Nucleolus-Targeted Photodynamic Anticancer Therapy Using Renal-Clearable Carbon Dots

Visualizing mitochondrial ATP fluctuations in single cells during photodynamic therapy by In-Situ SERS three-dimensional imaging

An ultrasensitive strategy for in-situ visual monitoring of ATP in a single living tumor cell during mitochondria-targeted photodynamic therapy (PDT) process with high spatiotemporal resolution was proposed using surface-enhanced Raman scattering (SERS) 3D imaging technique. The nanostructures consisting of Au-Ag2S Janus nanoparticles functionalized with both Au nanoparticles linked by a DNA chain and a mitochondrial-targeting peptide (JMDA NPs) were deliberately employed to target mitochondria. The JMDA NPs exhibit excellent SERS activity and remarkable antitumor activity. The quantization of ATP relies on the intensity of the SERS probes bonded to the DNA, which shows a strong correlation with the generated hot spot between the Janus and the Au. Consequently, spatiotemporally controlled monitoring of ATP in the mitochondria of single living cells during the PDT process was achieved. Additionally, the JMDA NPs demonstrated remarkable capability for mitochondria-targeted PDT, providing significant antitumor effects and superior therapeutic safety both in vitro and in vivo. Our work presents an effective JMDA NPs-based SERS imaging strategy for in-situ and real-time 3D visualization of intracellular ATP in living tumor cells during the mitochondria-targeted PDT process, which enables significant information on the time point of PDT treatment and is beneficial to precious PDT applications in tumor therapy.

Carbon Dots in the Pathological Microenvironment: ROS Producers or Scavengers?

Reactive oxygen species (ROS), as metabolic byproducts, play pivotal role in physiological and pathological processes. Recently, studies on the regulation of ROS levels for disease treatments have attracted extensive attention, mainly involving the ROS-induced toxicity therapy mediated by ROS producers and antioxidant therapy by ROS scavengers. Nanotechnology advancements have led to the development of numerous nanomaterials with ROS-modulating capabilities, among which carbon dots (CDs) standing out as noteworthy ROS-modulating nanomedicines own their distinctive physicochemical properties, high stability, and excellent biocompatibility. Despite progress in treating ROS-related diseases based on CDs, critical issues such as rational design principles for their regulation remain underexplored. The primary cause of these issues may stem from the intricate amalgamation of core structure, defects, and surface states, inherent to CDs, which poses challenges in establishing a consistent generalization. This review succinctly summarizes the recently progress of ROS-modulated approaches using CDs in disease treatment. Specifically, it investigates established therapeutic strategies based on CDs-regulated ROS, emphasizing the interplay between intrinsic structure and ROS generation or scavenging ability. The conclusion raises several unresolved key scientific issues and prominent technological bottlenecks, and explores future perspectives for the comprehensive development of CDs-based ROS-modulating therapy.

Carbon dots as a novel photosensitizer for photodynamic therapy of cancer and bacterial infectious diseases: recent advances

Carbon dots (CDs) are novel carbon-based nanomaterials that have been used as photosensitizer-mediated photodynamic therapy (PDT) in recent years due to their good photosensitizing activity. Photosensitizers (PSs) are main components of PDT that can produce large amounts of reactive oxygen species (ROS) when stimulated by light source, which have the advantages of low drug resistance and high therapeutic efficiency. CDs can generate ROS efficiently under irradiation and therefore have been extensively studied in disease local phototherapy. In tumor therapy, CDs can be used as PSs or PS carriers to participate in PDT and play an extremely important role. In bacterial infectious diseases, CDs exhibit high bactericidal activity as CDs are effective in disrupting bacterial cell membranes leading to bacterial death upon photoactivation. We focus on recent advances in the therapy of cancer and bacteria with CDs, and also briefly summarize the mechanisms and requirements for PSs in PDT of cancer, bacteria and other diseases. We also discuss the role CDs play in combination therapy and the potential for future applications against other pathogens.

Boosted photo-immunotherapy via near-infrared light excited phototherapy in tumor sites and photo-activation in sentinel lymph nodes

Phototherapy is a promising modality that could eradicate tumor and trigger immune responses via immunogenic cell death (ICD) to enhance anti-tumor immunity. However, due to the lack of deep-tissue-excitable phototherapeutic agents and appropriate excitation strategies, the utility of phototherapy for efficient activation of the immune system is challenging. Herein, we report functionalized ICG nanoparticles (NPs) with the capture capability of tumor-associated antigens (TAAs). Under near-infrared (NIR) light excitation, the ICG NPs exhibited high-performance phototherapy, i.e., synergistic photothermal therapy and photodynamic therapy, thereby efficiently eradicating primary solid tumor and inducing ICD and subsequently releasing TAAs. The ICG NPs also captured TAAs and delivered them to sentinel lymph nodes, and then the sentinel lymph nodes were activated with NIR light to trigger efficient T-cell immune responses through activation of dendritic cells with the assistance of ICG NP generated reactive oxygen species, inhibiting residual primary tumor recurrence and controlling distant tumor growth. The strategy of NIR light excited phototherapy in tumor sites and photo-activation in sentinel lymph nodes provides a powerful platform for active immune systems for anti-tumor photo-immunotherapy.

The future of plant based green carbon dots as cancer Nanomedicine: From current progress to future Perspectives and beyond

BACKGROUND

The emergence of carbon dots (CDs) as anticancer agents had sparked a transformation in cancer research and treatment strategies. These fluorescent CDs, initially introduced in the early 2000 s, possess exceptional biocompatibility, tunable fluorescence, and surface modification capabilities, positioning them as promising tools in biomedical applications.

