystems developed recently and describes their applications as probes for multimodal imaging and agents for image-guided therapeutic interventions. Finally, future research and development prospects of magneto-optical nanosystems are discussed along with an outlook on their further applications in the biomedical field.

Supra-Fluorophores: Ultrabright Fluorescent Supramolecular Assemblies Derived from Conventional Fluorophores in Water

Fluorescent organic nanoparticles (NPs) with exceptional brightness hold significant promise for demanding fluorescence bioimaging applications. Although considerable efforts are invested in developing novel organic dyes with enhanced performance, augmenting the brightness of conventional fluorophores is still one of the biggest challenges to overcome. This study presents a supramolecular strategy for constructing ultrabright fluorescent nanoparticles in aqueous media (referred to as "Supra-fluorophores") derived from conventional fluorophores. To achieve this, this course has employed a cylindrical nanoparticle with a hydrophobic microdomain, assembled by a cyclic peptide-diblock copolymer conjugate in water, as a supramolecular scaffold. The noncovalent dispersion of fluorophore moieties within the hydrophobic microdomain of the scaffold effectively mitigates the undesired aggregation-caused quenching and fluorescence quenching by water, resulting in fluorescent NPs with high brightness. This strategy is applicable to a broad spectrum of fluorophore families, covering polyaromatic hydrocarbons, coumarins, boron-dipyrromethenes, cyanines, xanthenes, and squaraines. The resulting fluorescent NPs demonstrate high fluorescence quantum yield (>30%) and brightness per volume (as high as 12 060 m-1 cm-1 nm-3). Moreover, high-performance NPs with emission in the NIR region are constructed, showcasing up to 20-fold increase in both brightness and photostability. This Supra-fluorophore strategy offers a versatile and effective method for transforming existing fluorophores into ultrabright fluorescent NPs in aqueous environments, for applications such as bioimaging.

Self-Assembled DNA Nanospheres Driven by Carbon Dots for MicroRNAs Imaging in Tumor via Logic Circuit

DNA nanostructures with diverse biological functions have made significant advancements in biomedical applications. However, a universal strategy for the efficient production of DNA nanostructures is still lacking. In this work, a facile and mild method is presented for self-assembling polyethylenimine-modified carbon dots (PEI-CDs) and DNA into nanospheres called CANs at room temperature. This makes CANs universally applicable to multiple biological applications involving various types of DNA. Due to the ultra-small size and strong cationic charge of PEI-CDs, CANs exhibit a dense structure with high loading capacity for encapsulated DNA while providing excellent stability by protecting DNA from enzymatic hydrolysis. Additionally, Mg2+ is incorporated into CANs to form Mg@CANs which enriches the performance of CANs and enables subsequent biological imaging applications by providing exogenous Mg2+. Especially, a DNAzyme logic gate system that contains AND and OR Mg@CANs is constructed and successfully delivered to tumor cells in vitro and in vivo. They can be specifically activated by endogenic human apurinic/apyrimidinic endonuclease 1 and recognize the expression levels of miRNA-21 and miRNA-155 at tumor sites by logic biocomputing. A versatile pattern for delivery of diverse DNA and flexible logic circuits for multiple miRNAs imaging are developed.

Semiconducting polymer dots for multifunctional integrated nanomedicine carriers

The expansion applications of semiconducting polymer dots (Pdots) among optical nanomaterial field have long posed a challenge for researchers, promoting their intelligent application in multifunctional nano-imaging systems and integrated nanomedicine carriers for diagnosis and treatment. Despite notable progress, several inadequacies still persist in the field of Pdots, including the development of simplified near-infrared (NIR) optical nanoprobes, elucidation of their inherent biological behavior, and integration of information processing and nanotechnology into biomedical applications. This review aims to comprehensively elucidate the current status of Pdots as a classical nanophotonic material by discussing its advantages and limitations in terms of biocompatibility, adaptability to microenvironments in vivo, etc. Multifunctional integration and surface chemistry play crucial roles in realizing the intelligent application of Pdots. Information visualization based on their optical and physicochemical properties is pivotal for achieving detection, sensing, and labeling probes. Therefore, we have refined the underlying mechanisms and constructed multiple comprehensive original mechanism summaries to establish a benchmark. Additionally, we have explored the cross-linking interactions between Pdots and nanomedicine, potential yet complete biological metabolic pathways, future research directions, and innovative solutions for integrating diagnosis and treatment strategies. This review presents the possible expectations and valuable insights for advancing Pdots, specifically from chemical, medical, and photophysical practitioners' standpoints.

Potentiating Immunogenic Cell Death in Cold Tumor with Functional Living Materials of FeAu-Methylene Blue Composites

Low immunogenicity, absence of tumor-infiltrating lymphocytes and immunosuppressive microenvironment of immune cold tumors are the main bottlenecks leading to unfavorable prognosis. Here, an integrated tumor bioimaging and multimodal therapeutic strategy is developed, which converts immune cold into hot by modulating oxidative stress levels, enhancing photo-killing efficacy, inducing immunogenic cell death and inhibiting the immune checkpoint. On that occasion, the unique tumor microenvironment can be harnessed to biosynthesize in situ self-assembly iron complexes and fluorescent gold nanoclusters from metal ions Fe(II) and Au(III) for active targeting and real-time visualization of the tumors, simultaneously regulating reactive oxygen species levels within tumors via peroxidase-like activity. Furthermore, methylene blue (MB)-mediated photodynamic therapy promotes the release of damage-associated molecular patterns (DAMPs), which acts as in situ tumor vaccine and further induces dendritic cells maturation, augments the infiltration of antitumor T cells and significantly impedes the primary tumor growth and proliferation. More strikingly, by synergizing with the programmed cell death receptor-1 (PD-1) checkpoint inhibitor, the immunosuppressive microenvironment is remodeled and the survival time of model mice is prolonged. In summary, this paradigm utilizes the tumor-specific microenvironment to boost robust and durable systemic antitumor immunity, providing a novel opportunity for precision cancer theranostics.

