Studies on preparation and photodynamic mechanism of chlorin P6-13,15-N-(cyclohexyl)cycloimide (Chlorin-H) and its antitumor effect for photodynamic therapy in vitro and in vivo

Recent advances in type I organic photosensitizers for efficient photodynamic therapy for overcoming tumor hypoxia

Photodynamic therapy (PDT) with an oxygen-dependent character is a noninvasive therapeutic method for cancer treatment. However, its clinical therapeutic effect is greatly restricted by tumor hypoxia. What's more, both PDT-mediated oxygen consumption and microvascular damage aggravate tumor hypoxia, thus, further impeding therapeutic outcomes. Compared to type II PDT with high oxygen dependence and high oxygen consumption, type I PDT with less oxygen consumption exhibits great potential to overcome the vicious hypoxic plight in solid tumors. Type I photosensitizers (PSs) are significantly important for determining the therapeutic efficacy of PDT, which performs an electron transfer photochemical reaction with the surrounding oxygen/substrates to generate highly cytotoxic free radicals such as superoxide radicals (˙O₂^-) as type I ROS. In particular, the primary precursor (˙O₂^-) would progressively undergo a superoxide dismutase (SOD)-mediated disproportionation reaction and a Haber-Weiss/Fenton reaction, yielding higher cytotoxic species (˙OH) with better anticancer effects. As a result, developing high-performance type I PSs to treat hypoxic tumors has become more and more important and urgent. Herein, the latest progress of organic type I PSs (such as AIE-active cationic/neutral PSs, cationic/neutral PSs, polymer-based PSs and supramolecular self-assembled PSs) for monotherapy or synergistic therapeutic modalities is summarized. The molecular design principles and strategies (donor-acceptor system, anion-π⁺ incorporation, polymerization and cationization) are highlighted. Furthermore, the future challenges and prospects of type I PSs in hypoxia-overcoming PDT are proposed.

Conjugates of Tetrapyrrolic Macrocycles as Potential Anticancer Target-Oriented Photosensitizers

Photodynamic therapy is a minimally invasive treatment of tumors using photosensitizers, light, and reactive oxygen species, which can destroy cellular structures. With the development of photodynamic therapy, significant efforts have been made to create new efficient photosensitizers with improved delivery to cells, stability, and selectivity against cancer tissues. Naturally occurring tetrapyrrolic macrocycles, such as porphyrins and chlorins, are very attractive as photosensitizers, and their structural modification and conjugation with other biologically active molecules are promising approaches for creating new photosensitizers specifically targeting cancer cells. The present review aims to highlight recent developments in the design, preparation, and investigation of complex conjugates of tetrapyrrolic macrocycles, which can potentially be used as sensitizers for target-oriented photodynamic therapy of cancer. In this review, we discuss the structure, photodynamic effect, and anticancer activity of the following conjugates of tetrapyrrolic macrocycles: (1) conjugates obtained by modifying peripheral substituents in porphyrins and chlorins; (2) conjugates of porphyrins and chlorins with lipids, carbohydrates, steroids, and peptides; (3) conjugates of porphyrins and chlorins with anticancer drugs and some other biologically active molecules; (4) metal-containing conjugates. The question of how the conjugate structure affects its specificity, internalization, localization, and photoinduced toxicity within cancer cells is the focus of this review.

Synthesis and evaluation of novel chlorophyll a derivatives as potent photosensitizers for photodynamic therapy

Chlorophyll a exhibits excellent photosensitive activity in photosynthesis. The unstability limited its application as photoensitizer drug in photodynamic therapy. Here a series of novel chlorophyll a degradation products pyropheophorbide-a derivatives were synthesized and evaluated for lung cancer in PDT. These compounds have strong absorption in 660-670 nm with high molar extinction coefficient, and fluorescence emission in 660-675 nm upon excitation with 410-415 nm light. They all have much higher ROS yields than pyropheophorbide-a, and compound 10 was even higher than [3-(1-hexyloxyethyl)]-pyrophoeophorbide a (HPPH). Distinctive phototoxicity was observed in vitro and the inhibition effect was in light dose-dependent and drug dose-dependent style. They can effectively inhibit the growth of lung tumor in vivo. Among them, compound 8 and 11 have outstanding photodynamic anti-tumor effects without obvious skin photo-toxicity, so they can act as new drug candidates for photodynamic therapy.

