Feasibility Study on Quantitative Measurements of Singlet Oxygen Generation Using Singlet Oxygen Sensor Green

Determination of singlet oxygen quantum yield based on the behavior of solvent dimethyl sulfoxide oxidation by singlet oxygen

BACKGROUND

Photodynamic therapy (PDT) is emerging as a promising cancer treatment. The PDT efficacy is primarily attributed to the generation of singlet oxygen (1O2), stemming from the integrated effects of the photosensitizer, oxygen, and light. The singlet oxygen quantum yield (ΦΔ) serves as a bridge that links these parameters to the overall efficacy of PDT. The near-infrared luminescence of 1O2 provides a direct way for determining ΦΔ, but suffers from a poor signal-to-noise ratio. While the chemical trap probe method is detection-friendly, but it has a strict requirement for the excitation wavelength. Therefore, the existing methods for ΦΔ measurement are insufficient.

RESULTS

In this work, we developed an approach to determine ΦΔ of a broader range of photosensitizers using only the commonly used solvent dimethyl sulfoxide (DMSO), which can be oxidized by 1O2 to dimethyl sulfone. This method establishes the relationship between 1O2 production and changes in DMSO absorption spectra, eliminating the need for additional chemical probes. This method was validated by measuring the ΦΔ of rose bengal (RB) through systematic changes in absorption spectrum of DMSO under various RB concentrations and different excitation light power densities. Moreover, the ΦΔ of hematoporphyrin monomethyl ether (HMME), as determined by this method, is consistent with measurements obtained using the 1,3-diphenylisobenzofuran (DPBF) trapping probe. This consistency further validates the reliability of this method.

SIGNIFICANCE AND NOVELTY

This work presents a direct, probe-free method to determine ΦΔ, reducing potential interference and expanding the range of useable excitation wavelengths. Its ability to measure ΦΔ using only DMSO enhances the accuracy of photosensitizer measurement, and broadens the applicability of the method to a wide range of samples, thereby advancing research on the properties of photosensitizers and further promoting the development of PDT.

Sonodynamic Therapy for HER2+ Breast Cancer with Iodinated Heptamethine Cyanine-Trastuzumab Conjugate

The first example of sonodynamic therapy (SDT) with a cyanine dye-antibody conjugate is reported. The aim of this study was to evaluate the sonodynamic efficacy of a trastuzumab-guided diiodinated heptamethine cyanine-based sensitizer, 2ICy7-Ab, versus its non-iodinated counterpart, Cy7-Ab, in a human epidermal growth factor receptor 2-positive (HER2+) xenograft model. In addition, the combined sonodynamic and photodynamic (PDT) effects were investigated. A single intravenous injection of 2ICy7-Ab followed by sonication or combined sonication and photoirradiation in mice resulted in complete tumor growth suppression compared with the nontreated control and showed no detectable toxicity to off-target tissues. In contrast, Cy7-Ab provided only a moderate therapeutic effect (~1.4-1.6-fold suppression). SDT with 2ICy7-Ab resulted in a 3.5-fold reduction in tumor volume within 45 days and exhibited 13-fold greater tumor suppression than PDT alone. In addition, 2ICy7-Ab showed more durable sonostability than photostability. The sonotoxicity of the iodinated versus noniodinated counterparts is attributed to the increased generation of hydroxyl radicals, superoxide, and singlet oxygen. We observed no significant contribution of PDT to the efficacy of the combined SDT and PDT, indicating that SDT with 2ICy7-Ab is superior to PDT alone. These new findings set the stage for the application of cyanine-antibody conjugates for fluorescently monitored targeted sonodynamic treatment of cancer.

Singlet Oxygen Photophysics: From Liquid Solvents to Mammalian Cells

Molecular oxygen, O2, has long provided a cornerstone for studies in chemistry, physics, and biology. Although the triplet ground state, O2(X3Σg-), has garnered much attention, the lowest excited electronic state, O2(a1Δg), commonly called singlet oxygen, has attracted appreciable interest, principally because of its unique chemical reactivity in systems ranging from the Earth's atmosphere to biological cells. Because O2(a1Δg) can be produced and deactivated in processes that involve light, the photophysics of O2(a1Δg) are equally important. Moreover, pathways for O2(a1Δg) deactivation that regenerate O2(X3Σg-), which address fundamental principles unto themselves, kinetically compete with the chemical reactions of O2(a1Δg) and, thus, have practical significance. Due to technological advances (e.g., lasers, optical detectors, microscopes), data acquired in the past ∼20 years have increased our understanding of O2(a1Δg) photophysics appreciably and facilitated both spatial and temporal control over the behavior of O2(a1Δg). One goal of this Review is to summarize recent developments that have broad ramifications, focusing on systems in which oxygen forms a contact complex with an organic molecule M (e.g., a liquid solvent). An important concept is the role played by the M+•O2-• charge-transfer state in both the formation and deactivation of O2(a1Δg).

Singlet oxygen detection in vivo is hindered by nonspecific SOSG staining

Singlet oxygen is considered an important cell damaging agent due to its propensity to react with organic compounds. This drives the interest in developing methods for determination of 1O2. Simplicity of application and high sensitivity makes fluorescent probes a popular choice for in vivo 1O2 detection. Despite its proclaimed cell-impermeability, the commercially available Singlet Oxygen Sensor Green (SOSG) is widely applied to support assertions of 1O2 involvement in cell and tissue damage. Our investigation, however, demonstrate that different microbial species and cancer cells become fluorescent when exposed to SOSG under conditions which exclude generation of 1O2. Cells, permeabilized with chlorhexidine or by heat exposure under anaerobic conditions, exhibited SOSG fluorescence. Permeabilized cells could be stained with SOSG even 24 h post-permeabilization. Since SOSG is cell impermeable, the main factor that led to fluorescent staining was plasma membrane damage. Spectral analyses of different batches of SOSG revealed that SOSG endoperoxide (SOSG-EP) did not increase even after prolonged storage under the recommended conditions. The commercial preparations of SOSG, however, were not SOSG-EP free, which can produce erroneous results when SOSG staining is used as a proof of singlet oxygen production in vivo.

Core-Shell Interface Engineering Strategies for Modulating Energy Transfer in Rare Earth-Doped Nanoparticles

Rare earth-doped nanoparticles (RENPs) are promising biomaterials with substantial potential in biomedical applications. Their multilayered core-shell structure design allows for more diverse uses, such as orthogonal excitation. However, the typical synthesis strategies-one-pot successive layer-by-layer (LBL) method and seed-assisted (SA) method-for creating multilayered RENPs show notable differences in spectral performance. To clarify this issue, a thorough comparative analysis of the elemental distribution and spectral characteristics of RENPs synthesized by these two strategies was conducted. The SA strategy, which avoids the partial mixing stage of shell and core precursors inherent in the LBL strategy, produces RENPs with a distinct interface in elemental distribution. This unique elemental distribution reduces unnecessary energy loss via energy transfer between heterogeneous elements in different shell layers. Consequently, the synthesis method choice can effectively modulate the spectral properties of RENPs. This discovery has been applied to the design of orthogonal RENP biomedical probes with appropriate dimensions, where the SA strategy introduces a refined inert interface to prevent unnecessary energy loss. Notably, this strategy has exhibited a 4.3-fold enhancement in NIR-II in vivo imaging and a 2.1-fold increase in reactive oxygen species (ROS)-related photodynamic therapy (PDT) orthogonal applications.

