The photodynamic effect: the comparison of chemiexcitation by luminol and phthalhydrazide

The presence of light, oxygen and photosensitizer (organic dye) is required for the photodynamic effect. Light and photosensitizer are harmless by themselves, but when combined with oxygen, reactive oxygen species (ROS) can be produced. This photodynamic effect is used in photodynamic therapy (PDT); the production of ROS as lethal cytotoxic agents can inactivate tumor cells. However, during PDT, there are many difficulties, so it is not possible to excite the photosensitizer using a laser, a source of light at the wavelengths specific to the photosensitizer (in visible region of the spectrum). Chemiluminescence is the light emission as a result of a chemical reaction. It is possible to use a chemiluminescent mixture to excite the photosensitizer even if the light emission does not conform to the absorption maximum of the photosensitizer. Luciferin and luminol have been used as chemiluminescent compounds (energizers) for the excitation of the photosensitizers. The aim of this work was to compare the chemiexcitation of some selected photosensitizers (e.g. fluorescein, eosin, methylene blue, hypericin and phthalocyanines) by chemiluminescent mixtures containing luminol (high chemiluminescent quantum yield) or phthalhydrazide (low chemiluminescent quantum yield) on some Gram‐positive (Enterococcus faecalis, Staphylococcus aureus) and Gram‐negative (Pseudomonas aeruginosa, E. coli) bacteria and some cell lines (NIH3T3 and MCF7). The efficiency of the chemiexcitation was dependent on the kind of the photosensitizer and on the type of the bacterial strain or cell line and was independent of the energizers. Copyright © 2010 John Wiley & Sons, Ltd.     

Photodynamic Activity of Plant Extracts from Sarawak,Borneo

Photodynamic therapy (PDT) is a medical treatment that involves the irradiation of an administered photosensitizing drug with light of a particular wavelength to activate the photosensitizer to kill abnormal cells. To date, only a small number of photosensitizers have been clinically approved for PDT, and researchers continue to look for new molecules that have more desirable properties for clinical applications. Natural products have long been important sources of pharmaceuticals, and there is a great potential for discovery of novel chemotypes from under‐explored biodiversities in the world. The objective of this study is to mine the terrestrial plants in Sarawak, Borneo Island, for new photosensitizers for PDT. In a screening program from 2004 to 2008, we prepared and studied 2,400 extracts from 888 plants for their photosensitizing activities. This report details the bioprospecting process, preparation and testing of extracts, analysis of the active samples, fractionation of four samples, and isolation and characterization of photosensitizers.     

Precise ligand engineering of Ir(III)-based photosensitizer with aggregation-induced emission for image-guided photodynamic therapy

Photodynamic therapy (PDT), which relies on the production of reactive oxygen species (ROS) induced by a photosensitizer to kill cancer cells, has become a non-invasive approach to combat cancer. However, the conventional aggregation-caused quenching effect, as well as the low ROS generation ability of photosensitizers, restrict their biological applications. In this work, a new Ir(III) complex with a dendritic ligand has been strategically designed and synthesized by ingenious modification of the ancillary ligand of a reported Ir(III) complex ( Ir-1 ). The extended π-conjugation and multiple aromatic donor moieties endow the resulting complex Ir-2 with obvious aggregation-induced emission (AIE) activity and bathochromic emission. In in vitro experiments, importantly, Ir-2 nanoparticles exhibit the excellent photoinduced ROS generation capabilities of O₂^•− and ¹O₂, as well as excellent biocompatibility and the lipid droplets (LDs) targeting feature. This study would provide useful guidance to design efficient Ir(III)-based photosensitizers used in biological applications in the future.     

