Red-Emissive Carbon Dots for Fluorescent, Photoacoustic, and Thermal Theranostics in Living Mice

Advances on carbon nanomaterials and their applications in medical diagnosis and drug delivery

Carbon nanomaterials are indispensable due to their unique properties of high electrical conductivity, mechanical strength and thermal stability, which makes them important nanomaterials in biomedical applications and waste management. Limitations of conventional nanomaterials, such as limited surface area, difficulty in fine tuning electrical or thermal properties and poor dispersibility, calls for the development of advanced nanomaterials to overcome such limitations. Commonly, carbon nanomaterials were synthesized by chemical vapor deposition (CVD), laser ablation or arc discharge methods. The advancement in these techniques yielded monodispersed carbon nanotubes (CNTs) and allows p-type and n-type doping to enhance its electrical and catalytic activities. The functionalized CNTs showed exceptional mechanical, electrical and thermal conductivity (3500-5000 W/mK) properties. On the other hand, carbon quantum dots (CQDs) exhibit strong photoluminescence properties with high quantum yield. Carbon nanohorns are another fascinating type of nanomaterial that exhibit a unique structure with high surface area and excellent adsorption properties. These carbon nanomaterials could improve waste management by adsorbing pollutants from water and soil, enabling precise environmental monitoring, while enhancing wastewater treatment and drug delivery systems. Herein, we have discussed the potentials of all these carbon nanomaterials in the context of innovative waste management solutions, fostering cleaner environments and healthier ecosystems for diverse biomedical applications such as biosensing, drug delivery, and environmental monitoring.

Surface State-Based panchromatic luminescent carbon dots

Carbon dots have shown a broad application prospect in the fields of sensing and detection, biological imaging, and optoelectronic devices. However, it is still challenging to adopt a simple and green synthesis route and to develop new precursor systems to prepare full-color luminescent carbon dots. This study proposes a mechanism for fine regulation of carbon dot fluorescence spectra based on surface states of CN, COC, and OH, among which CN play a major role in long wavelength emission while COC and OH are responsible for the blue shift of emission wavelength. Using 4,4-bipyridine and p-phenylenediamine as precursors in safe and environmentally friendly glycol and water as solvents for the first time, the fine spectral carbon dots with full spectrum luminescence from purple (441 nm) to red (627 nm) were successfully synthesized by simply changing the composition of the reaction solvent and using a short reaction time. Compared with other reports on regulating polychromatic carbon dots, our method is more refined and has a wider distribution of luminescent colors. In addition, the obtained carbon dots based on such surface state luminescence mechanism have shown good application prospects in specific detection of Fe3+and cell labeling.

Advance of Near-Infrared Emissive Carbon Dots in Diagnosis and Therapy: Synthesis, Luminescence, and Application

Carbon dots (CDs) with good optical properties, biocompatibility, easy functionalization, and small size have attracted more and more attention and laid a good foundation for their applications in the biomedicine field. CDs emitted in near-infrared regions (NIR-CDs) can achieve high penetration depth imaging and produce high cytotoxic substance for disease treatment. Therefore, NIR-CDs are promising materials to realize high-quality imaging-guided diagnostic and therapeutic integration. This review first introduces the current mainstream synthesis methods of NIR-CDs by "top-down" and "bottom-up". Second, the luminescence modes of NIR-CDs are introduced, and the luminescence mechanisms based on carbon core state, surface state, molecular state, and crosslinking enhanced emission are summarized. Third, the applications and principles of NIR-CDs in imaging, drug delivery, and non-invasive therapeutics are introduced from a view of diagnosis and therapy. Finally, their prospects and challenges in biomedical and biotechnological applications are outlined.

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Graphitic Carbon Nitride Quantum Dots (g-C3N4 QDs): From Chemistry to Applications

Since their emergence in 2014, graphitic carbon nitride quantum dots (g-C3N4 QDs) have attracted much interest from the scientific community due to their distinctive physicochemical features, including structural, morphological, electrochemical, and optoelectronic properties. Owing to their desirable characteristics, such as non-zero band gap, ability to be chemically functionalized or doped, possessing tunable properties, outstanding dispersibility in different media, and biocompatibility, g-C3N4 QDs have shown promise for photocatalysis, energy devices, sensing, bioimaging, solar cells, optoelectronics, among other applications. As these fields are rapidly evolving, it is very strenuous to pinpoint the emerging challenges of the g-C3N4 QDs development and application during the last decade, mainly due to the lack of critical reviews of the innovations in the g-C3N4 QDs synthesis pathways and domains of application. Herein, an extensive survey is conducted on the g-C3N4 QDs synthesis, characterization, and applications. Scenarios for the future development of g-C3N4 QDs and their potential applications are highlighted and discussed in detail. The provided critical section suggests a myriad of opportunities for g-C3N4 QDs, especially for their synthesis and functionalization, where a combination of eco-friendly/single step synthesis and chemical modification may be used to prepare g-C3N4 QDs with, for example, enhanced photoluminescence and production yields.

Ultrasmall Carbon Nanodots as Theranostic Nanoheaters for Precision Breast Cancer Phototherapy: Establishing the Translational Potential in Tumor-in-a-Dish Models

This study investigates the remarkable attributes of sulfur-doped carbon nanodots (CDs) synthesized in high yield and a narrow size distribution (4.8 nm). These CDs exhibit notable features, including potential bioelimination through renal clearance and efficient photothermal conversion in the near-infrared region with multicolor photoluminescence across the visible spectrum. Our research demonstrates high biocompatibility and effective near-infrared (NIR)-triggered photothermal toxicity when targeting mammospheres and patient-derived tumor organoids. Moreover, the study delves into the intricate cellular responses induced by CD-mediated hyperthermia. This involves efficient tumor mass death, activation of the p38-mitogen-activated protein kinase (MAPK) pathway, and upregulation of genes associated with apoptosis, hypoxia, and autophagy. The interaction of CDs with mammospheres reveals their ability to penetrate the complex microenvironment, impeded at 4 °C, indicating an energy-dependent endocytosis mechanism. This observation underscores the CDs' potential for targeted drug delivery, particularly in anticancer therapeutics. This investigation contributes to understanding the multifunctional properties of sulfur-doped CDs and highlights their promising applications in cancer therapeutics. Utilizing 3-D tumor-in-a-dish patients' organoids enhances translational potential, providing a clinically relevant platform for assessing therapeutic efficacy in a context mirroring the physiological conditions of cancerous tissues.

Advances and perspectives in phototherapy-based combination therapy for cancer treatment

Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT), has the advantages of spatiotemporal selectivity, non-invasiveness, and negligible drug resistance. Phototherapy has been approved for treating superficial epidermal tumors. However, its therapeutic efficacy is limited by the hypoxic tumor microenvironment and the highly expressed heat shock protein. Moreover, poor tissue penetration and focused irradiation laser region in phototherapy make treating deep tissues and metastatic tumors challenging. Combination therapy strategies, which integrate the advantages of each treatment and overcome their disadvantages, can significantly improve the therapeutic efficacy. Recently, many combination therapy strategies have been reported. Our study summarizes the strategies used for combining phototherapy with other cancer treatments such as chemotherapy, immunotherapy, sonodynamic therapy, gas therapy, starvation therapy, and chemodynamic therapy. Some research cases were selected to analyze the combination therapy effect, delivery platform feature, and synergetic anticancer mechanisms. Moreover, additional research cases are summarized in the tables. This review provides strong evidence that phototherapy-based combination strategies can enhance the anticancer effect compared with phototherapy alone. Additionally, the challenges and future perspectives associated with these combinational therapies are discussed.

