Phthalocyanine Chloride Tetrasulfonic Acid Research Articles

Aluminium phthalocyanine–mediated photodynamic therapy promotes antitumour activity in oesophageal cancer stem cells.

e15194 Background: Photodynamic therapy (PDT), a non-invasive treatment modality, has emerged as an effective treatment measure for various cancers, including oesophageal cancer. PDT has attracted much attention in the field of oncology due to its low toxicity profile and the selective accumulation of the photoactivated agent in the tumour cells. However, the therapeutic effect of Aluminium (III) Phthalocyanine Chloride Tetra sulfonic Acid (AlPcS4Cl) mediated PDT on oesophageal CSCs is limited. In this study, we evaluated the cellular localization of AlPcS4Cl and its PDT anticancer effects on oesophageal CSCs. Methods: An in vitro experimental design was employed in this study. Oesophageal cancer (HKESC-1 cells) was grown, and the CSCs were isolated using the magnetic-activated cell sorting (MACS). The isolated CSCs were characterised using a flow cytometry, Hoechst efflux side population test, and immunofluorescence. The CSCs were maintained in a serum-free culture medium and incubated at 37° C, 5% CO2 and 85% humidity. The cells were grouped into control and experimental groups. The CSCs received two-fold increasing concentrations of AlPcS4Cl and were exposed to irradiation at 673.2nm wavelength using a diode laser. After 24 hours post-PDT, the anticancer activities of AlPcS4Cl on oesophageal CSCs were examined. The MTT cell viability assay was used to determine the 50% inhibitory concentration (IC50), light microscopy for morphological changes, and adenosine triphosphate (ATP) assay for cell proliferation, lactate dehydrogenase (LDH) assay for cellular toxicity. While cellular localization of AlPcS4Cl was examined using fluorescent microscopy. All experimental and control cells were conducted in six biological replicates (n = 6). Results: Results were compiled, and statistical analysis was performed using GraphPad Prism (v5). The mean values of experimental groups were compared with the mean value of the control cells. One-way ANOVA was employed, and a p-value of less than 0.05 was considered statistically significant. Findings from cellular localization showed that the AlPcS4Cl is localized in the mitochondria and lysosomes, indicating a probable cellular death pathway. The dose-response of AlPcS4Cl on oesophageal CSCs showed an IC50 value of 4µM, suggesting the photosensitizer is efficient for the treatment of CSCs at low concentrations. The CSCs exposed to PDT showed remarkable morphological distortion, high cytotoxic activity, decreased viable cells and significant antiproliferative potential. Conclusions: This study showed that AlPcS4Cl promote PDT anticancer effects on oesophageal CSCs and could serve as an efficient therapeutic option for eradicating oesophageal CSCs.

Abstract 2419: A multimodel preclinical platform to evaluate photodynamic therapy as a strategy to reduce local recurrence in myxofibrosarcoma and osteosarcoma

