Precise and long-term tracking of adipose-derived stem cells and their regenerative capacity via superb bright and stable organic nanodots

Near-infrared-II fluorescence/magnetic resonance double modal imaging of transplanted stem cells using lanthanide co-doped gadolinium oxide nanoparticles

To ensure maximum therapeutic safety and efficacy of stem cell transplantation, it is essential to observe the kinetics of behavior, accumulation, and engraftment of transplanted stem cells in vivo. However, it is difficult to detect transplanted stem cells with high sensitivity by conventional in vivo imaging technologies. To diagnose the kinetics of transplanted stem cells, we prepared multifunctional nanoparticles, Gd2O3 co-doped with Er3+ and Yb3+ (Gd2O3: Er, Yb-NPs), and developed an in vivo double modal imaging technique with near-infrared-II (NIR-II) fluorescence imaging and magnetic resonance imaging (MRI) of stem cells using Gd2O3: Er, Yb-NPs. Gd2O3: Er, Yb-NPs were transduced into adipose tissue-derived stem cells (ASCs) through a simple incubation process without cytotoxicity under certain concentrations of Gd2O3: Er, Yb-NPs and were found not to affect the morphology of ASCs. ASCs labeled with Gd2O3: Er, Yb-NPs were transplanted subcutaneously onto the backs of mice, and successfully imaged with good contrast using an in vivo NIR-II fluorescence imaging and MRI system. These data suggest that Gd2O3: Er, Yb-NPs may be useful for in vivo double modal imaging with NIR-II fluorescence imaging and MRI of transplanted stem cells.

A Holistic Perspective on Living Aggregate

Aggregate is one of the most extensive existing modes of matters in the world. Besides the research objectives of inanimate systems in physical science, the entities in life science can be regarded as living aggregates, which are far from being thoroughly understood despite the great advances in molecular biology. Molecular biology follows the research philosophy of reductionism, which generally reduces the whole into parts to study. Although reductionism benefits the understanding of molecular behaviors, it encounters limitations when extending to the aggregate level. Holism is another epistemology comparable to reductionism, which studies objectives at the aggregate level, emphasizing the interactions and synergetic/antagonistic effects of a group of composed single entities in determining the characteristics of a whole. As a representative of holism, aggregation-induced emission (AIE) materials have made great achievements in the past two decades in both physical and life science. In particular, the unique properties of AIE materials endow them with in situ and real-time visual methods to investigate the inconsistency between microscopic molecules and macroscopic substances, offering researchers excellent toolkits to study living aggregates. The applications of AIE materials in life science are still in their infancy and worth expanding. In this Perspective, we summarize the research progress of AIE materials in unveiling some phenomena and processes of living systems, aiming to provide a general research approach from the viewpoint of holism. At last, insights into what we can do in the near future are also raised and discussed.

Fluorescence-Based Mono- and Multimodal Imaging for In Vivo Tracking of Mesenchymal Stem Cells

The advancement of stem cell therapy has offered transformative therapeutic outcomes for a wide array of diseases over the past decades. Consequently, stem cell tracking has become significant in revealing the mechanisms of action and ensuring safe and effective treatments. Fluorescence stands out as a promising choice for stem cell tracking due to its myriad advantages, including high resolution, real-time monitoring, and multi-fluorescence detection. Furthermore, combining fluorescence with other tracking modalities-such as bioluminescence imaging (BLI), positron emission tomography (PET), photoacoustic (PA), computed tomography (CT), and magnetic resonance (MR)-can address the limitations of single fluorescence detection. This review initially introduces stem cell tracking using fluorescence imaging, detailing various labeling strategies such as green fluorescence protein (GFP) tagging, fluorescence dye labeling, and nanoparticle uptake. Subsequently, we present several combinations of strategies for efficient and precise detection.

Enhancing NIR-II Imaging and Photothermal Therapy for Improved Oral Cancer Theranostics by Combining TICT and Aggregation-Induced Emission

In the treatment process of cancers like oral cancer, it is necessary to employ extensive surgical resection to achieve cancer eradication. However, this often results in damage to crucial functions such as chewing and speaking, leading to a poorer prognosis and a reduced quality of life. To address this issue, a multifunctional theranostic agent named MBPN-T-BTD has been developed by precisely modulating the excitation state energy distribution in the radiative/nonradiative decay pathways using the characteristics of twisted intramolecular charge transfer and aggregation-induced emission. This agent outperforms clinically utilized indocyanine green (ICG) in various aspects, including the second near-infrared window (NIR-II, 1000-1700 nm) fluorescence (FL) and photothermal conversion efficiency (PCE). Its nanoparticle form (BTB NPs) can be effectively used for high-contrast delineation of lymph node mapping and tongue and floor of mouth cancers using NIR-II FL, enabling surgeons to achieve more precise and thorough tumor clearance. For tumors located in close proximity to vital organs such as the tongue, the exceptional PCE (71.96%) of BTB NPs allows for targeted photothermal ablation with minimal damage to peripheral healthy tissues. This contribution provides a safer and more effective paradigm for minimally invasive or noninvasive treatment of oral cancer, ensuring the preservation of normal organ functions and showing potential for improving the overall prognosis and quality of life for cancer patients.

