A solid-state electrochemiluminescence biosensor for Con A detection based on CeO2@Ag nanoparticles modified graphene quantum dots as signal probe

Strategies to Enhance the Therapeutic Efficacy of GLP-1 Receptor Agonists through Structural Modification and Carrier Delivery

Diabetes is a metabolic disorder characterized by insufficient endogenous insulin production or impaired sensitivity to insulin. In recent years, a class of incretin-based hypoglycemic drugs, glucagon-like peptide-1 receptor agonists (GLP-1RAs), have attracted great attention in the management of type 2 diabetes mellitus (T2DM) due to their benefits, including stable glycemic control ability, a low risk of hypoglycemia, and weight reduction for patients. However, like other peptide drugs, GLP-1RAs face challenges such as instability, susceptibility to enzymatic degradation, and immunogenicity, which severely limit their clinical application. In recent years, various strategies have been developed to improve the bioavailability and therapeutic efficacy of GLP-1RAs, including structural modification and carrier-mediated delivery. This article briefly introduces the research and application status of several common GLP-1RAs and their limitations. Taking exendin-4 as an example, we focus on the research progress of improving bioavailability and therapeutic efficacy based on structural modification and carrier delivery strategies, aiming to provide reference for the development of new GLP-1RAs treatment systems.

Harnessing the Potential of Graphene Quantum Dots for Multifunctional Biomedical Applications

The existing and emerging demand for materials for life and health has contributed to the cultivation and development of respective markets. Nevertheless, the current generation of biomedical materials has yet to fully satisfy the clinical requirements of the market, which is still in its relative infancy. Research and development in this area must be prioritized in light of the pivotal role of new life and health materials in the biological field. Among many life and health materials, GQDs, an emerging nanomaterial, exhibit considerable promise in the biomedical field, primarily due to their exceptional properties. Furthermore, the direct preparation and functionalization of GQDs have facilitated the development of specific functional composites based on GQDs. The biological applications of GQDs are undergoing rapid growth, which makes it necessary to publish a review article presenting the latest advances in this field. This review provides an overview of the significant advances in synthesizing GQDs, the techniques employed for structural characterizations, and the properties that have been elucidated. Furthermore, it presents recent findings on applying GQDs in antimicrobial, anticancer, biosensing, drug delivery, and bioimaging applications. Finally, it explores the potential of GQDs in biomedicine and biotechnology, highlighting the current challenges that remain to be addressed.

Pyrene-Based Metal-Organic Frameworks with Coordination-Enhanced Electrochemiluminescence for Fabricating a Biosensing Platform

Enhancing the electrochemiluminescence (ECL) properties of polycyclic aromatic hydrocarbons (PAHs) is a significant topic in the ECL field. Herein, we elaborately chose PAH derivative luminophore 1,3,6,8-tetrakis(p-benzoic acid)pyrene (H4TBAPy) as the organic ligand to synthesize a new Ru-complex-free ECL-active metal-organic framework Dy-TBAPy. Interestingly, Dy-TBAPy exhibited a more brilliant ECL emission and higher ECL efficiency than H4TBAPy aggregates. On the one hand, TBAPy luminophores were assembled into rigid MOF skeleton via coordination bonds, which not only enlarged the distance between pyrene cores to eliminate the aggregation-caused quenching (ACQ) effect but also obstructed the intramolecular motions of TBAPy to diminish the nonradiative relaxation, thus realizing a remarkable coordination-enhanced ECL. On the other hand, the ultrahigh porosity of Dy-TBAPy was beneficial to the diffusion of electrons, ions, and coreactant (S2O82-) in the skeleton, which efficiently boosted the excitation of interior TBAPy luminophores and led to a high utilization ratio of TBAPy, further improving ECL properties. More intriguingly, the ECL intensity of the Dy-TBAPy/S2O82- system was about 4.1, 87.0-fold higher than those of classic Ru(bpy)32+/TPrA and Ru(bpy)32+/S2O82- systems. Considering the aforementioned fabulous ECL performance, Dy-TBAPy was used as an ECL probe to construct a supersensitive ECL biosensor for microRNA-21 detection, which showed an ultralow detection limit of 7.55 aM. Overall, our study manifests that coordinatively assembling PAHs into MOFs is a simple and practicable way to improve ECL properties, which solves the ACQ issue of PAHs and proposes new ideas for developing highly efficient Ru-complex-free ECL materials, therefore providing promising opportunities to fabricate high-sensitivity ECL biosensors.