Abstract Sarcomas are heterogeneous and rare malignant tumors that develop from connective tissues. Myxofibrosarcoma (MFS) and Osteosarcoma (OS) are the main representative subtypes of Soft tissues and Bone sarcomas. Conventional treatment consists of surgical resection and neo/adjuvant chemotherapy. However, a challenging clinical feature is a high local recurrence rate, calling for the development of novel strategies to eradicate MFS and OS. Fluorescence-guided surgery (FGS), coupled with photodynamic therapy (PDT), enables to detect and eradicate malignant tissues using a light-sensitive photosensitizer (PS). These compounds could be retained by neoplastic cells to a greater extent than by healthy tissue. Thus, when photoactivated, they lead to cancer cell death, minimizing normal tissues toxicity. The project aims to provide a preclinical proof of concept of FGS and PDT for MFS and OS, allowing us to pave the way for a more effective treatment strategy. A multimodel preclinical platform of MFS and OS comprising 2D, 3D-collagen based scaffold was developed. A MFS stabilized cell line (IM-MFS-1) and four OS cell lines (Saos-2, U-2 OS, MG-63, 143B) were used. NIH-3T3 fibroblast cell line was used as healthy counterpart. We tested a panel of synthetic PSs: Toluidine Blue, 5-Aminolevulinic Acid hydrochloride (ALA), Methylene Blue, Chlorin e6 (Ce6), Pheophorbide a (Pba) and Al(III) Phthalocyanine Chloride Tetrasulfonic Acid (AlPcS4) that can be photoactivated with light in the 630-660 nm wavelengths’ range. The PSs were ranked on (a) selective uptake by tumor cells, respect to healthy cells and (b) the cytotoxic effect, after photoactivation. PSs cell uptake was evaluated by Countess II FL automated cell counter. Cytotoxicity was evaluated by WST-1 and Presto Blue assays. For each PS we determined the highest concentration, causing less than 50% dark toxicity in IM-MFS-1, OS cell lines and fibroblast NIH-3T3, seeded in 2D and 3D collagen-based models. Then, we evaluated the cell viability upon light irradiation (λ=630 or 660 nm; 10 mW/cm^2, 5 min). For all PSs, dark toxicity was very low. However, only Ce6 was effectively uptaken by tumor cells (% uptake > 60%) and not by NIH-3T3 cells (% uptake = 27%). Moreover, upon photoactivation, Ce6 induced significantly higher cell death in cancer cells as compared to NIH-3T3 cells, e.g. 1-3% cell viability in tumor cells and 76% cell viability in NIH-3T3. Results from our multimodel platform highlight PDT as a powerful strategy for the treatment of MFS and OS. Among the screened PSs, Ce6 is the most promising, showing a remarkable selectivity in tumor cells uptake and cytotoxicity. To increase the clinical significance of our approach, we will confirm its efficacy in patient-derived primary cultures; xenograft zebrafish in vivo embryos will be used to evaluate how PDT affects the disease aggressiveness and metastatic potential. Citation Format: Chiara Spadazzi, Micaela Pannella, Chiara Bellotti, Elisa Martella, Silvia Vanni, Alessandro De Vita, Chiara Liverani, Giacomo Miserocchi, Claudia Cocchi, Chiara Calabrese, Valentina Fausti, Roberto Casadei, Federica Pieri, Ania Naila Guerrieri, Giovanni Martinelli, Greta Varchi, Enrico Lucarelli, Laura Mercatali, Toni Ibrahim. A multimodel preclinical platform to evaluate photodynamic therapy as a strategy to reduce local recurrence in myxofibrosarcoma and osteosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2419.

A Photochemical Crosslinking Approach to Enhance Resistance to Mechanical Wear and Biochemical Degradation of Articular Cartilage

ObjectiveThe objective of this study was to evaluate photochemical crosslinking using Al(III) phthalocyanine chloride tetrasulfonic acid (CASPc) and light with a wavelength of 670 nm as a potential therapy to strengthen articular cartilage and prevent tissue degradation.DesignChanges in viscoelastic properties with indentation were used to identify 2 crosslinking protocols for further testing. Crosslinked cartilage was subjected to an in vitro, accelerated wear test. The ability of the crosslinked tissue to resist biochemical degradation via collagenase was also measured. To better understand how photochemical crosslinking with CASPc varies through the depth of the tissue, the distribution of photo-initiator and penetration of light through the tissue depth was characterized. Finally, the effect of CASPc on chondrocyte viability and of co-treatment with an antioxidant was evaluated.ResultsThe equilibrium modulus was the most sensitive viscoelastic measure of crosslinking. Crosslinking decreased both mechanical wear and collagenase digestion compared with control cartilage. These beneficial effects were realized despite the fact that crosslinking appeared to be localized to a region near the articular surface. In addition, chondrocyte viability was maintained in crosslinked tissue treated with antioxidants.ConclusionThese results suggest that photochemical crosslinking with CASPc and 670 nm light holds promise as a potential therapy to prevent cartilage degeneration by protecting cartilage from mechanical wear and biochemical degradation. Limitations were also evident, however, as an antioxidant treatment was necessary to maintain chondrocyte viability in crosslinked tissue.

Functional titanium dioxide nanoparticle conjugated with phthalocyanine and folic acid as a promising photosensitizer for targeted photodynamic therapy in vitro and in vivo

Photodynamic therapy (PDT) is a promising cancer treatment that can be implemented using various agents. The conventional photosensitizer Al (III) phthalocyanine chloride tetrasulfonic acid (Pc) has limitations of selectivity in tumor targeting, low affinity to cancer cells, and low two-photon absorption. This study presents a novel photosensitizer FA-TiO2-Pc, which has the TiO2 nanoparticle conjugated with a tumor targeting agent of folic acid (FA), and Pc. FA-TiO2-Pc possessed high targeted photodynamic therapeutic activity and excellent biocompatibility. This promising photosensitizer showed high therapeutic drug efficiency in vitro at a low concentration dose and short incubation time under one-photon excitation (OPE). In vivo, when treated with a low dose of FA-TiO2-Pc and low light irradiation, the tumor growth was depressed in mice bearing HeLa xenograft tumors with minimal side effects. In addition, the two-photon absorption of FA-TiO2-Pc was also enhanced compared to Pc, proving that FA-TiO2-Pc system has a great potential to be used for the therapy of the folate receptor positive cancer cells in both OPE-PDT and two-photon excitation (TPE)-PDT agents.