Small Molecules Temporarily Induce Neuronal Features in Adult Canine Dermal Fibroblasts

Several methods have been developed to generate neurons from other cell types for performing regeneration therapy and in vitro studies of central nerve disease. Small molecules (SMs) can efficiently induce neuronal features in human and rodent fibroblasts without transgenes. Although canines have been used as a spontaneous disease model of human central nerve, efficient neuronal reprogramming method of canine cells have not been well established. We aimed to induce neuronal features in adult canine dermal fibroblasts (ACDFs) by SMs and assess the permanency of these changes. ACDFs treated with eight SMs developed a round-shaped cell body with branching processes and expressed neuronal proteins, including βIII-tubulin, microtubule-associated protein 2 (MAP2), and neurofilament-medium. Transcriptome profiling revealed the upregulation of neuron-related genes, such as SNAP25 and GRIA4, and downregulation of fibroblast-related genes, such as COL12A1 and CCN5. Calcium fluorescent imaging demonstrated an increase in intracellular Ca2+ concentration upon stimulation with glutamate and KCl. Although neuronal features were induced similarly in basement membrane extract droplet culture, they diminished after culturing without SMs or in vivo transplantation into an injured spinal cord. In conclusion, SMs temporarily induce neuronal features in ACDFs. However, the analysis of bottlenecks in the neuronal induction is crucial for optimizing the process.

Ratiometric Fluorescence and Afterglow Lifetime Dual-Channel Nanoprobe for Simultaneous Imaging of HOCl and Temperature in Arthritis

Arthritis is a joint disorder that potentially causes permanent joint damage and eventual disability without effective treatment. Clinical detection methods, including in vitro blood tests and anatomical imaging, still have limitations in achieving real-time in situ early detection of arthritis. In this work, a dual-channel luminescence nanoprobe (AGNPs-Cy7) is reported, which combines a cyanine dye and a photochemical reaction-based afterglow system for real-time in vivo imaging of arthritis. AGNPs-Cy7 simultaneously detect hypochlorous acid (HOCl) and temperature, two important indicators associated with the early development of arthritis, by monitoring the respective changes in independent ratiometric fluorescence and afterglow lifetime signals. The anti-interference properties of both the ratiometric fluorescence signal and afterglow lifetime signal enhance sensing accuracy compared to the single luminescence intensity. The developed probe successfully reveals the simultaneous increase in HOCl concentration and temperature in an arthritis mouse model.

Design and synthesis of photostable triphenylamine based neutral AIE nano luminogens: specific and long-term tracking of mitochondria in cells

With the increasing dependence on fluorescence bioimaging, luminogens with aggregation-induced emission (AIE) properties have gained significant attention due to their excellent photostabilization, minimal photobleaching, high reliability, and superior biocompatibility. Since mitochondria are crucial subcellular organelles in eukaryotic cells with important biological functions, organelle-specific AIE emitters with distinct functions have been highly sought after, but with limited success using simple synthetic methods. Here, we describe a strategy for synthesizing two triphenylamine (TPA) based acrylonitriles, tethered to different donor groups, TPA and phenothiazine (PTZ), respectively, with superior AIE properties using Suzuki coupling. We conducted a systematic and detailed experimental analysis of the structural characteristics of both AIE luminogens, which exhibited excellent photostability, a large Stokes shift, and bright solid-state emission. A cell viability study carried out with F1 and F2 dyes revealed that both luminogens exhibited excellent biocompatibility. Based on fluorescence experiments, F2 displayed excellent AIE characteristics, permeability, biocompatibility, and photostability compared to rhodamine 123, allowing it to selectively stain and track mitochondria in cancer cells over an extended period of time. The Pearson correlation coefficient of F2 and rhodamine 123 was estimated to have an r-value of 0.99. Our findings are expected to provide insight into the synthesis of an extensive archive of AIE-based acrylonitriles with fascinating properties for mitochondrial staining.

Single-cell spatiotemporal analysis reveals cell fates and functions of transplanted mesenchymal stromal cells during bone repair

Mesenchymal stromal cells (MSCs) transplantation could enhance bone repair. However, the cell fate of transplanted MSCs, in terms of their local distribution and spatial associations with other types of cells were poorly understood. Here, we developed a single-cell 3D spatial correlation (sc3DSC) method to track transplanted MSCs based on deep tissue microscopy of fluorescent nanoparticles (fNPs) and immunofluorescence of key proteins. Locally delivered fNP-labeled MSCs enhanced tibial defect repair, increased the number of stem cells and vascular maturity in mice. fNP-MSCs persisted in the defect throughout repair. But only a small portion of transplanted cells underwent osteogenic differentiation (OSX+); a significant portion has maintained their expression of mesenchymal stem cell and skeletal stem cell markers (SCA-1 and PRRX1). Our results contribute to the optimization of MSC-based therapies. The sc3DSC method may be useful in studying cell-based therapies for the regeneration of other tissue types or disease models.

