Bioactive NIR-II gold clusters for three-dimensional imaging and acute inflammation inhibition

Molecular Gold Nanoclusters for Advanced NIR-II Bioimaging and Therapy

Small thiolate-protected gold molecular clusters have gained significant interest in research due to their unique size-dependent properties. Their molecular to nanoscale sizes lead to distinctive quantum confinement effects, resulting in a discrete electronic energy band gap structure and molecule-like properties, including HOMO-LUMO electronic transitions, enhanced photoluminescence, and intrinsic magnetism and chirality. Near-infrared II (NIR-II, 1000-3000 nm) emissive gold clusters have emerged as a fascinating class of nanomaterials that are well-suited for biomedical applications. The unique combination of stability, biocompatibility, and tunable emission properties position them as valuable tools for high-resolution and deep-tissue imaging, with potential real-world applications ranging from disease diagnostics and prognosis to therapeutics. In this review, we focus on the NIR-II photoluminescence properties of gold molecular clusters for preclinical in vivo NIR-II imaging of vasculature, brain, kidney, liver, and gastrointestinal organs, and molecular targeted tumor imaging and theranostic treatment. The imaging capabilities combined with fast excretion and a high safety profile make molecular gold clusters highly promising for clinical translation.

A Nucleus-Targeting Ruthenium(II) Complex Induces DNA Condensation in Cisplatin-Resistant Tumor Cells

One of the conventional ways to eradicate tumor cells is to utilize chemotherapy agents, e.g., cisplatin, to induce DNA damage. However, DNA damage repair mechanisms can significantly limit the therapeutic efficacy of cisplatin. These mechanisms enable tumor cells to repair the DNA damage caused by the drug, leading to resistance. Cisplatin and similar drugs bind to specific DNA sites without significantly altering their conformation. As a result, DNA repair enzymes can still attach to and repair the damaged DNA. To address this issue, we designed four Ru(II) complexes (RuC3, RuC6, RuC9, and RuC12) with high positive charges of +8 valence and regulated their nuclear accumulation levels by adjusting the length of alkyl chains. RuC9 exhibits the highest nucleus accumulation level. DNA conformation was significantly altered by inducing DNA condensation through indiscriminately neutralizing the negative charge of the DNA backbone. This significant change prevents DNA-related enzymes from binding to DNA, ultimately leading to the efficient eradication of various tumor cell lines. To the best of our knowledge, it is the first work that kills tumor cells and overcomes cisplatin resistance through inducing DNA condensation.

Engineering ultrasmall gold nanoclusters: tailored optical modulation for phototherapeutic and multimodal biomedical applications

Ultrasmall gold nanoclusters (Au NCs) with core sizes below 2 nm exhibit distinctive physicochemical properties and hold remarkable promise in a variety of biomedical applications. Through precise synthesis and surface engineering, Au NCs can be endowed with high quantum yields, excellent stability, and favorable biocompatibility. Recent studies have demonstrated the versatility of Au NCs in imaging modalities-ranging from fluorescence and Raman to photoacoustics-as well as in light-driven therapeutics such as photodynamic therapy (PDT) and photothermal therapy (PTT). This review provides an overview of Au NC design strategies, highlighting ligand-assisted synthesis and supramolecular self-assembly for optimizing optical features and biological performance. Representative biomedical applications in optical imaging, biosensing, and phototherapy are summarized to illustrate the multifaceted benefits of Au NCs in disease diagnosis and treatment. Finally, challenges related to large-scale production, long-term biosafety, and clinical translation are discussed, along with future perspectives on leveraging Au NCs for next-generation theranostic platforms.

Unprecedented stacking-dependent piezoluminescence enhancement in atomically precise superatomic gold nanoclusters

Deciphering the structure-property relationship between cluster stacking and high-efficiency luminescence of metal nanoclusters is crucial for designing and synthesizing high-performance light-emitting materials and devices. Here, we successfully synthesized two polymorphic gold nanoclusters (Au8-C and Au8-P) and investigated their stacking-dependent piezoluminescence based on hydrostatic pressure. Under compression, Au8-C exhibits notable piezoluminescence enhancement. However, Au8-P presents monotonic piezoluminescence quenching. High-pressure structural characterizations confirm the existence of stacking-dependent anisotropic compression in Au8-C and Au8-P. Under high pressure, the columnar-stacked Au8-C shrinks faster along the a axis, increasing the aspect ratio (AR) of the fusiform Au8 core. However, the layered Au8-P is compressed faster along the c axis, reducing the AR and leading to a flatter Au8 core. High-pressure femtosecond transient absorption, time-resolved photoluminescence, and Raman spectra collaboratively confirm that differentiated anisotropic compression notably suppresses nonradiative loss caused by low-frequency vibrations of the Au8 core, which is responsible for the piezoluminescence enhancement in Au8-C.

Janus Gold Nanodiscs with an Asymmetrically Positioned Polyaniline Nano-Urchin for Photothermal Therapy and Multimodal Imaging in the Second Near-Infrared Window

The second near-infrared (NIR-II) window (1000-1700 nm) offers advantages in biomedical applications such as deeper tissue penetration and superior imaging contrast. Despite this potential, existing NIR-II probes are limited by biocompatibility concerns, photobleaching, and poor photostability, issues that constrain their clinical utility. This study introduces Janus-type gold nanodiscs having an asymmetrically integrated hierarchical polyaniline (PANI) structure, optimized for use as multifunctional agents for NIR-II photothermal therapy and multimodal imaging. By shifting the localized surface plasmon resonance of the gold nanodiscs─the foundation of the Janus structure─from NIR-I to NIR-II, the developed AuPANI nanodiscs achieve remarkable deep-tissue photoacoustic imaging, up to 15 mm, while also enabling highly sensitive positron emission tomography imaging through stable radiolabeling. The nanodiscs also exhibit superior photostability and notable efficacy as photoacoustic-guided photothermal therapy agents under 1064 nm irradiation. This study positions AuPANI nanodiscs as a versatile platform for NIR-II theranostics, addressing limitations of current probes and advancing their potential for precise and effective cancer treatment.