Effect of dose responses of hydrophilic aluminium (III) phthalocyanine chloride tetrasulphonate based photosensitizer on lung cancer cells

Photodynamic therapy (PDT) is a promising approach for the treatment of different types of cancer and has been brought into focus for its synergy, compatibility, repeatability, relatively inexpensive cost and it's typically more efficacious nature. Photosensitizers (PSs) play a major role in PDT and are the core of this specific therapy. Al (III) Phthalocyanine Chloride Tetra sulfonic Acid (AlPcS4Cl) PS is an aromatic macrocyclic metal-based compound that is synthetically derived. It aids in deep tissue penetration due to its far red light activation wavelength, low photo bleaching, increased quantum yields and stability. Lung cancer is a leading cause of cancer related deaths worldwide accounting for approximately 1 in 5 of all cancer-related deaths. In this study, we explored the photochemical properties of AlPcS4Cl, its uptake into lung cancer, the intracellular localization and photodynamic action on lung cancer (A549 cells). Results indicated that AlPcS4Cl is a stable PS that localizes in intracellular organelles including the mitochondrion and lysosomes. PDT using AlPcS4Cl indicated an increase in cell death and decrease in cell proliferation and viability. AlPcS4Cl showed to be effective in treating lung cancer in vitro, however the resulting PDT efficacy will finally depend on the biological features such as tumour vasculature and tumour specific accumulation when used as a clinical application. It is noted that PDT can be considered as an adjunct therapy until standard protocols for various tumour types along with a relevant PS has been validated.

Nanosystem Integrated with Photosensitizer and Novel Targeting Chemotherapy Agent for Gastric Cancer Chemo-Photodynamic Combined Therapy.

The poor cell membrane penetration ability of photosensitizers resulted in the limited antitumor effect, thereby hampered their potential in clinical translation. The high toxic side effect and multidrug resistance of chemotherapeutic agents during in clinical chemical therapy should be resolved. Nanosystem integrated with photosensitizer and novel targeting chemotherapy agent may be an effective strategy for overcoming clinical or preclinical drawbacks of monotherapy and enhancing therapeutic effect. Therefore, a nanosized micelle F127 integrated with Apogossypolone (ApoG2) and Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) (referred as F127-ApoG2@AlPcS4) was synthesized to induce the cell death quickly for reducing the risk of resistance and enhancing gastric cancer therapeutic efficiency by combining AlPcS4/photodynamic therapy and ApoG2/chemotherapy. Hydrophobic of ApoG2 and hydrophilic of AlPcS4 self-assembled into this micelle to formation of core-shell structure based on the amphiphilic character of F127 micelle. The reactive oxygen species-dependent mitochondria membrane permeability was improved effectively because of reactive oxygen species generation of ApoG2, thereby resulting in a considerable amount of AlPcS4 and ApoG2 entering the mitochondrial. The AlPcS4 binding site was altered from the cytoplasm to the cell nucleus at higher concentration because of the existence of ApoG2. With irradiation, ApoG2 and AlPcS4 showed effective synergistic anti-tumor effect through inducing apoptosis due to singlet oxygen production regulated mainly by AlPcS4, reactive oxygen species accumulation and calcium overload regulated mainly by ApoG2. Intranuclear AlPcS4 caused cell death through necrosis. The apoptosis induced by AlPcS4 was earlier than ApoG2. In summary, F127-ApoG2@AlPcS4 quickly induced a long-lasting apoptosis that led to cell death, which could be a promising nanosized reagent for gastric cancer therapy based on chemo-photodynamic combined therapy.

Comparison of the synergistic anticancer activity of AlPcS4 photodynamic therapy in combination with different low‑dose chemotherapeutic agents on gastric cancer cells.

