Photostable Small-Molecule NIR-II Fluorescent Scaffolds that Cross the Blood-Brain Barrier for Noninvasive Brain Imaging

Real-time bioluminescence imaging of nitroreductase in breast cancer bone metastasis

Bone metastasis is a leading cause of mortality in breast cancer patients. Monitoring biomarkers for bone metastasis in breast cancer is crucial for the development of effective interventional treatments. Despite being a highly vascularized tissue, the bone presents a particularly hypoxic environment. Tumor hypoxia is closely linked to increased levels of various reductases, including nitroreductase (NTR). Currently, there are few probes available to detect NTR levels in breast cancer bone metastases. Although bioluminescent imaging is promising due to its specificity and high signal-to-noise ratio, many probes face challenges such as short emission wavelengths, reliance on complex conditions like external adenosine triphosphate, or lack of tissue specificity. In this study, through "caging" the luciferase substrate with an NTR-responsive aromatic nitro recognition group, we developed a highly sensitive and selective NTR-sensitive bioluminescent probe. The resulting probe effectively detects NTR in breast cancer cells and enables real-time monitoring of NTR in a mouse model of breast cancer bone metastasis. Additionally, it can differentiate between primary and bone tumors, and allow continuous monitoring of NTR levels, thus providing valuable insights into bone tumor progression. This work provides a powerful tool for further understanding the biological functions of NTR in breast cancer bone metastasis.

Rabies Virus Targeting NIR-II Phototheranostics

Rabies is a viral disease with an almost 100% fatality rate, primarily transmitted through bites from infected animals, with a long incubation period and no effective clinical treatments to date. Herein, we developed the first fluorescent nanotheranostic probe in the second near-infrared (NIR-II) window capable of efficiently crossing the blood-brain barrier (BBB), precisely targeting rabies virus (RABV), and enabling safe photodynamic therapy (PDT). This probe is based on a novel NIR-II organic polyacetylene fluorophore, DK, which self-assembles via a click reaction with a nanoparticle carrier, N3-PEG2000-R, that we synthesized with a high biocompatibility and BBB permeability. The probe surface is further modified with an aptamer that specifically binds to RABV glycoprotein (RVG), resulting in our final nanotheranostic probe, DK@RA-PEG. Upon intravenous injection into mice, it effectively crosses the BBB, localizes to the infection site, and binds to the RVG, allowing for real-time NIR-II fluorescence imaging. Additionally, it efficiently converts light energy into chemical energy without generating thermal effects, ensuring safe and effective PDT. This advanced nanotheranostic probe integrates precise targeting, deep-tissue imaging, and safe therapy, making it a promising candidate for future clinical applications in rabies treatment.

Understanding the Properties of Donor-Acceptor Substituted Boron Difluoride 3-Cyanoformazanate Dyes

π-Conjugated materials offer attractive traits including semiconductivity, low-energy light absorption/photoluminescence, and solution processability that render them ubiquitous within the organic electronics field. Among many strategies for property tuning, the creation of asymmetric electronic structures through the installation of donor and acceptor substituents commonly results in low-energy absorption/photoluminescence bands. Boron difluoride formazanate dyes are readily synthesized, can be asymmetrically substituted with donor and acceptor groups, and have unexpectedly low-energy absorption/photoluminescence bands that extend into the near-infrared. In this study, we prepared a series of donor-acceptor substituted boron difluoride 3-cyanoformazanate dyes and compared their properties to symmetric analogues. Our findings suggest that donor-acceptor derivatives are highly delocalized with properties intermediate of their symmetric counterparts. Furthermore, the data obtained suggest that the N-aryl substituents act as donors to the strongly accepting boron difluoride formazanate core, regardless of the functional groups appended to them. These properties were reproduced computationally, and while the frontier orbitals calculated for donor-acceptor dyes were modestly asymmetric, there was no evidence of charge-transfer character. This work provides significant insight into the unexpected properties of boron difluoride formazanates and reveals that their strongly accepting nature circumvents the predicted augmentation of electronic structure commonly observed for donor-accepter substituted dyes.

Morphology evolution and NIR-II luminescence enhancement in LaF3:Er3+ nanoparticles

Luminescence imaging in the second near-infrared (NIR-II) window (1000-1700 nm) has attracted extensive attention in recent years owing to its superior tissue penetration ability and weak spontaneous fluorescence effects in biological tissues. However, an important bottleneck restricting the development of NIR-II luminescence imaging technology is the lack of nanoprobes with suitable morphology, particle size and high luminescence intensity. In this work, NIR-II emitted LaF3:Er3+ nanoparticles (NPs) were synthesized by a simple chemical precipitation method, where the size and morphology of LaF3:Er3+ NPs were precisely controlled through the regulation of reaction conditions. The NIR-II luminescence of Er3+ was effectively enhanced for 8.4 times by Zr4+ doping. The results provides useful reference for the research of NIR-II luminescent imaging nanoprobes.

Monitoring Acidification Preceding Aβ Deposition in Alzheimer's Disease

Amyloid beta (Aβ) is the primary early biomarker of Alzheimer's disease (AD), and since an acidic environment promotes Aβ aggregation, acidification plays a crucial role in AD progression. In this study, a novel acid-responsive near-infrared (NIR) fluorescent probe alongside multiple molecular biology techniques to investigate the temporal relationship between acidification and Aβ deposition, as well as the underlying mechanisms of acidification is employed. By monitoring 2- to 11-month-old APP/PS1 mice and wild-type (WT) mice, it is detected significant fluorescence signal in APP/PS1 mice beginning at 3 months preceding Aβ deposition at 5 months, and peaking at 5 months, followed by cognitive deficits at 8 months. Additionally, elevated monocarboxylate transporter 4 (MCT4) protein expression in 3-month-old APP/PS1 mice indicated disruption of astrocyte-neuron lactate shuttle (ANLS) homeostasis. Overall, this findings first demonstrate that acidification precedes Aβ deposition, peaks at the onset of Aβ deposition, and diminishes thereafter, with early acidification likely driven by the disruption of ANLS.

Naphthalimide Nanoprobe with Enhanced Electron-Withdrawing Ability and Large Stokes Shift for NIR-II Fluorescence Imaging-Guided Phototheranostics

Nanoprobes with NIR-II fluorescence and a large Stokes shift are highly desirable for high-quality bioimaging applications. However, designing NIR-II fluorescent nanoprobes with the desired photophysical properties based on small organic molecules remains a significant challenge. Herein, we report a naphthalimide (NMI)-based NIR-II fluorescent molecule, NMI-BF2, by further enhancing the electron affinity of NMI through the incorporation of boron difluoride formazanate. NMI-BF2 exhibits a sufficient NIR-II quantum yield (QY) of 0.53%, a large Stokes shift of 263 nm, and excellent photostability. For biological applications, NMI-BF2 is coassembled with fetal bovine serum (FBS) to prepare a biocompatible nanoprobe, NMI-BF2/FBS, which maintains a good NIR-II QY of 0.21% and a photothermal conversion efficiency of 32.5%. In vitro and in vivo studies verified that the NMI-BF2/FBS nanoprobe shows an excellent photothermal antitumor therapeutic effect, guided by NIR-II fluorescence and photoacoustic imaging.