Red/NIR-I-Fluorescence Carbon Dots Based on Rhein with Active Oxygen Scavenging and Colitis Targeting for UC Therapeutics

Ulcerative colitis (UC) is a chronic inflammatory disease with uncontrolled inflammation and demage to the intestinal barrier. Rhein, a bioactive compound in traditional Chinese medicine, has anti-inflammatory and intestinal repair effect. However, their clinical application is limited by their hydrophobicity and poor bioavailability. L-arginine, as a complement to NO, has synergistic and attenuating effects. In this paper, red/NIR-I fluorescent carbon dots based on rhein and doped with L-arginine (RA-CDs), which are synthesized by a hydrothermal process without any organic solvents, are reported. RA-CDs preserve a portion of the functional group of the active precursor, increase rhein solubility, and emit red/NIR-I light for biological imaging. In vitro experiments show that RA-CDs scavenge excessive reactive oxygen species (ROS), protect cells from oxidative stress, and enable the fluorescence imaging of inflamed colons. In a DSS-induced UC mouse model, both delayed and prophylactic treatment with RA-CDs via intraperitoneal and tail vein injections alleviate UC severity by reducing intestinal inflammation and restoring the intestinal barrier. This study highlights a novel strategy for treating and imaging UC with poorly soluble small-molecule drugs.

Nano-based drug delivery systems in hepatocellular carcinoma

The high recurrence rate of hepatocellular carcinoma (HCC) and poor prognosis after medical treatment reflects the necessity to improve the current chemotherapy protocols, particularly drug delivery methods. Development of targeted and efficient drug delivery systems (DDSs), in all active, passive and stimuli-responsive forms for selective delivery of therapeutic drugs to the tumour site has been extended to improve efficacy and reduce the severe side effects. Recent advances in nanotechnology offer promising breakthroughs in the diagnosis, treatment and monitoring of cancer cells. In this review, the specific design of DDSs based on the different nano-particles and their surface engineering is discussed. In addition, the innovative clinical studies in which nano-based DDS was used in the treatment of HCC were highlighted.

Biomedical applications of graphene-based nanomaterials: recent progress, challenges, and prospects in highly sensitive biosensors

Graphene-based nanomaterials (graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, graphene-based nanocomposites, etc.) are emerging as an extremely important class of nanomaterials primarily because of their unique and advantageous physical, chemical, biological, and optoelectronic aspects. These features have resulted in uses across diverse areas of scientific research. Among all other applications, they are found to be particularly useful in designing highly sensitive biosensors. Numerous studies have established their efficacy in sensing pathogens and other biomolecules allowing for the rapid diagnosis of various diseases. Considering the growing importance and popularity of graphene-based materials for biosensing applications, this review aims to provide the readers with a summary of the recent progress in the concerned domain and highlights the challenges associated with the synthesis and application of these multifunctional materials.

Bletilla striata Polysaccharide-/Chitosan-Based Self-Healing Hydrogel with Enhanced Photothermal Effect for Rapid Healing of Diabetic Infected Wounds via the Regulation of Microenvironment

The management of diabetic ulcers poses a significant challenge worldwide, and persistent hyperglycemia makes patients susceptible to bacterial infections. Unfortunately, the overuse of antibiotics may lead to drug resistance and prolonged infections, contributing to chronic inflammation and hindering the healing process. To address these issues, a photothermal therapy technique was incorporated in the preparation of wound dressings. This innovative solution involved the formulation of a self-healing and injectable hydrogel matrix based on the Schiff base structure formed between the oxidized Bletilla striata polysaccharide (BSP) and hydroxypropyltrimethylammonium chloride chitosan. Furthermore, the introduction of CuO nanoparticles encapsulated in polydopamine imparted excellent photothermal properties to the hydrogel, which promoted the release of berberine (BER) loaded on the nanoparticles and boosted the antibacterial performance. In addition to providing a reliable physical protection to the wound, the developed hydrogel, which integrated the herbal components of BSP and BER, effectively accelerated wound closure via microenvironment regulation, including alleviated inflammatory reaction, stimulated re-epithelialization, and reduced oxidative stress based on the promising results from cell and animal experiments. These impressive outcomes highlighted their clinical potential in safeguarding the wound against bacterial intrusion and managing diabetic ulcers.

Advancements in the synthesis of carbon dots and their application in biomedicine

As a sort of fluorescent carbon nanomaterial with a particle size of less than 10 nm, carbon dots (CDs) have their own merits of good dispersibility in water, stable optical properties, strong chemical inertness, stable optical properties, and good biosecurity. These excellent peculiarities facilitated them like sensing, imaging, medicine, catalysis, and optoelectronics, making them a new star in the field of nanotechnology. In particular, the development of CDs in the fields of chemical probes, imaging, cancer therapy, antibacterial and drug delivery has become a hot topic in current research. Although the biomedical applications in CDs have been demonstrated in many research articles, a systematic summary of their role in biomedical applications is scarce. In this review, we introduced the basic information of CDs in detail, including synthesis approaches of CDs as well as their favorable properties including photoluminescence and low cytotoxicity. Subsequently, the application of CDs in the field of biomedicine was emphasized. Finally, the main challenges and research prospects of CDs in this field were proposed, which might provide some detailed information in designing new CDs in this promising biomedical field.

Targeted delivery strategies: The interactions and applications of nanoparticles in liver diseases

In recent years, nanoparticles have been broadly utilized in various drugs delivery formulations. Nanodelivery systems have shown promise in solving problems associated with the distribution of hydrophobic drugs and have promoted the accumulation of nanomedicines in the circulation or in organs. However, the injection dose of nanoparticles (NPs) is much greater than that needed by diseased tissues or organs. In other words, most of the NPs are localized off-target and do not reach the desired tissue or organs. With the rapid development of biodegradable and biosafety nanomaterials, the nanovectors represent assurance of safety. However, the off-target effects also induce concerns about the application of NPs, especially in the delivery of gene editing tools. Therefore, a complete understanding of the biological responses to NPs in the body will clearly guide the design of targeted delivery of NPs. The different properties of various nanodelivery systems may induce diverse interactions between carriers and organs. In this review, we describe the relationship between the liver, the most influenced organ of systemic administration of NPs, and targeted delivery nanoplatforms. Various transport vehicles have adopted multiple delivery strategies for the targeted delivery to the cells in the homeostasis liver and in diseased liver. Additionally, nanodelivery systems provide a novel strategy for treating incurable diseases. The appearance of a targeted delivery has profoundly improved the application of NPs to liver diseases.