Limited cellular delivery and internalization efficiency of Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) induce poor penetration ability in cells and a slight photodynamic therapy (PDT) effect on gastric cancer. The combination treatment of AlPcS4/PDT with low-dose chemotherapeutic agents may provide a promising treatment strategy to increase the weak delivery efficiency of AlPcS4, reducing the dose of chemical agents without reducing efficacy, and improving apoptosis-inducing abilities, thereby increasing the antitumor effects and decreasing the noxious side effects on gastric cancer. We investigated and compared the synergistic antitumor growth effect on gastric cancer cells by combining AlPcS4/PDT treatment with different low-dose chemotherapeutic agents, namely, 5-fluorouracil (5-FU), doxorubicin (DOX), cisplatin (CDDP), mitomycin C (MMC), and vincristine (VCR). The inhibitory effect was increased in treatments that combined AlPcS4/PDT with all the aforementioned low-dose chemotherapeutic agents, to a different extent. An evident synergistic effect was obtained in the combination treatment of AlPcS4/PDT with low-dose 5-FU, DOX, and MMC by increasing AlPcS4 intracellular uptake ability, improving apoptosis-inducing abilities, and prolonging apoptosis-inducing time. The low-dose chemotherapeutic agents prolonged the apoptosis-inducing period of AlPcS4/PDT, and AlPcS4/PDT quickly improved apoptosis-inducing abilities of chemotherapy even at low doses. Generally, the combination treatment of AlPcS4/PDT with low-dose chemotherapeutic agents had significant antitumor growth effects in addition to a low dark-cytotoxicity effect on gastric cancer, thereby representing an effective and feasible therapy method for gastric cancer.

Enhancing integration of articular cartilage grafts via photochemical bonding.

The integration of osteochondral grafts to native articular cartilage is critical as the lack of graft integration may lead to continued tissue degradation, poor load transfer and inadequate nutrient transport. Photochemical bonding promotes graft integration by activating a photosensitizer at the interface via a light source and avoids negative effects associated with other bonding techniques. We hypothesized that the bond strength depends on photosensitizer type and concentration in addition to light exposure. Photochemical bonding was evaluated using methylene blue (MB), a cationic phenothiazine photosensitizer, and two phthalocyanine photosensitizers, Al(III) phthalocyanine chloride tetrasulfonic acid (CASPc) and aluminum phthalocyanine chloride (AlPc). Exposure was altered by varying irradiation time for a fixed irradiance or by varying irradiance with a fixed irradiation time. MB was ineffective at producing bonding at the range of concentrations tested while CASPc produced a peak twofold bond strength increase over controls. AlPc produced substantial bonding at all concentrations with a peak 3.9-fold bond strength increase over controls. Parametric tests revealed that bond strength depended primarily on the total energy delivered to the bonding site rather than the rate of light delivery or light irradiance. Bond strength persisted for 1 week of in-vitro culture, which warrants further exploration for clinical applications. These studies indicate that photochemical bonding is a viable strategy for enhancing articular cartilage graft integration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2406-2415, 2018.

Decomposition of xenobiotics during visible light irradiation in the presence of immobilised photosensitisers: kinetics study.

The objective of this work was to study the photosensitised oxidation of the xenobiotics benzylparaben (BeP) and 2,4dichlorophenol (2,4DCP) in aqueous solutions using photosensitisers immobilised into chitosan carrier particles and visible light radiation. Zn(II) phthalocyanine tetrasulfonate tetrasodium salt and Al(III) phthalocyanine chloride tetrasulfonic acid were used as photosensitisers. The major role of the singlet oxygen during photodegradation was proven by using scavengers of reactive oxygen species. The influence of initial xenobiotic concentration and temperature on degradation rate was examined. The investigations were focused on kinetics (Langmuir-Hinshelwood model) as well as activation energy determination. Moreover, the adsorption isotherms of BeP and 2,4DCP into chitosan carrier were determined using the Brunauer-Emmett-Teller model.

