A graphene oxide-based switch-on fluorescent probe for glutathione detection and cancer diagnosis

Fluorescent carbon dots for discriminating cell types: a review

Carbon dots (CDs) are quasi-spherical carbon nanoparticles with excellent photoluminescence, good biocompatibility, favorable photostability, and easily modifiable surfaces. CDs, serving as fluorescent probes, have emerged as an ideal tool for cellular differentiation owing to their outstanding luminescence performance and tunable surface properties. In this review, we summarize the recent research progress with CDs in the differentiation of cancer/normal cells, Gram-positive/Gram-negative bacteria, and live/dead cells, as well as the cellular differences used for differentiation. Additionally, we summarize the preparation methods, raw materials, and properties of the CDs used for cell discrimination. The differentiation mechanisms and the advantages or limitations of the differentiation methods are also introduced. Finally, we propose several research challenges in this field and future research directions that require extensive investigation. It is hoped that this review will help researchers in the design of new CDs as ideal fluorescent probes for realizing diverse cell differentiation applications.

Emerging Trends in Nanomedicine: Carbon-Based Nanomaterials for Healthcare

Carbon-based nanomaterials, such as carbon quantum dots (CQDs) and carbon 2D nanosheets (graphene, graphene oxide, and graphdiyne), have shown remarkable potential in various biological applications. CQDs offer tunable photoluminescence and excellent biocompatibility, making them suitable for bioimaging, drug delivery, biosensing, and photodynamic therapy. Additionally, CQDs' unique properties enable bioimaging-guided therapy and targeted imaging of biomolecules. On the other hand, carbon 2D nanosheets exhibit exceptional physicochemical attributes, with graphene excelling in biosensing and bioimaging, also in drug delivery and antimicrobial applications, and graphdiyne in tissue engineering. Their properties, such as tunable porosity and high surface area, contribute to controlled drug release and enhanced tissue regeneration. However, challenges, including long-term biocompatibility and large-scale synthesis, necessitate further research. Potential future directions encompass theranostics, immunomodulation, neural interfaces, bioelectronic medicine, and expanding bioimaging capabilities. In summary, both CQDs and carbon 2D nanosheets hold promise to revolutionize biomedical sciences, offering innovative solutions and improved therapies in diverse biological contexts. Addressing current challenges will unlock their full potential and can shape the future of medicine and biotechnology.

Ultrabright Green-Emissive Nanodots for Precise Biological Visualization

Developing general methods to fabricate water-dispersible and biocompatible fluorescent probes will promote different biological visualization applications. Herein, we report a metal-facilitated method to fabricate ultrabright green-emissive nanodots via the one-step solvothermal treatment of rose bengal, ethanol, and various metal ions. These metal-doped nanodots show good water dispersity, ultrahigh photoluminescence quantum yields (PLQYs) (e.g., the PLQY of Fe-doped nanodots (FeNDs) was ∼97%), and low phototoxicity. Owing to the coordination effect of metal ions, the FeNDs realize glutathione detection with outstanding properties. Benefiting from the high endoplasmic reticulum (ER) affinity of the chloride group, the FeNDs can act as an ER tracker with long ER imaging capacity (FeNDs: >24 h; commercial ER tracker: ∼1 h) and superb photostability and can achieve tissue visualization in living Caenorhabditis elegans. The metal-doped nanodots represent a general nanodot preparation method and may shed new light on diverse biological visualization uses.

