Chalcedony (a crystalline variety of silica): biogenic origin in electric organs from living Psammobatis extenta (family Rajidae)

The electric organs of electric fish have been used extensively for the study of peripheral cholinergic synapses. Aluminum and silicon have been observed in the electrocytes of Psammobatis extenta, a fish belonging to the family Rajidae, using a combination of scanning electron microscopy and X-ray spectrometry. Based on this evidence, the presence of silica minerals has been documented by means of mineralogical techniques. Electric organ cryostat sections and subcellular fractions were observed using a Leica DMLP mineralogical microscope. The shape, size and color, among other properties, were analyzed in plane-polarized light, while birefringence and the extinction angle, which allow for mineral identification, were observed through crossed-polarized illumination. The distribution of chalcedony, an oxide silicon mineral, in the sections and all the fractions of the electric organ was recorded. X-ray diffraction analysis of the electric organ segments showed a similar result, with a low-quartz variety. Chalcedony precipitation occurred at a specific pH (7-8) and oxidation potential (Eh; 0.0 to -0.2). This observation supports the important role played by pH and Eh conditions in silica precipitation in electrocytes, as has been reported in geological environments. It is possible that silica formation and silica degradation in electric organs are also related to the enzymes, silicatein and silicase, that direct the polymerization and depolymerization of amorphous silica in sponges. Carbonic anhydrases (silicase) are involved in physiological pH regulation. Crystallization of chalcedony via spiral growth from a partially polymerized fluid is consistent with processes known to occur in organic systems. This is the first time that a biogenically produced crystalline mineral phase (i.e., chalcedony) has been observed in the electrocytes and cholinergic nerves from living electric fish.     

Encapsulation of Photosensitizers and Upconversion Nanocrystals in Lipid Micelles for Photodynamic Therapy

Photodynamic therapy (PDT) is a promising method for cancer therapy. However, it is constrained by limited penetration depth of visible light, hydrophobicity of photosensitizers, and lack of tumor targeting. In this work, the photosensitizer zinc phthalocyanine (ZnPc) and upconversion nanocrystals (UCNs) are encapsulated into OQPGA‐PEG/RGD/TAT lipid micelles. The UCNs acting as a nanotransducer convert deep‐penetrating near‐infrared (NIR) light to visible light for activating the photosensitizer. OQPGA‐PEG/RGD/TAT lipid micelles are used as a carrier for the photosensitizer, with improved biocompatibility and cancer‐targeting ability. The results show that the photosensitizer ZnPc‐ and UCNs‐loaded OQPGA‐PEG/RGD/TAT lipid micelles are nanoparticles with an average size of 25 nm. The lipid micelle nanoparticles are stable in water with low leakage of photosensitizer. The absorption peak of the photosensitizer overlaps with the emission peak of UCNs, so the visible fluorescence emitted from the UCNs upon excitation by the NIR laser at 980 nm can activate the photosensitizer to produce singlet oxygen for PDT. The targeting RGD peptide and cell‐penetrating TAT peptide on the surface help the nanoparticles getting into cancer cells. The OQPGA‐PEG/RGD/TAT lipid micelles encapsulated with both the photosensitizer ZnPc and UCNs could be used for targeted PDT by using deep‐penetrating NIR light as the light source.     

光敏剂对肿瘤细胞损伤效应与孵育时间关系的拉曼光谱分析

利用拉曼光谱研究光敏剂与HepG2肝癌细胞不同孵育时间的光动力损伤效应。结果表明孵育时间与光动力损伤效应成正相关性,但孵育时间超过一定值,延长孵育时间并不能提高光动力损伤效应。     

光敏剂CPD4对肿瘤组织DNA损伤的拉曼光谱研究

观测了小牛胸腺DNA、腹水型S_(180)肿瘤组织DNA以及光敏剂CPD_4对肿瘤组织DNA损伤的拉曼光谱。肿瘤组织DNA是分别从注射了光敏剂和生理盐水的荷瘤小鼠的肿瘤中提取的。实验结果表明,肿瘤组织DNA的拉曼光谱与正常组织DNA的有所差异,最明显的是脱氧核糖的特征谱线在正常组织DNA拉曼光谱中出现而在肿瘤组织DNA中却几乎消失或变为很弱的小峰。这些差异可作为肿瘤早期诊断的参考。实验结果还表明,光敏剂对肿瘤组织DNA各碱基产生不同程度的破坏,在DNA修复酶的作用下,可使脱氧核糖和鸟嘌呤得到修复。     

