Multifunctional Carbon Dots for Biomedical Applications: Diagnosis, Therapy, and Theranostic

Dentistry Insights: Single-Walled and Multi-Walled Carbon Nanotubes, Carbon Dots, and the Rise of Hybrid Materials

We are committed to writing this narrative review given that carbon-based nanomaterials are revolutionizing dental medicine. Since the groundbreaking discovery of carbon nanotubes in 1991, their dental applications have skyrocketed. The numbers speak for themselves: in 2024, the global carbon nanotubes market hit USD 1.3 billion and is set to double to USD 2.6 billion by 2029. Over the past few decades, various forms of carbon nanomaterials have been integrated into dental practices, elevating the quality and effectiveness of dental treatments. They represent a transformative advancement in dentistry, offering numerous benefits such as augmented mechanical properties, antimicrobial activity, and potential for regenerative applications. Both carbon nanotubes (CNTs) and carbon dots (CDs) are derived from carbon and integral to nanotechnology, showcasing the versatility of carbon nanostructures and delivering cutting-edge solutions across diverse domains, such as electronics, materials science, and biomedicine. CNTs are ambitiously examined for their capability to reinforce dental materials, develop biosensors for detecting oral diseases, and even deliver therapeutic agents directly to affected tissues. This review synthesizes their current applications, underscores their interdisciplinary value in bridging nanotechnology and dentistry, identifies key barriers to clinical adoption, and discusses hybrid strategies warranting further research to advance implementation.

Programmed Transformation of Osteogenesis Microenvironment by a Multifunctional Hydrogel to Enhance Repair of Infectious Bone Defects

Repair of infectious bone defects remains a serious problem in clinical practice owing to the high risk of infection and excessive reactive oxygen species (ROS) during the early stage, and the residual bacteria and delayed Osseo integrated interface in the later stage, which jointly creates a complex and dynamic microenvironment and leads to bone non-union. The melatonin carbon dots (MCDs) possess antibacterial and osteogenesis abilities, greatly simplifying the composition of a multifunctional material. Therefore, a multifunctional hydrogel containing MCDs (GH-MCD) is developed to meet the multi-stage and complex repair needs of infectious bone injury in this study. The GH-MCD can intelligently release MCDs responding to the acidic microenvironment to scavenge intracellular ROS and exhibit good antibacterial activity by inducing the production of ROS in bacteria and inhibiting the expression of secA2. Moreover, it has high osteogenesis and long-lasting antimicrobial activity during bone repair. RNA-seq results reveal that the hydrogels promote the repair of infected bone healing by enhancing cellular resistance to bacteria, balancing osteogenesis and osteoclastogenesis, and regulating the immune microenvironment. In conclusion, the GH-MCD can promote the repair of infectious bone defects through the programmed transformation of the microenvironment, providing a novel strategy for infectious bone defects.

Covalent Functionalisation of rGO and Nanodiamonds: Complementary Versatility and Applicability of Azomethine Ylide, Nitrile Oxide and Nitrone

The existing synthetic protocols for the direct functionalization of carbon-based nanomaterials often entail limitations due to their harsh reaction conditions, which require the use of high temperatures for extended periods. This study aims to overcome these limitations by developing mild and efficient synthetic protocols around 1,3-dipolar cycloaddition. Beginning with the well-established azomethine ylide derivatization, we progress to the utilization of nitrile oxide, and of nitrone derivatives for the functionalization of reduced graphene oxide (rGO) as well as of nanodiamonds (NDs). This comparative work employs both classical heating and microwave activation with the aim of reducing reaction times and enhancing efficacy. Results demonstrate that nitrone can react at 60 °C and that the reaction temperature may be decreased to 30 °C with nitrile oxide. Excellent progress was made in reducing the large excess of dipoles typically required for derivatization. Nitrile oxide was proved to be the most efficient in terms of derivatization degree, while nitrone was the most versatile reagent, facilitating the decoration of the carbon nanolayer with disubstituted dihydroisoxazole. To accurately assess the degree of functionalization, the reaction products underwent characterization using various spectroscopic and analytical techniques. Additionally, an indirect evaluation of the reaction outcome was conducted through Fmoc deprotection and quantification.