AIM OF REVIEW

The review encapsulates the transformative trajectory of green CDs as future anticancer nanomedicine, poised to redefine the strategies employed in the ongoing fight against cancer.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The versatility of CDs was rooted in their various synthesis approaches and sustainable strategies, enabling their adaptability for diverse therapeutic uses. In vitro studies had showcased CDs' selective cytotoxicity against cancer cells while sparing healthy counterparts, forming the basis for targeted therapeutic potential. This selectivity had been attributed to the reactive oxygen species (ROS) generation, which opened avenues for targeted interventions. The role of CDs in combination therapies, synergizing with chemotherapy, radiotherapy, and targeted approaches was then investigated to heighten their anticancer efficacy. Notably, in vivo studies highlight CDs' remarkable biocompatibility and minimal side effects, endorsing their translational promise. Integration with conventional cancer treatments such as chemotherapy, radiotherapy, and immunotherapy amplified the versatility and effectiveness of CDs. The exploration of CDs' applications in photo-induced treatments further solidified their significance, positioning them as photosensitizers (PS) in photodynamic therapy (PDT) and photothermal agents (PA) in photothermal therapy (PTT). In PDT, CDs triggered the generation of ROS upon light exposure, facilitating cancer cell elimination, while in PTT, they induced localized hyperthermia within cancer cells, enhancing therapeutic outcomes. In vitro and in vivo investigations validated CDs' efficacy in PDT and PTT, affirming their potential for integration into combination therapies. Looking ahead, the future of CDs in anticancer treatment encompasses bioavailability, biocompatibility, synergistic treatments, tumor targeting, artificial intelligence (AI) and robotics integration, personalized medicine, and clinical translation. This transformative odyssey of CDs as future anticancer agents is poised to redefine the paradigm of cancer treatment strategies.

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.

Fe-doped carbon dots: a novel biocompatible nanoplatform for multi-level cancer therapy

BACKGROUND

Tumor treatment still remains a clinical challenge, requiring the development of biocompatible and efficient anti-tumor nanodrugs. Carbon dots (CDs) has become promising nanomedicines for cancer therapy due to its low cytotoxicity and easy customization.

RESULTS

Herein, we introduced a novel type of "green" nanodrug for multi-level cancer therapy utilizing Fe-doped carbon dots (Fe-CDs) derived from iron nutrient supplement. With no requirement for target moieties or external stimuli, the sole intravenous administration of Fe-CDs demonstrated unexpected anti-tumor activity, completely suppressing tumor growth in mice. Continuous administration of Fe-CDs for several weeks showed no toxic effects in vivo, highlighting its exceptional biocompatibility. The as-synthesized Fe-CDs could selectively induce tumor cells apoptosis by BAX/Caspase 9/Caspase 3/PARP signal pathways and activate antitumoral macrophages by inhibiting the IL-10/Arg-1 axis, contributing to its significant tumor immunotherapy effect. Additionally, the epithelial-mesenchymal transition (EMT) process was inhibited under the treatment of Fe-CDs by MAPK/Snail pathways, indicating the capacity of Fe-CDs to inhibit tumor recurrence and metastasis.

CONCLUSIONS

A three-level tumor treatment strategy from direct killing to activating immunity to inhibiting metastasis was achieved based on "green" Fe-CDs. Our findings reveal the broad clinical potential of Fe-CDs as a novel candidate for anti-tumor nanodrugs and nanoplatform.

Recent strategies of carbon dot-based nanodrugs for enhanced emerging antitumor modalities

Nanomaterial-based cancer therapy has recently emerged as a new therapeutic modality with the advantages of minimal invasiveness and negligible normal tissue toxicity over traditional cancer treatments. However, the complex microenvironment and self-protective mechanisms of tumors have suppressed the therapeutic effect of emerging antitumor modalities, which seriously hindered the transformation of these modalities to clinical settings. Due to the excellent biocompatibility, unique physicochemical properties and easy surface modification, carbon dots, as promising nanomaterials in the biomedical field, can effectively improve the therapeutic effect of emerging antitumor modalities as multifunctional nanoplatforms. In this review, the mechanism and limitations of emerging therapeutic modalities are described. Further, the recent advances related to carbon dot-based nanoplatforms in overcoming the therapeutic barriers of various emerging therapies are systematically summarized. Finally, the prospects and potential obstacles for the clinical translation of carbon dot-based nanoplatforms in tumor therapy are also discussed. This review is expected to provide a reference for nanomaterial design and its development for the efficacy enhancement of emerging therapeutic modalities.

A Fluorescent Vector of Carbon Dot to Deliver Rab13 and Rab14 Plasmids for Promoting Neurite Outgrowth

The complex processes of neuron differentiation and neuron repair are critical for treating nervous system injuries and neurodegenerative diseases. Neurite outgrowth plays a crucial role in these processes by enabling the formation of connections between neurons and the generation of neuroplasticity to restore the function of the nervous system. In this study, we fabricated functionalized carbon dots (CDs) with distinctive photoluminescence and low cytotoxicity for use as fluorescence imaging probes and nanocarriers to deliver plasmid DNAs to neurons effectively for inducing neurite outgrowth. CDs were prepared through a reflux process in nitric acid solution, and their surface was then modified using polyethylenimine (PEI) to obtain positively charged CDs for increasing the absorption of plasmid DNAs and the efficiency of cell uptake. Experimental results indicated that the fabricated CDs maintained a low cytotoxicity and exhibited a high neuron uptake of up to 97%. An improvement in the plasmid DNA ingestion of neurons resulted in enhanced expression of Rab13-Q67L and Rab14 proteins, which considerably promoted neurite sprouting and elongation. After the fabricated PEI-modified CDs were used to deliver the Rab13-Q67L and Rab14 plasmids, more than 56% of the neurons had a neurite length that was greater than twice the size of their soma. Thus, DNA delivery through functionalized CDs has a high potential for use in gene therapy for neuronal injuries and diseases.

