Selenium-doped two-photon fluorescent carbon nanodots for in-situ free radical scavenging in mitochondria

High-Resolution Tracking of Aging-Related Small Molecules: Bridging Pollutant Exposure, Brain Aging Mechanisms, and Detection Innovations

Brain aging is a complex process regulated by genetic, environmental, and metabolic factors, and increasing evidence suggests that environmental pollutants can significantly accelerate this process by interfering with oxidative stress, neuroinflammation, and mitochondrial function-related signaling pathways. Traditional studies have focused on the direct damage of pollutants on macromolecules (e.g., proteins, DNA), while the central role of senescence-associated small molecules (e.g., ROS, PGE2, lactate) in early regulatory mechanisms has been long neglected. In this study, we innovatively proposed a cascade framework of "small molecule metabolic imbalance-signaling pathway dysregulation-macromolecule collapse", which reveals that pollutants exacerbate the dynamics of brain aging through activation of NLRP3 inflammatory vesicles and inhibition of HIF-1α. Meanwhile, to address the technical bottleneck of small molecule spatiotemporal dynamics monitoring, this paper systematically reviews the cutting-edge detection tools such as electrochemical sensors, genetically encoded fluorescent probes and antioxidant quantum dots (AQDs). Among them, AQDs show unique advantages in real-time monitoring of ROS fluctuations and intervention of oxidative damage by virtue of their ultra-high specific surface area, controllable surface modification, and free radical scavenging ability. By integrating multimodal detection techniques and mechanism studies, this work provides a new perspective for analyzing pollutant-induced brain aging and lays a methodological foundation for early intervention strategies based on small molecule metabolic networks.

Robust Fluorescent Nanoprobe for Rapid Evaluation of the Selenium Supplementation Effect and Imaging

At present, an increasing number of people pay more attention to selenium-enriched food, but the quality of the selenium-enriched food varies. Therefore, there is an urgent need to develop a new tool to assess the effects of selenium supplementation in foods by rapidly detecting the levels of the metabolite selenium selenocysteine (Sec). In this work, a fluorescent nanoprobe CS-Sec was designed, synthesized, and characterized for Sec detection and imaging in living biosystems, which exhibited the advantages of good biocompatibility, excellent water solubility, high sensitivity, high selectivity, and rapid response (2.5 min) for Sec detection and imaging in vitro and in vivo and evaluation of selenium supplementation in selenium-rich foods. Specifically, CS-Sec was constructed by grafting alkyne groups on organic small-molecule fluorescent probes with azide groups on azido chitosan by click chemistry. A 2,4-dinitrophenyl ether (DNB) with a strong intramolecular charge transfer (ICT) effect was selected as a response group and fluorescence-quenching group, which had excellent chemical specificity toward Sec. In addition, CS-Sec has high selectivity and sensitivity toward Sec over other analytes, and an excellent limit of detection (LOD) is as low as 15 nM. Impressively, CS-Sec has been successfully used to detect and image the concentration of Sec in living HepG2 cells and mouse models with exciting results, indicating that the newly constructed CS-Sec can provide a robust molecule tool for the rapid evaluation of the selenium supplementation effect and imaging in the future.

Revitalizing Ancient Mitochondria with Nano-Strategies: Mitochondria-Remedying Nanodrugs Concentrate on Disease Control

Mitochondria, widely known as the energy factories of eukaryotic cells, have a myriad of vital functions across diverse cellular processes. Dysfunctions within mitochondria serve as catalysts for various diseases, prompting widespread cellular demise. Mounting research on remedying damaged mitochondria indicates that mitochondria constitute a valuable target for therapeutic intervention against diseases. But the less clinical practice and lower recovery rate imply the limitation of traditional drugs, which need a further breakthrough. Nanotechnology has approached favorable regiospecific biodistribution and high efficacy by capitalizing on excellent nanomaterials and targeting drug delivery. Mitochondria-remedying nanodrugs have achieved ideal therapeutic effects. This review elucidates the significance of mitochondria in various cells and organs, while also compiling mortality data for related diseases. Correspondingly, nanodrug-mediate therapeutic strategies and applicable mitochondria-remedying nanodrugs in disease are detailed, with a full understanding of the roles of mitochondria dysfunction and the advantages of nanodrugs. In addition, the future challenges and directions are widely discussed. In conclusion, this review provides comprehensive insights into the design and development of mitochondria-remedying nanodrugs, aiming to help scientists who desire to extend their research fields and engage in this interdisciplinary subject.

