Singlet Oxygen Yield Research Articles

Preparation and photodynamic antibacterial/anticancer effects of ultralong-lifetime room-temperature phosphorescent N-doped carbon dots.

Room-temperature phosphorescent (RTP) N-doped carbon-dots (CNDs) featuring eco-friendliness, low cost and high biocompatibility, are ideal photodynamic antibacterial and anticancer nanomaterials. However, the existing CNDs are limited by low singlet oxygen (1O2) quantum yield, which has become a bottleneck in the development of CNDs. One basic reason is the short T1-state exciton lifetime of CNDs. Herein, triethylenetetramine hexaacetic acid was used to synthesize CNDs via a one-step hydrothermal method. CNDs are characterized with low toxicity, high biocompatibility and ultralong-lifetime RTP (URTP). In addition to the URTP (average lifetime 414 ms) under solid conditions, CNDs even had URTP (average lifetime 320 ms) in a water environment. The ultralong T1 exciton lifetime largely extends the collision time between T1 state excitons and O2 and prolongs the energy transfer time, not only improving the quantum yield (0.63) of singlet oxygen (1O2) in solution, but also facilitating the photodynamic antibacterial and anticancer effects.

Pegylated metal-free and zinc(II) phthalocyanines: synthesis, photophysicochemical properties and in vitro photodynamic activities against head, neck and colon cancer cell lines.

In this study, a series of peripherally and non-peripherally tetra-substituted metal-free and zinc(II) phthalocyanines were successfully prepared in good yields by cyclotetramerization of the phthalonitrile derivative bearing a tetraethylene glycol methyl ether group at 3- and 4- positions. All newly synthesized compounds were characterized using spectroscopic methods, such as FT-IR, NMR, mass and UV-Vis spectroscopy. To determine the therapeutic potential of the synthesized phthalocyanines, the effects of the substitution pattern (peripheral and non-peripheral) and central metal atom on the photophysicochemical properties were investigated. When comparing their singlet oxygen generation capabilities (ΦΔ), metallo-phthalocyanine derivatives with zinc (0.73 for 1b and 0.70 for 2b) showed higher singlet oxygen yield than metal-free derivatives (0.21 for 1a and 0.12 for 2a) in DMSO. The photodynamic therapy activities of the water-soluble phthalocyanines were tested via in vitro studies using the A253, FaDu (head and neck cancer cell lines), and HT29 (colon cancer) cell lines. The strongest photodynamic activity was found in 1b and 2b molecules with a metal core among the four molecules studied. The results suggested that the non-peripherally tetra-substituted 1b molecule was regarded as a suitable photodynamic therapy agent due to its light cytotoxicity and secondary impact induced by ROS production.

Single-molecule photosensitizers for NIR-II fluorescence and photoacoustic imaging guided precise anticancer phototherapy.

It is ideal yet challenging to achieve precise tumor targeting and high-quality imaging guided combined photodynamic and photothermal therapy (PDT and PTT). In this study, we synthesized a series of D–π–A-type single-molecule photosensitizers (CyE-TT, CyQN-TT, and CyQN-BTT) based on quaternized 1,1,2-trimethyl-1H-benz[e]indoles as acceptors by introducing π-bridges to elongate their emission wavelength and triphenylamine as a donor to construct a twisted molecular conformation. We found that the 1O2 generation ability and the photothermal conversion efficiency (PCE) are directly correlated with the π-bridge between donors and acceptors in these molecules. When a 2,1,3-benzothiadiazole group as a π-bridge was introduced into CyQN-BTT, the singlet oxygen yield enhanced to 27.1%, PCE to 37.8%, and the emission wavelength was red-shifted to near-infrared II (NIR-II). Importantly, double-cationic CyQN-BTT displays structure-inherent cancer cell targeting ability instead of targeting normal cells. Consequently, relying on NIR-II fluorescence imaging (NIR-II FLI) and photoacoustic imaging (PAI) guided PDT and PTT, CyQN-BTT can accurately locate solid tumors in mice and effectively eliminate them with good biocompatibility and biosafety to normal tissues. This study provides insights into the design and development of a tumor-specific targeting multifunctional photosensitizer for precise cancer phototherapy.