Sensing, Imaging, and Therapeutic Strategies Endowing by Conjugate Polymers for Precision Medicine

Conjugated polymers (CPs) have promising applications in biomedical fields, such as disease monitoring, real-time imaging diagnosis, and disease treatment. As a promising luminescent material with tunable emission, high brightness and excellent stability, CPs are widely used as fluorescent probes in biological detection and imaging. Rational molecular design and structural optimization have broadened absorption/emission range of CPs, which are more conductive for disease diagnosis and precision therapy. This review provides a comprehensive overview of recent advances in the application of CPs, aiming to elucidate their structural and functional relationships. The fluorescence properties of CPs and the mechanism of detection signal amplification are first discussed, followed by an elucidation of their emerging applications in biological detection. Subsequently, CPs-based imaging systems and therapeutic strategies are illustrated systematically. Finally, recent advancements in utilizing CPs as electroactive materials for bioelectronic devices are also investigated. Moreover, the challenges and outlooks of CPs for precision medicine are discussed. Through this systematic review, it is hoped to highlight the frontier progress of CPs and promote new breakthroughs in fundamental research and clinical transformation.

Interlaboratory Comparison on Absolute Photoluminescence Quantum Yield Measurements of Solid Light Converting Phosphors with Three Commercial Integrating Sphere Setups

Scattering luminescent materials dispersed in liquid and solid matrices and luminescent powders are increasingly relevant for fundamental research and industry. Examples are luminescent nano- and microparticles and phosphors of different compositions in various matrices or incorporated into ceramics with applications in energy conversion, solid-state lighting, medical diagnostics, and security barcoding. The key parameter to characterize the performance of these materials is the photoluminescence/fluorescence quantum yield (Φf), i.e., the number of emitted photons per number of absorbed photons. To identify and quantify the sources of uncertainty of absolute measurements of Φf of scattering samples, the first interlaboratory comparison (ILC) of three laboratories from academia and industry was performed by following identical measurement protocols. Thereby, two types of commercial stand-alone integrating sphere setups with different illumination and detection geometries were utilized for measuring the Φf of transparent and scattering dye solutions and solid phosphors, namely, YAG:Ce optoceramics of varying surface roughness, used as converter materials for blue light emitting diodes. Special emphasis was dedicated to the influence of the measurement geometry, the optical properties of the blank utilized to determine the number of photons of the incident excitation light absorbed by the sample, and the sample-specific surface roughness. While the Φf values of the liquid samples matched between instruments, Φf measurements of the optoceramics with different blanks revealed substantial differences. The ILC results underline the importance of the measurement geometry, sample position, and blank for reliable Φf data of scattering the YAG:Ce optoceramics, with the blank's optical properties accounting for uncertainties exceeding 20%.

Ultrabright Dibenzofluoran-Based Polymer Dots with NIR-IIa Emission Maxima and Unusual Large Stokes Shifts for 3D Rotational Stereo Imaging

Emerging organic molecules with emissions in the second near-infrared (NIR-II) region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR-IIa (1300 nm) region faces challenges due to the intrinsic energy gap law. Up to the current stage, all reported organic NIR-IIa emitters belong to polymethine-based dyes with small Stokes shifts (<50 nm) and low quantum yield (QY; ≤0.015%). However, such polymethines have proved to cause self-absorption with constrained emission brightness, limiting advanced development in deep-tissue imaging. Here a new NIR-IIa scaffold based on rigid and highly conjugated dibenzofluoran core terminated by amino-containing moieties that reveal emission peaks of 1230-1305 nm is designed. The QY is at least 10 times higher than all synthesized or reported NIR-IIa polymethines with extraordinarily large Stokes shifts of 370-446 nm. DBF-BJ is further prepared as a polymer dot to demonstrate its in vivo 3D stereo imaging of mouse vasculature with a 1400 nm long-pass filter.

Control of the fluorescence lifetime in dye based nanoparticles

Fluorescent dye based nanoparticles (NPs) have received increased interest due to their high brightness and stability. In fluorescence microscopy and assays, high signal to background ratios and multiple channels of detection are highly coveted. To this end, time-resolved imaging offers suppression of background and temporal separation of spectrally overlapping signals. Although dye based NPs and time-resolved imaging are widely used individually, the combination of the two is uncommon. This is likely due to that dye based NPs in general display shortened and non-mono-exponential lifetimes. The lower quality of the lifetime signal from dyes in NPs is caused by aggregation caused quenching (ACQ) and energy migration to dark states in NPs. Here, we report a solution to this problem by the use of the small-molecule ionic isolation lattices (SMILES) concept to prevent ACQ. Additionally, incorporation of FRET pairs of dyes locks the exciton on the FRET acceptor providing control of the fluorescence lifetime. We demonstrate how SMILES NPs with a few percent rhodamine and diazaoxatriangulenium FRET acceptors imbedded with a cyanine donor dye give identical emission spectra and high quantum yields but very different fluorescence lifetimes of 3 ns and 26 ns, respectively. The two spectrally identical NPs are easily distinguished at the single particle level in fluorescence lifetime imaging. The doping approach for dye based NPs provides predictable fluorescence lifetimes and allows for these bright imaging reagents to be used in time-resolved imaging detection modalities.

Advancing Spinal Cord Injury Bioimaging and Repair with Multifunctional Gold Nanodots Tracking

High levels of reactive oxygen species (ROS) are known to play a critical role in the secondary cascade of spinal cord injury (SCI). The scavenging of ROS has emerged as a promising approach for alleviating acute SCI. Moreover, identifying the precise location of the SCI site remains challenging. Enhancing the visualization of the spinal cord and improving the ability to distinguish the lesion site are crucial for accurate and safe treatment. Therefore, there is an urgent clinical need to develop a biomaterial that integrates diagnosis and treatment for SCI. Herein, ultra-small-sized gold nanodots (AuNDs) were designed for dual-mode imaging-guided precision treatment of SCI. The designed AuNDs demonstrate two important functions. First, they effectively scavenge ROS, inhibit oxidative stress, reduce the infiltration of inflammatory cells, and prevent apoptosis. This leads to a significant improvement in SCI repair and promotes a functional recovery after injury. Second, leveraging their excellent dual-mode imaging capabilities, the AuNDs enable rapid and accurate identification of SCI sites. The high contrast observed between the injured and adjacent uninjured areas highlights the tremendous potential of AuNDs for SCI detection. Overall, by integrating ROS scavenging and dual-mode imaging in a single biomaterial, our work on functionalized AuNDs provides a promising strategy for the clinical diagnosis and treatment of SCI.