Rational design of a ratiometric fluorescent nanoprobe for real-time imaging of hydroxyl radical and its therapeutic evaluation of diabetes

Hydroxyl radical (•OH), one of the most reactive and deleterious substances in organisms, belongs to a class of reactive oxygen species (ROS), and it has been verified to play an essential role in numerous pathophysiological scenarios. However, due to its extremely high reactivity and short lifetime, the development of a reliable and robust method for tracking endogenous •OH remains an ongoing challenge. In this work, we presented the first ratiometric fluorescent nanoprobe NanoDCQ-3 for •OH sensing based on oxidative C-H abstraction of dihydroquinoline to quinoline. The study mainly focused on how to modulate the electronic effects to achieve an ideal ratiometric detection of •OH, as well as solving the inherent problem of hydrophilicity of the probe, so that it was more conducive to monitoring •OH in living organisms. The screened-out probe NanoDCQ-3 exhibited an exceptional ratiometric sensing capability, better biocompatibility, good cellular uptake, and appropriate in vivo retention, which has been reliably used for detecting exogenous •OH concentration fluctuation in living cells and zebrafish models. More importantly, NanoDCQ-3 facilitated visualization of •OH and evaluation of drug treatment efficacy in diabetic mice. These findings afforded a promising strategy for designing ratiometric fluorescent probes for •OH. NanoDCQ-3 emerged as a valuable tool for the detection of •OH in vivo and held potential for drug screening for inflammation-related diseases.

Roles of PTEN gene methylation in Se-CQDs induced mitochondrial apoptosis of osteosarcoma cells

Biocompatible carbon quantum dots (CQDs) containing anti-osteosarcoma elements are intriguing therapeutics promising for bioimaging and tumor therapy. However, how the anti-osteosarcoma element doped in the structure of such CQDs triggers tumor inhibition remains unclear. Here, selenium-doped CQDs (Se-CQDs) are developed via a one-step hydrothermal route using discarded orange peel as a carbon source and structurally characterized by various physicochemical techniques. The biocompatibility and anti-osteosarcoma efficacy are deeply evaluated using animal and cell models. The resulting spherical Se-CQDs, with a 3-7 nm diameter, possess green-yellow tunable luminescence and excellent biocompatibility. Cell experiments show that Se-CQDs can be up-taken by osteosarcoma U2OS cells and activate the mitochondrial apoptosis pathway triggered by increased reactive oxygen species. They can arrest the cell cycle at the G2/S phase and promote cellular apoptosis with reduced invasion and migration. Molecularly, Se-CQDs can down-regulate the expression of DNMT1 while up-regulating the expression of PTEN due to the decreased promoter methylation. Notably, Se-incorporated CQDs are more effective in inhibiting the proliferation, migration, and invasion of osteosarcoma than Se-free CQDs. It is feasible to use Se-CQDs as candidates for the potential application of early monitoring and treatment of osteosarcoma.

Regulating Chondro-Bone Metabolism for Treatment of Osteoarthritis via High-Permeability Micro/Nano Hydrogel Microspheres

Destruction of cartilage due to the abnormal remodeling of subchondral bone (SB) leads to osteoarthritis (OA), and restoring chondro-bone metabolic homeostasis is the key to the treatment of OA. However, traditional intra-articular injections for the treatment of OA cannot directly break through the cartilage barrier to reach SB. In this study, the hydrothermal method is used to synthesize ultra-small size (≈5 nm) selenium-doped carbon quantum dots (Se-CQDs, SC), which conjugated with triphenylphosphine (TPP) to create TPP-Se-CQDs (SCT). Further, SCT is dynamically complexed with hyaluronic acid modified with aldehyde and methacrylic anhydride (AHAMA) to construct highly permeable micro/nano hydrogel microspheres (SCT@AHAMA) for restoring chondro-bone metabolic homeostasis. In vitro experiments confirmed that the selenium atoms scavenged reactive oxygen species (ROS) from the mitochondria of mononuclear macrophages, inhibited osteoclast differentiation and function, and suppressed early chondrocyte apoptosis to maintain a balance between cartilage matrix synthesis and catabolism. In vivo experiments further demonstrated that the delivery system inhibited osteoclastogenesis and H-vessel invasion, thereby regulating the initiation and process of abnormal bone remodeling and inhibiting cartilage degeneration in SB. In conclusion, the micro/nano hydrogel microspheres based on ultra-small quantum dots facilitate the efficient penetration of articular SB and regulate chondro-bone metabolism for OA treatment.

