High Singlet Oxygen Quantum Yield Research Articles

Sonophotochemical and photochemical efficiency of thiazole-containing metal phthalocyanines and their gold nanoconjugates.

This study presents the synthesis of some metal {M = Zn(II), Lu(III), Si(IV)} phthalocyanines bearing chlorine and 2-(4-methylthiazol-5-yl) ethoxy groups at peripheral or axial positions. The newly synthesized metal phthalocyanines were characterized by applying FT-IR, 1H NMR, mass, and UV-Vis spectroscopic approaches. Additionally, the surface of gold nanoparticles was modified with zinc(II) and silicon(IV) phthalocyanines. The resultant nanoconjugates were characterized using TEM images. Moreover, the effect of metal ions and position of substituent, and gold nanoparticles on the photochemical and sonophotochemical properties of the studied phthalocyanines was investigated. The highest singlet oxygen quantum yield was obtained for the lutetium phthalocyanine by applying photochemical and sonophotochemical methods. However, the linkage of the zinc(II) and silicon(IV) phthalocyanines to the surface of gold nanoparticles improved significantly their singlet oxygen generation capacities.

Synthesis and biological evaluation of bi-modal BODIPY-conjugated Hoechst applicable for Auger-electron and photodynamic cancer therapy

Current therapeutic approaches to cancer are not fully effective, and so development of more effective treatment is needed. Auger-electron therapy and photodynamic therapy have attracted marked attentions as a promising strategy in cancer treatment. In this study, we synthesized [125I]BH-2/BH-2, which comprised Hoechst and 2,6-diiodo-substituted BODIPY, and evaluated its usefulness as a bi-modal agent for Auger-electron/photodynamic therapy by comparison with the previously reported compound [125I]BH/BH. [125I]BH-2 was obtained at a 13% radiochemical yield. [125I]BH-2 showed similar uptake into the nucleus to [125I]BH, suggesting that Hoechst can function as a nuclear localization tag. HeLa cell viabilities were reduced in both cells exposed to [125I]BH-2 and [125I]BH. γ-H2AX foci in HeLa cells exposed to [125I]BH-2 or [125I]BH were increased in a dose-dependent manner, indicating that DNA double-strand breaks may have occurred. No significant difference was observed between [125I]BH-2 and [125I]BH at these investigations. For PDT application, BH-2 showed a higher singlet oxygen quantum yield (ΦΔ) and caused superior photo-induced cytotoxicity in HeLa cells compared with BH. These results suggest that bi-modal [125I]BH-2/BH-2 can cause anti-tumor effects with Auger-electron and photodynamic therapy.

FRET-based two-photon benzo[a] phenothiazinium photosensitizer for fluorescence imaging-guided photodynamic therapy

To overcome the conflict between the long-wavelength excitation and high singlet oxygen quantum yield of photosensitizers, we conjugated a two-photon fluorophore, tetrahydroquinoxaline coumarin (TQ), and an efficient photodynamic therapeutic agent, benzo[a]phenothiazinium (NBS-NH2), through a hexamethylene linker to build a two-photon photosensitizer, TQ-NBS. In TQ-NBS, TQ served as an energy donor and NBS-NH2 acted as an energy acceptor; and TQ-NBS was a Förster resonance energy transfer (FRET) cassette with a 92.8% efficiency. The large two-photon absorption cross-section of TQ allowed photosensitizer TQ-NBS to work in a 900 nm two-photon excitation (TPE) mode, which greatly benefited the deep tissue penetration in PDT treatment. Meanwhile, the excellent phototoxicity and near-infrared fluorescence of NBS-NH2 was kept in TQ-NBS under a TPE mode via a FRET process. Photosensitizer TQ-NBS exhibited a high phototoxic efficacy in living cells and tumor-bearing mice.