Recent progress in carbon dots for anti-pathogen applications in oral cavity

Background

Oral microbial infections are one of the most common diseases. Their progress not only results in the irreversible destruction of teeth and other oral tissues but also closely links to oral cancers and systemic diseases. However, traditional treatment against oral infections by antibiotics is not effective enough due to microbial resistance and drug blocking by oral biofilms, along with the passive dilution of the drug on the infection site in the oral environment.

Aim of review

Besides the traditional antibiotic treatment, carbon dots (CDs) recently became an emerging antimicrobial and microbial imaging agent because of their excellent (bio)physicochemical performance. Their application in treating oral infections has received widespread attention, as witnessed by increasing publication in this field. However, to date, there is no comprehensive review available yet to analyze their effectiveness and mechanism. Herein, as a step toward addressing the present gap, this review aims to discuss the recent advances in CDs against diverse oral pathogens and thus propose novel strategies in the treatment of oral microbial infections.

Key scientific concepts of review

In this manuscript, the recent progress of CDs against oral pathogens is summarized for the first time. We highlighted the antimicrobial abilities of CDs in terms of oral planktonic bacteria, intracellular bacteria, oral pathogenic biofilms, and fungi. Next, we introduced their microbial imaging and detection capabilities and proposed the prospects of CDs in early diagnosis of oral infection and pathogen microbiological examination. Lastly, we discussed the perspectives on clinical transformation and the current limitations of CDs in the treatment of oral microbial infections.

Meticulously Designed Carbon Dots as Photo-Triggered RNA-Destroyer for Evoking Pyroptosis

An ideal photosensitizer for photodynamic therapy should not only possess high reactive oxygen species (ROS) generation efficiency but also maximize utilization of the in situ produced ROS species, where the latter is closely related to its intracellular location. However, rational design of such photosensitizer without tedious conjugation procedures remains a grand challenge. Here, we report the one-pot preparation of carbon dots (CDs)-based photosensitizer from levofloxacin and neutral red featuring both high 1O2 quantum yield (φΔ = 38.85%) and superior RNA selectivity. Moreover, the φΔ value shows a further 40% improvement and reaches 54.33% in response to RNA binding. Owing to these combined attributes, the CDs could exert great damage to the cellular RNA system (termed the RNA-destroyer) under extremely low dosage of light irradiation (15 mW cm-2, 1 min). It induces pyroptotic cell death and causes rapid release of different cytokines that served as molecular markers in photodynamic immunotherapy. This work represents the meticulously designed CDs with high ROS generation and utilization efficiency via good organization of the photosensitive and targeting modularity. Moreover, it is the first CDs-based pyroptosis inducer to the best of our knowledge.

RNA-Targeting Carbon Dots for Live-Cell Imaging of Granule Dynamics

It is significant to monitor the different RNA granules dynamics and phase separation process inside cells under various stresses, for example, oxidative stress. The current small-molecule RNA probes work well only in fixed cells and usually encounter problems such as insufficient stability and biocompatibility, and thus a specific RNA-targeting fluorescent nanoprobe that can be used in the living cells is urgently desired. Here, the de novo design and microwave-assisted synthesis of a novel RNA-targeting, red-emissive carbon dots (named as M-CDs) are reported by choosing neutral red and levofloxacin as precursors. The as-synthesized M-CDs is water-soluble with a high fluorescence quantum yield of 22.83% and can selectively bind to RNA resulting in an enhanced red fluorescence. More interestingly, such an RNA-targeting, red-emissive M-CDs can be fast internalized into cells within 5 s and thus used for real-time imaging the dynamic process of intracellular stress granules under oxidative stress, revealing some characteristics of granules that have not been identified by previously reported RNA and protein biomarkers. This research paves a new pathway for visualizing bulk RNA dynamics and studying phase-separation behaviors in living cells by rational design of the fluorescent carbon dots in terms of structure and functionality.

Superior biocompatible carbon dots for dynamic fluorescence imaging of nucleoli in living cells

The nucleolus is a newly developed and promising target for cancer diagnosis and therapy, and its imaging is extremely significant for fundamental research and clinical applications. The unique feature, i.e., high resolution at the subcellular level, makes the fluorescence imaging method a powerful tool for nucleolus imaging. However, the fluorescence imaging of nucleoli in living cells is restricted by the limited availability of fluorescent agents with specific nucleolus-targeting capability and superior biocompatibility. Here, promising carbon dots (CDs) with intrinsic nucleolus-targeting capability were synthesized, characterized and employed for dynamic fluorescence imaging of nucleoli in living cells. The CDs exhibit a high fluorescence quantum yield of 0.2, excellent specificity and photostability, and superior biocompatibility, which were systematically demonstrated at the gene, cellular and animal levels and confirmed by their biological effects on embryonic development. All these features enabled CDs to light up the nucleoli for a long time with a high signal-to-noise ratio in living cells and monitor the nucleolar dynamics of malignant cells in camptothecin (CPT) based chemotherapy. Their excellent optical and biological features as well as general nucleolus-targeting capability endow CDs with great potential for future translational research.

