Synthesis and properties of photo-activable phthalocyanines: a brief overview

Phthalocyanines (Pcs) can very well satisfy the different demands of photosensitizer in photodynamic therapy (PDT) such as absorption, amphiphilicity and most importantly, high photochemical reactivity, depending on the subtle interplay of structure?Cfunction relationships. They have been shown to be phototoxic against a number of tumor cells. Certain criteria of ideal photosensitizers for PDT were described. A brief summary of the synthesis and some properties of photo-activable Pcs have been presented and an outlook for future photocytotoxic Pcs given. These Pcs are classified into three groups: (1) Pcs with different peripheral and/or non-peripheral substitution; (2) Pcs with different axial substitution; (3) Pcs with different metal center.     

血浆溶液中竹红菌乙素和2-牛磺酸修饰的竹红菌乙素的光漂白

光动力学疗法是应用光敏剂受激光激发后对靶体产生光化学作用来治疗病变。光漂白是光动力学治疗过程中普遍现象，在光动力疗法治疗血管类疾病中，光敏剂与血浆中的生物分子相互作用及其在血管中的光漂白行为直接关系到治疗效果。本文考察了HB和THB与血浆的作用和在血浆溶液中的光漂白过程，研究表明在富氧条件下，以单重态氧漂白为主；在有血浆生物分子溶液中光产物与水溶液中的光产物不同。研究表明光敏剂的结构和氧化电位导致了它们不同的光漂白机制，HB和THB与生物分子的相互作用加速了它们光漂白并影响了光产物。     

Photodynamic therapy for periodontal diseases: state of the art

BACKGROUND: Photodynamic killing of periodontopathogenic bacteria may be an alternative to the systemic application of antibacterial drugs used in the treatment of periodontal diseases. Even though the method is still in the experimental stage, increasing bacterial resistance problems may promote the introduction of photodynamic therapy (PDT) into periodontal practice. AIM: In this review a literature survey is given of PDT as seen from a periodontal perspective. METHODS: In this review, the present knowledge and experience of PDT is summarized. Literature data are presented on drawbacks of conventional antibiotics, the mechanism of PDT, bactericidal effects of PDT as well as results of clinical efforts. The future prospects of the method are discussed. RESULTS: The application of photosensitizing dyes and their excitation by visible light enables effective killing of periodontopathogens. Encouraging studies using PDT in periodontitis and in peri-implantitis are known. CONCLUSION: Even though PDT is still in experimental stages of development and testing, the method may be an adjunct to conventional antibacterial measures in periodontology. Clinical follow-up studies are needed to confirm the efficacy of the procedure.     

Influence of substitutions on asymmetric dihydroxychlorins with regard to intracellular uptake, subcellular localization and photosensitization of Jurkat cells

The search for new efficient sensitizers for photodynamic therapy (PDT) points to improve photophysical properties like absorption in the red region and singlet oxygen quantum yield as well as to control the localization of the sensitizer within the tumour cell. Depending on their physicochemical properties and their uptake mechanism, sensitizers can reach different intracellular concentrations and localize in different subcellular compartments. Moreover, the preferential localization of a sensitizer in target organelles, like mitochondria or lysosomes, could determine the cell death mechanism after PDT. This study aimed to investigate the influence of substitutions on dihydroxychlorins with regard to intracellular uptake, subcellular localization and cell death pathway. Moreover, the effect of a liposome-based delivery system was tested. The intracellular uptake was found to be strictly dependent on the sensitizer molecular structure and the means of its delivery. The most polar sensitizer in this study (compound 3) had, depending on incubation time, an intracellular concentration 2-8 times higher than the unsubstituted chlorin 1. All investigated photosensitizers localize predominantly in lysosomes but after longer incubation times weak fluorescence intensity was also detected in mitochondria and Golgi apparatus. The cell death pathway was found to be influenced by the sensitizer intracellular concentration and the applied light doses. In general, the increasing amphiphilicity of the sensitizer molecules is correlated with an increased sensitizer uptake and an increased rate of necrotic cells after irradiation.     