Communications Among Neurocytes in Parkinson's Disease Regulated by Differential Metabolism and Blood-Brain Barrier Traversing of Chiral Gold Cluster-MOF Integrated Nanoparticles

This study have previously reported that ZIF-based chiral nanomedicines achieve Parkinson's disease (PD) therapy through differential metabolism and relief of neuroinflammation. However, lack of overall chirality and anti-inflammatory capacity of nanomedicines limit the further effective solution to the nanobiological effects research in PD. Here, it dexterously loaded chiral gold nanoclusters (AuNCs) onto the inner and outer surfaces of ZIF to achieve the purpose of simultaneously improving the overall chirality and anti-inflammatory activity of the composite nanoparticles (NPs). There are significant differences in the composition of protein corona between different chiral NPs, which elucidates the mechanism of chiral-mediated discrepancies in metabolism and the blood-brain barrier (BBB) traversing. Multi-omics and biochemical techniques further reveal that chiral NPs interfere with the chemokine axis (CX3CL1/CX3CR1)-NF-κB-NLRP3 and PI3K-AKT signaling pathways, regulate communications between neurons, neural stem cells and microglia ("the three-body problem"), and induce anti-inflammatory efficacy of microglia mitochondrial energy metabolic reprogramming in PD. The research uncovers the biodistribution, metabolic variances, and therapeutic mechanism of chiral NPs, providing deep insights into the nanobiological effects of chiral anti-inflammatory nanomedicines in PD therapy for future clinical transformation.

Advances in the Treatment of Spinal Cord Injury with Nanozymes

Spinal cord injury (SCI) with increasing incidence can lead to severe disability. The pathological process involves complex mechanisms such as oxidative stress, inflammation, and neuron apoptosis. Current treatment strategies focusing on the relief of oxidative stress and inflammation have achieved good effects, while many problems and challenges remain such as the side effect and short half-life of the therapeutic agents. Nanozymes exhibiting good biocatalytic activities can sustainably scavenge free radicals, inhibit neuroinflammation, and protect the neurons. With high stability in physiological conditions and cost-effectiveness, the nanozymes provide a new strategy for SCI treatment. In this Review, we outline the advances of nanozymes and their enzyme-mimicking activities and highlight the progress in the intervention of SCI-adopting nanozymes. We also propose future directions and clinical translation for the nanozyme strategy against SCI.

Atomic Artificial Enzyme for Acute and Chronic Pneumonia

Pneumonia involves complex immunological and pathological processes leading to pulmonary dysfunction, which can be life-threatening yet lacks effective specialized medications. Natural enzymes can be used as biological agents for the treatment of oxidative stress-related diseases, but limiting to catalytic and environmental stability as well as high cost. Herein, an artificial enzyme, gold nanoclusters (Au NCs) with excellent stability, bioactivity, and renal clearance can be used as the next-generation biological agents for acute lung injury (ALI) and allergic lung disease (ALD). The Au25 clusters can mimic catalase (CAT) and glutathione peroxidase (GPx), and the Km of Au24Er1 with H2O2 reaches 1.28 mM, about 22 times higher than natural CAT (≈28.8 mM). The clusters inhibit the oxidative stress in the mitochondria and promote the synthesis of adenosine triphosphate (ATP). The molecular mechanism shows that the TLR4/MyD88/NF-κB pathway and M1 macrophage-mediated inflammatory response are suppressed in ALI and the Th1/Th2 imbalance in ovalbumin (OVA)-induced ALD is rescued. Further, the clusters can notably improve lung function in both ALI and ALD models which paves the way for immunomodulation and intervention for lung injury and can be used as a substitute for natural enzymes and potential biopharmaceuticals in the treatment of various types of pneumonia.

Advances in Tracing Techniques: Mapping the Trajectory of Mesenchymal Stem-Cell-Derived Extracellular Vesicles

Mesenchymal stem-cell-derived extracellular vesicles (MSC-EVs) are nanoscale lipid bilayer vesicles secreted by mesenchymal stem cells. They inherit the parent cell's attributes, facilitating tissue repair and regeneration, promoting angiogenesis, and modulating the immune response, while offering advantages like reduced immunogenicity, straightforward administration, and enhanced stability for long-term storage. These characteristics elevate MSC-EVs as highly promising in cell-free therapy with notable clinical potential. It is critical to delve into their pharmacokinetics and thoroughly elucidate their intracellular and in vivo trajectories. A detailed summary and evaluation of existing tracing strategies are needed to establish standardized protocols. Here, we have summarized and anticipated the research progress of MSC-EVs in various biomedical imaging techniques, including fluorescence imaging, bioluminescence imaging, nuclear imaging (PET, SPECT), tomographic imaging (CT, MRI), and photoacoustic imaging. The challenges and prospects of MSC-EV tracing strategies, with particular emphasis on clinical translation, have been analyzed, with promising solutions proposed.