Nucleus-targeted carbon dots as peroxidase nanozyme for photoacoustic imaging and phototherapy of tumor

High-purity carbon dots (CDs) with a highly π-conjugated sp2-hybridized graphite structure were prepared by the pulse electrolysis method using the graphite plate as raw material. Photoacoustic signal together with photothermal effect was found in the CDs-dispersed suspensions under near-infrared (NIR) irradiation. For the suspension with the CDs concentration of 500 μg/mL, the photothermal conversion efficiency is high up 64.3% and the solution's temperature can be increased to 82.2 °C under NIR irradiation. Moreover, CDs can be effectively endocytosed by human hepatoma (HepG2) cells with a few hours, act as peroxidase nanozyme to decompose H2O2 and facilitate the production of reactive oxygen species. Under NIR irradiation, CDs exhibit an outstanding apoptosis-inducing effect on HepG2 cells by the photothermal effect. In addition, in vivo experiments show that CDs can be used in photoacoustic imaging (PAI) and guiding the tumor treatment. As a result, the nucleus-targeted CDs with an unique combination of PAI and photothermal effect have potential in cancer diagnosis and treatment.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Effect of PVP Molecular Weights on the Synthesis of Ultrasmall Cus Nanoflakes: Synthesis, Properties, and Potential Application for Phototheranostics

Copper sulfide nanoparticles (CuS) hold tremendous potential for applications in photothermal therapy (PTT) and photoacoustic imaging (PAI). However, the conventional chemical coprecipitation method often leads to particle agglomeration issues. To overcome this challenge, we utilized polyvinylpyrrolidone (PVP) as a stabilizing agent, resulting in the synthesis of small PVP-CuS nanoparticles named PC10, PCK30, and PC40. Our study aimed to investigate how different molecular weights of PVP influence the nanoparticles' crystalline characteristics and essential properties, especially their photoacoustic and photothermal responses. While prior research on PVP-assisted CuS nanoparticles has been conducted, our study delves deeper into this area, providing insights into optical properties. Remarkably, all synthesized nanoparticles exhibited a crystalline structure, were smaller than 10 nm, and featured an absorbance peak at 1020 nm, indicating their robust photoacoustic and photothermal capabilities. Among these nanoparticles, PC10 emerged as the standout performer, displaying superior photoacoustic properties. Our photothermal experiments demonstrated significant temperature increases in all cases, with PC10 achieving an impressive efficiency of 51%. Moreover, cytotoxicity assays revealed the nanoparticles' compatibility with cells, coupled with an enhanced incidence of apoptosis compared to necrosis. These findings underscore the promising potential of PVP-stabilized CuS nanoparticles for advanced cancer theranostics.

Facile synthesis of Gd/Ru-doped fluorescent carbon dots for fluorescent/MR bimodal imaging and tumor therapy

Functional metal doping endows fluorescent carbon dots with richer physical and chemical properties, greatly expanding their potential in the biomedical field. Nonetheless, fabricating carbon dots with integrated functionality for diagnostic and therapeutic modalities remains challenging. Herein, we develop a simple strategy to prepare Gd/Ru bimetallic doped fluorescent carbon dots (Gd/Ru-CDs) via a one-step microwave-assisted method with Ru(dcbpy)3Cl2, citric acid, polyethyleneimine, and GdCl3 as precursors. Multiple techniques were employed to characterize the morphology and properties of the obtained carbon dots. The Gd/Ru-CDs are high mono-dispersity, uniform spherical nanoparticles with an average diameter of 4.2 nm. Moreover, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) confirmed the composition and surface properties of the carbon dots. In particular, the successful doping of Gd/Ru enables the carbon dots not only show considerable magnetic resonance imaging (MRI) performance but also obtain better fluorescence (FL) properties, especially in the red emission area. More impressively, it has low cytotoxicity, excellent biocompatibility, and efficient reactive oxygen species (ROS) generation ability, making it an effective imaging-guided tumor treatment reagent. In vivo experiments have revealed that Gd/Ru-CDs can achieve light-induced tumor suppression and non-invasive fluorescence/magnetic resonance bimodal imaging reagents to monitor the treatment process of mouse tumor models. Thus, this simple and efficient carbon dot manufacturing strategy by doping functional metals has expanded avenues for the development and application of multifunctional all-in-one theranostics.

Green conversion of delignified sorghum straw and polyethylene glycol into form-stable phase change materials with promising solar energy capture, transition, and storage capabilities

Phase change materials (PCMs) have attracted considerable attention as a thermal energy management technology for thermal storage. However, achieving high energy-storing abilities, low leakage rates, and solar absorption abilities simultaneously in PCMs remains greatly challenging. This research proposed a green strategy for preparing sorghum straw-based PCMs. By facile delignification and solvothermal process, delignified sorghum straw (DSS) and carbon quantum dots (CQDs) derived from removal lignin are prepared. The obtained PEG@CQDs/DSS possessed considerable reusable stabilities, excellent photo-thermal conversion properties, and thermal energy management capacities due to the delicate micropores and intrinsic noncovalent interactions among components. Especially, the PEG@CQDs-7.5/DSS exhibited superior solar-thermal conversion capabilities (with conducive photo-thermal conversion efficiency ~90.84%), and kept stable after 100 cycles of heating and cooling, in which the melting enthalpy value is ~168.1 J/g (enthalpy efficiency of ~91.11%). In conclusion, the synthesized PCMs showed potential for application in energy-saving and building thermal management.

Hepatotoxicity evaluations of different surface charged carbon quantum dots in vivo and in vitro

Recently, carbon quantum dots (CQDs) have become popular because of their simple synthesis and potential applications. Although CQDs have high biocompatibility, their biotoxicity must be verified to reduce the possible risks associated with large-scale application. In this study, the hepatotoxicity of three CQD types, namely diammonium citrate (AC)-based (CQDs-AC), spermidine trihydrochloride (Spd)-based (CQDs-Spd), and AC- and Spd-based CQDs (CQDs-AC/Spd), were evaluated in vivo and in vitro. It was observed in vivo that CQDs-Spd and CQDs-AC/Spd, but not CQDs-AC, caused histopathological damage, including liver steatosis and mild mixed inflammatory cell infiltration; however, reduced liver function was only observed in CQD-Spd-treated mice. The in vitro results revealed that only CQDs-Spd significantly decreased the number of viable HepG2 cells (NADH depletion) and induced oxidative stress (heme oxygenase-1 activation) after 24 h of exposure, which promoted inflammatory factor secretion (NF-κB activation). Additionally, decreasing zonula occludens-2 and α1-antitrypsin protein expression in HepG2 cells suggested that CQD-Spd exposure increases the risk of liver diseases. Our results revealed that CQDs-Spd had greater hepatotoxic potential than CQDs-AC and CQDs-AC/Spd, which might be attributable to their high positive surface charge. Overall, the risk of CQD-induced hepatotoxic risk must be considered when applying positively charged CQDs.

Carbon quantum dots in bioimaging and biomedicines

Carbon quantum dots (CQDs) are gaining a lot more attention than traditional semiconductor quantum dots owing to their intrinsic fluorescence property, chemical inertness, biocompatibility, non-toxicity, and simple and inexpensive synthetic route of preparation. These properties allow CQDs to be utilized for a broad range of applications in various fields of scientific research including biomedical sciences, particularly in bioimaging and biomedicines. CQDs are a promising choice for advanced nanomaterials research for bioimaging and biomedicines owing to their unique chemical, physical, and optical properties. CQDs doped with hetero atom, or polymer composite materials are extremely advantageous for biochemical, biological, and biomedical applications since they are easy to prepare, biocompatible, and have beneficial properties. This type of CQD is highly useful in phototherapy, gene therapy, medication delivery, and bioimaging. This review explores the applications of CQDs in bioimaging and biomedicine, highlighting recent advancements and future possibilities to increase interest in their numerous advantages for therapeutic applications.

