Visible-light-driven dynamic cancer therapy and imaging using graphitic carbon nitride nanoparticles

Efficient Strategies to Use β-Cationic Porphyrin-Imidazolium Derivatives in the Photoinactivation of Methicillin-Resistant Staphylococcus aureus

Bacterial resistance to antibiotics is a critical global health issue and the development of alternatives to conventional antibiotics is of the upmost relevance. Antimicrobial photodynamic therapy (aPDT) is considered a promising and innovative approach for the photoinactivation of microorganisms, particularly in cases where traditional antibiotics may be less effective due to resistance or other limitations. In this study, two β-modified monocharged porphyrin-imidazolium derivatives were efficiently incorporated into polyvinylpyrrolidone (PVP) formulations and supported into graphitic carbon nitride materials. Both porphyrin-imidazolium derivatives displayed remarkable photostability and the ability to generate cytotoxic singlet oxygen. These properties, which have an important impact on achieving an efficient photodynamic effect, were not compromised after incorporation/immobilization. The prepared PVP-porphyrin formulations and the graphitic carbon nitride-based materials displayed excellent performance as photosensitizers to photoinactivate methicillin-resistant Staphylococcus aureus (MRSA) (99.9999% of bacteria) throughout the antimicrobial photodynamic therapy. In each matrix, the most rapid action against S. aureus was observed when using PS 2. The PVP-2 formulation needed 10 min of exposure to white light at 5.0 µm, while the graphitic carbon nitride hybrid GCNM-2 required 20 min at 25.0 µm to achieve a similar level of response. These findings suggest the potential of graphitic carbon nitride-porphyrinic hybrids to be used in the environmental or clinical fields, avoiding the use of organic solvents, and might allow for their recovery after treatment, improving their applicability for bacteria photoinactivation.

The direct catalytic synthesis of ultrasmall Cu2O-coordinated carbon nitrides on ceria for multimodal antitumor therapy

Engineering chem-/sono-/photo-multimodal antitumor therapies has become an efficient strategy to combat malignant tumors. However, the existence of hypoxia in the tumor microenvironment (TME) leads to limited sonodynamic or photodynamic efficiency because O₂ is the key reactant during the process of generation of reactive oxygen species (ROS). Here, to design a desirable platform that can simultaneously convert H₂O₂ in the TME into ROS and O₂ for efficient chem-/sono-/photo-multimodal tumor therapies, we have created ultrasmall Cu₂O-coordinated carbon nitride on a biocompatible ceria substrate (denoted as Cu₂O-CN_x@CeO₂) via a self-assisted catalytic growth strategy. The chemical and morphological structures, ROS and O₂ generation activities, and chemo-/photo-/sono-dynamic specificities of Cu₂O-CN_x@CeO₂ when serving as multifunctional biocatalytic agents were systematically disclosed. The experimental studies validated that Cu₂O-CN_x@CeO₂ presents state-of-the-art peroxidase-like and catalase-like activities. Moreover, the light excitation and ultrasound irradiation were also demonstrated to boost ROS production. The in vitro and in vivo experiments suggest that Cu₂O-CN_x@CeO₂ can efficiently inhibit the growth of malignant melanoma via chem-/sono-/photo-multimodal antitumor ability. We believe that applying these new biocatalysts with dual catalytic activities of producing ROS and O₂ will offer a new path for engineering multimodal nanoagents to combat malignant tumors.

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.

Nanoparticle Systems for Cancer Phototherapy: An Overview

Photodynamic therapy (PDT) and photothermal therapy (PTT) are photo-mediated treatments with different mechanisms of action that can be addressed for cancer treatment. Both phototherapies are highly successful and barely or non-invasive types of treatment that have gained attention in the past few years. The death of cancer cells because of the application of these therapies is caused by the formation of reactive oxygen species, that leads to oxidative stress for the case of photodynamic therapy and the generation of heat for the case of photothermal therapies. The advancement of nanotechnology allowed significant benefit to these therapies using nanoparticles, allowing both tuning of the process and an increase of effectiveness. The encapsulation of drugs, development of the most different organic and inorganic nanoparticles as well as the possibility of surfaces' functionalization are some strategies used to combine phototherapy and nanotechnology, with the aim of an effective treatment with minimal side effects. This article presents an overview on the use of nanostructures in association with phototherapy, in the view of cancer treatment.

