近红外发光Ag2S-CdS 核壳结构水溶性量子点的合成及光学性质

本文以谷胱甘肽(GSH)作为表面活性剂,采用两步法,先生成Ag2S核,再生长CdS,得到了高质量的Ag2S-CdS核壳结构水溶性量子点。我们用XRD,TEM,HRTEM和EDS研究了产物的结构,形貌和组分,用紫外可见吸收光谱和荧光发射光谱研究了所得量子点的光学性质,同时考察了反应时间,GSH的量,Ag和S源前驱物的含量对量子点光学性质的影响。实验结果表明量子点稳定性好,荧光寿命长,可在710~718 nm近红外区域发光。在核生长过程中,Ag和S源的含量同时影响量子点的发光位置和强度,而GSH量和壳层生长中S源的量几乎只影响近红外发光强度,发光位置保持不变。不同的量子点光学性质可能来源于量子点中组分及表面缺陷的分布。     

Computational design of chlorin based photosensitizers with enhanced absorption properties

The porphyrin and chlorin parent compounds constitute the base of many potent photosensitizers aimed to be utilized in photodynamic therapy (PDT). However, the photosensitizers available on the market today are not ideal for use in PDT; many of them suffering from drawbacks such as long-lasting photosensitization or absorption at wavelengths below the optimal tissue penetration. This has emphasized the need of new photosensitizers with improved photodynamic properties. In the present study we have used density functional theory based methods to design new chlorin compounds with conjugated substituents such as vinyl groups and carboxylic acids, aiming for strong absorption in the therapeutic window of PDT. The specific substituent positions were found to have a significant effect on the spectra. A chlorin with four propenoic acids was able to red-shift the absorption the most compared with non-substituted chlorin, generating the red-most absorption at 755 nm, and with significantly enhanced oscillator strengths. The results from the present study constitute a useful starting point for further design of tetrapyrrole derivatives as improved photosensitizers.     

Self-Amplified Photodynamic Therapy through the 1O2-Mediated Internalization of Photosensitizers from a Ppa-Bearing Block Copolymer

Nanocarriers are employed to deliver photosensitizers for photodynamic therapy (PDT) through the enhanced penetration and retention effect, but disadvantages including the premature leakage and non-selective release of photosensitizers still exist. Herein, we report a ¹O₂-responsive block copolymer (POEGMA-b-P(MAA-co-VSPpaMA) to enhance PDT via the controllable release of photosensitizers. Once nanoparticles formed by the block copolymer have accumulated in a tumor and have been taken up by cancer cells, pyropheophorbide a (Ppa) could be controllably released by singlet oxygen (¹O₂) generated by light irradiation, enhancing the photosensitization. This was demonstrated by confocal laser scanning microscopy and in vivo fluorescence imaging. The ¹O₂-responsiveness of POEGMA-b-P(MAA-co-VSPpaMA) block copolymer enabled the realization of self-amplified photodynamic therapy by the regulation of Ppa release using NIR illumination. This may provide a new insight into the design of precise PDT.     

Self‐Amplified Photodynamic Therapy through the 1O2‐Mediated Internalization of Photosensitizers from a Ppa‐Bearing Block Copolymer

Nanocarriers are employed to deliver photosensitizers for photodynamic therapy (PDT) through the enhanced penetration and retention effect, but disadvantages including the premature leakage and non‐selective release of photosensitizers still exist. Herein, we report a ¹O₂‐responsive block copolymer (POEGMA‐b‐P(MAA‐co‐VSPpaMA) to enhance PDT via the controllable release of photosensitizers. Once nanoparticles formed by the block copolymer have accumulated in a tumor and have been taken up by cancer cells, pyropheophorbide a (Ppa) could be controllably released by singlet oxygen (¹O₂) generated by light irradiation, enhancing the photosensitization. This was demonstrated by confocal laser scanning microscopy and in vivo fluorescence imaging. The ¹O₂‐responsiveness of POEGMA‐b‐P(MAA‐co‐VSPpaMA) block copolymer enabled the realization of self‐amplified photodynamic therapy by the regulation of Ppa release using NIR illumination. This may provide a new insight into the design of precise PDT.     