High biocompatible nitrogen and sulfur Co-doped carbon dots for Hg(II) detection and their long-term biological stability in living cells

Fluorescent carbon dots have been highly reported nanomaterials in recent times because of their excellent physio-chemical properties and various field of applications. Herein, a one-step hydrothermal approach was used to synthesize high biocompatible nitrogen and sulfur co-doped carbon dots, and examined their chemical sensing (Hg²⁺) and biological imaging properties. The N,S-CDs exhibited blue light, demonstrating a high quantum yield of up to 44.5% and excitation-independent fluorescent characteristics. Cytotoxicity was observed by CCK-8 assay using T-ca cells as a target source. Cell viability was recorded over 80% even after 7 days of treatment with a concentration up to 400 μg/mL, indicating low-toxicity of N,S-CDs. Notably, the bright blue fluorescence of N,S-CDs was quenched by introducing toxic Hg²⁺ ions into the solution. The detection limit was calculated to be about ∼3.5 nM, which is quite impressive compared to previous reports. Because of their low-toxicity, nano-size, and environment friendly properties, N,S-CDs could be excellent fluorescent agents for bio-imaging applications. The biological stability of fluorescent N,S-CDs was tested over time, and the findings were significant even after 8 days of incubation with T-ca cells. Because of good biocompatibility and bright fluorescence, N,S-CDs were suitable for in vivo imaging.

Two-photon photodynamic therapy based on FRET using tumor-cell targeted riboflavin conjugated graphene quantum dot

The photodynamic therapy (PDT) is considered as a noninvasive and photo-controlled treatment for various cancers. However, its potential is not fully developed as current clinically approved photosensitizers (PSs) mainly absorb the light in the UV-visible region (less than 700 nm), where the depth of penetration is inadequate for reaching tumor cells under deeper tissue layers. Furthermore, the lack of specific accumulation capability of the conventional PSs in the tumor cells may cause serious toxicity and low treatment efficiency. To address these problems, riboflavin (Rf) conjugated and amine-functionalized nitrogen-doped graphene quantum dots (am-N-GQD) are herein proposed. Rf functions as both photosensitizer and targeting ligand by indirect excitation through intra-particle fluorescence resonance energy transfer (FRET) via two-photon (TP) excited am-N-GQD, to enhance the treatment depth, and further am-N-GQD-Rf accumulation in cancer cells using Rf transporter family (RFVTs) and Rf carrier proteins (RCPs). The one-photon (OP) and two-photon(TP)-PDT effect and cellular internalization ability of the am-N-GQD-Rf were investigated in vitro in different cancel cell lines. Besides the excellent cellular uptake as well TP-PDT capability, the superior biocompatibility of am-N-GQD-Rf in vitro makes it promising candidate in PDT.

Carbon dot-based nanomaterials: a promising future nano-platform for targeting tumor-associated macrophages

The tumor microenvironment (TME) is the internal environment that tumors depend on for survival and development. Tumor-associated macrophages (TAMs), as an important part of the tumor microenvironment, which plays a crucial role in the occurrence, development, invasion and metastasis of various malignant tumors and has immunosuppressant ability. With the development of immunotherapy, eradicating cancer cells by activating the innate immune system has yielded encouraging results, however only a minority of patients show a lasting response. Therefore, in vivo imaging of dynamic TAMs is crucial in patient-tailored immunotherapy to identify patients who will benefit from immunotherapy, monitor efficacy after treatment, and identify alternative strategies for non-responders. Meanwhile, developing nanomedicines based on TAMs-related antitumor mechanisms to effectively inhibit tumor growth is expected to become a promising research field. Carbon dots (CDs), as an emerging member of the carbon material family, exhibit unexpected superiority in fluorescence imaging/sensing, such as near infrared imaging, photostability, biocompatibility and low toxicity. Their characteristics naturally integrate therapy and diagnosis, and when CDs are combined with targeted chemical/genetic/photodynamic/photothermal therapeutic moieties, they are good candidates for targeting TAMs. We concentrate our discussion on the current learn of TAMs and describe recent examples of macrophage modulation based on carbon dot-associated nanoparticles, emphasizing the advantages of their multifunctional platform and their potential for TAMs theranostics.

Regulating photochemical properties of carbon dots for theranostic applications

As a new zero-dimensional carbon-based material, carbon dots (CDs) have attracted extensive attention owing to their advantages such as easy preparation and surface modification, good biocompatibility and water solubility, and tunable photochemical properties. CDs have become one of the most promising nanomaterials in the field of fluorescent sensing, bioimaging, and cancer therapy. How to precisely regulate the photochemical properties, especially the absorption, fluorescence, phosphorescence, reactive oxygen species generation, and photothermal conversion of the CDs, is the key to developing highly efficient phototheranostics for cancer treatment. Although many studies on cancer therapy using CDs have been published, no review has focused on the regulation of photochemical properties of CDs for phototheranostic applications. In this review, we summarized the strategies such as the selection of suitable carbon source, heteroatomic doping, optimum reaction conditions, surface modification, and assembly strategy to efficiently regulate the photochemical properties of the CDs to meet the requirements of different practical applications. This review might provide some valuable insight and new ideas for the development of CDs with excellent phototheranostic performance. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Carbon dots conjugated to SN38 for improved colorectal anticancer therapy

Irinotecan (CTP-11) is one of the standard therapies for colorectal cancer (CRC). CTP-11 is enzymatically converted to the hydrophobic 7-ethyl-10-hydroxycamptothecin (SN38), a one hundred-fold more active metabolite. Conjugation of hydrophobic anticancer drugs to nanomaterials is a strategy to improve their solubility, efficacy, and selectivity. Carbon dots (CDs) have garnered interest for their small sizes (<10 ​nm), low toxicity, high water solubility, and bright fluorescence. This paper describes the use of CDs to improve drug vehiculation, stability, and chemotherapeutic efficiency of SN38 through a direct intracellular uptake in CRC. The covalent conjugation of SN38 to CDs via a carbamate bond provides a CD-SN38 hybrid material for slow, sustained, and pH-responsive drug release. CD-SN38 successfully penetrates the CRC cells with a release in the nucleus affecting first the cell cycle and then the cytoskeleton. Moreover, CD-SN38 leads to a deregulation of the extracellular matrix (ECM), one of the major components of the cancer niche considered a possible target therapy for reducing the cancer progression. This work shows the combined therapeutic and imaging potential of CD-based hybrid materials for the treatment of CRC. Future efforts for targeted therapy of chronic diseases characterized by altered ECM deposition, such as chronic kidney disease and chronic allograft nephropathy in kidney transplant patients are envisaged.