Molecular and cellular imaging of the eye

The application of molecular and cellular imaging in ophthalmology has numerous benefits. It can enable the early detection and diagnosis of ocular diseases, facilitating timely intervention and improved patient outcomes. Molecular imaging techniques can help identify disease biomarkers, monitor disease progression, and evaluate treatment responses. Furthermore, these techniques allow researchers to gain insights into the pathogenesis of ocular diseases and develop novel therapeutic strategies. Molecular and cellular imaging can also allow basic research to elucidate the normal physiological processes occurring within the eye, such as cell signaling, tissue remodeling, and immune responses. By providing detailed visualization at the molecular and cellular level, these imaging techniques contribute to a comprehensive understanding of ocular biology. Current clinically available imaging often relies on confocal microscopy, multi-photon microscopy, PET (positron emission tomography) or SPECT (single-photon emission computed tomography) techniques, optical coherence tomography (OCT), and fluorescence imaging. Preclinical research focuses on the identification of novel molecular targets for various diseases. The aim is to discover specific biomarkers or molecular pathways associated with diseases, allowing for targeted imaging and precise disease characterization. In parallel, efforts are being made to develop sophisticated and multifunctional contrast agents that can selectively bind to these identified molecular targets. These contrast agents can enhance the imaging signal and improve the sensitivity and specificity of molecular imaging by carrying various imaging labels, including radionuclides for PET or SPECT, fluorescent dyes for optical imaging, or nanoparticles for multimodal imaging. Furthermore, advancements in technology and instrumentation are being pursued to enable multimodality molecular imaging. Integrating different imaging modalities, such as PET/MRI (magnetic resonance imaging) or PET/CT (computed tomography), allows for the complementary strengths of each modality to be combined, providing comprehensive molecular and anatomical information in a single examination. Recently, photoacoustic microscopy (PAM) has been explored as a novel imaging technology for visualization of different retinal diseases. PAM is a non-invasive, non-ionizing radiation, and hybrid imaging modality that combines the optical excitation of contrast agents with ultrasound detection. It offers a unique approach to imaging by providing both anatomical and functional information. Its ability to utilize molecularly targeted contrast agents holds great promise for molecular imaging applications in ophthalmology. In this review, we will summarize the application of multimodality molecular imaging for tracking chorioretinal angiogenesis along with the migration of stem cells after subretinal transplantation in vivo.

Fabrication and characterization of microwave-assisted synthesis of carbon dots crosslinked sodium alginate hydrogel films

In this study, potassium-incorporated carbon dots (K-CDs) and nitrogen-incorporated carbon dots (N-CDs) were composted using the microwave-assisted method, in which the carbon source is citric acid. Subsequently, the prepared CDs were added into sodium alginate (NaAlg)/CaCO3 to form a hydrogel film. The Ca2+ in the system is tend to be released in the presence of acidic CDs to promote the cross-linking of NaAlg. This study presents a NaAlg hydrogel film preparation process that requires no additional acid and is natural and environmentally friendly. Moreover, it gives the NaAlg hydrogel film excellent antioxidant and antimicrobial properties and also improves its mechanical properties and gel strength. The release behaviors of the CDs in the hydrogel films were also explored. The prepared CD-incorporated NaAlg hydrogel films have potential applications in medical, biological engineering, food preservation, and other fields owing to their functional properties.

Synthesis of Yellow Fluorescence Carbon Dots for the Applications of Vitamin B12 Detection and Cell Imaging

In this work, bright yellow fluorescent and multifunctional carbon dots (N-CDs) were prepared by hydrothermal method from O-phenylenediamine and 4-aminobenzoic acid. The fluorescence characterization showed that the N-CDs possessed good optical properties (QY = 32%) and excitation dependent multi-color emission. By exciting with 390 nm, the strong selective interaction of VB12 with N-CDs could result in a sharp decrease in the luminescence of N-CDs at 567 nm. An efficient fluorescence sensor in aqueous solution was constructed which could linearly respond VB12 in wide concentration ranges of 0-90 μM and 140-250 μM. The linear correlation coefficients of N-CDs and VB12 were 0.9950 and 0.9968, respectively, and the detection limit was 0.119 μM. N-CDs were performed for sensitive determination of VB12 in real samples. Moreover, the N-CDs were exploited to image cell. This N-CDs was a sensitive fluorescence probe to monitor VB12 and presented prospective potential in living cells imaging. Schematic diagram of the synthesis process and application research of N-CDs.

Functionalized heteroatom-doped carbon dots for biomedical applications: A review

Carbon nanoparticles (CDs) have recently drawn a great attention in (bio)chemical analysis, sensing and bioimaging owing to their photostability, water stability, minimal toxicity, biocompatibility and ease of surface functionalization. While the vast majority of CDs applications rely on exploiting their fluorescent properties, doping such nanomaterials with various elements has recently received increasing attention as an effective approach to modify their optoelectronic characteristics, introducing novel improved optical features such as phosphorescence, upconversion luminescence or multimodal imaging capabilities. This review article focuses in the recent advances on the synthesis of heteroatom-doped CDs, exhibiting distinctive features of high value for sensing and imaging, as well as various functionalization schemes developed for guided analyte labeling. Relevant applications in chemical sensing, bioimaging and disease therapy are here presented. A final section intends to provide an overview towards future developments of such emerging light-emitting nanomaterials in the design of future devices and strategies for (bio)analytical chemistry.

Impact of carbon quantum dots on self-assembly and dielectric relaxation modes of a room temperature tri-component fluorinated antiferroelectric liquid crystal mixture

We investigated the impact of carbon quantum dots (CQDs) of sizes ∼2-5 nm in a room temperature tri-component fluorinated antiferroelectric liquid crystal (AFLC) mixture. The synthesised CQDs have been characterised by high-resolution transmission electron microscopy and X-ray diffraction spectroscopy. An increase in the transition temperature and enthalpy to the isotropic liquid phase indicates stabilization of the AFLC mixture in the presence of CQDs. The dielectric studies have been carried out in the frequency range of 1 Hz-40 MHz under the planar anchoring conditions of the molecules. An appreciable increase in the permittivity, dielectric strength, and conductivity has been observed owing to the existence of sp2/sp3 hybridization in the CQDs which form a strong coupling and develop a dipolar ordering in the systems. Various relaxation frequencies were increased with the incarceration of CQDs in the AFLC mixture. Overall, the different studies suggest that the doped CQDs are very well settled in between the host molecules without disturbing the molecular ordering of the hosts. Such results are encouraging and reveal the potential applicability of the CQD doped systems to produce highly efficient tuneable optical devices and other multifaceted applications.

Photothermal Carbon Dots Chelated Hydroxyapatite Filler: High Photothermal Conversion Efficiency and Enhancing Adhesion of Hydrogel

The synthesis of photothermal carbon/hydroxyapatite composites poses challenges due to the binding modes and relatively low photothermal conversion efficiency. To address these challenges, the calcium ions chelated by photothermal carbon dots (PTC-CDs) served as the calcium source for the synthesis of photothermal carbon dots chelated hydroxyapatite (PTC-HA) filler via the coprecipitation method. The coordination constant K and chelation sites of PTC-HA were 7.20 × 102 and 1.61, respectively. Compared to PTC-CDs, the coordination constant K and chelation sites of PTC-HA decreased by 88 and 35% due to chelating to hydroxyapatite, respectively. PTC-HA possesses fluorescence and photothermal performance with a 62.4% photothermal conversion efficiency. The incorporation of PTC-HA filler significantly enhances as high as 76% the adhesion performance of the adhesive hydrogel. PTC-HA with high photothermal conversion efficiency and enhancing adhesion performance holds promise for applications in high photothermal conversion efficiency, offering tissue adhesive properties and fluorescence capabilities to the hydrogel.