A review on synthesis, properties, and biomedical applications of graphene quantum dots (GQDs)

A new type of 0-dimensional carbon-based materials called graphene quantum dots (GQDs) is gaining significant attention as a non-toxic and eco-friendly nanomaterial. GQDs are nanomaterials composed of sp2hybridized carbon domains and functional groups, with their lateral size less than 10 nm. The unique and exceptional physical, chemical, and optical properties arising from the combination of graphene structure and quantum confinement effect due to their nano-size make GQDs more intriguing than other nanomaterials. Particularly, the low toxicity and high solubility derived from the carbon core and abundant edge functional groups offer significant advantages for the application of GQDs in the biomedical field. In this review, we summarize various synthetic methods for preparing GQDs and important factors influencing the physical, chemical, optical, and biological properties of GQDs. Furthermore, the recent application of GQDs in the biomedical field, including biosensor, bioimaging, drug delivery, and therapeutics are discussed. Through this, we provide a brief insight on the tremendous potential of GQDs in biomedical applications and the challenges that need to be overcome in the future.

Significant Enhancement of Circular Polarization in Light Emission through Controlling Helical Pitches of Semiconductor Nanohelices

Circularly polarized light emission (CPLE) can be potentially applied to three-dimensional displays, information storage, and biometry. However, these applications are practically limited by a low purity of circular polarization, i.e., the small optical dissymmetry factor gCPLE. Herein, glancing angle deposition (GLAD) is performed to produce inorganic nanohelices (NHs) to generate CPLE with large gCPLE values. CdSe NHs emit red CPLE with gCPLE = 0.15 at a helical pitch (P) ≈ 570 nm, having a 40-fold amplification of gCPLE compared to that at P ≈ 160 nm. Ceria NHs emit ultraviolet-blue CPLE with gCPLE ≈ 0.06 at P ≈ 830 nm, with a 103-fold amplification compared to that at P ≈ 110 nm. Both the photoluminescence and scattering among the close-packed NHs complicatedly account for the large gCPLE values, as revealed by the numerical simulations. The GLAD-based NH-fabrication platform is devised to generate CPLE with engineerable color and large gCPLE = 10-2-10-1, shedding light on the commercialization of CPLE devices.

Recent advances in modification of novel carbon-based composites: Synthesis, properties, and biotechnological/ biomedical applications

Nowadays, carbon-based materials owing to great interest in biomedical science/biotechnology and applied for effective diagnosis and treatment of disease. To enhance the effectiveness of carbon nanotubes (CNTs)/graphene-based materials for bio-medical science/technology applications, different kinds of surface modification/functionalization were developed for the attachment of metal oxides nanostructures, biomolecules and polymers. The attachment of pharmaceutical agents with CNTs/graphene, make it a favorable candidate in research field of bio-medical science/technology applications. Surface modified/functionalized CNTs and graphene derivatives materials integrated with pharmaceutical agents has been developed for the purpose of cancer therapy, antibacterial action, pathogens bio detection, drug and gene delivery. Surface modification or functionalization of CNT/graphene materials provides good platform for pharmaceutical agents attachment with improved surface Raman scattering, fluorescence and its quenching capability. Graphene-based biosensing and bioimaging technologies are widely applied to identify numerous trace level analytes. These fluorescent and electrochemical sensors are utilized primarily for detecting organic, inorganic, and biomolecules. In this article, we highlights and summarized overview of the current research progress concerned on the CNTs/graphene-based materials as a new generation materials for detection and treatment of diseases.

On demand regulation of blood glucose level by biocompatible oxidized starch-Con A nanogels for glucose-responsive release of exenatide

Diabetes mellitus is a long-term chronic disease characterized by abnormal high level blood glucose (BG). An artificial closed-loop system that mimics pancreatic β-cells and releases insulin on demand has potential to improve the therapeutic efficiency of diabetes. Herein, a lectin Concanavalin A modified oxidized starch nanogel was designed to regulate glucose dynamically according to different glucose concentrations. The nanogels were formed by double cross-linking the Concanavalin A and glucose units on oxidized starch via specific binding and amide bonds to achieve the high drug loading and glucose responsiveness. The results showed that oxidized starch nanogels prolonged the half-life of antidiabetic peptide drug exenatide and released it in response to high BG concentrations. It could absorb BG at a high level and maintain glucose homeostasis. Besides, the oxidized starch nanogels performed well in recovering regular BG level from hyperglycemia state and maintaining in euglycemia state that fitted in a biological rhythm. In addition, the nanogels showed high biocompatibility in vivo and could improve plasma half-life and therapeutic efficacy of exenatide. Overall, the nanogels protected peptide drugs from degradation in plasma as a glucose-responsive platform showing a high potential for peptide drugs delivery and antidiabetic therapy.