Phloroglucinol-Based Carbon Quantum Dots/Polyurethane Composite Films: How Structure of Carbon Quantum Dots Affects Antibacterial and Antibiofouling Efficiency of Composite Films

Nowadays, bacteria resistance to many antibiotics is a huge problem, especially in clinics and other parts of the healthcare system. This critical health issue requires a dynamic approach to produce new types of antibacterial coatings to combat various pathogen microbes. In this research, we prepared a new type of carbon quantum dots based on phloroglucinol using the bottom-up method. Polyurethane composite films were produced using the swell-encapsulation-shrink method. Detailed electrostatic force and viscoelastic microscopy of carbon quantum dots revealed inhomogeneous structure characterized by electron-rich/soft and electron-poor/hard regions. The uncommon photoluminescence spectrum of carbon quantum dots core had a multipeak structure. Several tests confirmed that carbon quantum dots and composite films produced singlet oxygen. Antibacterial and antibiofouling efficiency of composite films was tested on eight bacteria strains and three bacteria biofilms.

On-Site Quantitative Visualization of Singlet Oxygen in Crops via an Organic Small Molecule-Based Ratiometric Fluorescent Probe and a Mobile Fluorescence Analysis Device

Singlet oxygen (1O2) plays imperative roles in a variety of biotic or abiotic stresses in crops. The change of its concentration within a crop is closely related to the crop growth and development. Accordingly, there is an urgent need to develop an efficient analytical method for on-site quantitative detection of 1O2 in crops. Here, we judiciously constructed a novel ratiometric fluorescent probe, SX-2, for the detection of 1O2 in crops. Upon treating with 1O2, probe SX-2 displayed highly selective ratiometric fluorescence response, which is favorable for the quantitative detection of 1O2. Concurrently, the fluorescence solution color of probe SX-2 was varied, obviously from blue to yellow, indicating that the probe is beneficial for on-site detection by the naked eye. Sensing reaction mechanism studies showed that the 2,3-diphenyl imidazole group in SX-2 could function as a new selective recognition group for 1O2. Probe SX-2 was utilized for the detection of photoirradiation-induced 1O2 and endogenous 1O2 in living cells. The changes in the 1O2 level in zebrafish were also tracked by fluorescence imaging. In addition, the production of 1O2 in crop leaves under a light source of different wavelengths was studied. The results demonstrated more 1O2 were produced under a light source of 365 nm. Furthermore, to achieve on-site quantitative detection, a mobile fluorescence analysis device has been made. Probe SX-2 and mobile fluorescence analysis device were capable of on-site quantitative detecting of 1O2 in crops. The method developed herein will be convenient for the on-site quantitative measurement of 1O2 in distinct crops.

Red Light-Triggered Anti-Angiogenic and Photodynamic Combination Therapy of Age-Related Macular Degeneration

Choroidal neovascularization (CNV) is the key pathological event of wet age-related macular degeneration (wAMD) leading to irreversible vision loss. Currently, anti-angiogenic therapy with anti-vascular endothelial growth factor (VEGF) agents has become the standard treatment for wAMD, while it is still subject to several limitations, including the safety concerns of monthly intravitreal administration and insufficient efficacy for neovascular occlusion. Combined therapy with photodynamic therapy (PDT) and anti-angiogenic agents has emerged as a novel treatment paradigm. Herein, a novel and less-invasive approach is reported to achieve anti-angiogenic and photodynamic combination therapy of wAMD by intravenous administration of a photoactivatable nanosystem (Di-DAS-VER NPs). The nanosystem is self-assembled by reactive oxygen species (ROS)-sensitive dasatinib (DAS) prodrug and photosensitizer verteporfin (VER). After red-light irradiation to the diseased eyes, intraocular release of anti-angiogenic DAS is observed, together with selective neo-vessels occlusion by VER-generated ROS. Notably, Di-DAS-VER NPs demonstrates promising therapeutic efficacy against CNV with minimized systemic toxicity. The study enables an efficient intravenous wAMD therapy by integrating a photoactivation process with combinational therapeutics into one simple nanosystem.

Recent advances in biosensors for real time monitoring of pH, temperature, and oxygen in chronic wounds

Chronic wounds are among the major healthcare issues affecting millions of people worldwide with high rates of morbidity, losses of limbs and mortality. Microbial infection in wounds is a severe problem that can impede healing of chronic wounds. Accurate, timely and early detection of infections, and real time monitoring of various wound healing biomarkers related to infection can be significantly helpful in the treatment and care of chronic wounds. However, clinical methodologies of periodic assessment and care of wounds require physical visit to wound care clinics or hospitals and time-consuming frequent replacement of wound dressing patches, which also often adversely affect the healing process. Besides, frequent replacements of wound dressings are highly expensive, causing a huge amount of burden on the national health care systems. Smart bandages have emerged to provide in situ physiochemical surveillance in real time at the wound site. These bandages integrate smart sensors to detect the condition of wound infection based on various parameters, such as pH, temperature and oxygen level in the wound which reduces the frequency of changing the wound dressings and its associated complications. These devices can continually monitor the healing process, paving the way for tailored therapy and improved quality of patient's life. In this review, we present an overview of recent advances in biosensors for real time monitoring of pH, temperature, and oxygen in chronic wounds in order to assess infection status. We have elaborated the recent progress in quantitative monitoring of several biomarkers important for assessing wounds infection status and its detection using smart biosensors. The review shows that real-time monitoring of wound status by quantifying specific biomarkers, such as pH, temperature and tissue oxygenation to significantly aid the treatment and care of chronic infected wounds.

Modulating Electronic Structure Engineering of Atomically Dispersed Cobalt Catalyst in Fenton-like Reaction for Efficient Degradation of Organic Pollutants

Currently, the lack of model catalysts limits the understanding of the catalytic essence. Herein, we report the functional group modification of model single atom catalysts (SACs) with an accurately regulated electronic structure for accelerating the sluggish kinetics of the Fenton-like reaction. The amino-modified cobalt phthalocyanine anchored on graphene (CoPc/G-NH2) shows superior catalytic performance in the peroxymonosulfate (PMS) based Fenton-like reaction with Co mass-normalized pseudo-first-order reaction rate constants (kobs, 0.2935 min-1), which is increased by 4 and 163 times compared to those of CoPc/G (0.0737 min-1) and Co3O4/G (0.0018 min-1). Density functional theory (DFT) calculations demonstrate that the modification of the -NH2 group narrows the gap between the d-band center and the Fermi level of a single Co atom, which strengthens the charge transfer rate at the reaction interface and reduces the free energy barrier for the activation of PMS. Moreover, the scale-up experiment realizes 100% phenol removal at 7200-bed volumes during 240 h continuous operation without obvious decline in catalytic performance. This work provides in-depth insight into the catalytic mechanism of Fenton-like reactions and demonstrates the electronic engineering of SACs as an effective strategy for improving the Fenton-like activity to achieve the goal of practical application.

