Effect of Photosensitizer Delivery System and Irradiation Parameters on the Efficiency of Photodynamic Therapy of B16 Pigmented Melanoma in Mice

Abstract— Previous studies (Biolo et al., Photochem. Photobiol. 59, 362-365, 1994) showed that liposome-delivered Si(IV)-na-phthalocyanine (SiNc) photosensitizes B16 pigmented melanoma subcutaneously transplanted in C57 mice to the action of 776 nm light. However, the efficacy of the phototreatment was limited by a lack of selectivity of tumor targeting by SiNc as well as by incomplete necrosis of the neoplastic mass. The present investigations show that the use of a different delivery system (Cremophor emulsion vs liposomes of dipalmitoylphosphatidylcholine) causes no significant increase in the selectivity of tumor targeting for three injected doses of SiNc (0.5, 1, 2 mg/kg). However, upon 776 nm light irradiation (300 mW/cm²; 520 J/cm²), the delay in the rate of tumor growth was maximal (7-8 days) for the highest naphthalocyanine dose. On the other hand, a remarkable improvement in the tumor response was obtained by inducing an intratumoral temperature increase to 44°C immediately after PDT. The thermal effect appeared to be due to photoexcitation of melanin by 776 nm light (550 mW/cm²; 520 J/cm²) and subsequent partial conversion of absorbed energy into heat.     

1064nm激光诱导Ge(111)与Cl2反应动力学

采用超声分子束和时间分辨质谱技术研究了1064nm脉冲激光辐照下Ge(111)与Cl₂的反应动力学。实验结果表明,该反应的主要产物为GeCl₂,提高入射氯分子的平动能将增加反应速率。激光能量密度对GeCl₂产率呈指数关系,而对GeCl₂的平动温度影响不大。升高Ge(111)表面温度也能提高反应产率。同时还讨论了近红外激光诱导GeCl₂反应的机理。     

Fluorescence and Treatment Light Monitoring for Interstitial Photodynamic Therapy

In interstitial photodynamic therapy, light is distributed to the tumor via light diffusers. The light dose and the related phototoxic effect achieved throughout the target volume critically depend on absorption, scattering and diffuser positioning. Using liquid tissue phantoms, we investigated the dependencies of treatment light transmission and protoporphyrin IX (PpIX) fluorescence on these parameters. This enabled monitoring hemoglobin oxygenation and methemoglobin formation during irradiation (635 nm, 200 mW cm⁻¹ diffuser length). Starting with two parallel cylindrical diffusers at 10 mm radial separation, the light transmitted between the fibers was largely determined by the minimal distance between the diffusers, but rather insensitive to an additional axial displacement or tilting of one fiber with respect to the other. For fixed distance between the diffusor centers, however, tilting up to direct contact resulted in a 10-fold signal increase. For hemoglobin within erythrocytes, irradiation leads to photobleaching of PpIX without marked change in hemoglobin oxygenation until hemolysis occurs. Afterward, hemoglobin is rapidly deoxygenized and methemoglobin is formed, leading to a dramatic increase in absorption. For lysed blood, these effects start immediately. A comparison of intraoperative monitoring of the signals with the experimental results might help prevent insufficient treatment by reconsidering treatment planning or prolonging irradiation.     