Luminescence Fingerprint of Intracellular NIR-II Gold Nanocluster Transformation: Implications for Sensing and Imaging

Gold nanoclusters emitting in the second biological window (NIR-II-AuNCs) have gained significant interest for their potential in deep-tissue bioimaging and biosensing applications due to the partial transparency and reduced autofluorescence of tissues in this spectral range. However, the limited understanding of how the biological environment affects their luminescent properties might hinder their use in bioimaging and biosensing. In this study, we investigated the emission properties of NIR-II-AuNCs when interacting and internalizing into live cells including macrophages, fibroblasts, and cancer cell lines, revealing substantial alterations in their luminescence. A systematic comparison between control and in vitro experiments concluded that the disruption of surface ligands is the main factor responsible for these alterations. NIR-II-AuNCs within cellular environments may also be influenced by other interactions, including aggregation or complexation with proteins. Furthermore, we also corroborated these spectroscopic modifications at the in vivo level, providing additional evidence of the environmental sensitivity of NIR-II-AuNCs. The results obtained in this study contribute to a deeper understanding of the luminescence mechanisms of NIR-II-AuNCs in biological environments in cells and in living tissues and are crucial for their optimization as reliable tools in biological environment for in vitro and in vivo imaging and diagnostics.

Ce12V6 Clusters with Multi-Enzymatic Activities for Sepsis Treatment

Artificial enzymes, especially nanozymes, have attracted wide attention due to their controlled catalytic activity, selectivity, and stability. The rising Cerium-based nanozymes exhibit unique SOD-like activity, and Vanadium-based nanozymes always hold excellent GPx-like activity. However, most inflammatory diseases involve polymerase biocatalytic processes that require multi-enzyme activities. The nanocomposite can fulfill multi-enzymatic activity simultaneously, but large nanoparticles (>10 nm) cannot be excreted rapidly, leading to biosafety challenges. Herein, atomically precise Ce12V6 clusters with a size of 2.19 nm are constructed. The Ce12V6 clusters show excellent glutathione peroxidase (GPx) -like activity with a significantly lower Michaelis-Menten constant (Km, 0.0125 mM versus 0.03 mM of natural counterpart) and good activities mimic superoxide dismutase (SOD) and peroxidase (POD). The Ce12V6 clusters exhibit the ability to scavenge the ROS including O2 ·- and H2O2 via the cascade reactions of multi-enzymatic activities. Further, the Ce12V6 clusters modulate the proinflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) and consequently rescue the multi-organ failure in the lipopolysaccharide (LPS)-induced sepsis mouse model. With excellent biocompatibility, the Ce12V6 clusters show promise in the treatment of sepsis.

Bioactive Decellularized Extracellular Matrix Platform Integrating Multifunctional Nanozymes and Cell-Laden Microgels for Acute Liver Failure Treatment

Mesenchymal stem cell (MSC) therapy has emerged as a promising alternative approach for treating acute liver failure (ALF) while confronting the shortage of low efficiency and poor engraftment within a hostile liver milieu. In this study, we establish a bioactive decellularized extracellular matrix (dECM) platform that incorporates dihydrolipoic acid (DHLA)-protected Pt nanoclusters doped with Cu (PtCu-DHLA) nanozymes and cell-laden microgels. The PtCu-DHLA nanozymes, selected for their versatility, function as antioxidant, anti-inflammatory, pro-proliferative, and pro-angiogenic agents, enhancing ALF alleviation and providing an optimal microenvironment for MSC transplantation. Additionally, a methacrylic anhydride (MA)-modified porcine liver-derived decellularized extracellular matrix (PLdECM) hydrogel (PLdECMMA) has been developed for the construction of microgels via microfluidic devices. Interferon γ (IFNγ) preconditioned MSCs encapsulated in PLdECMMA microgels exhibit enhanced immunomodulating activity and prolonged survival. PtCu-DHLA nanozymes and cell-laden microgels are codelivered by leveraging the PLdECM hydrogel for orthotopic transplantation. The transplanted dECM platform enables an efficient and successful rescue of CCl4-induced ALF by counteracting oxidative stress, suppressing inflammatory storms, and promoting cellular regeneration. Overall, this study highlights a synergistic and reinforced strategy that combines biomimetic nanozymes with MSC therapy, offering significant potential for ALF treatment and broader applications in regenerative medicine.

Synergistic Intramolecular Charge Transfer Promotes Au Nanoclusters with Enhanced NIR-II Photoluminescence

Gold nanoclusters (Au NCs) protected by molecular ligands represent a new class of second-generation near-infrared (NIR-II) luminescent materials that have been widely studied. However, the photoluminescence efficiencies of most NIR-II emitting Au NCs in aqueous solution are generally lower than 0.2%, and to fully exploit the advantages of AuNCs in the NIR-II region, improving their photoluminescence efficiency has become an urgent need. Considering the holistic nature of the core-shell structure of Au NCs, herein, we propose a synergistic intramolecular charge transfer (ICT) strategy to enhance the luminescence. The NIR-II fluorescence quantum yield of Au NCs was increased 6-fold to 5.59% by the synergistic effect of heteroatomic copper doping and ligand p-MBA deprotonation. Experimental characterization results show that the strong p-π conjugation between d10 metal and the deprotonated p-MBA enhances the charge transfer between the metal core and ligand. The synergistic ICT process strongly suppressed the nonradiative process, thereby enhancing the emission intensity. Our findings provide a facile method for understanding the integrity of the core-shell structure of Au NCs and regulating their photoluminescence properties.

Valence-engineering modulation of MoS2 clusters for enhancing biocatalytic activity

Earth-abundant MoS2 with the advantages of a stable structure, tunable bandgap, and easy shear has great potential for applications in the fields of catalysis, biomedicine, and so on. However, the biocatalytic activity of MoS2 remains little investigated and is insufficient for biomedical applications. In this work, we develop ultra-small and water-soluble MoS2 clusters with superior antioxidant activity and enzyme-like activity via valence-engineering modulation with Ce doping. Compared with pure, Re-, Tl-, and Nd-MoS2 clusters, Ce-MoS2 clusters exhibit about 1.7-fold enhanced antioxidant activity. Moreover, superoxide dismutase (SOD)-like activity of Ce-MoS2 clusters is about 30-fold higher than that of MoS2 clusters. In addition, the Ce-MoS2 clusters are evidenced to possess ultra-high clearance performance for reactive oxygen species and reactive nitrogen radicals (RONS), especially ˙OH and O2˙-. The comprehensive analyses of valence evolution and the energy level structure indicate that the enhanced biocatalytic activity is attributed to the synergistic effect of valence engineering of Mo4+/Mo6+ and energy-level engineering in MoS2 clusters via Ce doping. This work provides a universal approach to improve the biocatalytic activity of MoS2 clusters via valence engineering modulation, which exhibits great potential in the field of biomedical application, especially inflammatory diseases.