Cell-Derived N/P/S-Codoped Fluorescent Carbon Nanodots with Intrinsic Targeting Ability for Tumor-Specific Phototheranostics

Combining targeting ability, imaging function, and photothermal/photodynamic therapy into a single agent is highly desired for cancer theranostics. Herein, we developed a one-for-all nanoplatform with N/P/S-codoped fluorescent carbon nanodots (CNDs) for tumor-specific phototheranostics. The CNDs were prepared via a one-pot hydrothermal process using cancer cells as sources of carbon, nitrogen, phosphorus, and sulfur. The obtained N/P/S-codoped CNDs exhibit wide light absorption in the range of 200-900 nm and excitation-dependent emission with high photostability. Importantly, the cancer cell-derived N/P/S-codoped CNDs have outstanding biocompatibility and naturally intrinsic targeted ability for cancer cells as well as dual photothermal/photodynamic effects under 795 nm laser irradiation. Moreover, the photothermal conversion efficiency and singlet oxygen (1O2) generation efficiency were calculated to be 52 and 34%, respectively. These exceptional properties enable CNDs to act as fine theranostic agents for targeted imaging and photothermal-photodynamic synergistic therapy within the NIR therapeutic window. The CNDs prepared in this work are promising for construction as a universal tumor phototheranostic platform.

Functionalized Fe-Doped Carbon Dots Exhibiting Dual Glutathione Consumption to Amplify Ferroptosis for Enhanced Cancer Therapy

Nonapoptotic ferroptosis is a promising cancer treatment which offers a solution to the multidrug resistance of conventional apoptosis-induced programmed cancer cell death therapies. Reducing intracellular glutathione (GSH) is essential for inducing excess ROS and has been considered a crucial process to trigger ferroptosis. However, treatments reducing GSH alone have not produced satisfactory effects due to their restricted target. In this regard, FeCDs (Fe3+-modified l-histidine -sourced carbon dots) with dual GSH-consumption capabilities were constructed to engineer ferroptosis by self-amplifying intratumoral oxidative stress. Carbon dots have the ability to consume GSH, and the introduction of Fe3+ can amplify the GSH-consuming ability of CDs, reacting with excess H2O2 in the tumor microenvironment to generate highly oxidized •OH. This is a novel strategy through synergistic self-amplification therapy combining Fe3+ and CDs with GSH-consuming activity. The acid-triggered degradation material (FeCDs@PAE-PEG) was prepared by encapsulating FeCDs in an oil-in-water manner. Compared with other ferroptosis-triggering nanoparticles, the established FeCDs@PAE-PEG is targeted and significantly enhances the consumption efficiency of GSH and accumulation of excess iron without the involvement of infrared light and ultrasound. This synergistic strategy exhibits excellent ferroptosis-inducing ability and antitumor efficacy both in vitro and in vivo and offers great potential for clinical translation of ferroptosis.

Lignocellulosic Biomass-Based Carbon Dots: Synthesis Processes, Properties, and Applications

Carbon dots (CDs), a new type of carbon-based fluorescent nanomaterial, have attracted widespread attention because of their numerous excellent properties. Lignocellulosic biomass is the most abundant renewable natural resource and possesses broad potential to manufacture different composite and smart materials. Numerous studies have explored the potential of using the components (such as cellulose, hemicellulose, and lignin) in lignocellulosic biomass to produce CDs. There are few papers systemically aiming in the review of the state-of-the-art works related to lignocellulosic biomass-derived CDs. In this review, the significant advances in synthesis processes, formation mechanisms, structural characteristics, optical properties, and applications of lignocellulosic biomass-based CDs such as cellulose-based CDs, hemicellulose-based CDs and lignin-based CDs in latest research are reviewed. In addition, future research directions on the improvement of the synthesis technology of CDs using lignocellulosic biomass as raw materials to enhance the properties of CDs are proposed. This review will serve as a road map for scientists engaged in research and exploring more applications of CDs in different science fields to achieve the highest material performance goals of CDs.

Polyphenolic Carbon Quantum Dots with Intrinsic Reactive Oxygen Species Amplification for Two-Photon Bioimaging and In Vivo Tumor Therapy

Recent studies indicate that mitochondrial dysfunctions and DNA damage have a critical influence on cell survival, which is considered one of the therapeutic targets for cancer therapy. In this study, we demonstrated a comparative study of the effect of polyphenolic carbon quantum dots (CQDs) on in vitro and in vivo antitumor efficacy. Dual emissive (green and yellow) shape specific polyphenolic CQDs (G-CQDs and Y-CQDs) were synthesized from easily available nontoxic precursors (phloroglucinol), and the antitumor property of the as-synthesized probe was investigated as compared to round-shaped blue emissive CQDs (B-CQDs) derived from well-reported precursor citric acid and urea. The B-CQDs had a nuclei-targeting property, and G-CQDs and Y-CQDs had mitochondria-targeting properties. We have found that the polyphenol containing CQDs (at a dose of 100 μg mL-1) specifically attack mitochondria by excess accumulation, altering the metabolism, inhibiting branching pattern, imbalanced Bax/Bcl-2 homeostasis, and ultimately generating oxidative stress levels, leading to oxidative stress-induced cell death in cancer cells in vitro. We show that G-CQDs are the main cause of oxidative stress in cancer cells because of their ability to produce sufficient •OH- and 1O2 radicals, evidenced by electron paramagnetic resonance spectroscopy and a terephthalic acid test. Moreover, the near-infrared absorption properties of the CQDs were exhibited in two-photon (TP) emission, which was utilized for TP cellular imaging of cancer cells without photobleaching. The in vivo antitumor test further discloses that intratumoral injection of G-CQDs can significantly augment the treatment efficacy of subcutaneous tumors without any adverse effects on BalB/c nude mice. We believe that shape-specific polyphenolic CQD-based nanotheranostic agents have a potential role in tumor therapy, thus proving an insight on treatment of malignant cancers.

Comprehensive advances in the synthesis, fluorescence mechanism and multifunctional applications of red-emitting carbon nanomaterials

Red emitting fluorescent carbon nanomaterials have drawn significant scientific interest in recent years due to their high quantum yield, water-dispersibility, photostability, biocompatibility, ease of surface functionalization, low cost and eco-friendliness. The red emissive characteristics of fluorescent carbon nanomaterials generally depend on the carbon source, reaction time, synthetic approach/methodology, surface functional groups, average size, and other reaction environments, which directly or indirectly help to achieve red emission. The importance of several factors to achieve red fluorescent carbon nanomaterials is highlighted in this review. Numerous plausible theories have been explained in detail to understand the origin of red fluorescence and tunable emission in these carbon-based nanostructures. The above advantages and fluorescence in the red region make them a potential candidate for multifunctional applications in various current fields. Therefore, this review focused on the recent advances in the synthesis approach, mechanism of fluorescence, and electronic and optical properties of red-emitting fluorescent carbon nanomaterials. This review also explains the several innovative applications of red-emitting fluorescent carbon nanomaterials such as biomedicine, light-emitting devices, sensing, photocatalysis, energy, anticounterfeiting, fluorescent silk, artificial photosynthesis, etc. It is hoped that by choosing appropriate methods, the present review can inspire and guide future research on the design of red emissive fluorescent carbon nanomaterials for potential advancements in multifunctional applications.