Rapid Initiation of Apoptosis by Photodynamic Therapy

Abstract— Photodynamic therapy (PDT) of neoplastic cell lines is sometimes associated with the rapid initiation of apoptosis, a mode of cell death that results in a distinct pattern of cellular and DNA fragmentation. The apoptotic response appears to be a function of both the sensitizer and the cell line. In this study, we examined photodynamic effects of several photosensitizers on murine leukemia P388 cells. Two drugs, a porphycene dimer (PcD) and tin etiopurpurin (SnET2), which localized at lysosomal sites, were tested at PDT doses that resulted in 50% loss of viability (LD₅₀), measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. An oligonucleosomal pattern of DNA degradation was observed within 1 h after irradiation. Neither sensitizer antagonized PDT-mediated internucleosomal DNA cleavage by the other. Very high PDT doses with either agent abolished this rapid internucleosomal cleavage. Exposure of cells to high concentrations of either sensitizer in the dark also resulted in rapid DNA fragmentation to nucle-osomes and nucleosome multimers; this effect was not altered by the antioxidant 6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid (trolox), although the latter could protect cells from cytotoxicity and apoptotic effects caused by LD₅₀ PDT doses. Photodamage from two cat-ionic sensitizers, which localized at membrane sites, caused rapid DNA cleavage to 50 kb particles; however, no further fragmentation was detected after 1 h under LD₁₀, LD₅₀ or LD₉₅ PDT conditions. Moreover, the presence of either cationic sensitizer inhibited the rapid internucleosomal cleavage induced by SnET2 or PcD photodamage. The site of photodynamic action may therefore be a major determinant of the initiation and rate of progression of apoptosis.     

Metronomic Photodynamic Therapy as a New Paradigm for Photodynamic Therapy: Rationale and Preclinical Evaluation of Technical Feasibility for Treating Malignant Brain Tumors¶

The concept of metronomic photodynamic therapy (mPDT) is presented, in which both the photosensitizer and light are delivered continuously at low rates for extended periods of time to increase selective tumor cell kill through apoptosis. The focus of the present preclinical study is on mPDT treatment of malignant brain tumors, in which selectivity tumor cell killing versus damage to normal brain is critical. Previous studies have shown that low‐dose PDT using 5‐aminolevulinic acid (ALA)‐induced protoporphyrin IX(PpIX) can induce apoptosis in tumor cells without causing necrosis in either tumor or normal brain tissue or apoptosis in the latter. On the basis of the levels of apoptosis achieved and model calculations of brain tumor growth rates, metronomic delivery or multiple PDT treatments, such as hyperfractionation, are likely required to produce enough tumor cell kill to be an effective therapy. In vitro studies confirm that ALA‐mPDT induces a higher incidence of apoptotic (terminal deoxynucleotidyl transferase‐mediated 2′‐deoxyuridine 5′‐triphosphate, sodium salt nick‐end labeling positive) cells as compared with an acute, high‐dose regimen (ALA‐αPDT). In vivo, mPDT poses two substantial technical challenges: extended delivery of ALA and implantation of devices for extended light delivery while allowing unencumbered movement. In rat models, ALA administration via the drinking water has been accomplished at very high doses (up to 10 times therapeutic dose) for up to 10 days, and ex vivo spectro‐fluorimetry of tumor (9L gliosarcoma) and normal brain demonstrates a 3–4 fold increase in the tumor‐to‐brain ratio of PpIX concentration, without evidence of toxicity. After mPDT treatment, histological staining reveals extensive apoptosis within the tumor periphery and surrounding microinvading colonies that is not evident in normal brain or tumor before treatment. Prototype light sources and delivery devices were found to be practical, either using a laser diode or light‐emitting diode (LED) coupled to an implanted optical fiber in the rat model or a directly implanted LED using a rabbit model. The combined delivery of both drug and light during an extended period, without compromising survival of the animals, is demonstrated. Preliminary evidence of selective apoptosis of tumor under these conditions is presented.     

Delayed Oxidative Photodamage induced by Photodynamic Therapy

Abstract— Apoptotic DNA fragmentation was observed 60 min after photodynamic therapy of murine leukemia cells in culture, using either of two photosensitizers with predominantly lysosomal targets. When the radical scavengers trolox or α-tocopherol succinate were present during irradiation, the subsequent appearance of apoptotic cells was prevented, as was phototoxicity. Addition of either scavenger during the 60 min after irradiation provided only partial protection from apoptosis and phototoxicity; this protection was abolished if the addition was delayed for 10 min. These results are consistent with a model whereby long-persisting photoproducts continue the initiation of apoptosis for approximately 10 min after irradiation has ceased.     