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Transplanted marrow stromal cells associated with vessels during bone defect repair

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Small proportion of transplanted cells differentiated into osteogenic cells

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A proportion of transplanted cells maintained expressions of stem cell markers

Celebrating 25 Years of IMRE: Research Highlights on Nanomaterials and Nanotechnologies

The Institute of Materials Research and Engineering (IMRE) is a research institute of the Science and Engineering Research Council (SERC), Agency for Science, Technology and Research (A*STAR). IMRE was established in September 1997. Over the past 25 years, IMRE has developed core competencies and interdisciplinary teams for material development from fundamental discoveries to industrial translation. Currently, with over 400 researchers and state-of-the-art research facilities, IMRE conducts world class research in important material and material technology fields, including polymer composites, optical materials, electronic materials, soft materials, structural materials, energy materials, biomaterials, quantum technologies, as well as advanced characterization. As a material-centered research institute in Singapore, IMRE has played important roles in pushing science boundaries and developing cutting-edge technologies. One of the key strategies is to partner international organizations, research institutes, and industry to fulfill its vision to be a leading research institute to accelerate materials research, moving from "Made in Singapore" toward "Created in Singapore".

Visualization of Acute Inflammation through a Macrophage-Camouflaged Afterglow Nanocomplex

Acute inflammation is a basic innate, immediate, and stereotyped immune response to injury, which is characterized by rapid recruitment of immune cells to the vasculature and extravasation into the damaged parenchyma. Visualization of acute inflammation plays an important role in monitoring the disease course and understanding pathogenesis, which lacks specific targeted and observing tools in vivo. Here, we report a Trojan horse strategy of a macrophage-camouflaged afterglow nanocomplex (UCANPs@RAW) to specifically visualize acute inflammation. Due to the advantages of optical antibackground interference elimination, as well as particular immune homing and long-term tracking capacity, UCANPs@RAW demonstrates an excellent acute inflammatory recognition ability. In an arthritis model, previously intravenously injected UCANPs@RAW could directionally migrate from the liver to the inflammation site as soon as 3 h after the model was induced, which could be continuously lighted for at least 36 h with the highest imaging signal-to-background ratio (SBR) as 382 at the time point of 9 h. Additionally, UCANPs@RAW is observed to penetrate the blood-brain barrier and image the deep brain inflamed region covered by the thick skull in an acute brain inflammation model with an SBR_max of 258, which is based on the strong recruiting ability of macrophages to immune response. In view of this smart nanocomplex, our strategy holds great potential for inflammatory detection and treatments.

In Vivo Micro-Computerized Tomography Tracking of Human Periodontal Ligament Stem Cells Labeled with Gold Nanocomplexes

Gold nanocomplexes have been proposed as contrast agents for computerized tomography (CT) and cell tracking, which is especially useful in stem cell therapy. However, their potential for long-term in vivo cell detection is still unknown. This study proposes an optimized approach to labeling human periodontal ligament stem cells (hPDLSCs) with gold nanocomplexes to evaluate their detection with micro-CT after transplantation at four different rat tissues. The gold nanocomplexes of 0.05 mg mL^-1 do not affect cell viability nor osteogenic differentiation capacity, but render fluorescent and radiopaque hPDLSCs. Excellent linear correlation with the number of labeled cells is shown over a wide range (r = 0.99, P < 0.01), with a detection limit of ≈1.2 × 10³ cells/µL. In vivo, strong, and durable detection of transplanted labeled cells within 5 days at all investigated areas is seen by micro-CT and immunohistochemical assay. This approach confirms the potential of gold nanocomplexes in longitudinal in vivo cell tracking, which may facilitate their application in CT image-guided interventions commonly used in oromaxillofacial or systemic applications of stem cell therapy.

A Multispectral Photoacoustic Tracking Strategy for Wide-Field and Real-Time Monitoring of Macrophages in Inflammation

Inflammation is a common defensive response of the vascular system that involves the activation and mediation of immune cell and stem cell homing. However, it is usually hard to track and analyze the real-time status of these cell types toward the inflammation microenvironment in a large field of view with desired resolution. Here, we designed and synthesized near-infrared absorbing semiconducting polymer nanoparticles, BBT-TQP-NP (BTNPs), as the cell tracker and utilized their photoacoustic activity to unveil the targeting behaviors of macrophages, neutrophils, and mesenchymal stem cells to the inflamed sites in mice. Facilitated by multispectral optical-resolution photoacoustic microscopy (ORPAM), we can continuously monitor the in vivo photoacoustic signals of the labeled cells with cellular resolution in a wide-field (a circle field-of-view with a diameter of 9 mm). In addition, the highly sensitive observation of vascular microstructures and labeled cells can reveal the time-dependent accumulating behaviors of various cell types toward inflammation sites. As a result, our study offers an effective and promising tracking strategy to analyze the in vivo status and fate of functional cells in targeting the diseased/damaged regions.

