Exploration of Graphitic-C3N4 Quantum Dots for Microwave-Induced Photodynamic Therapy

Quantum dots for bone tissue engineering

In confronting the global prevalence of bone-related disorders, bone tissue engineering (BTE) has developed into a critical discipline, seeking innovative materials to revolutionize treatment paradigms. Quantum dots (QDs), nanoscale semiconductor particles with tunable optical properties, are at the cutting edge of improving bone regeneration. This comprehensive review delves into the multifaceted roles that QDs play within the realm of BTE, emphasizing their potential to not only revolutionize imaging but also to osteogenesis, drug delivery, antimicrobial strategies and phototherapy. The customizable nature of QDs, attributed to their size-dependent optical and electronic properties, has been leveraged to develop precise imaging modalities, enabling the visualization of bone growth and scaffold integration at an unprecedented resolution. Their nanoscopic scale facilitates targeted drug delivery systems, ensuring the localized release of therapeutics. QDs also possess the potential to combat infections at bone defect sites, preventing and improving bacterial infections. Additionally, they can be used in phototherapy to stimulate important bone repair processes and work well with the immune system to improve the overall healing environment. In combination with current trendy artificial intelligence (AI) technology, the development of bone organoids can also be combined with QDs. While QDs demonstrate considerable promise in BTE, the transition from laboratory research to clinical application is fraught with challenges. Concerns regarding the biocompatibility, long-term stability of QDs within the biological environment, and the cost-effectiveness of their production pose significant hurdles to their clinical adoption. This review summarizes the potential of QDs in BTE and highlights the challenges that lie ahead. By overcoming these obstacles, more effective, efficient, and personalized bone regeneration strategies will emerge, offering new hope for patients suffering from debilitating bone diseases.

Emerging Roles of Graphitic Carbon Nitride-based Materials in Biomedical Applications

Graphite carbon nitride (g-C3N4) is a two-dimensional conjugated polymer with a unique energy band structure similar to graphene. Due to its outstanding analytical advantages, such as relatively small band gap (2.7 eV), low-cost synthesis, high thermal stability, excellent photocatalytic ability, and good biocompatibility, g-C3N4 has attracted the interest of researchers and industry, especially in the medical field. This paper summarizes the latest research on g-C3N4-based composites in various biomedical applications, including therapy, diagnostic imaging, biosensors, antibacterial, and wearable devices. In addition, the application prospects and possible challenges of g-C3N4 in nanomedicine are also discussed in detail. This review is expected to inspire emerging biomedical applications based on g-C3N4.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

Nanocatalysts for modulating antitumor immunity: fabrication, mechanisms and applications

Immunotherapy harnesses the inherent immune system in the body to generate systemic antitumor immunity, offering a promising modality for defending against cancer. However, tumor immunosuppression and evasion seriously restrict the immune response rates in clinical settings. Catalytic nanomedicines can transform tumoral substances/metabolites into therapeutic products in situ, offering unique advantages in antitumor immunotherapy. Through catalytic reactions, both tumor eradication and immune regulation can be simultaneously achieved, favoring the development of systemic antitumor immunity. In recent years, with advancements in catalytic chemistry and nanotechnology, catalytic nanomedicines based on nanozymes, photocatalysts, sonocatalysts, Fenton catalysts, electrocatalysts, piezocatalysts, thermocatalysts and radiocatalysts have been rapidly developed with vast applications in cancer immunotherapy. This review provides an introduction to the fabrication of catalytic nanomedicines with an emphasis on their structures and engineering strategies. Furthermore, the catalytic substrates and state-of-the-art applications of nanocatalysts in cancer immunotherapy have also been outlined and discussed. The relationships between nanostructures and immune regulating performance of catalytic nanomedicines are highlighted to provide a deep understanding of their working mechanisms in the tumor microenvironment. Finally, the challenges and development trends are revealed, aiming to provide new insights for the future development of nanocatalysts in catalytic immunotherapy.

Recent Advances in Chemistry, Mechanism, and Applications of Quantum Dots in Photodynamic and Photothermal Therapy

Semiconductor quantum dots (QD) are a kind of nanoparticle with unique optical properties that have attracted a lot of attention in recent years. In this paper, the characteristics of these nanoparticles and their applications in nanophototherapy have been reviewed. Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), has gained special importance because of its high accuracy and local treatment due to the activation of the drug at the tumor site. PDT is a new way of cancer treatment that is performed by activating light-sensitive compounds named photosensitizers (PS) by light. PSs cause the destruction of diseased tissue through the production of singlet oxygen. PTT is another non-invasive method that induces cell death through the conversion of near-infrared light (NIR) into heat in the tumor situation by the photothermal agent (PA). Through using energy transfer via the FRET (Förster resonance energy transfer) process, QDs provide light absorption wavelength for both methods and cover the optical weaknesses of phototherapy agents.