Site-Specific Molecular Engineering of Nanobody-Glucoside Conjugates for Enhanced Brain Tumor Targeting

Nanobodies play an increasingly prominent role in cancer imaging and therapy. However, their in vivo efficacy is often constrained by inadequate tumor penetration and rapid clearance from the bloodstream, particularly in brain tumors due to the intractable blood-brain barrier (BBB). Glycosylation is a favorable strategy for modulating the biological functions of nanobodies, including permeability and pharmacokinetics, but it also leads to heterogeneous glycan structures, which affect the targeting ability, stability, and quality of nanobodies. Here, we describe a post-translational modification strategy to produce precisely engineered and homogeneous nanobody-glucoside conjugates for effective BBB penetration and brain tumor targeting. Specifically, we employ an enzymatic method and click chemistry to functionalize nanobodies with glucoside and poly(ethylene glycol) (PEG), facilitating efficient transcytosis into the brain via glucose transporter-1 (GLUT1). Furthermore, we rationally select a near-infrared (NIR) fluorophore for labeling to maintain the metabolic pathway and biodistribution of nanobodies and assess their potency in two tumor models. The resulting nanobody-glucoside conjugates demonstrate a remarkable increase in BBB penetration and brain tumor accumulation, which are ∼2.9-fold higher in the transgenic mouse model and ∼5.7-fold higher in the orthotopic glioma model compared to unmodified nanobodies. This study provides a promising approach for the production of nanobody therapeutic agents for central nervous system (CNS) delivery.

Near-Infrared-II Fluorescent Probes for Analytical Applications: From In Vitro Detection to In Vivo Imaging Monitoring

Biomarkers play a vital role in the regulation of life processes, especially in predicting the occurrence and development of diseases. For the early diagnosis and precise treatment of diseases, it has become necessary and significant to detect biomarkers with sensitivity, accuracy, simplicity, convenience, and even visualization. Fluorescent-probe-based techniques have been recognized as one of the most powerful tools for the sensitive detection and real time imaging of biomarkers in biological samples. However, traditional optical probes, mainly including the visible probes (400-700 nm) and the near-infrared I (NIR-I, 700-900 nm) probes, suffer from low sensitivity, poor resolution, strong absorption and scattering, and high background fluorescence, which hinder effective monitoring of biomarkers. Fortunately, the past decade has witnessed a remarkable evolution in the application fields of near-infrared II (NIR-II, 900-1700 nm) fluorescence, driven by its exceptional optical characteristics and the advancement of imaging technologies. Leveraging the superior penetration capabilities, negligible autofluorescence, and extended fluorescence emission wavelengths, NIR-II fluorescent probes significantly enhance the signal-to-noise ratio (SNR) of in vitro detection (IVD) and the temporal resolution of in vivo imaging. Our team has been committed to the design strategy, controlled synthesis, luminous mechanisms, and biomedical applications of NIR-II fluorescent probes. In this Account, we present the representative works in recent years from our group in the field of NIR-II fluorescent probes for analytical applications, ranging from in vitro detection of biomarkers to in vivo imaging monitoring of different biomarkers and various diseases, which also will further provide a general overview of analytical applications of NIR-II fluorescence probes. First, the in vitro analytical applications of NIR-II fluorescent probes are fully summarized, including tumor marker detection, virus and bacteria analysis, cell testing, and small-molecule sensing. Second, the in vivo imaging monitoring applications of NIR-II fluorescent probes are adequately discussed, including ROS detection, gas monitoring, pH sensing, small-molecule testing, receptor analysis, and the imaging diagnosis of some serious diseases. Finally, we further outline the application advantages of NIR-II fluorescent probes in analytical fields and also discuss in detail some challenges as well as their future development. There is a reasonable prospect that the in vitro detection technology and the in vivo imaging monitoring technology based on NIR-II fluorescent probes will exhibit great development potential in biomedical research and clinical disease diagnosis. We hope that this Account can expand their reach into an even broader spectrum of fields, further enhancing their impact on scientific discovery and medical practice.

Side Chain Phenyl Isomerization-Induced Spatial Conjugation for Achieving Efficient Near-Infrared II Phototheranostic Agents

The contradiction of near-infrared II (NIR-II) emission and photothermal effects limits the development of phototheranostic agents (PTAs) in many emerging cutting-edge applications. Organic aggregates present a promising opportunity for the balance of competitive relaxation processes through the manipulation of molecular structure and packing. Herein, side chain phenyl isomerization-induced spatial conjugation was proposed for constructing A-D-A type NIR-II PTAs with simultaneous enhancement of fluorescence brightness and photothermal properties. Three pairs of mutually isomeric fluorophores, whose phenyls respectively located at the outside (o-series) and inside (i-series) of the side chain, were designed and synthesized. The positional isomerization of the phenyl endows the o-series crystals with strong spatial conjugation between the phenyl group on the side chain and the backbone, as well as interlocked planar network, which is different to that observed in the i-series. Thus, all o-series nanoparticles (NPs) exhibit red-shifted absorption, enhanced NIR-II emission, and superior photothermal properties than their i-series counterparts. A prominent member of the o-series, o-ITNP NPs, demonstrated efficacy in facilitating NIR-II angiography, tumor localization, and NIR-II imaging-guided tumor photothermal therapy. The success of this side chain phenyl isomerization strategy paves the way for precise control of the aggregation behavior and for further development of efficient NIR-II PTAs.

Activatable Molecular Probes With Clinical Promise for NIR-II Fluorescent Imaging

The second near-infrared window (NIR-II) fluorescence imaging has been widely adopted in basic scientific research and preclinical applications due to its exceptional spatiotemporal resolution and deep tissue penetration. Among the various fluorescent agents, organic small-molecule fluorophores are considered the most promising candidates for clinical translation, owing to their well-defined chemical structures, tunable optical properties, and excellent biocompatibility. However, many currently available NIR-II fluorophores exhibit an "always-on" fluorescence signal, which leads to background noise and compromises diagnostic accuracy during disease detection. Developing NIR-II activatable organic small-molecule fluorescent probes (AOSFPs) for accurately reporting pathological changes is key to advancing NIR-II fluorescence imaging toward clinical application. This review summarizes the rational design strategies for NIR-II AOSFPs based on four core structures (cyanine, hemicyanine, xanthene, and BODIPY). These NIR-II AOSFPs hold substantial potential for clinical translation. Furthermore, the recent advances in NIR-II AOSFPs for NIR-II bioimaging are comprehensively reviewed, offering clear guidance and direction for their further development. Finally, the prospective efforts to advance NIR-II AOSFPs for clinical applications are outlined.