Porphyrin synthesis from aminolevulinic acid esters in endothelial cells and its role in photodynamic therapy

Photodynamic therapy (PDT) may cause tumour cell destruction by direct toxicity or by inducing microcirculatory shutdown. Protoporphyrin IX generated from 5-aminolevulinic acid (ALA) has been widely used as an endogenous photosensitiser in PDT. However, the hydrophilic nature of the ALA molecule limits its penetration through the stratum corneum of the skin and cell membranes and thus, ALA alkyl-esters have been developed to improve ALA permeation.The aim of this work was to study Protoporphyrin IX synthesis from ALA and its derivatives ALA methyl ester (Me-ALA) and ALA hexyl ester (He-ALA) in the microvascular endothelial cell line HMEC-1 derived from normal skin, and to evaluate their response to PDT.We found that lower light doses are required to photosensitise HMEC-1 endothelial cells than to photosensitise PAM212 transformed keratinocytes, showing some possible selectivity of ALA-PDT for vascularisation in skin.Employed at concentrations leading to equal Protoporphyrin IX synthesis, ALA, He-ALA and Me-ALA presented the same efficacy of HMEC-1 photosensitisation. However, He-ALA was a promising compound for the use in the enhancement of Protoporphyrin IX in HMEC-1 cells employed at low concentrations at both short and long time exposures whereas Me-ALA should be employed at high concentrations and longer time periods in order to surpass the Protoporphyrin IX levels obtained with ALA. The advantage of Me-ALA over ALA was based on its lower dark toxicity.This is the first work to report vascular cell photosensitisation employing alkyl-esters of ALA, and we demonstrated that these derivatives could exert the same effect as ALA and under certain conditions enhance photosensitisation of vasculature.     

Predictive power of long-range corrected functionals on the spectroscopic properties of tetrapyrrole derivatives for photodynamic therapy

Porphyrin and chlorin based compounds possess promising properties to be utilized as photosensitizers in photodynamic therapy (PDT). However, the photosensitizers available on the market today are not ideal for use in PDT, which has emphasized the need for new photosensitizers with improved photodynamic properties to be developed. Computational drug-design can be utilized in the search for improved pharmaceutical compounds, provided that the methods used are able to reproduce experimental data. In the present study we investigated, by the use of time-dependent density functional theory (TD-DFT), the performance of the long-range corrected functionals ωB97, ωB97X and ωB97XD on their ability to predict low-lying singlet excitations (>600 nm) of a set of well-known photosensitizing compounds. It was found that ωB97X reproduced the experimental red-most absorption band most satisfactorily. The use of either B3LYP, ωB97XD or M06 in geometry optimizations has a minor effect on the spectra in most cases. Calculated energy differences between the optimized singlet ground states and optimized first excited triplet states show consistent and overall higher triplet state energies for B3LYP, M06, and PBE0 compared with ωB97, ωB97X, and ωB97XD. The calculated triplet state energies are, however, sufficient to generate singlet oxygen in most cases.     

Rhodium Nanoparticles as a Novel Photosensitizing Agent in Photodynamic Therapy against Cancer

Photodynamic therapy (PDT) is a promising alternative treatment for different types of cancer due to its high selectivity, which prevents healthy tissues from being damaged. The use of nanomaterials in PDT has several advantages over classical photosensitizing agents, due to their unique properties and their capacity for functionalization. Especially interesting is the use of metallic nanoparticles, which are capable of absorbing electromagnetic radiation and either transferring this energy to oxygen molecules for the generation of reactive oxygen species (ROS) or dissipating it as heat. Although previous reports have demonstrated the capacity of Rh derivatives to serve as anti-tumor drugs, to the best of our knowledge there have been no studies on the potential use of small-sized Rh nanoparticles as photosensitizers in PDT. In this study, 5 nm Rh nanoparticles have been synthesized and their potential in PDT has been evaluated. The results show that treatment with Rh nanoparticles followed by NIR irradiation induces apoptosis in cancer cells through a p53-independent mechanism.     

Research advances in the use of tetrapyrrolic photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is a promising new treatment modality for several diseases, most notably cancer. In PDT, light, O2, and a photosensitizing drug are combined to produce a selective therapeutic effect. Lately, there has been active research on new photosensitizer candidates, because the most commonly used porphyrin photosensitizers are far from ideal with respect to PDT. Finding a suitable photosensitizer is crucial in improving the efficacy of PDT. Recent synthetic activity has created such a great number of potential photosensitizers for PDT that it is difficult to decide which ones are suitable for which pathological conditions, such as various cancer species. To facilitate the choice of photosensitizer, this review presents a thorough survey of the photophysical and chemical properties of the developed tetrapyrrolic photosensitizers. Special attention is paid to the singlet-oxygen yield (PhiDelta) of each photosensitizer, because it is one of the most important photodynamic parameters in PDT. Also, in the survey, emphasis is placed on those photosensitizers that can easily be prepared by partial syntheses starting from the abundant natural precursors, protoheme and the chlorophylls. Such emphasis is justified by economical and environmental reasons. Several of the most promising photosensitizer candidates are chlorins or bacteriochlorins. Consequently, chlorophyll-related chlorins, whose PhiDelta have been determined, are discussed in detail as potential photosensitizers for PDT. Finally, PDT is briefly discussed as a treatment modality, including its clinical aspects, light sources, targeting of the photosensitizer, and opportunities.     