B, P, and S heteroatom doped, bio- and hemo-compatible 2D graphitic-carbon nitride (g-C3N4) with antioxidant, light-induced antibacterial, and bioimaging endeavors

The synthesis of two-dimensional (2D) graphiticg-C3N4and heteroatom-doped graphitic H@g-C3N4(H: B, P, or S) particles were successfully done using melamine as source compounds and boric acid, phosphorous red, and sulfur as doping agents. The band gap values of 2Dg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures were determined as 2.90, 3.03, 2.89, and 2.93 eV, respectively. The fluorescent emission wavelengths of 2Dg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures were observed at 442, 430, 441, and 442 nm, respectively upon excitation atλEx= 325 nm. There is also one additional new emission wavelength was found at 345 nm for B50@g-C3N4structure. The blood compatibility test results ofg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures revealed that all materials are blood compatible with <2% hemolysis and >90% blood clotting indices at 100μg ml-1concentration. The cell toxicity of the prepared 2D graphitic structures were also tested on L929 fibroblast cells, and even the heteroatom doped hasg-C3N4structures induce no cytotoxicity was observed with >91% cell viability even at 250μg ml-1particle concentration with the exception of P50@g-C3N4which as >75 viability. Moreover, for 2Dg-C3N4, B50@g-C3N4, and S50@g-C3N4constructs, even at 500μg ml-1concentration, >90% cell viabilities was monitored. As a diagnostic material, B50@g-C3N4was found to have significantly high penetration and distribution abilities into L929 fibroblast cells granting a great potential in fluorescence imaging and bioimaging applications. Furthermore, the elemental doping with B, P, and S ofg-C3N4were found to significantly increase the photodynamic antibacterial activity e.g. more than half of bacterial elimination by heteroatom-doped forms ofg-C3N4under UVA treatment was achieved.

Emerging Graphitic Carbon Nitride-based Nanobiomaterials for Biological Applications

Graphitic carbon nitride (g-CN) based nanostructures are distinctive materials with unique compositional, structural, optical, and electronic properties with exceptional band structure, moderate surface area, and exceptional thermal and chemical stability. Because of these properties, g-CN based nanomaterials have shown promising applications and higher performance in the biological avenue. This review covers the state-of-the-art synthetic strategies used for the preparation of the materials, the basic structure, and a panorama of different optimization strategies leading to improved physicochemical properties responsible for the biological application. The following sections include the recent progress in the use of g-CN based nanobiomaterials for biosensors, bioimaging, photodynamic therapy, drug delivery, chemotherapy, and the antimicrobial segment. Furthermore, we have summarized the role and evaluation of biosafety and biocompatibility of the material. Finally, the unresolved issues, plausible challenges, current status, and future perspectives for the development and design of g-CN have been summarized and are expected to promote a clinical path for the medical sector and human well-being.

Mn-doped Ti-based MOFs for magnetic resonance imaging-guided synergistic microwave thermal and microwave dynamic therapy of liver cancer

Currently, precise ablation of tumors without damaging the surrounding normal tissue is still an urgent problem for clinical microwave therapy of liver cancer. Herein, we synthesized Mn-doped Ti MOFs (Mn–Ti MOFs) nanosheets by in-situ doping method and applied them for microwave therapy. Infrared thermal imaging results indicate Mn–Ti MOFs can rapidly increase the temperature of normal saline, attributing to the porous structure improving microwave-induced ion collision frequency. Moreover, Mn–Ti MOFs show higher ¹O₂ output than Ti MOFs under 2 W of low-power microwave irradiation due to the narrower band-gap after Mn doping. At the same time, Mn endows the MOFs with a desirable T₁ contrast of magnetic resonance imaging (r₂/r₁ = 2.315). Further, results on HepG2 tumor-bearing mice prove that microwave-triggered Mn–Ti MOFs nearly eradicate the tumors after 14 days of treatment. Our study offers a promising sensitizer for synergistic microwave thermal and microwave dynamic therapy of liver cancer.

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Mn-doped Ti-MOFs nanosheets (Mn–Ti MOFs) were synthesized as novel microwave sensitizers.

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Mn–Ti MOFs can significantly generate heat and produce ROS under low-power microwave irradiation.

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The combination of microwave thermal therapy and microwave dynamic therapy can effectively inhibit the growth of tumor cells in vitro and in vivo.

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The microwave sensitizers have potential application in MRI-guided microwave therapy for liver cancer.

Copper-cysteamine nanoparticle-mediated microwave dynamic therapy improves cancer treatment with induction of ferroptosis

Photodynamic Therapy (PDT) holds a great promise for cancer patients, however, due to the hypoxic characteristics of most solid tumors and the limited penetration depth of light in tissues, the extensive clinical application of PDT is limited. Herein, we report microwave induced copper-cysteamine (Cu-Cy) nanoparticles-based PDT as a promising cancer treatment to overcome cancer resistance in combination with ferroptosis. The treatment efficiency of Cu-Cy-mediated microwave dynamic therapy (MWDT) tested on HCT15 colorectal cancer (CRC) cells via cell titer-blue cell viability assay and live/dead assay reveal that Cu-Cy upon MW irradiation can effectively destroy HCT15 CRC cells with average IC-50 values of 20 μg/mL. The cytotoxicity of Cu-Cy to tumor cells after MW stimulation can be alleviated by ferroptosis inhibitor. Furthermore, Cu-Cy mediated MWDT could deplete glutathione peroxide 4 (GPX4) and enhance lipid peroxides (LPO) and malondialdehyde (MDA). Our findings demonstrate that MW-activated Cu-Cy killed CRC cells by inducing ferroptosis. The superior in vivo antitumor efficacy of the Cu-Cy was corroborated by a HCT15 tumor-bearing mice model. Immunohistochemical experiments showed that the GPX4 expression level in Cu-Cy + MW group was significantly lower than that in other groups. Overall, these findings demonstrate that Cu-Cy nanoparticles have a safe and promising clinical application prospect in MWDT for deep-seated tumors and effectively inhibit tumor cell proliferation by inducing ferroptosis, which provides a potential solution for cancer resistance.