IFN-γ reprograms cardiac microvascular endothelial cells to mediate doxorubicin transport and influences the sensitivity of mice to doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is a first-line chemotherapy agent known for its cardiac toxicity. DOX-induced cardiotoxicity (DIC) severely limits the use for treating malignant tumors and is associated with a poor prognosis. The sensitivity to DIC varies among patients, but the precise mechanisms remain elusive. Here we constructed a mouse model of DIC using DOX to investigate potential mechanisms contributing to the differential susceptibility to DIC. Through surface-enhanced Raman spectroscopy and single-cell RNA sequencing, we explored the mechanisms underlying DIC phenotypic variations. In vitro and in vivo studies with small-molecule drugs were conducted. DIC-insensitive mice displayed preserved ejection fractions, lower DOX levels in cardiac tissues and higher levels in the serum. Single-cell RNA sequencing revealed differences of gene expression in cardiac endothelial cells between DIC-insensitive and DIC-sensitive groups. The expression of IFN-γ pathway-related genes was high in DIC-insensitive mice. IFN-γ administration decreased the DOX distribution in cardiac tissues, whereas PPAR-γ activation increased DIC susceptibility. IFN-γ stimulation upregulated P-glycoprotein expression, leading to increased DOX efflux and DIC insensitivity. Our model provides insights into the mechanisms of DIC sensitivity and potential preventive strategies.

Glaser-Hay-Coupled Random Copolymers Containing Boron Difluoride Formazanate Dyes

𝜋-Conjugated polymers, including those based on acetylenic repeating units, are an exciting class of materials that offer narrow optical band gaps and tunable frontier orbital energies that lead to their use in organic electronics. This work expands the knowledge of structure-property relationships of acetylenic polymers through the synthesis and characterization of a series of Glaser-Hay-coupled model compounds and random copolymers comprised of BF2 formazanate, fluorene, and/or bis(alkoxy)benzene units. The model compounds and copolymers synthesized exhibit redox activity associated with the reversible reduction of the BF2 formazanate units and the irreversible reduction of the fluorene and bis(alkoxy)benzene units. The copolymers exhibit absorption profiles characteristic or intermediate of their respective models and homopolymers, leading to broad absorption of UV-vis light. The alkyne linkages of the model compounds and copolymers are reacted with [Co2(CO)8] to convert the alkyne functional groups into cobalt carbonyl clusters. This transformation leads to blue-shifted absorption profiles due to a decrease in π-conjugation, demonstrating the ability to tune the properties of these materials through post-polymerization functionalization. The redox activity and broad absorption bands of the polymers reported make them excellent candidates for use in photovoltaics and other light-harvesting applications.

Endogenous Fe2+-triggered self-targeting nanomicelles for self-amplifying intracellular oxidative stress

BACKGROUND

Artesunate (ASA) acts as an •O₂- source through the breakdown of endoperoxide bridges catalyzed by Fe2+, yet its efficacy in ASA-based nanodrugs is limited by poor intracellular delivery.

METHODS

ASA-hyaluronic acid (HA) conjugates were formed from hydrophobic ASA and hydrophilic HA by an esterification reaction first, and then self-targeting nanomicelles (NM) were developed using the fact that the amphiphilic conjugates of ASA and HA are capable of self-assembling in aqueous environments.

RESULTS

These ASA-HA NMs utilize CD44 receptor-mediated transcytosis to greatly enhance uptake by breast cancer cells. Subsequently, endogenous Fe2+ from the tumor catalyzes the released ASA to produce highly toxic •O₂- radicals to kill tumor cells, although sustained tumor growth inhibition can be achieved via in vivo experiments.

CONCLUSIONS

Self-targeting NMs represent a promising strategy for enhancing ASA-based treatments, leveraging clinically approved drugs to expedite drug development and clinical research in oncology.

Recent Advances in Tetra-Coordinate Boron-Based Photoactive Molecules for Luminescent Sensing, Imaging, and Anticounterfeiting

Tetra-coordinate boron-based fluorescent materials hold considerable promise across chemistry, biology and materials science due to their unique and precisely tunable optoelectronic properties. The incorporation of the heteroatom boron (B) enables these materials to exhibit high luminescence quantum yields, adjustable absorption and emission wavelengths, and exceptional photostability. This review examines the molecular design and applications of tetra-coordinate boron-based photoactive molecules, highlighting their roles in fluorescence sensing, anticounterfeiting, and imaging. We outline how structural features impact their properties and discuss strategies for enhancing their performance, including ligand modification and the extension of conjugation length, among others. Additionally, future research focus in this field is also addressed including strategies for diversifying molecular structures and enhancing molecular stability, which is believed to pave the way for innovative solutions to the challenges in areas such as sensing, imaging and information security.

Amphiphilic hemicyanine molecular probes crossing the blood-brain barrier for intracranial optical imaging of glioblastoma

Intracranial optical imaging of glioblastoma (GBM) is challenging due to the scarcity of effective probes with blood-brain barrier (BBB) permeability and sufficient imaging depth. Herein, we describe a rational strategy for designing optical probes crossing the BBB based on an electron donor-π-acceptor system to adjust the lipid/water partition coefficient and molecular weight of probes. The amphiphilic hemicyanine dye (namely, IVTPO), which exhibits remarkable optical properties and effective BBB permeability, is chosen as an efficient fluorescence/photoacoustic probe for in vivo real-time imaging of orthotopic GBM with high resolution through the intact skull. Abnormal leakage of IVTPO adjacent to the developing tumor is unambiguously observed at an early stage of tumor development prior to impairment of BBB integrity, as assessed by commercial Evans blue (EB). Compared with EB, IVTPO demonstrates enhanced optical imaging capability and improved tumor-targeting efficacy. These results offer encouraging insights into medical diagnosis of intracranial GBM.

Intramolecular Repulsive Interactions Enable High Efficiency of NIR-II Aggregation-Induced Emission Luminogens for High-Contrast Glioblastoma Imaging

Strategies to acquire high-efficiency luminogens that emit in the second near-infrared (NIR-II, 1000-1700 nm) range are still rare due to the impediment of the energy gap law. Herein, a feasible strategy is pioneered by installing large-volume encumbrances in a confined space to intensify the repulsive interactions arising from overlapping electron densities. The experimental results, including smaller coordinate displacement, reduced reorganization energy, and suppressed internal conversion, demonstrate that the repulsive interactions assist in the inhibition of radiationless deactivation. Meanwhile, the configuration and hybridization form of the donor units are transformed along with the repulsive interactions, bringing about improved oscillator strength. A 3.8-fold higher luminescence efficiency is realized via the synergistic effect. Furthermore, the repulsive interactions endow the NIR-II fluorophores with a highly twisted conformation, superior AIE activity, and cascaded improvement of fluorescence emission from isolated molecules to aggregates. By utilizing a brain-targeting peptide to functionalize the NIR-II nanoparticles, accurate detection and high-contrast imaging of orthotopic glioblastoma are realized. This work not only explores a fundamental principle to handle the intractable energy gap law but also provides potential applications of NIR-II luminogens in high-contrast bioimaging and glioblastoma detection.