Dual-mode antibacterial core-shell gold nanorod@mesoporous-silica/curcumin nanocomplexes for efficient photothermal and photodynamic therapy

Bacteria are becoming increasingly resistant to antibiotics because of their overuse. As a result, new therapies are urgently needed to replace traditional antibiotic therapies. Photodynamic therapy and photothermal therapy are considered to be effective sterilization methods instead of antibiotics to resist drug-resistant pathogens. In this work, silica-coated gold nanorods with photothermal conversion effects were employed as photothermal carriers, and curcumin was selected as photosensitizer, to form PTT/PDT dual-mode antibacterial nanocomposites (AuNRs@Cur). Comparing with their counterparts Cur and AuNRs, AuNRs@Cur exhibited higher singlet oxygen yield and photothermal conversion efficiency, which greatly improved the utilization rate of photosensitizer and consequently effectively enhanced the photoinactivation effect of bacteria. The inhibition rate of AuNRs@Cur on S. aureus and E. coli under 405 and 808 nm dual irradiation was higher than that of Cur or PDT alone. The changes of bacterial membrane structure were revealed by scanning electron microscopy (SEM) and confocal fluorescence imaging. The reactive oxygen species and thermal energy generated by dual-wavelength (405 + 808 nm) laser irradiation can cause the destruction of bacterial outer membrane structure, resulting in bacterial death. In addition, the cytotoxicity and hemolytic activity of AuNRs@Cur were negligible. AuNRs@Cur nanocomposites proved thatphotodynamic-photothermal synergistic treatment can greatly improve the bactericidal effect. Therefore, construction of AuNRs@Cur provides a new idea for pathogen infection caused by drug-resistant bacteria, and provides relevant nano-carrier experience for follow-up drugs.

Low Blue Dose Photodynamic Therapy with Porphyrin-Iron Oxide Nanoparticles Complexes: In Vitro Study on Human Melanoma Cells.

The purpose of this study was to investigate the effectiveness in photodynamic therapy of iron oxide nanoparticles (γ-Fe2O3 NPs), synthesized by laser pyrolysis technique, functionalized with 5,10,15,20-(Tetra-4-sulfonatophenyl) porphyrin tetraammonium (TPPS) on human cutaneous melanoma cells, after only 1 min blue light exposure. The efficiency of porphyrin loading on the iron oxide nanocarriers was estimated by using absorption and FTIR spectroscopy. The singlet oxygen yield was determined via transient characteristics of singlet oxygen phosphorescence at 1270 nm both for porphyrin functionalized nanoparticles and rose bengal used as standard. The irradiation was performed with a LED (405 nm, 1 mW/cm2) for 1 min after melanoma cells were treated with TPPS functionalized iron oxide nanoparticles (γ-Fe2O3 NPs_TPPS) and incubated for 24 h. Biological tests revealed a high anticancer effect of γ-Fe2O3 NPs_TPPS complexes indi-cated by the inhibition of tumor cell proliferation, reduction of cell adhesion, and induction of cell death through ROS generated by TPPS under light exposure. The biological assays were combined with the pharmacokinetic prediction of the porphyrin.

Two effective strategies to improve SOCT-ISC type photosensitizers: Triphenylamine BODIPY with A-D-A configuration and AIE effect and its application in A-549 cells and zebrafish