Merged Red and NIR Light Sources for Photobiomodulation Therapy in Diabetic Wound Healing

Photobiomodulation (PBM) is considered an effective and safe therapeutic modality in supporting the treatment of complications from a global pandemic-diabetes. In this study, PBM therapy is investigated to accelerate wound healing in diabetic mice (DM), under the combined biological effects of red light from a red organic light-emitting diode (ROLED) and near-infrared (NIR) light from an NIR conversion film (NCF) with dispersed CuInS2/ZnS quantum dots (QDs). The QD concentration and the NCF structure were optimized to maximize the optical properties and mechanical stability. A merged red/NIR device (MRND) was produced by integrating the optimized NCF and ROLED for PBM therapy. As a result of irradiating DM with MRND at a dose of 2 J/cm2, after 10 days, the wounds recovered three times faster than DM without MRND. Additionally, MRND light not only restored the epidermal thickness to normal but also significantly reduced the levels of pro-inflammatory cytokines. The experimental results show that the proposed PBM therapy has the potential to improve the quality of life of diabetic patients by helping them with rapid wound healing.

Ultrasmall metal nanoclusters as efficient luminescent probes for bioimaging

Ultrasmall metal nanoclusters (NCs, <2 nm) have emerged as a novel class of luminescent probes due to their atomically precise size and tailored physicochemical properties. The rapid advancements in the design and utilization of metal NC-based luminescent probes are facilitated by the atomic-level manipulation of metal NCs. This review article explores (i) the engineering of metal NCs' functions for bioimaging applications, and (ii) the diverse uses of metal NCs in bioimaging. We begin by presenting an overview of the engineering functions of metal NCs as luminescent probes for bioimaging applications, highlighting key strategies for enhancing NCs' luminescence, biocompatibility and targeting capabilities towards biological specimens. Our discussion then centers on the bioimaging applications of metal NCs in subcellular organelles, individual cells, tissues, and entire organs. Finally, we offer a perspective on the challenges and potential developments in the future use of metal NCs for bioimaging applications.

An Emerging Toolkit of Ho3+ Sensitized Lanthanide Nanocrystals with NIR-II Excitation and Emission for in Vivo Bioimaging

Optical imaging in the second near-infrared window (NIR-II, 1000-1700 nm) holds great promise for biomedical detection due to reduced tissue scattering and autofluorescence. However, the rational design of NIR-II probes with superior excitation wavelengths to balance the effects of tissue scattering and water absorption remains a great challenge. To address this issue, here we developed a series of Ho3+-sensitized lanthanide (Ln) nanocrystals (NaYF4: Ho, Ln@NaYF4) excited at 1143 nm, featuring tunable emissions ranging from 1000 to 2200 nm for in vivo bioimaging. Precise core-shell engineering (β-NaYF4: Ho@NaYF4: Ln@NaYF4 and β-NaYF4: Ho/Yb@NaYbF4@NaYbF4: Ln@NaYF4) further endows the Ho3+-sensitized system with the capability of energy migration within interfaces, enabling more abundant visible and NIR-II emissions that are unattainable in co-doped structures due to detrimental cross relaxation. Tissue phantom studies demonstrated the superior tissue penetration ability of 1143 photons, especially in imaging experiments through the highly photon-scattering skull, where the fluorescence transmittance of 1143 nm excited nanocrystals was 15% and 10% higher than that of the conventional 808 and 980 excitation, respectively. By leveraging these Ho3+-sensitized nanomaterials with multiemission characteristics and well-selected lanthanide nanomaterials with crosstalk-free excitation, we achieved six-channel NIR-II in vivo imaging, enabling the simultaneous visualization of blood vessels, liver, spleen, stomach, intestine, subcutaneous tumors, and lymph nodes in mice. Our research provides new insights into the design of lanthanide nanocrystals with NIR-II excitation and emission and highlights the potential of these materials in in vivo multichannel detection.

Electrostatic Assembly of Gold Nanoclusters in Reverse Emulsion Enabling Nanoassemblies with Tunable Structure and Size for Enhanced NIR-II Fluorescence Imaging

The precise control of the assembly structure and size of gold nanoclusters (AuNCs) can potentially amplify their near-infrared II (NIR-II) fluorescence imaging and targeting properties. However, the conventional electrostatic assembly of AuNCs and charged molecules faces challenges in balancing the inherent electrostatic repulsions among charged units and regulating the diffusion of assembly units. These difficulties limit precise control over assembly size and structure, along with limited options for coassembled molecules, thereby restricting imaging properties and targeting capability. To circumvent this challenge, we developed a reverse emulsion-confined electrostatic assembly method. This technique efficiently constructs AuNC nanoassemblies with diverse coassembled molecules, allowing for the fine-tuning of assembly size and structure, including both core-satellite and homogeneous AuNC nanoassemblies. The development of two distinct nanoassemblies can be partially attributed to the varying diffusive rates of AuNCs or the AuNCs/polymer complex within the fused emulsion droplets. This variance arises from steric hindrances encountered during the emulsion fusion process. Interestingly, core-satellite nanoassemblies exhibit the strongest NIR-II fluorescence enhancement. Finally, the introduction of a hyaluronic acid coating on the surfaces of nanoassemblies with varying sizes enables the nanoprobes to achieve enhanced lymph node imaging through size modulation and macrophage targeting, which are used for surgical navigation to remove lymph node metastases. We envision that this self-assembly strategy can be extended to a wide range of electrostatic assembly systems for the development of multicomponent functional materials.