Graphene Oxide Nanoparticles and Organoids: A Prospective Advanced Model for Pancreatic Cancer Research

Pancreatic cancer, notorious for its grim 10% five-year survival rate, poses significant clinical challenges, largely due to late-stage diagnosis and limited therapeutic options. This review delves into the generation of organoids, including those derived from resected tissues, biopsies, pluripotent stem cells, and adult stem cells, as well as the advancements in 3D printing. It explores the complexities of the tumor microenvironment, emphasizing culture media, the integration of non-neoplastic cells, and angiogenesis. Additionally, the review examines the multifaceted properties of graphene oxide (GO), such as its mechanical, thermal, electrical, chemical, and optical attributes, and their implications in cancer diagnostics and therapeutics. GO's unique properties facilitate its interaction with tumors, allowing targeted drug delivery and enhanced imaging for early detection and treatment. The integration of GO with 3D cultured organoid systems, particularly in pancreatic cancer research, is critically analyzed, highlighting current limitations and future potential. This innovative approach has the promise to transform personalized medicine, improve drug screening efficiency, and aid biomarker discovery in this aggressive disease. Through this review, we offer a balanced perspective on the advancements and future prospects in pancreatic cancer research, harnessing the potential of organoids and GO.

Graphene oxide nanoarchitectures in cancer therapy: Drug and gene delivery, phototherapy, immunotherapy, and vaccine development

The latest advancements in oncology involves the creation of multifunctional nanostructures. The integration of nanoparticles into the realm of cancer therapy has brought about a transformative shift, revolutionizing the approach to addressing existing challenges and limitations in tumor elimination. This is particularly crucial in combating the emergence of resistance, which has significantly undermined the effectiveness of treatments like chemotherapy and radiotherapy. GO stands as a carbon-derived nanoparticle that is increasingly finding utility across diverse domains, notably in the realm of biomedicine. The utilization of GO nanostructures holds promise in the arena of oncology, enabling precise transportation of drugs and genetic material to targeted sites. GO nanomaterials offer the opportunity to enhance the pharmacokinetic behavior and bioavailability of drugs, with documented instances of these nanocarriers elevating drug accumulation at the tumor location. The GO nanostructures encapsulate genes, shielding them from degradation and facilitating their uptake within cancer cells, thereby promoting efficient gene silencing. The capability of GO to facilitate phototherapy has led to notable advancements in reducing tumor progression. By PDT and PTT combination, GO nanomaterials hold the capacity to diminish tumorigenesis. GO nanomaterials have the potential to trigger both cellular and innate immunity, making them promising contenders for vaccine development. Additionally, types of GO nanoparticles that respond to specific stimuli have been applied in cancer eradication, as well as for the purpose of cancer detection and biomarker diagnosis. Endocytosis serves as the mechanism through which GO nanomaterials are internalized. Given these advantages, the utilization of GO nanomaterials for tumor elimination comes highly recommended.

Nanotechnology in Cancer Diagnosis and Treatment

Traditional cancer diagnosis has been aided by the application of nanoparticles (NPs), which have made the process easier and faster. NPs possess exceptional properties such as a larger surface area, higher volume proportion, and better targeting capabilities. Additionally, their low toxic effect on healthy cells enhances their bioavailability and t-half by allowing them to functionally penetrate the fenestration of epithelium and tissues. These particles have attracted attention in multidisciplinary areas, making them the most promising materials in many biomedical applications, especially in the treatment and diagnosis of various diseases. Today, many drugs are presented or coated with nanoparticles for the direct targeting of tumors or diseased organs without harming normal tissues/cells. Many types of nanoparticles, such as metallic, magnetic, polymeric, metal oxide, quantum dots, graphene, fullerene, liposomes, carbon nanotubes, and dendrimers, have potential applications in cancer treatment and diagnosis. In many studies, nanoparticles have been reported to show intrinsic anticancer activity due to their antioxidant action and cause an inhibitory effect on the growth of tumors. Moreover, nanoparticles can facilitate the controlled release of drugs and increase drug release efficiency with fewer side effects. Nanomaterials such as microbubbles are used as molecular imaging agents for ultrasound imaging. This review discusses the various types of nanoparticles that are commonly used in cancer diagnosis and treatment.