The photodynamic activity properties of a series of structurally analogous tetraarylporphyrin, chlorin and N-confused porphyrin dyes and their Sn(IV) complexes

A series of tetraarylporphyrin, -chlorin and N-confused porphyrin dyes with 4‑methoxy‑meso-aryl rings (1-Por, 1-Chl and 1-NCP) and their Sn(IV) complexes (1-SnPor, 1-SnChl and 1-SnNCP) have been synthesized and characterized. The heavy atom effect of the Sn(IV) ion results in relatively high singlet oxygen quantum yield values of 0.67, 0.71 and 0.85 for 1-SnPor, 1-SnChl and 1-SnNCP, respectively. The photodynamic activities of 1-Por, 1-Chl, 1-NCP, 1-SnPor, 1-SnChl and 1-SnNCP were determined against MCF-7 breast cancer cells through illumination with Thorlabs 625 or 660 nm (240 or 280 mW.cm−2) light emitting diodes (LEDs) for 20 min. The IC50 values for 1-SnChl and 1-SnNCP lie between 1.4 − 6.1 and 1.6 − 4.8 µM upon photoirradiation with the 660 and 625 nm LEDs, respectively, while higher values of >10 µM were obtained for 1-SnPor and the free base dyes. In a similar manner, 1-SnChl and 1-SnNCP were found to also have significantly higher photodynamic antimicrobial activity against planktonic Gram-(+) Staphylococcus aureus and Gram-(−) Escherichia coli bacteria than the other dyes studied. Upon illumination with Thorlabs 625 and 660 nm LEDs for 75 min, Log10 reduction values of 7.62 and > 2.40−3.69 were obtained with 1 and 5 µM solutions, respectively.

Efficient Spin-Orbit Charge-Transfer Intersystem Crossing and Slow Intramolecular Triplet-Triplet Energy Transfer in Bodipy-Perylenebisimide Compact Dyads and Triads.

Bodipy (BDP)-perylenebisimide (PBI) donor-acceptor dyads/triad were prepared to study the spin-orbit charge-transfer intersystem crossing (SOCT-ISC). For BDP-PBI-3, in which BDP was attached at the imide position of PBI, higher singlet oxygen quantum yield (ΦΔ =85 %) was observed than the bay-substituted derivative BDP-PBI-1 (ΦΔ =30 %). Femtosecond transient absorption spectra indicate slow Förster resonance energy transfer (FRET; 40.4 ps) and charge separation (CS; 1.55 ns) in BDP-PBI-3, while for BDP-PBI-1, CS takes 2.8 ps. For triad BDP-PBI-2, ultrafast FRET (149 fs) and CS (4.7 ps) process were observed, the subsequent charge recombination (CR) takes 5.8 ns and long-lived 3 PBI* (179.8 μs) state is populated. Nanosecond transient absorption spectra of BDP-PBI-3 show that the CR gives upper triplet excited state (3 BDP*) and subsequently, via a slow intramolecular triplet energy transfer (14.5 μs), the 3 PBI* state is finally populated, indicating that upper triplet state is involved in SOCT-ISC. Time-resolved electron paramagnetic resonance spectroscopy revealed that both radical pair ISC (RP ISC) and SOCT-ISC contribute to the ISC. A rare electron spin polarization of (e, e, e, e, e, e) was observed for the triplet state formed via the RP ISC mechanism, due to the S-T+1 /T0 states mixing.

Rational design of β-carboline as an efficient type I/II photosensitizer to enable hypoxia-tolerant chemo-photodynamic therapy

Photodynamic therapy (PDT) is a clinically approved treatment for cancer due to its high spatiotemporal selectivity and non-invasive modality. However, its therapeutic outcomes are always limited to the severe hypoxia environment of the solid tumor. Herein, two novel photosensitizers HY and HYM based on naturally antitumor alkaloids β-carboline were designed and synthesized. Through a series of experiments, we found HY and HYM can produce type II ROS (singlet oxygen) after light irradiation. HYM had higher singlet oxygen quantum yield and molar extinction coefficient than HY, as well as type I PDT behavior, which further let us find that HYM could exhibit robust phototoxicity activities in both normoxia and hypoxia. Meanwhile, HYM showed tumor-selective cytotoxicity with minimal toxicity toward normal cells. Notably, thanks to HYM's hypoxia-tolerant type I/II PDT and tumor selective chemotherapy, HYM showed synergistic inhibitory effect on tumor growth (inhibition rate > 91%). Our research provides a promising photosensitizer for hypoxia-tolerant chemo-photodynamic therapy, and may also give a novel molecular skeleton for photosensitizer design.