Exploring Simple Particle-Based Signal Amplification Strategies in a Heterogeneous Sandwich Immunoassay with Optical Detection

Heterogeneous sandwich immunoassays are widely used for biomarker detection in bioanalysis and medical diagnostics. The high analyte sensitivity of the current "gold standard" enzyme-linked immunosorbent assay (ELISA) originates from the signal-generating enzymatic amplification step, yielding a high number of optically detectable reporter molecules. For future point-of-care testing (POCT) and point-of-need applications, there is an increasing interest in more simple detection strategies that circumvent time-consuming and temperature-dependent enzymatic reactions. A common concept to aim for detection limits comparable to those of enzymatic amplification reactions is the usage of polymer nanoparticles (NP) stained with a large number of chromophores. We explored different simple NP-based signal amplification strategies for heterogeneous sandwich immunoassays that rely on an extraction-triggered release step of different types of optically detectable reporters. Therefore, streptavidin-functionalized polystyrene particles (PSP) are utilized as carriers for (i) the fluorescent dye coumarin 153 (C153) and (ii) hemin (hem) molecules catalyzing the luminol reaction enabling chemiluminescence (CL) detection. Additionally, (iii) NP labeling with hemin-based microperoxidase MP11 was assessed. For each amplification approach, the PSP was first systematically optimized regarding size, loading concentration, and surface chemistry. Then, for an immunoassay for the inflammation marker C-reactive protein (CRP), the analyte sensitivity achievable with optimized PSP systems was compared with the established ELISA concept for photometric and CL detection. Careful optimization led to a limit of detection (LOD) of 0.1 ng/mL for MP11-labeled PSP and CL detection, performing similarly well to a photometric ELISA (0.13 ng/mL), which demonstrates the huge potential of our novel assay concept.

Magnesium-Catalyzed Dye-Embedded Polylactide Nanoparticles for the Effective Killing of Highly Metastatic B16F10 Melanoma Cells

In the current research, dye-embedded polylactic acid (PLA) conjugate materials were synthesized using one-pot ring-opening polymerization (ROP), i.e., (dtHPLA) (2-[(2,4,6-trimethylphenyl) imino]-1(2H)-acenaphthylenone-reduced-PLA) and (dmHPLA) (monoiminoacenaphtheneone-reduced-PLA), and then, nanoparticles (NPs) were engineered in the size range of 150 ± 30 nm. P(dtHPLA) NPs were employed in the treatment of melanoma, an aggressive type of skin cancer, which mandates the development of novel techniques to enhance healing outcomes and eliminate adverse effects related to existing treatments. In addition to exhibiting strong intracellular absorption in the spheroid model, the P(dtHPLA) NPs exhibited a strong cytotoxic effect on B16F10 cells, which resulted in oxidative stress from the generation of reactive oxygen species (ROS) and cell death. Additionally, a live/dead experiment using P(dtHPLA) NPs revealed a notable reduction in cell viability.

Dansylated Nitrile N-Oxide as the Fluorescent Dye Clickable to Unsaturated Bonds without Catalyst

Fluorescent polymeric materials have been exploited in the fields of aesthetical purposes, biomedical engineering, and three-dimensional printing applications. While the fluorescent materials are prepared by the polymerization of fluorescent monomer or the blending a fluorescent dye with common polymer, the covalent immobilization of fluorescent dye onto common polymers is not the practical technique. In this paper, dansylated nitrile N-oxide (Dansyl-NO) has been designed and synthesized to be a stable nitrile N-oxide as the derivative of 2-hydroxy-1-naphthaldehyde. While Dansyl-NO shows good reactivity to an alkene and an alkyne to give fluorescent Dansyl-Ene and Dansyl-Yne, respectively, it hardly reacts to a nitrile. The results indicate that Dansyl-NO serves as a fluorescent dye clickable to alkenes and alkynes. To know the effects of solvent on the fluorescent properties, the UV-vis and fluorescence spectra of Dansyl-Ene are measured in three solvents. Dansyl-Ene shows fluorescent solvatochromism, which appears to be red-shifted along with the increase in solvent polarity. Poly(styrene-co-butadiene) directly reacts with Dansyl-NO to give fluorescent modified SB. The emission spectrum of modified SB is blue-shifted compared with that of Dansyl-Ene. The blue-shift could be possibly attributed to the presence of less polar polymer skeleton around the dansyl moieties of modified SB.

FRET-Sensing of Multivalent Protein Binding at the Interface of Biomimetic Microparticles Functionalized with Fluorescent Glycolipids

Cell adhesion is a central process in cellular communication and regulation. Adhesion sites are triggered by specific ligand-receptor interactions inducing the clustering of both partners at the contact point. Investigating cell adhesion using microscopy techniques requires targeted fluorescent particles with a signal sensitive to the clustering of receptors and ligands at the interface. Herein, we report on simple cell or bacterial mimics, based on liquid microparticles made of lipiodol functionalized with custom-designed fluorescent lipids. These lipids are targeted toward lectins or biotin membrane receptors, and the resulting particles can be specifically identified and internalized by cells, as demonstrated by their phagocytosis in primary murine bone marrow-derived macrophages. We also evidence the possibility to sense the binding of a multivalent lectin, concanavalin A, in solution by monitoring the energy transfer between two matching fluorescent lipids on the surface of the particles. We anticipate that these liquid particle-based sensors, which are able to report via Förster resonance energy transfer (FRET) on the movement of ligands on their interface upon protein binding, will provide a useful tool to study receptor binding and cooperation during adhesion processes such as phagocytosis.