Graphene quantum dots: synthesis, properties, and applications to the development of optical and electrochemical sensors for chemical sensing

GQDs exhibits exceptional electrochemical activity owing to their active edge sites that make them very attractive for biosensing applications. However, their use in the design of new biosensing devices for application to the detection and quantification of toxins, pathogens, and clinical biomarkers has so far not investigated in detail. In this regard, herein we provide a detailed review on various methodologies employed for the synthesis of GQDs, including bottom-up and top-down approaches, with a special focus on their applications in biosensing via fluorescence, photoluminescence, chemiluminescence, electrochemiluminescence, fluorescence resonance energy transfer, and electrochemical techniques. We believe that this review will shed light on the critical issues and widen the applications of GQDs for the design of biosensors with improved analytical response for future applications. HIGHLIGHTS: • Properties of GQDs play a critical role in biosensing applications. • Synthesis of GQDs using top-down and bottom-up approaches is discussed comprehensively. • Overview of advancements in GQD-based sensors over the last decade. • Methods for the design of selective and sensitive GQD-based sensors. • Challenges and opportunities for future GQD-based sensors.

Quantum dots for electrochemiluminescence bioanalysis - A review

Electrochemiluminescence (ECL) bioanalysis has become increasingly important in various fields from bioanalysis to clinical diagnosis due to its outstanding merits, including low background signal, high sensitivity, and simple instrumentation. Quantum dots (QDs) are a significant theme in ECL bioanalysis since their excellent optical, electrochemical properties, and ease of functionalization endow them with versatile roles and new mechanisms of signal transduction in ECL. Herein, this review details recent advances of QDs-based ECL bioanalysis by using QDs as ECL emitters, coreactants, or ECL resonance energy transfer donors/acceptors, mainly focused on their optical and electrochemical properties and ECL reaction mechanism. In the end, we will discuss the current limitations and future developments in QDs ECL bioanalysis to address the requirement about selectivity, sensitivity, toxicity, and emerging applications.

Cerium functionalized graphene nano-structures and their applications; A review

Graphene-based nanomaterials with remarkable properties, such as good biocompatibility, strong mechanical strength, and outstanding electrical conductivity, have dramatically shown excellent potential in various applications. Increasing surface area and porosity percentage, improvement of adsorption capacities, reduction of adsorption energy barrier, and also prevention of agglomeration of graphene layers are the main advantages of functionalized graphene nanocomposites. On the other hand, Cerium nanostructures with remarkable properties have received a great deal of attention in a wide range of fields; however, in some cases low conductivity limits their application in different applications. Therefore, the combination of cerium structures and graphene networks has been widely invesitaged to improve properties of the composite. In order to have a comprehensive information of these nanonetworks, this research reviews the recent developments in cerium functionalized graphene derivatives (graphene oxide (GO), reduced graphene oxide (RGO), and graphene quantum dot (GQD) and their industrial applications. The applications of functionalized graphene derivatives have also been successfully summarized. This systematic review study of graphene networks decorated with different structure of Cerium have potential to pave the way for scientific research not only in field of material science but also in fluorescent sensing, electrochemical sensing, supercapacitors, and catalyst as a new candidate.

Two-Dimensional Quantum Dot-Based Electrochemical Biosensors

Two-dimensional quantum dots (2D-QDs) derived from two-dimensional sheets have received increasing interest owing to their unique properties, such as large specific surface areas, abundant active sites, good aqueous dispersibility, excellent electrical property, easy functionalization, and so on. A variety of 2D-QDs have been developed based on different materials including graphene, black phosphorus, nitrides, transition metal dichalcogenides, transition metal oxides, and MXenes. These 2D-QDs share some common features due to the quantum confinement effects and they also possess unique properties owing to their structural differences. In this review, we discuss the categories, properties, and synthetic routes of these 2D-QDs and emphasize their applications in electrochemical biosensors. We deeply hope that this review not only stimulates more interest in 2D-QDs, but also promotes further development and applications of 2D-QDs in various research fields.

