Recent breakthroughs in graphene quantum dot-enhanced sonodynamic and photodynamic therapy

Water-soluble graphene quantum dots (GQDs) have recently exhibited considerable potential for diverse biomedical applications owing to their exceptional optical and chemical properties. However, the pronounced heterogeneity in the composition, size, and morphology of GQDs poses challenges for a comprehensive understanding of the intricate correlation between their structural attributes and functional properties. This variability also introduces complexities in scaling the production processes and addressing safety considerations. Light and sound have firmly established their role in clinical applications as pivotal energy sources for minimally invasive therapeutic interventions. Given the limited penetration depth of light, photodynamic therapy (PDT) predominantly targets superficial conditions such as dermatological disorders, head and neck malignancies, ocular ailments, and early-stage esophageal cancer. Conversely, ultrasound-based sonodynamic therapy (SDT) capitalizes on its superior ability to propagate and focus ultrasound within biological tissues, enabling a diverse range of therapeutic applications, including the management of gliomas, breast cancer, hematological tumors, and modulation of the blood-brain barrier (BBB). Considering the advancements in theranostic and precision therapies, reevaluating these conventional energy sources and their associated sensitizers is imperative. This review introduces three prevalent treatment modalities that harness light and sound stimuli: PDT, SDT, and a synergistic approach that integrates PDT and SDT. This study delineated the therapeutic dynamics and contemporary designs of sensitizers tailored to these modalities. By exploring the historical context of the field and elucidating the latest design strategies, this review underscores the pivotal role of GQDs in propelling the evolution of PDT and SDT. This aspires to stimulate researchers to develop "multimodal" therapies integrating both light and sound stimuli.

Quantum Dots as a Potential Multifunctional Material for the Enhancement of Clinical Diagnosis Strategies and Cancer Treatments

Quantum dots (QDs) represent a class of nanoscale wide bandgap semiconductors, and are primarily composed of metals, lipids, or polymers. Their unique electronic and optical properties, which stem from their wide bandgap characteristics, offer significant advantages for early cancer detection and treatment. Metal QDs have already demonstrated therapeutic potential in early tumor imaging and therapy. However, biological toxicity has led to the development of various non-functionalized QDs, such as carbon QDs (CQDs), graphene QDs (GQDs), black phosphorus QDs (BPQDs) and perovskite quantum dots (PQDs). To meet the diverse needs of clinical cancer treatment, functionalized QDs with an array of modifications (lipid, protein, organic, and inorganic) have been further developed. These advancements combine the unique material properties of QDs with the targeted capabilities of biological therapy to effectively kill tumors through photodynamic therapy, chemotherapy, immunotherapy, and other means. In addition to tumor-specific therapy, the fluorescence quantum yield of QDs has gradually increased with technological progress, enabling their significant application in both in vivo and in vitro imaging. This review delves into the role of QDs in the development and improvement of clinical cancer treatments, emphasizing their wide bandgap semiconductor properties.

Lights and Dots toward Therapy-Carbon-Based Quantum Dots as New Agents for Photodynamic Therapy

The large number of deaths induced by carcinoma and infections indicates that the need for new, better, targeted therapy is higher than ever. Apart from classical treatments and medication, photodynamic therapy (PDT) is one of the possible approaches to cure these clinical conditions. This strategy offers several advantages, such as lower toxicity, selective treatment, faster recovery time, avoidance of systemic toxic effects, and others. Unfortunately, there is a small number of agents that are approved for usage in clinical PDT. Novel, efficient, biocompatible PDT agents are, thus, highly desired. One of the most promising candidates is represented by the broad family of carbon-based quantum dots, such as graphene quantum dots (GQDs), carbon quantum dots (CQDs), carbon nanodots (CNDs), and carbonized polymer dots (CPDs). In this review paper, these new smart nanomaterials are discussed as potential PDT agents, detailing their toxicity in the dark, and when they are exposed to light, as well as their effects on carcinoma and bacterial cells. The photoinduced effects of carbon-based quantum dots on bacteria and viruses are particularly interesting, since dots usually generate several highly toxic reactive oxygen species under blue light. These species are acting as bombs on pathogen cells, causing various devastating and toxic effects on those targets.

Hydrogels for Antitumor and Antibacterial Therapy

As a highly absorbent and hydrophobic material with a three-dimensional network structure, hydrogels are widely used in biomedical fields for their excellent biocompatibility, low immunogenicity, adjustable physicochemical properties, ability to encapsulate a variety of drugs, controllability, and degradability. Hydrogels can be used not only for wound dressings and tissue repair, but also as drug carriers for the treatment of tumors. As multifunctional hydrogels are the focus for many researchers, this review focuses on hydrogels for antitumor therapy, hydrogels for antibacterial therapy, and hydrogels for co-use in tumor therapy and bacterial infection. We highlighted the advantages and representative applications of hydrogels in these fields and also outlined the shortages and future orientations of this useful tool, which might give inspirations for future studies.