Cadmium induced aggregation of orange-red emissive carbon dots with enhanced fluorescence for intracellular imaging

Cadmium is a notorious toxic heavy metal, that poses serious threat to human health. Sensitive and selective detection of cadmium in cells is of great significance in poison screening and disease diagnosis. Orange-red emissive carbon dots (OR-CDs), prepared from the calcination of selected carbon sources 5-amino-1, 10-phenanthroline (Aphen) and salicylic acid (SA), were found to act as a "turn on" type fluorescence probe for Cd²⁺ detection. The structure and optical properties of OR-CDs were comprehensively investigated by both experimental characterizations and density functional theory (DFT) calculations. The OR-CDs consist of a basic unit of nine aromatic rings, and the N/O binding sites on the OR-CDs can specifically bind with Cd²⁺, leading to aggregation induced enhanced emission (AIEE). A detection limit of 0.30 μM was achieved for Cd²⁺ with a linear range of 0.80-100 μM. OR-CDs can not only be used for intracellular Cd²⁺ imaging but also have the potential to alleviate cadmium poison in living organisms.

Carbon Dot Therapeutic Platforms: Administration, Distribution, Metabolism, Excretion, Toxicity, and Therapeutic Potential

Ultrasmall nanoparticles are often grouped under the broad umbrella term of "nanoparticles" when reported in the literature. However, for biomedical applications, their small sizes give them intimate interactions with biological species and endow them with unique functional physiochemical properties. Carbon quantum dots (CQDs) are an emerging class of ultrasmall nanoparticles which have demonstrated considerable biocompatibility and have been employed as potent theragnostic platforms. These particles find application for increasing drug solubility and targeting, along with facilitating the passage of drugs across impermeable membranes (i.e., blood brain barrier). Further functionality can be triggered by various environmental conditions or external stimuli (i.e., pH, temperature, near Infrared (NIR) light, ultrasound), and their intrinsic fluorescence is valuable for diagnostic applications. The focus of this review is to shed light on the therapeutic potential of CQDs and identify how they travel through the body, reach their site of action, administer therapeutic effect, and are excreted. Investigation into their toxicity and compatibility with larger nanoparticle carriers is also examined. The future of CQDs for theragnostic applications is promising due to their multifunctional attributes and documented biocompatibility. As nanomaterial platforms become more commonplace in clinical treatments, the commercialization of CQD therapeutics is anticipated.

MXenes Quantum Dots for Biomedical Applications: Recent Advances and Challenges

MXenes have aroused widespread interest in the biomedical field owing to their remarkable photo-thermal conversion capabilities combined with large specific surface areas. MXenes quantum dots (MQDs) have been synthesized either by the physical or chemical methods based on MXenes as precursors, which possess smaller size, higher photoluminescence, coupled with low cytotoxicity and many beneficial properties of MXenes, thereby having potential biomedical applications. Given this, this review summarized the synthesis methods, optical, surface and biological properties of MQDs along with their practical applications in the field of biomedicine. Finally, the authors make an outlook towards the synthesis, properties and applications of MQDs in the future biomedicine field.

Light amplified oxidative stress in tumor microenvironment by carbonized hemin nanoparticles for boosting photodynamic anticancer therapy

Photodynamic therapy (PDT), which utilizes light excite photosensitizers (PSs) to generate reactive oxygen species (ROS) and consequently ablate cancer cells or diseased tissue, has attracted a great deal of attention in the last decades due to its unique advantages. However, the advancement of PDT is restricted by the inherent characteristics of PS and tumor microenvironment (TME). It is urgent to explore high-performance PSs with TME regulation capability and subsequently improve the therapeutic outcomes. Herein, we reported a newly engineered PS of polymer encapsulated carbonized hemin nanoparticles (P-CHNPs) via a facile synthesis procedure for boosting photodynamic anticancer therapy. Solvothermal treatment of hemin enabled the synthesized P-CHNPs to enhance oxidative stress in TME, which could be further amplified under light irradiation. Excellent in vitro and in vivo PDT effects were achieved due to the improved ROS (hydroxyl radicals and singlet oxygen) generation efficiency, hypoxia relief, and glutathione depletion. Moreover, the superior in vitro and in vivo biocompatibility and boosted PDT effect make the P-CHNPs a potential therapeutic agent for future translational research.

Applications and Immunological Effects of Quantum Dots on Respiratory System

Quantum dots (QDs), are one kind of nanoscale semiconductor crystals with specific electronic and optical properties, offering near-infrared mission and chemically active surfaces. Increasing interest for QDs exists in developing theranostics platforms for bioapplications such as imaging, drug delivery and therapy. Here we summarized QDs’ biomedical applications, toxicity, and immunological effects on the respiratory system. Bioapplications of QDs in lung include biomedical imaging, drug delivery, bio-sensing or diagnosis and therapy. Generically, toxic effects of nanoparticles are related to the generation of oxidative stresses with subsequent DNA damage and decreased lung cells viability in vitro and in vivo because of release of toxic metal ions or the features of QDs like its surface charge. Lastly, pulmonary immunological effects of QDs mainly include proinflammatory cytokines release and recruiting innate leukocytes or adaptive T cells.