Recent advances of photoresponsive nanomaterials for diagnosis and treatment of acute kidney injury

Non-invasive imaging in the near-infrared region (NIR) offers enhanced tissue penetration, reduced spontaneous fluorescence of biological tissues, and improved signal-to-noise ratio (SNR), rendering it more suitable for in vivo deep tissue imaging. In recent years, a plethora of NIR photoresponsive materials have been employed for disease diagnosis, particularly acute kidney injury (AKI). These encompass inorganic nonmetallic materials such as carbon (C), silicon (Si), phosphorus (P), and upconversion nanoparticles (UCNPs); precious metal nanoparticles like gold and silver; as well as small molecule and organic semiconductor polymer nanoparticles with near infrared responsiveness. These materials enable effective therapy triggered by NIR light and serve as valuable tools for monitoring AKI in living systems. The review provides a concise overview of the current state and pathological characteristics of AKI, followed by an exploration of the application of nanomaterials and photoresponsive nanomaterials in AKI. Finally, it presents the design challenges and prospects associated with NIR photoresponsive materials in AKI.

Application of gold nanoclusters in fluorescence sensing and biological detection

Gold nanoclusters (Au NCs) exhibit broad fluorescent spectra from visible to near-infrared regions and good enzyme-mimicking catalytic activities. Combined with excellent stability and exceptional biocompatibility, the Au NCs have been widely exploited in biomedicine such as biocatalysis and bioimaging. Especially, the long fluorescence lifetime and large Stokes shift attribute Au NCs to good probes for fluorescence sensing and biological detection. In this review, we systematically summarized the molecular structure and fluorescence properties of Au NCs and highlighted the advances in fluorescence sensing and biological detection. The Au NCs display high sensitivity and specificity in detecting iodine ions, metal ions, and reactive oxygen species, as well as certain diseases based on the fluorescence activities of Au NCs. We also proposed several points to improve the practicability and accelerate the clinical translation of the Au NCs.

Constructing Electron-Rich Ru Clusters on Non-Stoichiometric Copper Hydroxide for Superior Biocatalytic ROS Scavenging to Treat Inflammatory Spinal Cord Injury

Traumatic spinal cord injury (SCI) represents a complex neuropathological challenge that significantly impacts the well-being of affected individuals. The quest for efficacious antioxidant and anti-inflammatory therapies is both a compelling necessity and a formidable challenge. Here, in this work, the innovative synthesis of electron-rich Ru clusters on non-stoichiometric copper hydroxide that contain oxygen vacancy defects (Ru/def-Cu(OH)2), which can function as a biocatalytic reactive oxygen species (ROS) scavenger for efficiently suppressing the inflammatory cascade reactions and modulating the endogenous microenvironments in SCI, is introduced. The studies reveal that the unique oxygen vacancies promote electron redistribution and amplify electron accumulation at Ru clusters, thus enhancing the catalytic activity of Ru/def-Cu(OH)2 in multielectron reactions involving oxygen-containing intermediates. These advancements endow the Ru/def-Cu(OH)2 with the capacity to mitigate ROS-mediated neuronal death and to foster a reparative microenvironment by dampening inflammatory macrophage responses, meanwhile concurrently stimulating the activity of neural stem cells, anti-inflammatory macrophages, and oligodendrocytes. Consequently, this results in a robust reparative effect on traumatic SCI. It is posited that the synthesized Ru/def-Cu(OH)2 exhibits unprecedented biocatalytic properties, offering a promising strategy to develop ROS-scavenging and anti-inflammatory materials for the management of traumatic SCI and a spectrum of other diseases associated with oxidative stress.

Luminescent metal nanoclusters and their application in bioimaging

Owing to their unique optical properties and atomically precise structures, metal nanoclusters (MNCs) constitute a new generation of optical probe materials. This mini-review provides a brief overview of luminescence mechanisms and modulation methods of luminescent metal nanoclusters in recent years. Based on these photophysical phenomena, the applications of cluster-based optical probes in optical bioimaging and related sensing, disease diagnosis, and treatment are summarized. Some challenges are also listed at the end.

Morphology-Mediated Tumor Deep Penetration for Enhanced Near Infrared II Photothermal and Chemotherapy of Colorectal Cancer

The low permeability and heterogeneous distribution of drugs (including nanomedicines) have limited their deep penetration into solid tumors. Herein we report the design of gold nanoparticles with virus-like spikes (AuNVs) to mimic viral shapes and facilitate tumor penetration. Mechanistic studies revealed that AuNVs mainly entered cells through macropinocytosis, then transported to the Golgi/endoplasmic reticulum system via Rab11-regulated pathway, and finally exocytosed through recycling endosomes, leading to high cellular uptake, effective transcytosis, and deep tumor penetration compared to gold nanospheres (AuNPs) and gold nanostars (AuNSs). The high tumor accumulation and deep tumor penetration of mitoxantrone (MTO) facilitated by AuNVs endowed effective chemophotothermal therapy when exposed to a near-infrared II laser, significantly reducing tumor sizes in a mouse model of colorectal cancer. This study reveals a potent mechanism of viral-like structures in tissue penetration and highlights their potential as effective drug delivery carriers.