Aggregation-induced emission (AIE) nanoparticles labeled human embryonic stem cells (hESCs)-derived neurons for transplantation

Transplantation of differentiated neurons derived from either human embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs) is an emerging therapeutic strategy for various neurodegenerative diseases. One important aspect of transplantation is the accessibility to track and control the activity of the stem cells-derived neurons post-transplantation. Recently, the characteristics of organic nanoparticles (NPs) with aggregation-induced emission (AIE) have emerged as efficient cell labeling reagents, where positive outcomes were observed in long-term cancer cell tracing in vivo. In the current study, we designed, synthesized, and analyzed the biocompatibility of AIE-NPs in cultured neurons such as in mouse neuronal progenitor cells (NPCs) and hESC-derived neurons. Our data demonstrated that AIE-NPs show high degree of penetration into cells and presented intracellular long-term retention in vitro without altering the neuronal proliferation, differentiation, and viability. Furthermore, we have tracked AIE-NPs labeled neuronal grafts in mouse brain striatum in various time points post-transplantation. We demonstrated prolonged cellular retention of AIE-NPs labeled neuronal grafts 1 month post-transplantation in mouse brain striatum. Lastly, we have shown activation of brain microglia in response to AIE-NPs labeled grafts. Together, these findings highlight the potential application of AIE-NPs in neuronal transplantation.

The glucagon-like peptide-1 (GLP-1) analog exenatide ameliorates intrauterine adhesions in mice

OBJECTIVE

The purpose of the experiments in this study was to explore the effect of exenatide on intrauterine adhesions (IUAs) and to elucidate its mechanism to provide new ideas for the clinical treatment of IUAs.

METHODS

In this study, an animal model of IUAs was established by double stimulation using mechanical curettage and inflammation. After modeling, the treatment group was injected subcutaneously with three doses of exenatide for two weeks. The model group was injected with sterile ultrapure water, and the sham operation group was treated the same as the normal group, except for the observation of abdominal wound changes. Two weeks later, all mice were sacrificed by cervical dysfunction. The obtained mouse uterine tissue was used for subsequent experimental detection, using HE and Masson staining for histomorphological and pathological analysis; qRT-PCR for the detection of TGF-β1, α-SMA, and MMP-9 gene expression in uterine tissue; and western blotting analysis of TGF-β1, α-SMA, and collagen 1 protein expression to verify whether exenatide has a therapeutic effect on IUAs in mice.

RESULTS

In the high-dose exenatide treatment group, the endometrial glands significantly increased in size, and the deposition area of collagen fibers in the endometrial tissue was significantly reduced. We observed that the mRNA expression of TGF-β1 and α-SMA in the endometrial tissue of IUAs mice in this group was significantly reduced, while the expression of MMP-9 was significantly increased. In addition, we found that the protein expression of TGF-β1, α-SMA, and collagen 1 remarkably decreased after treatment with exenatide.

CONCLUSION

Exenatide may reduce the deposition of collagen fibers in the uterus of IUAs mice and promote the proliferation of endometrial glands in mice.

A two-in-one Janus NIR-II AIEgen with balanced absorption and emission for image-guided precision surgery

Fluorescence imaging in the near-infrared II (NIR-II, 1000-1700 nm) region opens up new avenues for biological systems due to suppressed scattering and low autofluorescence at longer-wavelength photons. Nonetheless, the development of organic NIR-II fluorophores is still limited mainly due to the shortage of efficient molecular design strategy. Herein, we propose an approach of designing Janus NIR-II fluorophores by introducing electronic donors with distinct properties into one molecule. As a proof-of-concept, fluorescent dye 2 TT-m, oC6B with both twisted and planar electronic donors displayed balanced absorption and emission which were absent in its parent compound. The key design strategy for Janus molecule is that it combines the merits of intense absorption from planar architecture and high fluorescence quantum yield from twisted motif. The resulting 2 TT-m, oC6B nanoparticles exhibit a high molar absorptivity of 1.12 ⨯104 M-1 cm-1 at 808 nm and a NIR-II quantum yield of 3.7%, displaying a typical aggregation-induced emission (AIE) attribute. The highly bright and stable 2 TT-m, oC6B nanoparticles assured NIR-II image-guided cancer surgery to resect submillimeter tumor nodules. The present study may inspire further development of molecular design philosophy for highly bright NIR-II fluorophores for biomedical applications.

A mechanistic insight into benefits of aggregation induced emissive luminogens in cancer

Exploration of advanced chemotheranostics that benefit from a combined in vivo strategy of cancer diagnosis and chemotherapy simultaneously is highly valued and will expose novel possibilities in modifying treatment and reduce side effects. In recent years, nanodrug delivery systems that incorporate aggregation-induced emissive luminogens (AIEgens) have been developed to track and monitor anticancer drug release, trace translocation processes and predict chemotherapeutic responses. There are several classes of AIEgen based chemotheranostics such us stimuli-responsive nanoprodrugs, pH-sensitive mesoporous silica nanocarriers, supramolecular polymer systems, drug encapsulated carriers, carrier-free nanodrugs, self-indicating drug delivery nanomachines and AIEgen-prodrug co-assembly. The present review conveys mechanistic insight into the benefits of AIEgens in the theranostic application by illustrating the recent breakthroughs in chemotheranostic nanomedicines that incorporate these unique fluorophores as signal reporters. The perspectives that can be further explored are also highlighted with the hope to instil more research interest in the advancement of AIE active cancer chemotheranostics for imaging and treatment in vivo.HIGHLIGHTSAggregation induced emissive materials (AIEgens) exhibit unique advantages over conventional luminogens for synergistic diagnosis and chemotherapy of cancer in vivo.The combination of AIE and nanotechnology offers an excellent platform to fabricate advanced chemotheranostics for cancer therapy.