Platinum-Centered Oligoynes Capped by Boron Difluoride Formazanate Dyes and Their Thin-Film Properties

Since the Nobel prize winning discovery that polyacetylene could act as a semiconductor, there has been tremendous efforts dedicated to understanding and harnessing the unusual properties of π-conjugated polymers. Much of this research has focused on the preparation of oligoynes and polyynes with well-defined numbers of repeating alkyne units as models for carbyne. These studies are usually hampered by a structure-property relationship where the stability of the resulting materials decrease with the incorporation of additional alkyne units. Here, we describe a series of oligoynes, with up to 12 alkyne units, where electron-rich [Pt(PBu3)2]2+ units are incorporated at the center of the oligoyne backbones which are capped by electron-poor BF2 formazanate dyes. These compounds exhibit excellent stability and solubility, panchromatic absorption, and redox activity characteristic of their structural components. These traits facilitated thin-film studies of extended oligoyne materials, where it is shown that incorporating [Pt(PBu3)2]2+ units leads to smoother films, decreased conductivity on the microscale, and increased conductivity on the nanoscale when compared to metal-free analogs. Remarkably, our oligoynes have superior conductivity compared to the ubiquitous poly(3-hexylthiophene) semiconductor.

Turn-On NIR-II Polymer Dots with Large Stokes Shift for In Vivo Visualizing Dynamical Brain Zinc in Alzheimer's Disease Mouse

It is a critical and broad prospect to evaluate ion levels and monitor their dynamic changes in the brain for early diagnosis, in-depth mechanism investigation, and accurate staging of neurodegenerative diseases including Alzheimer's disease (AD). It is still a great challenge to in vivo track Zn2+ levels in the brain by fluorescence imaging due to the drawbacks including short emission wavelength, poor selectivity and sensitivity, and unfavorable penetration across the blood-brain barrier (BBB) for currently developed fluorescent probes. We herein engineer a fluorescent probe with a large Stokes shift of 256 nm, NNDPTQ Pdots, which display substantial Zn2+-specific turn-on response in the NIR II region with the longest emission of 1064 nm up to now. The probe shows a fast response within seconds, high selectivity, low-nanomolar affinity of 6 nM, low detection limit of 3.4 nM, and efficient BBB-permeability efficacy of 37%. The results of brain imaging demonstrate that brain Zn2+ level in AD mice is substantially higher than normal mice and also is elevated with the prolonging of AD-bearing time. This study may provide a promising fluorescent indicator for in vivo tracing of brain Zn2+ levels to reveal AD pathogenesis.

A Small-Molecule NIR-II Probe for the Diagnosis of Hemorrhagic Diseases

Numerous hemorrhagic disorders, particularly those presenting deep hemorrhage, pose diagnostic challenges, often leading to delayed treatment and severe outcomes. Near-infrared (NIR)-II fluorescence imaging offers advantages such as deep tissue penetration, real-time visualization, and a high signal-to-background ratio, making it highly suitable for diagnosing hemorrhagic diseases. In this study, an NIR-II fluorescent probe LJ-2P carrying carboxylic and phosphoric acid groups is successfully applied for imaging hemorrhagic diseases. LJ-2P demonstrates a strong affinity for fibrinogen and fibrin clots both computationally and experimentally, thus exhibiting increased brightness upon coagulation. As compared to Indocyanine Green, LJ-2P provides a longer imaging window, higher imaging specificity, and signal-to-background ratio, as well as superior photobleaching resistance in three disease models: gastric, pulmonary, and cerebral hemorrhages. These results reveal that LJ-2P demonstrates enhanced imaging capabilities, enabling precise identification of hemorrhagic sites.

Dihydropyridopyrazine Functionalized Xanthene: Generating Stable NIR Dyes with Small-Molecular Weight by Enhanced Charge Separation

Near-infrared region (NIR; 650-1700 nm) dyes offer many advantages over traditional dyes with absorption and emission in the visible region. However, developing new NIR dyes, especially organic dyes with long wavelengths, small molecular weight, and excellent stability and biocompatibility, is still quite challenging. Herein, we present a general method to enhance the absorption and emission wavelengths of traditional fluorophores by simply appending a charge separation structure, dihydropyridopyrazine. These novel NIR dyes not only exhibited greatly redshifted wavelengths compared to their parent dyes, but also displayed a small molecular weight increase together with retained stability and biocompatibility. Specifically, dye NIR-OX, a dihydropyridopyra-zine derivative of oxazine with a molecular mass of 386.2 Da, exhibited an absorption at 822 nm and an emission extending to 1200 nm, making it one of the smallest molecular-weight NIR-II emitting dyes. Thanks to its rapid metabolism and long wave-length, NIR-OX enabled high-contrast bioimaging and assessment of cholestatic liver injury in vivo and also facilitated the evalua-tion of the efficacy of liver protection medicines against cholestatic liver injury.

Biomimetic Gold Nanorods-Manganese Porphyrins with Surface-Enhanced Raman Scattering Effect for Photoacoustic Imaging-Guided Photothermal/Photodynamic Therapy

Surface-enhanced Raman scattering (SERS) imaging integrating photothermal and photodynamic therapy (PTT/PDT) is a promising approach for achieving accurate diagnosis and effective treatment of cancers. However, most available Raman reporters show multiple signals in the fingerprint region, which overlap with background signals from cellular biomolecules. Herein, a 4T1 cell membrane-enveloped gold nanorods-manganese porphyrins system (GMCMs) is designed and successfully fabricated as a biomimetic theranostic nanoplatform. Manganese porphyrins are adsorbed on the surface of Au nanorods via the terminal alkynyl group. Cell membrane encapsulation protects the manganese porphyrins from falling off the gold nanorods. The biomimetic GMCMs confirm specific homologous targeting to 4T1 cells with good dispersibility, excellent photoacoustic (PA) imaging properties, and preferable photothermal and 1O2 generation performance. GMCMs exhibit distinct SERS signals in the silent region without endogenous biomolecule interference both in vitro and in vivo. Manganese ions could not only quench the fluorescence of porphyrins to enhance the SERS imaging effect but also deplete cellular GSH to increase 1O2 yield. Both in vitro and in vivo studies demonstrate that GMCMs effectively eradicate tumors through SERS/PA imaging-guided PTT/PDT. This study provides a feasible strategy for augmenting the Raman imaging effects of the alkynyl group and integrating GSH-depletion to enhance PTT/PDT efficacy.