A New Insight into the Singlet Oxygen Mechanism for Photodynamic Therapy

Modern photodynamic therapy has been built on the mechanism of the interaction between the photosensitizer (porphyrin derivatives) and oxygen to produce singlet oxygen, which relies on energy transfer from the triplet excited state (T₁) of porphyrin to the excited state of oxygen. In this process, the energy transfer from the singlet excited state (S₁) of porphyrin to oxygen is believed to be not pronounced as the rapid decay of S₁ and the large energy mismatch. Here, we have evidenced the existence of an energy transfer between S₁ and oxygen, which can contribute to the production of singlet oxygen. For hematoporphyrin monomethyl ether (HMME), the Stern-Volmer constant of S₁ (K_SV') is 0.023 kPa^-1, according to the oxygen concentration-dependent steady fluorescence intensities. In addition, fluorescence dynamic curves of S₁ under various oxygen concentrations have also been measured through ultrafast pump probe experiments to further verify our results.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Screening of antioxidant capacity of Nepali medicinal plants with a novel singlet oxygen scavenging assay

Pollutant exposure due to industrial development increases oxidative stress in human bodies. Dietary intake of antioxidant shows a protective effect against oxidative damage induced by oxidative stress. Therefore, the development of natural antioxidants is needed. In this study, the antioxidant activities of some Nepali medicinal plant extracts were measured. Using Rose bengal and 3,3',5,5'-tetramethylbenzidine, a novel assay was utilized to evaluate the singlet oxygen scavenging capacity, and showed a strong correlation with other antioxidant assays. Also, antioxidant capacities based on four assays including the singlet oxygen scavenging assay were highly correlated (≥ 0.858) with the total phenolic contents in the medicinal plant extracts. Among the selected extracts, Persicaria capitata, Elaphoglossum marginatum and Eurya acuminata showed the highest antioxidant capacities. Overall, this study presents a novel approach for evaluating singlet oxygen scavenging capacity, and performed a screening of antioxidant capacities of 54 Nepali herbal medicines.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01175-z.

Effect of Solubilizing Group on the Antibacterial Activity of Heptamethine Cyanine Photosensitizers

Antibiotic resistance of pathogenic bacteria dictates the development of novel treatment modalities such as antimicrobial photodynamic therapy (APDT) utilizing organic dyes termed photosensitizers that exhibit a high cytotoxicity upon light irradiation. Most of the clinically approved photosensitizers are porphyrins that are poorly excitable in the therapeutic near-IR spectral range. In contrast, cyanine dyes function well in the near-IR region, but their phototoxicity, in general, is very low. The introduction of iodine atoms in the cyanine molecules was recently demonstrated to greatly increase their phototoxicity. Herein, we synthesized a series of the new iodinated heptamethine cyanine dyes (ICy7) containing various solubilizing moieties, i.e., negatively charged carboxylic (ICy7COOH) and sulfonic (ICy7SO₃H) groups, positively charged triphenylphosphonium (ICy7PPh₃), triethylammonium (ICy7NEt₃) and amino (ICy7NH₂) groups, and neutral amide (ICy7CONHPr) group. The effect of these substituents on the photodynamic eradication of Gram-positive (S. aureus) and Gram-negative (E. coli and P. aeruginosa) pathogens was studied. Cyanine dyes containing the amide and triphenylphosphonium groups were found to be the most efficient for eradication of the investigated bacteria. These dyes are effective at low concentrations of 0.05 µM (33 J/cm²) for S. aureus, 50 µM (200 J/cm²) for E. coli, and 5 µM (100 J/cm²) for P. aeruginosa and considered, therefore, promising photosensitizers for APDT applications. The innovation of the new photosensitizers consisted of a combination of the heavy-atom effect that increases singlet oxygen generation with the solubilizing group's effect improving cell uptake, and with effective near-IR excitation. Such a combination helped to noticeably increase the APDT efficacy and should pave the way for the development of more advanced photosensitizers for clinical use.

Dual drive acute lethal toxicity of methylene blue to Daphnia magna by polystyrene microplastics and light

Microplastics (MPs) can adsorb and influence the toxicity of traditional pollutants significantly. Although the complex toxicity of MPs and molecular pollutants were frequently reported, rare work has been done on the influence of MPs on the phototoxicity of photosensitive pollutants under light illumination condition. Herein, polystyrene microplastics (PS) (~1 μm in diameter, 5.0 mg/L) was used as a model MP to investigate its influence on the phototoxicity of a soluble blue dye, methylene blue (MB) using Daphnia magna as a model organism. The results indicate that PS could adsorb MB effectively and quickly, thus led to concentrated MB on PS/water interface. D. magna ingested MB-adsorbed PS very quickly within tens of minutes. Although MB or PS alone led to negligible lethal phototoxicity to D. magna, PS significantly enhanced the lethal phototoxicity of MB (0.25 mg/L) to D. magna after light illumination (10 h) with the survival rate decreased by 63.3 % compared with the control in the dark. Further, the phototoxicity of MB was found positively consistent with PS concentration from 0.50 mg/L to 7.50 mg/L. The singlet oxygen fluorescence assay indicates that the presence of PS did not increase the total amount of singlet oxygen in the aquatic environment but increased the local concentration in the gut area via non-selective ingestion of D. magna. High level singlet oxygen generated in the gut might possibly be the main reason that led to the massive death of D. magna. Surface adsorption of photosensitive pollutants may transform inert MPs into persistent solid sources of singlet oxygen production and become a new potential lethal threat to aquatic small organisms and ecological equilibrium. This kind of MPs and light dual drive phototoxicity of photosensitive pollutants needs to paid more attention in understanding the uncertain ecological risk of MPs.

Enhancement effect of 2, 3-dimethyl maleic acid on luminol chemiluminescence reactions and its application in detection of sequence-specific DNA related to hepatitis B virus

2, 3-dimethyl maleic acid (DMMA) was found to enhance luminol-H₂O₂ chemiluminescent (CL) reactions, among which the strongest enhancement effect was observed by using polyethyleneimine-templated gold nanoclusters (PEI-Au NCs) as the catalyst. With the addition of DMMA, the CL signal of the PEI-Au NCs-catalyzed luminol-H₂O₂ reaction enhanced about 630-fold, and a flash-type CL profile was obtained. Mechanism studies showed that the luminophore was still 3-aminophthalate anions in the excited state (3-APA*), and superoxide radical (O₂^·-) played an important role during the CL process. Under the optimized experimental conditions, the lowest concentration of PEI-Au NCs can be detected was 0.168 nM which was 82-fold lower than that without an enhancer. Furthermore, the catalytic activity of biotinylated PEI-Au NCs in the DMMA-enhanced luminol system was similar to PEI-Au NCs, providing a good opportunity for the development of CL bioanalysis platforms using PEI-Au NCs as the label. Thus, the DMMA-enhanced luminol-H₂O₂ system was applied to the CL detection of sequence-specific DNA related to the hepatitis B virus (HBV) using PEI-Au NCs as the label. The CL platform exhibited linearly enhanced CL response with the increasing amount of target DNA ranging from 0.0025 to 0.5 pmol. As low as 0.002 pmol of HBV DNA could be sensitively detected, which was superior to the previously reported methods.