Diagnostic and Therapeutic Nanomedicine

Nanotechnology has been widely applied to medical interventions for prevention, diagnostics, and therapeutics of diseases, and the application of nanotechnology for medical purposes, which is called as a term "nanomedicine" has received tremendous attention. In particular, the design and development of nanoparticle for biosensors have received a great deal of attention, since those are most impactful area of clinical translation showing potential breakthrough in early diagnosis of diseases such as cancers and infections. For example, the nanoparticles that have intrinsic unique features such as magnetic responsive characteristics or photoluminescence can be utilized for noninvasive visualization of inner body. Drug delivery that makes use of drug-containing nanoparticles as a carrier is another field of study, in which the particulate form nanomedicine is given by parenteral administration for further systemic targeting to pathological tissues. In addition, encapsulation into nanoparticles gives the opportunity to secure the sensitive therapeutic payloads that are readily degraded or deactivated until reached to the target in biological environments, or to provide sufficient solubilization (e.g., to deliver compounds which have physicochemical properties that strongly limit their aqueous solubility and therefore systemic bioavailability). The nanomedicine is further intended to enhance the targeting index such as increased specificity and reduced false binding, thus improve the diagnostic and therapeutic performances. In this chapter, principles of nanomaterials for medicine will be thoroughly covered with applications for imaging-based diagnostics and therapeutics.

Transplantation of Human Amnion Epithelial Cells Improves Endometrial Regeneration in Rat Model of Intrauterine Adhesions

Intrauterine adhesions (IUAs) are characterized by the injury of endometrium due to curettage and/or endometritis. The loss of functional endometrium in uterine cavity usually results in hypomenorrhea, amenorrhea, infertility, and/or recurrent pregnancy loss. Recently, stem cell transplantation has been applied to promote the endometrial regeneration. Human amnion epithelial cells (hAECs) have been shown to have stem cell characteristics. In this study, we found that PKH26-labeled hAECs were mainly distributed in the basal layer of endometrium after transplantation, and hAEC transplantation, including uterine injection and tail vein injection, could increase pregnancy rate and the number of embryos in rat model of IUAs. Moreover, hAEC transplantation was demonstrated to increase the endometrial thickness, promote the proliferation of glands and blood vessels, and decrease fibrotic areas in the endometrium. The immunohistochemical and quantitative polymerase chain reaction analysis showed the upregulated expression of growth factors, such as basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF-1) after hAEC transplantation; and the downregulated expression of collagen type I alpha 1 (COL1A1), tissue inhibitor of metalloproteinase-1 (TIMP-1), and transforming growth factor-β (TGF-β), all of which are associated with the extracellular matrix (ECM) deposition after hAEC transplantation. The mRNA sequencing indicated that platelet-derived growth factor-C (PDGF-C), thrombospondin-1 (THBS1), connective tissue growth factor (CTGF), Wnt5a, and Snai2 were significantly modulated in treatment groups. These results indicate that hAEC transplantation promotes endometrial regeneration and the restoration of fertility in rat model of IUAs.

Adipose tissue-derived stromal cells stimulated macrophages-endothelial cells interactions promote effective ischemic muscle neovascularization

Neovascularization, the process of new blood vessels formation in response to hypoxia induced signals, is an essential step during wound healing or ischemia repair. It follows as a cascade of consecutive events leading to new blood vessels formation and their subsequent remodeling to a mature and functional state, enabling tissue regeneration. Any disruption in consecutive stages of neovascularization can lead to chronic wounds or impairment of tissue repair. In the study we try to explain the biological basis of accelerated blood vessels formation in ischemic tissue after adipose tissue-derived stromal cells (ADSCs) administration. Experiments were performed on mouse models of hindlimb ischemia. We have evaluated the level of immune cells (neutrophils, macrophages) infiltration. The novelty of our work was the assessment of bone marrow-derived stem/progenitor cells (BMDCs) infiltration and their contribution to the neovascularization process in ischemic tissue. We have noticed that ADSCs regulated immune response and affected the kinetics and ratio of macrophages population infiltrating ischemic tissue. Our research revealed that ADSCs promoted changes in the morphology of infiltrating macrophages and their tight association with forming blood vessels. We assume that recruited macrophages may take over the role of pericytes and stabilize the new blood vessel or even differentiate into endothelial cells, which in consequence can accelerate vascular formation upon ADSCs administration. Our findings indicate that administration of ADSCs into ischemic muscle influence spatio-temporal distribution of infiltrating cells (macrophages, neutrophils and BMDCs), which are involved in each step of vascular formation, promoting effective ischemic tissue neovascularization.