Ultrasensitive dual-quenching electrochemiluminescence immunosensor for prostate specific antigen detection based on graphitic carbon nitride quantum dots as an emitter

Early monitoring of prostate-specific antigen (PSA) is crucial in diagnosis and proactive treatment of prostate disease. Herein, a dual-quenching ternary ECL immunosensor was designed for PSA detection based on graphitic carbon nitride quantum dots (g-CNQDs, as an emitter), potassium persulfate (K2S2O8, as a coreactant), and silver nanoparticles doped multilayer Ti3C2 MXene hybrids (Ag@TCM, as a coreaction accelerator). First, Ag@TCM was immobilized on the surface of a glassy carbon electrode, then g-CNQDs was further adsorbed on Ag@TCM to acquire a higher initial ECL signal at a potential window from - 1.3 to 0.0 V (vs. Ag/AgCl). Ag@TCM not only acted as the coreaction accelerator, but also as a matrix to load enormous g-CNQDs and prostate-specific capture antibody via Ag-N bond. Meanwhile, prostate-specific detection antibody was marked by gold nanoparticles modified manganese dioxide as a dual-quenching probe (Ab2- Au@MnO2). When Ab2-Au@MnO2 was introduced into the ternary ECL system via sandwiched immuno-reaction, the high-sensitive detection of PSA was achieved by the dual-quenching effect, caused by the resonant energy transfer from g-CNQDs (energy donor) to Au@MnO2 (energy acceptor). As a result, this ECL immunosensor showed a good dynamic concentration range from 10 fg·mL-1 to 100 ng·mL-1 with a detection limit of 6.9 fg·mL-1 for PSA detection. The dual-quenching ECL strategy presented high stability and good specificity to open up a new pathway for ultrasensitive immunoassay.

One Step Production of Silver-Copper (AgCu) Nanoparticles

AgCu nanoparticles were prepared through hydrogen-reduction-assisted Ultrasonic Spray Pyrolysis (USP) and the Hydrogen Reduction (HR) method. The changes in the morphology and crystal structure of nanoparticles were studied using different concentrated precursors. The structure and morphology of the mixed crystalline particles were characterized through X-ray diffraction analysis (XRD), scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM) and Energy-dispersive X-ray spectroscopy (EDS). The average particle size decreased from 364 nm to 224 nm by reducing the initial solution concentration from 0.05 M to 0.4 M. These results indicate that the increase in concentration also increases the grain size. Antibacterial properties of nanoparticles against Escherichia coli were investigated. The obtained results indicate that produced particles show antibacterial activity (100%). The AgCu nanoparticles have the usage potential in different areas of the industry.

A dual signal-amplified electrochemiluminescence immunosensor based on core-shell CeO2-Au@Pt nanosphere for procalcitonin detection

A dual signal-amplified sandwich electrochemiluminescence (ECL) immunosensor was fabricated for trace detection of procalcitonin (PCT). CeO2-Au@Pt composed of sea urchin-like Au@Pt nanoparticles coated on CeO2 hollow nanospheres was immobilized on electrode surface to electrochemically catalyze H2O2 to produce a large number of superoxide anion (O2•-). The immunosensor was prepared by linking the capture antibody on immobilized CeO2-Au@Pt with heptapeptide (HWRGWVC), which could maintain the activity of the antibody. The prepared Au star@BSA was used to bind abundant luminol for labeling the secondary antibody (Ab2). Upon the sandwich-typed immunoreactions, the O2•- could react with the introduced luminol on the immunosensor surface to produce strong ECL intensity. With an outstanding linear detection range and a low detection limit of 17 fg/mL, the ECL immunosensor permitted ultrasensitive detection of PCT at a low H2O2 concentration and demonstrated its high application potential in the clinical assay.

Analyzing Near-Infrared Electrochemiluminescence of Graphene Quantum Dots in Aqueous Media

Mechanisms of emissions, especially electrochemiluminescence (ECL), for graphene quantum dots (GQDs) are poorly understood, which makes near-infrared (NIR)-emitting GQDs difficult to create. To explore this poorly understood NIR ECL, two GQDs, nitrogen-doped GQDs (GQD-1) and nitrogen- and sulfur-doped ones (GQD-2), were prepared by a simple one-step solvothermal reaction with similar core structures but different surface states. The GQDs were analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Photoluminescence results, with a comparable quantum efficiency of 13% to strong luminophores in aqueous media, suggested a mechanism that the emission mainly depends on the core structure while slightly adjusted by the heteroatom doping. ECL of GQD-2 dispersed in aqueous media with K₂S₂O₈ as the coreactant was measured by means of ECL-voltage curves and ECL spectroscopy, demonstrating strong NIR emissions between 680 and 870 nm, with a high ECL efficiency of 13% relative to that of the Ru(bpy)₃²⁺/K₂S₂O₈ system. Interestingly, ECL is generated by surface excited states emitting light at a much longer wavelength in the NIR region. The easily prepared GQD-2 has several advantages such as low cost and quite strong NIR-ECL in aqueous media, with which wide applications in biodetection are anticipated.

