Carbon Dots with Intrinsic Theranostic Properties for Bioimaging, Red-Light-Triggered Photodynamic/Photothermal Simultaneous Therapy In Vitro and In Vivo

Porphyra polysaccharide-derived carbon dots for non-viral co-delivery of different gene combinations and neuronal differentiation of ectodermal mesenchymal stem cells

In this study, multifunctional fluorescent carbon dots (CDs) were synthesized using a one-pot hydrothermal carbonization reaction, with the naturally-occurring porphyra polysaccharide (PPS) serving as a single carbon source for the first time and ethylenediamine (Ed) acting as the surface passivation agent. The resulting CDs enjoyed a high quantum yield (56.3%), excitation-dependent fluorescence, small size (<10 nm), spherical shape, uniform distribution, positive surface charge, low cytotoxicity and excellent ability to condense macromolecular plasmid DNA. The synthesized CDs were employed for neuronal induction from ectodermal mesenchymal stem cells for the first time via highly efficient non-viral gene delivery. The optimal combination of factors (Ascl1 and Brn2) was selected from seven different combinations out of Ascl1, Brn2 and Sox2 according to the expression of neuronal markers (Tuj1, Map2 and Tau). The results of qRT-PCR demonstrated that the CDs possessed a significantly higher transfection efficiency than the commercially available transfection reagents PEI (25 kDa) and Lipofectamine2000. Moreover, the CDs/pDNA nanoparticles exhibited more efficient neuronal differentiation of the EMSCs than the AT-RA-containing induction medium. Furthermore, the CDs/pDNA nanoparticles could enter cells via both caveolae- and clathrin-mediated endocytosis. Taken together, the natural polysaccharide PPS-derived CDs enriched the current application of CDs by employing the CDs as a novel non-viral gene carrier for neuronal differentiation of adult stem cells, which held great promise in tissue engineering and bioimaging.

Biocompatible Iron Phthalocyanine-Albumin Assemblies as Photoacoustic and Thermal Theranostics in Living Mice

Exploring novel and versatile nanomaterials for the construction of personalized multifunctional phototheranostics with significant potentials in bioimaging-guided tumor phototherapies has attracted considerable attention. Herein, the phototheranostic agent human serum albumin-iron (II) phthalocyanine FePc nanoparticles (HSA-FePc NPs) were fabricated for photoacoustic (PA) imaging-guided photothermal therapy (PTT) of cancer in vivo. The prepared HSA-FePc NPs exhibited high stability, efficient NIR absorption, good capability and stability of photothermal behavior with a high photothermal conversion efficiency of ∼44.4%, high contrast and spatial resolution of PA imaging, efficient cancer therapy, and low long-term toxicity. This potent multifunctional phototheranostic is, therefore, very promising and favorable for effective, precise, and safe antitumor treatment in clinical application.

Self-Assembled Carbon Dot Nanosphere: A Robust, Near-Infrared Light-Responsive, and Vein Injectable Photosensitizer

Self-assembly "activated" carbon dot photosensitizer: a robust, NIR-light responsive, and vein injectable carbon dot nanosphere (CDNS) photosensitizer with ¹ O₂ quantum yield of 0.45 under 671 nm laser irradiation has been developed through self-assembly using individual CD as building units. This study develops the biomedical applications of CD, highlights the self-assembly for designing well-defined CD-based photosensitizers, and promotes future explorations of this CDNS photosensitizer in nanomedical and clinical applications.

Versatile Polymer Nanoparticles as Two-Photon-Triggered Photosensitizers for Simultaneous Cellular, Deep-Tissue Imaging, and Photodynamic Therapy

Clinical applications of current photodynamic therapy (PDT) photosensitizers (PSs) are often limited by their absorption in the UV-vis range that possesses limited tissue penetration ability, leading to ineffective therapeutic response for deep-seated tumors. Alternatively, two-photon excited PS (TPE-PS) using NIR light triggered is one the most promising candidates for PDT improvement. Herein, multimodal polymer nanoparticles (PNPs) from polythiophene derivative as two-photon fluorescence imaging as well as two-photon-excited PDT agent are developed. The prepared PNPs exhibit excellent water dispersibility, high photostability and pH stability, strong fluorescence brightness, and low dark toxicity. More importantly, the PNPs also possess other outstanding features including: (1) the high ¹ O₂ quantum yield; (2) the strong two-photon-induced fluorescence and efficient ¹ O₂ generation; (3) the specific accumulation in lysosomes of HeLa cells; and (4) the imaging detection depth up to 2100 µm in the mock tissue under two-photon. The multifunctional PNPs are promising candidates as TPE-PDT agent for simultaneous cellular, deep-tissue imaging, and highly efficient in vivo PDT of cancer.