Photoluminescence properties of Ag2S semiconductor clusters synthesized in micropores and mesopores

Silver sulfide (Ag₂S) clusters were synthesized in microporous zeolites and mesoporous AlMCM-41 by the sulfurization of Ag⁺ ions exchanged within the pores of the host. Characterization was performed by means of XRD, UV-Vis Ag K-edge XAFS and photoluminescence. The pore size of the host has great effects on the photoluminescence properties. Ag₂S/AlMCM-41 showed photoluminescence at the longer wavelengths than Ag₂S/zeolites. The photoluminescence band of Ag₂S in the zeolite with 1-dimensional channels was narrow in comparison to the Ag₂S in zeolites with 2- or 3-dimensional channels.     

Quantum dot-based energy transfer: perspectives and potential for applications in photodynamic therapy

Quantum dots have emerged as an important class of material that offers great promise to a diverse range of applications ranging from energy conversion to biomedicine. Here, we review the potential of using quantum dots and quantum dot conjugates as sensitizers for photodynamic therapy (PDT). The photophysics of singlet oxygen generation in relation to quantum dot-based energy transfer is discussed and the possibility of using quantum dots as photosensitizer in PDT is assessed, including their current limitations to applications in biological systems. The biggest advantage of quantum dots over molecular photosensitizers that comes into perspective is their tunable optical properties and surface chemistries. Recent developments in the preparation and photophysical characterization of quantum dot energy transfer processes are also presented in this review, to provide insights on the future direction of quantum dot-based photosensitization studies from the viewpoint of our ongoing research.     

Photobleaching Kinetics and Effect of Solvent in the Photophysical Properties of Indocyanine Green for Photodynamic Therapy

Indocyanine green is an attractive molecule for photodynamic therapy due to its near infrared absorption, resulting in a higher tissue penetration. However, its quantum yields of the triplet and singlet state have been reported to be low and then, reactive oxygen species are unlikely to be formed. Aiming to understand the ICG role in photodynamic response, its photobleaching behavior in solution has been studied under distinct conditions of CW laser irradiation at 780 and 808 nm, oxygen saturations and solvents. Sensitizer bleaching and photoproduct formation were measured by absorption spectroscopy and analyzed using the PDT bleaching macroscopic model to extract physical parameters. ICG photobleaching occurs even at lower oxygen concentrations, indicating that the molecule presents more than one way of degradation. Photoproducts were produced even in solution of less than 4 % oxygen saturation for both solvents and excitation wavelengths. Also, the amplitude of absorption related to J-dimers was increased during irradiation, but only in 50 % PBS solution. The formation of photoproducts was enhanced in the presence of J-type dimers under low oxygen concentration, and the quantum yields of triplet and singlet states were one order of magnitude and two times higher, respectively, when compared to ICG in distilled H₂O.     

Highly Twisted Conformation Thiopyrylium Photosensitizers for In Vivo Near Infrared-II Imaging and Rapid Inactivation of Coronavirus

Despite significant effort, a majority of heavy-atom-free photosensitizers have short excitation wavelengths, thereby hampering their biomedical applications. Here, we present a facile approach for developing efficient near-infrared (NIR) heavy-atom-free photosensitizers. Based on a series of thiopyrylium-based NIR-II (1000–1700 nm) dyads, we found that the star dyad HD with a sterically bulky and electron-rich moiety exhibited configuration torsion and significantly enhanced intersystem crossing (ISC) compared to the parent dyad. The electron excitation characteristics of HD changed from local excitation (LE) to charge transfer (CT)-domain, contributing to a ≈6-fold reduction in energy gap (ΔE_ST), a ≈10-fold accelerated ISC process, and a ≈31.49-fold elevated reactive oxygen species (ROS) quantum yield. The optimized SP@HD-PEG_2K lung-targeting dots enabled real-time NIR-II lung imaging, which precisely guided rapid pulmonary coronavirus inactivation.     