Enhanced Photodynamic Therapy: A Review of Combined Energy Sources

Photodynamic therapy (PDT) has been used in recent years as a non-invasive treatment for cancer, due to the side effects of traditional treatments such as surgery, radiotherapy, and chemotherapy. This therapeutic technique requires a photosensitizer, light energy, and oxygen to produce reactive oxygen species (ROS) which mediate cellular toxicity. PDT is a useful non-invasive therapy for cancer treatment, but it has some limitations that need to be overcome, such as low-light-penetration depths, non-targeting photosensitizers, and tumor hypoxia. This review focuses on the latest innovative strategies based on the synergistic use of other energy sources, such as non-visible radiation of the electromagnetic spectrum (microwaves, infrared, and X-rays), ultrasound, and electric/magnetic fields, to overcome PDT limitations and enhance the therapeutic effect of PDT. The main principles, mechanisms, and crucial elements of PDT are also addressed.

A Hypoxia-Activated Prodrug Conjugated with a BODIPY-Based Photothermal Agent for Imaging-Guided Chemo-Photothermal Combination Therapy

Hypoxia-activated prodrugs (HAPs) have drawn increasing attention for improving the antitumor effects while minimizing side effects. However, the heterogeneous distribution of the hypoxic region in tumors severely impedes the curative effect of HAPs. Additionally, most HAPs are not amenable to optical imaging, and it is difficult to precisely trace them in tissues. Herein, we carefully designed and synthesized a multifunctional therapeutic BAC prodrug by connecting the chemotherapeutic drug camptothecin (CPT) and the fluorescent photothermal agent boron dipyrromethene (BODIPY) via hypoxia-responsive azobenzene linkers. To enhance the solubility and tumor accumulation, the prepared BAC was further encapsulated into a human serum albumin (HSA)-based drug delivery system to form HSA@BAC nanoparticles. Since the CPT was caged by a BODIPY-based molecule at the active site, the BAC exhibited excellent biosafety. Importantly, the activated CPT could be quickly released from BAC and could perform chemotherapy in hypoxic cancer cells, which was ascribed to the cleavage of the azobenzene linker by overexpressed azoreductase. After irradiation with a 730 nm laser, HSA@BAC can efficiently generate hyperthermia to achieve irreversible cancer cell death by oxygen-independent photothermal therapy. Under fluorescence imaging-guided local irradiation, both in vitro and in vivo studies demonstrated that HSA@BAC exhibited superior antitumor effects with minimal side effects.

Rational design of a small organic photosensitizer for NIR-I imaging-guided synergistic photodynamic and photothermal therapy

Developing a small molecular photosensitizer to achieve multimodal phototherapy has recently garnered attention as a promising strategy for efficient cancer treatment. However, synthesis of a multifunctional small molecular photosensitizer has remained challenging. Here we report an aggregation-induced-emission (AIE)-featured luminogen (AIEgen) TPA-BTZ decorated with long and branched alkyl chains. TPA-BTZ shows long-wavelength emission at ca. 800 nm in the NIR-I region. Moreover, upon laser irradiation, TPA-BTZ could produce O₂˙^- and ¹O₂via both type I and type II mechanisms for enhanced photodynamic therapy (PDT). The propeller-like structure triphenylamine (TPA) rotators not only endow TPA-BTZ with AIE characteristics but also facilitate heat generation by intramolecular rotation for photothermal therapy (PTT). More importantly, long and branched alkyl chains can create intermolecular spatial isolation in the fabricated TPA-BTZ@PEG2000 nanoparticles (NPs) to allow sufficient intramolecular motion for photothermal conversion. Due to these unique features, in vitro and in vivo evaluations demonstrate that the TPA-BTZ@PEG2000 NPs exhibited long-term NIR-imaging ability, superior tumoricidal activity, and suppressed tumor growth. This research provides new insights for developing new AIEgens for NIR imaging-guided multimodal phototherapy.

Self-Matrix N-Doped Room Temperature Phosphorescent Carbon Dots Triggered by Visible and Ultraviolet Light Dual Modes

The synthesis of room temperature phosphorescent carbon dots (RTP-CDs) without any matrix is important in various applications. In particular, RTP-CDs with dual modes of excitation are more interesting. Here, we successfully synthesized matrix-free carbonized polymer dots (CPDs) that can generate green RTP under visible and ultraviolet light dual-mode excitation. Using acrylic acid (AA) and ammonium oxalate as precursors, a simple one-pot hydrothermal method was selected to prepare AA-CPDs. Here, acrylic acid is easy to polymerize under high temperature and high pressure, which makes AA-CPDs form a dense cross-linked internal structure. Ammonium oxalate as a nitrogen source can form amino groups during the reaction, which reacts with a large number of pendant carboxyl groups on the polymer chains to further form a cross-linked structure. The carboxyl and amino groups on the surface of AA-CPDs are connected by intermolecular hydrogen bonds. These hydrogen bonds can provide space protection (isolation of oxygen) around the AA-CPDs phosphor, which can stably excite the triplet state. This self-matrix structure effectively inhibits the non-radiative transition by blocking the intramolecular motion of CPDs. Under the excitation of WLED and 365 nm ultraviolet light, AA-CPDs exhibit the phosphorescence emission at 464 nm and 476 nm, respectively. The naked-eye observation exceeds 5 s and 10 s, respectively, and the average lifetime at 365 nm excitation wavelength is as long as 412.03 ms. In addition, it successfully proved the potential application of AA-CPDs in image anti-counterfeiting.