Preparation of a chlorophyll derivative and investigation of its photodynamic activities against cholangiocarcinoma

Photodynamic therapy (PDT) is emerging as a promising method for the treatment of various cancer diseases. However, the clinical application of PDT is limited due to the lack of effective photosensitizers. In this study, a novel chlorophyll derivative, N,N-bis(2-carboxyethyl)pyropheophorbide a (BPPA), had been synthesized and characterized. BPPA had a characteristic long wavelength absorption peak at 669nm and a singlet oxygen quantum yield of 0.54. To investigate the photodynamic ability of BPPA against cholangiocarcinoma (CCA), cellular uptake, subcellular location and bio-distribution, in vitro and in vivo PDT efficacy of BPPA were studied. The results showed that BPPA could rapidly accumulate in QBC-939 cells and localize in the cytoplasm. BPPA- PDT was effective in reducing the cell viability in a drug dose- and light dose-dependent manner in vitro. In CCA xenograft nude mouse model, the concentration of BPPA in the plasma lowered rapidly, and the fluorescence signal peaked at 0.5h and 2h after injection in the skin and tumor, respectively. Significant quantities could be observed in the tumor. BPPA followed by irradiation could significantly inhibit growth of tumors, and histological examination revealed necrotic damage in PDT-treated tumors. These results suggested that BPPA could be a promising drug candidate for photodynamic therapy in cholangiocarcinoma.

Applications of functionalized nanomaterials in photodynamic therapy

Specially designed functionalized nanomaterials such as superparamagnetic iron oxide, gold, quantum dots and up- and down-conversion lanthanide series nanoparticles have consistently and completely revolutionized the biomedical environment over the past few years due to their specially inferring properties, such as specific drug delivery, plasmonic effect, optical and imaging properties, therapeutic thermal energy productionand excellent irresistible cellular penetration. These properties have been used to improve many existing disease treatment modalities and have led to the development of better therapeutic approaches for the advancement of the treatment of critical human diseases, such as cancers and related malaise. In photodynamic therapy, for example, where the delivery of therapeutic agents should ideally avoid toxicity on nearby healthy cells, superparamagnetic iron oxide nanoparticles have been shown to be capable of making photodynamic therapy (PDT) prodrugs and their associative targeting moieties tumor-specific via their unique response to an external magnetic fields. In this review, the nanomaterials commonly employed for the enhancement of photodynamic therapy are discussed. The review further describes the various methods of synthesis and characterization of these nanomaterials and highlights challenges for improving the efficacy of PDT in the future.

Molecular analysis of apoptosis pathway after photodynamic therapy in breast cancer: Animal model study

BACKGROUND

Molecular investigation of breast tumors has permitted better understanding about interaction of genes and pathways involved in tumor progression.

OBJECTIVE

The aim of this study was to evaluate the association between genes belonging to the pathway of apoptosis with tumor response to photodynamic therapy.

STUDY DESIGN/MATERIALS AND METHODS

The mammary tumors were induced in twenty-four Spraguey-Dawley female rats by oral gavage of 7,12-dimethylbenz(a)anthracene (8mg/Kg body weight). Animals were divided into three groups: G1 (normal tissue), G2 (tumors without treatment), G3 (animals euthanized 48h after treatment). The photosensitizer used was a chlorin, 5,15-bis-(2-bromo-5-hydroxyphenyl) chlorin in the dose of 8mg/kg for each animal. Light source of diode laser at a wavelength of 660nm, fluence rate of 100mW/cm, and light dose of 100J/cm was delivery to lesions for treatment. A sample from each animal was investigated by quantitative real time PCR using Rat Apoptosis RT(2) Profiler™ PCR Array platform.