Elucidation of the Intersystem Crossing Mechanism in a Helical BODIPY for Low-Dose Photodynamic Therapy

Intersystem crossing (ISC) of triplet photosensitizers is a vital process for fundamental photochemistry and photodynamic therapy (PDT). Herein, we report the co-existence of efficient ISC and long triplet excited lifetime in a heavy atom-free bodipy helicene molecule. Via theoretical computation and time-resolved EPR spectroscopy, we confirmed that the ISC of the bodipy results from its twisted molecular structure and reduced symmetry. The twisted bodipy shows intense long wavelength absorption (ϵ=1.76×10⁵ m ⁻¹ cm⁻¹ at 630 nm), satisfactory triplet quantum yield (Φ_T=52 %), and long-lived triplet state (τ_T=492 μs), leading to unprecedented performance as a triplet photosensitizer for PDT. Moreover, nanoparticles constructed with such helical bodipy show efficient PDT-mediated antitumor immunity amplification with an ultra-low dose (0.25 μg kg⁻¹), which is several hundred times lower than that of the existing PDT reagents.     

Metal-Organic Layer Delivers 5-Aminolevulinic Acid and Porphyrin for Dual-Organelle-Targeted Photodynamic Therapy

The efficacy of photodynamic therapy (PDT) depends on the subcellular localization of photosensitizers. Herein, we report a dual-organelle-targeted nanoparticle platform for enhanced PDT of cancer. By grafting 5-aminolevulinic acid (ALA) to a Hf₁₂-based nanoscale metal-organic layer (Hf-MOL) via carboxylate coordination, ALA/Hf-MOL enhanced ALA delivery and protoporphyrin IX (PpIX) synthesis in mitochondria, and trapped the Hf-MOL comprising 5,15-di-p-benzoatoporphyrin (DBP) photosensitizers in lysosomes. Light irradiation at 630 nm simultaneously excited PpIX and DBP to generate singlet oxygen and rapidly damage both mitochondria and lysosomes, leading to synergistic enhancement of the PDT efficacy. The dual-organelle-targeted ALA/Hf-MOL outperformed Hf-MOL in preclinical PDT studies, with a 2.7-fold lower half maximal inhibitory concentration in cytotoxicity assays in vitro and a 3-fold higher cure rate in a colon cancer model in vivo.     

Photodynamic Therapy Efficacy Enhanced by Dynamics: The Role of Charge Transfer and Photostability in the Selection of Photosensitizers

Progress in the photodynamic therapy (PDT) of cancer should benefit from a rationale to predict the most efficient of a series of photosensitizers that strongly absorb light in the phototherapeutic window (650–800 nm) and efficiently generate reactive oxygen species (ROS=singlet oxygen and oxygen‐centered radicals). We show that the ratios between the triplet photosensitizer–O₂ interaction rate constant (k_D) and the photosensitizer decomposition rate constant (k_d), k_D/k_d, determine the relative photodynamic activities of photosensitizers against various cancer cells. The same efficacy trend is observed in vivo with DBA/2 mice bearing S91 melanoma tumors. The PDT efficacy intimately depends on the dynamics of photosensitizer–oxygen interactions: charge transfer to molecular oxygen with generation of both singlet oxygen and superoxide ion (high k_D) must be tempered by photostability (low k_d). These properties depend on the oxidation potential of the photosensitizer and are suitably combined in a new fluorinated sulfonamide bacteriochlorin, motivated by the rationale.     

Elucidation of the Intersystem Crossing Mechanism in a Helical BODIPY for Low‐Dose Photodynamic Therapy

Intersystem crossing (ISC) of triplet photosensitizers is a vital process for fundamental photochemistry and photodynamic therapy (PDT). Herein, we report the co‐existence of efficient ISC and long triplet excited lifetime in a heavy atom‐free bodipy helicene molecule. Via theoretical computation and time‐resolved EPR spectroscopy, we confirmed that the ISC of the bodipy results from its twisted molecular structure and reduced symmetry. The twisted bodipy shows intense long wavelength absorption (?=1.76×10⁵ m ^?1 cm^?1 at 630 nm), satisfactory triplet quantum yield (Φ_T=52 %), and long‐lived triplet state (τ_T=492 μs), leading to unprecedented performance as a triplet photosensitizer for PDT. Moreover, nanoparticles constructed with such helical bodipy show efficient PDT‐mediated antitumor immunity amplification with an ultra‐low dose (0.25 μg kg^?1), which is several hundred times lower than that of the existing PDT reagents.     

