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The blood-brain barrier (BBB) plays an irreplaceable role in protecting the central nervous system (CNS) from bloodborne pathogens. However, the BBB complicates the treatment of CNS diseases because it prevents almost all therapeutic drugs from getting into the CNS. With the growing understanding of the physiological characteristics of the BBB and the development of nanotechnology, nanomaterial-based drug delivery systems have become promising tools for delivering drugs across the BBB to the CNS. Herein, we systematically summarize the recent progress in organic-nanoparticle delivery systems for treating CNS diseases and evaluate their mechanisms in overcoming the BBB with the aim to provide a comprehensive understanding of the advantages, disadvantages, and challenges of organic nanoparticles in delivering drugs across the BBB. This review may inspire new research ideas and directions for applying nanotechnology to treat CNS diseases.

Correction for ‘Copper coordination-based conjugated polymer nanoparticles for synergistic photodynamic and chemodynamic therapy’ by Qiang Cheng et al., Chem. Commun., 2023, https://doi.org/10.1039/d3cc01107k.

Nanocarrier-based drug delivery systems hold impressive promise for biomedical application because of their excellent water dispersibility, prolonged blood circulation time, increased drug accumulation in tumors, and potential in combination therapeutics. However, most nanocarriers suffer from low drug-loading efficiency, poor therapeutic effectiveness, potential systematic toxicity, and unstable metabolism. As an alternative, carrier-free nanodrugs, completely formulated with one or more drugs, have attracted increasing attention in cancer therapy due to their advantage of improved pharmacodynamics/pharmacokinetics, reduced toxicity, and high drug-loading. In recent years, carrier-free nanodrugs have contributed to progress in a variety of therapeutic modalities. In this review, different common strategies for carrier-free nanodrugs preparation are first summarized, mainly including nanoprecipitation, template-assisted nanoprecipitation, thin-film hydration, spray-drying technique, supercritical fluid (SCF) technique, and wet media milling. Then we describe the recently reported carrier-free nanodrugs for cancer chemo-monotherapy or combination therapy. The advantages of anti-cancer drugs combined with other chemotherapeutic, photosensitizers, photothermal, immunotherapeutic or gene drugs have been demonstrated. Finally, a future perspective is introduced to highlight the existing challenges and possible solutions toward clinical application of currently developed carrier-free nanodrugs, which may be instructive to the design of effective carrier-free regimens in the future.

The number of cases of bacterial resistance to antibiotics has been exponentially rising over the last decade. This issue is getting worse as the research and development of new antibiotics is much slower than the speed of pathogenic bacteria acquiring resistance to antibiotic treatment. To fight against antibacterial resistance, new therapeutic strategies have to be sought as alternatives to currently administered antibiotics. Many new materials, for instance, metal organic frameworks possess desirable properties such as improved bacterial internalization, flexible structural control, high selectivity, and controlled drug release and therefore, are potentially good candidates for antibacterial therapy to overcome antibiotic resistance. This review describes the most recent development of the field of the antibacterial applications of metal organic frameworks, and their hybrids and derivatives, followed by an in-depth analysis of their advantages, disadvantages and design factors of these materials. Finally, we present our insights into the important aspects of the future development of metal organic frameworks for antibacterial applications.

Photosensitizers (PSs) with aggregation-induced emission (AIE) feature show promising applications in fluorescence imaging-guided photodynamic therapy (PDT) in virtue of their enhanced fluorescence and phototoxicity in aggregate state. Seeking the ideal AIE luminogens (AIEgens) with good capability of generating reactive oxygen species is still urgent. Here we rationally synthesized an acceptor-donor-acceptor (A-D-A) structured AIEgen (BTZPP) and then prepared it into nanoparticles (NPs) through a simple re-precipitation procedure. The obtained BTZPP NPs show a deep-red emission peaked at 635 nm, a large Stokes shift of 195 nm, and a high 1O2 generation quantum yield of 72.3%. Moreover, these NPs can selectively target lysosomes in live cells and image mouse tumor with a high contrast and long-term tracking (up to 14 days) capability. The high-efficiency imaging-guided PDT against cancer cells and tumors is successfully demonstrated in vitro and in vivo.