A multifunctional chemical toolbox to engineer carbon dots for biomedical and energy applications

Photoluminescent carbon nanoparticles, or carbon dots, are an emerging class of materials that has recently attracted considerable attention for biomedical and energy applications. They are defined by characteristic sizes of <10 nm, a carbon-based core and the possibility to add various functional groups at their surface for targeted applications. These nanomaterials possess many interesting physicochemical and optical properties, which include tunable light emission, dispersibility and low toxicity. In this Review, we categorize how chemical tools impact the properties of carbon dots. We look for pre- and postsynthetic approaches for the preparation of carbon dots and their derivatives or composites. We then showcase examples to correlate structure, composition and function and use them to discuss the future development of this class of nanomaterials.

Two-photon excitable membrane targeting polyphenolic carbon dots for long-term imaging and pH-responsive chemotherapeutic drug delivery for synergistic tumor therapy

Long-term dynamic tracking of cells with theranostics properties remains challenging due to difficulty in preparing and delivering drugs by the probes. Herein, we developed a highly fluorescent one- and two-photon...

Carbon nanomaterials as emerging nanotherapeutic platforms to tackle the rising tide of cancer - A review

Cancer has become one of the main reasons for human death in recent years. Around 18 million new cancer cases and approximately 9.6 million deaths from cancer reported in 2018, and the annual number of cancer cases will have increased to 22 million in the next two decades. These alarming facts have rekindled researchers' attention to develop and apply different approaches for cancer therapy. Unfortunately, most of the applied methods for cancer therapy not only have adverse side effects like toxicity and damage of healthy cells but also have a short lifetime. To this end, introducing innovative and effective methods for cancer therapy is vital and necessary. Among different potential materials, carbon nanomaterials can cope with the rising threats of cancer. Due to unique physicochemical properties of different carbon nanomaterials including carbon, fullerene, carbon dots, graphite, single-walled carbon nanotube and multi-walled carbon nanotubes, they exhibit possibilities to address the drawbacks for cancer therapy. Carbon nanomaterials are prodigious materials due to their ability in drug delivery or remedial of small molecules. Functionalization of carbon nanomaterials can improve the cancer therapy process and decrement the side effects. These exceptional traits make carbon nanomaterials as versatile and prevalent materials for application in cancer therapy. This article spotlights the recent findings in cancer therapy using carbon nanomaterials (2015-till now). Different types of carbon nanomaterials and their utilization in cancer therapy were highlighted. The plausible mechanisms for the action of carbon nanomaterials in cancer therapy were elucidated and the advantages and disadvantages of each material were also illustrated. Finally, the current problems and future challenges for cancer therapy based on carbon nanomaterials were discussed.

In Vivo Biodistribution, Clearance, and Biocompatibility of Multiple Carbon Dots Containing Nanoparticles for Biomedical Application

Current research on the use of carbon dots for various biological systems mainly focuses on the single carbon dots, while particles that contain multiple carbon dots have scarcely been investigated. Here, we assessed multiple carbon dots-crosslinked polyethyleneimine nanoparticles (CDs@PEI) for their in vivo biodistribution, clearance, biocompatibility, and cellular uptake. The in vivo studies demonstrate three unique features of the CDs@PEI nanoparticles: (1) the nanoparticles possess tumor-targeting ability with steady and prolonged retention time in the tumor region. (2) The nanoparticles show hepatobiliary excretion and are clear from the intestine in feces. (3) The nanoparticles have much better biocompatibility than the polyethyleneimine passivated single carbon dots (PEI-CD). We also found that pegylated CDs@PEI nanoparticles can be effectively taken up by the cells, which the confocal laser scanning microscope can image under different excitation wavelengths (at 405, 488, and 800 nm). These prior studies provide invaluable information and new opportunities for this new type of intrinsic photoluminescence nanoparticles in carbon dot-based biomedical applications.

Riboflavin-based carbon dots with high singlet oxygen generation for photodynamic therapy

Photodynamic therapy, as an effective treatment for superficial tumors, has attracted more and more attention. The development of safe, biocompatible and in vivo photosensitive materials is helpful to promote photodynamic therapy. Here we report green fluorescent carbon quantum dots prepared from a natural vitamin, riboflavin (VB2), as a photosensitizer. The VB2-based carbon dots have excellent water solubility and biocompatibility, and their singlet oxygen generation ability is much stronger than that of riboflavin itself. Through endocytosis, the carbon dots can easily enter the cells and show bright green fluorescence. In vivo experiments show that after photodynamic therapy the carbon dots can significantly inhibit the growth of tumors, and will not have toxic and side effects on other organs.

Carbon-Defect-Driven Boron Carbide for Dual-Modal NIR-II/Photoacoustic Imaging and Photothermal Therapy

Recently, tremendous attention has been evoked in the discovery of defect-engineered nanomaterials for near-infrared second window (NIR-II)-driven cancer therapy. Herein, we have constructed a novel type of carbon defects enriched in boron carbide nanomaterial (denoted as B₄C@C) through reacting B₄C and glucose by a hydrothermal method. The carbon defect concentration in B₄C@C has been significantly increased after coating with glucose; thus, B₄C@C exhibited a distinct photothermal response under the NIR-II window and the efficiency of photothermal conversion is determined to reach 45.4%, which is higher than the carbon-based nanomaterials in the NIR-II region. Both Raman spectra and X-ray photoelectron spectroscopy (XPS) spectra reveal that B₄C@C has rich sp²-hybridized carbon defects and effectively increases the NIR-II window light absorption capacity, thus enhancing the nonradiative recombination rate and improving the NIR-II photothermal effect. Furthermore, the B₄C@C nanosheets allows for tumor phototherapy and simultaneous photoacoustic imaging. This work indicates the huge potential of B₄C@C as a novel photothermal agent, which might arise much attention in exploring boron-based nanomaterials for the advantage of cancer therapy.