Hiporfin‐Mediated Photodynamic Therapy in Preclinical Treatment of Osteosarcoma

This study was carried out to investigate the anti‐tumor effect and mechanism of hiporfin‐mediated photodynamic therapy (hiporfin‐PDT) in osteosarcoma. We found that hiporfin accumulated mainly in the cytoplasm of osteosarcoma cells in a time and concentration‐dependent manner. Hiporfin‐PDT inhibited the proliferation, induced apoptosis and produced cell cycle arrest at G2M in osteosarcoma cell lines. Hiporfin‐PDT increased the expression of cleaved‐caspase‐3, cleaved PARP‐1, Bax and RIP1 while it decreased the expression of Bcl‐2; in addition, low concentration of hiporfin increased LC3 conversion. Furthermore, cell death caused by hiporfin‐PDT could be rescued by Nec‐1 but not by Z‐VAD‐FMK. Production of reactive oxygen species was increased after hiporfin‐PDT. In vivo studies showed a significant decrease in tumor volume and weight after hiporfin‐PDT in all three tumor mouse models investigated (subcutaneous and orthotopic). Histological analysis showed widespread cell apoptosis and necrosis after treatment. Immunohistochemistry also showed upregulation of cleaved‐caspase‐3 and downregulation of Bcl‐2 after hiporfin‐PDT. These results indicate that hiporfin‐PDT exhibits a killing effect in osteosarcoma both in vitro and in vivo, which is associated with apoptosis and necroptosis, while autophagy plays a protective role. All these findings shed light on a potential future clinical use for hiporfin in the treatment of osteosarcoma.     

The Raman spectroscopy of cement minerals under 1064 nm excitation

The prospects for near-IR-excited Raman scattering from cement minerals are discussed, and a very unusual result concerning the intensity of the spectra is presented.     

Therapeutic Enhancement of Verteporfin-mediated Photodynamic Therapy by mTOR Inhibitors

Photodynamic therapy (PDT) with photosensitizer verteporfin is a clinically approved vascular disrupting modality that is currently in clinical trial for cancer treatment. In this study, we evaluated PDT in combination with either mTORC1 inhibitor rapamycin or mTORC1/C2 dual inhibitor AZD2014 for therapeutic enhancement in SVEC endothelial cells. Verteporfin-PDT alone induced cell apoptosis by activating the intrinsic apoptotic pathway. However, it increased the expression of anti-apoptotic protein MCL-1 and the phosphorylation of S6, a downstream molecule of mTOR signaling. In contrast, mTOR inhibitors rapamycin and AZD2014 did not induce apoptosis in SVEC cells. They suppressed MCL-1 expression and S6 phosphorylation and imposed a potent inhibition on cell proliferation. PDT in combination with mTOR inhibitors activated the intrinsic apoptotic pathway and resulted in increased apoptosis. Combination treatments also led to sustained inhibition of cell proliferation. Although AZD2014 was more effective for cell growth inhibition and PDT enhancement than rapamycin at the higher concentrations examined in the study, both inhibitors effectively enhanced PDT response, suggesting that inhibition of mTORC1 is crucial for PDT enhancement. Our results indicate that mTOR inhibitors mechanistically cooperate with PDT for enhanced cell death and sustained growth inhibition, supporting a combination approach for therapeutic enhancement.     