Hydrogen sulfide decreases photodynamic therapy outcome through the modulation of the cellular redox state

Photodynamic therapy (PDT) is a non-surgical treatment that has been approved for its human medical use in many cancers. PDT involves the interaction of a photosensitizer (PS) with light. The amino acid 5- aminolevulinic acid (ALA) can be used as a pro-PS, leading to the synthesis of Protoporphyrin IX. Hydrogen sulfide (H₂S) is an endogenously produced gas that belongs to the gasotransmitter family, which can diffuse through biological membranes and have relevant physiological effects such as cardiovascular functions, vasodilatation, inflammation, cell cycle and neuro-modulation. It was also proposed to have cytoprotective effects. We aimed to study the modulatory effects of H₂S on ALAPDT in the mammary adenocarcinoma cell line LM2. Exposure of the cells to NaHS (donor of H₂S) in concentrations up to 10 mM impaired the response to ALA-PDT in a dose-dependent manner. The addition of 3 doses of NaHS showed the highest effect. This decreased response to the photodynamic treatment was correlated to an increase in the GSH levels, catalase activity, a dose dependent reduction of PpIX and increased intracellular ALA, decreased levels of oxidized proteins and a decrease of PDT-induced ROS. NaHS also reduced the levels of singlet oxygen in an in vitro assay. H₂S also protected other cells of different origins against PDT mediated by ALA and other PSs. These results suggest that H₂S has a role in the modulation of the redox state of the cells, and thus impairs the response to ALA-PDT through multifactor pathways. These findings could contribute to developing new strategies to improve the effectiveness of PDT particularly mediated by ALA or other ROS-related treatments.

A-DA'D-A Structured Organic Phototheranostics for NIR-II Fluorescence/Photoacoustic Imaging-Guided Photothermal and Photodynamic Synergistic Therapy

Multimodal imaging-guided combinational phototherapies triggered by a single near-infrared (NIR) laser are highly desirable. However, their development is still a big challenge. Herein, we have developed an "acceptor-donor-acceptor'-donor-acceptor" structured organic phototheranostics (Y16-Pr) with strong light-harvesting ability in the NIR region. After being modified with polyethylene glycol (PEG), the obtained biocompatible nanoparticles (Y16-Pr-PEG NPs) could conduct NIR-II fluorescence imaging (FLI) and photoacoustic imaging (PAI) and perform photothermal therapy (PTT) and photodynamic therapy (PDT) simultaneously. Notably, Y16-Pr-PEG NPs showed an impressive photothermal conversion efficiency (PCE) of 82.4% under 808 nm laser irradiation. The irradiated NPs could also produce hydroxyl radicals (•OH) and singlet oxygen (¹O₂) for type I and type II PDT, respectively. In vivo and in vitro experiments revealed that the Y16-Pr-PEG NPs significantly inhibit tumor cell growth without apparent toxic side effects under laser irradiation. Overall, the single-laser-triggered multifunctional phototheranostic Y16-Pr-PEG NPs can achieve NIR-II FLI/PAI-guided synergistic PTT/PDT against tumors.

Blood Plasma Stabilized Gold Nanoclusters for Personalized Tumor Theranostics

Simple Summary

Cancer is a disease that has a high fatality rate over the world. Nanotechnology is one of the most promising current approaches for developing novel diagnostic and treatment methods in accomplishing more personalized medicine. Personalized gold nanoclusters have potential to be used in cancer theranostics. We demonstrate that biocompatible gold nanoclusters could be synthesized directly in human blood plasma. Such gold nanoclusters have a wide photoluminescence band in the optical tissue window and generate reactive oxygen species under irradiation with visible light, thus are suitable for cancer theranostics.

Abstract

Personalized cancer theranostics has a potential to increase efficiency of early cancer diagnostics and treatment, and to reduce negative side-effects. Protein-stabilized gold nanoclusters may serve as theranostic agents. To make gold nanoclusters personalized and highly biocompatible, the clusters were stabilized with human plasma proteins. Optical properties of synthesized nanoclusters were investigated spectroscopically, and possible biomedical application was evaluated using standard cell biology methods. The spectroscopic investigations of human plasma proteins stabilized gold nanoclusters revealed that a wide photoluminescence band in the optical tissue window is suitable for cancer diagnostics. High-capacity generation of singlet oxygen and other reactive oxygen species was also observed. Furthermore, the cluster accumulation in cancer cells and the photodynamic effect were evaluated. The results demonstrate that plasma proteins stabilized gold nanoclusters that accumulate in breast cancer cells and are non-toxic in the dark, while appear phototoxic under irradiation with visible light. The results positively confirm the utility of plasma protein stabilized gold nanoclusters for the use in cancer diagnostics and treatment.

Screening of Chitosan Derivatives-Carbon Dots Based on Antibacterial Activity and Application in Anti-Staphylococcus aureus Biofilm

Introduction

Pathogenic bacteria, especially the ones with highly organized, systematic aggregating bacteria biofilm, would cause great harm to human health. The development of highly efficient antibacterial and antibiofilm functional fluorescent nanomaterial would be of great significance.

Methods

This paper reports the preparation of a series of antibacterial functional carbon dots (CDs) with chitosan (CS) and its derivatives as raw materials through one-step route, and the impact of various experiment parameters upon the optical properties and the antibacterial abilities have been explored, including the structures of the raw materials, excipients, and solvents.

Results

The CDs prepared by quaternary ammonium salt of chitosan (QCS) and ethylenediamine (EDA) exhibit multiple antibacterial effects through membrane breaking, DNA and protein destroying, and the production of singlet oxygen. The CDs showed excellent broad-spectrum inhibitory activity against a variety of bacteria (Gram-positive and negative bacteria), in particular, to the biofilm of Staphylococcus aureus with minimum inhibitory concentration at 10 µg/mL, showing great potential in killing bacteria and biofilms. The biocompatibility experiments proved that QCS-EDA-CDs are non-toxic to human normal hepatocytes and have low haemolytic effect. Furthermore, the prepared QCS-EDA-CDs have been successfully used in bacterial and biofilm imaging thanks to their excellent optical properties.

Conclusion

This paper explored the preparation and application of functional CDs, which can be used as the visual probe and therapeutic agents in the treatment of infections caused by bacteria and biofilm.

Hyaluronic acid carrier-based photodynamic therapy for head and neck squamous cell carcinoma

PURPOSE

Conventional photosensitizers for photodynamic therapy (PDT) typically have wide tissue distribution and poor water solubility. A hyaluronic acid (HA) polymeric nanoparticle with specific lymphatic uptake and highly water solubility was developed to deliver pyropheophorbide-a (PPa) for locally advanced head and neck squamous cell carcinoma (HNSCC) treatment.