Clinical Grade Fibroin Sutures with Bioactive Gold Clusters Enhance Surgical Wound Healing via Inflammation Modulation

Silk sutures are common in surgeries, and silk-based textiles are widely used in clinical medicine on account of their great mechanical properties and biodegradability. However, due to the lack of biocatalytic activity, silk sutures show unsatisfactory anti-inflammatory properties and healing speed. To address this constraint, we construct clinical grade bioactive gold cluster-sutures through a heterojunction. The antioxidant activity of bioactive gold cluster-sutures is ∼160 times more than that of clinical sutures. Meanwhile, the suture displays superb reactive oxygen species (ROS) scavenging, superoxide dismutase-like (SOD-like, 5 times more than the silk suture), and catalase-like (CAT-like) activities. The clusters assemble on the surface of silk through hydrogen bonding, leading to a durable catalytic and structural stability for 15 months without decay. Subsequently, the suture significantly accelerates wound healing by exerting excellent anti-inflammatory effects, improving neovascularization and collagen deposition. Clinical grade bioactive gold clusters with high bioactivity, stability, and biocompatibility hold promise for clinical translation and pave the way for other implanted biomaterials from wound healing to intelligent textiles.

Hepatic Biotransformation of Renal Clearable Gold Nanoparticles for Noninvasive Detection of Liver Glutathione Level via Urinalysis

Renal clearable nanoparticles have been drawing much attention as they can avoid prolonged accumulation in the body by efficiently clearing through the kidneys. While much effort has been made to understand their interactions within the kidneys, it remains unclear whether their transport could be influenced by other organs, such as the liver, which plays a crucial role in metabolizing and eliminating both endogenous and exogenous substances through various biotransformation processes. Here, by utilizing renal clearable IRDye800CW conjugated gold nanocluster (800CW4-GS18-Au25) as a model, we found that although 800CW4-GS18-Au25 strongly resisted serum-protein binding and exhibited minimal accumulation in the liver, its surface was still gradually modified by hepatic glutathione-mediated biotransformation when passing through the liver, resulting in the dissociation of IRDye800CW from Au25 and biotransformation-generated fingerprint message of 800CW4-GS18-Au25 in urine, which allowed us to facilely quantify its urinary biotransformation index (UBI) via urine chromatography analysis. Moreover, we observed the linear correlation between UBI and hepatic glutathione concentration, offering us a noninvasive method for quantitative detection of liver glutathione level through a simple urine test. Our discoveries would broaden the fundamental understanding of in vivo transport of nanoparticles and advance the development of urinary probes for noninvasive biodetection.

Metal-organic frameworks for biomedical applications: A review

Metal-organic frameworks (MOFs) are emergent materials in diverse prospective biomedical uses, owing to their inherent features such as adjustable pore dimension and volume, well-defined active sites, high surface area, and hybrid structures. The multifunctionality and unique chemical and biological characteristics of MOFs allow them as ideal platforms for sensing numerous emergent biomolecules with real-time monitoring towards the point-of-care applications. This review objects to deliver key insights on the topical developments of MOFs for biomedical applications. The rational design, preparation of stable MOF architectures, chemical and biological properties, biocompatibility, enzyme-mimicking materials, fabrication of biosensor platforms, and the exploration in diagnostic and therapeutic systems are compiled. The state-of-the-art, major challenges, and the imminent perspectives to improve the progressions convoluted outside the proof-of-concept, especially for biosensor platforms, imaging, and photodynamic therapy in biomedical research are also described. The present review may excite the interdisciplinary studies at the juncture of MOFs and biomedicine.

Interplay of kernel shape and surface structure for NIR luminescence in atomically precise gold nanorods

It is challenging to attain strong near-infrared (NIR) emissive gold nanoclusters. Here we show a rod-shaped cluster with the composition of [Au28(p-MBT)14(Hdppa)3](SO3CF3)2 (1 for short, Hdppa is N,N-bis(diphenylphosphino)amine, p-MBT is 4-methylbenzenethiolate) has been synthesized. Single crystal X-ray structural analysis reveals that it has a rod-like face-centered cubic (fcc) Au22 kernel built from two interpenetrating bicapped cuboctahedral Au15 units. 1 features NIR luminescence with an emission maximum at 920 nm, and the photoluminescence quantum yield (PLQY) is 12%, which is 30-fold of [Au21(m-MBT)12(Hdppa)2]SO3CF3 (2, m-MBT is 3-methylbenzenethiolate) with a similar composition and 60-fold of Au30S(S‑t‑Bu)18 with a similar structure. time-dependent DFT(TDDFT)calculations reveal that the luminescence of 1 is associated with the Au22 kernel. The small Stokes shift of 1 indicates that it has a very small excited state structural distortion, leading to high radiative decay rate (kr) probability. The emission of cluster 1 is a mixture of phosphorescence and thermally activated delayed fluorescence(TADF), and the enhancement of the NIR emission is mainly due to the promotion of kr rather than the inhibition of knr. This work demonstrates that the metal kernel and the surface structure are both very important for cluster-based NIR luminescence materials.

Three-Dimensional Visualization of Breast Cancer Pathology Evolution in Clinical Patient Tissues with NIR-II Imaging

Breast cancer (BC) is the most common tumor worldwide and requires crucial molecular typing for treatment and prognosis assessment. Currently, approaches like pathological staining, immunohistochemistry (IHC), and immunofluorescence (IF) face limitations due to the low signal-to-background ratio (SBR) and high tumor heterogeneity, resulting in a high misdiagnosis rate. Fluorescent assay in the second near-infrared region (NIR-II, 1000-1700 nm) exhibits ultrahigh SBR owing to diminished scattering and tissue autofluorescence. Here, we present a NIR-II strategy for accurate BC molecular typing and three-dimensional (3D) visualization based on the atomically precise fluorescent Au24Pr1 clusters. Single-atom Pr doping results in 3.9-fold fluorescence enhancement and long-term photostability. The Au24Pr1 clusters possess high fluorescence centered at ∼1100 nm and the SBR on pathological section diagnosis was 4 times higher than that of NIR-I imaging. This enables high spatial resolution 3D visualization of biopsy specimens, which can surmount tissue heterogeneity for clinical diagnosis of BC.