Polymer nanoparticles with high photothermal conversion efficiency as robust photoacoustic and thermal theranostics

Synthesis of photothermal agents with absorption in the near-infrared (NIR) region and featuring excellent photostability, high photothermal conversion efficiency, and good biocompatibility is necessary for the application of photothermal therapy (PTT). In this work, a low band gap thiophene-benzene-diketopyrrolopyrrole (TBD)-based polymer was synthesized and used to fabricate TBD polymer nanoparticles (TBDPNPs) through a one-step nanoprecipitation method. The obtained near-infrared-absorbing TBDPNPs presented good water dispersibility, high photothermal stability, and low toxicity. Significantly, the TBDPNPs exhibited an ultrahigh photothermal conversion efficiency of approximately 68.1% under 671 nm laser irradiation. In addition, photoacoustic (PA) imaging, with high spatial resolution and deep tissue penetration, showed that the TBDPNPs targeted tumor sites through the enhanced permeability and retention effect. Therefore, the robust TBDPNPs with a photothermal conversion efficiency of 68.1% can serve as an excellent therapeutic agent for PA-imaging-guided PTT.

Multifunctional Theranostics for Dual-Modal Photodynamic Synergistic Therapy via Stepwise Water Splitting

Combined therapy using multiple approaches has been demonstrated to be a promising route for cancer therapy. To achieve enhanced antiproliferation efficacy under hypoxic condition, here we report a novel hybrid system by integrating dual-model photodynamic therapies (dual-PDT) in one system. First, we attached core-shell structured up-conversion nanoparticles (UCNPs, NaGdF₄:Yb,Tm@NaGdF₄) on graphitic-phase carbon nitride (g-C₃N₄) nanosheets (one photosensitizer). Then, the as-fabricated nanocomposite and carbon dots (another photosensitizer) were assembled in ZIF-8 metal-organic frameworks through an in situ growth process, realizing the dual-photosensitizer hybrid system employed for PDT via stepwise water splitting. In this system, the UCNPs can convert deep-penetration and low-energy near-infrared light to higher-energy ultraviolet-visible emission, which matches well with the absorption range of the photosensitizers for reactive oxygen species (ROS) generation without sacrificing its efficacy under ZIF-8 shell protection. Furthermore, the UV light emitted from UCNPs allows successive activation of g-C₃N₄ and carbon dots, and the visible light from carbon dots upon UV light excitation once again activate g-C₃N₄ to produce ROS, which keeps the principle of energy conservation thus achieving maximized use of the light. This dual-PDT system exhibits excellent antitumor efficiency superior to any single modality, verified vividly by in vitro and in vivo assay.

Bacteria-derived fluorescent carbon dots for microbial live/dead differentiation

Microbial viability assessment plays a key role in many areas such as pathogen detection, infectious disease treatment and antimicrobial drug development. Many conventional viability dyes (such as propidium iodide, PI) used for differentiating live/dead microbes suffer from notable cytotoxicity, poor photostability and are of high cost. Thus their applications for accurate microbial viability determination are limited. Herein, for the first time we report the successful synthesis of fluorescent carbon dots (CDs) from bacteria via one-step hydrothermal carbonization. Benefiting from their highly negative surface charge (the zeta potential is as high as around -42 mV) and suitable size, the CDs can selectively stain dead microbial cells (bacteria and fungi) but not live ones. Importantly, compared to the widely used commercial dye PI, the developed CDs possess many great advantages including low cytotoxicity, multicolor imaging ability, excellent photostability and high selectivity. Moreover, because the synthetic method is simple, inexpensive and eco-friendly, this type of CD is suitable for large-scale production, making it an excellent candidate for microbial live/dead differentiation and viability assessment. The present work explores the feasibility of using bacteria to fabricate novel CDs and broadens the applications of CDs for biomedical applications.

Porphyrin-Based Carbon Dots for Photodynamic Therapy of Hepatoma

Porphyrin-containing carbon dots (CDs) possess ultrasmall size, excellent water solubility, and photostability. These CDs can effectively generate cytotoxic singlet oxygen upon irradiation, and induce the cell apoptosis. Photodynamic ability of CDs inhibits the growth of hepatoma. This work not only sheds light on developing functional carbon dots, but also highlights the importance of special-structure precursor molecules in synthesizing functional CDs.