Structure Tailoring of Hemicyanine Dyes for In Vivo Shortwave Infrared Imaging

In vivo bioimaging using shortwave infrared (SWIR) (1000-2000 nm) molecular dyes enables deeper penetration and higher contrast compared to visible and near-infrared-I (NIR-I, 700-900 nm) dyes. Developing new SWIR molecules is still quite challenging. This study developed SRHCYs, a panel of fluorescent dyes based on hemicyanine, with adjustable absorbance (830-1144 nm) and emission (886-1217 nm) wavelength. The photophysical attributes of these dyes are precisely tailored by strengthening the donor parts and extending polymethine chains. SRHCY-3, with its clickable azido group, was chosen for high-performance imaging of blood vessels in living mice, enabling the precise detection of brain and lung cancer. The combination of these probes achieved in vivo multicolor imaging with negligible optical crosstalk. This report presents a series of SWIR hemicyanine dyes with promising spectroscopic properties for high-contrast bioimaging and multiplexing detection.

Antibody-based near-infrared fluorogenic probes for wash-free imaging of cell-surface proteins

BACKGROUND

Cell-surface proteins, which are closely associated with various physiological and pathological processes, have drawn much attention in drug discovery and disease diagnosis. Thus, wash-free imaging of the target cell-surface protein under its native environment is critical and helpful for early detection and prognostic evaluation of diseases.

RESULTS

To minimize the interference from autofluorescence and fit the penetration depth towards tissue samples, we developed a fluorogenic antibody-based probe, Ab-Cy5.5, which will liberate > 5-fold turn-on near-infrared (NIR) emission in the presence of its target antigen within 10 min.

SIGNIFICANCE

By taking advantage of the fluorescence-quenched dimeric H-aggregation of Cy5.5, Ab-Cy5.5 with Cy5.5 attached at the N-terminus showed negligible background signal, allowing direct imaging of the target cell-surface protein in both living cells and tissue samples without washing.

Delivering DNA Aptamers Across the Blood-Brain Barrier Reveals Heterogeneous Decreased ATP in Different Brain Regions of Alzheimer's Disease Mouse Models

DNA aptamers have been developed as sensors to detect metabolites with high sensitivity, selectivity, and biocompatibility. While they are effective in sensing important targets in the brain, the lack of methods for their efficient delivery across the blood-brain barrier (BBB) has significantly hindered their applications in brain research. To address this issue, we herein report the development of brain cell-derived exosomes as endogenous BBB delivery vehicles to deliver an ATP-responsive aptamer across the BBB of live mice for noninvasive live brain imaging. We found that the system uses endosome recycling to transfer the sensors between the delivered exosomes and native recycling endosomes, resulting in high delivery efficiencies. Using this system, we observed unique signal distributions for ATP across different brain regions, with significant accumulation in the subiculum and cortex in healthy mice. In an Alzheimer's disease transgenic mouse model, ATP levels decreased in the subiculum and cortex, demonstrating this method's capability to determine metabolite location and relative abundance with high spatial resolution in vivo. Since DNA aptamers have been obtained for many other targets, the method developed in this work can be applied to deliver sensors across the BBB to image a wide range of other brain-related metabolites.

Construction of Boron Difluoride Complexes with Asymmetric N,N'-Bidentate Ligands

Boron difluoride (BF2) complexes with asymmetrical N,N'-bidentate ligands have received increasing attention due to their fascinating properties and broad applications. They are generally constructed in two steps: ligand formation, followed by boron complexation. This review focuses on categorizing these BF2 complexes based on the key synthetic strategies that have been applied in the ligand formation steps. The post-functionalization, properties and applications of different types of BF2 complexes are presented. Their challenges and opportunities are also discussed. This should help the future rational design and synthesis of BF2 complexes with intriguing properties and practical applications.

Near-infrared II theranostic agents for the diagnosis and treatment of Alzheimer's disease

BACKGROUND

Near-infrared II theranostic agents have gained great momentum in the research field of AD owing to the appealing advantages. Recently, an array of activatable NIR-II fluorescence probes has been developed to specifically monitor pathological targets of AD. Furthermore, various NIR-II-mediated nanomaterials with desirable photothermal and photodynamic properties have demonstrated favorable outcomes in the management of AD.

METHODS

We summerized amounts of references and focused on small-molecule probes, nanomaterials, photothermal therapy, and photodynamic therapy based on NIR-II fluorescent imaging for the diagnosis and treatment in AD. In addition, design strategies for NIR-II-triggered theranostics targeting AD are presented, and some prospects are also addressed.

RESULTS

NIR-II theranostic agents including small molecular probes and nanoparticles have received the increasing attention for biomedical applications. Meanwhile, most of the theranostic agents exhibited the promising results in animal studies. To our surprise, the multifunctional nanoplatforms also show a great potential in the diagnosis and treatment of AD.

CONCLUSIONS

Although NIR-II theranostic agents showed the great potential in diagnosis and treatment of AD, there are still many challenges: 1) Faborable NIR-II fluorohpores are still lacking; 2) Biocompatibility, bioseurity and dosage of NIR-II theranostic agents should be further revealed; 3) New equipment and software associated with NIR-II imaging system should be explored.

Advancements in boron difluoride formazanate dyes for biological imaging

In the past decade, boron difluoride formazanate dyes have gained considerable attention due to their redox activity, high absorption and emission intensities, chemical stability across a broad range of conditions, and the ease to fine-tune their optical and electronic characteristics. Over the past five years, boron difluoride formazanate dyes have demonstrated their extended emission wavelengths in the near-infrared region, suggesting their potential applications in the field of biological imaging. This review provides an overview of the evolution of boron difluoride formazanate dyes, encompassing the structural variations and corresponding optical properties, while also highlighting their current applications in biological imaging fields.

A probe for NIR-II imaging and multimodal analysis of early Alzheimer's disease by targeting CTGF

To date, earlier diagnosis of Alzheimer's disease (AD) is still challenging. Recent studies revealed the elevated expression of connective tissue growth factor (CTGF) in AD brain is an upstream regulator of amyloid-beta (Aβ) plaque, thus CTGF could be an earlier diagnostic biomarker of AD than Aβ plaque. Herein, we develop a peptide-coated gold nanocluster that specifically targets CTGF with high affinity (KD ~ 21.9 nM). The probe can well penetrate the blood-brain-barrier (BBB) of APP/PS1 transgenic mice at early-stage (earlier than 3-month-old) in vivo, allowing non-invasive NIR-II imaging of CTGF when there is no appearance of Aβ plaque deposition. Notably, this probe can also be applied to measuring CTGF on postmortem brain sections by multimodal analysis, including fluorescence imaging, peroxidase-like chromogenic imaging, and ICP-MS quantitation, which enables distinguishment between the brains of AD patients and healthy people. This probe possesses great potential for precise diagnosis of earlier AD before Aβ plaque formation.