METHODS AND RESULTS

PPa was chemically conjugated to the HA polymeric nanoparticle via an adipic acid dihydrazide (ADH) linker. The conjugates were injected subcutaneously in a region near the tumor. Near-infrared (NIR) imaging was used to monitor distribution, and diode laser was used to activate PPa. The singlet oxygen generation efficiency of PPa was not affected by conjugation to HA nanoparticles at a PPa loading degree of 1.89 w.t.%. HA-ADH-PPa inhibited human HNSCC MDA-1986 cell growth only when photo-irradiation was applied. After HA-ADH-PPa treatment and radiation, NU/NU mice bearing human HNSCC MDA-1986 tumors showed reduced tumor growth and significantly enhanced survival time compared with an untreated group (p < 0.05).

CONCLUSIONS

These results demonstrate that HA-ADH-PPa could be useful for in vivo locoregional photodynamic therapy of HNSCC.

Scintillator-based radiocatalytic superoxide radical production for long-term tumor DNA damage

Photocatalytic materials absorb photons ranging from ultraviolet to near-infrared light to initiate photocatalytic reactions and have broad application prospects in various fields. However, high-energy ionizing radiations are rarely involved in...

Aggregation-induced emission luminogens for highly effective microwave dynamic therapy

Aggregation-induced emission luminogens (AIEgens) exhibit efficient cytotoxic reactive oxygen species (ROS) generation capability and unique light-up features in the aggregated state, which have been well explored in image-guided photodynamic therapy (PDT). However, the limited penetration depth of light in tissue severely hinders AIEgens as a candidate for primary or adjunctive therapy for clinical applications. Coincidentally, microwaves (MWs) show a distinct advantage for deeper penetration depth in tissues than light. Herein, for the first time, we report AIEgen-mediated microwave dynamic therapy (MWDT) for cancer treatment. We found that two AIEgens (TPEPy-I and TPEPy-PF6) served as a new type of microwave (MW) sensitizers to produce ROS, including singlet oxygen (1O2), resulting in efficient destructions of cancer cells. The results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and live/dead assays reveal that the two AIEgens when activated by MW irradiation can effectively kill cancer cells with average IC-50 values of 2.73 and 3.22 μM, respectively. Overall, the ability of the two AIEgens to be activated by MW not only overcomes the limitations of conventional PDT, but also helps to improve existing MW ablation therapy by reducing the MW dose required to achieve the same therapeutic outcome, thus reducing the occurrence of side-effects of MW radiation.

Semiconducting Polymer Nano-regulators with Cascading Activation for Photodynamic Cancer Immunotherapy

Combination photoimmunotherapy holds promise for tumor suppression; however, smart phototherapeutic agents that only activate their immunotherapeutic action in tumor have been rarely developed, which have the potential advantage of reduced side effect. Herein, we report a semiconducting polymer nano-regulator (SPN T ) with cascading activation for combinational photodynamic immunotherapy of cancer. SPN T  comprises an immunoregulator (M-Trp:  1-methyltryptophan ) conjugating to the side chain of semiconducting polymer backbone using an apoptotic biomarker-cleavable linker. Under near-infrared (NIR) laser irradiation, SPN T  produces singlet oxygen ( 1 O 2 ) to cause  immunogenic apoptosis . Concurrently, the upregulation of apoptotic biomarker triggers the specific cleavage of M-Trp from SPN T , leading to specific intratumoral immunotherapeutic activation. Released M-Trp inhibits  indoleamine 2,3-dioxygenase (IDO) activity, and thus decreases regulatory T cells (Tregs) formation and drives cytotoxic T lymphocytes (CTLs) infiltration. SPN T -mediated combination photodynamic immunotherapy thus reprograms the tumor immune microenvironment (TIME), resulting in efficient suppression of both primary and distant tumors, and inhibition of lung metastasis.

Two-photon activated precision molecular photosensitizer targeting mitochondria

Mitochondria metabolism is an emergent target for the development of novel anticancer agents. It is amply recognized that strategies that allow for modulation of mitochondrial function in specific cell populations need to be developed for the therapeutic potential of mitochondria-targeting agents to become a reality in the clinic. In this work, we report dipolar and quadrupolar quinolizinium and benzimidazolium cations that show mitochondria targeting ability and localized light-induced mitochondria damage in live animal cells. Some of the dyes induce a very efficient disruption of mitochondrial potential and subsequent cell death under two-photon excitation in the Near-infrared (NIR) opening up possible applications of azonia/azolium aromatic heterocycles as precision photosensitizers. The dipolar compounds could be excited in the NIR due to a high two-photon brightness while exhibiting emission in the red part of the visible spectra (600-700 nm). Interaction with the mitochondria leads to an unexpected blue-shift of the emission of the far-red emitting compounds, which we assign to emission from the locally excited state. Interaction and possibly aggregation at the mitochondria prevents access to the intramolecular charge transfer state responsible for far-red emission.

Synthesis of Au@MOF core-shell hybrids for enhanced photodynamic/photothermal therapy

Photodynamic/photothermal therapy (PDT/PTT) has become a research focus of cancer treatment due to the non-invasiveness, spatio-temporal controllability, and effectiveness of repeated treatment. Here, Au@MOF core-shell hybrids were designed and constructed by the layer-by-layer method, and the thickness of the MOF shell can be adjusted by controlling the coordination reaction between the layers. Au nanorod cores mainly produce the PTT effect due to their strong absorbance at 650 nm. The porphyrin ligand in the MOF shell can convert O₂ into ¹O₂ under light conditions, resulting in a high PDT effect. Moreover, the metal node Fe₃O(OAc)₆(H₂O)₃⁺ cluster of the MOF can catalyze the decomposition of H₂O₂ into O₂ to overcome the hypoxic environment of tumors, which further improves the effect of PDT. The combination of the porphyrin ligand in the MOF structure and Au nanorods has promoted the synergistic effects of PDT/PTT. As expected, the results confirmed that Au@MOF hybrids showed no obvious biotoxicity in both cells and animal experiments, and exhibited good biocompatibility. With the synergistic effects of PDT/PTT, cancer cells could be effectively killed and tumor growth could be inhibited. In addition, the modification of folic acid on the surface of Au@MOF can further enrich the hybrids at the tumor site and enhance the inhibitory effect on tumors. These studies have proved that PDT and PTT can be effectively combined and have greater advantages in enhancing the treatment of tumors.

