Carbon quantum Dot@Silver nanocomposite-based fluorescent imaging of intracellular superoxide anion

Advancements in Small Molecule Fluorescent Probes for Superoxide Anion Detection: A Review

Superoxide anion (O2•-), a significant reactive oxygen species (ROS) within biological systems, plays a widespread role in cellular function regulation and is closely linked to the onset and progression of numerous diseases. To unveil the pathological implications of O2•- in these diseases, the development of effective monitoring techniques within biological systems is imperative. Small molecule fluorescent probes have garnered considerable attention due to their advantages: simplicity in operation, heightened sensitivity, exceptional selectivity, and direct applicability in monitoring living cells, tissues, and animals. In the past few years, few reports have focused on small molecule fluorescence probes for the detection of O2•-. In this small review, we systematically summarize the design and application of O2•- responsive small molecule fluorescent probes. In addition, we present the limitations of the current detection of O2•- and suggest the construction of new fluorescent imaging probes to indicate O2•- in living cells and in vivo.

Effect of a new slow-release zinc fertilizer based on carbon dots on the zinc concentration, growth indices, and yield in wheat (Triticum aestivum)

The present study aimed to introduce a new carbon dots nanocarrier (Zn-NCDs) as a slow-release Zn fertilizer. Zn-NCDs was synthesized using a hydrothermal method and characterized by instrumental methods. A greenhouse experiment was then conducted involving two Zn sources (Zn-NCDs and ZnSO₄), three concentrations of Zn-NCDs (2, 4, and 8 mg/L), and under sand culture conditions. This study comprehensively evaluated the effects of Zn-NCDs on the zinc, nitrogen, and phytic acid content, biomass, growth indices, and yield in bread wheat (cv. Sirvan). Also, a fluorescence microscope was used to examine the in vivo transport route of Zn-NCDs in wheat organs. Finally, the availability of Zn in soil samples treated with Zn-NCDs was evaluated over 30 days in an incubation experiment. The findings indicated that Zn-NCDs as a slow-release fertilizer increased root-shoot biomass, fertile spikelet, and grain yield by 20, 44, 16, and 43%, respectively, compared to ZnSO₄ treatment. The concentration of zinc and nitrogen in the grain was increased by 19% and 118%, respectively, while phytic acid was decreased by 18% than ZnSO₄ treatment. Microscopic observations revealed that wheat plants could absorb and transfer Zn-NCDs from roots to stems and leaves through vascular bundles. This study demonstrated for the first time that Zn-NCDs could be used as a slow-release Zn fertilizer with high efficiency and low cost in wheat enrichment. In addition, Zn-NCDs could be applied as a new nano fertilizer and technology for in vivo plant imaging.

Advances in tumor nanotechnology: theragnostic implications in tumors via targeting regulated cell death

Cell death constitutes an indispensable part of the organismal balance in the human body. Generally, cell death includes regulated cell death (RCD) and accidental cell death (ACD), reflecting the intricately molecule-dependent process and the uncontrolled response, respectively. Furthermore, diverse RCD pathways correlate with multiple diseases, such as tumors and neurodegenerative diseases. Meanwhile, with the development of precision medicine, novel nano-based materials have gradually been applied in the clinical diagnosis and treatment of tumor patients. As the carrier, organic, inorganic, and biomimetic nanomaterials could facilitate the distribution, improve solubility and bioavailability, enhance biocompatibility and decrease the toxicity of drugs in the body, therefore, benefiting tumor patients with better survival outcomes and quality of life. In terms of the most studied cell death pathways, such as apoptosis, necroptosis, and pyroptosis, plenty of studies have explored specific types of nanomaterials targeting the molecules and signals in these pathways. However, no attempt was made to display diverse nanomaterials targeting different RCD pathways comprehensively. In this review, we elaborate on the potential mechanisms of RCD, including intrinsic and extrinsic apoptosis, necroptosis, ferroptosis, pyroptosis, autophagy-dependent cell death, and other cell death pathways together with corresponding nanomaterials. The thorough presentation of RCD pathways and diverse nano-based materials may provide a wider cellular and molecular landscape of tumor diagnosis and treatments.

Carbon dot and silver nanoparticle-based fluorescent probe for the determination of sulfite and bisulfite via inner-filter effect and competitive redox reactions

A new sensitive fluorescent probe (CDs-AgNP/H₂O₂) for detecting sulfite and bisulfite (SO₃^2- and HSO₃^-) based on the inner-filter effect (IFE) between silver nanoparticles (AgNPs) and carbon dots (CDs) was developed. Because of the spectral overlap between the absorption of AgNPs and the excitation of CDs, the fluorescence of CDs can be quenched by AgNPs owing to the IFE. H₂O₂ weakens the IFE and restores the fluorescence due to the oxidation of AgNPs by H₂O₂. However, the existence of SO₃^2-/HSO₃^- can quench the fluorescence again as a result of redox reaction between SO₃^2-/HSO₃^- and H₂O₂. The results showed a broad linear range of 20-200 μM with a low limit of detection (3.02 μM) toward SO₃^2-/HSO₃^-. The combination of IFE and redox reaction led to improvement of the sensitivity and selectivity. The probe was implemented to measure SO₃^2-/HSO₃^- in various agricultural products and foods with acceptable results (80.6 to 118.9% recovery).