Particle-based artificial three-dimensional stem cell spheroids for revascularization of ischemic diseases

Development of new approaches to biomimetically reconstruct vasculature networks remains challenging in regenerative medicine. We introduce a particle-based artificial stem cell spheroid (ASSP) technology that recapitulates paracrine functions of three-dimensional (3D) SSPs for vasculature regeneration. Specifically, we used a facile method to induce the aggregation of stem cells into 3D spheroids, which benefited from hypoxia microenvironment-driven and enhanced secretion of proangiogenic bioactive factors. Furthermore, we artificially reconstructed 3D spheroids (i.e., ASSP) by integration of SSP-secreted factors into micro-/nanoparticles with cell membrane-derived surface coatings. The easily controllable sizes of the ASSP particles provided superior revascularization effects on the ischemic tissues in hindlimb ischemia models through local administration of ASSP microparticles and in myocardial infarction models via the systemic delivery of ASSP nanoparticles. The strategy offers a promising therapeutic option for ischemic tissue regeneration and addresses issues faced by the bottlenecked development in the delivery of stem cell therapies.

Decellularized Aortic Scaffold Alleviates H2O2-Induced Inflammation and Apoptosis in CD34+ Progenitor Cells While Driving Neovasculogenesis

Bone marrow-derived stem/progenitor cells have been utilized for cardiac or vascular repair after ischemic injury, but they are subject to apoptosis and immune rejection in the ischemic site. Multiple scaffolds were used as delivery tools to transplant stem/progenitor cells; however, these scaffolds did not show intrinsically antiapoptotic or anti-inflammatory properties. Decellularized aortic scaffolds that facilitate cell delivery and tissue repair were prepared by removing cells of patient-derived aortic tissues. Scanning electron microscopy (SEM) showed cells attached well to the scaffold after culturing for 5 days. Live/dead staining showed most seeded cells survived at day 7 on a decellularized aortic scaffold. Ki67 staining demonstrated that decellularized aortic scaffold promoted proliferation of bone marrow-derived CD34+ progenitor cells. Apoptosis of CD34+ progenitor cells induced by H₂O₂ at high concentration was significantly alleviated in the presence of decellularized aortic scaffolds, demonstrating a protective effect against oxidative stress-induced apoptosis. Furthermore, decellularized aortic scaffolds significantly reduced the expression of proinflammatory cytokines (IL-8, GM-CSF, MIP-1β, GRO-α, Entoxin, and GRO) concurrently with an increase in anti-inflammatory cytokines (IL-2 and TGF-β) released from CD34+ progenitor cells when exposed to H₂O₂ at low concentration. Finally, neovascularization was observed by H&E and immunohistochemical staining 14 days after the decellularized aortic scaffolds were subcutaneously implanted in nude mice. This preclinical study demonstrates that the use of a decellularized aortic scaffold possessing antiapoptotic and anti-inflammatory properties may represent a promising strategy for cardiovascular repair after ischemic injury.

Nanoparticle-based Cell Trackers for Biomedical Applications

The continuous or real-time tracking of biological processes using biocompatible contrast agents over a certain period of time is vital for precise diagnosis and treatment, such as monitoring tissue regeneration after stem cell transplantation, understanding the genesis, development, invasion and metastasis of cancer and so on. The rationally designed nanoparticles, including aggregation-induced emission (AIE) dots, inorganic quantum dots (QDs), nanodiamonds, superparamagnetic iron oxide nanoparticles (SPIONs), and semiconducting polymer nanoparticles (SPNs), have been explored to meet this urgent need. In this review, the development and application of these nanoparticle-based cell trackers for a variety of imaging technologies, including fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, magnetic particle imaging, positron emission tomography and single photon emission computing tomography are discussed in detail. Moreover, the further therapeutic treatments using multi-functional trackers endowed with photodynamic and photothermal modalities are also introduced to provide a comprehensive perspective in this promising research field.

AIE/FRET-based versatile PEG-Pep-TPE/DOX nanoparticles for cancer therapy and real-time drug release monitoring

Based on the biological significance of self-assembling peptides in program cell death, promoting proliferation of stem cells and suppressing immune responses, stimuli-responsive polypeptide nanoparticles have attracted more and more attention.