Exfoliation of a Coordination Polymer Based on a Linear π-Conjugated Ligand into an Ultrathin Nanosheet for Glyphosate Sensing

Owing to the large-scale consumption of pesticides and their potential threats to the environment and human health, the development of sensing materials for pesticides has attracted considerable attention in recent years. In this work, a novel Cd(II)-based coordination polymer (CP) with the formula [Cd(H2O)2(L)]·DMF (Cd-1, DMF = N,N-dimethylformamide, H2L = 4,4'-[(2,5-dimethoxy-1,4-phenylene)di-2,1-ethenediyl]bis-benzoic acid) was synthesized under solvothermal conditions. Structural analysis revealed that coordination between central Cd2+ cations and the ligand L2- formed two-dimensional (2D) networks, which were further assembled by noncovalent hydrogen bonds into a three-dimensional (3D) supramolecular framework. Through ultrasonic treatment in isopropyl alcohol, Cd-1 was exfoliated to afford an ultrathin CP-based 2D nanosheet (Cd-1-NS) with a thickness of less than 1.8 nm. Compared to the bulk materials, the prepared Cd-1-NS exhibited enhanced fluorescence emission properties and superior sensing performance toward glyphosate (Glyph) in water with high selectivity, sensitivity, anti-interference, fast response, and good recyclability via the turn-off effect. The limit of detection (LOD) of Cd-1-NS for Glyph was as low as 41 nM (7 ppb) in the low-concentration range of 0-2.4 μM. In addition, the Cd-1-NS also showed excellent practicability and reliability for the detection of Glyph in real samples, including lake water, tap water, cabbage, and watermelon skin, and could realize the rapid visualized sensing of Glyph residues on the surfaces of vegetables and fruits.

Focused ion beam-scanning electron microscopy provides novel insights of drug delivery phenomena

Scanning electron microscopy (SEM) has long been a standard tool for morphological analyses, providing sub micrometer resolution of pharmaceutical formulations. However, analysis of internal morphologies of such formulations can often be biased due to the introduction of artifacts that originate from sample preparation. A recent advancement in SEM, is the focused ion beam scanning electron microscopy (FIB-SEM). This technique uses a focused ion beam (FIB) to remove material with nanometer precision, to provide virtually sample-independent access to sub-surface structures. The FIB can be combined with SEM imaging capabilities within the same instrumentation. As a powerful analytical tool, electron microscopy and FIB-milling are performed sequentially to produce high-resolution 3D models of structural peculiarities of diverse drug delivery systems or their behavior in a biological environment, i.e. intracellular or -tissue distribution. This review paper briefly describes the technical background of the method, outlines a wide array of potential uses within the drug delivery field, and focuses on intracellular transport where high-resolution images are an essential tool for mechanistical insights.

Malachite green: a long-buried water-soluble AIEgen with near-infrared fluorescence for living cell nucleus staining

Fluorescent imaging probes are crucial for exploring nucleus-related cellular events in live cells. Ideal probes should be photostable, small-sized, highly contrasted, and low in background. Here, we discovered that malachite green is a water-soluble near-infrared luminogen with aggregation-induced emission properties. Importantly, it can be used for living cell nucleus staining in a wash-free manner.

Fluorescent polymer as a biosensing tool for the diagnosis of microbial pathogens

Diseases and diagnoses are predominant in the human population. Early diagnosis of etiological agents plays a vital role in the treatment of bacterial infections. Existing standard diagnostic platforms are laborious, time-consuming, and require trained personnel and cost-effective procedure, though they are producing promising results. These shortcomings have led to a thirst for rapid diagnostic procedures. Fluorescence-based diagnosis is one of the efficient rapid diagnostic methods that rely on specific and sensitive bacterial detection. Emerging bio-sensing studies on conducting polymers (CPs) are gaining popularity in medical diagnostics due to their promising properties of high fluorescence efficiency, good light stability, and low cytotoxicity. Poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), is the first identified soluble polymer and model material for understanding the fundamental photophysics of conventional CPs. In this present study, MEH-PPV is used as a fluorescent dye for direct pathogen detection applications by interacting with the microbial cell surface. An optimized concentration of MEH-PPV solution used to confirm the presence of selective bacterial structures. The present study endeavours towards bacterial detection based on the emission from bacteria due to interfacial interaction between polymer and bacterial surface.

Liquid core fluorescent organic nanoprobes: Long-term stability and highly selective lipid droplets bio-imaging

Lipid droplets (LDs) are important subcellular organelles that play a huge role in cell metabolism and growth. In this study, we synthesized two LDs fluorescent probes with benzothiadiazole (BTH) as electron acceptor and triphenylamine (TPA) as electron donor, which named as TPA-BTH1 and TPA-BTH2, respectively. Meanwhile, we introduced long alkyl chain to the probe as a shielding group and LDs targeting enhancement group. The results showed that the two probes were too sensitive to solvents' polarity because of the D-A structures possessed twisted intramolecular charge-transfer (TICT) effect. Furthermore, we prepared the two probes into nanoprobes by nanoprecipitation, which named as TPA-BTH1-20 and TPA-BTH2-20, respectively. The nanoprobes also had excellent fluorescence emission abilities and biocompatibility, as well as high photostability and accurately target LDs ability, which could be successfully applied in cell fluorescence imaging experiments.

Fluorogen-Functionalized Mesoporous Silica Hybrid Sensing Materials: Applications in Cu2+ Detection

Since Cu2+ ions play a pivotal role in both ecosystems and human health, the development of a rapid and sensitive method for Cu2+ detection holds significant importance. Fluorescent mesoporous silica materials (FMSMs) have garnered considerable attention in the realm of chemical sensing, biosensing, and bioimaging due to their distinctive structure and easily functionalized surfaces. As a result, numerous Cu2+ sensors based on FMSMs have been devised and extensively applied in environmental and biological Cu2+ detection over the past few decades. This review centers on the recent advancements in the methodologies for preparing FMSMs, the mechanisms underlying sensing, and the applications of FMSMs-based sensors for Cu2+ detection. Lastly, we present and elucidate pertinent perspectives concerning FMSMs-based Cu2+ sensors.

Capturing Doublet Intermediate Emitters by Chemically Crosslinking Confinement towards Spatiotemporal Encryption

Photoluminescence is one of the most meticulous ways to manipulate light energy. Typical photoluminescent emitters are mostly stable substances with a pure photophysical process of spontaneous photon-emission from their excited states. Intermediate emitters are elusive attributing to their synchronous energy transfer process including photophysical and incomplete photochemical pathways. An intermediate emitter containing radicals is more difficult to be observed due to its inherent chemical reactivity. Here, these challenges are overcome by spontaneously formed space limitations in polymer crosslinking networks meanwhile chemically active intermediates are captured. These doublet intermediates exhibit unique long-wavelength emissions under chemically crosslinking confinement conditions, and their luminous mechanism provides a novel perspective for designing intermediate emitters with liquid-crystal character and photoresponsive features towards spatiotemporal encryption, promising for the detection of photochemical reactions and the development of fascinating luminescent systems.