Three-dimensional ordered DNA network constructed by a biomarker pair for accurate monitoring of colorectal cancer

Precise and early screening of colorectal cancer (CRC) is one crucial yet challenging task for its treatment, and the analysis of multi-targets of CRC in a single assay with high accuracy is essential for pathological research and clinical diagnosis. Here, a CRC-related biomarker pair, microRNA-211 (miRNA-211) and H₂S, was detected by constructing a three-dimensional (3D) ordered DNA network. First, trace amount of miRNA-211 could initiate a hybridization chain reaction-based amplification process. A highly ordered 3D DNA network was formed based on the organized assembly of DNA-cube frameworks that were constructed by DNA origamis and Ag nanoparticles (NPs) encapsulated inside. In the presence of the H₂S, Ag NPs within the network can be etched to generate Ag₂S quantum dots, which could be better visualized in fluorescence in situ cell imaging. Using the 3D DNA ordered network as the sensing platform, it can acquire dual analysis of biomolecule (miRNA-211) and inorganic gas (H₂S) in vitro, overcoming the limitations of single type of biomarker detection in a single assay. This assay achieved a wide linearity range of H₂S from 0.05 to 10 μM, and exhibited a low limit of detection of 4.78 nM. This strategy allows us to acquire the spatial distributions of H₂S and miRNA expression levels in living CRC cells simultaneously, providing a highly sensitive and selective tool for early screening and monitoring of CRC.

The role of molecular fluorophores in the photoluminescence of carbon dots derived from citric acid: current state-of-the-art and future perspectives

Carbon dots (CDs), an emerging class of nanomaterials, have attracted considerable attention due to their intriguing photophysical properties. Despite their indisputable potential of utilization in many fascinating areas of research and life, some fundamental aspects concerning their structure and the origin of their photoluminescence (PL) properties still await clarification. The mechanism of PL emission of CDs is associated with their structure, which is dependent on the carbonization process. At the initial stages of CD synthesis via a bottom-up approach, molecular fluorophores are considered to dominate the optical characteristics of the resulting nanomaterials. In this review, the recent progress in the use of molecular state theory for explanation of the structure-property relationship in CDs is summarized. This review focuses exclusively on the molecular fluorophores existing in nanomaterials prepared from citric acid (CA) as one of the most frequent carbon sources reported for the bottom-up synthesis of CDs. Consequently, the most relevant transformations of CA and the history of molecular fluorophores derived from it are described, followed by an in-depth discussion on their relevance in understanding the specific photophysical properties of blue-, green-, and red-emitting CDs. Finally, the challenging issues and future perspectives of molecular state PL mechanism exploration in CDs are highlighted.

ZIF-based carbon dots with lysosome-Golgi transport property as visualization platform for deep tumour therapy via hierarchical size/charge dual-transform and transcytosis

The poor penetration of nanomaterials in solid tumours and difficulty in monitoring their penetration depth are major obstacles in their application for the treatment of solid tumours. Herein, pH-responsive carbon dots (ZCD) based on a zeolitic imidazolate framework (ZIF-8) were fabricated to achieve the deep delivery of the chemotherapeutic doxorubicin (DOX) via a hierarchical size/charge dual-transformation and transcytosis. The as-prepared ZCD accumulated in the solid tumour and the acidic tumour microenvironment further triggered its decomposition. Firstly, ZCD was decomposed by the weakly acidic extracellular microenvironment of the solid tumour, enabling it to transform into small and neutrally charged particles. Subsequently, these particles were endocytosed by lysosomes, and further disintegrated into smaller and positively charged particles, which could target the Golgi apparatus. Consequently, ZCD delivered DOX deep into the solid tumour via a size-shrinking strategy and Golgi-mediated transcytosis, thus significantly improving its antitumour efficacy. In addition, carbonization endowed ZCD with superior fluorescence property, which was enhanced in the acidic microenvironment, thus improving the sensitivity and accuracy of ex vivo monitoring of the penetration depth of the nanomedicine in real time. Collectively, our results confirmed that the carbon dots obtained via the direct carbonization of ZIF-8 simultaneously exhibited enhanced deep penetration into solid tumours and fluorescence, which could be monitored, and that the carbonization of functional materials is effective to enhance their fluorescence, and further broaden their applications.

Nanotechnologies for Reactive Oxygen Species"Turn-On" Detection

Reactive oxygen species (ROS) encompasses a collection of complicated chemical entities characterized by individually specific biological reactivities and physicochemical properties. ROS detection is attracting tremendous attention. The reaction-based nanomaterials for ROS "turn-on" sensing represent novel and efficient tools for ROS detection. These nanomaterials have the advantages of high sensitivity, real-time sensing ability, and almost infinite contrast against background. This review focuses on appraising nanotechnologies with the ROS "turn-on" detection mechanism coupled with the ability for broad biological applications. In this review, we highlighted the weaknesses and advantages in prior sensor studies and raised some guidelines for the development of future nanoprobes.