Self-assembled Cupric Oxide Nanoclusters for Highly efficient chemodynamic therapy

Chemodynamic therapy (CDT) based on Fenton and Fenton-like reactions induces cancer cell killing via in situ catalyzing H₂ O₂ and generating highly oxidative hydroxyl radicals (⋅OH) in tumor sites. Their application is not limited by tumor grown depth or hypoxic microenvironment. However, the reaction efficiency is still hampered due to the structure of catalytic agents and the requirement for low pH environment. Here, we design a porous CuO nanocluster (CuO NC) through self-assembly of oleylamine stabilized CuO NPs (OAm-CuO NPs), and functionalize it with folic acid (CuO NC-FA) for specific tumor cell targeting. It can catalyze H₂ O₂ with high efficiency in nearly neutral environment. Besides, the porous structure of CuO NC also helps the diffusion of H₂ O₂ to the interior of nanocluster to further improve Fenton-like reaction efficiency. The convenient synthesis of CuO NC-FA with good Fenton-like reaction efficiency at neutral environment demonstrates good chemodynamic therapy effect.

Tuning Multicolor Emission of Manganese-Activated Gallogermanate Nanophosphors by Regulating Mn Ions Occupying Sites for Multiple Anti-Counterfeiting Application

The ability to manipulate the luminescent color, intensity and long lifetime of nanophosphors is important for anti-counterfeiting applications. Unfortunately, persistent luminescence materials with multimode luminescent features have rarely been reported, even though they are expected to be highly desirable in sophisticated anti-counterfeiting. Here, the luminescence properties of Zn₃Ga₂GeO₈:Mn phosphors were tuned by using different preparation approaches, including a hydrothermal method and solid-state reaction approach combining with non-equivalent ion doping strategy. As a result, Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by a hydrothermal method demonstrate an enhanced red photoluminescence at 701 nm and a strong green luminescence with persistent luminescence and photostimulated luminescence at 540 nm. While Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by solid-state reactions combined with a hetero-valent doping approach only exhibit an enhanced single-band red emission. Keeping the synthetic method unchanged, the substitution of hetero-valent dopant ion Li⁺ into different sites is valid for spectral fine-tuning. A spectral tuning mechanism is also proposed. Mn-activated Zn₃Ga₂GeO₈ phosphors synthesized by a hydrothermal approach with multimodal luminescence is especially suitable for multiple anti-counterfeiting, multicolor display and other potential applications.

Graphitic-phase C3N4 nanosheets combined with MnO2 nanosheets for sensitive fluorescence quenching detection of organophosphorus pesticides

In this study, we have developed a sensitive approach to measure organophosphorus pesticides (OPs) using graphitic-phase C₃N₄ nanosheets (g-C₃N₄) combined with a nanomaterial-based quencher, MnO₂ nanosheets (MnO₂ NS). Since MnO₂ NS can quench the fluorescence of g-C₃N₄ via the inner-filter effect (IFE), enzymatic hydrolysate (thiocholine, TCh) can efficiently trigger the decomposition of MnO₂ nanosheets in the presence of acetylcholinesterase (AChE) and acetylthiocholine (ATCh), resulting in the fluorescence recovery of g-C₃N₄. OPs, as inhibitors to AChE activity, can prevent the generation of TCh and decomposition of MnO₂ nanosheets while exhibiting fluorescence quenching. Therefore, the AChE-ATCh-MnO₂-g-C₃N₄ system can be utilized to quantitatively detect OPs based on g-C₃N₄ fluorescence. Under optimal conditions, the linear ranges for the determination of parathion-methyl (PM) and 2,2-dichlorovinyl dimethyl phosphate (DDVP) were found to be 0.1-2.1 ng/mL and 0.5-16 ng/mL, respectively, with limits of detection of 0.069 ng/mL and 0.20 ng/mL, respectively. The advantages of this assay are user-friendliness, ease of use, and cost effectiveness compared to other more sophisticated analytical instruments.

Colorectal liver metastasis: molecular mechanism and interventional therapy

Colorectal cancer (CRC) is one of the most frequently occurring malignancy tumors with a high morbidity additionally, CRC patients may develop liver metastasis, which is the major cause of death. Despite significant advances in diagnostic and therapeutic techniques, the survival rate of colorectal liver metastasis (CRLM) patients remains very low. CRLM, as a complex cascade reaction process involving multiple factors and procedures, has complex and diverse molecular mechanisms. In this review, we summarize the mechanisms/pathophysiology, diagnosis, treatment of CRLM. We also focus on an overview of the recent advances in understanding the molecular basis of CRLM with a special emphasis on tumor microenvironment and promise of newer targeted therapies for CRLM, further improving the prognosis of CRLM patients.

A tailored and red-emissive type I photosensitizer to potentiate photodynamic immunotherapy

Photodynamic immunotherapy (PDIT) emerges and shows great potentials in eradicating malignant tumors for the advantages on simultaneously damaging primary tumors, inhibiting tumors metastasis and recurrence. However, hypoxic microenvironment of tumor...