An O2 Self‐Sufficient Biomimetic Nanoplatform for Highly Specific and Efficient Photodynamic Therapy

Conventional oxygen‐dependent photodynamic therapy (PDT) has faced severe challenges because of the non‐specificity of most available photosensitizers (PSs) and the hypoxic nature of tumor tissues. Here, an O2 self‐sufficient cell‐like biomimetic nanoplatform (CAT‐PS‐ZIF@Mem) consisting of the cancer cell membrane (Mem) and a cytoskeleton‐like porous zeolitic imidazolate framework (ZIF‐8) with the embedded catalase (CAT) protein molecules and Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4, defined as PS) is developed. Because of the immunological response and homologous targeting abilities of the cancer cell membrane, CAT‐PS‐ZIF@Mem is selectively accumulated at the tumor site and taken up effectively by tumor cells after intravenous injection. After the intracellular H2O2 penetration into the framework, it is catalyzed by CAT to produce O2 at the hypoxic tumor site, facilitating the generation of toxic 1O2 for highly effective PDT in vivo under near‐infrared irradiation. By integrating the immune escape, cell homologous recognition, and O2 self‐sufficiency, this cell‐like biomimetic nanoplatform demonstrates highly specific and efficient PDT against hypoxic tumor cells with much reduced side‐effect on normal tissues.

A Triple‐Collaborative Strategy for High‐Performance Tumor Therapy by Multifunctional Mesoporous Silica‐Coated Gold Nanorods

To integrate treatments of photothermal therapy, photodynamic therapy (PDT), and chemotherapy, this study reports on a multifunctional nanocomposite based on mesoporous silica‐coated gold nanorod for high‐performance oncotherapy. Gold nanorod core is used as the hyperthermal agent and mesoporous silica shell is used as the reservoir of photosensitizer (Al(III) phthalocyanine chloride tetrasulfonic acid, AlPcS4). The mesoporous silica shell is modified with β‐cyclodextrin (β‐CD) gatekeeper via redox‐cleavable Pt(IV) complex for controlled drug release. Furthermore, tumor targeting ligand (lactobionic acid, LA) and long‐circulating poly(ethylene glycol) chain are introduced via host–guest interaction. It is found that the nanocomposite can specifically target to hepatoma cells by virtue of the LA targeting moiety. Due to the abundant existence of reducing agents within tumor cells, β‐CD can be removed by reducing the Pt(IV) complex to active cisplatin drug for chemotherapy, along with the releasing of entrapped AlPcS4 for effective PDT. As confirmed by in vitro and in vivo studies, the nanocomposite exhibits an obvious near‐infrared induced thermal effect, which significantly improves the PDT and chemotherapy efficiency, resulting in a superadditive therapeutic effect. This collaborative strategy paves the way toward high‐performance nanotherapeutics with a superior antitumor efficacy and much reduced side effects.

Synergistic Integration of Layer-by-Layer Assembly of Photosensitizer and Gold Nanorings for Enhanced Photodynamic Therapy in the Near Infrared.

A layer-by-layer (LbL) assembly strategy was used to incorporate high concentrations of Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) photosensitizer (PS) onto plasmonic Au nanorings (Au NRs) for increasing the cellular uptake of AlPcS4 and subsequently enhancing the efficacy of photodynamic therapy (PDT) of human breast cancer cells (MDA-MB-231) in the near-infrared (NIR) range. Au NRs with two layers of AlPcS4 (Au NR/(AlPcS4)2) markedly increased the cellular internalization of AlPcS4 and elevated the generation of reactive oxygen species (ROS). Quenching the photosensitivity of AlPcS4 on the Au NR surface during the uptake and then significant ROS formation only upon PS release inside the cellular compartment made it possible to achieve a high PDT specificity and efficacy. PDT of breast cancer cells following 4 h of incubation with various formula revealed the following cell destruction rate: ∼10% with free AlPcS4, ∼23% with singly layered Au NR/(AlPcS4)1 complex, and ∼50% with doubly layered Au NR/(AlPcS4)2. Incubation with Au NR/(AlPcS4)2 for an additional 2 h resulted in ∼85% cell killing, more than 8-fold increase compared to AlPcS4 alone. Together, integration of LbL of PS with Au NRs holds a significant promise for PDT therapeutic treatment of a variety of cancers.

Phthalocyanine photosensitizers as contrast agents for in vivo photoacoustic tumor imaging.

There is a need for contrast agents for non-invasive diagnostic imaging of tumors. Herein, Multispectral Optoacoustic Tomography (MSOT) was employed to evaluate phthalocyanines commonly used in photodynamic therapy as photoacoustic contrast agents. We studied the photoacoustic activity of three water-soluble phthalocyanine photosensitizers: phthalocyanine tetrasulfonic acid (PcS4), Zn(II) phthalocyanine tetrasulfonic acid (ZnPcS4) and Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) in phantom and in tumor-bearing mice to investigate the biodistribution and fate of the phthalocyanines in the biological tissues. PcS4 was observed to grant good contrast between the different reticuloendothelial organs and accumulate in the tumor within an hour of post-administration. ZnPcS4 and AlPcS4 offered little contrast in photoacoustic signals between the organs. PcS4 is a promising photoacoustic contrast agent and can be exploited as a photodiagnostic agent.

