One-Pot To Synthesize Multifunctional Carbon Dots for Near Infrared Fluorescence Imaging and Photothermal Cancer Therapy

Multifunctional hyaluronic acid-derived carbon dots for self-targeted imaging-guided photodynamic therapy

It is of vital importance to engineer the surface structures of carbon dots (CDs) to satisfy their practical biomedical applications, including imaging and treatment. In this work, one type of hyaluronic acid-derived CD (HA-CD) was synthesized via a facile one-step hydrothermal method using cancer cell-targeted HA as a precursor. The as-prepared HA-CDs were targeted actively toward CD44 receptor-overexpressing cancer cells because a partial HA structure remained on the HA-CD surface. Beyond this, HA-CDs can act as a novel photosensitizer, because they can generate O₂˙^- under 650 nm laser irradiation, and they also exhibit excellent blue photoluminescence emission. The in vitro results revealed that HA-CDs imaged selectively CD44-overexpressing cancer cells and inhibited their growth under 650 nm laser irradiation. Thus, HA-CDs can serve as a promising self-targeted imaging-guided photodynamic therapy (PDT) agent for cancer. The present research provides a promising new method to simply construct multifunctional CD-based targeted phototheranostic systems.

Multifunctional carbon dot for lifetime thermal sensing, nucleolus imaging and antialgal activity

Multifunctional carbon dots (CDs) with lifetime thermal sensing, nucleolus imaging, and antialgal activity properties were synthesized directly from ascorbic acid aqueous solution by a one-step electrochemical method at room temperature. The as-prepared CDs are responsive to temperature and exhibit an accurate linear response of fluorescence intensity vs. temperature (20-100 °C). These CDs can enter a cell and nucleolus, adsorb on the nucleic acids (DNA and RNA) and the fluorescence intensity of CDs is increased by the adsorption of nucleic acids. In addition, the CDs can inhibit the activity of RuBisCO in Anabaena sp., leading to reducing the growth of Anabaena sp. All these properties make the CDs serve as effective fluorescence-based nanothermometers, nucleolus probes, and antialgal agents.

Fluorometric determination of microRNA-155 in cancer cells based on carbon dots and MnO2 nanosheets as a donor-acceptor pair

A fluorometric method is presented for sensitive deternination of microRNA. It is making use of carbon dots (C-dots) loaded with a DNA probe as fluorophore and MnO₂ nanosheets as the quenching agent. The blue-green fluorescence of the DNA-loaded C-dots is quenched by the MnO₂ nanosheets, but restored on binding target microRNA-155. The maximum excitation wavelength and the maximum emission wavelength of C-dots are at 360 nm and 455 nm, respectively. Fluorescence correlates linearly with the log of the microRNA-155 concentration in two ranges, viz. from 0.15 to 1.65 aM and from 1.65 to 20 aM. The detection limit is as low as 0.1 aM. The assay can discriminate between fully complementary and single-base mismatch microRNA. The assay displayed high specificity when used to detect MCF-7 breast cancer cells which can be detected in concentrations from 1000 to 45,000 cells·mL^-1, with a 600 cells·mL^-1 detection limit. The method was applied to the analysis of serum samples spiked with microRNA, and satisfactory results were acquired. Graphical abstract Schematic of a fluorometric sensing platform for miRNA-155. The method relies on a FRET process between C-dots and MnO₂ nanosheets. This strategy has a practical application for detection of miRNA in cell lines and biological fluids.

Diketopyrrolopyrrole-based carbon dots for photodynamic therapy

The development of a simple and straightforward strategy to synthesize multifunctional carbon dots for photodynamic therapy (PDT) has been an emerging focus. In this work, diketopyrrolopyrrole-based fluorescent carbon dots (DPP CDs) were designed and synthesized through a facile one-pot hydrothermal method by using diketopyrrolopyrrole (DPP) and chitosan (CTS) as raw materials. DPP CDs not only maintained the ability of DPP to generate singlet oxygen (1O2) but also have excellent hydrophilic properties and outstanding biocompatibility. In vitro and in vivo experiments demonstrated that DPP CDs greatly inhibited the growth of tumor cells under laser irradiation (540 nm). This study highlights the potential of the rational design of CDs for efficient cancer therapy.