Construction of continuously enhanced fluorescent sensor for detection of glutathione in normal and cancer cells

In this paper, water-soluble cysteamine (CA)-capping CdSe quantum dots (CA-CdSe) could be used as a continuous fluorescent sensor. The CA-CdSe QDs can respond to Ag⁺ with a detection limit of 54.1 nM. Interestingly, CA-CdSe quantum dots combined with Ag⁺ to generate a new nano-fluorescence sensor-Ag⁺ modified CA-CdSe QDs (Ag⁺@CA-CdSe). Ag⁺@CA-CdSe can detect glutathione (GSH) with good sensitivity and anti-interference performance. The detection limit of Ag⁺@CA-CdSe fluorescenct sensor for GSH is as low as 0.74 μM. In addition, the novel nano-fluorescent sensor Ag⁺@CA-CdSe exhibited good cell permeability and was successfully applied to detect exogenous and endogenous GSH concentrations in cells. It could distinguish cancerous and normal cells by in vitro cell fluorescence imaging.

A novel colorimetric detection of glutathione based on stable free radical TEMPO oxidation of 3,3',5,5'-tetramethylbenzizine (TMB) via Copper(II) acetylacetonate catalysis

In this work, a new colorimetric method for the determination of Glutathione (GSH) on the basis of stable free radical 2,2,6,6 - tetramethylpiperidine - 1 - oxyl (TEMPO) oxidation of 3,3',5,5'-tetramethylbenzizine (TMB) via copper(II) acetylacetonate (Cu(acac)₂) catalysis was proposed. TEMPO was catalyzed by Cu(acac)₂ to produce TEMPO⁺, then TEMPO⁺ oxidized TMB to produce oxidized TMB (ox - TMB). The resulting ox - TMB showed blue and possessed a distinct absorption peak about 650 nm. Whereas, GSH prohibited the generation of ox - TMB through inhibiting TMB oxidation. As compared to the case that GSH was absent, significantly enhanced absorption was determined, and was proportional to GSH amount. On this basis, a qualitative and quantitative detection method of GSH with the naked eye and the microplate reader was achieved. The developed TEMPO - based method achieved GSH biosensing with improved sensitivity in a good specificity - manner. The limit of detection (LOD) was 90 μM via naked eye, and the microplate reader was 4.71 μM. And the stable free radical TEMPO possessed higher stability and lower toxicity than traditional oxidant of H₂O₂. Moreover, this TEMPO - based method achieved good results in the detection of GSH in human serums.

Fluorescent Sensing of Glutathione and Related Bio-Applications

Glutathione (GSH), as the most abundant low-molecular-weight biological thiol, plays significant roles in vivo. Abnormal GSH levels have been demonstrated to be related to the dysfunction of specific physiological activities and certain kinds of diseases. Therefore, the sensing of GSH is emerging as a critical issue. Cancer, with typical high morbidity and mortality, remains one of the most serious diseases to threaten public health. As it is clear that much more concentrated GSH is present at tumor sites than at normal sites, the in vivo sensing of GSH offers an option for the early diagnosis of cancer. Moreover, by monitoring the amounts of GSH in specific microenvironments, effective diagnosis of ROS levels, neurological diseases, or even stroke has been developed as well. In this review, we focus on the fluorescent methodologies for GSH detection, since they can be conveniently applied in living systems. First, the fluorescent sensing methods are introduced. Then, the principles for fluorescent sensing of GSH are discussed. In addition, the GSH-sensing-related biological applications are reviewed. Finally, the future opportunities in in the areas of fluorescent GSH sensing-in particular, fluorescent GSH-sensing-prompted disease diagnosis-are addressed.

Platinum-Coordinated Dual-Responsive Nanogels for Universal Drug Delivery and Combination Cancer Therapy