Rational Design of NIR-II G-Quadruplex Fluorescent Probes for Accurate In Vivo Tumor Metastasis Imaging

Accurate in vivo imaging of G-quadruplexes (G4) is critical for understanding the emergence and progression of G4-associated diseases like cancer. However, existing in vivo G4 fluorescent probes primarily operate within the near-infrared region (NIR-I), which limits their application accuracy due to the short emission wavelength. The transition to second near-infrared (NIR-II) fluorescent imaging has been of significant interest, as it offers reduced autofluorescence and deeper tissue penetration, thereby facilitating more accurate in vivo imaging. Nonetheless, the advancement of NIR-II G4 probes has been impeded by the absence of effective probe design strategies. Herein, through a "step-by-step" rational design approach, we have successfully developed NIRG-2, the first small-molecule fluorescent probe with NIR-II emission tailored for in vivo G4 detection. Molecular docking calculations reveal that NIRG-2 forms stable hydrogen bonds and strong π-π interactions with G4 structures, which effectively inhibit twisted intramolecular charge transfer (TICT) and, thereby, selectively illuminate G4 structures. Due to its NIR-II emission (940 nm), large Stokes shift (90 nm), and high selectivity, NIRG-2 offers up to 47-fold fluorescence enhancement and a tissue imaging depth of 5 mm for in vivo G4 detection, significantly outperforming existing G4 probes. Utilizing NIRG-2, we have, for the first time, achieved high-contrast visualization of tumor metastasis through lymph nodes and precise tumor resection. Furthermore, NIRG-2 proves to be highly effective and reliable in evaluating surgical and drug treatment efficacy in cancer lymphatic metastasis models. We are optimistic that this study not only provides a crucial molecular tool for an in-depth understanding of G4-related diseases in vivo but also marks a promising strategy for the development of clinical NIR-II G4-activated probes.

Injectable-Hydrogel-Based Tissue Sealant for Hemostasis, Bacteria Inhibition, and Pro-Angiogenesis in Organ Bleeding Wounds and Therapeutic Outcome Monitoring Via NIR-II Optical Imaging

Sudden hemorrhage stemming from internal organ wounds poses a grave and potentially fatal risk if left untreated. Injectable-hydrogel-based tissue sealants featuring multiple actions, including fit-to-shape in situ gelation, rapid hemostasis, pro-angiogenic, anti-bacterial and outcome tracking, are ideal for the management of organ trauma wounds. Herein, an injectable-hydrogel tissue sealant AN@CD-PEG&TQ which consists of four-arm 4-arm poly(ethylene glycol) (PEG-SC) succinimidyl carbonate), AN@CD nanoprobe, and two bioactive peptides (anti-microbial peptide Tet213 and pro-angiogenic peptide QK) is developed. Among them, AN@CD nanoparticles form through host/guest complexation of amino-group-containing β-cyclodextrin and adamantyl group, enabling in situ biomarker (NO)-activatable optoacoustic/NIR-II: Near-infrared second biological window fluorescent imaging. The ample ─NH2 groups on the surface of AN@CD readily engage in rapid cross-linking with succinimidyl ester groups located at the ends of four-arm PEG-SC. This cross-linking expedites the gelation process without necessitating additional initiators or cross-linking agents; thus, significantly enhancing both hydrogel's application convenience and biocompatibility. Bioactive peptides (Tet213 and QK) safeguard against possible bacterial infections, facilitate angiogenesis, and eventually, improve organ wounds healing. This hydrogel-based tissue sealant demonstrates superior therapeutic and bioimaging performance in various mouse models including liver hemorrhage, gastric perforation, and bacterial-infected skin wound mouse models, highlighting its potential as a high-performance wound sealant for organ bleeding wound management.

Butyrylcholinesterase-Activated Near-Infrared Fluorogenic Probe for In Vivo Theranostics of Alzheimer's Disease

Butyrylcholinesterase (BChE) is a promising biomarker and effective therapeutic target for Alzheimer's disease (AD). Herein, we designed a BChE-activated near-infrared (NIR) probe, DTNP, which could be activated by BChE and inhibit its enzymatic activity. DTNP is composed of a cyclopropane moiety as the recognition unit, a NIR fluorophore hemicyanine as the NIR reporter, and a BChE inhibitor as the therapeutic unit. DTNP specifically binds BChE with high sensitivity and exhibits strong "turn-on" NIR fluorescence as well as nerve cell protection. In vivo imaging shows DTNP has favorable blood-brain barrier permeability and long-term tracking ability with preliminary competence in AD diagnosis. DTNP can significantly inhibit BChE activity, promote the release of ACh, and rescue learning deficits and cognitive impairment. Therefore, DTNP, the first reported and partially validated theranostic probe for the detection of BChE in AD, may provide a foundation and inspiration for imaging and therapy in AD.

Ultra-photostable small-molecule dyes facilitate near-infrared biophotonics

Long-wavelength, near-infrared small-molecule dyes are attractive in biophotonics. Conventionally, they rely on expanded aromatic structures for redshift, which comes at the cost of application performance such as photostability, cell permeability, and functionality. Here, we report a ground-state antiaromatic strategy and showcase the concise synthesis of 14 cationic aminofluorene dyes with mini structures (molecular weights: 299-504 Da) and distinct spectra covering 700-1600 nm. Aminofluorene dyes are cell-permeable and achieve rapid renal clearance via a simple 44 Da carboxylation. This accelerates optical diagnostics of renal injury by 50 min compared to existing macromolecular approaches. We develop a compact molecular sensing platform for in vivo intracellular sensing, and demonstrate the versatile applications of these dyes in multispectral fluorescence and optoacoustic imaging. We find that aromaticity reversal upon electronic excitation, as indicated by magnetic descriptors, not only reduces the energy bandgap but also induces strong vibronic coupling, resulting in ultrafast excited-state dynamics and unparalleled photostability. These results support the argument for ground-state antiaromaticity as a useful design rule of dye development, enabling performances essential for modern biophotonics.

Golgi-targeting viscosity probe for the diagnosis of Alzheimer's disease

Early diagnosis and intervention of Alzheimer's disease (AD) are particularly important to delay the pathological progression. Although fluorescent probes have been widely employed for investigating and diagnosing AD, their biological applications are significantly restricted due to the low penetration ability of the blood-brain barrier (BBB) in vivo. In this study, we reported the first Golgi-targeted two-photon (TP) fluorescent probe, DCM-DH, for detecting viscosity in the Golgi apparatus. The probe was rationally designed to exhibit superior analytical performance including high sensitivity, specific Golgi-targeting, efficient BBB penetration ability, and deep tissue penetration (247 μm) in the brains of AD model mice. Using the probe, we demonstrated that the fluorescence intensity in the human liver cancer cell (HepG2 cells) was higher than that of human normal liver cell (LO2 cells), and the brain viscosity of AD model mice increased significantly. We anticipate that this competent tool could be easily extended to other AD biomarkers for fundamental research on this detrimental disease.