One-Step Hydrothermal Synthesis of Nitrogen-Doped Conjugated Carbonized Polymer Dots with 31% Efficient Red Emission for In Vivo Imaging

Carbon dots with long-wavelength emissions, high quantum yield (QY) and good biocompatibility are highly desirable for biomedical applications. Herein, a green, facile hydrothermal synthesis of highly efficient red emissive nitrogen-doped carbonized polymer dots (CPDs) with optimal emission at around 630 nm are reported. The red emissive CPDs possess a variety of superior properties including excellent water dispersibility, good biocompatibility, narrow bandwidth emission, an excitation-independent emission, and high QY (10.83% (in water) and 31.54% (in ethanol)). Further studies prove that such strong red fluorescence is ascribed to the efficient conjugated aromatic π systems and hydrogen bonds of CPDs. And the fluorescence properties of CPDs can be regulated by adjusting the dosage of HNO₃ before the reaction. Additionally, the as-prepared CPDs are successfully used as a fluorescent probe for bioimaging, both in vitro and in vivo. More importantly, biodistribution results demonstrate that most CPDs and their metabolites are not only excreted in urine but also excreted by hepatobiliary system in a rapid manner. Besides, the CPDs could easily cross the blood brain barrier, which may provide a valuable strategy for the theranostics of some brain diseases through real-time tracking.

A Magnetofluorescent Carbon Dot Assembly as an Acidic H2 O2 -Driven Oxygenerator to Regulate Tumor Hypoxia for Simultaneous Bimodal Imaging and Enhanced Photodynamic Therapy

Recent studies indicate that carbon dots (CDs) can efficiently generate singlet oxygen (¹ O₂ ) for photodynamic therapy (PDT) of cancer. However, the hypoxic tumor microenvironment and rapid consumption of oxygen in the PDT process will severely limit therapeutic effects of CDs due to the oxygen-dependent PDT. Thus, it is becoming particularly important to develop a novel CD as an in situ tumor oxygenerator for overcoming hypoxia and substantially enhancing the PDT efficacy. Herein, for the first time, magnetofluorescent Mn-CDs are successfully prepared using manganese(II) phthalocyanine as a precursor. After cooperative self-assembly with DSPE-PEG, the obtained Mn-CD assembly can be applied as a smart contrast agent for both near-infrared fluorescence (FL) (maximum peak at 745 nm) and T₁ -weighted magnetic resonance (MR) (relaxivity value of 6.97 mM^-1 s^-1 ) imaging. More interestingly, the Mn-CD assembly can not only effectively produce ¹ O₂ (quantum yield of 0.40) but also highly catalyze H₂ O₂ to generate oxygen. These collective properties of the Mn-CD assembly enable it to be utilized as an acidic H₂ O₂ -driven oxygenerator to increase the oxygen concentration in hypoxic solid tumors for simultaneous bimodal FL/MR imaging and enhanced PDT. This work explores a new biomedical use of CDs and provides a versatile carbon nanomaterial candidate for multifunctional nanotheranostic applications.

In vivo theranostics with near-infrared-emitting carbon dots-highly efficient photothermal therapy based on passive targeting after intravenous administration

Carbon dots that exhibit near-infrared fluorescence (NIR CDs) are considered emerging nanomaterials for advanced biomedical applications with low toxicity and superior photostability and targeting compared to currently used photoluminescence agents. Despite progress in the synthesis of NIR CDs, there remains a key obstacle to using them as an in vivo theranostic agent. This work demonstrates that the newly developed sulfur and nitrogen codoped NIR CDs are highly efficient in photothermal therapy (PTT) in mouse models (conversion efficiency of 59%) and can be readily visualized by photoluminescence and photoacoustic imaging. The real theranostic potential of NIR CDs is enhanced by their unique biodistribution and targeting. Contrary to all other nanomaterials that have been tested in biomedicine, they are excreted through the body's renal filtration system. Moreover, after intravenous injection, NIR CDs are accumulated in tumor tissue via passive targeting, without any active species such as antibodies. Due to their accumulation in tumor tissue without the need for intratumor injection, high photothermal conversion, excellent optical and photoacoustic imaging performance, and renal excretion, the developed CDs are suitable for transfer to clinical biomedical practice.

Self-assembly facilitated and visible light-driven generation of carbon dots

Molecular self-assembly may facilitate visible light generation of carbon dots.