Developing a universal nanoplatform for efficient delivery of various drugs to target sites is urgent for overcoming various biological barriers and realizing combinational cancer treatment. Nanogels, with the advantages of both hydrogels and nanoparticles, may hold potential for addressing the above issue. Here, a dual-responsive nanogel platform (HPC nanogel) is constructed using β-cyclodextrin-conjugated hyaluronic acid (HA-βCD), polyethyleneimine (PEI), and cisplatin. HA-βCD and PEI compose the skeleton of the nanogel, and cisplatin molecules provide the junctions inside the skeleton, thus affording a multiple interactions-based nanogel. Besides, HA endows the nanogel with hyaluronidase (HAase)-responsiveness, and cisplatin guarantees the glutathione (GSH)-responsive ability, which make the nanogel a dual-responsive platform that can degrade and release the loaded drugs when encountering HAase or GSH. Additionally, the HPC nanogel possesses excellent small-molecule drug and protein loading and intracellular delivery capabilities. Especially, for proteins, their intracellular delivery via nanogels is not hindered by serum proteins, and the enzymes delivered into cells still maintain their catalytic activities. Furthermore, the nanogel can codeliver different cargoes to achieve "cocktail" chemotherapeutic efficacy and realize combination cancer therapy. Overall, the HPC nanogel can serve as a multifunctional platform capable of delivering desired drugs to treat cancer or other diseases.

Design Strategies of Tumor-Targeted Delivery Systems Based on 2D Nanomaterials

Conventional chemotherapy and radiotherapy are nonselective and nonspecific for cell killing, causing serious side effects and threatening the lives of patients. It is of great significance to develop more accurate tumor-targeting therapeutic strategies. Nanotechnology is in a leading position to provide new treatment options for cancer, and it has great potential for selective targeted therapy and controlled drug release. 2D nanomaterials (2D NMs) have broad application prospects in the field of tumor-targeted delivery systems due to their special structure-based functions and excellent optical, electrical, and thermal properties. This review emphasizes the design strategies of tumor-targeted delivery systems based on 2D NMs from three aspects: passive targeting, active targeting, and tumor-microenvironment targeting, in order to promote the rational application of 2D NMs in clinical practice.

H2O2/pH Dual-Responsive Biomimetic Nanoenzyme Drugs Delivery System for Enhanced Tumor Photodynamic Therapy

Phototherapy has been recognized as a photochemical process to treat tumor via induce cancer cells necrosis and death, with minimal invasiveness, higher selectivity, and few side effects. However, the therapy effects of phototherapy are often compromised by the hypoxia, high levels of hydrogen peroxide, and glutathione of tumor microenvironment (TME). Therefore, we constructed a catalase-like activity bionic metal-organic framework drugs delivery system (FA-EM@MnO₂/ZIF-8/ICG) with tumor microenvironment controllable releasing. In this system, photosensitizer indocyanine green (ICG) was introduced into zeolite imidazole salt skeleton 8 (ZIF-8) by one-step methods, forming ZIF-8/ICG nano-platform, which can effectively avoid ICG-induced phototoxicity and aggregation-induced quenching during transport. MnO₂ with catalase-like activity was coated on the surface of ZIF-8/ICG nano-platform, which made it have the ability of self-supplying O₂ under the condition of H₂O₂ in TME. Exposure under near-infrared light can alleviate the anoxic TME, thus improving the phototherapy efficiency. In addition, folate-functionalized erythrocyte membrane is coated on the surface of MnO₂/ZIF-8/ICG, which can endow FA-EM@MnO₂/ZIF-8/ICG with the ability of targeted drug administration and immune elimination avoidance. Therefore, FA-EM@MnO₂/ZIF-8/ICG nano-platform has the catalase-like activity, which can alleviate the oxidative stress state of TME and provide a beneficial environment for photodynamic therapy of tumor.

Applications of graphene-based electrochemical and optical biosensors in early detection of cancer biomarkers