Indocyanine green and iohexol loaded hydroxyapatite in poly(L-lactide-co-caprolactone)-based composite for bimodal near-infrared fluorescence- and X-ray-based imaging

This study aimed to develop material for multimodal imaging by means of X-ray and near-infrared containing FDA- and EMA-approved iohexol and indocyanine green (ICG). The mentioned contrast agents (CAs) are hydrophilic and amphiphilic, respectively, which creates difficulties in fabrication of functional polymeric composites for fiducial markers (FMs) with usage thereof. Therefore, this study exploited for the first time the possibility of enhancing the radiopacity and introduction of the NIR fluorescence of FMs by adsorption of the CAs on hydroxyapatite (HAp) nanoparticles. The particles were embedded in the poly(L-lactide-co-caprolactone) (P[LAcoCL]) matrix resulting in the composite material for bimodal near-infrared fluorescence- and X-ray-based imaging. The applied method of material preparation provided homogenous distribution of both CAs with high iohexol loading efficiency and improved fluorescence signal due to hindered ICG aggregation. The material possessed profound contrasting properties for both imaging modalities. Its stability was evaluated during in vitro experiments in phosphate-buffered saline (PBS) and foetal bovine serum (FBS) solutions. The addition of HAp nanoparticles had significant effect on the fluorescence signal. The X-ray radiopacity was stable within minimum 11 weeks, even though the addition of ICG contributed to a faster release of iohexol. The stiffness of the material was not affected by iohexol or ICG, but incorporation of HAp nanoparticles elevated the values of bending modulus by approximately 70%. Moreover, the performed cell study revealed that all tested materials were not cytotoxic. Thus, the developed material can be successfully used for fabrication of FMs.

Supra-Cyanines: Ultrabright Cyanine-Based Fluorescent Supramolecular Materials in Solution and in the Solid State

Fluorescent materials with high brightness play a crucial role in the advancement of various technologies such as bioimaging, photonics, and OLEDs. While significant efforts are dedicated to designing new organic dyes with improved performance, enhancing the brightness of existing dyes holds equal importance. In this study, we present a simple supramolecular strategy to develop ultrabright cyanine-based fluorescent materials by addressing long-standing challenges associated with cyanine dyes, including undesired cis-trans photoisomerization and aggregation-caused quenching. Supra-cyanines are obtained by incorporating cyanine moieties in a cyclic peptide-based supramolecular scaffold, and exhibit high fluorescence quantum yields (up to 50 %) in both solution and in the solid state. These findings offer a versatile approach for constructing highly emissive cyanine-based supramolecular materials.

Membrane-Active Thermoresponsive Block Copolymers Containing a Diacylglycerol-Based Segment: RAFT Synthesis, Doxorubicin Encapsulation, and Evaluation of Cytotoxicity against Breast Cancer Cells

Herein, we report the formation of drug delivery systems from original thermoresponsive block copolymers containing lipid-based segments. Two acrylate monomers derived from palmitic- or oleic-acid-based diacylglycerols (DAGs) were synthesized and polymerized by the reversible addition-fragmentation chain transfer (RAFT) method. Well-defined DAG-based polymers with targeted molar masses and narrow molar mass distributions were next used as macro-chain transfer agents (macro-CTAs) for the polymerization of N-isopropylacrylamide (NIPAAm) or N-vinylcaprolactam (NVCL). The obtained amphiphilic block copolymers were formed into polymeric nanoparticles (PNPs) with and without encapsulated doxorubicin and characterized. Their biological assessment indicated appropriate cytocompatibility with the representatives of normal cells. Furthermore, compared to the free drug, increased cytotoxicity and apoptosis or necrosis induction in breast cancer cells was documented, including a highly aggressive and invasive triple-negative MDA-MB-231 cell line.

Self-assembled nano-particles of chitosan amphiphilic derivative for formaldehyde fluorescent detection and its application in test strips

Excessive levels of formaldehyde (FA) represent serious health risks. Aiming at the detection of formaldehyde content, this paper proposes a self-assembly method of proportional nanoprobes. Spherical nanoparticles (NPs) were prepared by one-step condensation reaction between rhodamine B (RhB) and chitosan (CS). After CS was modified by RhB, the linear structure changed and self-assembled under the action of "hydrophilic/hydrophobic" to form a core-shell structure with a cavity structure. The hydrophobic small molecule probe N-Butyl-4-Hydrazo-1,8-Naphacticimide (NBHN) spontaneously entered into the hydrophobic cavity to form spherical particles Chitosan-Rhodamine B@N-Butyl-4-Hydrazo-1,8-Naphacticimide (CS-RhB@NBHN) with a size of about 60 nm. The hydroxyl groups on CS enrich formaldehyde through charge interaction, and promote the reaction of formaldehyde with NBHN, so that the probe can detect formaldehyde at a lower concentration (detection limit 87 nmol·L-1). The self-assembled CS-RhB@NBHN nanoparticles significantly increased the response speed of NBHN (from 30 min to 10 min). After the reaction of NBHN with formaldehyde, the PET effect is released, the fluorescence transition from red to yellow of CS-RhB@NBHN, and the visual fluorescence response effect to formaldehyde is significantly improved. With the help of smartphone color recognition software, we converted the color of the probe solution into RGB values to realize the quantitative and visual detection of formaldehyde. In addition, CS-RhB@NBHN was used for the detection of FA in leather and air.