The Preparation of Golgi Apparatus-Targeted Polymer Dots Encapsulated with Carbon Nanodots of Bright Near-Infrared Fluorescence for Long-Term Bioimaging

As a vital organelle in eukaryotic cells, the Golgi apparatus is responsible for processing and transporting proteins in cells. Precisely monitoring the status of the Golgi apparatus with targeted fluorescence imaging technology is of enormous importance but remains a dramatically challenging task. In this study, we demonstrate the construction of the first Golgi apparatus-targeted near-infrared (NIR) fluorescent nanoprobe, termed Golgi-Pdots. As a starting point of our investigation, hydrophobic carbon nanodots (CNDs) with bright NIR fluorescence at 674 nm (fluorescence quantum yield: 12.18%), a narrow emission band of 23 nm, and excellent stability were easily prepared from Magnolia Denudata flowers using an ultrasonic method. Incorporating the CNDs into a polymer matrix modified with Golgi-targeting molecules allowed for the production of the water-soluble Golgi-Pdots, which showed high colloidal stability and similar optical properties compared with pristine CNDs. Further studies revealed that the Golgi-Pdots showed good biocompatibility and Golgi apparatus-targeting capability. Based on these fascinating merits, utilizing Golgi-Pdots for the long-term tracking of the Golgi apparatus inside live cells was immensely successful.

Beneficial Effect of Selenium Doped Carbon Quantum Dots Supplementation on the in vitro Development Competence of Ovine Oocytes

Background

After the synthesis of selenium doped carbon quantum dots (Se/CDs) via a step-by-step hydrothermal synthesis method with diphenyl diselenide (DPDSe) as precursor, the beneficial effects of Se/CDs’ supplementation on the in vitro development competence of ovine oocytes were firstly investigated in this study by the assay of maturation rate, cortical granules’ (CGs) dynamics, mitochondrial activity, reactive oxygen species (ROS) production, epigenetic modification, transcript profile, and embryonic development competence.

Results

The results showed that the Se/CDs’ supplementation during the in vitro maturation (IVM) process not only enhanced the maturation rate, CGs’ dynamics, mitochondrial activity and embryonic developmental competence of ovine oocytes, but remarkably decreased the ROS production level of ovine oocytes. In addition, the expression levels of H3K9me3 and H3K27me3 in the ovine oocytes were significantly up-regulated after the Se/CDs’ supplementation, in consistent with the expression levels of 5mC and 5hmC. Moreover, 2994 up-regulated differentially expressed genes (DEGs) and 846 repressed DEGs were found in the oocytes after the Se/CDs’ supplementation. According to the analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), these DEGs induced by the Se/CDs’ supplementation were positively related to the progesterone mediated oocyte maturation and mitochondrial functions. And these remarkably up-regulated expression levels of DEGs related to oocyte maturation, mitochondrial function, and epigenetic modification induced by the Se/CDs’ supplementation further confirmed the beneficial effect of Se/CDs’ supplementation on the in vitro development competence of ovine oocytes.

Conclusion

The Se/CDs prepared in our study significantly promoted the in vitro development competence of ovine oocytes, benefiting the extended research about the potential applications of Se/CDs in mammalian breeding technologies.

Recent Progress of Surface Modified Nanomaterials for Scavenging Reactive Oxygen Species in Organism

Reactive oxygen species (ROS) are essential for normal physiological processes and play important roles in signal transduction, immunity, and tissue homeostasis. However, excess ROS may have a negative effect on the normal cells leading to various diseases. Nanomaterials are an attractive therapeutic alternative of antioxidants and possess an intrinsic ability to scavenge ROS. Surface modification for nanomaterials is a critical strategy to improve their comprehensive performances. Herein, we review the different surface modified strategies for nanomaterials to scavenge ROS and their inherent antioxidant capability, mechanisms of action, and biological applications. At last, the primary challenges and future perspectives in this emerging research frontier have also been highlighted. It is believed that this review paper will offer a top understanding and guidance on engineering future high-performance surface modified ROS scavenging nanomaterials for wide biomedical applications.