Doping is an effective approach to regulate the physicochemical properties of carbon dots (CDs) and has received increasing attention in recent years. After CDs are doped with heteroatoms, their electronic structure, nanostructure, and chemical composition will be changed due to the overlapping atomic orbitals of the heteroatoms and carbon atoms, as well as the push/pull electron effect of heteroatoms. As compared with the non-metallic atoms, metal ions have more electron and unoccupied orbitals, and larger atomic radius, doping CDs with metal ions may induce noticeable alterations of the optical, electronic, and magnetic properties by changing the electron density distribution and energy gap of the CDs. In this review, we summarize the synthesis methods of metal ions-doped CDs (M−CDs), discuss the novel physicochemical properties originating from the doping of metal ions, and provide examples of applications in sensing, imaging, phototherapy, optoelectronics, and catalysis. Furthermore, we describe challenges in preparing M−CDs and provide an outlook for their future development.

C dots (CDs) have shown great potential in bioimaging and phototherapy. However, it is challenging to manipulate their fluorescent properties and therapeutic efficacy to satisfy the requirements for clinic applications. In this study, we prepared S, Se-codoped CDs via a hydrothermal method and demonstrated that the doping resulted in excitation wavelength-independent near-infrared (NIR) emissions of the CDs, with peaks at 731 and 820 nm. Significantly, the CDs exhibited a photothermal conversion efficiency of ~58.2%, which is the highest reported value for C nanostructures and is comparable to that of Au nanostructures. Moreover, the CDs had a large two-photon absorption cross section (~30,045 GM), which allowed NIR emissions and the photothermal conversion of the CDs through the two-photon excitation (TPE) mechanism. In vitro and in vivo tests suggested that CDs can function as new multifunctional phototheranostic agents for the TPE fluorescence imaging and photothermal therapy of cancer cells.

Carbon dots (CDs) are novel zero-dimensional carbonaceous nanomaterial, and they are featured with an attractive combination of physical, chemical, and biomedical properties including wide absorption spectrum, tunable fluorescence, excellent water solubility, outstanding photostability, and biocompatibility, which leads to their diverse applications as optically functional materials in various fields, e.g., fluorescence sensing, bioimaging, and drug delivery. Recently, it was revealed that CDs could be used as an effective photosensitizer to generate reactive oxygen species under light excitation, and/or a photothermal agent to convert light energy into heat, which enable them to be applied in photodynamic therapy or photothermal therapy for cancer treatment. In this review, we summarize the latest progress of research on CDs in phototherapy, including their use as nanocarriers for organic phototherapy agents, and highlight the strategies which are adopted to improve the therapeutic efficacy of CDs-based phototheranostics. Furthermore, we also discuss the challenges and prospects of the CDs-based phototheranostics towards clinical applications. We hope this review will provide critical insights to inspire new exciting discoveries on CDs from both fundamental and practical views so as to prompt their advances in the phototherapy.

In using nanomaterials for advanced photodynamic therapy, it is important to improve surface modification to increase stability, minimize non-specific loss of drugs in blood circulation, enhance the photostability of photosensitizers, and achieve highly efficient intracellular uptake. In this report, we for the first time covalently conjugate photosensitizer Chlorin e6 (Ce6) to polyethylene glycol modified layered double hydroxides and produce hybrid nanoflakes. These nanoflakes display many superior characteristics and lead to excellent in vivo photodynamic therapeutic efficiency and safety profiles.