VEGFR-2 adhesive nanoprobes reveal early diabetic retinopathy in vivo

Diabetic retinopathy (DR) is a debilitating organ manifestation of diabetes. Absent of early diagnosis and intervention, vision tends to drastically and irreversibly decline. Previously, we showed higher vascular endothelial growth factor receptor 2 (VEGFR-2) expression in diabetic microvessels, and the suitability of this molecule as a biomarker for early DR diagnosis. However, a hurdle to translation remained generation of biodegradable nanoprobes that are sufficiently bright for in vivo detection. Here, an adhesive fluorescent nanoprobe with high brightness was developed using biodegradable materials. To achieve that, a fluorophore with bulky hydrophobic groups was encapsulated in the nanoparticles to minimize fluorophore π-π stacking, which diminishes brightness at higher loading contents. The nanoprobe selectively targeted the VEGFR-2 under dynamic flow conditions. Upon systemic injection, the nanoprobes adhered in the retinal microvessels of diabetic mice and were visualized as bright spots in live retinal microscopy. Histology validated the in vivo results and showed binding of the nanoprobes to the microvascular endothelium and firmly adhering leukocytes. Leukocytes were found laden with nanoprobes, indicating the potential for payload transport across the blood-retinal barrier. Our results establish the translational potential of these newly generated nanoprobes in early diagnosis of DR.

Bright and Stable Nanomaterials for Imaging and Sensing

This review covers strategies to prepare high-performance emissive polymer nanomaterials, combining very high brightness and photostability, to respond to the drive for better imaging quality and lower detection limits in fluorescence imaging and sensing applications. The more common approaches to obtaining high-brightness nanomaterials consist of designing polymer nanomaterials carrying a large number of fluorescent dyes, either by attaching the dyes to individual polymer chains or by encapsulating the dyes in nanoparticles. In both cases, the dyes can be covalently linked to the polymer during polymerization (by using monomers functionalized with fluorescent groups), or they can be incorporated post-synthesis, using polymers with reactive groups, or encapsulating the unmodified dyes. Silica nanoparticles in particular, obtained by the condensation polymerization of silicon alcoxides, provide highly crosslinked environments that protect the dyes from photodegradation and offer excellent chemical modification flexibility. An alternative and less explored strategy is to increase the brightness of each individual dye. This can be achieved by using nanostructures that couple dyes to plasmonic nanoparticles so that the plasmon resonance can act as an electromagnetic field concentrator to increase the dye excitation efficiency and/or interact with the dye to increase its emission quantum yield.

Micro- and nanosystems for the detection of hemorrhagic fever viruses

Hemorrhagic fever viruses (HFVs) are virulent pathogens that can cause severe and often fatal illnesses in humans. Timely and accurate detection of HFVs is critical for effective disease management and prevention. In recent years, micro- and nano-technologies have emerged as promising approaches for the detection of HFVs. This paper provides an overview of the current state-of-the-art systems for micro- and nano-scale approaches to detect HFVs. It covers various aspects of these technologies, including the principles behind their sensing assays, as well as the different types of diagnostic strategies that have been developed. This paper also explores future possibilities of employing micro- and nano-systems for the development of HFV diagnostic tools that meet the practical demands of clinical settings.

Aggregation-Induced Emission (AIE), Life and Health

Light has profoundly impacted modern medicine and healthcare, with numerous luminescent agents and imaging techniques currently being used to assess health and treat diseases. As an emerging concept in luminescence, aggregation-induced emission (AIE) has shown great potential in biological applications due to its advantages in terms of brightness, biocompatibility, photostability, and positive correlation with concentration. This review provides a comprehensive summary of AIE luminogens applied in imaging of biological structure and dynamic physiological processes, disease diagnosis and treatment, and detection and monitoring of specific analytes, followed by representative works. Discussions on critical issues and perspectives on future directions are also included. This review aims to stimulate the interest of researchers from different fields, including chemistry, biology, materials science, medicine, etc., thus promoting the development of AIE in the fields of life and health.

Polymer-based nanosystems and their applications in bone anticancer therapy

The mortality rate of bone cancer has witnessed a substantial reduction in recent years, all thanks to the advent of advanced cancer treatment modalities such as surgical intervention, radiation, and chemotherapy. Nevertheless, these popular modalities come with a set of clinical challenges, including non-specificity, side effects, and drug intolerance. In recent years, polymer-based nanosystems have emerged as a promising solution in bone anti-cancer therapy by virtue of their unique physical and chemical properties. These nanosystems can be tailored for use in different drug release mechanisms for therapeutic implementations. This review delves into the efficacy of these therapy applications in bone cancer (with a focus on one of the most common types of cancers, Osteosarcoma) treatment and their correlation with the properties of polymer-based nanosystems, in addition to their interaction with the tumor microenvironment and the biological milieu.

Highly Sensitive Detection of Bacteria by Binder-Coupled Multifunctional Polymeric Dyes

Infectious diseases caused by pathogens are a health burden, but traditional pathogen identification methods are complex and time-consuming. In this work, we have developed well-defined, multifunctional copolymers with rhodamine B dye synthesized by atom transfer radical polymerization (ATRP) using fully oxygen-tolerant photoredox/copper dual catalysis. ATRP enabled the efficient synthesis of copolymers with multiple fluorescent dyes from a biotin-functionalized initiator. Biotinylated dye copolymers were conjugated to antibody (Ab) or cell-wall binding domain (CBD), resulting in a highly fluorescent polymeric dye-binder complex. We showed that the unique combination of multifunctional polymeric dyes and strain-specific Ab or CBD exhibited both enhanced fluorescence and target selectivity for bioimaging of Staphylococcus aureus by flow cytometry and confocal microscopy. The ATRP-derived polymeric dyes have the potential as biosensors for the detection of target DNA, protein, or bacteria, as well as bioimaging.

Controlling Molecular Dye Encapsulation in the Hydrophobic Core of Core-Shell Nanoparticles for In Vivo Imaging

Polymeric nanoparticles with a hydrophobic core are valuable biomedical materials with potential applications in in vivo imaging and drug delivery. These materials are effective at protecting vulnerable molecules, enabling them to serve their functions in hydrophilic physiological environments; however, strategies that allow the chemical composition and molecular weight of polymers to be tuned, forming nanoparticles to control the functional molecules, are lacking. In this article, we review strategies for designing core-shell nanoparticles that enable the effective and stable encapsulation of functional molecules for biomedical applications. IR-1061, which changes its optical properties in response to the microenvironment are useful for in vitro screening of the in vivo stability of polymeric nanoparticles. An in vitro screening test can be performed by dispersing IR-1061-encapsulated polymer nanoparticles in water, saline, buffer solution, aqueous protein solution, etc., and measuring the absorption spectral changes. Through the screening, the effects of the polarity, molecular weight, and the chiral structure of polymers consisting of polymer nanoparticles on their stability have been revealed. Based on the findings presented here, more methodologies for the effective application of various biomolecules and macromolecules with complex high-dimensional structures are expected to be developed.