Synthesis and effect on SMMC-7721 cells of new benzo[c,d]indole rhodanine complex merocyanines as PDT photosensitizers

Photodynamic therapy (PDT) represents a modern and noninvasive therapeutic approach, however, it relies on the development of photosensitizers. Here five new benzo[c,d]indole rhodamine complex merocyanines (BIRCM) D1-D5, displaying low dark toxicity and significant photo toxicity, were synthesized as PDT photosensitizers, and characterized by ¹H NMR, IR, UV–Vis and HRMS. The investigation of their absorption spectra in different solvents showed that the absorption maxima and molar extinction coefficient were in the region 507–679 nm and 0.21 × 10⁴–1.27 × 10⁵ L · mol^?1cm^?1, respectively. The evaluation of PDT activity showed that only irradiation could not kill SMMC-7721 cells, and the cell survival rate and inhibition rate at the application dose and duration was 92%–87% and 78%–49%, respectively. Especially, using D2, absorbed in the red zone, as photosensitizer for PDT analyzed its effect on SMMC-7721 cells survival, it could be found that the cell survival rate was 92% without irradiating and the cell inhibited rate was 78% under irradiating at concentrations of 2.5 × 10^?6 mol/L, displaying low dark toxicity and high photo toxicity, which was valuable for PDT of some microvascular diseases or other superficial diseases.     

Photodynamic properties of naphthosulfobenzoporphyrazines, novel asymmetric, amphiphilic phthalocyanine derivatives.

Metallo naphthosulfobenzoporphyrazines sulfonated to different degrees (M-NSBP) were prepared, and their potential as photosensitizers for the photodynamic therapy (PDT) of cancer was evaluated. M-NSBP can be viewed as hybrid molecules between sulfophthalocyanines and naphthalocyanines resulting in distinct differences in the absorption spectra between the mono-through tetrasulfonated derivatives. This feature greatly facilited their purification. Using V-79 Chinese hamster cells in vitro, the disulfonated derivatives were found slightly more photoactive than the hydrophilic trisulfonated derivatives while the monosulfonated derivative was inactive, in spite of a sixfold higher cell uptake. In the case of the di- and trisulfonated derivatives, differences in phototoxicity correlated well with their relative cell uptake. Substitution of Al for Zn had little effect on the extent of phototoxicity of the M-NSBP. In vitro PDT of the EMT-6 cells after in vivo dye administration, revealed a similar potency for direct cell killing between the di- and trisulfonated AlOH-NSBP, while the monosulfonated analog was inactive. PDT with the amphiphilic disulfonated AlOH-NSBP on the EMT-6 mammary tumor in BALB/c mice induced a significant tumor response, while the monosulfonated derivative was much less active.     

Computational design of chlorin based photosensitizers with enhanced absorption properties

The porphyrin and chlorin parent compounds constitute the base of many potent photosensitizers aimed to be utilized in photodynamic therapy (PDT). However, the photosensitizers available on the market today are not ideal for use in PDT; many of them suffering from drawbacks such as long-lasting photosensitization or absorption at wavelengths below the optimal tissue penetration. This has emphasized the need of new photosensitizers with improved photodynamic properties. In the present study we have used density functional theory based methods to design new chlorin compounds with conjugated substituents such as vinyl groups and carboxylic acids, aiming for strong absorption in the therapeutic window of PDT. The specific substituent positions were found to have a significant effect on the spectra. A chlorin with four propenoic acids was able to red-shift the absorption the most compared with non-substituted chlorin, generating the red-most absorption at 755 nm, and with significantly enhanced oscillator strengths. The results from the present study constitute a useful starting point for further design of tetrapyrrole derivatives as improved photosensitizers.     

Prodrugs of 5-Aminolevullinic Acid for Photodynamic Therapy

Abstract— The use of 5-aminolevulinic acid (ALA) as a protoporphyrin IX (PpIX) precursor for photodynamic therapy (PDT) became very popular in a short time. However, despite its advantages, ALA also has a drawback; it shows a poor ability to diffuse through biological membranes because of its low Iipophilicity. As a consequence, a high dose of ALA must be administered in order to increase PpIX in the afflicted tissue at a level sufficient for PDT. A possible solution to this problem is the use of derivatives of ALA. ALA prodrugs are expected to have better diffusing properties as a result of their enhanced Jipophilicity and are converted into the parent ALA after enzymatic hydrolysis. In this report, results are presented of the synthesis of a number of ALA derivatives. The ALA prodmgs were investigated regarding the optimum conditions for cell penetration and PPIX formation in an in vitro cellular test system. It is shown that several prod· rugs do indeed enhance the amount of accumulated PPIX considerably as compared to ALA. Finally, the most promising prodrugs were tested in an animal model and showed increased PPIX formation under these conditionsas well.     