Graphene is a one-atom-thick carbon compound, which holds promises for detecting cancer biomarkers along with its derivatives. The atom-wide graphene layer is ideal for cancer biomarker detection due to its unique physicochemical properties like increased electrical and thermal conductivity, optical transparency, and enhanced chemical and mechanical strength. The scientific aim of any biosensor is to create a smaller and portable point of care device for easy and early cancer detection; graphene is able to live up to that. Apart from tumour detection, graphene-based biosensors can diagnose many diseases, their biomarkers, and pathogens. Many existing remarkable pieces of research have proven the candidacy of nanoparticles in most cancer biomarkers detection. This article discusses the effectiveness of graphene-based biosensors in different cancer biomarker detection. This article provides a detailed review of graphene and its derivatives that can be used to detect cancer biomarkers with high specificity, sensitivity, and selectivity. We have highlighted the synthesis procedures of graphene and its products and also discussed their significant properties. Furthermore, we provided a detailed overview of the recent studies on cancer biomarker detection using graphene-based biosensors. The different paths to create and modify graphene surfaces for sensory applications have also been highlighted in each section. Finally, we concluded the review by discussing the existing challenges of these biosensors and also highlighted the steps that can be taken to overcome them.

Rose Bengal-Derived Ultrabright Sulfur-Doped Carbon Dots for Fast Discrimination between Live and Dead Cells

The discrimination between dead and live cells is crucial for cell viability evaluation. Carbon dots (CDs), with advantages like simple and cost-effective synthesis, excellent biocompatibility, and high photostability, have shown potential for realizing selective live/dead cell staining. However, most of the developed CDs with the live/dead cell discrimination capacity usually have low photoluminescence quantum yields (PLQYs) and excitation wavelength-dependent fluorescence emission (which can cause fluorescence overlap with other fluorescent probes and make dual-color live/dead staining impossible), and hence, developing ultrabright CDs with excitation wavelength-independent fluorescence emission property for live/dead cell discrimination becomes an important task. Here, using a one-pot hydrothermal method, we prepared ultrasmall (∼1.6 nm), ultrabright (PLQY: ∼78%), and excitation wavelength-independent sulfur-doped carbon dots (termed S-CDs) using rose bengal and 1,4-dimercaptobenzene as raw materials and demonstrated that the S-CDs could rapidly (∼5 min) and accurately distinguish dead cells from live ones for almost all the cell types including bacterial, fungal, and animal cells in a wash-free manner. We confirmed that the S-CDs could rapidly pass through the dead cell surfaces to enter the interior of the dead cells, thus visualizing these dead cells. In contrast, the S-CDs could not enter the interior of live cells and thus could not stain these live cells. We further verified that the S-CDs presented better biocompatibility and higher photostability than the commercial live/dead staining dye propidium iodide, ensuring its bright application prospect in cell imaging and cell viability assessment. Overall, this work develops a type of CDs capable of realizing the live/dead cell discrimination of almost all the cell types (bacterial, fungal, and animal cells), which has seldom been achieved by other fluorescent nanoprobes.

Biomimetic smart nanoplatform for dual imaging-guided synergistic cancer therapy

A biomimetic nanoplatform for MRI and fluorescence imaging-guided synergetic cancer therapies has been constructed using a folate-functionalized erythrocyte membrane-coated metal–organic framework as both a photosensitizer and a nanocarrier.

Naturally Occurring Exopolysaccharide Nanoparticles: Formation Process and Their Application in Glutathione Detection

Naturally occurring nanoscale exopolysaccharide (EPS) has attracted much attention in recent years. In this research, we obtained a new kind of naturally occurring spherical EPS nanoparticles (EPS-R503) from Lactobacillus plantarum R503. The secretion, self-assembly process, morphological structure, and surface characteristics of the as-prepared nanoparticles were comprehensively revealed with transmission electron microscopy (TEM) and atomic force microscope (AFM) for the first time. It was found that the EPS-R503 nanoparticles consist of negatively charged heteropolysaccharide composed of mannose, glucose, galactose, and glucuronide with several functional groups including -OH, -COOH, and -NH₂. When different solvents were used to treat the EPS-R503 nanoparticles, the morphological structure and surface properties could be changed or manipulated. The forming mechanism of EPS-R503 was elucidated based on the aggregation processes from a fundamental point of view. Furthermore, EPS-R503 can serve as reducing and stabilizing agents for the biosynthesis of manganese dioxide nanosheets (MnO₂ NSs), leading to EPS-MnO₂ nanocomposite. The as-prepared nanocomposites can absorb fluorescein (FL) to form EPS-MnO₂-FL, which can be used to detect glutathione (GSH) with a low limit of detection (0.16 μM) and a wide detection range from 0.05 to 4 mM. The excellent biocompatibility of EPS-MnO₂-FL endows the feasibility of in vivo detection of GSH as well. Overall, the findings from this work not only benefit the exploitation of naturally occurring EPS nanomaterials but also provide a novel strategy for the green synthesis of metal-containing nanosheets for GSH detection.