Determination of VEGF165 using impedimetric aptasensor based on cyclohexanehexone-melem covalent-organic framework

A porous nanostructured covalent-organic framework (COF) has been prepared via condensation polymerization between the two building blocks of melem and hexaketocyclohexane octahydrate (represented as M-HO-COF). Basic characterizations revealed that the M-HO-COF network was composed of C=N and highly conjugated aromatic moieties, along with a high surface area, large pore size, remarkable electrochemical activity, and strong bioaffinity toward aptamer strands. Given that the vascular endothelial growth factor 165 (VEGF₁₆₅)-targeted aptamer was stably anchored over M-HO-COF via weak intermolecular forces, the prepared M-HO-COF network exhibited great potential as a sensitive and selective platform for the impedimetric VEGF₁₆₅ aptasensor. Consequently, the M-HO-COF-based aptasensor displayed an ultralow limit of detection of 0.18 fg mL^-1 within a wide range of VEGF₁₆₅ concentrations from 1 fg mL^-1 to 10 ng mL^-1. Considering its strong fluorescence performance, excellent biocompatibility, and small nanosheet-like structure, the obtained COF-based aptasensor showed a superior sensing performance and regeneration capability after 7 regeneration cycles for the detection of osteosarcoma cells (K7M2 cells), which overexpressed with VEGF₁₆₅, with a low limit of detection of 49 cells mL^-1. For real f human serum samples, the obtained COF-based aptasensor exhibits acceptable mean apparent recoveries of 97.41% with a relative standard deviation of 4.60%. Furthermore, the proposed bifunctional aptasensor for the detection VEGF₁₆₅ and K7M2 cells exhibited good stability, appropriate selectivity toward other biomarkers or normal cells, acceptable reproducibility, and applicability. A bifunctional sensing system was constructed for detecting osteosarcoma cells (K7M2 cells) and VEGF₁₆₅ based on the a porous nanostructured covalent-organic framework (M-HO-COF) via condensation polymerization between melem and hexaketocyclohexane octahydrate. The M-HO-COF-based aptasensor displayed ultralow detection limit of 0.18 fg mL^-1 toward VEGF₁₆₅ and 49 cell mL^-1 for K7M2 cells with high selectivity, acceptable reproducibility, and good stability.

3-Amino-1,2,4-triazole-derived graphitic carbon nitride for photodynamic therapy

Graphitic carbon nitride (g-C₃N₄) has been shown as a promising visible-light photosensitizer for photodynamic therapy (PDT) application. Nevertheless, its therapeutic efficiency is limited by the low efficiency of visible-light utilization. To overcome this issue, 3-amino-1,2,4-triazole-derived graphitic carbon nitride nanosheets (g-C₃N₅ NSs) are prepared for PDT application. The addition of nitrogen-rich triazole group into the g-C₃N₄ motif significantly makes the light absorption of g-C₃N₅ NSs red-shift with the band gap down to 1.95 eV, corresponding to a absorption edge at a wavelength of 636 nm. g-C₃N₅ NSs generate superoxide anion radicals (O₂^•-) and singlet oxygen (¹O₂) under the irradiation of a low-intensity white light emitting diode. Owing to the high efficiency of visible-light utilization, g-C₃N₅ NSs show about 9.5 fold photocatalytic activity of g-C₃N₄ NSs. In vitro anticancer studies based on the results of CCK-8 assay, Calcein-AM/PI cell-survival assay and photo-induced intracellular ROS level analysis in living HeLa cells demonstrate the potential of g-C₃N₅ NSs as a low-toxic and biocompatible high-efficient photosensitizer for PDT.

Intense Pulsed Light Attenuates UV-Induced Hyperimmune Response and Pigmentation in Human Skin Cells

The skin of an organism is affected by various environmental factors and fights against aging stress via mechanical and biochemical responses. Photoaging induced by ultraviolet B (UVB) irradiation is common and is the most vital factor in the senescence phenotype of skin, and so, suppression of UVB stress-induced damage is critical. To lessen the UVB-induced hyperimmune response and hyperpigmentation, we investigated the ameliorative effects of intense pulsed light (IPL) treatment on the photoaged phenotype of skin cells. Normal human epidermal keratinocytes and human epidermal melanocytes were exposed to 20 mJ/cm² of UVB. After UVB irradiation, the cells were treated with green (525–530 nm) and yellow (585–592 nm) IPL at various time points prior to the harvest step. Subsequently, various signs of excessive immune response, including expression of proinflammatory and melanogenic genes and proteins, cellular oxidative stress level, and antioxidative enzyme activity, were examined. We found that IPL treatment reduced excessive cutaneous immune reactions by suppressing UVB-induced proinflammatory cytokine expression. IPL treatment prevented hyperpigmentation, and combined treatment with green and yellow IPL synergistically attenuated both processes. IPL treatment may exert protective effects against UVB injury in skin cells by attenuating inflammatory cytokine and melanogenic gene overexpression, possibly by reducing intracellular oxidative stress. IPL treatment also preserves antioxidative enzyme activity under UVB irradiation. This study suggests that IPL treatment is a useful strategy against photoaging, and provides evidence supporting clinical approaches with non-invasive light therapy.