Deletion of Alloantigen-Activated Cells by Aminolevulinic Acid-Based Photodynamic Therapy

Protoporphyrin IX (PpIX), an endogenously synthesized photosensitizer, can transiently accumulate in activated lymphocytes following administration of the heme precursor 5-aminolevulinic acid (ALA). One possible mechanism of this in lymphocyte accumulation is that actively dividing cells use intracellular iron stores for cytochrome and DNA synthesis and thus do not inactivate PpIX, the photoactive precursor of heme, by iron incorporation. This selective accumulation in activated cells should allow targeting by photodynamic therapy (PDT). To determine the effect of this accumulation, we studied PDT effects on the in vitro correlate of transplantation rejection: the one-way mixed lymphocyte reaction (MLR). Selective phototoxicity was determined by photoirradiating ALA-treated, MLR-activated cells and measuring subsequent stimulation either in a secondary MLR or with phytohemagglutinin (PHA). We found that proliferation of MLR-activated lymphocytes incubated with ALA and treated with light was only 12-20% of controls (ALA+, no light) after rechallenge with the stimulator cells (P < 0.05), although their response to nonspecific PHA stimulation was similar to controls. Thus alloantigen-specific depletion was shown. The data suggest a role for ALA-PDT in the treatment of diseases that require the selective elimination of activated lymphocytes and possibly as an immunomodulator.     

Metal Nanoparticles for Photodynamic Therapy: A Potential Treatment for Breast Cancer

Breast cancer (BC) is the most common malignant tumor in women worldwide, which seriously threatens women’s physical and mental health. In recent years, photodynamic therapy (PDT) has shown significant advantages in cancer treatment. PDT involves activating photosensitizers with appropriate wavelengths of light, producing transient levels of reactive oxygen species (ROS). Compared with free photosensitizers, the use of nanoparticles in PDT shows great advantages in terms of solubility, early degradation, and biodistribution, as well as more effective intercellular penetration and targeted cancer cell uptake. Under the current circumstances, researchers have made promising efforts to develop nanocarrier photosensitizers. Reasonably designed photosensitizer (PS) nanoparticles can be achieved through non-covalent (self-aggregation, interfacial deposition, interfacial polymerization or core-shell embedding and physical adsorption) or covalent (chemical immobilization or coupling) processes and accumulate in certain tumors through passive and/or active targeting. These PS loading methods provide chemical and physical stability to the PS payload. Among nanoparticles, metal nanoparticles have the advantages of high stability, adjustable size, optical properties, and easy surface functionalization, making them more biocompatible in biological applications. In this review, we summarize the current development and application status of photodynamic therapy for breast cancer, especially the latest developments in the application of metal nanocarriers in breast cancer PDT, and highlight some of the recent synergistic therapies, hopefully providing an accessible overview of the current knowledge that may act as a basis for new ideas or systematic evaluations of already promising results.     

Enhancement of Photodynamic Cancer Therapy by Physical and Chemical Factors

The viable use of photodynamic therapy (PDT) in cancer therapy has never been fully realized because of its undesirable effects on healthy tissues. Herein we summarize some physicochemical factors that can make PDT a more viable and effective option to provide future oncological patients with better‐quality treatment options. These physicochemical factors include light sources, photosensitizer (PS) carriers, microwaves, electric fields, magnetic fields, and ultrasound. This Review is meant to provide current information pertaining to PDT use, including a discussion of in vitro and in vivo studies. Emphasis is placed on the physicochemical factors and their potential benefits in overcoming the difficulty in transitioning PDT into the medical field. Many advanced techniques, such as employing X‐rays as a light source, using nanoparticle‐loaded stem cells and bacteriophage bio‐nanowires as a photosensitizer carrier, as well as integration with immunotherapy, are among the future directions.     

Exploitation of Immune Response-eliciting Properties of Hypocrellin Photosensitizer SL052-based Photodynamic Therapy for Eradication of Malignant Tumors