Heat Shock Protein Inspired Nanochaperones Restore Amyloid-β Homeostasis for Preventative Therapy of Alzheimer's Disease

Amyloid beta (Aβ) aggregation is generally believed as the crucial and primary cause of Alzheimer's disease (AD). However, current Aβ-targeted therapeutic strategies show limited disease-modifying efficacy due to the irreversible damages in the late stage of AD, thus the treatment should be given before the formation of deposition and target primary Aβ species rather than advanced plaques. Herein, inspired by heat shock protein, a self-assembly nanochaperone based on mixed-shell polymeric micelle (MSPM) is devised to act as a novel strategy for AD prevention. With unique surface hydrophobic domains, this nanochaperone can selectively capture Aβ peptides, effectively suppress Aβ aggregation, and remarkably reduce Aβ-mediated cytotoxicity. Moreover, the formed nanochaperone-Aβ complex after Aβ adsorption can be easily phagocytosed by microglia and thereby facilitates Aβ clearance. As a result, the nanochaperone reduces Aβ burden, attenuates Aβ-induced inflammation, and eventually rescues the cognitive deficits of APP/PS1 transgenic AD mice. These results indicate that this biomimetic nanochaperone can successfully prevent the onset of AD symptoms and serve as a promising candidate for prophylactic treatment of AD.

A new approach to developing diagnostics and therapeutics: Aggregation-induced emission-based fluorescence turn-on

Fluorescence imaging is a promising visualization tool and possesses the advantages of in situ response and facile operation; thus, it is widely exploited for bioassays. However, traditional fluorophores suffer from concentration limits because they are always quenched when they aggregate, which impedes applications, especially for trace analysis and real-time monitoring. Recently, novel molecules with aggregation-induced emission (AIE) characteristics were developed to solve the problems encountered when using traditional organic dyes, because these new molecules exhibit weak or even no fluorescence when they are in free movement states but emit intensely upon the restriction of intramolecular motions. Inspired by the excellent performances of AIE molecules, a substantial number of AIE-based probes have been designed, synthesized, and applied to various fields to fulfill diverse detection tasks. According to numerous experiments, AIE probes are more practical than traditional fluorescent probes, especially when used in bioassays. To bridge bioimaging and materials engineering, this review provides a comprehensive understanding of the development of AIE bioprobes. It begins with a summary of mechanisms of the AIE phenomenon. Then, the strategies to realize accurate detection using AIE probes are discussed. In addition, typical examples of AIE-active materials applied in diagnosis, treatment, and nanocarrier tracking are presented. In addition, some challenges are put forward to inspire more ideas in the promising field of AIE-active materials.

In Vivo Real-Time Imaging of Extracellular Vesicles in Liver Regeneration via Aggregation-Induced Emission Luminogens

Extracellular vesicles (EVs) attract much attention in liver pathology because they regulate cell-cell communication and many pathophysiological events by transferring their cargos. Monitoring and understanding the in vivo fate and therapeutic capacity of these EVs is critical for the development and optimization of EV-based diagnosis and therapy. Herein, we demonstrate the use of an aggregation-induced emission luminogen, DPA-SCP, for the real-time tracking of EVs derived from human placenta-derived mesenchymal stem cells (MSCs) and their therapeutic effects in a mouse acute liver injury (ALI) model. In vitro, DPA-SCP does not alter the inherent characteristics of MSC-derived EVs and shows extremely low toxicity. Moreover, DPA-SCP exhibited superior labeling efficiency and tracking capability to the most popular commercial EV trackers, PKH26 and DiI. In vivo, DPA-SCP precisely and quantitatively tracked the behaviors of EVs for 7 days in the mouse ALI model without influencing their regenerative capacity and therapeutic efficacy. The therapeutic effects of EVs may attribute to their ability for reducing inflammatory cell infiltration, enhancing cell survival and antiapoptotic effects. In conclusion, DPA-SCP with an AIE signature serves as a favorable and safe tracker for in vivo real-time imaging of EVs in liver regeneration.

Highly efficient photothermal nanoagent achieved by harvesting energy via excited-state intramolecular motion within nanoparticles

The exciting applications of molecular motion are still limited and are in urgent pursuit, although some fascinating concepts such as molecular motors and molecular machines have been proposed for years. Utilizing molecular motion in a nanoplatform for practical application has been scarcely explored due to some unconquered challenges such as how to achieve effective molecular motion in the aggregate state within nanoparticles. Here, we introduce a class of near infrared-absorbing organic molecules with intramolecular motion-induced photothermy inside nanoparticles, which enables most absorbed light energy to dissipate as heat. Such a property makes the nanoparticles a superior photoacoustic imaging agent compared to widely used methylene blue and semiconducting polymer nanoparticles and allow them for high-contrast photoacoustic imaging of tumours in live mice. This study not only provides a strategy for developing advanced photothermal/photoacoustic imaging nanoagents, but also enables molecular motion in a nanoplatform to find a way for practical application.

Fabrication and Application of Dual-Modality Polymer Nanoparticles Based on an Aggregation-Induced Emission-Active Fluorescent Molecule and Magnetic Fe₃O₄

Fluorescent magnetic nanoparticles (NPs) utilized for imaging hold great promise for biomedical applications, but it remains a challenging task. Here, we report novel dual-modality NPs using an aggregation-induced emission (AIE)-active and near-infrared (NIR) emissive dye (TPAS) and magnetic Fe₃O₄ as the core, and biocompatible polymer Pluronic F-127 as the encapsulation matrix by self-assembly procedures. The obtained fluorescent-magnetic AIE NPs have both high fluorescence quantum yield (13.8%) at 700 nm and high magnetic saturation value. With good photostability and biocompatibility, the resulting NPs show effective MRI ability, but also a stain in cytoplasm with a strong NIR fluorescent signal.