The photosensitized oxidation of mixture of parabens in aqueous solution.

The work presents results of studies on the photosensitized oxidation of mixture of five parabens (methyl-, ethyl-, propyl-, n-butyl-, and benzylparaben) in aqueous solution. Aluminum phthalocyanine chloride tetrasulfonic acid and xenon lamp simulating solar radiation were used as a photosensitizer and a light source, respectively. The purpose was to investigate the influence of inhibitory effect compounds present in the mixture on the reaction rate. The influence of the addition of second photosensitizer on the parabens degradation rate was investigated. The effect of additives: tert-butanol-hydroxyl radical scavenger and sodium azide-singlet oxygen scavenger on reaction course was also determined. The transformation products formed during the photosensitized oxidation process were analyzed by UPLC-MS/MS. The efficiency of photosensitized oxidation of parabens with natural sunlight irradiation in the central Poland was checked.

Stent bioactivo de titanio y óxido nítrico, ¿más seguro y eficaz que los stents farmacoactivos de segunda generación?

Photodynamic therapy (PDT) is a promising cancer treatment that can be implemented using various agents. The conventional photosensitizer Al (III) phthalocyanine chloride tetrasulfonic acid (Pc) has limitations of selectivity in tumor targeting, low affinity to cancer cells, and low two-photon absorption. This study presents a novel photosensitizer FA-TiO2-Pc, which has the TiO2 nanoparticle conjugated with a tumor targeting agent of folic acid (FA), and Pc. FA-TiO2-Pc possessed high targeted photodynamic therapeutic activity and excellent biocompatibility. This promising photosensitizer showed high therapeutic drug efficiency in vitro at a low concentration dose and short incubation time under one-photon excitation (OPE). In vivo, when treated with a low dose of FA-TiO2-Pc and low light irradiation, the tumor growth was depressed in mice bearing HeLa xenograft tumors with minimal side effects. In addition, the two-photon absorption of FA-TiO2-Pc was also enhanced compared to Pc, proving that FA-TiO2-Pc system has a great potential to be used for the therapy of the folate receptor positive cancer cells in both OPE-PDT and two-photon excitation (TPE)-PDT agents.

Singlet oxygen-sensitized delayed fluorescence of common water-soluble photosensitizers

Six common water-soluble singlet oxygen ((1)O2) photosensitizers - 5,10,15,20-tetrakis(1-methyl-4-pyridinio) porphine (TMPyP), meso-tetrakis(4-sulfonathophenyl)porphine (TPPS4), Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4), eosin Y, rose bengal, and methylene blue - were investigated in terms of their ability to produce delayed fluorescence (DF) in solutions at room temperature. All the photosensitizers dissolved in air-saturated phosphate buffered saline (PBS, pH 7.4) exhibit easily detectable DF, which can be nearly completely quenched by 10 mM NaN3, a specific (1)O2 quencher. The DF kinetics has a biexponential rise-decay character in a microsecond time domain. Therefore, we propose that singlet oxygen-sensitized delayed fluorescence (SOSDF), where the triplet state of a photosensitizer reacts with (1)O2 giving rise to an excited singlet state of the photosensitizer, is the prevailing mechanism. It was confirmed by additional evidence, such as a monoexponential decay of triplet-triplet transient absorption kinetics, dependence of SOSDF kinetics on oxygen concentration, absence of SOSDF in a nitrogen-saturated sample, or the effect of isotopic exchange H2O-D2O. Eosin Y and AlPcS4 show the largest SOSDF quantum yield among the selected photosensitizers, whereas rose bengal possesses the highest ratio of SOSDF intensity to prompt fluorescence intensity. The rate constant for the reaction of triplet state with (1)O2 giving rise to the excited singlet state of photosensitizer was estimated to be ~/>1 × 10(9) M(-1) s(-1). SOSDF kinetics contains information about both triplet and (1)O2 lifetimes and concentrations, which makes it a very useful alternative tool for monitoring photosensitizing and (1)O2 quenching processes, allowing its detection in the visible spectral region, utilizing the photosensitizer itself as a (1)O2 probe. Under our experimental conditions, SOSDF was up to three orders of magnitude more intense than the infrared (1)O2 phosphorescence and by far the most important pathway of DF. SOSDF was also detected in a suspension of 3T3 mouse fibroblast cells, which underlines the importance of SOSDF and its relevance for biological systems.