Exploring the optimal ratio of d-glucose/l-aspartic acid for targeting carbon dots toward brain tumor cells

Targeting imaging to the desired site of action can increase the accuracy and effectiveness of diagnostic and treatment. In this work, a series of fluorescent carbon dots (CDs) were prepared by varying molar ratios of d-glucose (Glu) to l-aspartic acid (Asp). Their photophysical properties, morphologies and structures were investigated in detail. More important, the targeting ability was screened by confocal laser scanning microscopy and flow cytometry. The results indicate that CDs prepared from the optimal molar ratio of Glu/Asp (7:3) exhibit the highest targeting ability on C6 glioma cells. This work highlights the interplay of molecular design and corresponding functions, and open new possibility of developing state-of-art nanoparticles for biomedical applications.

High Quantum Yield Green-Emitting Carbon Dots for Fe(ІІІ) Detection, Biocompatible Fluorescent Ink and Cellular Imaging

In the present work, we reported the luminescence of a green-emitting carbon dots (CDs) synthesized via solid state reaction method using diammonium hydrogen citrate and urea as a starting materials. The obtained green-emitting CDs shows strong absorption in the 350-450 nm region and gives intense green emission (λmax = 537 nm) with quantum yield as high as 46.4% under 420 nm excitation. The obtained green-emitting CDs also demonstrates high photo-stability, which is evidenced by the fact that its emission intensity almost has no change under irradiation by a 365 nm UV lamp for 2 hours. Moreover, the obtained green-emitting CDs shows high sensitivity and selectivity for the detection of Fe3+, and their emission intensity response towards Fe3+ ions is highly linear (R2 = 0.995) over the concentration range from 25 to 300 µM, which could provide an effective platform for detection of Fe3+. Mostly important, we further demonstrate that such photoluminescent green-emitting CDs exhibits low toxicity and are biocompatible for use with in cellular imaging. Combining with low cytotoxicity, good water solubility and excellent luminescence properties, green-emitting CDs could be used as a biocompatible fluorescent ink in future applications.

Structure-Guided Design and Synthesis of a Mitochondria-Targeting Near-Infrared Fluorophore with Multimodal Therapeutic Activities

An urgent challenge for imaging-guided disease-targeted multimodal therapy is to develop the appropriate multifunctional agents to meet the requirements for potential applications. Here, a rigid cyclohexenyl substitution in the middle of a polymethine linker and two asymmetrical amphipathic N-alkyl side chains to indocyanine green (ICG) (the only FDA-approved NIR contrast agent) are introduced, and a new analog, IR-DBI, is developed with simultaneous cancer-cell mitochondrial targeting, NIR imaging, and chemo-/PDT/PTT/multimodal therapeutic activities. The asymmetrical and amphipathic structural modification renders IR-DBI a close binding to albumin protein site II to form a drug-protein complex and primarily facilitates its preferential accumulation at tumor sites via the enhanced permeability and retention (EPR) effect. The released IR-DBI dye is further actively taken up by cancer cells through organic-anion-transporting polypeptide transporters, and the lipophilic cationic property leads to its selective accumulation in the mitochondria of cancer cells. Finally, based on the high albumin-binding affinity, IR-DBI is modified into human serum albumin (HSA) via self-assembly to produce a nanosized complex, which exhibits significant improvement in the cancer targeting and multimodal cancer treatment with better biocompatibility. This finding may present a practicable strategy to develop small-molecule-based cancer theranostic agents for simultaneous cancer diagnostics and therapeutics.

Designed Synthesis of Au/Fe3 O4 @C Janus Nanoparticles for Dual-Modal Imaging and Actively Targeted Chemo-Photothermal Synergistic Therapy of Cancer Cells

Elaborately designed novel multifunctional Janus nanoparticles (JNPs) have attracted considerable attention owing to their anisotropic surface properties and various functionalities that allow them to house several components for the detection and targeting of cancer cells. In this work, we report a novel and facile approach to synthesize Au/Fe₃ O₄ @C JNPs, which were further selectively functionalized with amino-poly(ethylene glycol)thiol (NH₂ -PEG-SH) and folic acid (FA) on the exposed Au domains to achieve high contrast for X-ray computed tomography (CT) imaging, excellent stability, good biocompatibility, as well as cancer cell-specific targeting. Meanwhile, the other Fe₃ O₄ @C sides with mesoporous structure served as a drug delivery vehicle for doxorubicin (DOX), an efficient photothermal therapy (PTT) agent, and a magnetic resonance (MR) imaging contrast agent. Taking these features together, these unique multifunctional JNPs provide an intriguing nanoplatform for dual-modal CT and MR imaging-guided actively targeted chemo-photothermal synergistic cancer therapy.