One step, high yield synthesis of amphiphilic carbon quantum dots derived from chia seeds: a solvatochromic study

In this work, we demonstrate the high-yield synthesis of carbon quantum dots using a one-step eco-friendly, low-cost thermal treatment of a renewable biomass, i.e. natural chia seeds.

Targeted Nanomaterials for Phototherapy

Phototherapies involve the irradiation of target tissues with light. To further enhance selectivity and potency, numerous molecularly targeted photosensitizers and photoactive nanoparticles have been developed. Active targeting typically involves harnessing the affinity between a ligand and a cell surface receptor for improved accumulation in the targeted tissue. Targeting ligands including peptides, proteins, aptamers and small molecules have been explored for phototherapy. In this review, recent examples of targeted nanomaterials used in phototherapy are summarized.

Carbon-Based Materials for Photo-Triggered Theranostic Applications

Carbon-based nanomaterials serve as a type of smart material for photo-triggered disease theranostics. The inherent physicochemical properties of these nanomaterials facilitate their use for less invasive treatments. This review summarizes the properties and applications of materials including fullerene, nanotubes, nanohorns, nanodots and nanographenes for photodynamic nanomedicine in cancer and antimicrobial therapies. Carbon nanomaterials themselves do not usually act as photodynamic therapy (PDT) agents owing to the high hydrophobicity, however, when the surface is passivated or functionalized, these materials become great vehicles for PDT. Moreover, conjugation of carbonaceous nanomaterials with the photosensitizer (PS) and relevant targeting ligands enhances properties such as selectivity, stability, and high quantum yield, making them readily available for versatile biomedical applications.

A Versatile and Clearable Nanocarbon Theranostic Based on Carbon Dots and Gadolinium Metallofullerene Nanocrystals

Nanocarbons such as carbon nanotubes, graphene derivatives, and carbon nanohorns have illustrated their potential uses as cancer theranostics owing to their intrinsic fluorescence or NIR absorbance as well as superior cargo loading capacity. However, some problems still need to be addressed, such as the fates and long-term toxicology of different nanocarbons in vivo and the improvement of their performance in various biomedical imaging-guided cancer therapy systems. Herein, a versatile and clearable nanocarbon theranostic based on carbon dots (CDs) and gadolinium metallofullerene nanocrystals (GFNCs) is first developed, in which GFNCs enhance the tumor accumulation of CDs, and CDs enhance the relaxivity of GFNCs, leading to an efficient multimodal imaging-guided photodynamic therapy in vivo without obvious long-term toxicity. Furthermore, biochemical analysis reveals that the novel nanotheranostic can harmlessly eliminate from the body in a reasonable period of time after exerting diagnostic and therapeutic function.

Gold nanorod@silica-carbon dots as multifunctional phototheranostics for fluorescence and photoacoustic imaging-guided synergistic photodynamic/photothermal therapy

Phototheranostics, which is the application of light in the diagnostic imaging and therapy of cancer, has shown great promise for multimodal cancer imaging and effective therapy. Herein, we developed multifunctional gold nanorod@silica-carbon dots (GNR@SiO2-CDs) as a phototheranostic agent by incorporating carbon dots (CDs) with gold nanorods (GNRs), using SiO2 as a scaffold. In GNR@SiO2-CDs, the GNRs act as both photoacoustic (PA) imaging and photothermal therapy (PTT) agents, and the CDs serve as fluorescence (FL) imaging and photodynamic therapy (PDT) agents. The introduction of SiO2 not only improves the chemical stability of the GNRs and CDs in the physiological environment but also prevents the absolute quenching of the fluorescence of the CDs by GNRs. These collective properties make GNR@SiO2-CDs a novel phototheranostic agent, in which high sensitivity and good spatial resolution of FL/PA imaging can be achieved to guide PDT/PTT treatments through i.v. administration. The combination of PDT and PTT proved to be more efficient in killing cancer cells compared to PDT or PTT alone under a low dose of laser irradiation (≤0.5 W cm(-2)). Furthermore, GNR@SiO2-CDs could be cleared out from the body of mice, indicating the low toxicity of this phototheranostic agent. Our work highlights the potential of using GNRs and CDs as novel phototheranostic agents for multifunctional cancer therapies.

A macromolecular cyclometalated gold(iii) amphiphile displays long-lived emissive excited state in water: self-assembly and in vitro photo-toxicity

A cyclometalated gold(iii) amphiphile self-assembles into nano-sized micelles in water, displaying a long-lived emissive excited state andin vitrophoto-toxicity.