Design of 2-Pyridone Fluorophores for Brighter Emissions at Longer Wavelengths

The recent discovery of blue fluorophores with high quantum yields based on pyridone structures inspired the development of new low-molecular-weight fluorophores with bright emissions at tunable wavelengths, which are highly attractive for various applications. In this study, we propose a rational design strategy for 2-pyridone-based fluorophores with bright emissions at long wavelengths. With a detailed understanding of the positional substitution effects on each carbon atom of the 2-pyridone core, we developed a bright blue fluorophore (λabs =377 nm; λem =433 nm; ϵ=13,200 M-1  cm-1 ; ϕF =88 %) through C3 -aryl and C4 -ester substitutions followed by cyclization. Furthermore, by applying the intramolecular charge transfer (ICT) principle, we invented a bright green fluorophore through C3 - and C4 -diester and C6 -aryl substitutions. The ICT fluorophore based on the pyridone structure shows large molar absorptivity (ϵ=20,100 M-1  cm-1 ), longer emission wavelength (λem =539 nm), high emission quantum yield (ϕF =74 %), and large Stokes shift (Δv=5720 cm-1 ), which are comparable to those of practical fluorescent probes.

J-Aggregation Strategy toward Potentiated NIR-II Fluorescence Bioimaging of Molecular Fluorophores

Molecular fluorophores emitting in the second near-infrared (NIR-II, 1000-1700 nm) window with strong optical harvesting and high quantum yields hold great potential for in vivo deep-tissue bioimaging and high-resolution biosensing. Recently, J-aggregates are harnessed to engineer long-wavelength NIR-II emitters and show unique superiority in tumor detection, vessel mapping, surgical navigation, and phototheranostics due to their bathochromic-shifted optical bands in the required slip-stacked arrangement aggregation state. However, despite the preliminary progress of NIR-II J-aggregates and theoretical study of structure-property relationships, further paradigms of NIR-II J-aggregates remain scarce due to the lack of study on aggregated fluorophores with slip-stacked fashion. In this effort, how to utilize the specific molecular structure to form slip-stacked packing motifs with J-type aggregated exciton coupling is emphatically elucidated. First, several molecular regulating strategies to achieve NIR-II J-aggregates containing intermolecular interactions and external conditions are positively summarized and deeply analyzed. Then, the recent reports on J-aggregates for NIR-II bioimaging and theranostics are systematically summarized to provide a clear reference and direction for promoting the development of NIR-II organic fluorophores. Eventually, the prospective efforts on ameliorating and promoting NIR-II J-aggregates to further clinical practices are outlined.

Dyads and Triads of Boron Difluoride Formazanate and Boron Difluoride Dipyrromethene Dyes

Dye-dye conjugates have attracted significant interest for their utility in applications such as bioimaging, theranostics, and light-harvesting. Many classes of organic dyes have been employed in this regard; however, building blocks don't typically extend beyond small chromophores. This can lead to minor changes to the optoelectronic properties of the original dye. The exploration of dye-dye structures is impeded by long synthetic routes, incompatible synthetic conditions, or a mismatch of the desired properties. Here, we present the first-of-their-kind dye-dye conjugates of boron difluoride complexes of formazanate and dipyrromethene ligands. These conjugates exhibit dual photoluminescence bands that reach the near-infrared spectral region and implicate anti-Kasha processes. Cyclic voltammetry experiments revealed the generation of polyanionic species that can reversibly tolerate the uptake of up to 6 electrons. Ultimately, we demonstrate that BF2 formazanates can serve as a synthetically accessible platform to build upon new classes of dye-dye conjugates.

Nanoparticles Mediated the Diagnosis and Therapy of Glioblastoma: Bypass or Cross the Blood-Brain Barrier

Glioblastoma is one of the most aggressive central nervous system malignancies with high morbidity and mortality. Current clinical approaches, including surgical resection, radiotherapy, and chemotherapy, are limited by the difficulty of targeting brain lesions accurately, leading to disease recurrence and fatal outcomes. The lack of effective treatments has prompted researchers to continuously explore novel therapeutic strategies. In recent years, nanomedicine has made remarkable progress and expanded its application in brain drug delivery, providing a new treatment for brain tumors. Against this background, this article reviews the application and progress of nanomedicine delivery systems in brain tumors. In this paper, the mechanism of nanomaterials crossing the blood-brain barrier is summarized. Furthermore, the specific application of nanotechnology in glioblastoma is discussed in depth.

Asymmetric aza-BODIPY photosensitizer for photoacoustic/photothermal imaging-guided synergistic photodynamic/photothermal therapy

Cancer synergistic therapy usually shows improved therapeutic efficacy with low side effects. In this contribution, an aza-BODIPY-derived photosensitizer NBDP with asymmetric structure and the periphery phenyl ring modified with bromine atom was designed and synthesized for synergistic photothermal therapy (PTT) and photodynamic therapy (PDT). Photosensitizer NBDP exhibited good singlet oxygen (1O2) generation capacity (1.43 times higher than that of ICG), and NBDP NPs showed an outstanding photothermal conversion efficiency (η) of 46.0% under 660 nm photoirradiation. Guided by in vivo photoacoustic (PA) imaging, NBDP NPs were found to targetedly accumulate in the tumor tissues in 6 h. All results showed that the aza-BODIPY-derived photosensitizer NBDP had great potential for PA/photothermal imaging-guided synergistic PTT/PDT.

Visualization detection of mycotoxin patulin in fruit juices by a small-molecule fluorescent probe

The mycotoxin patulin is a common contaminant in rotten fruits, posing severe food safety risks and threats to human health. Developing a convenient, sensitive and reliable method for patulin detection is of utmost importance but remains challenging. In this study, we have successfully designed and synthesized a small-molecule fluorescent probe, FITC-Lys, which demonstrates good sensitivity in detecting patulin. Upon contact with patulin, the terminal Lys group of the FITC-Lys probe reacts with patulin, resulting in the formation of the fluorescein dimer that subsequently quenches fluorescence. This variation of fluorescence enables the visualization and sensitive detection of patulin. The probe exhibits good sensitivity with a low LOD of 8 ng mL-1 for the fluorescence spectrum method and a LOD of 12 ng mL-1 for the fluorescence imaging method. Moreover, we have validated the probe's capability for patulin detection in apple and pear juices, achieving good recoveries ranging from 98.60% to 103.80%. Notably, the probe FITC-Lys is the first small-molecule fluorescent probe that has proven successful in visualizing patulin in juices derived from decayed apples and pears. Consequently, this probe holds great potential as a practical tool for monitoring patulin in foodstuffs, thereby contributing to enhanced food safety standards.