Designing Strong, Tough, Fluorescent, and UV-Shielding PLA Materials by Incorporating a Phenolic Compound-Based Multifunctional Modifier

The realization of high stiffness, high extensibility, and multi-functions for polylactic acid (PLA) is a vital issue for its practical applications. Herein, hydroxyalkylated tannin acid (mTA), a phenolic compound-based modifier with plentiful flat aromatic structures and flexible isopropanol oligomers, is designed and fabricated to act as the multifunctional modifier for PLA. The mTA exhibits the capability of emitting fluorescence and blocking UV light due to the combination of flat aromatic structures and plentiful flexible chains. Besides, mTA with high grafting degree (h-mTA) shows an excellent compatibility to PLA due to the hydrogen bonding interface and the high affinity of grafted isopropanol oligomers to PLA. As a result, the as-prepared PLA/h-mTA20 composite exhibits a strikingly improved extensibility by 61.2 times while maintaining the high yield strength of PLA. Moreover, PLA/h-mTA can serve as a fluorescent material with multi-mode responsiveness as well as a UV-shielding material with high transparency. We envision that this work opens a novel yet facile way to prepare a strong, tough, and multifunctional PLA material with expanded application scopes and will promote the practical applications of phenolic compounds in polymers.

Biotinylated Fluorescent Polymeric Nanoparticles for Enhanced Immunostaining

The performance of fluorescence immunostaining is physically limited by the brightness of organic dyes, whereas fluorescence labeling with multiple dyes per antibody can lead to dye self-quenching. The present work reports a methodology of antibody labeling by biotinylated zwitterionic dye-loaded polymeric nanoparticles (NPs). A rationally designed hydrophobic polymer, poly(ethyl methacrylate) bearing charged, zwitterionic and biotin groups (PEMA-ZI-biotin), enables preparation of small (14 nm) and bright fluorescent biotinylated NPs loaded with large quantities of cationic rhodamine dye with bulky hydrophobic counterion (fluorinated tetraphenylborate). The biotin exposure at the particle surface is confirmed by Förster resonance energy transfer with dye-streptavidin conjugate. Single-particle microscopy validates specific binding to biotinylated surfaces, with particle brightness 21-fold higher than quantum dot-585 (QD-585) at 550 nm excitation. The nanoimmunostaining method, which couples biotinylated antibody (cetuximab) with bright biotinylated zwitterionic NPs through streptavidin, significantly improves fluorescence imaging of target epidermal growth factor receptors (EGFR) on the cell surface compared to a dye-based labeling. Importantly, cetuximab labeled with PEMA-ZI-biotin NPs can differentiate cells with distinct expression levels of EGFR cancer marker. The developed nanoprobes can greatly amplify the signal from labeled antibodies, and thus become a useful tool in the high-sensitivity detection of disease biomarkers.

Quantitative Evaluation of a Multimodal Aptamer-Targeted Long-Circulating Polymer for Tumor Targeting

Aptamers are promising targeting agents for imaging and therapy of numerous diseases, including cancer. However, a significant shortcoming of aptamers is their poor stability and fast excretion, limiting their application in vivo. Common strategies to overcome these challenges is to chemically modify aptamers in order to increase their stability and/or to apply formulation technologies such as conjugating them to polymers or nanocarriers in order to increase their circulation half-life. This is expected to result in improved cellular uptake or retention to passively targeted nanomedicines. Herein, we report a modular conjugation strategy based on click chemistry between functionalized tetrazines and trans-cyclooctene (TCO), for the modification of high molecular weight hyperbranched polyglycerol (HPG) with sgc8 aptamer, fluorescent dyes, and ¹¹¹In. Our data indicate strong affinity of sgc8 against a range of solid tumor-derived cell lines that have previously not been tested with this aptamer. Nevertheless, nonspecific uptake of scrambled ssDNA-functionalized HPG in cells highlights inherent challenges of aptamer-targeted probes that remain to be solved for clinical translation. We validate HPG-sgc8 as a nontoxic nanoprobe with high affinity against MDA-MB-468 breast and A431 lung cancer cells and show significantly increased plasma stability compared to free sgc8. In vivo quantitative SPECT/CT imaging indicates EPR-mediated tumor uptake of HPG-sgc8 and nontargeted or scrambled ssDNA-conjugated HPG but no statistically significant difference between these formulations in terms of total tumor uptake or retention. Our study emphasizes the need for stringent controls and quantification in the evaluation of aptamer-targeted probes. For this purpose, our versatile synthesis strategy provides a simple approach for the design and evaluation of long-circulating aptamer-conjugated nanoformulations.

Synthesis and Application of Fluorescent Polymer Micro- and Nanoparticles

Fluorescent polymer particles have witnessed an increasing interest in recent years, owing to their fascinating physicochemical properties as well as wide-ranging applications. In this review, the state-of-the-art research progress of fluorescent polymer particles in the past five years is summarized. First, the synthesis protocols for fluorescent polymer particles, including emulsion polymerization, precipitation polymerization, dispersion polymerization, suspension polymerization, nanoprecipitation, self-assembly, and post-polymerization modification, are presented in detail. Then, the applications of the resulting beguiling particles in anticounterfeiting, chemical sensing, and biomedicine, are illustrated. Finally, the challenges and opportunities that exist in the field are pointed out. This review aims to offer important guidance and stimulate more research attention to this rapidly developing field.