A multifunctional nanoplatform based on graphitic carbon nitride quantum dots for imaging-guided and tumor-targeted chemo-photodynamic combination therapy

Graphitic carbon nitride quantum dots (g-CNQDs) have shown great potential in imaging, drug delivery and photodynamic therapy (PDT). However, relevant research on g-CNQDs for PDT or drug delivery has been conducted separately. Herein, we develop a g-CNQDs-based nanoplatform (g-CPFD) to achieve simultaneously imaging and chemo-photodynamic combination therapy in one system. A g-CNQDs-based nanocarrier (g-CPF) is first prepared by successively introducing carboxyamino-terminated oligomeric polyethylene glycol and folic acid onto the surface of g-CNQDs via two-step amidation. The resultant g-CPF possesses good physiological stability, strong blue fluorescence, desirable biocompatibility, and visible light-stimulated reactive oxygen species generating ability. Further non-covalently loaded doxorubicin enables the system with chemotherapy function. Compared with free doxorubicin, g-CPFD expresses more efficient chemotherapy to HeLa cells due to improved folate receptor-mediated cellular uptake and intracellular pH-triggered drug release. Furthermore, g-CPFD under visible light irradiation shows enhanced inhibition on the growth of cancer cells compared to sole chemotherapy or PDT. Thus, g-CPFD exhibits exceptional anti-tumor efficiency due to folate receptor-mediated targeting ability, intracellular pH-triggered drug release and a combined treatment effect arising from PDT and chemotherapy. Moreover, this nanoplatform benefits imaging-guided drug delivery because of inherent fluorescent properties of doxorubicin and g-CPF, hence achieving the goal of imaging-guided chemo-photodynamic combination treatments.

Rosette-shaped graphitic carbon nitride acts as a peroxidase mimic in a wide pH range for fluorescence-based determination of glucose with glucose oxidase

Rosette-shaped graphitic carbon nitride (rosette-GCN) is described as a promising alternative to natural peroxidase for its application to fluorescence-based glucose assays. Rosette-GCN was synthesized via a rapid reaction between melamine and cyanuric acid for 10 min at 35 °C, followed by thermal calcination for 4 h. Importantly, rosette-GCN possesses a peroxidase-like activity, producing intense fluorescence from the oxidation of Amplex UltraRed in the presence of H₂O₂ over a broad pH-range of, including neutral pH; the peroxidase activity of rosette-GCN was ~ 10-fold higher than that of conventional bulk-GCN. This enhancement of peroxidase activity is presumed to occur because rosette-GCN has a significantly larger surface area and higher porosity while preserving its unique graphitic structure. Based on the high peroxidase activity of rosette-GCN along with the catalytic action of glucose oxidase (GOx), glucose was reliably determined down to 1.2 μM with a dynamic linear concentration range of 5.0 to 275.0 μM under neutral pH conditions. Practical utility of this strategy was also successfully demonstrated by determining the glucose levels in serum samples. This work highlights the advantages of GCNs synthesized via rapid methods but with unique structures for the preparation of enzyme-mimicking catalysts, thus extending their applications to the diagnostics field and other biotechnological fields. Graphical abstract.

Photocatalytically Active Graphitic Carbon Nitride as an Effective and Safe 2D Material for In Vitro and In Vivo Photodynamic Therapy

Thanks to its photocatalytic property, graphitic carbon nitride (g-C₃ N₄ ) is a promising candidate in various applications including nanomedicine. However, studies focusing on the suitability of g-C₃ N₄ for cancer therapy are very limited and possible underlying molecular mechanisms are unknown. Here, it is demonstrated that photoexcitation of g-C₃ N₄ can be used effectively in photodynamic therapy, without using any other carrier or additional photosensitizer. Upon light exposure, g-C₃ N₄ treatment kills cancer cells, without the need of any other nanosystem or chemotherapeutic drug. The material is efficiently taken up by tumor cells in vitro. The transcriptome and proteome of g-C₃ N₄ and light treated cells show activation in pathways related to both oxidative stress, cell death, and apoptosis which strongly suggests that only when combined with light exposure, g-C₃ N₄ is able to kill cancer cells. Systemic administration of the mesoporous form results in elimination from urinary bladder without any systemic toxicity. Administration of the material significantly decreases tumor volume when combined with local light treatment. This study paves the way for the future use of not only g-C₃ N₄ but also other 2D nanomaterials in cancer therapy.