Functionalized europium-porphyrin coordination polymer: Rational design of high performance electrochemiluminescence emitter for mucin 1 sensing

The excellent characteristics of porphyrins have inspired widespread interest in electrochemiluminescence (ECL). However, the limited ECL intensity and poor stability of porphyrins in aqueous solution are still severely restricted further biological application. Here, we subtly synthesized a functionalized europium and 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) coordination polymer (Eu-PCP) by a one-step solvothermal method. In sharp contrast to the pristine TCPP, Eu-PCP showed a higher and more stable ECL red-light emission (673 nm) at low potential (-1.1 V, vs Ag/AgCl), which was 7.7-fold higher ECL intensity and 4.6-fold efficiency. In view of the crucial role of mucin 1 (MUC1) in tumor overexpression, it was selected as the target molecule. Combined with exonuclease III (Exo III)-assisted recycling amplification strategy, a ternary ECL biosensor was constructed for the MUC1 detection based on Eu-PCP as a satisfied ECL emitter, gold nanoparticles capped CeO₂ (CeO₂@Au) as the coreactant accelerator and peroxydisulfate as coreactant. Meanwhile, gold nanoparticles capped MnO₂ (MnO₂@Au) was used as the quenching probe to achieve a highly sensitive detection of MUC1. The proposed biosensor exhibited a wide linear range from 1 fg mL^-1 to 10 ng mL^-1 with a low limit of detection (0.32 fg mL^-1). By changing the corresponding target recognition DNA, this strategy could be expanded to detect other biomarkers.

Antimicrobial gum bio-based nanocomposites and their industrial and biomedical applications

Gum polysaccharides are derived from renewable sources. They are readily available, inexpensive, non-hazardous and eco-friendly. Depending upon the source, gums may be categorized as microbial gums, plant exudate gums or seed gums. Naturally occurring gum carbohydrates find multiple applications in the biomedical arena, compared with synthetic compounds, because of their unique structures and functionalities. Gums and their biocomposites are preferred for sustained drug delivery because they are safe and edible as well as more susceptible to biodegradation. The present review provides a state-of-the-art conspectus on the industrial and biomedical applications of antimicrobial gum-based biocomposites. Different kinds of gums polysaccharides will first be addressed based on their sources. Metal-, carbon- and organic-based nanostructures that are used in gum nanocomposites will then be reviewed with respect to their industrial and biomedical applications, to provide a backdrop for future research.

Review of Carbon and Graphene Quantum Dots for Sensing

Carbon and graphene quantum dots (CQDs and GQDs), known as zero-dimensional (0D) nanomaterials, have been attracting increasing attention in sensing and bioimaging. Their unique electronic, fluorescent, photoluminescent, chemiluminescent, and electrochemiluminescent properties are what gives them potential in sensing. In this Review, we summarize the basic knowledge on CQDs and GQDs before focusing on their application to sensing thus far followed by a discussion of future directions for research into CQDs- and GQD-based nanomaterials in sensing. With regard to the latter, the authors suggest that with the potential of these nanomaterials in sensing more research is needed on understanding their optical properties and why the synthetic methods influence their properties so much, into methods of surface functionalization that provide greater selectivity in sensing and into new sensing concepts that utilize the virtues of these nanomaterials to give us new or better sensors that could not be achieved in other ways.

Recent Advances on Graphene Quantum Dots: From Chemistry and Physics to Applications

Graphene quantum dots (GQDs) that are flat 0D nanomaterials have attracted increasing interest because of their exceptional chemicophysical properties and novel applications in energy conversion and storage, electro/photo/chemical catalysis, flexible devices, sensing, display, imaging, and theranostics. The significant advances in the recent years are summarized with comparative and balanced discussion. The differences between GQDs and other nanomaterials, including their nanocarbon cousins, are emphasized, and the unique advantages of GQDs for specific applications are highlighted. The current challenges and outlook of this growing field are also discussed.