Ultra-low-cost and high-fidelity NIR-II confocal laser scanning microscope with Bessel beam excitation and SiPM detection

Confocal laser scanning microscopy (CLSM) is one of the most important imaging tools in the biomedical field, and near-infrared-II (NIR-II, 900-1700nm) fluorescence imaging technology has also made fruitful research progress in deep imaging in recent years. The NIR-II based CLSM has problems such as an expensive detector and reduced image resolution caused by long wavelength excitation. Here, by simultaneously using a low-cost silicon photomultiplier (SiPM) as a detector and a Bessel beam as an excitation, we developed an ultra-low-cost and high-fidelity NIR-II confocal laser scanning microscope. The use of SiPM reduces the cost of the NIR-II fluorescence detection module in CLSM, while enabling the detection of ultra-broadband fluorescence signals spanning visible to NIR-II regions. The introduction of the Bessel beam compensates to some extent for the weakening of spatial resolution caused by the increase in the wavelength of light in the NIR region. Experimental results show that the use of the Bessel beam can improve the resolution by 12% when observing thin samples. With the increase of sample thickness, the imaging resolution of the Bessel beam at NIR-II wavelengths is better than that of the Gaussian beam at NIR-I wavelengths at the penetrable depth of the NIR-I light. At deeper depths, the imaging resolution and imaging depth of Bessel beam CLSM is superior to Gaussian beam CLSM at the same excitation power.

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.

Recent Advances in Photosensitizer Materials for Light-Mediated Tumor Therapy

Photodynamic therapy (PDT) as an emerging therapeutic method has drawn much attention in the treatment field for cancer. Photosensitizer, which can convert photon energy into cytotoxic species under light irradiation, is the core component in PDT. The design of photosensitizers still faces problems of light absorption, targeting, penetration and oxygen dependence. With the rapid progress of material science, various photosensitizers have been developed to produce cytotoxic species for treatment of tumor with high selectivity, safety, and noninvasiveness. Besides, the applications of photosensitizers have been expanded to diverse cancer treatments such as drug release, optogenetics and immune checkpoint blockade. In this review, we summarize the recent advances of photosensitizers in various therapeutic methods for cancer. Prevailing challenges and further prospects associated with photosensitizers are also discussed.

Probiotics Armed with In Situ Mineralized Nanocatalysts and Targeted Biocoatings for Multipronged Treatment of Inflammatory Bowel Disease

While oral probiotics show promise in treating inflammatory bowel disease, the primary challenge lies in sustaining their activity and retention within the inflamed gastrointestinal environment. In this work, we develop an engineered probiotic platform that is armed with biocatalytic and inflamed colon-targeting nanocoatings for multipronged management of IBD. Notably, we achieve the in situ growth of artificial nanocatalysts on probiotics through a bioinspired mineralization strategy. The resulting ferrihydrite nanostructures anchored on bacteria exhibit robust catalase-like activity across a broad pH range, effectively scavenging ROS to alleviate inflammation. The further envelopment with fucoidan-based shields confers probiotics with additional inflamed colon-targeting functions. Upon oral administration, the engineered probiotics display markedly improved viability and colonization within the inflamed intestine, and they further elicit boosted prophylactic and therapeutic efficacy against colitis through the synergistic interplay of nanocatalysis-based immunomodulation and probiotics-mediated microbiota reshaping. The robust and multifunctional probiotic platforms offer great potential for the comprehensive management of gastrointestinal disorders.

Enzyme-mimic catalytic activities and biomedical applications of noble metal nanoclusters

Noble metal (e.g., Au and Ag) nanoclusters (NCs), which exhibit structural complexity and hierarchy comparable to those of natural proteins, have been increasingly pursued in artificial enzyme research. The protein-like structure of metal NCs not only ensures enzyme-mimic catalytic activity, including peroxidase-, catalase-, and superoxide dismutase-mimic activities, but also affords an unprecedented opportunity to correlate the catalytic performance with the cluster structure at the molecular or atomic levels. In this review, we aim to summarize the recent progress in programming and demystify the enzyme-mimic catalytic activity of metal NCs, presenting the state-of-the-art understandings of the structure-property relationship of metal NC-based artificial enzymes. By leveraging on a concise anatomy of the hierarchical structure of noble metal NCs, we manage to unravel the structural origin of the catalytic performance of metal NCs. Noteworthily, it has been proven that the surface ligands and metal-ligand interface of metal NCs are instrumental in influencing enzyme-mimic catalytic activities. In addition to the structure-property correlation, we also discuss the synthetic methodologies feasible to tailoring the cluster structure at the atomic level. Prior to the closure of this review with our perspectives in noble metal NC-based artificial enzymes, we also exemplify the biomedical applications based on the enzyme-mimic catalysis of metal NCs with the theranostics of kidney injury, brain inflammation, and tumors. The fundamental and methodological advancements delineated in this review would be conducive to further development of metal NCs as an alternative family of artificial enzymes.