Nanoscale vesicles assembled from non-planar cyclic molecules for efficient cell penetration

A new approach to the development of functional biomaterials is to obtain a controllable nanostructure through supramolecular self-assembly.

Far-Red/Near-Infrared Emissive (1,3-Dimethyl)barbituric Acid-Based AIEgens for High-Contrast Detection of Metastatic Tumors in the Lung

Despite of the enthusiastic research in aggregation-induced emission luminogens (AIEgens) in recent years, the ones that can be smoothly used for sophisticated biomedical applications such as in vivo bioimaging of pulmonary metastatic tumors during surgery are still limited. Herein, we report the design and synthesis of a new series of far-red/near-infrared (FR/NIR) fluorescent AIEgens that consist of methoxy-substituted tetraphenylethene (TPE) as the electron-donating moiety, (1,3-dimethyl)barbituric acid as the electron-withdrawing moiety, and different π-bridge units. As compared to benzene or 3,4-ethylenedioxythiophene, using thiophene as the π-conjugation unit between the donor and acceptor results in a relatively higher absolute fluorescence quantum yield (14.5 %) in water when formulating the corresponding AIEgens into nanoparticles (AIE dots) with an amphiphilic co-polymer as the doping matrix. The highly FR/NIR-emissive thiophene-based AIE dots are demonstrated to be potent for intraoperative detection of pulmonary metastatic tumors, particularly the micro-sized ones, with excellent signal-to-background ratio.

Chiral molecular face-rotating sandwich structures constructed through restricting the phenyl flipping of tetraphenylethylene

Chiral tetraphenylethylene (TPE) derivatives have great potential in chiral recognition and circularly polarized luminescence. However, they were mainly constructed through introducing chiral substituents at the periphery of the TPE moiety, which required additional chemical modifications and limited the variety of chiralities of products. Herein, we constructed a series of chiral face-rotating sandwich structures (FRSs) through restricting the phenyl flipping of TPE without introducing any chiral substituents. In FRSs, the complex arrangements of TPE motifs resulted in a variety of chiralities. We also found that non-covalent repulsive interactions in vertices caused the facial hetero-directionality of FRSs, and the hydrogen bonds between imine bonds and hydroxy groups induced excited-state intramolecular proton transfer (ESIPT) emission of FRSs. In addition, the fluorescence intensity of FRSs decreases with the addition of trifluoroacetic acid. This study provides new insights into the rational design of chiral assemblies from aggregation-induced emission (AIE) active building blocks through restriction of intramolecular rotation (RIR).

Single-Molecular Near-Infrared-II Theranostic Systems: Ultrastable Aggregation-Induced Emission Nanoparticles for Long-Term Tracing and Efficient Photothermal Therapy

Second near-infrared (NIR-II, 1000-1700 nm) fluorescence bioimaging has attracted tremendous scientific interest and already been used in many biomedical studies. However, reports on organic NIR-II fluorescent probes for in vivo photoinduced imaging and simultaneous therapy, as well as the long-term tracing of specific biological objects, are still very rare. Herein we designed a single-molecular and NIR-II-emissive theranostic system by encapsulating a kind of aggregation-induced emission luminogen (AIEgen, named BPN-BBTD) with amphiphilic polymer. The ultra-stable BPN-BBTD nanoparticles were employed for the NIR-II fluorescence imaging and photothermal therapy of bladder tumors in vivo. The 785 nm excitation triggered photothermal therapy could completely eradicate the subcutaneous tumor and inhibit the growth of orthotopic tumors. Furthermore, BPN-BBTD nanoparticles were capable of monitoring subcutaneous and orthotopic tumors for a long time (32 days). Single-molecular and NIR-II-emitted aggregation-induced emission nanoparticles hold potential for the diagnosis, precise treatment, and metastasis monitoring of tumors in the future.

Aggregation-Induced Emission Luminogens: Union Is Strength, Gathering Illuminates Healthcare

The rapid development of healthcare techniques encourages the emergence of new molecular imaging agents and modalities. Fluorescence imaging that enables precise monitoring and detection of biological processes/diseases is extensively investigated as this imaging technique has strengths in terms of high sensitivity, excellent temporal resolution, low cost, and good safety. Aggregation-induced emission luminogens (AIEgens) have recently emerged as a new class of emitters that possess several notable features, such as high brightness, large Stokes shift, marked photostability, good biocompatibility, and so on. So far, AIEgens are widely explored and exhibit superb performance in the area of biomedicine and life sciences. Herein, this review summarizes and discusses the recent investigations of AIEgens for in vivo diagnosis and therapy including long-term tracking, 3D angiography, multimodality imaging, disease theranostics, and activatable sensing. Collectively, these results reveal that AIEgens are of great promise for in vivo biomedical applications. It is hoped that this review will lead to new insights into the development of advanced healthcare materials.