荧光偏振光谱法探测光动力过程中癌细胞膜的流动性

以DPH作荧光探剂,用荧光偏振光谱法研究了金属酞菁配合物苯硫基钛菁锌(C₅₆H₃₂N₈S₄Zn)在光动力过程中,不同光照时间对乳腺癌细胞膜流动性的影响。实验结果表明,经光照激发光敏剂金属酞菁后,荧光标记团的偏振度增大,癌细胞膜流动性降低,微黏度升高。说明这是光动力治疗的疗效所在。用酶联免疫检测(MTT法)不同光照时间对细胞存活的影响,结果显示癌细胞最低存活率与膜流动性降低成正相关。这表明光动力过程在一个相近的程度影响癌细胞膜的流动性和增殖,提示光动力过程可能通过影响细胞膜流动性引起细胞增殖变化,即细胞膜是光动力作用的一个位点。     

Photodynamic Therapy of Human Hepatoma Using Semiconductor Quantum Dots as Sole Photosensitizer

Currently, the studies about photodynamic therapy (PDT) of human cancers have made considerable progress and attracted tremendous attention. The existing photosensitizers used for PDT are mainly organic compounds. In order to enhance their photosensitizing efficacy, some studies reported hybrid photosensitizers consisting of inorganic quantum dots (QDs) and organic photosensitizers. Herein, a new type of photosensitizer consisting of sole semiconductor CdTe QDs with good photosensitizing efficacy, excellent water dispersibility, and stability is reported. The photosensitizer is prepared through a facile one‐step strategy using sodium hyaluronate as a stabilizing and targeting agent. Different from most of the previous reports, the as‐prepared QDs do not show inhibition effects on normal cells in the experimental concentration range, but can also be directly utilized as a photosensitizer to specifically and remarkably inhibit the proliferation of human hepatoma cells. Mechanism studies reveal that the QDs could be specifically internalized by hepatoma cells, considerably induce the generation of intracellular reactive oxidative species under light illumination, and significantly induce the necrosis of hepatoma cells. This work provides an inspiration for the direct application of QDs as a new type of photosensitizer to specifically and significantly treat human hepatoma through PDT.     

Photobleaching mechanisms of Radachlorin photosensitizer in aqueous solution

The time dependence of the fluorescence intensity of aqueous solutions of Radachlorin photosensitizer at different concentrations and the influence of the dissolved oxygen concentration on the fluorescence dynamics are analyzed. The experimental results are interpreted based on the numerical solution of the system of kinetic equations describing the photochemical processes that lead to the formation and degradation of singlet oxygen in solution. The influence of possible mechanisms of photosensitizer photobleaching is analyzed. It is shown that the main photobleaching mechanism under our experimental conditions is the chemical reaction between the photosensitizer in the triplet state and dissolved oxygen molecules. Two rate constants of electron-transfer chemical reactions, which are important for understanding the nature of the occurring photoprocesses, are determined.     

EPR investigations of synthetic manganese complexes as bio-mimics of the water oxidation complex in photosystem II

Research in the Swedish Consortium for Artificial Photosynthesis aims to construct a supramolecular system containing synthetically connected D (electron donor), S (photosensitizer), and A (electron acceptor) compartments. These are intended to carry out catalytic water oxidation on the donor side and catalytic hydrogen formation on the acceptor side, driven by light energy absorbed by the photosensitizer. In this minireview, we focus our attention on our spectroscopic and electrochemical studies of a series of manganese complexes partially mimicking the water-oxidizing manganese complex in the natural photosystem II (PSII), using ruthenium(II) tris(bypyridine) as the photosensitizer. The manganese complexes we discuss fall in three categories: monomeric manganese systems covalently linked to the ruthenium(II) tris(bypyridine) center, dimeric manganese complexes that are not covalently connected to ruthenium(II) tris(bypyridine) and dimeric manganese complexes covalently bound to a ruthenium(II) tris(bypyridine) center via an amide bound. The review focuses on the use of electron paramagnetic resonance spectroscopy in the studies of our manganese compounds.     