Revolutionizing nanozymes: The synthesis, enzyme-mimicking capabilities of carbon dots, and advancements in catalytic mechanisms

Nanozymes, a revolutionary category of engineered artificial enzymes based on nanomaterials, have been developed to overcome the inherent limitations of natural enzymes, such as the high cost associated with storage and their fragility. Carbon dots (CDs) have emerged as compelling candidates for various applications due to their versatile properties. Particularly noteworthy are CDs with a range of surface functional groups that exhibit enzyme-like behavior, combining exceptional performance with catalytic capabilities. This review explores the methodologies used for synthesizing CDs with enzyme mimicking capabilities, highlighting potential avenues such as doping and hybrid nanozymes to enhance their catalytic efficacy. Moreover, a comprehensive overview of CDs that mimick the activities of various oxidoreductases-like peroxidase, catalase, oxidase/laccase, and superoxide dismutase-like is provided. The focus is on the in-depth exploration of the mechanisms, advancements and practical applications of each oxidoreductase-like function exhibited by CD nanozymes. Drawing upon these exhaustive summaries and analyses, the review identifies the prevailing challenges that hinder the seamless integration of CDs into real-world applications and offers forward-looking perspectives for future directions.

Carbon dots derived from organic drug molecules with improved therapeutic effects and new functions

Carbon dots (CDs) are new types of fluorescent nanomaterials with particle diameters of 1∼10 nm and have excellent photoluminescence (PL) properties, good biocompatibility, simple preparation methods and numerous raw materials; consequently, they are promising in the biomedical field. In recent years, to overcome drug resistance and toxic side effects of traditional organic drugs, the synthesis of CDs from drug molecules has become an effective strategy, which produces CDs with the same therapeutic effects as the raw drugs and even possessing new properties. At present, many CDs derived from organic drugs have been developed, which can be classified according to their sources such as antibiotics, anti-inflammatory drugs, and guanidine drugs. This article focuses on the progress of the above-mentioned drug-derived CDs compared with their drug precursors in terms of therapeutic efficacy, enhanced performance and new additional functions, with special attention to the structure-activity relationship between the drug precursors and the CD-based therapeutic agents. It demonstrates the feasibility of designing new drug-derived CDs for clinical applications, summarizes the shortcomings and research gaps of the existing work, and provides a reference for related work in the future.

Biomass-Derived Carbon Dots as Fluorescent Probes for Label-Free Sensing of Hemin and as Radical Scavengers

Carbon dots (CDs) derived from biomass are promising fluorescent probes for specific analyte detection due to their specificity, biocompatibility, selectivity, and sensitivity. In this work, carbon dots were prepared hydrothermally from natural material, Myrica esculenta fruits (hereafter referred to as MPCDs), without adding any chemicals. The prepared MPCDs were characterized using optical, microscopic, and spectroscopic methods that revealed the presence of numerous functional groups and fluorescent properties. MPCDs exhibited exceptional characteristics such as water solubility, photostability, excitation-dependent fluorescence emission, and ionic stability. Transmission electron microscopy found that the average size of the MPCDs was 8 nm. MPCDs exhibited remarkable sensing ability for hemin, with a good linearity (R2 = 0.999) and a lower limit of detection of 14.1 nM. MPCDs demonstrated fluorescence quenching-based detection of hemin, primarily owing to ground state complex formation and the inner filter effect. Furthermore, the prepared material exhibited excellent antioxidant potential against 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) and 2,2-diphenyl-1-picrylhydrazyl radicals with EC50 values of 25.4 and 205.4 µg/mL, respectively. The study suggests that CDs from Myrica esculenta fruits could be used as optical sensors for hemin detection as well as to scavenge selected radicals.

Ultrasensitive and Selective Nitrogen-Doped Fluorescent Carbon Dots Probe for Quantification Analysis of Trace Cu2+ in the Aqueous Environment

As a typical non-ferrous metal, copper is heavily used in the manufacturing and chemical industries. Copper pollution has been demonstrated to have a significant detrimental impact on the natural environment, as well as causing irreparable damage to the human body, such as elevated Cu2+ levels have been identified as a factor in the pathogenesis of AD (Alzheimer's disease). In this study, novel nanoscale carbon dots Blue-CDs (B-CDs) were obtained by the solvothermal approach in formamide solution utilizing citric acid as the carbon source and ethylenediamine as the nitrogen dopant. The particle size of B-CD was assessed to be 2.17 nm, with a quantum yield (QY) of 10.28%. The B-CDs were found to be extinguished upon exposure to Cu2+, which exhibited a good fluorescence detection linear relationship within the concentration range of 0.25-10.0 µM Cu2+, showing a limit of detection (LOD) is 0.18 µM. B-CDs have been effectively used for the measurement of Cu2+ in actual aqueous systems. It is due to the chemical reactions that take place among the B-CDs and the Cu²⁺ that make the sensor highly sensitivities and highly selectivities. The results of the experiment demonstrate that the fluorescence quenching process is a consequence of Cu2+ binding to the amino groups of carbon dots, forming complexes via a non-radiative photoinduced electron transfer process. In conclusion, the described simple sensing techniques could be effectively utilized as monitoring tools for Cu2+ in environmental waters.