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT) holds great potential for efficient cancer therapy by inducing reactive oxygen species (ROS) or heat into tumor. Nevertheless, PDT or PTT suffers from some limitations, e.g., PTT requires long-time and high-power laser irradiation to generate enough heat, while the hypoxia microenvironment of tumor and the limit diffuse distance of ROS hamper the efficacy of oxygen-dependent PDT. Here we reported the carbon dots (CDs) which could simultaneously generate singlet oxygen (1O2), hydroxyl radical (OH ), and heat under a 635 nm laser irradiation, with a 1O2 generation quantum yield of 5.7% and photothermal conversion efficiency of 73.5% (the highest thus far for CDs). Significantly, the CDs can selectively accumulate in lysosome, which is an ideal organelle for phototherapy because of its key role in sustaining cellular activity and stability. Moreover, the CDs present one-photon excited (OPE) and two-photon excited (TPE) fluorescence, and excellent photoacoustic (PA) imaging capability. Combining the good biocompatibility, the as-prepared CDs was served as multi-functional phototheranostic agent for synergistic PA/fluorescence imaging, and PDT/PTT.

This paper reports on new applications of water- dispersible graphene quantum dots (GQDs) that we recently developed. The prepared GQDs not only show broad absorption in the visible spectrum from 400 to 700 nm, but can also serve as smart photosensitizers with high singlet oxygen (1O2) production under visible-light irradiation (≥420 nm). We showed that the prepared G QDs can potentially be used as a metal-free, visible-light-active, sensitized photocatalyst via e nergy transfer mechanism, in which the light energy was converted by GQDs to produce 1O2, which can kill nearby microorganisms and degrade organic dyes.

Metal-free, organic-dye-based fluorescent nanorods were fabricated through a simple solvent-exchange procedure. The as-prepared nanorods exhibit low toxicity to living cells and excellent photostability. Furthermore, they are stable in solutions of various pHs and high ionic strength and in solutions with interfering metal ions. Compared with the free DPP-Br molecules in THF, these nanorods exhibit larger Stokes shift, broader absorption spectra, and greatly improved photostability. We successfully demonstrated the application of the nanorods, including their aforementioned beneficial characteristics, as a good fluorescence probe for bio-imaging.

Carbon nano-dots were synthesized by a hydrothermal method and integrated into the poly(vinyl alcohol) matrix as charge carrier trapping centers for nonvolatile memory devices. The devices with the configuration of ITO/carbon nano-dots-PVA/Ag exhibited bistable electrical switching at low voltage, long retention time and excellent reading stability.

A water-soluble, polythiophene-based colorimetric sensor was designed for selective and sensitive detection of carbenicillin in HEPES buffer solution. Quaternized quinine was linked to thiophene through bis-functionality benzyl group, which can interact with carbenicillin via electrostatic interaction and geometric match effect. The sensor exhibited a colorimetric signal change upon the addition of carbenicillin because of the formation of more nonplanar structures. However, the addition of other beta-lactam antibiotics or dicarboxylic acids into the sensor solution caused no obvious changes in absorbance intensity ratio. This result may be attributed to the cavity formed by the semi-rigid framework of PTQ2, which is suitable for the special binding with carbenicillin. This novel sensor can effectively distinguish carbenicillin from other beta-lactam antibiotics and has a wide linear range response in HEPES buffer solution. Linear calibration curves are obtained with 0 to 18 μmol/L of HEPES buffer solution, with a limit of detection of 0.54 μmol/L.

Clinical applications of current photodynamic therapy (PDT) agents are often limited by their low singlet oxygen (1O2) quantum yields, as well as by photobleaching and poor biocompatibility. Here we present a new PDT agent based on graphene quantum dots (GQDs) that can produce 1O2 via a multistate sensitization process, resulting in a quantum yield of ~1.3, the highest reported for PDT agents. The GQDs also exhibit a broad absorption band spanning the UV region and the entire visible region and a strong deep-red emission. Through in vitro and in vivo studies, we demonstrate that GQDs can be used as PDT agents, simultaneously allowing imaging and providing a highly efficient cancer therapy. The present work may lead to a new generation of carbon-based nanomaterial PDT agents with overall performance superior to conventional agents in terms of 1O2 quantum yield, water dispersibility, photo- and pH-stability, and biocompatibility., Photosensitisers are used in cancer therapy to promote the formation of reactive oxygen species on irradiation with light. Here, the authors present a graphene quantum dot photosensitiser with a singlet oxygen quantum yield of approximately 1.3, and investigate its in vitro and in vivo applications