Biocompatibility nanoprobe of MXene N-Ti3C2 quantum dot/Fe3+ for detection and fluorescence imaging of glutathione in living cells

MXene quantum dots have attracted much attention due to their great optical performance and excellent water solubility. Glutathione (GSH) plays a key role in living cells. In this study, a biocompatibility nanoprobe was prepared for detecting intracellular GSH based on MXene N-Ti₃C₂ quantum dots (N-Ti₃C₂ QDs). The N-Ti₃C₂ QDs act as the fluorescence reporters and the ferric iron (Fe³⁺) as the quenchers based on nonradiative electron-hole annihilation. When Fe³⁺ encounters the amino group of N-Ti₃C₂ QDs, the electrons of N-Ti₃C₂ QDs in the excited state will transfer to the half-filled 3d orbitals of Fe³⁺, leading to the fluorescence quenching of N-Ti₃C₂ QDs. When the N-Ti₃C₂ QDs/Fe³⁺ nanoprobe acts on the cancer cell MCF-7, the abundant GSH in the cancer cells can reduce Fe³⁺ to Fe²⁺, which will restore the fluorescence of N-Ti₃C₂ QDs. The N-Ti₃C₂ QDs/Fe³⁺ nanoprobe displays a high sensitivity for GSH with a detection limit of 0.17 μM in range of 0.5-100 μM. It becomes a promising probe for detecting and showing cellular imaging of GSH in MCF-7 cells. The N-Ti₃C₂ QDs/Fe³⁺ nanoprobe might provide a new way for imaging-guided precision cancer diagnosis.

Fabrication of FeS2/SiO2 Double Mesoporous Hollow Spheres as an Artificial Peroxidase and Rapid Determination of H2O2 and Glutathione

Nanozymes as one of artificial enzymes show many advantages than natural enzymes. The high Michaelis-Menten constant (K_m) to H₂O₂ is the drawback for nanozymes, which means a high H₂O₂ concentration to oxidize 3,3',5,5'-tetramethylbenzidine (TMB). For this problem, FeS₂/SiO₂ double mesoporous hollow spheres (DMHSs) were first synthesized as an artificial peroxidase through a solid reaction. The experimental results demonstrate that Fe₃O₄ vulcanization and DMHS formation were effective strategies to enhance affinity to H₂O₂ for the nanozyme. The K_m of FeS₂/SiO₂ DMHSs (H₂O₂ as the substrate) is 18-fold smaller than that of FeS₂ nanoparticles (NPs). The catalytic efficiency (K_cat/K_m) of FeS₂/SiO₂ DMHSs is about 16 times higher than that of FeS₂ NPs. FeS₂/SiO₂ DMHSs can be used as a nanozyme to sensitively and rapidly detect H₂O₂ and glutathione within 1 min at room temperature.

A facile biosensor for Aβ40O based on fluorescence quenching of prussian blue nanoparticles