Hyaluronic Acid-Conjugated Carbon Nanomaterials for Enhanced Tumour Targeting Ability

Hyaluronic acid (HA) has been implemented for chemo and photothermal therapy to target tumour cells overexpressing the CD44+ receptor. HA-targeting hybrid systems allows carbon nanomaterial (CNM) carriers to efficiently deliver anticancer drugs, such as doxorubicin and gemcitabine, to the tumour sites. Carbon nanotubes (CNTs), graphene, graphene oxide (GO), and graphene quantum dots (GQDs) are grouped for a detailed review of the novel nanocomposites for cancer therapy. Some CNMs proved to be more successful than others in terms of stability and effectiveness at removing relative tumour volume. While the literature has been focused primarily on the CNTs and GO, other CNMs such as carbon nano-onions (CNOs) proved quite promising for targeted drug delivery using HA. Near-infrared laser photoablation is also reviewed as a primary method of cancer therapy-it can be used alone or in conjunction with chemotherapy to achieve promising chemo-photothermal therapy protocols. This review aims to give a background into HA and why it is a successful cancer-targeting component of current CNM-based drug delivery systems.

Biocompatible Mesoporous Silica-Polydopamine Nanocomplexes as MR/Fluorescence Imaging Agent for Light-Activated Photothermal-Photodynamic Cancer Therapy In Vivo

Conventional cancer phototherapy with single modality suffers from low therapeutic efficacy and undesired posttreatment damage for adjacent normal tissues. Therefore, the lower NIR laser irradiation power is vital to the reduction or preclusion of risk of scalds and burns in normal tissues. Herein, we rationally proposed a novel multifunctional nanocomplex, which enabled good magnetic resonance (MR) imaging contrast effect and promising photothermal conversion efficacy. The prepared core/shell nanocomplexes [MSN-Ce6@PDA (Mn)] were composed of chlorin e6-embedded mesoporous silica/nanoparticle composites as the cores, and then polydopamine and manganese ions were conjugated on the cores to form protective shells. The MSN-Ce6@PDA (Mn) nanocomplexes revealed superior properties in colloidal stability, photothermal conversion, reaction oxygen species generation, magnetic resonance imaging, etc. Under the guidance of MR and fluorescence imaging, these MSN-Ce6@PDA (Mn) nanocomplexes were found to be primarily accumulated in the MDA-MB-231 tumor area. Furthermore, the combined photodynamic and photothermal therapy exhibited strong inhibition to the growth of MDA-MB-231 tumor in vitro and in vivo. Besides, the MSN-Ce6@PDA (Mn) nanocomplexes also exhibited excellent biocompatibility and low damage to the healthy animals. Hence, the results demonstrated that the prepared MSN-Ce6@PDA (Mn) nanocomplex would be a promising potential for multimodal imaging-guided phototherapy.

Synthesis of Graphene Quantum Dots Decorated With Se, Eu and Ag As Photosensitizer and Study of Their Potential to Use in Photodynamic Therapy

GQDs decorated with europium (Eu), silver (Ag) and selenium (Se) at molar ratios of 0.1%, 0.3% and 0.5% were produced for the first time at different temperatures of 180 °C, 200 °C and 220 °C. Surface passivation was carried out with polyethylene glycol (PEG) to increase the intensity of photoluminescence (PL) of the produced samples. The prepared quantum dots were characterized by X-Ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), transmission electron microscopy (TEM), PL and ultraviolet-visible spectroscopy. GQDs synthesized at 180 °C and decorated with Se (0.3%) had maximum PL intensity along with long lasted afterglow over 90 min compared with other samples. Excitation wavelength at 360 nm produced maximum emission at 600-900 nm and resulted in high singlet oxygen (¹O ₂) generation which makes it a good candidate for photodynamic therapy applications.

Graphene quantum dots in photodynamic therapy

Graphene quantum dots (GQDs) have shown great promise in a variety of medical applications. Recently, it has been found that GQDs are also beneficial for photodynamic therapy (PDT). However, the findings of GQDs as PDT agents have been controversial in the literature. Herein, we investigate the photoactivity of single-atomic-layered GQDs by examining their ability to generate singlet oxygen (¹O₂) under irradiation and their effects on the photoactivity of photosensitizers. We demonstrate that the GQDs with lateral sizes of ∼5 or 20 nm are photo-inactive for they cannot generate ¹O₂ under irradiation of either a 660 nm laser (105 mW cm^-2) or a halogen light. Moreover, the GQDs inhibit the photoactivity of two classical photosensitizers, namely, methylene blue and methylene violet. The stronger interaction between the GQDs and the photosensitizer results in greater inhibition of GQDs. Besides, the large-sized GQDs exhibit stronger inhibition than the small-sized GQDs. The inhibitory effect of the GQDs on the photoactivity of photosensitizers is consistent with their photo-cytotoxicity. These results indicate that the single-atomic-layered GQDs are not potential PDT agents, but they may be helpful for photosensitizers by delivering them into the cells. The discrepancy between the current work and the literature is probably associated with the GQDs used.