Photostability of a C<Subscript>60</Subscript> fullerene coating as a solid-phase photosensitizer of singlet oxygen

The stability of the optical properties and the generation efficiency of singlet oxygen of a solidphase photosensitizer based on fullerene in an aqueous suspension subjected to prolonged intense irradiation with visible light are studied in comparison with a photosensitizer based on methylene blue in an aqueous solution. Changes in the absorption spectra show that, as a result of 20-min irradiation, the content of fullerene decreases by 2% from its initial value, while that of methylene blue decreases by 19%. In both cases, the dynamics of the decrease in the photosensitizing ability of the photosensitizers in the course of their irradiation correlates with the changes in their spectra, but the magnitude of this decrease in the case of the solid-phase photosensitizer is greater than the magnitude of its spectral changes because of the surface nature of the photosensitization process. The study of the absorption spectra of fullerene coatings shows that their irradiation in water or in air causes the same photodegradation of fullerene. At the same time, studies with the help of the electron spin resonance (ESR) technique reveal differences in the nature of processes undergone by fullerene in water and in air.     

低玻璃化转变温度的光折变聚合物中光敏剂作用研究

通过对光敏剂C₆₀含量不同的低玻璃化转变温度的光折变聚合物聚乙烯咔唑掺杂2,5-二甲基-4-(4′-硝基苯偶氮基)苯甲醚、N-乙基咔唑和C₆₀的空间相移角和二波耦合系数的测量,研究了光敏剂在此类光折变聚合物中的作用- 关键词：     

光动力学疗法新型光敏剂的光谱特性研究

实验研究了用于光动力学诊断和治疗的新型光敏剂二磺基二邻苯二甲酰亚胺甲基酞菁锌（ZnPcS2P)癌光啉（PsD-007)、血啉甲醚（HMME）以及早期应用于临床的血卟啉衍生物（HpD)分别在生理盐水和含10％人血清生理盐水中的光谱特性。结果表明：除ZnPcS2P2的最大吸收峰位于670nm之外，其余三种光敏剂在人血清环境中的最大吸收峰都位于405nm处，但与生理盐水环境相比索瑞（Soret)峰发生了12nm的红移。在波长为413和514.5nm光源激发下，HMME，HpD和PsD-007在人血清环境中的荧光发射峰都分别位于625和690nm，但413nm光源的激发效率比514.5nm光源高出3倍左右，而且HEEM的荧光激发效率最高，HpD次之，PsD-007最低。     

Quenching of porous silicon photoluminescence by molecular oxygen and dependence of this phenomenon on storing media and method of preparation of pSi photosensitizer

The quenching of porous silicon photoluminescence (pSi PL) by molecular oxygen has been studied in different storing media in an attempt to clarify the mechanism of the energy transfer from the silicon photosensitizer to the oxygen acceptor. Luminescent materials have been prepared by two methods: electrochemical anodizing and chemical etching. Different structural forms were used: porous layers on silicon wafer and two kinds of differently prepared powder. Dry air and liquid water were employed as storing media; quenching behaviour was under observation until total degradation of quenching properties. Singlet oxygen molecules generation through energy transfer from photoluminescent pSi was the only photosensitizing mechanism observed under dry gas conditions. This PL quenching process was preferentially developed at 760 nm (1.63 eV) that corresponds to the formation of the ¹Σ singlet oxygen state. Oxidation of the pSi photosensitizer was the main factor that led to its total deactivation in a time scale of few weeks. Regarding water medium, different photosensitizing behaviour was observed. In watery conditions, two preferred energy levels were found: the one detected in dry gas and another centred at approximately 2.2 eV (550 nm). Formation of reactive oxygen species (ROS) different from singlet oxygen, such as superoxide anion or superoxide radical, can be responsible for the second one. This second quenching process developed gradually after the initial contact of pSi photosensitizer with water and then degraded. The process lasted only several hours. Therefore, functionalization of the pSi photosensitizer is probably required to stabilize its PL and quenching properties in the watery physiological conditions required for biomedical applications.     

掺杂无机纳米超微粒的有机聚合物体系中的光折变效应

研究了掺杂无机纳米超微粒的有机聚合物体系中的光折变效应．体系中以Ｃｕ２Ｓ／ＣｄＳ／ＺｎＳ复合超微粒为光敏剂,ＰＶＫ为载流子输运剂,电光分子为ＥＰＮＡＣ．给出了光敏剂的制备方法,ＥＰＮＡＣ的分子结构及电光特性,以及该光折变材料中的两波耦合效应的实验结果．结果表明,无机纳米超微粒可用作光折变材料中的光敏剂,这是它的一种新的应用．     