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

Photodynamic therapy (PDT) represents a promising method for treatment of cancerous tumors. The chemical and physical properties of used photosensitizer play key roles in the treatment efficacy. In this study, a novel photosensitizer, Chlorin-H [-13,15-N-(cyclohexyl)cycloimide] which displayed a characteristic long wavelength absorption peak at 698 nm was synthesized. Following flash photolysis with 355 nm laser, Chlorin-H is potent to react with O₂ and then produce ¹O₂. This finding indicates that Chlorin-H takes its effects through type II mechanism in PDT. Generally, Chlorin-H is localized in mitochondria and nucleus of cell. After light irradiation with 698 nm laser, it can kill many types of cell, inhibit cell proliferation and colony formation, suppress cancer cell invasiveness and trigger apoptosis via the mitochondrial pathway in A549 cells in vitro. In addition, Chlorin-H–PDT can destroy A549 tumor in nude mice and a necrotic scab was formed eventually. The expression levels of many genes which regulated cell growth and apoptosis were determined by RT-PCR following Chlorin-H–PDT. The results showed that it either increased or decrease. Among which, the expression level of TNFSF13, a member of tumor necrosis factor superfamily, increased significantly. Silencing of TNFSF13 caused by RNA interference decreased the susceptibility of A549 cells to Chlorin-H–PDT. In general, Chlorin-H is an effective antitumor photosensitizer in vitro and in vivo and is worthy of further study as a new drug candidate. TNFSF13 will be an important molecular target for the discovery of new photosensitizers.     

Targeting Mitochondria by Zn(II)N-Alkylpyridylporphyrins: The Impact of Compound Sub-Mitochondrial Partition on Cell Respiration and Overall Photodynamic Efficacy

Mitochondria play a key role in aerobic ATP production and redox control. They harness crucial metabolic pathways and control cell death mechanisms, properties that make these organelles essential for survival of most eukaryotic cells. Cancer cells have altered cell death pathways and typically show a shift towards anaerobic glycolysis for energy production, factors which point to mitochondria as potential culprits in cancer development. Targeting mitochondria is an attractive approach to tumor control, but design of pharmaceutical agents based on rational approaches is still not well established. The aim of this study was to investigate which structural features of specially designed Zn(II)N-alkylpyridylporphyrins would direct them to mitochondria and to particular mitochondrial targets. Since Zn(II)N-alkylpyridylporphyrins can act as highly efficient photosensitizers, their localization can be confirmed by photodamage to particular mitochondrial components. Using cultured LS174T adenocarcinoma cells, we found that subcellular distribution of Zn-porphyrins is directed by the nature of the substituents attached to the meso pyridyl nitrogens at the porphyrin ring. Increasing the length of the aliphatic chain from one carbon (methyl) to six carbons (hexyl) increased mitochondrial uptake of the compounds. Such modifications also affected sub-mitochondrial distribution of the Zn-porphyrins. The amphiphilic hexyl derivative (ZnTnHex-2-PyP) localized in the vicinity of cytochrome c oxidase complex, causing its inactivation during illumination. Photoinactivation of critical cellular targets explains the superior efficiency of the hexyl derivative in causing mitochondrial photodamage, and suppressing cellular respiration and survival. Design of potent photosensitizers and redox-active scavengers of free radicals should take into consideration not only selective organelle uptake and localization, but also selective targeting of critical macromolecular structures.     

Photodynamic treatment and H2O2-induced oxidative stress result in different patterns of cellular protein oxidation.

Photodynamic treatment (PDT) is an emerging therapeutic procedure for the management of cancer, based on the use of photosensitizers, compounds that generate highly reactive oxygen species (ROS) on irradiation with visible light. The ROS generated may oxidize a variety of biomolecules within the cell, loaded with a photosensitizer. The high reactivity of these ROS restricts their radius of action to 5-20 nm from the site of their generation. We studied oxidation of intracellular proteins during PDT using the ROS-sensitive probe acetyl-tyramine-fluorescein (acetylTyr-Fluo). This probe labels cellular proteins, which become oxidized at tyrosine residues under the conditions of oxidative stress in a reaction similar to dityrosine formation. The fluorescein-labeled proteins can be visualized after gel electrophoresis and subsequent Western blotting using the antibody against fluorescein. We found that PDT of rat or human fibroblasts, loaded with the photosensitizer Hypocrellin A, resulted in labeling of a set of intracellular proteins that was different from that observed on treatment of the cells with H2O2. This difference in labeling patterns was confirmed by 2D electrophoresis, showing that a limited, yet distinctly different, set of proteins is oxidized under either condition of oxidative stress. By matching the Western blot with the silver-stained protein map, we infer that alpha-tubulin and beta-tubulin are targets of PDT-induced protein oxidation. H2O2 treatment resulted in labeling of endoplasmic reticulum proteins. Under conditions in which the extent of protein oxidation was comparable, PDT caused massive apoptosis, whereas H2O2 treatment had no effect on cell survival. This suggests that the oxidative stress generated by PDT with Hypocrellin A activates apoptotic pathways, which are insensitive to H2O2 treatment. We hypothesize that the pattern of protein oxidation observed with Hypocrellin A reflects the intracellular localization of the photosensitizer. The application of acetylTyr-Fluo may be useful for characterizing protein targets of oxidation by PDT with various photosensitizers.     