Gadolinium(III) Porpholactones as Efficient and Robust Singlet Oxygen Photosensitizers

Construction of Gd^III photosensitizers is important for designing theranostic agents owing to the unique properties arising from seven unpaired f electrons of the Gd³⁺ ion. Combining these with the advantages of porpholactones with tunable NIR absorption, we herein report the synthesis of Gd^III complexes Gd‐1 – 4 ( 1 , porphyrin; 2 , porpholactone; 3 and 4 , cis‐ and trans‐porphodilactone, respectively) and investigated their function as singlet oxygen (¹O₂) photosensitizers. These Gd complexes displayed ¹O₂ quantum yields (Φ_Δs) from 0.64–0.99 with the order Gd‐1 < Gd‐2 < Gd‐3 < Gd‐4 . The gradually enhanced ¹O₂ sensitization after β‐oxazolone moiety replacement was ascribed to the narrowing of the energy gap (ΔE) between the lowest triplet states (T₁) of the ligand and the energy level of the ¹Δ_g→³Σ_g transition of ¹O₂. In particular, Gd‐4 is capable of excitation in the visible to NIR region (400–700 nm) with a quantum yield near unity. These Gd complexes were first demonstrated as efficient photosensitizers in photocatalysis such as oxidative C?H bond functionalization of secondary or tertiary amines, and the oxygenation of the natural product cholesterol. Finally, after glycosylation, these water‐soluble Gd complexes showed potential applications in photodynamic therapy (PDT) in HeLa cells. This work revealed that Gd^III complexes of “bioinspired” β‐modified porpholactones are efficient NIR photosensitizers and form a chemical basis to construct appealing photocatalysts and theranostic agents based on lanthanides.     

Activatable Type I Photosensitizer with Quenched Photosensitization Pre and Post Photodynamic Therapy

The phototoxicity of photosensitizers (PSs) pre and post photodynamic therapy (PDT), and the hypoxic tumor microenvironment are two major problems limiting the application of PDT. While activatable PSs can successfully address the PS phototoxicity pre PDT, and type I PS can generate reactive oxygen species (ROS) effectively in hypoxic environment, very limited approaches are available for addressing the phototoxicity post PDT. There is virtually no solution available to address all these issues using a single design. Herein, we propose a proof-of-concept on-demand switchable photosensitizer with quenched photosensitization pre and post PDT, which could be activated only in tumor hypoxic environment. Particularly, a hypoxia-normoxia cycling responsive type I PS TPFN-AzoCF₃ was designed to demonstrate the concept, which was further formulated into TPFN-AzoCF₃ nanoparticles (NPs) using DSPE-PEG-2000 as the encapsulation matrix. The NPs could be activated only in hypoxic tumors to generate type I ROS during PDT treatment, but remain non-toxic in normal tissues, pre or after PDT, thus minimizing side effects and improving the therapeutic effect. With promising results in in vitro and in vivo tumor treatment, this presented strategy will pave the way for the design of more on-demand switchable photosensitizers with minimized side effects in the future.     

Emodin-Based Nanoarchitectonics with Giant Two-Photon Absorption for Enhanced Photodynamic Therapy

Two-photon-excited photodynamic therapy (TPE-PDT) has significant advantages over conventional photodynamic therapy (PDT). However, obtaining easily accessible TPE photosensitizers (PSs) with high efficiency remains a challenge. Herein, we demonstrate that emodin (Emo), a natural anthraquinone (NA) derivative, is a promising TPE PS with a large two-photon absorption cross-section (TPAC: 380.9 GM) and high singlet oxygen (¹O₂) quantum yield (31.9 %). When co-assembled with human serum albumin (HSA), the formed Emo/HSA nanoparticles (E/H NPs) possess a giant TPAC (4.02×10⁷ GM) and desirable ¹O₂ generation capability, thus showing outstanding TPE-PDT properties against cancer cells. In vivo experiments reveal that E/H NPs exhibit improved retention time in tumors and can ablate tumors at an ultra-low dosage (0.2 mg/kg) under an 800 nm femtosecond pulsed laser irradiation. This work is beneficial for the use of natural extracts NAs for high-efficiency TPE-PDT.     