风湿性关节炎动物模型中血啉甲醚荧光强度的同步检测研究

光动力疗法的疗效依赖于治疗过程中靶组织中光敏剂的含量或浓度 ,而药物在组织中的分布特性是受动物机体调控的 ,因此 ,同一个体不同组织对光敏剂吸收的时间特性需要同时进行检测才能排除个体之间的差异。建立了一套空间三通道激光诱导荧光同步检测装置 ,并用该装置研究了活体大耳白兔风湿性关节炎模型滑膜、软骨和皮肤对血啉甲醚吸收的时间特性。研究结果表明 ,炎性滑膜组织对血啉甲醚的吸收量远大于软骨和皮肤 ,这一差别在静脉给药即刻就很明显 ,在静脉给药后 2 0min内 ,滑膜中的光敏剂药物含量约为软骨和皮肤中的 6倍。因此 ,对于借助血啉甲醚 ,用光动力疗法治疗风湿性关节炎并采用体外照射治疗方案时 ,从注药即刻开始 ,前 2 0min左右进行光照治疗可能是较好的选择。     

Ultrasonic irradiation enhanced the efficacy of antimicrobial photodynamic therapy against methicillin-resistant Staphylococcus aureus biofilm

Antimicrobial photodynamic therapy (aPDT) is a non-pharmacological antimicrobial regimen based on light, photosensitizer and oxygen. It has become a potential method to inactivate multidrug-resistant bacteria. However, limited by the delivery of photosensitizer (PS) in biofilm, eradicating biofilm-associated infections by aPDT remains challenging. This study aimed to explore the feasibility of combining ultrasonic irradiation with aPDT to enhance the efficacy of aPDT against methicillin-resistant staphylococcus aureus (MRSA) biofilm. A cationic benzylidene cyclopentanone photosensitizer with much higher selectivity to bacterial cells than mammalian cells were applied at the concentration of 10 μM. 532 nm laser (40 mW/cm², 10 min) and 1 MHz ultrasound (500 mW/cm², 10 min, simultaneously with aPDT) were employed against MRSA biofilms in vitro. In addition to combined with ultrasonic irradiation and aPDT, MRSA biofilms were treated with laser irradiation only, photosensitizer only, ultrasonic irradiation only, ultrasonic irradiation and photosensitizer, and aPDT respectively. The antibacterial efficacy was determined by XTT assay, and the penetration depth of PS in biofilm was observed using a photoluminescence spectrometer and a confocal laser scanning microscopy (CLSM). In addition, the viability of human dermal fibroblasts (WS-1 cells) after the same treatments mentioned above and the uptake of P3 by WS-1 cells after ultrasonic irradiation were detected by CCK-8 and CLSM in vitro. Results showed that the percent decrease in metabolic activity resulting from the US + aPDT group (75.76%) was higher than the sum of the aPDT group (44.14%) and the US group (9.88%), suggesting synergistic effects. Meanwhile, the diffusion of PS in the biofilm of MRSA was significantly increased by 1 MHz ultrasonic irradiation. Ultrasonic irradiation neither induced the PS uptake by WS-1 cells nor reduced the viability of WS-1 cells. These results suggested that 1 MHz ultrasonic irradiation significantly enhanced the efficacy of aPDT against MRSA biofilm by increasing the penetration depth of PS. In addition, the antibacterial efficacy of aPDT can be enhanced by ultrasonic irradiation, the US + aPDT treatment demonstrated encouraging in vivo antibacterial efficacy (1.73 log₁₀ CFU/mL reduction). In conclusion, the combination of aPDT and 1 MHz ultrasound is a potential and promising strategy to eradicate biofilm-associated infections of MRSA.     

The measurement of the absorption spectra of chlorine e 6 photosensitizer and hemoglobin in whole blood by multiple light scattering

The potential of using multiple light scattering methods to monitor the state and concentration of photosensitizer and hemoglobin in whole blood is demonstrated. Samples of whole blood with various contents of chlorine e ₆ photosensitizer were studied in the spectral region of 620–850 nm. On the basis of experimentally measured coefficients of diffuse reflection and transmission, absorption spectra of blood with and without the photosensitizer and the concentrations of oxy-, deoxy-, and methemoglobin in the samples are calculated. On the basis of this information, the absorption spectrum of chlorine e ₆ in whole blood is reconstructed and its state and concentration are estimated for the first time. It is found that chlorine e ₆ in whole blood occurs mainly in the monomer form.     