Monitoring oxygen concentration during photodynamic therapy using prompt photosensitizer fluorescence

A novel technique is described that uses either time-resolved or steady state prompt photosensitizer fluorescence to measure local oxygen concentration. Solution experiments conducted with Al(III) phthalocyanine chloride tetrasulfonic acid confirmed that the steady state fluorescence signal is dependent on the oxygen concentration and fluence rate. A relationship between prompt sensitizer fluorescence and sensitizer triplet quenching efficiency is derived which does not require knowledge of the Stern–Volmer constant. Similar relationships are also derived for sensitizer delayed fluorescence and phosphorescence. An explicit photodynamic therapy (PDT) dose metric that incorporates light dosimetry, sensitizer dosimetry, and triplet quenching efficiency is introduced. All components of this metric can be determined by optical measurements.

Ultrafast Dynamics of Metal Complexes of Tetrasulfonated Phthalocyanines at Biological Interfaces: Comparison between Photochemistry in Solutions, Films, and Noncancerous and Cancerous Human Breast Tissues

A promising material in medicine, electronics, opto-electronics, electrochemistry, catalysis, and photophysics, Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) is investigated at biological interfaces of human breast tissue by means of steady-state and time-resolved pump–probe spectroscopies: IR, Raman, UV–vis, fluorescence, and electronic transient absorption by pump–probe spectroscopy. Spectrally resolved pump–probe data were recorded on time scales ranging from femtoseconds to nanoseconds and give insight into molecular interactions and primary events in the interfacial region. The nature of these fast processes and pathways of the competing relaxation processes from the initially excited electronic states in AlPcS4 films and at biological interfaces of human breast cancerous and noncancerous tissues is studied. Comparison between photochemical dynamics in the biological environment of the human breast tissues and that occurring in aqueous solutions is presented. The excited-state absorptio...

Ultrafast dynamics and Raman imaging of metal complexes of tetrasulphonated phthalocyanines in human cancerous and noncancerous breast tissues

A promising material in medicine, electronics, optoelectronics, electrochemistry, catalysis and photophysics, Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) is investigated at biological interfaces of human breast tissue by means of time-resolved spectroscopy. The nature of fast processes and pathways of the competing relaxation mechanisms from the initially excited electronic states of a photosensitizer at biological interfaces have been studied. Comparison between the results in the biological environment of the breast tissues and in aqueous solutions demonstrates that the photochemical mechanisms become dramatically different. The presented results provide a basis for a substantial revision of the commonly accepted assumption that photochemistry of the bulk properties of photosensitizers in solutions can be translated to the interfacial region. First, in solution the dynamics of the photosensitizer is much slower than that at the biological interface. Second, the dynamics of the photosensitizer in the cancerous tissue is dramatically slower than that in noncancerous tissue. Our results provide evidence that molecular structures responsible for harvesting of the light energy in biological tissue find their ways for a recovery through some special features of the potential energy surfaces such as conical intersections, which facilitate the rate of radiationless transitions and maintain the photostability in the biological systems.

Effect of 1O2 quencher depletion on the efficiency of photodynamic therapy

Al(III) phthalocyanine chloride tetrasulfonic acid (AlPcS4) fluorescence and photodynamic oxygen consumption were monitored during AlPcS4-photodynamic therapy (PDT) of Mat LyLu cells in suspension. These measurements were used to calculate the PDT efficiency, which is defined as the oxygen consumption rate divided by the sensitizer concentration. As a function of the intracellular oxygen concentration consumed by PDT, the normalized PDT efficiency fell off more quickly at lower photosensitizer concentrations. The changes in PDT efficiency were compared to models of PDT in which the photosensitizer (PS) and singlet oxygen quencher (A) were either free to diffuse or were fixed. The model in which PS and A are free to diffuse did not agree with the experimental data because this model predicts that the reduction in PDT efficiency is independent of [PS]. A Monte Carlo model was written to simulate PDT when both PS and A are stationary. This model was found to describe the experimental data when the initial intracellular [A] = 90 mM and when the initial and final (i.e. after all A has been depleted) singlet oxygen lifetimes were 0.4 and 1.2 μs respectively.