Co-delivery of enzymes and photosensitizers via metal-phenolic network capsules for enhanced photodynamic therapy

The intrinsic hypoxic tumor microenvironment and limited accumulation of photosensitizers（PSs） result in unsatisfied efficiency of photodynamic therapy（PDT）.To enhance the PDT efficiency against solid tumors,a functional oxygen self-supplying and PS-delivering nanosystem is fabricated via the combination of catalase（CAT）,chlorin e6（Ce6） and metal-phenolic network（MPN） capsule.It is demonstrated that the CAT encapsulated in the capsules（named CCM capsules） could catalyze the degradation of hydrog...     

Strategy for Tuning the Photophysical Properties of Photosensitizers for Use in Photodynamic Therapy

A novel approach for tuning spectral properties, as well as minimizing aggregation, in zinc porphyrin and zinc phthalocyanine‐based compounds is presented. Particular emphasis is placed on use of these compounds as photosensitizers in photodynamic therapy (PDT). To accomplish this aim, a bulky hydrophobic cation, trihexyltetradecylphosphonium, is paired with anionic porphyrin and phthalocyanine dyes to produce a group of uniform materials based on organic salts (GUMBOS) that absorb at longer wavelengths with high molar absorptivity and high photostability. Nanoparticles derived from these GUMBOS possess positively charged surfaces with high zeta potential values, which are highly desirable for PDT. Upon irradiation at longer wavelengths, these GUMBOS produced singlet oxygen with greater efficiency as compared to the respective parent dyes.     

Synthesis of protein‐assisted aqueous Ag2S quantum dots in the bovine serum albumin solution

A one‐step method was developed for preparing Ag₂S quantum dots (QDs) using a common protein [bovine serum albumin (BSA)] to entrap QDs precursors (BSA–Ag⁺). Fluorescence (FL) and ultraviolet spectra showed that the molar ratio of Ag⁺/BSA, temperature, and pH are the crucial factors for the quality of QDs. The QDs absorption wavelength and emission wavelength were about 340 and 450 nm. The average QDs particle size was estimated to be less than 5 nm, determined by transmission electron microscopy. The X‐ray power diffraction and XPS results showed that the synthesized product was indeed monoclinic Ag₂S. With Fourier transform infrared spectra and thermogravimetry analysis, there might be conjugated bonds between Ag₂S QDs and –OH, –NH, and –SH groups in BSA. In addition, FL spectra suggest that the designed QDs can produce static quenching with BSA and the Stern–Volmer quenching constant (K_sv) was calculated as 2.145 × 10⁴. Copyright © 2014 John Wiley & Sons, Ltd.     

Plasmon-resonance-enhanced visible-light photocatalytic activity of Ag quantum dots/TiO2 microspheres for methyl orange degradation

We successfully prepared Ag quantum dots modified TiO₂ microspheres by facile solvothermal and calcination method. The as-prepared Ag quantum dots/TiO₂ microspheres were characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The Ag quantum dots/TiO₂ photocatalyst showed excellent visible light absorption and efficient photocatalytic activity for methyl orange degradation. And the sample with the molar ratio of 0.05 (Ag to Ti) showed the best visible light photocatalytic activity for methyl orange degradation, mainly because of the surface plasmon resonance (SPR) effects of Ag quantum dots to generate electron and hole pairs for enhanced visible light photocatalysis. Finally, possible visible light photocatalytic mechanism of Ag quantum dots/TiO₂ microspheres for methyl orange degradation was proposed in detail.     

Type I Photosensitizer Targeting G-Quadruplex RNA Elicits Augmented Immunity for Cancer Ablation

Type I photodynamic therapy (PDT) represents a promising treatment modality for tumors with intrinsic hypoxia. However, type I photosensitizers (PSs), especially ones with near infrared (NIR) absorption, are limited and their efficacy needs improvement via new targeting tactics. We develop a NIR type I PS by engineering acridinium derived donor-π-acceptor systems. The PS exhibits an exclusive type I PDT mechanism due to effective intersystem crossing and disfavored energy transfer to O₂, and shows selective binding to G-quadruplexes (G4s) via hydrogen bonds identified by a molecular docking study. Moreover, it enables fluorogenic detection of G4s and efficient O₂⋅⁻ production in hypoxic conditions, leading to immunogenic cell death and substantial variations of gene expression in RNA sequencing. Our strategy demonstrates augmented antitumor immunity for effective ablation of immunogenic cold tumor, highlighting its potential of RNA-targeted type I PDT in precision cancer therapy.