Amyloid β peptide oligomeFrs (AβOs) have been proved to be crucial biomarkers of Alzheimer's disease (AD). To explore an applicable method for the determination of AβOs is significant for the early AD diagnosis. Prussian blue nanoparticles (PBNPs), as one excellent nanomaterials, have the advantages of good stability, favorable biocompatibility, low cost, easy preparation and controllable shape. PBNPs was found to be of the fluorescence quenching ability to fluorophores, and the adsorption of DNA onto PBNPs surface occurred via the binding of phosphate skeleton in DNA to Fe²⁺/Fe³⁺ in PBNPs. On basis of this, carboxyl fluorescein (FAM) modified Aβ₄₀O-targeting aptamer (FAM-Apt_Aβ) was adsorbed onto PBNPs. And FAM-Apt_Aβ@PBNPs-based fluorescent aptasensor for the determination of Aβ₄₀O was developed. Upon incubating FAM-Apt_Aβ@PBNPs with Aβ₄₀O, the fluorescence intensity of the FAM-Apt_Aβ@PBNPs obviously increased comparing to the initial fluorescence intensity of the FAM-Apt_Aβ@PBNPs. The changes in the fluorescence intensity of the FAM-Apt_Aβ@PBNPs were linear with the Aβ₄₀O concentrations ranging from 1.00 nM to 100 nM. Moreover, AD patients and healthy persons can be distinguished using this method to determine Aβ₄₀O concentrations in human cerebrospinal fluid samples from AD patients and healthy persons. It demonstrates that this PBNPs-based aptasensor is not only simple and cost-effective, but also sensitive, selective and more applicable. This fluorescent sensing strategy is promising for the development of aptasensor in clinical fields.

Construction of CPs@MnO2-AgNPs as a multifunctional nanosensor for glutathione sensing and cancer theranostics

A multifunctional nanosensor of CPs@MnO₂-AgNPs was constructed for sensitive and selective sensing of GSH and cancer theranostics in this work. The CPs@MnO₂ nanocomposite was synthesized by capping MnO₂ onto carbon nanoparticles through an in situ redox reaction under ultrasonication. AgNPs with fluorescence were obtained through a silver-mirror-like reaction using BSA as both a template and reductant and further anchored onto the surface of CPs@MnO₂ through electrostatic interaction to construct the CPs@MnO₂-AgNP nanocomposite. The fluorescence of AgNPs was effectively quenched by MnO₂ through an inner filter effect and a static quenching effect and further recovered by GSH owing to the unique redox reaction between GSH and MnO₂. Therefore, a novel fluorescent turn-on nanosensor was established for GSH sensing in vitro and in vivo. For GSH sensing, a satisfactory linear range of 0.8-80 μM with a detection limit of 0.55 μM was obtained under optimal conditions. Moreover, by integrating the GSH-responsive fluorescence imaging capacity, the photothermal activity of carbon nanoparticles and the anticancer effect of AgNPs, the CPs@MnO₂-AgNP nanocomposite was successfully applied for cancer theranostics. The fluorescence recognition of cancer was achieved by overexpressing GSH in cancer, meanwhile the photothermal therapy from CPs and chemotherapy from AgNPs jointly produced an enhanced therapeutic effect. This redox-responsive nanocomposite of CPs@MnO₂-AgNPs improves the MnO₂ nanomaterial-based applications in GSH sensing and cancer theranostics.

Nanomaterials meet zebrafish: Toxicity evaluation and drug delivery applications

With the rapid development of engineered nanomaterials for various applications, in vivo toxicological studies for evaluating the potential hazardous effects of nanomaterials on environmental and human safety are in urgent need. Zebrafish has long been considered as the "gold standard" for biosafety assessments of chemicals and pollutants due to its high fecundity, cost-effectiveness, well-characterized developmental stages, optical transparency, and so forth. Thus, zebrafish holds great potential for high-throughput nanotoxicity screening. In this review, we summarize the in vivo toxicological profiles of different nanomaterials, including Ag nanoparticles (NPs), CuO NPs, silica NPs, polymeric NPs, quantum dots, nanoscale metal-organic frameworks, etc, in zebrafish and focus on how the physicochemical properties (e.g., size, surface charge, and surface chemistry) of these nanomaterials influence their biosafety. In addition, we also report the recent advances of the in vivo delivery of nanopharmaceuticals using zebrafish as the model organism for therapeutic assessment, biodistribution tracking, and the controlled release of loaded drugs. Limitations and special considerations of zebrafish model are also discussed. Overall, zebrafish is expected to serve as a high-throughput screening platform for nanotoxicity and drug delivery assessment, which may instruct the design of safe nanomaterials and more effective nanomedicines.