Lysosome-targetable selenium-doped carbon nanodots for in situ scavenging free radicals in living cells and mice

Lysosome-targetable selenium-doped carbon nanodots (Lyso-Se-CDs) that can efficiently scavenge lysosomal •OH in living cells and mice were designed in this research. Se-CDs with redox-responsive fluorescence (λ_ex = 379 nm, λ_em = 471 nm, quantum yield = 7.1%) were initially synthesized from selenocystine by a facile hydrothermal method, followed by the surface modification with morpholine, a lysosome targeting moiety. The as-synthesized Lyso-Se-CDs exhibited excellent colloidal stability, efficient scavenging abilities towards •OH, low biotoxicity, as well as good biocompatibility and lysosome targetability. Due to these desirable properties, Lyso-Se-CDs had been successfully utilized for rescuing cells from elevated lysosomal •OH levels. More importantly, Lyso-Se-CDs efficiently relieved phorbol 12-myristate 13-acetate (PMA) triggered ear inflammation in live mice. These findings reveal that Lyso-Se-CDs are potent candidates for treating •OH-related inflammation.

Superior reducing carbon dots from proanthocyanidin for free-radical scavenging and for cell imaging

The presence of excessive ROS can cause much harm to the human body and can even cause diseases. Therefore, it is important to detect and remove ROS, but there is no ideal method available for this at present. In this research, using procyanidins, a type of plant extract with strong reducibility, as raw materials, fluorescent carbon dots (CDs) were prepared by a hydrothermal method. The proanthocyanidin-based carbon dots (PCDs) emit a light-green colored light under UV irradiation. The PCDs retain the strong reducibility of procyanidins and are highly water-soluble compared with procyanidins. The PCDs, in addition to having good biocompatibility, also have the superior properties of radical scavenging activity and cell imaging. In in vitro experiments, 1,1-diphenyl-2-picrylhydrazyl (DPPH; 100 μM) was reduced by 30% when PCDs were added up to a concentration of 87.5 μg mL^-1. At the same time, the fluorescence quenching correlates with the concentration of hypochlorite and hydrogen peroxide and has a good linearity in the range of 250-2250 nM and 60-180 μM with a detection limit of 3.676 nM and 0.602 μM, respectively. Based on the previously described advantages, PCDs have potential as a biomedicine.

Discussions of Fluorescence in Selenium Chemistry: Recently Reported Probes, Particles, and a Clearer Biological Knowledge

In this review from literature appearing over about the past 5 years, we focus on selected selenide reports and related chemistry; we aimed for a digestible, relevant, review intended to be usefully interconnected within the realm of fluorescence and selenium chemistry. Tellurium is mentioned where relevant. Topics include selenium in physics and surfaces, nanoscience, sensing and fluorescence, quantum dots and nanoparticles, Au and oxide nanoparticles quantum dot based, coatings and catalyst poisons, thin film, and aspects of solar energy conversion. Chemosensing is covered, whether small molecule or nanoparticle based, relating to metal ion analytes, H2S, as well as analyte sulfane (biothiols-including glutathione). We cover recent reports of probing and fluorescence when they deal with redox biology aspects. Selenium in therapeutics, medicinal chemistry and skeleton cores is covered. Selenium serves as a constituent for some small molecule sensors and probes. Typically, the selenium is part of the reactive, or active site of the probe; in other cases, it is featured as the analyte, either as a reduced or oxidized form of selenium. Free radicals and ROS are also mentioned; aggregation strategies are treated in some places. Also, the relationship between reduced selenium and oxidized selenium is developed.

Label-free chlorine and nitrogen-doped fluorescent carbon dots for target imaging of lysosomes in living cells

Lysosomes with a single-layered membrane structure are mainly involved in the scavenging of foreign substances and play an important role in maintaining normal physiological functions of living cells. In this work, near-neutrally charged fluorescent carbon dots (CDs) were prepared with lipophilicity through a facile one-pot hydrothermal carbonization of chloranil and triethylenetetramine at 160 °C for 3 h. The as-obtained CDs are proved to have good photostability, low cost, and excellent biocompatibility. Importantly, the as-prepared CDs with high quantum yield of 30.8% show excitation-dependent emission with great stability, and thus, they can be well used for the long-term target imaging of lysosomes in living cells without further modification. Meanwhile, the CDs can quickly enter into the lysosomes within 30 min, and the green fluorescence (FL) of CDs reaches the plateau when incubated for 60 min. By comparing the fluorescent intensity, the information about distribution and amount of lysosomes in different cells can be obtained. The proposed CD-based strategy demonstrates great promise for label-free target imaging of lysosomes in living cells. Graphical abstract The near-neutral carbon dots (CDs) with lipophilicity are used as label-free fluorescent nanoprobes for the long-term imaging of lysosomes in living cells.