Exceptionally High Payload of the IR780 Iodide on Folic Acid-Functionalized Graphene Quantum Dots for Targeted Photothermal Therapy

The IR780 iodide (IR780) is recognized as an effective theranostic agent for simultaneous near-infrared fluorescence imaging and photothermal therapy (PTT). However, the rigid chloro-cyclohexenyl ring makes IR780 insoluble in almost all pharmaceutically acceptable solvents, which inevitably limits its clinical application. We report folic acid (FA)-functionalized graphene quantum dots (GQDs-FA) containing a large and intact sp² domain with carboxyl groups around the edge. Such GQDs-FA possess exceptionally high loading capacity for IR780 via strong π-π stacking interactions, and the water solubility of IR780 is improved by over 2400-fold after loading onto GQDs-FA (IR780/GQDs-FA). IR780/GQDs-FA with an improved photostability, an enhanced tumor-targeting ability, and a high photothermal conversion efficiency of 87.9% were capable of producing sufficient hyperthermia to effectively kill cancer cells and completely eradicate tumors upon 808 nm laser irradiation. The present IR780/GQDs-FA may open up great opportunities for the effective PTT to treat cancer.

Dendrimer-Modified MoS2 Nanoflakes as a Platform for Combinational Gene Silencing and Photothermal Therapy of Tumors

Exploitation of novel hybrid nanomaterials for combinational tumor therapy is challenging. In this work, we synthesized dendrimer-modified MoS₂ nanoflakes for combinational gene silencing and photothermal therapy (PTT) of cancer cells. Hydrothermally synthesized MoS₂ nanoflakes were modified with generation 5 (G5) poly(amidoamine) dendrimers partially functionalized with lipoic acid via disulfide bond. The formed G5-MoS₂ nanoflakes display good colloidal stability and superior photothermal conversion efficiency and photothermal stability. With the dendrimer surface amines on their surface, the G5-MoS₂ nanoflakes are capable of delivering Bcl-2 (B-cell lymphoma-2) siRNA to cancer cells (4T1 cells, a mouse breast cancer cells) with excellent transfection efficiency, inducing 47.3% of Bcl-2 protein expression inhibition. In vitro cell viability assay data show that cells treated with the G5-MoS₂/Bcl-2 siRNA polyplexes under laser irradiation have a viability of 21.0%, which is much lower than other groups of single mode PTT treatment (45.8%) or single mode of gene therapy (68.7%). Moreover, the super efficacy of combinational therapy was further demonstrated by treating a xenografted 4T1 tumor model in vivo. These results suggest that the synthesized G5-MoS₂ nanoflakes may be employed as a potential nanoplatform for combinational gene silencing and PTT of tumors.

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.

pH-Responsive near-infrared fluorescent cyanine dyes for molecular imaging based on pH sensing

pH-Responsive near-infrared cyanine dyes were synthesized and applied as imaging probes of acidic intracellular compartments of living cells.

GSH-triggered size increase of porphyrin-containing nanosystems for enhanced retention and photodynamic activity

We demonstrate the rational design of a size changeable nanosystem triggered by intracellular GSH for enhanced retention and photodynamic activity.

Paclitaxel-Paclitaxel Prodrug Nanoassembly as a Versatile Nanoplatform for Combinational Cancer Therapy

Recently, nanomedicine without drug carriers has attracted many pharmacists' attention. A novel paclitaxel-s-s-paclitaxel (PTX-s-s-PTX) conjugate with high drug loading (∼78%, w/w) was synthesized by conjugating paclitaxel to paclitaxel by using disulfide linkage. The conjugate could self-assemble into uniform nanoparticles (NPs) with 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DiR) encapsulated within the core of PTX-s-s-PTX NPs for photothermal therapy (PTT). The DiR-loaded self-assembled nanoparticles (DSNs) had a mean diameter of about 150 nm and high stability in biological condition. A disulfide bond is utilized as a redox-responsive linkage to facilitate a rapid release of paclitaxel in tumor cells. DSNs indicated significant cytotoxicity as a result of the synergetic chemo-thermal therapy. DSNs were featured with excellent advantages, including high drug loading, redox-responsive releasing behavior of paclitaxel, capability of loading with photothermal agents, and combinational therapy with PTT. In such a potent nanosystem, prodrug and photothermal strategy are integrated into one system to facilitate the therapy efficiency.