One-Pot, Optimized Microwave-Assisted Synthesis of Difunctionalized and B-N Co-Doped Carbon Dots: Structural Characterization

In this work, we employed a novel microwave-assisted synthesis method to produce nitrogen and boron co-doped carbon dots (B-N co-doped CDs). To achieve optimal synthesis, we conducted a comprehensive parameter modulation approach, combining various synthesis temperatures, times, and precursor concentrations, while keeping the power constant at 150 W and pH 5. Using maximum fluorescence emission as our response variable, the best conditions were identified as 120 °C, 3 min, and a precursor concentration of 1 mg/mL. Characterization using field emission scanning electron microscopy revealed these CDs to have a spherical morphology with an average size of 10.9 ± 3.38 nm. Further high-resolution transmission electron microscopy showed an interplanar distance of 0.23 nm, which is in line with prior findings of CDs that present a 0.21 nm distance corresponding to the (100) plane of graphite. Optical properties were ascertained through UV-vis absorption, identifying distinct π-π* and n-π* transitions. Fluorescence spectroscopy highlighted an emission peak at 375 nm when excited at 295 nm, achieving a quantum yield of 56.7%. Fourier-transform infrared spectroscopy and Raman spectroscopy analyses confirmed the boronic acid and amine groups' presence, underscoring the graphitic nature of the core and the co-doping of boron and nitrogen. These empirical observations were compared with theoretical investigations through simulated Raman spectra, proposing a potential structure for the CDs. X-ray photoelectron spectroscopy further endorsed the co-doping of nitrogen and boron, along with the detection of the specified functional groups. All these characteristics could lend this nanomaterial to different types of applications such as fluorescent probes for a broad range of analytes and for fluorescent cell imaging.

Photothermal performance of a novel carbon dot and its conjugate with disulfiram for prostate cancer PC3 cell therapy

Aim: To develop and employ a copper, sulfur, nitrogen-carbon quantum dot (C,S,N-CQD) multifunctional platform for synergistic cancer therapy, combining chemotherapy and photothermal treatment with in vitro cancer cell imaging. Materials & methods: Cu,S,N-CQDs were synthesized hydrothermally, loaded with disulfiram (DSF), and characterized through UV-Vis spectrophotometry, photoluminescence, Fourier-transform infrared spectroscopy, high-resolution transmission electron microscopy, dynamic light scattering, x-ray diffraction and EDAX. Results: Cu,S,N-CQD exhibited 5.5% absolute fluorescence quantum yield, 46.0% photothermal conversion efficiency and excellent stability. The release of DSF-loaded Cu,S,N-CQD, photothermal performance, and IC50 on PC3 prostate cancer cells, were evaluated. The impact of cellular glutathione on nanocarrier performance was investigated. Conclusion: Cu,S,N-CQD as a photothermal agent and DSF carrier showed synergy (combination index: 0.71) between chemotherapy and photothermal therapy. The nanocarrier simultaneously employed for in vitro cancer cell imaging due to its unique fluorescence properties.

Luminescence of carbon quantum dots and their application in biochemistry

Similar to fullerenes, carbon nanotubes and graphene, carbon dots (CDs) are causing a lot of research work in their own right. CDs are a type of surface-passivated quantum dot that contain carbon atoms. Their distinctive characteristics, such as luminescent emission that varies with size and wavelength, resistance to photobleaching, easy biological binding, lack of toxicity, and economical production without the need for intricate synthetic processes, have led to a noteworthy surge in attention within the research community. Different techniques can be utilized to create these CDs, spanning from basic candle burning to laser ablation. This review article delves into the principles of fluorescence technology, providing insights into how different synthesis methods of quantum dots impact their luminescent properties. Additionally, it highlights the latest applications of quantum dots in catalysis and biomedical fields, with special emphasis on the current status of luminescent properties in biology and chemistry. Towards the end, the article discusses the limitations of quantum dots in current practical applications, pointing out that CDs hold promising potential for future applications.

Multicolor Photoluminescent Carbon Dots à La Carte for Biomedical Applications

Dual-emission fluorescence probes that provide high sensitivity are key for biomedical diagnostic applications. Nontoxic carbon dots (CDs) are an emerging alternative to traditional fluorescent probes; however, robust and reproducible synthetic strategies are still needed to access materials with controlled emission profiles and improved fluorescence quantum yields (FQYs). Herein, we report a practical and general synthetic strategy to access dual-emission CDs with FQYs as high as 0.67 and green/blue, yellow/blue, or red/blue excitation-dependent emission profiles using common starting materials such as citric acid, cysteine, and co-dopants to bias the synthetic pathway. Structural and physicochemical analysis using nuclear magnetic resonance, absorbance and fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy in addition to transmission electron and atomic force microscopy (TEM and AFM) is used to elucidate the material's composition which is responsible for the unique observed photoluminescence properties. Moreover, the utility of the probes is demonstrated in the clinical setting by the synthesis of green/blue emitting antibody-CD conjugates which are used for the immunohistochemical staining of human brain tissues of glioblastoma patients, showing detection under two different emission channels.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Red emissive carbon dots: a promising next-generation material with intracellular applicability

The accidental discovery of carbon dots (CDs) back in 2004 has led to their widespread use in the biomedical field. CDs have demonstrated their effectiveness in reporting 3D structures of biological specimens, identifying normal and cancer cells, and even detecting analytes within cells. However, the limitations of blue-green emitting CDs, such as their shallow penetration, photodamage, and auto-fluorescence, have hindered their practical applications. To overcome these limitations, red emissive CDs (RCDs) have been developed, which have deep tissue penetration, minimal photo-damage, low auto-fluorescence, and high imaging contrast. In this article, we present a thorough review on the use of RCDs in biomedical applications, including in vivo and in vitro bioimaging, photoacoustic imaging, monitoring temperature and polarity changes in living cells, tumour therapy, and drug delivery. With the rapid progress being made in the development of RCDs for intracellular applications, their clinical application is expected to become a reality in the near future.

Bifunctional Cascading Nanozymes Based on Carbon Dots Promotes Photodynamic Therapy by Regulating Hypoxia and Glycolysis

Photodynamic therapy (PDT) still faces great challenges with suitable photosensitizers, oxygen supply, and reactive oxygen species (ROS) accumulation, especially in the tumor microenvironment, feathering hypoxia, and high glucose metabolism. Herein, a carbon dots (CDs)-based bifunctional nanosystem (MnZ@Au), acting as photosensitizer and nanozyme with cascading glucose oxidase (GOx)- and catalase (CAT)-like reactivity, was developed for improving hypoxia and regulating glucose metabolism to enhance PDT. The MnZ@Au was constructed using Mn-doped CDs (Mn-CDs) as a core and zeolitic imidazolate framework-8 (ZIF-8) as a shell to form a hybrid (MnZ), followed by anchoring ultrasmall Au nanoparticles (AuNPs) onto the surface of MnZ through the ion exchange and in situ reduction methods. MnZ@Au catalyzed glucose consumption and oxygen generation by cascading GOx- and CAT-like nanozyme reactions, which was further enhanced by its own photothermal properties. In vitro and in vivo studies also confirmed that MnZ@Au greatly improved CDs penetration, promoted ROS accumulation, and enhanced PDT efficacy, leading to efficient tumor growth inhibition in the breast tumor model. Besides, MnZ@Au enabled photoacoustic (PA) imaging to provide a mapping of Mn-CDs distribution and oxygen saturation, showing the real-time catalytic process of MnZ@Au in vivo. 18F-Fluorodeoxyglucose positron emission tomography (18F-FDG PET) imaging also validated the decreased glucose uptake in tumors treated by MnZ@Au. Therefore, the integrated design provided a promising strategy to utilize and regulate the tumor microenvironment, promote penetration, enhance PDT, and finally prevent tumor deterioration.