Phototransformation of hematoporphyrin in aqueous solution: Anomalous behavior at low oxygen concentration

The photoactivation of a photosensitizer is the initial step in photodynamic therapy (PDT) where photochemical reactions result in the production of reactive oxygen species and eventually cell death. In addition to oxidizing biomolecules, some of these photochemical reactions lead to photosensitizer degradation at a rate dependent on the oxygen concentration among other factors. We investigated photodegradation of Photogem ® (28 μM), a hematoporphyrin derivative, at different oxygen concentrations (9.4 to 625.0 μM) in aqueous solution. The degradation was monitored by fluorescence spectroscopy. The degradation rate (M/s) increases as the oxygen concentration increases when the molar ratio of oxygen to Photogem® is greater than 1. At lower oxygen concentrations (<25 μM) an inversion of this behavior was observed. The data do not fit a simple kinetic model of first-order dependence on oxygen concentration. This inversion of the degradation rate at low oxygen concentration has not previously been demonstrated and highlights the relationship between photosensitizer and oxygen concentrations in determining the photobleaching mechanism(s). The findings demonstrate that current models for photobleaching are insufficient to explain completely the effects at low oxygen concentration.     

In vivo study of laser irradiation of fractionated drug administration based mechanism for effective photodynamic therapy in rat liver

Up-regulation of stress-activated proteins in cancer cells plays a protective role against photodynamic induced apoptosis. Post photodynamic therapy extracted normal rat liver tissue usually shows a fraction of surviving cells, the photodynamic resistant cells, residing in the necrotic region. To treat these photo-dynamic resistant cells a technique has been proposed based on fractionated drug administration of diluted photosensitizer, keeping the net concentration (5 mg/kg) constant, and subsequently varying drug light interval (DLI). Flourescence measurements were made for the presence of photosensitizer in a tissue. For qualitative analysis both histological and morphological studies were made. Although preliminary aim of this approach was not achieved but there were some interesting observation made i.e. for higher dilution of photosensitizer there was a sharp boundary between necrotic and normal portion of tissue. An increase in the absorption coefficient (α) from 2.7 → 2.9 was observed as photosensitizer was diluted while the corresponding threshold dose (D _th) persistently decreases from (0.10 → 0.02) J/cm² when irradiated with a 635 nm laser fluence of 150 J/cm².     

Luminescence Study of Singlet Oxygen Production by Meso-Tetraphenylporphine

The research in the field of the photodynamic therapy of cancer (PDT) is focused on a development of photosensitizers exhibiting high quantum yield of singlet oxygen production. Direct time-resolved spectroscopic observation of singlet oxygen phosphorescence can provide time constants of its population and depopulation as well as photosensitizer phosphorescence lifetime and relative quantum yields. In our contribution, a study of time and spectral resolved phosphorescence of singlet oxygen photosensitized by meso-tetraphenylporphine in acetone together with the photosensitizer phosphorescence is presented. Time constants of singlet oxygen population and depopulation were determined at wide range of photosensitizer concentrations. The time constant of singlet oxygen generation (0.28 ± 0.01) s is slightly shorter then the lifetime of photosensitizer's triplet state (0.32 ± 0.01) s. It is caused by lower ability of TPP aggregates to transfer excitation energy to oxygen. The lifetime of singlet oxygen (50 s) decreases with increasing photosensitizer concentration. Therefore, the photosensitizer acts also as a quencher of oxygen singlet state, similarly to the effects observed in [A. A. Krasnovsky, P. Cheng, R. E. Blankenship, T. A. Moore, and D. Gust (1993). Photochem. Photobiol. 57, 324–330; H. Küpper, R. Ddic, A. Svoboda, J. Hála, and P. M. H. Kroneck (2002). Biochim. Biophys. Acta Gen. Subj. 1572, 107–113]. Moreover, the increasing concentraion of the photosensitizer causes a slight hypsochromic shift of the singlet oxygen luminescence maximum.     

The development of photosensitized pulsed and continuousultraviolet decontamination techniques for surfaces and solutions

The experimental results of a decontamination process that uses an ultraviolet (UV) light and a chemical photosensitizer for disinfecting surfaces and solutions are reported. Reduction in the microbial viability as a function of applied UV fluence and initial photosensitizer concentration is presented for the inactivation of both the vegetative and spore forms of Bacillus subtilis niger. Encouraging results have been obtained with both aqueous solutions and surfaces; and with both continuous and pulsed UV light sources. Extrapolation of the results and an estimate of the process speed and efficiency permit a comparison with other decontamination methods