A diaminophenyl derivative of hypocrellin B (SL052) has been developed as a photosensitizer for use in photodynamic therapy (PDT) of solid tumors. Testing SL052-PDT on mouse carcinoma and fibrosarcoma models revealed a typical response seen with clinically established photosensitizers featuring initial rapid tumor ablation with ensuing recurrence at rates dependent on photosensitizer/light doses. Elevated numbers of immune cells were found in lymph nodes draining SCCVII mouse squamous cell carcinomas treated by SL052-PDT (in particular T cells), and the accumulation of degranulating cytotoxic T cells was detected at the tumor-treated site. This indicates that a significant contribution to tumor cures is elicited by an antitumor adaptive immune response. Two different immunotherapy agents, γ-interferon and antibody blocking inhibitory FcγRIIB receptor, were both found to be highly effective in potentiating the curative effect of SL052-PDT with SCCVII tumors. Combining SL052-PDT with FcγRIIB-blocking antibody treatment caused a further increase in the number of cells in tumor-draining lymph nodes and in degranulating CD8⁺ cells, suggesting the amplification of the immune response induced by PDT. Vaccines consisting of SCCVII cells treated with SL052-PDT in vitro were effective in reducing growth of established subcutaneous SCCVII tumors. In conclusion, PDT mediated by SL052 is suitable to be integrated with various immunotherapy protocols.     

Photosynthetic Tumor Oxygenation by Photosensitizer-Containing Cyanobacteria for Enhanced Photodynamic Therapy

Sustained tumor oxygenation is of critical importance during type-II photodynamic therapy (PDT), which depends on the intratumoral oxygen level for the generation of reactive oxygen species. Herein, the modification of photosynthetic cyanobacteria with the photosensitizer chlorin e6 (ce6) to form ce6-integrated photosensitive cells, termed ceCyan, is reported. Upon 660 nm laser irradiation, sustained photosynthetic O₂ evolution by the cyanobacteria and the immediate generation of reactive singlet oxygen species (¹O₂) by the integrated photosensitizer could be almost simultaneously achieved for tumor therapy using type-II PDT both in vitro and in vivo. This work contributes a conceptual while practical paradigm for biocompatible and effective PDT using hybrid microorganisms, displaying a bright future in clinical PDT by microbiotic nanomedicine.     

1064 nm dispersive multichannel Raman spectroscopy for the analysis of plant lignin

The mixed phenylpropanoid polymer lignin is one of the most abundant biopolymers on the planet and is used in the paper, pulp and biorenewable industries. For many downstream applications, the lignin monomeric composition is required, but traditional methods for performing this analysis do not necessarily represent the lignin composition as it existed in the plant. Herein, it is shown that Raman spectroscopy can be used to measure the lignin monomer composition. The use of 1064 nm excitation is needed for lignin analyses since high fluorescence backgrounds are measured at wavelengths as long as 785 nm. The instrument used for these measurements is a 1064 nm dispersive multichannel Raman spectrometer that is suitable for applications outside of the laboratory, for example in-field or in-line analyses and using remote sensing fiber optics. This spectrometer has the capability of acquiring toluene/acetonitrile spectra with 800 cm⁻¹ spectral coverage, 6.5 cm⁻¹ spectral resolution and 54 S/N ratio in 10 s using 280 mW incident laser powers. The 1135–1350 cm⁻¹ and 1560–1650 cm⁻¹ regions of the lignin spectrum can be used to distinguish among the three primary model lignin monomers: coumaric, ferulic and sinapic acids. Mixtures of the three model monomers and first derivative spectra or partial least squares analysis of the phenyl ring breathing modes around 1600 cm⁻¹ are used to determine sugarcane lignin monomer composition. Lignin extracted from sugarcane is shown to have a predominant dimethoxylated and monomethoxylated phenylpropanoid content with a lesser amount of non-methoxylated phenol, which is consistent with sugarcane's classification as a non-woody angiosperm. The location of the phenyl ring breathing mode peaks do not shift in ethanol, methanol, isopropanol, 1,4 dioxane or acetone.     