In this paper, a spin−orbit charge-transfer intersystem crossing (SOCT-ISC) type PY-BDP photosensitizer was reported. This PY-BDP photosensitizer's triplet state property was promoted through its aggregation-induced emission (AIE) characteristic and A-D-A configuration. The singlet oxygen yield of PY-BDP was insignificant in high polar organic solvent, while it increased to 31.5% in 90% water content DMSO solvent, which suggested the AIE effect could promote the generation of singlet oxygen. Besides that, compared with TPA-BDP (D-A configuration), the singlet oxygen yield of PY-BDP was increased 54.4%, which indicated the A-D-A configuration is more beneficial than D-A configuration in the production of singlet oxygen. In addition, the above two promotion mechanisms also was studied through the transient absorption spectroscopy and theoretical calculations. In the biological application aspect, the dark and photo toxicity experiments and the simulated photodynamic therapy indicate that PY-BDP had a low dark toxicity and high photo toxicity for A-549 cells and the IC50 of PY-BDP was 21.6 μM for 8 min irradiation. Beside that, the fluorescence imaging of zebrafish shown that the PY-BDP also could exhibited green and red dual-channel imaging. These application indicated the PY-BDP have a great chance to be applied in organism for further research.

Bovine Serum Albumin-Encapsulated Ultrasmall Gold Nanoclusters for Photodynamic Therapy of Tumors

Gold nanoclusters (AuNCs) with an ultrasmall size showed potential application in photodynamic therapy (PDT), but short circulation and weak tumor retention restricted their PDT performance. Herein, bovine serum albumin (BSA) nanospheres with good biocompatibility were used to encapsulate AuNCs, by which the stable and biocompatible AuNCs@BSA nanoprobes were synthesized to boost PDT performance. The results showed that ultrasmall AuNCs with a size of 1.5 nm were encapsulated in BSA nanospheres, and the prepared AuNCs@BSA nanoparticles with an average size of 120 nm have high colloid stability and enhanced fluorescence emission. Compared with single AuNCs, AuNCs@BSA possessed higher singlet oxygen yield, which increased from 34.5% to 45.5%. Moreover, AuNCs@BSA showed lower cytotoxicity and stronger cellular uptake, by which the cell viability was reduced to 20.6% and 4T1 tumor completely disappeared, compared with 47.5% cell viability and tumor recurrence of single AuNCs. The results demonstrated that the prepared AuNCs@BSA nanoprobes possessed good biocompatibility and boosted PDT performance and will be potential highly efficient PDT nanoprobes owing to their safety and reliability.

Recent progress of conjugated polymers in biosensing and biomedical applications

<p indent="0mm">Conjugated polymers (CPs) with delocalized π–π conjugated backbones have shown broad applications in biomedical fields. Compared with traditional fluorescent small molecules, conjugated polymers have attracted extensive attention due to large optical absorption coefficients, high singlet-oxygen yields and good biocompatibility. Based on the structure design and performance control of conjugated polymers, this article mainly introduces our research progress in the design and synthesis of conjugated polymers and their applications in biosensing, pathogen killing and tumor treatment in the past ten years. It also discusses the main opportunities and challenges in the future.

Meso-substituted cationic 3- and 4-N-Pyridylporphyrins and their Zn(II) derivatives for antibacterial photodynamic therapy

Photodynamic inactivation of microorganisms known as antibacterial photodynamic therapy (APDT) is one of the most promising and innovative approaches for the destruction of pathogenic microorganisms. Among the photosensitizers (PSs), compounds based on cationic porphyrins/metalloporphyrins are most successfully used to inactivate microorganisms. Series of meso-substituted cationic pyridylporphyrins and metalloporphyrins with various peripheral groups in the third and fourth positions of the pyrrole ring have been synthesized in Armenia. The aim of this work was to determine and test the most effective cationic porphyrins and metalloporphyrins with high photoactivity against Gram negative and Gram positive microorganisms. It was shown that the synthesized cationic pyridylporphyrins/metalloporphyrins exhibit a high degree of phototoxicity towards both types of bacteria, including the methicillin-resistant S. aureus strain. Zinc complexes of porphyrins are more phototoxic than metal-free porphyrin analogs. The effectiveness of these Zn–metalloporphyrins on bacteria is consistent with the level of singlet oxygen generation. It was found that the high antibacterial activity of the studied cationic porphyrins/metalloporphyrins depends on four factors: the presence in the porphyrin macrocycle of a positive charge (+4), a central metal atom (Zn[Formula: see text] and hydrophobic peripheral functional groups as well as high values of quantum yields of singlet oxygen. The results indicate that meso-substituted cationic pyridylporphyrins/metalloporphyrins can find wider application in photoinactivation of bacteria than anionic or neutral PSs usually used in APDT.