Highly sensitive detection of CTLA-4-positive T-cell subgroups based on nanobody and fluorescent carbon quantum dots

The detection of cytotoxic T-lymphocyte antigen-4-positive (CTLA-4⁺) T-cell subgroups in peripheral blood samples and tumor tissues is of great significance. In the present study, a rapid, succinct and efficient method was designed for the detection of CTLA-4⁺ human T cells using a CTLA-4-specific nanobody-fluorescent carbon quantum dots complex (QDs-Nb36). QDs-Nb36 was used for high sensitivity detection of CTLA-4⁺ T cells by flow cytometry or immumofluorescent staining. The present study demonstrated that the novel technique was more specific and effective in the detection of CTLA-4⁺ T-cell ratio in the peripheral blood and tumor tissues compared with a traditional monoclonal antibody approach. Furthermore, no significant toxicity was identified in vitro and in vivo, thus suggesting that the method may have broad applications for the detection of certain lowly expressed targets.

Mitochondria and Nuclei Dual-Targeted Hollow Carbon Nanospheres for Cancer Chemophotodynamic Synergistic Therapy

Dual-targeted nanoparticles are gaining increasing importance as a more effective anticancer strategy by attacking double key sites of tumor cells, especially in chemophotodynamic therapy. To retain the nuclei inhibition effect and enhance doxorubicin (DOX)-induced apoptosis by mitochondrial pathways simultaneously, we synthesized the novel nanocarrier (HKH) based on hollow carbon nitride nanosphere (HCNS) modified with hyaluronic acid (HA) and the mitochondrial localizing peptide D[KLAKLAK]2 (KLA). DOX-loaded HKH nanoparticles (HKHDs) showed satisfactory drug-loading efficiency, excellent solubility, and very low hemolytic effect. HA/CD44 binding and electrostatic attraction between positively charged KLA and A549 cells facilitated HKHD uptake via the endocytosis mechanism. Acidic microenvironment, hyaluronidase, and KLA targeting together facilitate doxorubicin toward the mitochondria and nuclei, resulting in apoptosis, DNA intercalation, cell-cycle arrest at the S phase, and light-induced reactive oxygen species production. Intravascular HKHD inhibited tumor growth in A549-implanted mice with good safety. The present study, for the first time, systemically reveals biostability, targetability, chemophotodynamics, and safety of the functionalized novel HKHD.

Synthesis and biomedical applications of graphitic carbon nitride quantum dots

This review summarizes the synthetic methods and addresses current applications and future perspectives of graphitic carbon nitride quantum dots in the biomedical field.

Graphitic carbon nitride nanosheets as a multifunctional nanoplatform for photochemical internalization-enhanced photodynamic therapy

Photodynamic therapy (PDT) has been widely used as a noninvasive and moderate technique in precision cancer therapy by destroying cancer cells via light-induced reactive oxygen species (ROS). However, the overproduction of heat shock protein 70 (HSP70) induced by ROS will contribute to the cell survival under harsh conditions, finally leading to decreased PDT efficiency. To overcome this issue, herein, for the first time, we have prepared an HSP70 inhibitor (2-phenylethynesulfonamide (PES))-loaded graphitic carbon nitride nanosheet (GCNS) as a multifunctional nanoplatform (GCNS-PES) for enhanced PDT. By taking advantage of commendable PDT efficiency, strong blue fluorescence, satisfactory drug loading capacity and good water dispersity, the GCNS can simultaneously serve as a photosensitizer, an imaging agent and a drug carrier. Moreover, when the nanoplatform is restricted in the endo/lysosome vesicles through endocytosis, the GCNS can generate ROS effectively under visible light irradiation to promote the lipid peroxidation of endo/lysosomal membranes and accelerate the liberation of GCNS and PES into the cytoplasm. Finally, the tolerance of cancer cells to ROS is decreased by PES-induced HSP70 inactivation, and therefore the efficiency of PDT is significantly enhanced. As a result, GCNS-PES can serve as a promising therapeutic nanoplatform for photo-controlled cancer therapy.