Tumor‐pH‐value responsive non‐peripheral substituted phthalocyanines: Synthesis, investigation of photophysical and photochemical properties

Cancer is one of the diseases with the highest mortality rate worldwide. Although PDT has recently produced encouraging outcomes, there are still many areas that need to be improved. The first of these is the negative consequences faced by patients treated with the PDT method when exposed to sunlight. For this reason, a new PDT method has been developed in recent years, and it is aimed at using photosensitizer molecules that can be active in acidic conditions. Since the pH values of tumor tissues are more acidic than normal tissues, preparing molecules that act effectively in acidic conditions will allow for more effective results in treating cancer with PDT. In this context, within the scope of this study, 3‐(4‐propionylphenoxy)phthalonitrile (1) and its non‐peripheral tetra‐substituted phthalocyanine derivatives [(2), (3), and (4)] were prepared. With these phthalocyanine derivatives, the novel compounds (5), (6), and (7) were synthesized for the first time. The aggregation tendencies of newly synthesized phthalocyanines (5–7) were investigated in solvent media. The effects of pH changes upon UV–Vis and fluorescence spectra were performed. The electronic and emission spectra of synthesized phthalocyanine derivatives are highly sensitive to pH changes. Formation constant (LogK) values of mono‐ and di‐protonated phthalocyanine forms were calculated by the Henderson–Hasselback equation. The mono‐ and di‐protonated species' equilibrium constants (logK1 and logK2) were calculated as ~5.0. This value may be promising for pH‐sensitizing photosensitizers. Also, the photophysical and photochemical properties of synthesized metallophthalocyanine derivatives (2) and (5) were studied at different pH values. The singlet oxygen quantum yield of (2) and (5) was calculated to be 0.78 and 0.81 in DMSO, respectively. When pH = 6.4, that is, tumor‐pH‐values, this value for (5) has increased to 0.92. The newly synthesized phthalocyanines are suitable photosensitizers for PDT applications, especially with high singlet oxygen quantum yield at pH 6.4.

Aza-BODIPY dye with unexpected bromination and high singlet oxygen quantum yield for photoacoustic imaging-guided synergetic photodynamic/photothermal therapy

Introducing heavy halogen atoms into organic small molecules is a practical strategy for efficient singlet oxygen (1O2) generation. Generally, bromine or iodine atoms are introduced on the aza-boron-dipyrromethene (aza-BODIPY) core, rather than on the periphery aryl rings for efficient 1O2 generation. Herein, an aza-BODIPY dye NBDPBr with unexpected bromination on the periphery aryl rings was synthesized for photoacoustic (PA) imaging-guided synergistic photothermal therapy (PTT) and photodynamic therapy (PDT) in tumor cells. Owing to unexcepted bromination at the periphery aryl rings, NBDPBr demonstrated an outstanding singlet oxygen quantum yield (ΦΔ) of 66% which was superior to similar brominated photosensitizers previously reported. After encapsulation with amphiphilic polymer F-127, hydrophilic NBDPBr nanoparticles (NPs) were fabricated and exhibited an excellent photothermal conversion efficiency (η) of 43.0% under 660 nm photoirradiation. In vivo PA imaging results demonstrated that NBDPBr NPs could specifically accumulate at tumor sites and realized the maximum tumor retention at 7 h post-injection. All the in vitro and in vivo results indicated the significant potence of NBDPBr with unexpected bis-bromination for PA imaging-guided synergetic PDT/PTT.

A lysosomes and mitochondria dual-targeting AIE-active NIR photosensitizer: Constructing amphiphilic structure for enhanced antitumor activity and two-photon imaging.