Aggregation-induced emission luminogens for highly effective microwave dynamic therapy

Aggregation-induced emission luminogens (AIEgens) exhibit efficient cytotoxic reactive oxygen species (ROS) generation capability and unique light-up features in the aggregated state, which have been well explored in image-guided photodynamic therapy (PDT). However, the limited penetration depth of light in tissue severely hinders AIEgens as a candidate for primary or adjunctive therapy for clinical applications. Coincidentally, microwaves (MWs) show a distinct advantage for deeper penetration depth in tissues than light. Herein, for the first time, we report AIEgen-mediated microwave dynamic therapy (MWDT) for cancer treatment. We found that two AIEgens (TPEPy-I and TPEPy-PF6) served as a new type of microwave (MW) sensitizers to produce ROS, including singlet oxygen (1O2), resulting in efficient destructions of cancer cells. The results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and live/dead assays reveal that the two AIEgens when activated by MW irradiation can effectively kill cancer cells with average IC-50 values of 2.73 and 3.22 μM, respectively. Overall, the ability of the two AIEgens to be activated by MW not only overcomes the limitations of conventional PDT, but also helps to improve existing MW ablation therapy by reducing the MW dose required to achieve the same therapeutic outcome, thus reducing the occurrence of side-effects of MW radiation.

Recent advances and trends in nanoparticles based photothermal and photodynamic therapy

Light-mediated therapies, including photodynamic therapy (PDT) and photothermal therapy (PTT) have been exploited as minimally invasive techniques for ablation of various tumors., Both modalities may eradicate tumors with minimal side effects to normal tissues and organs. Moreover, developments of light-mediated approaches using nanoparticles (NPs) and photosensitizer (PS) as diagnostic and therapeutic agents may have a crucial role in achieving successful cancer treatment. In recent years, novel nanoplatforms and strategies have been investigated to boost the therapeutic effect.. In this regard, gold, iron oxide, graphene oxide nanoparticles and hybrid nanocomposites have attracted attention.. Moreover, the combination of these materials with PS, in the form of hybrid NPs, reduces in vitro and in vivo normal tissue cytotoxicity, improves their solubility property in the biological environment and enhances the therapeutic effects. In this review, we look into the basic principles of PTT and PDT with their strengths and limitations to treat cancers. We also will discuss light-based nanoparticles and their PTT and PDT applications in the preclinical and clinical translation. Also, recent advances and trends in this field will be discussed along with the clinical challenges of PTT and PDT.

Carbon nitride nanomaterials with application in photothermal and photodynamic therapies

Phototherapies offer treatment of tumors with high spatial selectivity. Photodynamic therapy (PDT) consists in the administration of a photosensitizer (PS) followed by local photoirradiation with light of specific wavelength. The excited states of the PS interact with biomolecules and molecular oxygen producing reactive oxygen species (ROS), which initiate cell death. Photothermal therapy (PTT) employs photothermal agents to harvest the energy from light and convert it into heat to produce a temperature increase of the surrounding environment leading to cell death. Due to their good biocompatibility and unique photophysical properties, carbon-based materials are suitable for application in PDT and PTT. In particular, graphitic carbon nitride (g-C₃N₄), is a low-cost, non-toxic, and environment-friendly material, which is currently being used in the development of new nanomaterials with application in PDT and PTT. This brief review includes recent advances in the development of g-C₃N₄-based nanomaterials specifically designed for achieving red-shifted band gaps with the aim of generating oxygen molecules via water splitting upon red light or NIR irradiation to tackle the hypoxic condition of the tumor area. Nanomaterials designed for theranostics, combining medical imaging applications with PDT and/or PTT treatments are also included. The recent developments of g-C₃N₄-nanomaterials containing lanthanide-based upconversion nanoparticles are also covered. Finally, g-C₃N₄-based nanomaterials employed in microwave induced photodynamic therapy, sonodynamic therapy, and magnetic hyperthermia are considered.

Nanodots Derived from Layered Materials: Synthesis and Applications

Layered 2D materials, such as graphene, transition metal dichalcogenides, transition metal oxides, black phosphorus, graphitic carbon nitride, hexagonal boron nitride, and MXenes, have attracted intensive attention over the past decades owing to their unique properties and wide applications in electronics, catalysis, energy storage, biomedicine, etc. Further reducing the lateral size of layered 2D materials down to less than 10 nm allows for preparing a new class of nanostructures, namely, nanodots derived from layered materials. Nanodots derived from layered materials not only can exhibit the intriguing properties of nanodots due to the size confinement originating from the ultrasmall size, but also can inherit some unique properties of ultrathin layered 2D materials, making them promising candidates in a wide range of applications, especially in biomedicine and catalysis. Here, a comprehensive summary on the materials categories, advantages, synthesis methods, and potential applications of these nanodots derived from layered materials is provided. Finally, personal insights about the challenges and future directions in this promising research field are also given.

Two-dimensional biomaterials: material science, biological effect and biomedical engineering applications

To date, nanotechnology has increasingly been identified as a promising and efficient means to address a number of challenges associated with public health. In the past decade, two-dimensional (2D) biomaterials, as a unique nanoplatform with planar topology, have attracted explosive interest in various fields such as biomedicine due to their unique morphology, physicochemical properties and biological effect. Motivated by the progress of graphene in biomedicine, dozens of types of ultrathin 2D biomaterials have found versatile bio-applications, including biosensing, biomedical imaging, delivery of therapeutic agents, cancer theranostics, tissue engineering, as well as others. The effective utilization of 2D biomaterials stems from the in-depth knowledge of structure-property-bioactivity-biosafety-application-performance relationships. A comprehensive summary of 2D biomaterials for biomedicine is still lacking. In this comprehensive review, we aim to concentrate on the state-of-the-art 2D biomaterials with a particular focus on their versatile biomedical applications. In particular, we discuss the design, fabrication and functionalization of 2D biomaterials used for diverse biomedical applications based on the up-to-date progress. Furthermore, the interactions between 2D biomaterials and biological systems on the spatial-temporal scale are highlighted, which will deepen the understanding of the underlying action mechanism of 2D biomaterials aiding their design with improved functionalities. Finally, taking the bench-to-bedside as a focus, we conclude this review by proposing the current crucial issues/challenges and presenting the future development directions to advance the clinical translation of these emerging 2D biomaterials.