A two-photon fluorescence probe with endoplasmic reticulum targeting ability for turn-on sensing photosensitized singlet oxygen in living cells and brain tissues

Endoplasmic reticulum (ER) is an indispensable organelle responsible for protein synthesis, transportation, and maintenance of Ca2+ homeostasis in eukaryotic cells. Recent studies highlighted that ER-targeted photosensitizers with high yield of singlet oxygen (1O2) are effective in selectively disrupting ER function and are promising candidates for anticancer therapy. Unfortunately, no ER targetable fluorescent probes for determining 1O2 photosensitized in this photodynamic therapy process is available. In this work, we synthesized an ER-targetable, two-photon fluorescence probe, ER-1O2, for fluorescence turn-on sensing of 1O2. ER-1O2 demonstrated high sensitivity to 1O2 sensing with a wide detection range (0–2.75 μM) and a low detection limit (0.11 μM). ER-1O2 also displayed excellent selectivity toward 1O2 out of other ROS and metal ions. Notably, ER-1O2 exhibited low cytotoxicity but with specific ER targetable capability. On account of these advantageous features, fluctuations of 1O2 in living cells and brain tissues were effectively visualized by ER-1O2.

Preparation of a porphyrin-polyoxometalate hybrid and its photocatalytic degradation performance for mustard gas simulant 2-chloroethyl ethyl sulfide

By combining 5,10,15,20-tetra(4-chlorine)phenylporphyrin (TClPP) and α-Keggin polyoxometalate H5PV2Mo10O40 (H5PVMo) via a simple ion-exchange method, an organic-inorganic hybrid material [C44H28N4Cl4]1.5[H2PMo10V2O40]·2C2H6O (H2TClPP-H2PVMo) was prepared and thoroughly characterized by a variety of techniques. The homogeneous photocatalytic degradation of 2-chloroethyl ethyl sulfide (CEES) (5 µL) by H2TClPP-H2PVMo (1 × 10−6 mol/L) was studied in methanol and methanol-water mixed solvent (v/v = 1:1), in which the degradation rate of CEES reached 99.52% and 99.14%, respectively. The reaction followed first-order reaction kinetics, and the half-life and kinetic constant in methanol and the mixed solvent were respectively 33.0 min, −0.021 min−1 and 15.7 min, −0.043 min−1. Mechanism analysis indicated that under visible light irradiation in the air, CEES was degraded via oxidation and alcoholysis/hydrolysis in methanol and the mixed solvent. O2·− and 1O2 generated by H2TClPP-H2PVMo selectively oxidized CEES into a nontoxic sulfoxide. Singlet oxygen capture experiments showed that H2TClPP-H2PVMo (ϕ = 0.73) had a higher quantum yield of singlet oxygen than TClPP (ϕ = 0.35) under an air atmosphere and visible light irradiation.

A diketopyrrolopyrrole-based conjugated polymer for efficient photodynamic and photothermal combination therapy under single 808 nm laser irradiation

Photodynamic therapy (PDT) and photothermal therapy (PTT) are two powerful tools to tackle cancer in the biomedical field due to their super tumor ablation efficiency and minimal damage to normal tissue. However, it is still a tricky challenge to combine these two treatment modalities into a single agent for single wavelength laser triggered efficient tumor therapy. Herein, water-soluble nanoparticles consisting of diketopyrrolopyrrole-based conjugated polymer and amphipathic Pluronic F127 were intelligently devised and fabricated, which possessed outstanding optical properties, superb biocompatibility, excellent photostability. Surprisingly, the nanoparticles exhibited moderate singlet oxygen yield (2.34%) and photothermal conversion efficiency (41.5%) under an 808 nm laser illumination, which was in favor of achieving high-performance PDT/PTT combination therapy. Moreover, the evident antitumor effect of the nanoparticles was confirmed by in vitro and in vivo experiments. This work provides a promising approach to rationally design near infrared absorbing organic polymer nanoplatforms for combination cancer therapy.