Research progress on carbon materials in tumor photothermal therapy

At present, cancer remains one of the leading causes of human death worldwide, and surgery, radiotherapy and chemotherapy are still the main methods of cancer treatment. However, these treatments have their drawbacks. Surgical treatment often struggles with the complete removal of tumor tissue, leading to a high risk of cancer recurrence. Additionally, chemotherapy drugs have a significant impact on overall health and can easily result in drug resistance. The high risk and mortality of cancer and other reasons promote scientific researchers to unremittingly develop and find a more accurate and faster diagnosis strategy and effective cancer treatment method. Photothermal therapy, which utilizes near-infrared light, offers deeper tissue penetration and minimal damage to surrounding healthy tissues. Compared to conventional radiotherapy and other treatment methods, photothermal therapy boasts several advantages, including high efficiency, non-invasiveness, simplicity, minimal toxicity, and fewer side effects. Photothermal nanomaterials can be categorized as either organic or inorganic materials. This review primarily focuses on the behavior of carbon materials as inorganic materials and their role in tumor photothermal treatment. Furthermore, the challenges faced by carbon materials in photothermal treatment are discussed.

Ultra-Narrow-Bandwidth Deep-Red Electroluminescence Based on Green Plant-Derived Carbon Dots

Deep-red light-emitting diodes (DR-LEDs, >660 nm) with high color-purity and narrow-bandwidth emission are promising for full-color displays and solid-state lighting applications. Currently, the DR-LEDs are mainly based on conventional emitters such as organic materials and heavy-metal based quantum dots (QDs) and perovskites. However, the organic materials always suffer from the complicated synthesis, inferior color purity with full-width at half-maximum (FWHM) more than 40 nm, and the QDs and perovskites still suffer from serious problems related to toxicity. Herein, this work reports the synthesis of efficient and high color-purity deep-red carbon dots (CDs) with a record narrow FWHM of 21 nm and a high quantum yield of more than 50% from readily available green plants. Moreover, an exciplex host is further established using a polymer and small molecular blend, which has been shown to be an efficient strategy for producing high color-purity monochrome emission from deep-red CDs via Förster energy transfer (FET). The deep-red CD-LEDs display high color-purity with Commission Internationale de l'Eclairage (CIE) coordinates of (0.692, 0.307). To the best of the knowledge, this is the first report of high color-purity CD-LEDs in the deep-red region, opening the door for the application of CDs in the development of high-resolution light-emitting display technologies.

Immunotherapeutic effect of photothermal-mediated exosomes secreted from breast cancer cells

Aim: Exosomal damage-associated molecular patterns can play a key role in immunostimulation and changing the cold tumor microenvironment to hot. Materials & methods: This study examined the immunostimulation effect of photothermal and hyperthermia-treated 4T1 cell-derived exosomes on 4T1 cell-induced breast tumors in BALB/c animal models. Exosomes were characterized for HSP70, HSP90 and HMGB-1 before injection into mice and tumor tissues were analyzed for IL-6, IL-12 and IL-1β, CD4 and CD8 T-cell permeability, and PD-L1 expression. Results: Thermal treatments increased high damage-associated molecular patterns containing exosome secretion and the permeability of T cells to tumors, leading to tumor growth inhibition. Conclusion: Photothermal-derived exosomes showed higher damage-associated molecular patterns than hyperthermia with a higher immunostimulation and inhibiting tumor growth effect.

Red emitting carbon dots: surface modifications and bioapplications

Quantum dots (QDs), and carbon quantum dots (CDs) in particular, have received significant attention for their special characteristics. These particles, on the scale of several nanometers, are often produced using simple and green methods, with naturally occurring organic precursors. In addition to facile production methods, CDs present advantageous applications in the field of medicine, primarily for bioimaging, antibacterial and therapeutics. Also, CDs present great potential for surface modification through methods like doping or material mixing during synthesis. However, the bulk of current literature focuses on CDs emitting in the blue wavelengths which are not very suitable for biological applications. Red emitting CDs are therefore of additional interest due to their brightness, photostability, novelty and deeper tissue penetration. In this review article, red CDs, their methods of production, and their biological applications for translational research are explored in depth, with emphasis on the effects of surface modifications and doping.

A double rare earth doped CD nanoplatform for nanocatalytic/starving-like synergistic therapy with GSH-depletion and enhanced reactive oxygen species generation

Cancer has been one of the principal diseases threatening human health in the world. Traditional chemotherapy, radiotherapy and surgery in clinical applications have some disadvantages, such as inefficiency, low specificity, and serious side effects. Therefore, some emerging synergistic therapies have been developed for more accurate diagnosis and more efficient treatment of cancer. Herein, novel Ce-Gd@CDs-GOx nanozymes were obtained by combining magnetic resonance/fluorescence (MR/FL) imaging and nanocatalytic/starving-like synergistic therapy for tumor tissue imaging and efficient cancer treatment. The as-prepared Ce-Gd@CDs-GOx nanozymes with a diameter of 25.0 ± 0.8 nm exhibited favorable physiological stability, negligible toxicity, bright fluorescence and strong T1-weighted MR imaging (MRI) performance (10.97 mM-1 s-1). Moreover, the nanozymes could not only cut off the nutrient supply of tumor cells, but also generate ROS to synergistically enhance antitumor efficacy. The coexistence of Ce3+/Ce4+ in Ce-Gd@CDs-GOx endowed them with attractive capacity for alleviating hypoxia and enhancing GSH consumption to induce the apoptosis of tumor cells. Furthermore, most of the 4T1 cells treated with Ce-Gd@CDs-GOx nanozymes were damaged in the CCK-8 and Calcein-AM/PI staining assays, indicating the excellent efficiency of intracellular synergistic therapy. In summary, this study offered a promising strategy to design a nanoplatform for MR/FL imaging-guided nanocatalytic and starvation-like synergistic therapy of cancer.

Bioorthogonal Glycoengineering-Mediated Multifunctional Liquid Metal Nanoprobes for Highly Efficient Photoacoustic Imaging-Guided Photothermal/Chemotherapy of Tumor

The development of a multifunctional cancer diagnosis and treatment platform offers excellent prospects for the effective eradication of malignant solid tumors. Herein, a doxorubicin hydrochloride (DOX)-loaded tannic acid (TA)-coated liquid metal (LM) multifunctional nanoprobe was synthesized and applied as a highly efficient platform for the photoacoustic (PA) imaging-guided photothermal/chemotherapy of tumor. The multifunctional nanoprobes exhibited strong near-infrared absorption, a remarkable photothermal conversion efficiency (PCE) of 55%, and high DOX loading capacity. Combined with the large intrinsic thermal expansion coefficient of LM, highly efficient PA imaging and effective drug release were realized. The LM-based multifunctional nanoprobes were specifically adsorbed into the cancer cells and tumor tissues via glycoengineering biorthogonal chemistry. The in vitro and in vivo photothermal/chemo-anticancer activity confirmed their promising potential in cancer treatment. The subcutaneous breast tumor-bearing mice completely recovered in 5 days under light illumination with clear PA imaging presentation, which showed better antitumor outcomes than single-mode chemotherapy or photothermal therapy (PTT), while keeping side effects at a minimum. Such an LM-based PA imaging-guided photothermal/chemotherapy strategy provided a valuable platform for resistant cancer precise treatment and intelligent biomedicine.