A Macrophage Membrane-Coated Cu-WO3-x-Hydro820 Nanoreactor for Treatment and Photoacoustic/Fluorescence Dual-Mode Imaging of Inflamed Liver Tissue

A disease-targeting nanoplatform that integrates imaging with therapeutic activity would facilitate early diagnosis, treatment, and therapeutic monitoring. To this end, a macrophage membrane-coated Cu-WO3-x-Hydro820 (CWHM) nanoreactor was prepared. This reactor was shown to target inflammatory tissues. The reactive oxygen species (ROS) such as H2O2 and ·OH in inflammatory tissues can react with Hydro820 in the reactor to form the NIR fluorophore IR820. This process allowed photoacoustic/fluorescence dual-mode imaging of H2O2 and ·OH, and it is expected to permit visual diagnosis of inflammatory diseases. The Cu-WO3-x nanoparticles within the nanoreactor shown catalase and superoxide enzyme mimetic activity, allowing the nanoreactor to catalyze the decomposition of H2O2 and ·O2- in inflammatory cells of hepatic tissues in a mouse model of liver injury, thus alleviating the oxidative stress of damaged liver tissue. This nanoreactor illustrates a new strategy for the diagnosis and treatment of hepatitis and inflammatory liver injury.

In Vivo Toxicology of Metabolizable Atomically Precise Au25 Clusters at Ultrahigh Doses

Ultrasmall Au25(MPA)18 clusters show great potential in biocatalysts and bioimaging due to their well-defined, tunable structure and properties. Hence, in vivo pharmacokinetics and toxicity of Au nanoclusters (Au NCs) are very important for clinical translation, especially at high dosages. Herein, the in vivo hematological, tissue, and neurological effects following exposure to Au NCs (300 and 500 mg kg-1) were investigated, in which the concentration is 10 times higher than in therapeutic use. The biochemical and hematological parameters of the injected Au NCs were within normal limits, even at the ultrahigh level of 500 mg kg-1. Meanwhile, no histopathological changes were observed in the Au NC group, and immunofluorescence staining showed no obvious lesions in the major organs. Furthermore, real-time near-infrared-II (NIR-II) imaging showed that most of the Au25(MPA)18 and Au24Zn1(MPA)18 can be metabolized via the kidney. The results demonstrated that Au NCs exhibit good biosafety by evaluating the manifestation of toxic effects on major organs at ultrahigh doses, providing reliable data for their application in biomedicine.

Mated-Atom Nanozymes with Efficient Assisted NAD+ Replenishment for Skin Regeneration

Excessive accumulation of reduced nicotinamide adenine dinucleotide (NADH) within biological organisms is closely associated with many diseases. It remains a challenge to efficiently convert superfluous and detrimental NADH to NAD+. NADH oxidase (NOX) is a crucial oxidoreductase that catalyzes the oxidation of NADH to NAD+. Herein, M1M2 (Mi=V/Mn/Fe/Co/Cu/Mo/Rh/Ru/Pd, i = 1 or 2) mated-atom nanozymes (MANs) are designed by mimicking natural enzymes with polymetallic active centers. Excitingly, RhCo MAN possesses excellent and sustainable NOX-like activity, with Km-NADH (16.11 μM) being lower than that of NOX-mimics reported so far. Thus, RhCo MAN can significantly promote the regeneration of NAD+ and regulate macrophage polarization toward the M2 phenotype through down-regulation of TLR4 expression, which may help to recover skin regeneration. However, RhRu MAN with peroxidase-like activity and RhMn MAN with superoxide dismutase-like activity exhibit little modulating effects on eczema. This work provides a new strategy to inhibit skin inflammation and promote skin regeneration.

Visible to NIR-II Photoluminescence of Atomically Precise Gold Nanoclusters

Atomically precise gold nanoclusters (NCs) have emerged as a new class of precision materials and attracted wide interest in recent years. One of the unique properties of such nanoclusters pertains to their photoluminescence (PL), for it can widely span visible to near-infrared-I and -II wavelengths (NIR-I/II), and even beyond 1700 nm by manipulating the size, structure, and composition. The current research efforts focus on the structure-PL correlation and the development of strategies for raising the PL quantum yields, which is nontrivial when moving from the visible to the near-infrared wavelengths, especially in the NIR-II regions. This review summarizes the recent progress in the field, including i) the types of PL observed in gold NCs such as fluorescence, phosphorescence, and thermally activated delayed fluorescence, as well as dual emission; ii) some effective strategies that are devised to improve the PL quantum yield (QY) of gold NCs, such as heterometal doping, surface rigidification, and core phonon engineering, with double-digit QYs for the NIR PL on the horizons; and iii) the applications of luminescent gold NCs in bioimaging, photosensitization, and optoelectronics. Finally, the remaining challenges and opportunities for future research are highlighted.

Imaging-Guided Antibacterial Based on Gold Nanocrystals and Assemblies

Bacterial infection becomes a severe threat to human life and health worldwide. Antibiotics with the ability to resist pathogenic bacteria are therefore widely used, but the misuse or abuse of antibiotics can generate multidrug-resistant bacteria or resistant biofilms. Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria. With the excellent optical properties, engineerable surface chemistry, neglectable biotoxicity, gold nanocrystals are particularly attractive in biomedicine for cancer therapy and antibacterial therapy, as well as nanoprobes for bioimaging and disease diagnosis. In this perspective, gold nanocrystal-based antibacterial performance and deep-tissue imaging are summarized, including near-infrared-light excited photoacoustic imaging and fluorescence imaging through deep tissue infections. On the basis of integrating "imaging-therapy-targeting" in single nanotheranostic, the current challenges of imaging-guided antibacterial and therapy based on gold nanocrystals are discussed, and some insights are provided into the gold nanocrystal-based nanoplatform that integrates antibacterial activity and therapy. This perspective is expected to provide comprehensive guidance for diagnosing and combating bacterial infections based on gold nanostructures.

Biological Interaction and Imaging of Ultrasmall Gold Nanoparticles

The ultrasmall gold nanoparticles (AuNPs), serving as a bridge between small molecules and traditional inorganic nanoparticles, create significant opportunities to address many challenges in the health field. This review discusses the recent advances in the biological interactions and imaging of ultrasmall AuNPs. The challenges and the future development directions of the ultrasmall AuNPs are presented.