Development of lysosomes and mitochondria dual-targeting photosensitizer with the virtues of near-infrared (NIR) emission, highly efficient reactive oxygen generation, good phototoxicity and biocompatibility is highly desirable in the field of imaging-guided photodynamic therapy (PDT) for cancer. Herein, a new positively charged amphiphilic organic compound (2-(2-(5-(7-(4-(diphenylamino)phenyl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)vinyl)-3-methylbenzo[d]thiazol-3-ium iodide) (ADB) based on a D-A-π-A structure is designed and comprehensively investigated. ADB demonstrates special lysosomes and mitochondria dual-organelles targeting, bright NIR aggregation-induced emission (AIE) at 736​nm, high singlet oxygen (1O2) quantum yield (0.442), as well as good biocompatibility and photostability. In addition, ADB can act as a two-photon imaging agent for the elaborate observation of living cells and blood vessel networks of tissues. Upon light irradiation, obvious decrease of mitochondrial membrane potential (MMP), abnormal mitochondria morphology, as well as phagocytotic vesicles and lysosomal disruption in cells are observed, which further induce cell apoptosis and resulting in enhanced antitumor activity for cancer treatment. In vivo experiments reveal that ADB can inhibit tumor growth efficiently upon light exposure. These findings demonstrate that this dual-organelles targeted ADB has great potential for clinical imaging-guided photodynamic therapy, and this work provides a new avenue for the development of multi-organelles targeted photosensitizers for highly efficient cancer treatment.

BODIPYs with Chalcogenophenes at Boron: Synthesis and Properties.

Reported herein are the synthesis and characterization of BODIPYs bearing heterocycles at boron. To synthesize this series, various chalcogenophenes (furan, thiophene, selenophene, and tellurophene) were lithiated and then used as nucleophiles to attack the boron center of a parent F-BODIPY. Compounds in the series were compared with respect to their photophysical and structural properties, and trends were discussed. By virtue of the "heavy atom effect", as the mass of the heterocycle appended to the BODIPY core increases, compounds exhibit a higher singlet oxygen quantum yield. The BODIPY with tellurophene at boron exhibits the highest quantum yield (ΦΔ = 0.68) in the series and reduced emission (Φf = 0.01).

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

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

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

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

Photodynamic Anticancer and Antibacterial Activities of Sn(IV) N-Confused Meso-tetra(methylthiophenyl)porphyrin

A Sn(IV) meso-tetra(4-methylthiolphenyl) N-confused porphyrin (4-Sn) complex was prepared to facilitate a comparison of the photophysicochemical and singlet oxygen photosensitiser properties of a series of Sn(IV) complexes of meso-4-methylthiolphenyl-substituted porphyrin, corrole, chlorin, and N-confused porphyrin. 4-Sn has an unusually high singlet oxygen quantum (ΦΔ) yield of 0.88, markedly higher than the ΦΔ values of the other complexes in this series. A Thorlabs M660L4 LED (280 mW · cm−2) was used to study the photodynamic activity of Sn-4 against the MCF-7 cancer cell line through irradiation at 660 nm for 30 min. The IC50 value was calculated to be 1.4 (± 0.8) µM, markedly lower than the previously reported values for the rest of the series. Photodynamic antimicrobial activity was also determined against Staphylococcus aureus and Escherichia coli, and 4-Sn was found to deactivate both Gram-(+) and Gram-(−) bacteria despite the absence of cationic charges on the ligand structure.

Synthesis, characterization and photodynamic antitumor activity of amine-modified zinc (II) phthalocyanines

In order to reduce the intramolecular charge-transfer (ICT) effect of amine groups on the photophysical properties of zinc (II) phthalocyanine (ZnPc), tertiary amines were covalently connected with ZnPc ring via ethyl p-hydroxybenzoate or diethyl 5-hydroxyisophthalate. Six new tertiary amine-modified ZnPcs were therefore synthesized and characterized. Meanwhile, the corresponding quaternary ammonium ZnPcs were also synthesized. The effects of different substitution ways (mono-substitutions, symmetrical tetra-substitutions, or asymmetric tetra-substitutions) and the numbers of different substitutions on the photophysical and physicochemical properties of these ZnPcs were studied. All twelve ZnPcs had relatively high singlet oxygen quantum yields (ΦΔ = 0.32–0.68) and fluorescence quantum yields (ΦF = 0.23–0.40), where the amine-containing substituents did not show obvious ICT effect. All ZnPcs showed effective phototoxicity towards breast cancer cells (IC50 = 63–366 nmol/L). Among them, three tetra-substituted ZnPcs containing quaternary ammonium groups (4aN, 4bN and 4cN) showed the best in vitro anticancer photodynamic activities with IC50 = 64–76 nmol/L, which owned to their relatively high cellular uptake. The tumor inhibition rate of 4aN on H22 tumor-bearing mice reached 87% (4aN dose: 3 nmol/g; light dose: 685 nm, 135 J/cm2).