Exploring the behavior of gold nanostar@reduced graphene oxide composite in chemiluminescence: Application to highly sensitive detection of glutathione

Gold nanostar@reduced graphene oxide (GNS@rGO) nanocomposite was used as a catalyst in a chemiluminescence (CL) reaction. Composites with different sizes of gold nanostars were prepared without any surfactant, and characterized by transmission electron microscopy, UV-visible, FT-IR and Raman spectroscopy. We showed that GNS@rGO can strongly enhance the intensity of luminol‑sodium periodate CL system and the larger the GNS size, the greater the enhancing effect. This effect results from the unique catalytic action of GNS@rGO, which leads to the acceleration of reactive oxygen species generation. We also found that a remarkable increase in the CL intensity of GNS@rGO-luminol-NaIO₄ system occurs in the presence of glutathione (GSH). Based on this observation, a simple and highly sensitive CL probe was developed for detection of GSH. Under the optimum conditions, the calibration curve exhibits a linear range from 1.0 nM to 1.0 μM for GSH with a detection limit of 0.2 nM. The developed method was applied to the detection of GSH in human plasma samples.

Dual role of BSA for synthesis of MnO2 nanoparticles and their mediated fluorescent turn-on probe for glutathione determination and cancer cell recognition

A MnO₂ nanoparticle (MnO₂ NP)-mediated fluorescent turn-on probe for sensitively and selectively detecting glutathione (GSH) and recognizing cancer cells was established in this work. MnO₂ NPs were synthesized simply and quickly through an in situ redox reaction by mixing bovine serum albumin (BSA) and KMnO₄, in which BSA served the dual roles of template and reductant. It was found that the MnO₂ NPs served as an effective energy acceptor and quenched the fluorescence intensity of carbon dots (CDs), owing to the fluorescence resonance energy transfer (FRET) process. Further, the addition of GSH triggered the decomposition of MnO₂, breaking the FRET between MnO₂ NPs and CDs and thus restoring the fluorescence intensity of CDs. Based on this mechanism, quantitative determination of GSH was performed. Under optimal conditions, a satisfactory linear range of 0.05-90 μM and limit of detection of 39 nM were obtained, and GSH content in human serum samples was detected. Moreover, taking advantage of the higher levels of GSH in cancer cells than in normal cells, the MnO₂ NP-CD probe was applied to distinguish SMMC-7721 cancer cells from L02 normal cells. The FRET was interrupted by GSH in cancer cells, and strong fluorescence was observed. This work provides a facile approach for synthesizing MnO₂ NPs, and this rapid, low-cost method with no need for reductants makes synthesis green and convenient. The MnO₂ NP-mediated fluorescent turn-on response to GSH could improve the MnO₂ nanomaterial-based biochemical analysis applications.

Biomarkers-based Biosensing and Bioimaging with Graphene for Cancer Diagnosis

At the onset of cancer, specific biomarkers get elevated or modified in body fluids or tissues. Early diagnosis of these biomarkers can greatly improve the survival rate or facilitate effective treatment with different modalities. Potential nanomaterial-based biosensing and bioimaging are the main techniques in nanodiagnostics because of their ultra-high selectivity and sensitivity. Emerging graphene, including two dimensional (2D) graphene films, three dimensional (3D) graphene architectures and graphene hybrids (GHs) nanostructures, are attracting increasing interests in the field of biosensing and bioimaging. Due to their remarkable optical, electronic, and thermal properties; chemical and mechanical stability; large surface area; and good biocompatibility, graphene-based nanomaterials are applicable alternatives as versatile platforms to detect biomarkers at the early stage of cancer. Moreover, currently, extensive applications of graphene-based biosensing and bioimaging has resulted in promising prospects in cancer diagnosis. We also hope this review will provide critical insights to inspire more exciting researches to address the current remaining problems in this field.