Theranostic Near-Infrared-Active Conjugated Polymer Nanoparticles

Conjugated polymer nanoparticles (CPNs) based on a common solar cell material (PTB7) have been prepared, and their potential in theranostic applications based on bioimaging and photosensitizing capabilities has been evaluated. The main absorption and emission bands of the prepared CPNs both fell within the NIR-I (650-950 nm) transparency window, allowing facile and efficient implementation of our CPNs as bioimaging agents, as demonstrated in this work for A549 human lung cancer cell cultures. The prepared CPN samples were also shown to produce reactive oxygen species (ROS) upon photoexcitation in the near-infrared or ultraviolet spectral regions, both in aqueous solutions and in HaCaT keratinocyte cell cultures. Importantly, we show that the photosensitizing ability of our CPNs was largely determined by the nature of the stabilizing shell: coating the CPNs with a Pluronic F-127 copolymer led to an improvement of photoinitiated ROS production, while using poly[styrene-co-maleic anhydride] instead completely quenched said process. This work therefore demonstrates that the photosensitizing capability of CPNs can be modulated via an appropriate selection of stabilizing material and highlights the significance of this parameter for the on-demand design of theranostic probes based on CPNs.

Circulating tumor-cell-targeting Au-nanocage-mediated bimodal phototherapeutic properties enriched by magnetic nanocores

Metastasis resulting from circulating tumor cells (CTCs) is associated with 90% of all cancer mortality. To disrupt cancer dissemination, therapeutic targeting of CTCs by extracorporeal photodynamic therapy (PDT) has emerged; however, it still remains impractical due to its limited therapeutic window. Herein, we developed a photosensitive and magnetic targeted core-satellite nanomedicine (TCSN) to augment the light-induced damage to the targeted cells. The magnetic nanocore (MNC) with multiple iron oxide nanoparticles stabilized using thiolated polyvinyl alcohol can magnetize the CTCs to achieve magnetic enrichment under a magnetic field. Multiple gold nanocage (AuNC) satellites were conjugated on the MNC to facilitate bimodal photothermal therapy and PDT. Adjusting the thiol content in the MNC allows manipulating the AuNC density on TCSNs, which has been found to demonstrate a density-dependent bimodal phototherapeutic effect under laser irradiation at 808 and 940 nm. Moreover, with the immobilization of anti-epithelial cell adhesion molecule (anti-EpCAM), TCSN exhibited an enhanced affinity toward EpCAM-expressing 4T1 cells. We demonstrate that TCSN-labeled 4T1 cells can be isolated and photo-eradicated in a microfluidic channel with a dynamic flow. Our studies showed that TCSN with the complementary properties of MNC and AuNCs can largely augment the therapeutic window by magnetic enrichment and bimodal phototherapy, serving as an advanced extracorporeal strategy to remove CTCs.

Tailored Engineering of Novel Xanthonium Polymethine Dyes for Synergetic PDT and PTT Triggered by 1064 nm Laser toward Deep-Seated Tumors

Small molecular dye that simultaneously exerts dual PDT/PTT effects as well as florescence imaging triggered by a single NIR-II light has never been reported to date. Apart from the huge challenge in pushing absorption profile into NIR-II region, fine-tuning dyes' excited state via rational structure design to meet all three functions, especially oxygen photosensitization, remains the most prominent throttle. Herein, five novel NIR-II dyes (BHs) are productively developed by strategically conjugating dyad innovative xanthonium with sequentially extended polymethine bridges, enabling intense absorption from 890 to 1206 nm, significantly 400 nm longer than conventional cyanine dyes with same polymethines. More importantly, owning to high resonance and favorable excited state energy population induced by greater rigidity via ring-fused amino, BH 1024 exhibits best singlet oxygen generation capability, moderate photothermal heating, and considerable fluorescence under 1064 nm laser irradiation. Furthermore, BH 1024 is encapsulated into folate-functionalized polymer, which demonstrated a synergetic PDT/PTT effect in vitro and in vivo, eventually achieving solid tumors elimination under NIR-II fluorescence guide. As far as it is known, this is the first time small molecular dyes for NIR-II PDT or NIR-II PDT/PTT are explored and designed.

Singlet-Oxygen Generation by Peroxidases and Peroxygenases for Chemoenzymatic Synthesis

Singlet oxygen is a reactive oxygen species undesired in living cells but a rare and valuable reagent in chemical synthesis. We present a fluorescence spectroscopic analysis of the singlet-oxygen formation activity of commercial peroxidases and novel peroxygenases. Singlet-oxygen sensor green (SOSG) is used as fluorogenic singlet oxygen trap. Establishing a kinetic model for the reaction cascade to the fluorescent SOSG endoperoxide permits a kinetic analysis of enzymatic singlet-oxygen formation. All peroxidases and peroxygenases show singlet-oxygen formation. No singlet oxygen activity could be found for any catalase under investigation. Substrate inhibition is observed for all reactive enzymes. The commercial dye-decolorizing peroxidase industrially used for dairy bleaching shows the highest singlet-oxygen activity and the lowest inhibition. This enzyme was immobilized on a textile carrier and successfully applied for a chemical synthesis. Here, ascaridole was synthesized via enzymatically produced singlet oxygen.

A chlorin-lipid nanovesicle nucleus drug for amplified therapeutic effects of lung cancer by internal radiotherapy combined with the Cerenkov radiation-induced photodynamic therapy

Traditional photodynamic therapy (PDT) requires external light excitation to produce reactive oxygen species (ROSs) for the treatment of tumors. Due to problems of light penetration, traditional PDT is limited by the location and depth of the tumor. In this study, we rationally designed and constructed a novel strategy to amplify the therapeutic effect of PDT. We prepared a chlorin-lipid nanovesicle based on the conjugates of chlorin e6 (Ce 6) and phospholipids, with the surface conjugating the aptamer for lung cancer targeting, GLT21.T. ¹³¹I-labeled bovine serum albumin (¹³¹I-BSA) was loaded into the chlorin-lipid nanovesicle cavity (¹³¹I-BSA@LCN-Apt). ¹³¹I not only plays a role in radiotherapy, but its Cerenkov radiation (CR), as an internal light source, can also stimulate Ce6 to produce ROSs without external light excitation. The in vitro and in vivo therapeutic effects in subcutaneous lung tumor models and orthotopic lung tumor models indicated that ¹³¹I-BSA@LCN-Apt produced a powerful anti-tumor effect through synergistic radiotherapy and CR-PDT, which almost caused complete tumor growth regression. After treatment, the survival time of the mice was significantly prolonged. During the treatment, no obvious side effects were found by histopathology of important organs, hematology and biochemistry analysis except the decrease of the white blood cell count (WBC). The study provides a major tool for deep-seated tumors to obtain amplified therapeutic effects by synergistic radiotherapy and CR-PDT without the use of any external light source.

An effective inactivant based on singlet oxygen-mediated lipid oxidation implicates a new paradigm for broad-spectrum antivirals

Emerging viral pathogens cause substantial morbidity and pose a severe threat to health worldwide. However, a universal antiviral strategy for producing safe and immunogenic inactivated vaccines is lacking. Here, we report an antiviral strategy using the novel singlet oxygen (¹O₂)-generating agent LJ002 to inactivate enveloped viruses and provide effective protection against viral infection. Our results demonstrated that LJ002 efficiently generated ¹O₂ in solution and living cells. Nevertheless, LJ002 exhibited no signs of acute toxicity in vitro or in vivo. The ¹O₂ produced by LJ002 oxidized lipids in the viral envelope and consequently destroyed the viral membrane structure, thus inhibiting the viral and cell membrane fusion necessary for infection. Moreover, the ¹O₂-based inactivated pseudorabies virus (PRV) vaccine had no effect on the content of the viral surface proteins. Immunization of mice with LJ002-inactiviated PRV vaccine harboring comparable antigen induced more neutralizing antibody responses and efficient protection against PRV infection than conventional formalin-inactivated vaccine. Additionally, LJ002 inactivated a broad spectrum of enveloped viruses. Together, our results may provide a new paradigm of using broad-spectrum, highly effective inactivants functioning through ¹O₂-mediated lipid oxidation for developing antivirals that target the viral membrane fusion process.