Heptamethine Cyanine‐Based Nanotheranostics with Catalase‐Like Activity for Synergistic Phototherapy of Cancer

AbstractSingle‐molecule photosensitizers (PSs) for synergistic phototherapy are desirable but highly challenging, due to the competitive relationship between photothermal (PTT) and photodynamic therapy (PDT). Herein, a supramolecular strategy is developed that can tune the stacking pattern of PS molecules in their aggregates to optimize the PTT/PDT efficiency. Specifically, near‐infrared (NIR) heptamethine cyanines (Cy7) are synthesized using tricyanofuran (TCF) as the acceptor and benzothiazole (BTH)/indole (IND) as the donor, where BTH is a less hydrogen‐bonded tecton relative to IND. Both IND‐Cy7‐TCF and BTH‐Cy7‐TCF have similar photophysical properties at the molecular level, but BTH‐Cy7‐TCF in aggregated state exhibits higher singlet oxygen quantum yield (1.3% vs 0.2%) and competitive photothermal conversion efficiency (56.4% vs 62.3%) compared to IND‐Cy7‐TCF, due to the fine‐tuning of hydrogen bonding and intermolecular π–π interactions to form loose molecular stacks. Interestingly, the unique molecular stacking structure provides a binding site and catalytic center for H2O2 that exhibits catalase‐like activity, which can further ameliorate the efficiency of PDT and enhance the synergistic effect of PDT/PTT phototherapy in vitro and in vivo. This study can provide a simple but effective supramolecular strategy to design small molecule PSs with desirable aggregated structure for synergistic dual‐mode phototherapy.

Bichromophoric Photosensitizers: How and Where to Attach Pyrene Moieties to Phenanthroline to Generate Copper(I) Complexes

Pyrene is a polycyclic aromatic hydrocarbon and organic dye that can form superior bichromophoric systems when combined with a transition metal-based chromophore. However, little is known about the effect of the type of attachment (i.e., 1- vs 2-pyrenyl) and the individual position of the pyrenyl substituents at the ligand. Therefore, a systematic series of three novel diimine ligands and their respective heteroleptic diimine-diphosphine copper(I) complexes has been designed and extensively studied. Special attention was given to two different substitution strategies: (i) attaching pyrene via its 1-position, which occurs most frequently in the literature, or via its 2-position and (ii) targeting two contrasting substitution patterns at the 1,10-phenanthroline ligand, i.e., the 5,6- and the 4,7-position. In the applied spectroscopic, electrochemical, and theoretical methods (UV/vis, emission, time-resolved luminescence and transient absorption, cyclic voltammetry, density functional theory), it has been shown that the precise choice of the derivatization sites is crucial. Substituting the pyridine rings of phenanthroline in the 4,7-position with the 1-pyrenyl moiety has the strongest impact on the bichromophore. This approach results in the most anodically shifted reduction potential and a drastic increase in the excited state lifetime by more than two orders of magnitude. In addition, it enables the highest singlet oxygen quantum yield of 96% and the most beneficial activity in the photocatalytic oxidation of 1,5-dihydroxy-naphthalene.

The Photodynamic Anticancer and Antibacterial Activity Properties of a Series of meso-Tetraarylchlorin Dyes and Their Sn(IV) Complexes.