Fabrication of G-quadruplex/porphyrin conjugated gold/persistent luminescence theranostic nanoprobe for imaging-guided photodynamic therapy

Photodynamic therapy (PDT) received great attention in cancer therapy due to the advantages of negligible drug resistance, low side effects, and minimal invasiveness. Development of theranostic nanoprobes with specific imaging-guided PDT is of great significance in the field. Herein we report the fabrication of a novel theranostic nanoprobe porphyrin/G-quadruplex conjugated gold/persistent luminescence nanocomposites for imaging-guided PDT. The developed nanoprobe contains NIR-emitting persistent luminescent nanoparticles (PLNP) as the core for autofluorescence-free bioimaging and Au coating on PLNP for facile subsequent DNA conjugation. The DNA sequence is designed to contain G-rich AS1411 aptamer for recognizing the over-expressed cellular nucleolin of cancer cell and forming a G-quadruplex structure to combine with tetrakis (4-carboxyphenyl) porphyrin (TCPP) to realize PDT. The AS1411 aptamer-contained DNA conjugated Au-coated PLNP is rapidly prepared via a freezing method with high content of DNA and good aqueous stability. Meanwhile, TCPP is easily loaded into the G-quadruplex structure formed from G-rich AS1411 aptamer on the surface of Au/PLNP in presence of K⁺. The theranostic nanoprobe gives integrated merits of PLNP for autofluorescence-free bioimging, TCPP for PDT and AS1411 aptamer-contained DNA for specific binding to cancer cells. This work provides a new specially designed imaging-guided PDT nanoplatform for theranostics.

Nitrogen-doped carbon dots for wash-free imaging of nucleolus orientation

Carbon dots (CDs) are a rising star in the field of cellular imaging, especially cytoplasmic imaging, attributing to the super-stable optical performance and ultra-low biological toxicity. Nucleolus can accurately reflect the expression state of a cell and is strongly linked to the occurrence and development of many diseases, so exploring bran-new CDs for nucleolus-orientation imaging with no-wash technology has important theoretical value and practical significance. Herein, nitrogen-doped carbon dots (N-CDs) with green fluorescence (the relative fluorescence quantum yield of 24.4%) was fabricated by the hydrothermal treatment of m-phenylenediamine and p-aminobenzoic acid. The N-CDs possess small size, bright green fluorescence, abundant surface functional groups, excellent fluorescence stability and good biocompatibility, facilitating that the N-CDs are an excellent imaging reagent for cellular imaging. N-CDs can particularly bind to RNA in nucleoli to enhance their fluorescence, which ensures that the N-CDs can be used in nucleolus-orientation imaging with high specificity and wash-free technique. This study demonstrates that the N-CDs have a significant feasibility to be used for nucleolus-orientation imaging in biomedical analysis and clinical diagnostic applications.

Near-infrared light excited photodynamic anticancer therapy based on UCNP@AIEgen nanocomposite

Photodynamic therapy (PDT), a clinically approved cancer treatment strategy, features non-invasiveness, few side-effects, high spatial resolution, etc. The advancement of PDT has been significantly restricted by the penetration depth of the excitation light. Herein, an effective fluorogen, TBD, with aggregation-induced emission characteristics (AIEgen) and high reactive-oxygen-species (ROS) generation efficiency was reported and integrated with a near infrared (NIR) light excitable upconversion nanoparticle (UCNP) to construct NIR light excitable UCNP@TBD nanocomposites. The formed nanocomposite has excellent photostability, good biocompatibility, and efficient ROS generation under NIR light excitation via Förster resonance energy transfer (FRET), enabling NIR light excited PDT. Moreover, the proposed NIR light excited PDT can break the impasse between the penetration depth and excitation volume in conventional PDT, effectively improving the anticancer therapeutic outcome. In vitro cancer cell ablation and in vivo tumor growth inhibition validated that the proposed UCNP@TBD nanocomposite is a promising NIR light excitable PDT agent with great potential for future translational research.

Rapid ex vivo assessment of cancer prognosis by fluorescence imaging of nucleolus using nitrogen doped carbon dots

Cancer severely threatens human health currently, promoting the rapid development of cancer treatment strategies. In addition to cancer therapy, assessment of cancer prognosis, which can evaluate the success with treatment and chances of recovery as well as assist to make subsequent therapeutic schedule, is also remarkably indispensable and important. Conventional technologies can't provide rapid and highly-sensitive assessment of cancer prognosis at cytological level. Herein, an effective nitrogen doped carbon dots with intrinsic nucleolus-targeting capability and high fluorescence quantum yield are synthesized, characterized and employed for fluorescence imaging of nucleolus, which is closely related to the biological alteration of cancer cell. The cancer prognosis thus can be accurately (limit of detection: 50 nM) and rapidly (5 min) assessed at subcellular organelle level from nucleolar characteristics, which are visualized and analyzed by the captured fluorescence images. Outstanding assessment performance endows the proposed technology with great potential for future clinical research.

Superior reducing carbon dots from proanthocyanidin for free-radical scavenging and for cell imaging

The presence of excessive ROS can cause much harm to the human body and can even cause diseases. Therefore, it is important to detect and remove ROS, but there is no ideal method available for this at present. In this research, using procyanidins, a type of plant extract with strong reducibility, as raw materials, fluorescent carbon dots (CDs) were prepared by a hydrothermal method. The proanthocyanidin-based carbon dots (PCDs) emit a light-green colored light under UV irradiation. The PCDs retain the strong reducibility of procyanidins and are highly water-soluble compared with procyanidins. The PCDs, in addition to having good biocompatibility, also have the superior properties of radical scavenging activity and cell imaging. In in vitro experiments, 1,1-diphenyl-2-picrylhydrazyl (DPPH; 100 μM) was reduced by 30% when PCDs were added up to a concentration of 87.5 μg mL^-1. At the same time, the fluorescence quenching correlates with the concentration of hypochlorite and hydrogen peroxide and has a good linearity in the range of 250-2250 nM and 60-180 μM with a detection limit of 3.676 nM and 0.602 μM, respectively. Based on the previously described advantages, PCDs have potential as a biomedicine.