Enhancing the Fluorescence and Antimicrobial Performance of Carbon Dots via Hypochlorite Treatment

This paper presents a simple, post-synthesis treatment of carbon dots (C-dots) that relies on the oxidizing activity of sodium hypochlorite to induce surface oxidation, etching and pronounced structural rearrangements. The thus treated C-dots (ox-C-dots) exhibit up to six-fold enhancement in quantum yield compared to non-oxidised analogues, while maintaining low levels of cytotoxicity against HeLa and U87 cell lines. In addition, we demonstrate that a range of polymeric materials (polyurethane sponge, polyvinylidene fluoride membrane, polyester fabric) impregnated with ox-C-dots show advanced antifungal properties against Talaromyces pinophilus, while their untreated counterparts fail to do so.

Long-chain surface-modified red-emitting carbon dots as fluorescent additives for 3D printing vat-photopolymerization

Carbon dots have recently attracted tremendous scientific attention thanks to their enhanced luminescence properties, photostability and low toxicity. In particular, red-emitting carbon dots (RCDs) are assuming increasing importance in biomedical applications, such as bio-imaging and phototherapy. At the same time, the possibility to create functional and complex objects by means of vat-photopolymerization-based three-dimensional (3D) printing techniques is continuously growing. This work describes the synthesis of long-chain surface-modified red emitting carbon dots, L-RCDs by esterification of RCDs, obtained from green reagents with a new solvothermal synthesis, and their employment as fluorescent additives in two formulations of photopolymerizable resins. The printing process proceeded smoothly in all cases, and red-emitting objects with different mechanical properties have been successfully obtained.

Advancing rhodium nanoparticle-based photodynamic cancer therapy: quantitative proteomics and in vivo assessment reveal mechanisms targeting tumor metabolism, progression and drug resistance

Rhodium nanoparticles have been recently discovered as good photosensitizers with great potential in cancer photodynamic therapy by effectively inducing cytotoxicity in cancer cells under near-infrared laser. This study evaluates the molecular mechanisms underlying such antitumoral effect through quantitative proteomics. The results revealed that rhodium nanoparticle-based photodynamic therapy disrupts tumor metabolism by downregulating key proteins involved in ATP synthesis and mitochondrial function, leading to compromised energy production. The treatment also induces oxidative stress and apoptosis while targeting the invasion capacity of cancer cells. Additionally, key proteins involved in drug resistance are also affected, demonstrating the efficacy of the treatment in a multi-drug resistant cell line. In vivo evaluation using a chicken embryo model also confirmed the effectiveness of the proposed therapy in reducing tumor growth without affecting embryo viability.

Recent developments in two-dimensional molybdenum disulfide-based multimodal cancer theranostics

Recent advancements in cancer research have led to the generation of innovative nanomaterials for improved diagnostic and therapeutic strategies. Despite the proven potential of two-dimensional (2D) molybdenum disulfide (MoS2) as a versatile platform in biomedical applications, few review articles have focused on MoS2-based platforms for cancer theranostics. This review aims to fill this gap by providing a comprehensive overview of the latest developments in 2D MoS2 cancer theranostics and emerging strategies in this field. This review highlights the potential applications of 2D MoS2 in single-model imaging and therapy, including fluorescence imaging, photoacoustic imaging, photothermal therapy, and catalytic therapy. This review further classifies the potential of 2D MoS2 in multimodal imaging for diagnostic and synergistic theranostic platforms. In particular, this review underscores the progress of 2D MoS2 as an integrated drug delivery system, covering a broad spectrum of therapeutic strategies from chemotherapy and gene therapy to immunotherapy and photodynamic therapy. Finally, this review discusses the current challenges and future perspectives in meeting the diverse demands of advanced cancer diagnostic and theranostic applications.

Catalytic Nanodots-Driven Pyroptosis Suppression in Nucleus Pulposus for Antioxidant Intervention of Intervertebral Disc Degeneration

Low back pain resulting from intervertebral disc degeneration (IVDD) is a prevalent global concern; however, its underlying mechanism remains elusive. Single-cell sequencing analyses revealed the critical involvement of pyroptosis in IVDD. Considering the involvement of reactive oxygen species (ROS) as the primary instigator of pyroptosis and the lack of an efficient intervention approach, this study developed carbonized Mn-containing nanodots (MCDs) as ROS-scavenging catalytic biomaterials to suppress pyroptosis of nucleus pulposus (NP) cells to efficiently alleviate IVDD. Catalytic MCDs have superior efficacy in scavenging intracellular ROS and rescuing homeostasis in the NP microenvironment compared with N-acetylcysteine, a classical antioxidant. The data validates that pyroptosis plays a vital role in mediating the protective effects of catalytic MCDs against oxidative stress. Systematic in vivo assessments substantiate the effectiveness of MCDs in rescuing a puncture-induced IVDD rat model, further demonstrating their ability to suppress pyroptosis. This study highlights the potential of antioxidant catalytic nanomedicine as a pyroptosis inhibitor and mechanistically unveils an efficient strategy for the treatment of IVDD.