RESULTS

Pro-apoptotic BAK1, CARD6, CASP8, CIDEA, CIDEB, DAPK1, TNF, TNFRSF10B, FASLG, LOC687813, and TP73 genes showed increased expression, and CD40 anti-apoptotic gene showed decreased expression in the group who underwent PDT (G3) in relation to G2.

CONCLUSION

The results indicated that these genes are involved more directly with cellular apoptosis induced by PDT using the Chlorin photosensitizer.

Biomedical applications of nano-titania in theranostics and photodynamic therapy

Titanium dioxide (TiO₂) is one of the most abundantly used nanomaterials for human life. It is used in sunscreen, photovoltaic devices, biomedical applications and as a food additive and environmental scavenger.

Photodynamic therapy with a novel porphyrin-based photosensitizer against human gastric cancer

The objective of the present study was to evaluate the effects of novel porphyrin-based photosensitizer meso-5-[ρ-diethylene triamine pentaacetic acid- aminophenyl]-10,15,20-triphenyl-porphyrin (DTP)-mediated photodynamic therapy (PDT) on the HGC27 and SNU-1 human gastric cancer cell lines. The absorption spectrum of DTP was analyzed using a microplate spectrophotometer. The HGC27 or SNU-1 cells were incubated with DTP and exposed to illumination by a 650-nm laser. The experiments were divided into four groups: A blank control, cells treated with DTP without light, cells exposed to laser light without DTP and cells treated with a combination of DTP and light together. The phototoxicity of DTP was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Cell apoptosis was detected by flow cytometry and Hoechst 33342 staining. In addition, the intracellular distribution of DTP was investigated by laser scanning confocal microscopy. DTP-PDT demonstrated marked phototoxicity towards HGC27- and SNU-1 cells. The rate of cell death increased significantly in a DTP concentration-dependent and light dose-dependent manner, with maximum mortality rates of 74.14 and 67.76%, respectively. There were significant differences between the therapeutic and control groups (P<0.01). In addition, the growth of cells treated with DTP or laser light alone was not inhibited. Further evaluation revealed that, following DTP-PDT, HGC27 and SNU-1 cells demonstrated notable apoptotic changes, including condensed chromatin, fragmented nuclei and apoptotic bodies, and the percentage of apoptotic cells was significantly higher than that of the control groups (P<0.01). Furthermore, confocal laser scanning microscopy revealed that DTP localized to the lysosomes but not mitochondria in the two types of tumor cell. In conclusion, significant phototoxicity and reduced cytotoxicity in dark conditions make the novel photosensitizer DTP a promising potential PDT drug for future use in the treatment of human gastric cancer.

Antitumor effects evaluation of a novel porphyrin derivative in photodynamic therapy

In this paper, the antitumor activity of a novel porphyrin-based photosensitizer 5,10,15,20-tetrakis[(5-diethylamino)pentyl] porphyrin (TDPP) was reported in vitro and in vivo. The photophysical and cellular properties of TDPP were investigated. The singlet oxygen generation quantum yield of TDPP was detected; it showed a high singlet oxygen quantum yield of 0.52. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The efficiency of TDPP-photodynamic therapy (PDT) in vitro was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and in situ trypan blue exclusion test. Treated with a 630-nm laser, TDPP can kill cultured human esophageal cancer cell line (Eca-109) cells and reduce the growth of Eca-109 xenograft tumors significantly in BABL/c nude mice. And histopathological study was also used to confirm the antitumor effect. It has the perspective to be developed as a new antitumor drug in photodynamic therapy and deserves further investigation.