Fluorescence Quantum Yield Standards for the UV/Visible/NIR: Development, Traceable Characterization, and Certification

The rational design of next generation molecular and nanoscale reporters and the comparison of different emitter classes require the determination of the fluorometric key performance parameter fluorescence quantum yield (Φ_f), i.e., the number of emitted photons per number of absorbed photons. Main prerequisites for reliable Φ_f measurements, which are for transparent luminophore solutions commonly done relative to a reference, i.e., a fluorescence quantum yield standard of known Φ_f, are reliable and validated instrument calibration procedures to consider wavelength-, polarization-, and time-dependent instrument specific signal contributions, and sufficiently well characterized fluorescence quantum yield standards. As the standard's Φ_f value directly contributes to the calculation of the sample's Φ_f, its accuracy presents one of the main sources of uncertainty of relative Φ_f measurements. To close this gap, we developed a first set of 12 fluorescence quantum yield standards, which absorb and emit in the wavelength region of 330-1000 nm and absolutely determined their Φ_f values with two independently calibrated integrating sphere setups. Criteria for standard selection and the configuration of these novel fluorescence reference materials are given, and the certification procedure is presented including homogeneity and stability studies and the calculation of complete uncertainty budgets for the certified Φ_f values. The ultimate goal is to provide the community of fluorescence users with available reference materials as a basis for an improved comparability and reliability of quantum yield data since the measurement of this spectroscopic key property is an essential part of the characterization of any new emitter.

Highly Sensitive Immunochromatographic Detection of Zearalenone Based on Ultrabright Red-Emitted Aggregation-Induced Luminescence Nanoprobes

Highly luminescent nanospheres have been demonstrated in enhancing the sensitivity of lateral flow immunoassay (LFIA) due to their loading numerous luminescent dyes. However, the photoluminescence intensities of existing luminescent nanospheres are limited due to the aggregation-caused quenching effect. Herein, highly luminescent aggregation-induced emission luminogens embedded nanospheres (AIENPs) with red emission were introduced as signal amplification probes of LFIA for quantitative detection of zearalenone (ZEN). Optical properties of red-emitted AIENPs were compared with time-resolved dye-embedded nanoparticles (TRNPs). Results showed that red-emitted AIENPs have stronger photoluminescence intensity on the nitrocellulose membrane and superior environmental tolerance. Additionally, we benchmarked the performance of AIENP-LFIA against TRNP-LFIA using the same set of antibodies, materials, and strip readers. Results showed that AIENP-LFIA exhibits good dynamic linearity with the ZEN concentration from 0.195 to 6.25 ng/mL, with half competitive inhibitory concentration (IC₅₀) and detection of limit (LOD) at 0.78 and 0.11 ng/mL, respectively. The IC₅₀ and LOD are 2.07- and 2.36-fold lower than those of TRNP-LFIA. Encouragingly, the precision, accuracy, specificity, practicality, and reliability of this AIENP-LFIA for ZEN quantitation were further characterized. The results verified that the AIENP-LFIA has good practicability for the rapid, sensitive, specific, and accurate quantitative detection of ZEN in corn samples.

Quatsomes Loaded with Squaraine Dye as an Effective Photosensitizer for Photodynamic Therapy

Photodynamic therapy is a non-invasive therapeutic strategy that combines external light with a photosensitizer (PS) to destroy abnormal cells. Despite the great progress in the development of new photosensitizers with improved efficacy, the PS’s photosensitivity, high hydrophobicity, and tumor target avidity still represent the main challenges. Herein, newly synthesized brominated squaraine, exhibiting intense absorption in the red/near-infrared region, has been successfully incorporated into Quatsome (QS) nanovesicles at different loadings. The formulations under study have been characterized and interrogated in vitro for cytotoxicity, cellular uptake, and PDT efficiency in a breast cancer cell line. The nanoencapsulation of brominated squaraine into QS overcomes the non-water solubility limitation of the brominated squaraine without compromising its ability to generate ROS rapidly. In addition, PDT effectiveness is maximized due to the highly localized PS loadings in the QS. This strategy allows using a therapeutic squaraine concentration that is 100 times lower than the concentration of free squaraine usually employed in PDT. Taken together, our results reveal the benefits of the incorporation of brominated squaraine into QS to optimize their photoactive properties and support their applicability as photosensitizer agents for PDT.

Bioimaging Probes Based on Magneto-Fluorescent Nanoparticles

Novel nanomaterials are of interest in biology, medicine, and imaging applications. Multimodal fluorescent-magnetic nanoparticles demand special attention because they have the potential to be employed as diagnostic and medication-delivery tools, which, in turn, might make it easier to diagnose and treat cancer, as well as a wide variety of other disorders. The most recent advancements in the development of magneto-fluorescent nanocomposites and their applications in the biomedical field are the primary focus of this review. We describe the most current developments in synthetic methodologies and methods for the fabrication of magneto-fluorescent nanocomposites. The primary applications of multimodal magneto-fluorescent nanoparticles in biomedicine, including biological imaging, cancer treatment, and drug administration, are covered in this article, and an overview of the future possibilities for these technologies is provided.

Highly water-stable, luminescent, and monodisperse polymer-coated CsPbBr3 nanocrystals for imaging in living cells with better sensitivity

Recently, CsPbX₃ (X= Cl, Br, I) nanocrystals (NCs) have evolved as a potential contender for various optoelectronic applications due to some of their excellent photophysical properties. Their superior non-linear optical properties enable them to take part in bioimaging applications due to their longer penetration depth and less scattering effect in living cells. However, the poor stability of perovskite NCs in aqueous media still remains a great challenge for practical usage. Comparatively stable silica-coated NCs have a tendency to agglomerate among other NCs and transform into bigger particles. Such big particles clog the inside of narrow channels during the uptake and can't effectively reach the targeted cells. To tackle such issues, we introduce a fast and reproducible synthesis process of CsPbBr₃ NCs that are coated with different long-chained organic ligands/polymers and compared their photophysical properties. Among them, polyvinylpyrrolidone (PVP) encapsulated NCs are highly luminescent in the green spectral region and showed a maximum photoluminescence quantum yield (PLQY) of up to 84%. The incorporation of n-isopropyl acrylamide (NIPAM) along with PVP further improves the stability of the PVP-coated NCs against heat and moisture. These NCs exhibit higher water stability compared to silica-coated NCs and maintained their emission properties for about one week in DI water. The smaller particle size, uniform size distribution, higher structural stability, and better dispersivity of polymer-coated NCs in the aqueous media enable them to perform as fluorescent probes for live cell imaging in mammalian Chinese Hamster Ovary (CHO-K1) cells. There is no adverse affect in the cells' viability and morphology even after long incubation periods (∼72 hours). The dosage of Pb-ions contained in the polymer-coated NCs is calculated as below 5 μg mL^-1, which is suitable for live cell imaging. This work provides insight for expanding the use of these NCs significantly into bioimaging applications with higher sensitivity.