A series of tetraarylchlorins with 3-methoxy-, 4-hydroxy- and 3-methoxy-4-hydroxyphenyl meso-aryl rings (1-3-Chl) and their Sn(IV) complexes (1-3-SnChl) were synthesized and characterized so that their potential utility as photosensitizer dyes for use in photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) can be assessed. The photophysicochemical properties of the dyes were assessed prior to in vitro PDT activity studies against MCF-7 breast cancer cells through irradiation with Thorlabs 625 or 660 nm LED for 20 min (240 or 280 mW·cm-2). PACT activity studies were performed against both planktonic bacteria and biofilms of Gram-(+) S. aureus and Gram-(-) E. coli upon irradiation with Thorlabs 625 and 660 nm LEDs for 75 min. The heavy atom effect of the Sn(IV) ion results in relatively high singlet oxygen quantum yield values of 0.69-0.71 for 1-3-SnChl. Relatively low IC50 values between 1.1-4.1 and 3.8-9.4 µM were obtained for the 1-3-SnChl series with the Thorlabs 660 and 625 nm LEDs, respectively, during the PDT activity studies. 1-3-SnChl were also found to exhibit significant PACT activity against planktonic S. aureus and E. coli with Log10 reduction values of 7.65 and >3.0, respectively. The results demonstrate that the Sn(IV) complexes of tetraarylchlorins merit further in depth study as photosensitizers in biomedical applications.

Lysosome-targeting phenalenones as efficient type I/II photosensitizers for anticancer photodynamic therapy

Development of safe and effective photosensitizers is important for enhancing the efficacy of photodynamic cancer therapy. Phenalenone is a type II photosensitizer with a high singlet oxygen quantum yield; however, its short UV absorption wavelength hinders its application in cancer imaging and in vivo photodynamic therapy. In this study, we report a new redshift phenalenone derivative, 6-amino-5-iodo-1H-phenalen-1-one (SDU Red [SR]), as a lysosome-targeting photosensitizer for triple-negative breast cancer therapy. SDU Red produced singlet oxygen (Type II reactive oxygen species [ROS]) and superoxide anion radicals (Type I ROS) upon light irradiation. It also exhibited good photostability and a remarkable phototherapeutic index (PI > 76) against triple-negative breast cancer MDA-MB-231 cancer cells. Additionally, we designed two amide derivatives, SRE-I and SRE-II, with decreased fluorescence and photosensitizing capabilities based on SDU Red as activatable photosensitizers for photodynamic cancer therapy. SRE-I and SRE-II could be further converted into the active photosensitizer SDU Red via carboxylesterase-catalyzed amide bond cleavage. Moreover, SDU Red and SRE-II induced DNA damage and cell apoptosis in the presence of light. Therefore, SRE-II can act as a promising theranostic agent for triple-negative breast cancer.

Chlorophenyl thiophene silicon phthalocyanine: Synthesis, two-photon bioimaging-guided lysosome target, and in vitro photodynamic efficacy.

The development of efficient photosensitizers with high singlet oxygen quantum yield, strong fluorescent emission, excellent photostability, and specific organelle targeting is in great demand for the enhancement of PDT treatment efficiency. This study designed and synthesized a new two-photon photosensitizer chlorophenyl thiophene axially substituted silicon (IV) phthalocyanine (CBT-SiPc). CBT-SiPc showed specific targeting of lysosomes in living cells and good biocompatibility. Furthermore, high 1O2 generation efficiency and high PDT efficiency in MCF-7 breast cancers under irradiation were also demonstrated. The novel CBT-SiPc showed great potential in the application of lysosome-targeted and two-photon bioimaging-guided photodynamic cancer therapy.

New asymmetric AB3-type free-base and metalloporphyrin-cyclotriphosphazene conjugates: Synthesis and photophysical-photochemical properties

In this work, new asymmetric H2-(3), Zn(II)-(4) and Pd(II)-(5) porphyrin derivatives conjugated with a cyclotriphosphazene ring bearing 2‑naphtoxy groups in paraposition were synthesized and fully characterized. For investigation of photophysical and photochemical properties of these compounds; their ground state absorption, fluorescence emission, fluorescence lifetime, fluorescence quantum yield and singlet oxygen quantum yield measurements were studied in THF. The singlet oxygen quantum yields were determined as 0.62 for 3, 0.49 for 4 and 0.64 for 5 in THF, respectively. As a result, conjugation of the porphyrin macrocycle with the cyclotriphosphazene ring have improved the singlet oxygen generation except compound 4 when compared to tetraphenylporphyrin (TPP) (0.58) and ZnTPP (0.61) in THF. Especially, compound 5 has the highest singlet oxygen quantum yield (0.64) due to the heavy metal effect of Pd(II).