Shedding Light on Lysosomal Malondialdehyde Affecting Vitamin B12 Transport during Cerebral Ischemia/Reperfusion Injury

Cerebral ischemia-reperfusion injury (CIRI) is often accompanied by upregulation of homocysteine (Hcy). Excessive Hcy damages cerebral vascular endothelial cells and neurons, inducing neurotoxicity and even neurodegeneration. Normally, supplementation of vitamin B12 is an ideal intervention to reduce Hcy. However, vitamin B12 therapy is clinically inefficacious for CIRI. Considering oxidative stress is closely related to CIRI, the lysosome is the pivotal site for vitamin B12 transport. Lysosomal oxidative stress might hinder the transport of vitamin B12. Whether lysosomal malondialdehyde (lysosomal MDA), as the authoritative biomarker of lysosomal oxidative stress, interferes with the transport of vitamin B12 has not been elucidated. This is ascribed to the absence of effective methods for real-time and in situ measurement of lysosomal MDA within living brains. Herein, a fluorescence imaging agent, Lyso-MCBH, was constructed to specifically monitor lysosomal MDA by entering the brain and targeting the lysosome. Erupting the lysosomal MDA level in living brains of mice under CIRI was first observed using Lyso-MCBH. Excessive lysosomal MDA was found to affect the efficacy of vitamin B12 by blocking the transport of vitamin B12 from the lysosome to the cytoplasm. More importantly, the expression and function of the vitamin B12 transporter LMBD1 were proved to be associated with excessive lysosomal MDA. Altogether, the revealing of the lysosomal MDA-LMBD1 axis provides a cogent interpretation of the inefficacy of vitamin B12 in CIRI, which could be a prospective therapeutic target.

Hyperbranched Polymer Dots with Strong Absorption and High Fluorescence Quantum Yield for In Vivo NIR-II Imaging

In order to improve the fluorescence quantum yield (QY) of NIR-II-emitting nanoparticles, D-A-D fluorophores are typically linked to intramolecular rotatable units to reduce aggregation-induced quenching. However, incorporating such units often leads to a twisted molecular backbone, which affects the coupling within the D-A-D unit and, as a result, lowers the absorption. Here, we overcome this limitation by cross-linking the NIR-II fluorophores to form a 2D polymer network, which simultaneously achieves a high QY by well-controlled fluorophore separation and strong absorption by restricting intramolecular distortion. Using the strategy, we developed polymer dots with the highest NIR-II single-particle brightness among reported D-A-D-based nanoparticles and applied them for imaging of hindlimb vasculatures and tumors as well as fluorescence-guided tumor resection. The high brightness of the polymer dots offered exceptional image quality and excellent surgical results, showing a promising performance for these applications.

Revisiting molecularly conformation-planarized organic dyes for NIR-II fluorescence imaging

Fluorescence imaging in the second window (NIR-II, 1000-1700 nm) provides deeper penetration depth and higher resolution, but there is still a dilemma for designing NIR-II dyes for simultaneously enhancing fluorescence efficiency and prolonging excitation wavelength. Herein, a molecular conformation planarization strategy has been revisited to guide the synthesis of two donor-acceptor-donor dyes (named T-BBT and BT-BBT). On the one hand, conformational planarization can extend the absorption peaks of T-BBT and BT-BBT to the NIR region with high molar extinction coefficients of 30.5 × 103 and 16.4 × 103 L (mol-1 cm-1) at 1064 nm, respectively. On the other hand, structural rigidity can weaken electronic vibration coupling-related non-radiative decay pathways, whereby both T-BBT and BT-BBT display rather high fluorescence efficiencies of 3.6% and 13.5% in solution. Furthermore, a molecular doping strategy is adopted to alleviate fluorescence quenching in the aggregated state by suppressing long-distance energy migration, and 2.5 wt% doped BT-BBT nanoparticles show a high fluorescence efficiency of 2.0%, which enables the application of in vivo deep NIR-II fluorescence imaging for vessels and tumors with high resolution under 980 nm excitation. This work demonstrates that organic dyes with structural planarization can bridge the gap between NIR-II absorption and fluorescence efficiency.

Optical and Photoacoustic Imaging In Vivo: Opportunities and Challenges

Optical and photoacoustic imaging plays an important role in biomedical applications owing to its noninvasiveness and high resolution. Fluorescence imaging and photoacoustic imaging emerge as powerful tools to deconstruct molecular information and investigate biological processes in vivo. Despite great progress has been achieved in chemical probe synthesis, how to design probes with optimal fluorescence or photoacoustic imaging performance to dynamically visualize the biological process in vivo still faces challenges. From this perspective, we will focus on the advanced development of fluorescence and photoacoustic imaging in vivo. Furthermore, concerns and prospects for future imaging in vivo will be demonstrated.

Tracking of Intestinal Probiotics In Vivo by NIR-IIb Fluorescence Imaging

The ability to accurately characterize microorganism distribution in the intestinal tract is helpful for understanding intrinsic mechanisms. Within the intestine, traditional optical probes used for microorganism labeling commonly suffer from a low imaging penetration depth and poor resolution. We report a novel observation tool useful for microbial research by labeling near-infrared-IIb (NIR-IIb, 1500-1700 nm) lanthanide nanomaterials NaGdF4:Yb3+,Er3+@NaGdF4,Nd3+ (Er@Nd NPs) onto the surface of Lactobacillus bulgaricus (L. bulgaricus) via EDC-NHS chemistry. We monitor microorganisms in tissue by two-photon excitation (TPE) microscopy and in vivo with NIR-IIb imaging. This dual-technique approach offers great potential for determining the distribution of transplanted bacteria in the intestinal tract with a higher spatiotemporal resolution.

Homotypic Membrane-Enhanced Blood-Brain Barrier Crossing and Glioblastoma Targeting for Precise Surgical Resection and Photothermal Therapy

The crossing of blood-brain barrier (BBB) is essential for glioblastoma (GBM) therapy, and homotypic targeting is an effective strategy to achieve BBB crossing. In this work, GBM patient-derived tumor cell membrane (GBM-PDTCM) is prepared to cloak gold nanorods (AuNRs). Relying on the high homology of the GBM-PDTCM to the brain cell membrane, GBM-PDTCM@AuNRs realize efficient BBB crossing and selective GBM targeting. Meanwhile, owing to the functionalization of Raman reporter and lipophilic fluorophore, GBM-PDTCM@AuNRs are able to generate fluorescence and Raman signals at GBM lesion, and almost all tumor can be precisely resected in 15 min by the guidance of dual signals, ameliorating the surgical treatment for advanced GBM. In addition, photothermal therapy for orthotopic xenograft mice is accomplished by intravenous injection of GBM-PDTCM@AuNRs, doubling the median survival time of the mice, which improves the nonsurgical treatment for early GBM. Therefore, benefiting from homotypic membrane-enhanced BBB crossing and GBM targeting, all-stage GBM can be treated with GBM-PDTCM@AuNRs in distinct ways, providing an alternative idea for the therapy of tumor in the brain.