Advances in Atherosclerosis Theranostics Harnessing Iron Oxide-Based Nanoparticles

Atherosclerosis, a multifaceted chronic inflammatory disease, has a profound impact on cardiovascular health. However, the critical limitations of atherosclerosis management include the delayed detection of advanced stages, the intricate assessment of plaque stability, and the absence of efficacious therapeutic strategies. Nanotheranostic based on nanotechnology offers a novel paradigm for addressing these challenges by amalgamating advanced imaging capabilities with targeted therapeutic interventions. Meanwhile, iron oxide nanoparticles have emerged as compelling candidates for theranostic applications in atherosclerosis due to their magnetic resonance imaging capability and biosafety. This review delineates the current state and prospects of iron oxide nanoparticle-based nanotheranostics in the realm of atherosclerosis, including pivotal aspects of atherosclerosis development, the pertinent targeting strategies involved in disease pathogenesis, and the diagnostic and therapeutic roles of iron oxide nanoparticles. Furthermore, this review provides a comprehensive overview of theranostic nanomedicine approaches employing iron oxide nanoparticles, encompassing chemical therapy, physical stimulation therapy, and biological therapy. Finally, this review proposes and discusses the challenges and prospects associated with translating these innovative strategies into clinically viable anti-atherosclerosis interventions. In conclusion, this review offers new insights into the future of atherosclerosis theranostic, showcasing the remarkable potential of iron oxide-based nanoparticles as versatile tools in the battle against atherosclerosis.

Carbon-coated selenium nanoparticles for photothermal therapy in choriocarcinoma cells

Choriocarcinoma can be cured by chemotherapy, but this causes resistance and severe side effects that bring about physical and psychological consequences for patients. Therefore, there is still an urgent need to find other alternative minimally invasive therapies to halt the progression of choriocarcinoma. Novel carbon-coated selenium nanoparticles (C-Se) were successfully synthesized for choriocarcinoma photothermal therapy. C-Se combined with near-infrared laser irradiation can inhibit the proliferation of human choriocarcinoma (JEG-3) cells and induce cell apoptosis. C-Se killed cells and produced ROS under near-infrared laser irradiation. Finally, the therapeutic mechanism of C-Se + laser was explored showing that C-Se + laser influenced numerous biological processes. Taken together, C-Se exhibited significant potential for choriocarcinoma photothermal therapy.

Red-Emissive Center Formation within Carbon Dots Based on Citric Acid and Formamide

The formation of red-emissive optical centers in carbon dots based on citric acid and formamide was investigated by varying the synthesis parameters with focus on finding optimal─necessary and sufficient─amount of precursors to decrease byproduct amount and to increase the chemical yield of red-emissive carbon dots. The emission is observed at 640 nm excited at 590 nm and quantum yield reaches up 19%. A high chemical yield of carbon dots of 26% was achieved at an optimal molar ratio of citric acid to formamide of 1:4.

Biological Synthesis, Characterization, and Therapeutic Potential of S. commune-Mediated Gold Nanoparticles

Green-synthesized gold nanoparticles demonstrate several therapeutic benefits due to their safety, non-toxicity, accessibility, and ecological acceptance. In our study, gold nanoparticles (AuNPs) were created using an extracellular extract from the fungus Schizophyllum commune (S. commune). The reaction color was observed to be a reddish pink after a 24 h reaction, demonstrating the synthesis of the nanoparticles. The myco-produced nanoparticles were investigated using transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV-visible spectroscopy. The TEM pictures depicted sphere-like shapes with sizes ranging from 60 and 120 nm, with an average diameter of 90 nm, which is in agreement with the DLS results. Furthermore, the efficiency of the AuNPs' antifungal and cytotoxic properties, as well as their production of intracellular ROS, was evaluated. Our findings showed that the AuNPs have strong antifungal effects against Trichoderma sp. and Aspergillus flavus at increasing doses. Additionally, the AuNPs established a dose-dependent activity against human alveolar basal epithelial cells with adenocarcinoma (A549), demonstrating the potency of synthesized AuNPs as a cytotoxic agent. After 4 h of incubation with AuNPs, a significant increase in intracellular ROS was observed in cancer cells. Therefore, these metallic AuNPs produced by fungus (S. commune) can be used as an effective antifungal, anticancer, and non-toxic immunomodulatory delivery agent.