Rational Design of Near‐Infrared Aza‐Platinum‐Dipyrromethene‐Based Nanophototherapy Agent with Multistage Enhancement for Synergistic Antitumor Therapeutics

The development of innovative synergistic phototherapy (SPT) agent with excellent photodynamic therapy (PDT) and photothermal therapy (PTT) effects for efficient antitumor is of great significance. However, the low photothermal conversion efficiency or low singlet oxygen yield of SPT agent during the phototherapy process will result in inefficient tumor therapy. Herein, a new near‐infrared (NIR) SPT agent based on aza‐platinum‐dipyrromethene dye (D‐3) with synergistic PDT and PTT effects is rationally designed and synthesized by the metallization and halogenation of aza‐dipyrromethene simultaneously. The introduction of iodine atoms and Pt(II) ion to aza‐dipyrromethene skeleton can not only effectively promote the excited electrons to undergo intersystem crossing process for improving singlet oxygen (1O2) generation capability, but also inhibit radiative transition process for boosting photothermal conversion properties. For biological exploration, the biocompatible D‐3 nanomaterials (APIDNs) with excellent concentration‐dependent photoacoustic and photothermal properties are prepared, thus visibly guiding synergetic PDT and PTT effects for inhibiting the growth of tumor cells in vivo. This work demonstrates the superior therapy effects of APIDNs and its negligible dark cytotoxicity. The novel strategy reported in this work will offer a new way to design new‐generation NIR aza‐metal‐dipyrromethene‐based dyes for developing superior SPT agents.

A SOCT-ISC type photosensitizer coumarin-BODIPY promoted by AIE effect: Mechanism of singlet oxygen generation, simulated PDT in A-549 cells and fluorescence imaging in zebrafish

A spin−orbit charge-transfer intersystem crossing (SOCT-ISC) type photosensitizer coumarin-BODIPY (CM-BDP) was reported in this paper. Due its aggregation induced emission (AIE) effect, CM-BDP could work under high water content condition. Besides that, another important phenomenon was discovered. In DMSO solvent, the fluorescence emission and the singlet oxygen yield of CM-BDP were almost negligible, while, in 90% water content system, the singlet oxygen yield of CM-BDP was up to 20.9% and a strong TICT fluorescence emission at 648 nm was observed, which indicated the AIE effect could also promote the generation of singlet oxygen by preserving the energy. In terms of the mechanism of generating singlet oxygen, the D-A configuration of CM-BDP could facilitate the process of charge separation, as well as the generation of TICT state. Then, the orthogonal configuration of CM-BDP in TICT state and the small △Est between the TICT state and T2 state could promote the SOCT-ISC process effectively. Combining the femtosecond transient absorption spectra and the DFT theoretical calculations, the photophysical process of CM-BDP was proposed in simplified Jablonski diagram. Moreover, the CM-BDP was also applied to intracellular experiment and zebrafish imaging. In the photo/dark toxicity experiment, cell survival rate of dark toxicity experiment was basically higher than 90%, while its decreased significantly under irradiation. The result of acridine orange/ethidium bromide (AO/EB) stain experiment indicated that the CM-BDP could kill A-549 cancer cells effectively under irradiation and the fluorescence imaging in zebrafish proved that CM-BDP could be further applied in organisms.

TB@PLGA Nanoparticles for Photodynamic/Photothermal Combined Cancer Therapy with Single Near-Infrared Irradiation.