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LJ002 efficiently generates ¹O₂ in solution and living cells.

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LJ002 oxidizes lipids in the viral envelope, thus inhibiting fusion between the virus and cell membrane.

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LJ002-inactivated PRV vaccine has no effect on the content of antigens on the viral surface.

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LJ002-inactivated PRV vaccine elicits a strong neutralizing antibody response.

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LJ002 can inactivate a broad spectrum of enveloped viruses.

Hydrogen Peroxide-Activatable Nanoparticles for Luminescence Imaging and In Situ Triggerable Photodynamic Therapy of Cancer

Abnormally increased reactive oxygen species (ROS) are intimately related to the development and metastasis of cancer. Since hydrogen peroxide (H₂O₂) is a major component of ROS, molecular imaging and selective treatment in response to high H₂O₂ are intriguing for the management of cancers. Herein, we report novel self-assembly luminescent nanoparticles, which can be activated by H₂O₂, thereby serving as an effective nanotheranostics for luminescence imaging and in situ photodynamic therapy (PDT) of tumors with high H₂O₂. This functional nanomedicine was assembled from an amphiphilic conjugate (defined as CLP) based on chlorin e6 (Ce6) simultaneously conjugated with luminol and poly(ethylene glycol), exhibiting a well-defined core-shell nanostructure. Upon triggering by pathologically relevant levels of H₂O₂, CLP nanoparticles produced luminescence due to the luminol unit and simultaneous excitation of Ce6 by chemiluminescence resonance energy transfer, enabling in vitro and in vivo imaging of tumors with highly expressed H₂O₂. In addition, excited Ce6 can produce singlet oxygen (¹O₂) for in situ PDT of H₂O₂-high tumors and inhibiting lung metastasis, which was demonstrated by in vitro and in vivo experiments. Furthermore, preliminary studies revealed the biosafety of CLP nanoparticles. Consequently, the self-illuminating nanoparticles are promising for noninvasive imaging and therapy of tumors with high expression of H₂O₂.

Enhancing multiphoton upconversion through interfacial energy transfer in multilayered nanoparticles

Photon upconversion in lanthanide-doped upconversion nanoparticles offers a wide variety of applications including deep-tissue biophotonics. However, the upconversion luminescence and efficiency, especially involving multiple photons, is still limited by the concentration quenching effect. Here, we demonstrate a multilayered core-shell-shell structure for lanthanide doped NaYF₄, where Er³⁺ activators and Yb³⁺ sensitizers are spatially separated, which can enhance the multiphoton emission from Er³⁺ by 100-fold compared with the multiphoton emission from canonical core-shell nanocrystals. This difference is due to the excitation energy transfer at the interface between activator core and sensitizer shell being unexpectedly efficient, as revealed by the structural and temperature dependence of the multiphoton upconversion luminescence. Therefore, the concentration quenching is suppressed via alleviation of cross-relaxation between the activator and the sensitizer, resulting in a high quantum yield of up to 6.34% for this layered structure. These findings will enable versatile design of multiphoton upconverting nanoparticles overcoming the conventional limitation.

Protein-stabilized gold nanoclusters for PDT: ROS and singlet oxygen generation

Suitable properties as well as eco-friendly synthesis of photoluminescent Au nanoclusters (NCs) make them promising compounds for biomedical diagnostics and visualization applications. However, the potential photochemical activity of such agents on cancerous cells is largely unknown. The nanoclusters (BSA-Au NCs) were synthetized in the presence of BSA (an average hydrodynamic diameter was about 9.4 nm, while the size of the metal cluster was <1.3 nm according to atomic force microscopy measurements) and possessed a broad photoluminescence band at 680 nm in buffered (pH 7.2) aqueous medium. The photochemical activity was studied by adding two fluorescent probes (dihydrorhodamine or Singlet Oxygen Sensor Green) for detection of reactive oxygen species in samples irradiated at 405 nm to minimize direct excitation of the probes. The photoluminescence measurements evidenced the capability of BSA-Au NCs to generate reactive oxygen species upon light exposure, while the observed sensitivity of the photoluminescence properties might be used to indicate photooxidative processes in the medium. The viability test performed on breast cancer cells after incubation with BSA-Au NCs and subsequent irradiation revealed notable difference in induced phototoxicity between two cell lines, which was not the case after the corresponding treatment using the photosensitizer chlorin e₆.

A Versatile Theranostic Nanoemulsion for Architecture-Dependent Multimodal Imaging and Dually Augmented Photodynamic Therapy

To design a clinically translatable nanomedicine for photodynamic theranostics, the ingredients should be carefully considered. A high content of nanocarriers may cause extra toxicity in metabolism, and multiple theranostic agents would complicate the preparation process. These issues would be of less concern if the nanocarrier itself has most of the theranostic functions. In this work, a poly(ethylene glycol)-boron dipyrromethene amphiphile (PEG-F₅₄ -BODIPY) with 54 fluorine-19 (¹⁹ F) is synthesized and employed to emulsify perfluorohexane (PFH) into a theranostic nanoemulsion (PFH@PEG-F₅₄ -BODIPY). The as-prepared PFH@PEG-F₅₄ -BODIPY can perform architecture-dependent fluorescence/photoacoustic/¹⁹ F magnetic resonance multimodal imaging, providing more information about the in vivo structure evolution of nanomedicine. Importantly, this nanoemulsion significantly enhances the therapeutic effect of BODIPY through both the high oxygen dissolving capability and less self-quenching of BODIPY molecules. More interestingly, PFH@PEG-F₅₄ -BODIPY shows high level of tumor accumulation and long tumor retention time, allowing a repeated light irradiation after a single-dose intravenous injection. The "all-in-one" photodynamic theranostic nanoemulsion has simple composition, remarkable theranostic efficacy, and novel treatment pattern, and thus presents an intriguing avenue to developing clinically translatable theranostic agents.

Injectable Peptide Hydrogel Enables Integrated Tandem Enzymes' Superactivity for Cancer Therapy

Elevation of the levels of reactive oxygen species and other toxic radicals is an emerging strategy to treat certain cancers by modulating the redox status of cancer cells. The biocatalytic upregulation of singlet oxygen by neutrophilic leukocytes should utilize robust enzymes and design carriers with protective microenvironment. Here, we utilize GOx-CPO as integrated tandem enzymes to in situ generate singlet oxygen, which could be not only for oxidative cross-linking of injectable hydrogel carriers but also for continuous tumor treatment by adjustable bioconversion of blood oxygen, glucose, and chloride ion. The tandem enzymes self-restrained within peptide hydrogel exhibited superactivity for upregulating singlet oxygen relative to free enzymes, which also avoids the diffusion of enzymes from tumor. This work will not only deepen the study of enzymes in biocatalysis but also offer an enzyme therapeutic modality for treating cancers.