Innovative Strategies for Hypoxic‐Tumor Photodynamic Therapy

Despite its clinical promise, photodynamic therapy (PDT) suffers from a key drawback associated with its oxygen‐dependent nature, which limits its effective use against hypoxic tumors. Moreover, both PDT‐mediated oxygen consumption and microvascular damage further increase tumor hypoxia and, thus, impede therapeutic outcomes. In recent years, numerous investigations have focused on strategies for overcoming this drawback of PDT. These efforts, which are summarized in this review, have produced many innovative methods to avoid the limits of PDT associated with hypoxia.     

Photosensitizer-Mesoporous Silica Nanoparticles Combination for Enhanced Photodynamic Therapy†

Mesoporous silica nanoparticles (MSNs) are widely known for their versatile applications. One of the most extended is as drug delivery systems for the treatment of cancer and other diseases. This review compiles the most representative examples in the last years of functionalized MSNs as photosensitizer carriers for photodynamic therapy (PDT) against cancer. Several commercially available photosensitizers (PSs) demonstrated poor solubility in an aqueous medium and insufficient selectivity for cancer tissues. The tumor specificity of PSs is a key factor for enhancing the PDT effect and at the same time reducing side effects. The use of nanoparticles and particularly MSNs, in which PS is covalently anchored or physically embedded, can overcome these limitations. For that, PS-MSNs can be externally decorated with compounds of interest in order to act as an active target for certain cancer cells, demonstrating enhanced phototoxicity in vitro and in vivo. The objective of this review is to collect and compare different nanosystems based on PS-MSNs pointing out their advantages in PDT against diverse types of cancers.     

5-Aminolevulinic acid derivatives in photomedicine: Characteristics, application and perspectives

The introduction of lipophilic derivatives of the naturally occurring heme precursor 5-aminolevulinic acid (5-ALA) into photomedicine has led to a true revival of this research area. 5-ALA-mediated photodynamic therapy (PDT) and fluorescence photodetection (FD) of neoplastic disease is probably one of the most selective cancer treatments currently known in oncology. To date, this method has been assessed experimentally for the treatment of various medical indications. However, the limited local bioavailability of 5-ALA has widely prevented its use in daily clinical practice. Although researchers were already aware of this drawback early during the development of 5-ALA-mediated PDT, only recently have well-established concepts in pharmaceutical science been adapted to investigate ways to overcome this drawback. Recently, two derivatives of 5-ALA, methylaminolevulinate (MAL) and hexylaminolevulinate (HAL), gained marketing authorization from the regulatory offices in Europe and Australia. MAL is marketed under the trade name Metvix for the treatment of actinic keratosis and difficult-to-treat basal cell carcinoma. HAL has recently been launched under the trade name Hexvix to improve the detection of superficial bladder cancer in Europe. This review will first present the fundamental concepts underlying the use of 5-ALA derivatives in PDT and FD from a chemical, biochemical and pharmaceutical point of view. Experimental evidences from preclinical data on the improvements and limits observed with 5-ALA derivatives will then be introduced. The state-of-the-art from clinical studies with 5-ALA esters will be discussed, with special emphasis placed on the process that led to the development of MAL in dermatology and to HAL in urology. Finally, we will discuss promising medical fields in which use of 5-ALA derivatives might potentially lead to further use of this methodology in photomedicine.     

8-巯基喹啉阴离子的锌配合物及其衍生物的电子光谱性质的含时密度泛函理论研究

采用从头算(ab initio)和密度泛函理论(DFT B3LYP)方法, 对配合物8-巯基喹啉锌Zn(tq)₂及其5种衍生物基态结构进行优化, 用含时密度泛函理论(TD-DFT/B3LYP)及6-31＋G(d)基组计算吸收光谱; 同时用ab initio HF 单激发组态相互作用(CIS)法在6-31G(d)基组上优化其最低激发单重态几何结构, 用含时密度泛函理论计算发射光谱. 结果表明, 电子在基态与激发态间的跃迁, 主要是在配体8-巯基喹啉(tq)环内的电荷转移, 电子从含S的苯硫酚环转移至含N的吡啶环上; 吸收光谱和发射光谱的计算值与实验值基本符合. 该类配合物都是优良的电子传输材料, 改变金属离子和取代基均可以调控发光材料的光谱波段.     