BackgroundPhototherapy has significant potential as an effective treatment for cancer. However, the application of a multifunctional nanoplatform for photodynamic therapy (PDT) and photothermal therapy (PTT) at a single excitation wavelength remains a challenge.Materials and MethodsThe double emulsion solvent evaporation method was used to prepare toluidine blue@poly lactic-co-glycolic acid (TB@PLGA) nanoparticles (NPs). The biocompatibility of TB@PLGA NPs was evaluated, and a 660 nm luminescence was used as the light source. The photothermal effect, photothermal stability, and singlet oxygen yield of NPs in an aqueous solution verified the feasibility of NPs as a PTT/PDT synergistic therapy drug.ResultsTB@PLGA NPs were successfully prepared and characterized. In vitro experiments demonstrated that TB@PLGA NPs can cause massive necrosis of tumor cells and induce apoptosis through a photodynamic mechanism under 660 nm laser irradiation. The TB@PLGA NPs also achieved optimal tumor inhibition effect in vivo.ConclusionThe TB@PLGA NPs prepared in this study were applied as a dual-mode phototherapeutic agent under single laser irradiation. Both in vitro and in vivo experiments demonstrated the good potential of PTT/PDT for tumor inhibitors.

Improved singlet oxygen yields of new palladium phthalocyanines using sonochemistry and comparisons with photochemistry

Sono-photodynamic therapy (SPDT) is a new approach for the determination of singlet oxygen quantum yields in non-invasively solid tumor studies. In SPDT application, effective tissue penetration is much more than that occurring in conventional photodynamic therapy (PDT) application. On the other hand, due to the synthetic difficulty of palladium phthalocyanines, there are few numbers of literature studying the unique properties of palladium phthalocyanines. For these reasons, this study presents the synthesis of three new non-peripherally substituted palladium(II) phthalocyanine complexes (PdPc1, PdPc2 and PdPc3). All the resulting compounds were characterized using FT-IR, 1H-NMR and mass spectroscopic methods. Also, this study comparatively focuses on both photochemical and sono-photochemical methods to examine the photophysicochemical properties of the newly synthesized palladium phthalocyanine complexes (PdPcs) for the first time. For the stated PdPcs, lower singlet oxygen yields were obtained by applying the photochemical method compared to those obtained by performing the sono-photochemical method. In the photochemical study, the respective singlet oxygen values (ΦΔ) of the phthalocyanine complexes (PdPc1-3) were obtained 0.45, 0.51 and 0.70 while in the sono-photochemical study, the singlet oxygen values (ΦΔ) were obtained 0.71, 0.75 and 0.82, respectively. These results indicated that the sono-photochemical method is a more promising approach than the photochemical one.

Singlet and Triplet State Properties and Singlet Oxygen Yield of an Amino-Acyl-Quinoxalinone Yellow Dye.

Amino-acyl-quinoxalinone yellow dyes are cyclised analogues of the yellow azomethine dyes developed for, and still used in, silver halide colour photography. Unlike image azomethine dyes, which are rapidly deactivated in their excited states by torsion about the azomethine bond, amino-acyl-quinoxalinone dyes have an interesting photophysics because torsion is not possible due to their cyclised structure. We report results from studies on singlet and triplet state properties, and singlet oxygen yields, of the yellow dye, 7-diethylamino-3-(2,2-dimethyl-propionyl)-5-methyl-1-phenyl-1H-quinoxalin-2-one, in polar and nonpolar solvents. The dye photophysics is characterised by a weak fluorescence, with a solvent dependent emission yield (ΦF ≈ 0.002-0.004), and short singlet state lifetime (τexpt ≈ 20-50ps), both increasing by a factor of ≈2 in going from polar acetonitrile to non-polar dioxane as solvent. DFT ZINDO calculations show a transition involving significant electron transfer from the diethyl-amino group into the carbonyl region of the molecule. In solution, in the presence of oxygen, the triplet state decays almost exclusively by oxygen quenching, and singlet oxygen is produced in high yield (Φ∆ ≈ 0.5-0.55). The triplet state absorbs across the 450-750nm region with maxima around 480 and 650nm, and moderate molar absorption coefficients (ca. 6000-8000M-1cm-1). In a glass at 77K, triplet decay gives a red phosphorescence, with λmax ≈ 640-650nm, and a ≈ 0.25s lifetime. If singlet oxygen yields are a good indication of triplet yields, then internal conversion and intersystem crossing occur with roughly equal efficiency.