Evaluation of a bacteriochlorin-based photosensitizer's anti-tumor effect in vitro and in vivo

PURPOSE

Bacteriochlorin derivatives are promising photosensitive agents for photodynamic therapy (PDT) of tumors. In the current study, the photodynamic activity of a novel bacteriochlorin derivative, cis-2, 3, 12, 13-tetracarboxymethyl-5, 10, 15, 20-tetraphenyl bacteriochlorin (TCTB), was evaluated both in vitro and in vivo.

METHODS

Physicochemical characteristics of the novel photosensitizer were measured. The efficiency of TCTB-PDT in vitro was analyzed by MTT assay, clonogenic assay and in situ trypan blue exclusion test. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The accumulation of TCTB in human malignant tumor cells was measured by fluorescence spectrometer, and the pathway of cell death was analyzed by flow cytometry. S180 tumor model was used to evaluate the anti-tumor effects of TCTB-PDT. And histopathological study was also used to confirm the anti-tumor effect.

RESULTS

TCTB shows a singlet oxygen quantum yield of 0.56 and displays a characteristic long wavelength absorption peak at 732 nm. The accumulation of TCTB increased in time-dependent manner, and it was found in cytoplasm and nuclear membranes. In vitro PDT using TCTB and Nd:YAG laser showed drug concentration-, laser dose-dependent cytotoxicity to human esophageal cancer Eca-109 cells. In mice bearing osteosarcoma S180 tumors, the combined use of 10 mg/kg TCTB and 120 J/cm(2) showed superior anti-tumor activity. Histology examination of tumor tissues revealed that PDT using TCTB and the Nd:YAG laser induced tumor cells shrunken and necrotic.

CONCLUSION

In in vitro and in vivo studies, we found that TCTB has excellent anti-tumor effect. It suggests that TCTB is a potential photosensitizer of PDT for cancer.

In vitro and in vivo antitumor activity of a novel porphyrin-based photosensitizer for photodynamic therapy

PURPOSE

Photodynamic therapy (PDT) is a promising treatment in cancer therapy, based on the use of a photosensitizer activated by visible light in the presence of oxygen. Nowadays significant research efforts have been focused on finding a new photosensitizer. In the present paper, the antitumor effects of a novel porphyrin-based photosensitizer, {Carboxymethyl-[2-(carboxymethyl-{[4-(10,15,20-triphenylporphyrin-5-yl)-phenylcarbamoyl]-methyl}-amino)-ethyl]-amino}-acetic acid (ATPP-EDTA) on two types of human malignant tumor cells in vitro and a gastric cancer model in nude mice, were evaluated.

METHODS

The PDT efficacy with ATPP-EDTA in vitro was assessed by MTT assay. The intracellular accumulation was detected with fluorescence spectrometer, and the intracellular distribution was determined by laser scanning confocal microscopy. The mode of cell death was investigated by Hoechst 33342 staining and flow cytometer. BGC823-derived xenograft tumor model was established to explore the in vivo antitumor effects of ATPP-EDTA.

RESULTS

ATPP-EDTA exhibited intense phototoxicity on both cell lines in vitro in concentration- and light dose-dependent manners meanwhile imposing minimal dark cytotoxicity. The accumulation of ATPP-EDTA in two malignant cell lines was time-dependent and prior compared to normal cells. It was mainly localized at lysosomes, but induced cell death by apoptotic pathway. ATPP-EDTA significantly inhibited the growth of BGC823 tumors in nude mice (160 mW/cm(2), 100 J/cm(2)).

CONCLUSIONS

Present studies suggest that ATPP-EDTA is an effective photosensitizer for PDT to tumors. It distributed in lysosomes and caused cell apoptosis. ATPP-EDTA, as a novel photosensitizer, has a great potential for human gastric cancer treatment in PDT and deserves further investigations.

Vacata- and divacataporphyrin: new photosensitizers for application in photodynamic therapy-an in vitro study

BACKGROUND AND OBJECTIVE

The photodynamic therapy is a well-known method of treatment of both malignant tumors and non-tumor lesions in human patients. In the present study, we aimed at evaluating the in vitro efficacy of the new photosensitizing agents, vacataporphyrin (VP), and divacataporphyrin (DVP).