Photodynamic Tumor Eradication With a Novel Targetable Photosensitizer: Strong Vascular Effects and Dependence on Treatment Repetition Versus Potentiation

A novel pyropheophorbide‐a (PPa) derivative, Ac‐sPPp, was developed in our lab for targeted photodynamic therapy (PDT) and combination therapies. Its versatile peptide moiety, high water‐solubility, amphiphilicity, and micellar aggregation allow efficient coupling to targeting moieties and convenient mixing with other therapeutics. Photosensitizer immunoconjugate (PIC) targeted PDT, using Ac‐sPPp conjugated to therapeutic anti‐epidermal growth factor receptor (EGFR) antibody cetuximab, and PDT + chemotherapy combination treatment, using Ac‐sPPp mixed with stealth liposomal doxorubicin (Doxil), were investigated as promising strategies for potentiating PDT and improving target specificity. Passively targeted PDT with Ac‐sPPp only or surfactant‐solubilized PPa was also investigated for comparison. The A‐431 human vulvar squamous cell carcinoma, xenografted in nude mice, was chosen as a tumor model because of its high EGFR expression and sensitivity to liposomal doxorubicin in vitro. Fluorescence imaging and PDT experiments showed that Ac‐sPPp formulations circulated far longer and provided superior tumor contrast and superior tumor control compared to PPa. Strong PDT vascular effects were observed by laser Doppler imaging regardless of whether Ac‐sPPp was passively or actively targeted. Passively targeted Ac‐sPPp PDT gave equivalent or better tumor control than PIC‐targeted PDT or PDT + Doxil combination therapy, and when treatments were repeated, it also yielded the highest cure rate.     

POLYMERIC SURFACTANT STRUCTURE

Polymeric surfactants are amongst the most widespread of all polymers. In nature, proteins and polysaccharidescause self organization as a result of this surfactancy; in industry, polymeric surfactants play key roles in the food, explosivesand surface coatings sectors. The generation of useful nano- and micro-structures in films and emulsions as a result ofpolymer amphiphilicity and the application of mechanical stress is discussed. The use of X-ray and neutron small anglescattering and reflectivity to measure these structures and their dynamic properties will be described. New results on linear and dendritic polymer surfactants are presented.     

Rationally Designed α‐Helical Broad‐Spectrum Antimicrobial Peptides with Idealized Facial Amphiphilicity

A series of 12‐amino acid peptide analogs is designed using point mutation strategy based on an α‐helical peptide template. The first mutation in the series, KL12, has an idealized facial amphiphilicity. Subsequent mutations are performed to increase hydrophobic or cationic contents. Idealized facial amphiphilicity show enhanced antimicrobial activity and selectivity against most of the tested microbes. Increasing hydrophobic contents further enhance antimicrobial potency; however, selectivity of the most hydrophobic analog is impaired due to non‐specific interactions with mammalian cell membrane. This study demonstrates that facial amphiphilicity and hydrophobic content are strongly correlated with antimicrobial activity and selectivity of antimicrobial peptides.     

Comparative sensitivity of microvascular endothelial cells, fibroblasts and tumor cells after in vitro photodynamic therapy with meso-tetra-hydroxyphenyl-chlorin

The phototoxic effect of meso-tetra-hydroxyphenyl-chlorin (mTHPC)-mediated photodynamic therapy (PDT) on human microvascular endothelial cells (hMVEC) was compared with that on human fibroblasts (BCT-27) and two human tumor cell lines (HMESO-1 and HNXOE). To examine the relationship between intrinsic phototoxicity and intracellular mTHPC content, we expressed cell survival as a function of cellular fluorescence. On the basis of total cell fluorescence, HNXOE tumor cells were the most sensitive and BCT-27 fibroblasts the most resistant, but these differences disappeared after correcting for cell volume. Endothelial cells were not intrinsically more sensitive to mTHPC-PDT than tumor cells or fibroblasts. Uptake of mTHPC in hMVEC increased linearly to at least 48 h, whereas drug uptake in the other cell lines reached a maximum by 24 h. No difference in drug uptake was seen between the cell lines during the first 24 h, but by 48 h hMVEC had a 1.8- to 2.8-fold higher uptake than other cell lines. Endothelial cells showed a rapid apoptotic response after mTHPC-mediated PDT, whereas similar protocols gave a delayed apoptotic or necrotic like response in HNXOE. We conclude that endothelial cells are not intrinsically more sensitive than other cell types to mTHPC-mediated PDT but that continued drug uptake beyond 24 h may lead to higher intracellular drug levels and increased photosensitivity under certain conditions.