Synthesis, Properties, and Biological Applications of Metallic Alloy Nanoparticles

Metallic alloy nanoparticles are synthesized by combining two or more different metals. Bimetallic or trimetallic nanoparticles are considered more effective than monometallic nanoparticles because of their synergistic characteristics. In this review, we outline the structure, synthesis method, properties, and biological applications of metallic alloy nanoparticles based on their plasmonic, catalytic, and magnetic characteristics.

Graphene Quantum Dots for Optical Bioimaging

Graphene quantum dots (GQDs) have shown great potential in bioimaging applications due to their excellent biocompatibility, low cytotoxicity, feasibility for surface functionalization, physiological stability, and tunable fluorescence properties. This Review first introduces the intriguing optical properties of GQDs that are suitable for biological imaging, and is followed by the GQDs' synthetic strategies. The emergent and latest development methods for tuning GQDs' optical properties are further described in detail. The recent advanced applications of GQDs in vitro, particularly in cell imaging, targeted imaging, and theranostic nanoplatform fabrication, are included. The applications of GQDs for in vivo bioimaging are also covered. Finally, the Review is concluded with the challenges and prospectives that face this nascent yet exciting field.

Carbon-Based Nanomaterials for Biomedical Applications: A Recent Study

The study of carbon-based nanomaterials (CBNs) for biomedical applications has attracted great attention due to their unique chemical and physical properties including thermal, mechanical, electrical, optical and structural diversity. With the help of these intrinsic properties, CBNs, including carbon nanotubes (CNT), graphene oxide (GO), and graphene quantum dots (GQDs), have been extensively investigated in biomedical applications. This review summarizes the most recent studies in developing of CBNs for various biomedical applications including bio-sensing, drug delivery and cancer therapy.

Highly Biocompatible Chlorin e6-Loaded Chitosan Nanoparticles for Improved Photodynamic Cancer Therapy

The photosensitizer Chlorin e6 (Ce6) has been frequently employed for photodynamic therapy (PDT) of cancer; however, its nonspecific toxicity has limited its clinical applications. In this study, we prepared chitosan nanoparticles (CNPs), with a mean diameter of approximately 130 nm, by a nonsolvent-aided counterion complexation method in an aqueous solution, into which Ce6 could be physically entrapped during the preparation process. These CNPs and Ce6-loaded CNPs (CNPs-Ce6) were fully characterized by UV-vis, photoluminescence, and Fourier transform infrared spectroscopic analysis, as well as dynamic light scattering and transmission electron microscopy measurements. More importantly, the biocompatibility of the otherwise toxic Ce6 was significantly improved upon its loading into the CNPs, as demonstrated by both confocal laser scanning microscopy analysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Furthermore, the PDT efficiency of Ce6-loaded CNPs was dramatically enhanced, in comparison with that of the free Ce6, as shown by both MTT and flow cytometry assays. This discovery provides a novel strategy for improving the biocompatibility and therapeutic efficacy of PDT agents by using a natural, biocompatible polysaccharide carrier.

Tumor Cell-Specific Nuclear Targeting of Functionalized Graphene Quantum Dots In Vivo

Specific targeting of tumor tissues is essential for tumor imaging and therapeutics but remains challenging. Here, we report an unprecedented method using synthetic sulfonic-graphene quantum dots (sulfonic-GQDs) to exactly target the cancer cell nuclei in vivo without any bio- ligand modification, with no intervention in cells of normal tissues. The key factor for such selectivity is the high interstitial fluid pressure (IFP) in tumor tissues, which allows the penetration of sulfonic-GQDs into the plasma membrane of tumor cells. In vitro, the sulfonic-GQDs are repelled out of the cell membrane because of the repulsive force between negatively charged sulfonic-GQDs and the cell membranes which contributes to the low distribution in normal tissues in vivo. However, the plasma membrane-crossing process can be activated by incubating cells in ultrathin film culture medium because of the attachment of sulfonic-GQDs on cell memebranes. Molecular dynamics simulations demonstrated that, once transported across the plasma membrane, the negatively charged functional groups of these GQDs will leave the membrane with a self-cleaning function retaining a small enough size to achieve penetration through the nuclear membrane into the nucleus. Our study showed that IFP is a previously unrecognized mechanism for specific targeting of tumor cell nuclei and suggested that sulfonic-GQDs may be developed into novel tools for tumor-specific imaging and therapeutics.

Facile synthesis of a highly water-soluble graphene conjugated chlorophyll-a photosensitizer composite for improved photodynamic therapy in vitro

Graphene conjugated withp-bromo-phenylhydrazone-methyl pyropheophorbide-a (BPMppa, 683 nm), which is derived from a chlorophyll-aphotosensitizer, shows significantly improved water-solubility and PDT efficiency.