MATERIALS AND METHODS

The effectiveness of VP and DVP was compared to well-known photosensitizers, that is, hematoporphyrin derivative (HPD) and chlorin e6 (Ce6) in identical in vitro conditions. The experiment was performed on a well-established breast cancer cell line, MCF-7 and compared to HCV 29T11-2-D1 cell line. Cells were incubated in standard conditions and they were exposed to different concentrations of VP, DVP, HPD, and Ce6, that is, 180, 90, 45, 22.5, and 10 µg/ml. After incubation with photosensitizers, the cells were washed, medium was exchanged and the cells were subjected to irradiation at the proper wavelengths, light intensity (100 mW/sq cm), and total light doses 4.5 and 9 J/sq cm.

RESULTS

Our results showed that the VP and DVP are potent photosensitizers and the photocytotoxic effect after the incubation with DVP was much better than that of VP. The cytotoxic effects of VP and DVP were less intensive than these of HPD and Ce6. VP and DVP also accumulated well in the tumor cells. Our results also indicated that the VP and DVP effectiveness on MCF-7 cells was photosensitizer dose and light dose dependent.

CONCLUSION

The overall properties revealed by both new porphyrins and particularly a possibility for excitation at a higher wavelength and thus a deeper tissue penetration, make them promising candidates for further in vivo experiments.

Preparation of photosensitizer-loaded PLLA nanofibers and its anti-tumor effect for photodynamic therapy in vitro

Photodynamic therapy (PDT) is a promising new treatment for cancer that has been recently accepted clinically. PDT is based on the administration of tumor-localizing photosensitizers (PSs), followed by exposing the neoplastic area to the light absorbed by the PS. In this article, a novel anticancer nanofiber membrane containing purpurin-18 (0.1%) was successfully prepared. The thickness of membrane was 0.028 mm, and the average fiber diameter was around 357 nm by scanning electron microscope (SEM). It was indicated that purpurin-18 possessed excellent compatibility with PLLA from FTIR spectrum. The physical properties of fiber membrane were also characterized by Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD). Cell morphology and the interaction between cells and nanofibers were studied by SEM. The results showed that both SMMC 7721 and ECA109 cells can adhere and spread on the surface of the polymer nanofiber, and both cells can interact and integrate well with the surrounding fibers. The efficacy of PDT was determined by MTT assays. The results showed that the cells were killed immediately after PDT and purpurin-18 had no different efficacy to different cancer cell lines. In summary, the PS-loaded PLLA nanofibers were prepared successfully, and the SMMC 7721 and ECA109 cells could be inhibited and killed through photodynamic therapy.

Enhanced tumor localization and retention of chlorin e6 in cationic nanolipoplexes potentiate the tumor ablation effects of photodynamic therapy

Here we report the tumor ablation effects of the negatively charged photosensitizer chlorin e6 (Ce6) in nanocomplexes. Ce6 was complexed to cationic 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine-based liposomes, forming cationic nanolipoplexes. The loading efficiency of Ce6 to cationic nanolipoplexes was greater than 90%. The degree of enhancement of cellular uptake of Ce6 by treatment in cationic nanolipoplexes increased with the concentration of Ce6, showing 18.3-fold higher uptake than free Ce6 at 15 µM. Molecular imaging revealed the preferential distribution and retention of Ce6 in SCC7 tumor tissues after intravenous administration of Ce6 in cationic nanolipoplexes. Moreover, localized illumination of mice receiving Ce6 in cationic nanolipoplexes resulted in the formation of thick scabs over tumor regions, and complete ablation of tumors after scab detachment. In contrast, continuous growth of tumors was observed in the group treated with free Ce6. Our results suggest that the cationic nanolipoplexes of Ce6 improve the therapeutic effects of photodynamic cancer therapy as compared to free Ce6.