Fabrication and photocatalytic activity of graphitic-C3N4 quantum dots-decorated basic zinc carbonate prepared by a co-precipitation method

Graphitic carbon nitride quantum dots (CNQDs) with a high quantum yield (up to 43%) were synthesized by incorporating the unique organic functional group of barbituric acid into the framework of the carbon nitride structure by supramolecular pre-organization. The CNQDs were introduced onto the surface of basic zinc carbonate (BZC) by co-precipitation. The resulting CNQDs/BZC composite showed that the degradation efficiency of tetracycline was 2.4 times higher than that of ZnO. The Z-scheme mechanism for the as-prepared sample was proposed for the enhanced photocatalytic degradation rate. The ˙O₂^- and ˙OH radicals played major roles due to the suitable bandgap. Finally, the formation and possible photocatalytic mechanisms of the CNQDs/BZC composite are proposed.

Acute administration of sulfur-doped g-C3N4 induces cognitive deficits and exacerbates the levels of glial activation in mouse hippocampus

During the last decades, graphitic carbon nitride (g-C3N4) has attracted increasing attention in several biomedical fields. In this study, the effects of sulfur-doped g-C3N4 (TCN) on cognitive function and histopathology of hippocampus were investigated in mice. The characteristics of synthetized sample were evaluated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and energy dispersive X-ray (EDX). Twenty-four male NMRI mice received vehicle, TCN at doses of 50, 150, or 500 mg/kg via gavage for one week. Morris water maze test was done to assess the cognitive function at day 14 post TCN administration. Nissl staining was used to determine the number of dark cells in the hippocampus. Immunostaining against NeuN, GFAP, and Iba1 was done to evaluate the neuronal density and levels of glial activation, respectively. Behavioral tests indicated that TCN reduces the spatial learning and memory in a dose-dependent manner. Histological evaluations showed an increased level of neuronal loss and glial activation in the hippocampus of TCN treated mice at doses of 150 and 500 mg/kg. Overall, our data indicate that TCN induces the cognitive impairment that is partly mediated via its exacerbating impacts on neuronal loss and glial activation.

Viability inhibition of A375 melanoma cellsin vitroby a high-frequency nanosecond-pulsed magnetic field combined with targeted iron oxide nanoparticles via membrane magnetoporation

Poor efficacy and low electrical safety are issues in the treatment of tumours with pulsed magnetic fields (PMFs). Based on the cumulative effect of high-frequency pulses and the enhanced perforation effect of targeted nanoparticles, this article proposes for the first time a new method that combines high-frequency nanosecond-pulsed magnetic fields (nsPMFs) with folic acid-superparamagnetic iron oxide nanoparticles (SPIONs-FA) to kill tumour cells. After determining the safe concentration of the targeted iron oxide nanoparticles, CCK-8 reagent was used to detect the changes in cell viability after utilising the combined method. After that, PI macromolecular dyes were used to stain the cells. Then, the state of the cell membrane was observed by scanning electron microscopy, and other methods were applied to study the cell membrane permeability changes after the combined treatment of the cells. It was finally confirmed that the high-frequency PMF can significantly reduce cell viability through the cumulative effect. In addition, the targeted iron oxide nanoparticles can reduce the magnetic field amplitude and the number of pulses required for the high-frequency PMF to kill tumour cellsin vitrothrough magnetoporation. The objective of this research is to improve the electrical safety of the PMF with the use of nsPMFs for the safe, efficient and low-intensity treatment of tumours.

Synergistic enhancement of immunological responses triggered by hyperthermia sensitive Pt NPs via NIR laser to inhibit cancer relapse and metastasis

The combination of tumor ablation and immunotherapy is a promising strategy against tumor relapse and metastasis. Photothermal therapy (PTT) triggers the release of tumor-specific antigens and damage associated molecular patterns (DAMPs) in-situ. However, the immunosuppressive tumor microenvironment restrains the activity of the effector immune cells. Therefore, systematic immunomodulation is critical to stimulate the tumor microenvironment and augment the anti-tumor therapeutic effect. To this end, polyethylene glycol (PEG)-stabilized platinum (Pt) nanoparticles (Pt NPs) conjugated with a PD-L1 inhibitor (BMS-1) through a thermo-sensitive linkage were constructed. Upon near-infrared (NIR) exposure, BMS-1 was released and maleimide (Mal) was exposed on the surface of Pt NPs, which captured the antigens released from the ablated tumor cells, resulting in the enhanced antigen internalization and presentation. In addition, the Pt NPs acted as immune adjuvants by stimulating dendritic cells (DCs) maturation. Furthermore, BMS-1 relieved T cell exhaustion and induced the infiltration of effector T cells into the tumor tissues. Thus, Pt NPs can ablate tumors through PTT, and augment the anti-tumor immune response through enhanced antigen presentation and T cells infiltration, thereby preventing tumor relapse and metastasis.

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Pt NPs ablated tumor cells through PTT and served as immune adjuvants.

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Released BMS-1 and deprotected maleimide by thermo-sensitive Diels-Alder reaction.

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Pt NPs captured the antigens with exposed maleimide and stimulated dendritic cells maturation.