A Novel Prospective Study Assessing the Combination of Photodynamic Therapy and Proton Radiation Therapy: Safety and Outcomes When Treating Malignant Pleural Mesothelioma

Malignant pleural mesothelioma remains difficult to treat, with high failure rates despite optimal therapy. We present a novel prospective trial combining proton therapy (PT) and photodynamic therapy (PDT) and the largest‐ever mesothelioma PT experience (n = 10). PDT photosensitizers included porfimer sodium (2 mg·kg^?1; 24 h drug‐light interval) or 2‐[1‐hexyloxyethyl]‐2‐devinyl pyropheophorbide‐a (HPPH) (4 mg·m^?2;48 h) with wavelengths of 630 nm to 60J·cm^?2 and 665 nm to 15‐45J·cm^?2, respectively. With a median age of 69 years, patients were predominantly male (90%) with epithelioid histology (100%) and stage III‐IV disease (100%). PT was delivered to a median of 55.0 CGE/1.8‐2.0 CGE (range 50–75 CGE) adjuvantly (n = 8) or as salvage therapy (n = 2) following extended pleurectomy/decortication (ePD)/PDT. Two‐year local control was 90%, with distant and regional failure rates of 50% and 30%, respectively. All patients received chemotherapy, and four received immunotherapy. Surgical complications included atrial fibrillation (n = 3), pneumonia (n = 2), and deep vein thrombosis (n = 2). Median survival from PT completion was 19.5 months (30.3 months from diagnosis), and 1‐ and 2‐year survival rates were 58% and 29%. No patient experienced CTCAEv4 grade ≥2 acute or late toxicity. Our prolonged survival in very advanced‐stage patients compares favorably to survival for PT without PDT and photon therapy with PDT, suggesting possible spatial or systemic cooperativity and immune effect.     

Initiation of Apoptosis versus Necrosis by Photodynamic Therapy with Chloroaluminum Phthalocyanine

Abstract— While chloroaluminum phthalocyanine is a highly effective photosensitizer of murine leukemia P388 or L1210 cells, the mode of cell death varies as a function of the PDT dose. When cells were incubated with 0.3 mUM of the sensitizer, a light dose of 45 mJ cm_-2 (670 5 nm) yielded a 90% apoptotic cell population within 60 min. The sensitizer localized throughout the cytoplasm and catalyzed both lysosomal and mitochondrial photodamage at this light dose. Higher light doses yielded progressively more membrane photodamage and inhibited the apoptotic response as determined by the examination of Hochst dye HO 33342-IabeIed nuclei, DNA fragmentation on gels and a poly(adenosylribose) polymerase (PARP)-cleavage assay. Pulse-field gel electrophoresis revealed nonspecific DNA degradation to particles 50 kbp at the higher PDT doses but neither PARP cleavage nor apoptotic nuclei     

光动力疗法用糖基光敏剂的研究进展

作为光动力疗法中至关重要的决定性因素,光敏剂的研究受到越来越多的重视.而糖基的引入,可以大大提高光敏剂母体的膜透过性和特异吸收性.从糖基光敏剂的母体结构、糖基光敏剂分子的构效关系、糖基的作用机理以及糖基光敏剂的药物动力学和代谢产物这四个方面对近年来糖基光敏剂的研究现状进行了综述,对其发展趋势进行了展望.     

Immunosuppressive Effects of Silicon Phthalocyanine Photodynamic Therapy

The purpose of this study was to determine if silicon phthalocyanine 4 (Pc 4), a second-generation photosensitizer being evaluated for the photodynamic therapy (PDT) of solid tumors, was immunosuppressive. Mice treated with Pc 4 PDT 3 days before dinitrofluorobenzene sensitization showed significant suppression of their cell-mediated immune response when compared to mice that were not exposed to PDT. The response was dose dependent, required both Pc 4 and light and occurred at a skin site remote from that exposed to the laser. The immunosuppression could not be reversed by in vivo pre-treatment of mice with antibodies to tumor necrosis factor-alpha or interleukin-10. These results provide evidence that induction of cell-mediated immunity is suppressed after Pc 4 PDT. Strategies that prevent PDT-mediated immunosuppression may therefore enhance the efficacy of this therapeutic modality.