A MnO2 nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots and o-phenylenediamine for determination of 6-mercaptopurine

A MnO₂ nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots (CQDs) and o-phenylenediamine (OPD) has been developed for the detection of the anticancer drug 6-mercaptopurine (6-MP). CQDs with strong fluorescence are synthesized via the one-step hydrothermal method. MnO₂ nanosheets as an oxidase-mimicking nanomaterial directly oxidize OPD into 2,3-diaminophenazine (DAP) which has a fluorescence emission at 570 nm, whereas the fluorescence of CQDs at 445 nm is then reduced by the DAP through the inner filter effect (IFE) under a single excitation wavelength (370 nm). After adding 6-MP, MnO₂ nanosheets can be reduced to Mn²⁺ and lose their oxidase-like property, blocking the IFE with the fluorescence decrease of DAP and fluorescence increase of CQDs. The novel ratiometric fluorescence probe exhibits considerable sensitivity toward 6-MP and linear response is in the 0.46-100.0 μmol L^-1 concentration range with the detection limit of 0.14 μmol L^-1. Furthermore, the probe shows good selectivity when exposed to a series of interfering other organic and inorganic compounds, and biomolecules and can be applied to the detection for 6-MP in human serum samples and pharmaceutical tablets. Satisfactory recoveries of 6-MP in human serum samples are in the range 96.1-110.9% with the RSD of 1.4 to 3.2%. The amount of 6-MP is successfully estimated as 49.3 mg in pharmaceutical tablet with the RSD of about  2.2%.

Application of phototherapeutic-based nanoparticles in colorectal cancer

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the second leading cause of cancer death, which accounts for approximately 10% of all new cancer cases worldwide. Surgery is the main method for treatment of early-stage CRC. However, it is not effective for most metastatic tumors, and new treatment and diagnosis strategies need to be developed. Photosensitizers (PSs) play an important role in the treatment of CRC. Phototherapy also has a broad prospect in the treatment of CRC because of its low invasiveness and low toxicity. However, most PSs are associated with limitations including poor solubility, poor selectivity and high toxicity. The application of nanomaterials in PSs has added many advantages, including increased solubility, bioavailability, targeting, stability and low toxicity. In this review, based on phototherapy, we discuss the characteristics and development progress of PSs, the targeting of PSs at organ, cell and molecular levels, and the current methods of optimizing PSs, especially the application of nanoparticles as carriers in CRC. We introduce the photosensitizer (PS) targeting process in photodynamic therapy (PDT), the damage mechanism of PDT, and the application of classic PS in CRC. The action process and damage mechanism of photothermal therapy (PTT) and the types of ablation agents. In addition, we present the imaging examination and the application of PDT / PTT in tumor, including (fluorescence imaging, photoacoustic imaging, nuclear magnetic resonance imaging, nuclear imaging) to provide the basis for the early diagnosis of CRC. Notably, single phototherapy has several limitations in vivo, especially for deep tumors. Here, we discuss the advantages of the combination therapy of PDT and PTT compared with the single therapy. At the same time, this review summarizes the clinical application of PS in CRC. Although a variety of nanomaterials are in the research and development stage, few of them are actually on the market, they will show great advantages in the treatment of CRC in the near future.

Noninvasive and real-time monitoring of Au nanoparticle promoted cancer metastasis using in vivo flow cytometry

Cancer is the second leading cause of mortality globally, while cancer metastasis, which accounts for about 90% of cancer-related mortality, presents an extremely poor prognosis. Thus, various nanomedicines were designed and synthesized for cancer treatment, but nanomaterials could lead to endothelial leakiness and consequently facilitate intravasation and extravasation of cancer cells to form circulating tumor cells (CTCs), which were regarded as the potential metastatic seeds, possibly accelerating cancer metastasis. Neither possible metastatic sites were observed nor rare CTCs could be measured using common methods at the early stage of cancer metastasis, it is urgent to explore new technology to dynamically monitor nanomedicine promoted cancer metastasis with high sensitivity, which would be beneficial for cancer treatment as well as design and synthesis of nanomedicine. Herein, a novel optical biopsy tool i.e. in vivo flow cytometry (IVFC) was constructed to noninvasively and real-time monitor CTCs of tumor-bearing mice treated with various concentrations of Au nanoparticles. The in vivo experimental results demonstrated the promoted CTCs were Au nanoparticles dose-dependent consistent with the in vitro results, which showed Au nanoparticles induced dose-dependent gaps in the blood vessel endothelial walls to accelerate CTCs formation, making IVFC a promising biopsy tool in fundamental, pre-clinical and clinical investigation of nanomedicine and cancer metastasis.

NIR-quantum dots in biomedical imaging and their future

Fluorescence imaging has gathered interest over the recent years for its real-time response and high sensitivity. Developing probes for this modality has proven to be a challenge. Quantum dots (QDs) are colloidal nanoparticles that possess unique optical and electronic properties due to quantum confinement effects, whose excellent optical properties make them ideal for fluorescence imaging of biological systems. By selectively controlling the synthetic methodologies it is possible to obtain QDs that emit in the first (650-950 nm) and second (1000-1400 nm) near infra-red (NIR) windows, allowing for superior imaging properties. Despite the excellent optical properties and biocompatibility shown by some NIR QDs, there are still some challenges to overcome to enable there use in clinical applications. In this review, we discuss the latest advances in the application of NIR QDs in preclinical settings, together with the synthetic approaches and material developments that make NIR QDs promising for future biomedical applications.