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Controlled release of BMS-1 in response to PTT relieved T cell exhaustion.

Emerging hybrid biomaterials for oxidative stress induced photodynamic therapy

Cancer therapy has undergone tremendous advancements in the past few years. The drawbacks of most of these therapies have encouraged researchers to obtain further insight into the complex chemical, biochemical and biological processes ongoing in the evolving cancer cells. These studies have led to an advent of reactive oxygen species mediated therapies to target and disrupt the cancer pathology. Photodynamic therapy (PDT) has emerged as a potent candidate for oxidative stress mediated non-invasive technique for rapid diagnosis and treatment of cancer. Towards this, biomacromolecules derived hybrid nanomaterials have contributed largely in the development of various therapeutics and theranostics for efficacious cancer management that can assist PDT. This review summarizes various hybrid biomaterials and advanced techniques that have been explored widely in the past few years for PDT application. The article also mentions some of the important in-vitro and in-vivo developments and observations explored by employing these materials for PDT application. The article also describes the interactions of these materials at the biological interface and the probable mechanism that assist in generation of oxidative stress and subsequent cell death.

Interaction of Genetically Encoded Photosensitizers with Scintillating Nanoparticles for X-ray Activated Photodynamic Therapy

Photodynamic therapy (PDT) applications are limited by the low penetration of UV-visible light into biological tissues. Considering X-rays as an alternative to excite photosensitizers (PS) in a deeper tumor, an intermediate particle able to convert the X-ray energy into visible light (scintillating nanoparticle, ScNP) is necessary. Moreover, accumulation of PS in the target cells is also required. Genetically encoded proteins could be used as a photosensitizer, allowing the exclusive expression of PS inside the tumor cells. Here, the interaction of eGFP, KillerOrange, and KillerRed proteins with LaF₃:Tb³⁺ ScNP was investigated, for the first time, in terms of its physicochemical and energy transfer properties. The protein structure, stability, and function were evaluated upon adverse physiological conditions and X-ray irradiation. Optimal parameters for energy transfer from ScNP to the proteins were investigated, paving the way for the use of genetically encoded photosensitizers for applications in X-ray activated photodynamic therapy.

Recent Advances in Photodynamic Therapy for Deep-Seated Tumors with the Aid of Nanomedicine

Photodynamic therapy (PDT) works through photoactivation of a specific photosensitizer (PS) in a tumor in the presence of oxygen. PDT is widely applied in oncology to treat various cancers as it has a minimally invasive procedure and high selectivity, does not interfere with other treatments, and can be repeated as needed. A large amount of reactive oxygen species (ROS) and singlet oxygen is generated in a cancer cell during PDT, which destroys the tumor effectively. However, the efficacy of PDT in treating a deep-seated tumor is limited due to three main reasons: Limited light penetration depth, low oxygen concentration in the hypoxic core, and poor PS accumulation inside a tumor. Thus, PDT treatments are only approved for superficial and thin tumors. With the advancement of nanotechnology, PDT to treat deep-seated or thick tumors is becoming a reachable goal. In this review, we provide an update on the strategies for improving PDT with nanomedicine using different sophisticated-design nanoparticles, including two-photon excitation, X-ray activation, targeting tumor cells with surface modification, alteration of tumor cell metabolism pathways, release of therapeutic gases, improvement of tumor hypoxia, and stimulation of host immunity. We focus on the difficult-to-treat pancreatic cancer as a model to demonstrate the influence of advanced nanomedicine in PDT. A bright future of PDT application in the treatment of deep-seated tumors is expected.

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.

Stimuli-Responsive Nanomaterials for Smart Tumor-Specific Phototherapeutics

Phototherapy, a type of photoresponsive regulation of biological activities, together with additional stimuli-responsive features, offers significant potential for enhancing the precision and efficacy of cancer treatments. To achieve tumor-specific therapeutics, numerous studies have focused on the development of smart phototherapeutic nanomaterials (PNMs) that can respond to endogenous pathological characteristics (e. g., mild acidity, the overproduction of glutathione, the overproduction of hydrogen peroxide, the overexpression of specific surface receptors, etc.) present in the tumor and/or exogenous stimuli. Such responsiveness can effectively improve the physicochemical properties, cellular uptake, tumor-targeting performance, and pharmacokinetic profile of PNMs. Herein, we will systematically discuss recent advances in this field. Moreover, potential challenges and future directions in the development of stimuli-responsive PNMs are also presented to support the development of this emerging cutting-edge research area.

Graphitic Carbon Nitride Quantum Dots Embedded in Carbon Nanosheets for Near-Infrared Imaging-Guided Combined Photo-Chemotherapy

Rational design of metal-free multifunctional therapeutic reagents offers great opportunities for cancer treatment in the clinic. Here, graphitic carbon nitride (g-C₃N₄) quantum dots embedded in carbon nanosheets (CNQD-CN) are in situ prepared via a one-pot hydrothermal approach with formamide as carbon and nitrogen source. The CNQD-CN not only serves as an excellent near-infrared (NIR) fluorescent marker but also acts as a pH-responsive nanocarrier. Moreover, the CNQD-CN possesses both light-to-heat conversion and singlet oxygen generation capabilities under a single NIR excitation wavelength. Further investigations show that systemic delivery of doxorubicin (DOX) using the multifunctional CNQD-CN nanocarrier under NIR irradiation was highly effective to cause cancer cell apoptosis in vitro and inhibit tumor growth in vivo. CNQD-CN represents a multifunctional therapeutic platform for synchronous cancer imaging and treatment through the synergistic effect of phototherapy and chemotherapy.