Organic Non-Wettable Superhydrophobic Fullerite Films.

A long-standing quest in material science has been the development of non-wettable superhydrophobic films based on a single organic material, without the requirement of fluorination or silane treatment. Here, such films and coatings, which are developed using colloidal gels of fullerite C60 and C70 nanocrystals, are described. It is illustrated that despite the high surface energy of these van der Waals molecular crystals their gelation can create films having self-affine fractal surfaces with multiscale roughness. Water droplets on resulting surfaces of fullerite films bead like a pearl resting in a Fakir state with contact angle exceeding 150°. The films are extremely water repellent and non-wettable; when submerged in water they stay dry up to 3 h even at a water depth of two feet and exhibit the plastron effect. A series of experiments are presented to provide comprehensive inspection of water droplet dynamics on these films. These include rolling, bouncing, squeezing, freezing, melting, evaporating; along with acidic and alkaline tests. Non-wettable films of such materials are unique as fullerites get photosensitized instantaneously generating extremely high yields (≈100%) of singlet oxygen (1 O2 ) that can destroy viruses and bacteria; thereby enabling their use in rheology, water purification, and medicinal devices.

Self-assembly of Amphiphilic Porphyrins To Construct Nanoparticles for Highly Efficient Photodynamic Therapy.

Hydrophobic photosensitizers greatly affect cell permeability and enrichment in tumors, but they cannot be used directly for clinical applications because they always aggregate in water, preventing their circulation in the blood and accumulation in tumor cells. As a result, amphiphilic photosensitizers are highly desirable. Although nanomaterial-based photosensitizers can solve water solubility, they have the disadvantages of complicated operation, poor reproducibility, low drug loading, and poor stability. In this work, an efficient synthesis strategy is proposed that converts small molecules into nanoparticles in 100 % aqueous solution by molecular assembly without the addition of any foreign species. Three photosensitizers with triphenylphosphine units and ethylene glycol chains of different lengths, TPP-PPh3 , TPP-PPh3 -2PEG and TPP-PPh3 -4PEG, were synthesized to improve amphiphilicity. Of the three photosensitizers, TPP-PPh3 -4PEG is the most efficient (singlet oxygen yield: 0.89) for tumor photodynamic therapy not only because of its definite constituent, but also because its amphiphilic structure allows it to self-assemble in water.

Genetic autonomy and low singlet oxygen yield support kleptoplast functionality in photosynthetic sea slugs.

The kleptoplastic sea slug Elysia chlorotica consumes Vaucheria litorea, stealing its plastids, which then photosynthesize inside the animal cells for months. We investigated the properties of V. litorea plastids to understand how they withstand the rigors of photosynthesis in isolation. Transcription of specific genes in laboratory-isolated V. litorea plastids was monitored for 7 days. The involvement of plastid-encoded FtsH, a key plastid maintenance protease, in recovery from photoinhibition in V. litorea was estimated in cycloheximide-treated cells. In vitro comparison of V. litorea and spinach thylakoids was applied to investigate reactive oxygen species formation in V. litorea. In comparison to other tested genes, the transcripts of ftsH and translation elongation factor EF-Tu (tufA) decreased slowly in isolated V. litorea plastids. Higher levels of FtsH were also evident in cycloheximide-treated cells during recovery from photoinhibition. Charge recombination in PSII of V. litorea was found to be fine-tuned to produce only small quantities of singlet oxygen, and the plastids also contained reactive oxygen species-protective compounds. Our results support the view that the genetic characteristics of the plastids are crucial in creating a photosynthetic sea slug. The plastid's autonomous repair machinery is likely enhanced by low singlet oxygen production and elevated expression of FtsH.