NIR-II Nanoprobes: A Review of Components-Based Approaches to Next-Generation Bioimaging Probes

Fluorescence and photoacoustic imaging techniques offer valuable insights into cell- and tissue-level processes. However, these optical imaging modalities are limited by scattering and absorption in tissue, resulting in the low-depth penetration of imaging. Contrast-enhanced imaging in the near-infrared window improves imaging penetration by taking advantage of reduced autofluorescence and scattering effects. Current contrast agents for fluorescence and photoacoustic imaging face several limitations from photostability and targeting specificity, highlighting the need for a novel imaging probe development. This review covers a broad range of near-infrared fluorescent and photoacoustic contrast agents, including organic dyes, polymers, and metallic nanostructures, focusing on their optical properties and applications in cellular and animal imaging. Similarly, we explore encapsulation and functionalization technologies toward building targeted, nanoscale imaging probes. Bioimaging applications such as angiography, tumor imaging, and the tracking of specific cell types are discussed. This review sheds light on recent advancements in fluorescent and photoacoustic nanoprobes in the near-infrared window. It serves as a valuable resource for researchers working in fields of biomedical imaging and nanotechnology, facilitating the development of innovative nanoprobes for improved diagnostic approaches in preclinical healthcare.

Nitrogen and bromine co-doped carbon dots with red fluorescence for sensing of Ag+ and visual monitoring of glutathione in cells

Carbon dots (CDs) with red fluorescence emission have excellent advantages in cell imaging. Herein, novel nitrogen and bromine doped CDs (N,Br-CDs) were prepared with 4-bromo-1,2-phenylenediamine as precursor. The N, Br-CDs present the optimal emission wavelength at 582 nm (λ_ex = 510 nm) at pH 7.0 and 648 nm (λ_ex = 580 nm) at pH 3.0 ∼ 5.0, respectively. The fluorescence intensity of N,Br-CDs at 648 nm versus Ag⁺ concentration shows a good relationship from 0 to 60 μM with the limit of detection (LOD) of 0.14 μM. Furthermore, the fluorescence of N,Br-CDs/Ag⁺ is efficiently restored via the combination of glutathione (GSH) and Ag⁺ and linearly changes with GSH concentration from 0 ∼ 6.0 μM with LOD of 49 nM. This method has been successfully employed to monitor intracellular Ag⁺ and GSH with fluorescence imaging. The results suggest that the N,Br-CDs has application potential in the sensing of Ag⁺ and visual monitoring of GSH in cells.

Curcumin-Triterpene Type Hybrid as Effective Sonosensitizers for Sonodynamic Therapy in Oral Squamous Cell Carcinoma

Sonodynamic therapy (SDT) is a non-invasive therapeutic modality in cancer treatment that combines low-intensity ultrasound (US) and sonosensitizers. Tumor cells are destroyed through the synergistic effects of ultrasound and a chemical sonosensitizer. This study focused on the synthesis and in vitro evaluation of the sonodynamic effect of natural curcumin, triterpene oleanolic acid, and their semi-synthetic derivatives on tongue cancer SCC-25 and hypopharyngeal FaDu cell lines. The combination of the tested compounds with sonication showed a synergistic increase in cytotoxicity. In the group of oleanolic acid derivatives, oleanoyl hydrogen succinate (6) showed the strongest cytotoxic effect both in the SCC-25 and FaDu cell lines. Comparing curcumin (4) and its pyrazole derivative (5), curcumin showed a better cytotoxic effect on SCC-25 cells, while curcumin pyrazole was more potent on FaDu cells. The highest sonotherapeutic activity, compared to its individual components, was demonstrated by a structural linker mode hybrid containing both curcumin pyrazole-oleanoyl hydrogen succinate units within one complex molecule (7). This study can be beneficial in the context of new perspectives in the search for effective sonosensitizers among derivatives of natural organic compounds.

Preparation of Multicolor Fluorescent Carbon Dots Based on Catechol and o-Phthalaldehyde

As the foremost category of carbon materials, carbon dots (CDs) have been extensively applied in many domains because of their special fluorescence features and outstanding biocompatibility. However, in early studies of fluorescent CDs, as the fluorescence wavelength of most CDs was restricted to the blue or green region and was excitation dependent, the application of CDs was limited. In this study, three representative CDs, fluorescing yellow, green, and blue, were synthesized under alkaline, neutral, and acidic circumstances, respectively, while using a hydrothermal method in which catechol and phthalaldehyde acted as carbon sources and methanol functioned as the reaction solvent. The carbon nuclei of the three fluorescent CDs all had comparable graphite structures. The diversity of photoluminescence (PL) emission from these three CDs was attributed mainly to the different sizes of the sp² conjugated structures among them. Mixing synthesized CDs with epoxy resin, three colors (yellow, green, and blue) of LED using CIE coordinates (0.40, 0.44), (0.33, 0.46), and (0.21, 0.22), respectively, were successfully prepared.

Eco-friendly cellulose-based hydrogel functionalized by NIR-responsive multimodal antibacterial polymeric ionic liquid as platform for promoting wound healing

With the trend of sustainable development and the complex medical environment, there is a strong demand for multimodal antibacterial cellulose wound dressing (MACD) with photothermal therapy (PTT). Herein, a novel MACD fabrication strategy with PTT was proposed and implemented through graft polymerization of an imidazolium ionic liquid monomer containing iron complex anion structure. The fabricated hydrogels exhibited excellent antibacterial properties because of the efficient photothermal conversion ability (68.67 %) of ionic liquids and the intrinsic structural characteristic of quaternary ammonium salts. The antibacterial ratio of cellulosic hydrogel dressings to S. aureus and E. coli could reach 99.57 % and 99.16 %, respectively. Additionally, the fabricated hydrogels demonstrated extremely low hemolysis rates (<5 %) and excellent cell viability (~>85 %). Furthermore, in vivo antibacterial experimental results proved that the fabricated antibacterial dressings could significantly accelerate wound healing. Therefore, the proposed strategy would provide a new method of designing and preparing high-performance cellulose wound dressings.

Dual-Emissive Carbon Dots: Exploring Their Fluorescence Properties for Sensitive Turn-Off-On Recognition of Ferric and Pyrophosphate Ions and Its Application in Fluorometric Detection of the Loop-Mediated Isothermal Amplification Reaction

In this study, dual-emissive carbon dots (CDs) were prepared using p-phenylenediamine (pPDA) and phytic acid (PA) precursors via a one-pot-hydrothermal method. The photophysical, morphological, and structural characterization of CDs was carried out using absorption, fluorescence, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), and high-resolution transmission electron microscopy (HR-TEM) analysis. The as-prepared CDs displayed dual-fluorescence peaks at 525 and 620 nm upon excitation at 450 nm. The CDs showed good photostability and exhibited solvent-dependent fluorescence properties. The solvatochromic behavior of CDs was utilized to detect water content in organic solvents. Furthermore, the dual-emissive property of CDs was utilized for the sequential detection of ferric (Fe³⁺) and pyrophosphate ions (PPi) by a fluorescence turn-off-on mechanism. The proposed assay showed appreciable fluorescence response toward Fe³⁺ and PPi with high selectivity and good tolerance for common interfering ions. The potential practical application of the CD probe was ascertained by carrying out the fluorometric detection of PPi to affirm the loop-mediated isothermal amplification (LAMP) reaction specific for Mycobacterium tuberculosis (negative and positive clinical samples).