Recent Advances in Nanostrategies Capable of Overcoming Biological Barriers for Tumor Management

Engineered nanomaterials have been extensively employed as therapeutics for tumor management. Meanwhile, the complex tumor niche along with multiple barriers at the cellular level collectively hinders the action of nanomedicines. Here, the advanced strategies that hold promise for overcoming the numerous biological barriers facing nanomedicines are summarized. Starting from tumor entry, methods that promote tissue penetration of nanomedicine and address the hypoxia issue are also highlighted. Then, emphasis is given to the significance of overcoming both physical barriers, such as membrane-associated efflux pumps, and biological features, such as resistance to apoptosis. The pros and cons for an individual approach are presented. In addition, the associated technical problems are discussed, along with the importance of balancing the therapeutic merits and the additional cost of sophisticated nanomedicine designs.

Highly Efficient Metal-Free Two-Dimensional Luminescent Melem Nanosheets for Bioimaging

Two-dimensional (2D) luminescent materials have received tremendous attention for their intrinsic properties and promising practical applications. Achieving 2D luminescent materials with high photoluminescence (PL) efficiency is still a great challenge. Here, ultrathin metal-free 2D luminescent nanosheets of 2,5,8-triamino-tri-s-triazine (melem) are synthesized through a facile liquid exfoliation process assisted by ultrasound. The as-obtained melem nanosheets distribute in the size range from a few nanometers to around 150 nm with a thickness of about 5 to 6 atomic layers. Melem nanosheets exhibit efficient blue emission with a PL efficiency as high as 77.09%, much higher than the heavily explored 2D luminescent g-C₃N₄ nanosheets. The high efficiency of melem nanosheets comes from the absence of atom vacancies and the low carrier mobility. Benefiting from the easy synthesis, good stability, low cell toxicity, and high efficiency, melem nanosheets are successfully applied as bioimaging materials on human breast cancer cells, requiring no extra treatments such as surface coating or functionalization. These metal-free 2D luminescent melem nanosheets hold great potential for various applications including bioimaging and other biorelated applications.

Phototherapy with layered materials derived quantum dots

Quantum dots (QDs) originating from two-dimensional (2D) sheets of graphitic carbon nitride (g-C₃N₄), graphene, hexagonal boron nitride (h-BN), monoatomic buckled crystals (phosphorene), germanene, silicene and transition metal dichalcogenides (TMDCs) are emerging zero-dimensional materials. These QDs possess diverse optical properties, are chemically stable, have surprisingly excellent biocompatibility and are relatively amenable to surface modifications. It is therefore not difficult to see that these QDs have potential in a variety of bioapplications, including biosensing, bioimaging and anticancer and antimicrobial therapy. In this review, we briefly summarize the recent progress of these exciting QD based nanoagents and strategies for phototherapy. In addition, we will discuss about the current limitations, challenges and future prospects of QDs in biomedical applications.

Photosensitizers for Photodynamic Therapy

As an emerging clinical modality for cancer treatment, photodynamic therapy (PDT) takes advantage of the cytotoxic activity of reactive oxygen species (ROS) that are generated by light irradiating photosensitizers (PSs) in the presence of oxygen (O₂ ). However, further advancements including tumor selectivity and ROS generation efficiency are still required. Substantial efforts are devoted to design and synthesize smart PSs with optimized properties for achieving a desirable therapeutic efficacy. This review summarizes the recent progress in developing intelligent PSs for efficient PDT, ranging from single molecules to delicate nanomaterials. The strategies to improve ROS generation through optimizing photoinduced electron transfer and energy transfer processes of PSs are highlighted. Moreover, the approaches that combine PDT with other therapeutics (e.g., chemotherapy, photothermal therapy, and radiotherapy) and the targeted delivery in cancer cells or tumor tissue are introduced. The main challenges for the clinical application of PSs are also discussed.

Exploration of TiO2 nanoparticle mediated microdynamic therapy on cancer treatment

Radical therapy takes advantage of the reactive oxygen species produced in greater quantities within tumor cells than in normal cells. Here, for the first time, we explore a TiO₂ nanoparticle mediated microwave induced radical therapy (termed as Microdynamic Therapy) as a new cancer treatment method. The experiments in vitro and in vivo demonstrate that colloidal TiO₂ nanoparticles could significantly suppress the growth of osteosarcomas, even under low power (5 W) microwave (MW) irradiation for 5 min. The high photocatalytic activity of TiO₂ nanoparticles efficiently utilizes the microwave-induced plasmonic effect for the formation of reactive oxygen species (ROS). Furthermore, TiO₂ nanoparticles exhibit a higher cytotoxicity on cancer cells (osteosarcoma UMR-106 cells) than on normal cells (mouse fibroblast L929 cells). The effectiveness of TiO₂ nanoparticles for microwave induced radical therapy demonstrates that this is a new landmark approach to treating cancers.

A facile method for the synthesis of copper–cysteamine nanoparticles and study of ROS production for cancer treatment

A facile synthesis method of copper–cysteamine nanoparticles is reported and their application for cancer treatment through ROS-mediated mechanisms is explored.

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.

Multifunctional nanocarriers based on graphitic-C3N4 quantum dots for tumor-targeted, traceable and pH-responsive drug delivery

A multifunctional nanocarrier is developed for simultaneous targeted delivery, efficient tracking and cancer treatment at the cellular level.