Perfluorocarbon-based O2 nanocarrier for efficient photodynamic therapy

Tumor hypoxia is considered as one of the major factors that limit the efficiency of photodynamic therapy (PDT), in which oxygen (O₂) is needed to generate singlet oxygen (¹O₂) for cell destruction. Inspired by the excellent O₂ carrying ability of perfluorocarbon molecules in artificial blood, we prepared a series of polymer micelles with a perfluorocarbon core to carry both photo-sensitizer and O₂ to the tumor site, aiming to improve PDT efficiency. We found that the accelerated generation of ¹O₂ correlated with the increased perfluorocarbon amount in solution. In vitro cell study further showed that the new perfluorocarbon formulation not only improved the production of ¹O₂, leading to enhanced photodynamic therapy efficiency, but also significantly reduced cell toxicity when compared with the one without these perfluoro units. This work provides a new option for improving PDT efficiency with the new perfluorocarbon-incorporated nanoplatform.

Differential photothermal and photodynamic performance behaviors of gold nanorods, nanoshells and nanocages under identical energy conditions

The corner angle structure of Au nanostructures could more efficiently convert the photon energy into the photodynamic performance.

A photodynamic antibacterial spray-coating based on the host–guest immobilization of the photosensitizer methylene blue

An efficient photodynamic antibacterial spray-coating is developed with a very low MB density and high singlet oxygen quantum yield.

A fluorescent nanoprobe for real-time monitoring of intracellular singlet oxygen during photodynamic therapy

Sensing of intracellular singlet oxygen (¹O₂) is required in order to optimize photodynamic therapy (PDT). An optical nanoprobe is reported here for the optical determination of intracellular ¹O₂. The probe consists of a porous particle core doped with the commercial ¹O₂ probe 1,3-diphenylisobenzofuran (DPBF) and a layer of poly-L-lysine. The nanoparticle probes have a particle size of ~80 nm in diameter, exhibit good biocompatibility, improved photostability and high sensitivity for ¹O₂ in both absorbance (peak at 420 nm) and fluorescence (with excitation/emission peaks at 405/458 nm). Nanoprobes doped with 20% of DPBF are best suited even though they suffer from concentration quenching of fluorescence. In comparison with the commercial fluorescent ¹O₂ probe SOSG, 20%-doped DPBF-NPs (aged) shows higher sensitivity for ¹O₂ generated at an early stage. The best nanoprobes were used to real-time monitor the PDT-triggered generation of ¹O₂ inside live cells, and the generation rate is found to depend on the supply of intracellular oxygen. Graphical abstract A fluorescent nanoprobe featured with refined selectivity and improved sensitivity towards ¹O₂ was prepared from the absorption-based probe DBPF and used to real-time monitoring of the generation of intracellular ¹O₂ produced during PDT.

Tuning photochemical properties of phosphorus(v) porphyrin photosensitizers

Photosensitizing and emission properties of P(v) porphyrins were studied. The nature of the axial ligands, occupying the apical position on the P centre adopting an octahedral coordination geometry, strongly influences singlet oxygen generation and charge transfer and allows switching between the two processes.

Oxygenic Hybrid Semiconducting Nanoparticles for Enhanced Photodynamic Therapy

Photodynamic nanotheranostics has shown great promise for cancer therapy; however, its therapeutic efficacy is limited due to the hypoxia of tumor microenvironment and the unfavorable bioavailability of existing photodynamic agents. We herein develop hybrid core-shell semiconducting nanoparticles (SPN-Ms) that can undergo O₂ evolution in hypoxic solid tumor to promote photodynamic process. Such oxygenic nanoparticles are synthesized through a one-pot surface growth reaction and have a unique multilayer structure cored and coated with semiconducting polymer nanoparticles (SPNs) and manganese dioxide (MnO₂) nanosheets, respectively. The SPN core serves as both NIR fluorescence imaging and photodynamic agent, while the MnO₂ nanosheets act as a sacrificing component to convert H₂O₂ to O₂ under hypoxic and acidic tumor microenvironment. As compared with the uncoated SPN (SPN-0), the oxygenic nanoparticles (SPN-M1) generate 2.68-fold more ¹O₂ at hypoxic and acidic conditions under NIR laser irradiation at 808 nm. Because of such an oxygen-evolution property, SPN-M1 can effectively eradicate cancer cells both in vitro and in vivo. Our study thus not only reports an in situ synthetic method to coat organic nanoparticles but also develops a tumor-microenvironment-sensitive theranostic nanoagent to overcome hypoxia for amplified therapy.

Pullulan-coated phospholipid and Pluronic F68 complex nanoparticles for carrying IR780 and paclitaxel to treat hepatocellular carcinoma by combining photothermal therapy/photodynamic therapy and chemotherapy

IR780, a near-infrared dye, can also be used as a photosensitizer both for photothermal therapy (PTT) and photodynamic therapy (PDT). In this study, we designed a simple but effective nanoparticle system for carrying IR780 and paclitaxel, thus hoping to combine PTT/PDT and chemotherapy to treat hepatocellular carcinoma (HCC). This nanosystem, named PDF nanoparticles, consisted of phospholipid/Pluronic F68 complex nanocores and pullulan shells. IR780 and paclitaxel were loaded separately into PDF nanoparticles to form PDFI and PDFP nanoparticles, which had regular sphere shapes and relatively small sizes. Upon near-infrared laser irradiation at 808 nm, PDFI nanoparticles showed strong PTT/PDT efficacy both in vitro and in vivo. In MHCC-97H cells, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles exhibited significant synergistic effects on inhibiting cell proliferation and inducing cell apoptosis and cell cycle arrest at G2/M phase. In MHCC-97H tumor-bearing mice, PDFI nanoparticles exhibited excellent HCC-targeting and accumulating capability after intravenous injection. Furthermore, the combined treatment of PDFI nanoparticles/laser irradiation and PDFP nanoparticles also effectively inhibited the tumor growth and the tumor angiogenesis in MHCC-97H tumor-bearing mice. In summary, we put forward a therapeutic strategy for HCC treatment by combining PTT/PDT and chemotherapy.

Biophotonics in China

Biophotonics is a highly interdisciplinary field where physicists, chemists, biologists, physicians and engineers work together to solve the problems appearing in biology and medicine. In China, the Biophotonics discipline is often referred to as Biomedical Photonics, under the first-level disciplines Biomedical Engineering or Optical Engineering, and was initiated in the late 1990s. Over the past 20 years, biophotonics research in China expanded extraordinarily and has reached the frontiers of the world-level sciences. This white paper introduces the research groups in the biophotonics field in China, and their representative contributions.