Effect of novel porphyrazine photosensitizers on normal and tumor brain cells

Photodynamic therapy (PDT) is a clinically approved procedure for targeting tumor cells. Though several different photosensitizers have been developed, there is still much demand for novel photosensitizers with improved properties. In this study we aim to characterize the accumulation, localization and dark cytotoxicity of the novel photosensitizers developed in‐house derivatives of porphyrazines ( pz I‐IV) in primary murine neuronal cells, as well as to identify the concentrations at which pz still effectively induces death in glioma cells yet is nontoxic to nontransformed cells. The study shows that incubation of primary neuronal and glioma cells with pz I‐IV leads to their accumulation in both types of cells, but their rates of internalization, subcellular localization and dark toxicity differ significantly. Pz II was the most promising photosensitizer. It efficiently killed glioma cells while remaining nontoxic to primary neuronal cells. This opens up the possibility of evaluating pz II for experimental PDT for glioma.      

Alkylation converts riboflavin into an efficient photosensitizer of phospholipid membranes

A new decyl chain [−(CH₂)₉CH₃] riboflavin conjugate has been synthesized and investigated. A nucleophilic substitution (S_N2) reaction was used for coupling the alkyl chain to riboflavin (Rf), a model natural photosensitizer. As expected, the alkylated compound (decyl-Rf) is significantly more lipophilic than its precursor and efficiently intercalates within phospholipid bilayers, increasing its fluorescence quantum yield. The oxidative damage to lipid membranes photoinduced by decyl-Rf was investigated in large and giant unilamellar vesicles (LUVs and GUVs, respectively) composed of different phospholipids. Using a fluorogenic probe, fast radical formation and singlet oxygen generation was demonstrated upon UVA irradiation in vesicles containing decyl-Rf. Photosensitized formation of conjugated dienes and hydroperoxides, and membrane leakage in LUVs rich in poly-unsaturated fatty acids were also investigated. The overall assessment of the results shows that decyl-Rf is a significantly more efficient photosensitizer of lipids than its unsubstituted precursor and that the association to lipid membranes is key to trigger phospholipid oxidation. Alkylation of hydrophilic photosensitizers as a simple and general synthetic tool to obtain efficient photosensitizers of biomembranes, with potential applications, is discussed.     

Photodynamic therapy: shedding light on the biochemical pathways regulating porphyrin-mediated cell death

Photodynamic therapy (PDT) is a clinically approved treatment for the ocular condition age-related macular degeneration, and certain types of cancer. PDT is also under investigation for other ocular, as well as, immune-mediated and cardiovascular indications. PDT is a two step procedure. In the first step, the photosensitizer, usually a porphyrin derivative, is administered and taken up by cells. The second step involves activation of the photosensitizer with a specific wavelength of visible light. Exposure to light of an activating wavelength generates reactive oxygen species within cells containing photosensitizer. PDT with porphyrin photosensitizers induces rapid apoptotic cell death, an event which may be attributed to the close association of these compounds with mitochondria. Thus, PDT is an attractive method to treat ailments such as cancer, viral infections, autoimmune disorders and certain cardiovascular diseases in which the apoptotic program may be compromised. The present review examines the cellular events triggered at lethal and sublethal PDT doses and their relationship to the subsequent effects exerted upon cells.     

Responses of an adventitious fast‐growing plant to photodynamic stress: comparative study of anionic and cationic porphyrin effect on Arabidopsis thaliana

Antimicrobial photodynamic treatment (APDT) based on the use of a photosensitizer to produce reactive oxygen species (ROS) that induce cell death could be envisaged to fight against plant pathogens. For setting this strategy, we want to study how plants themselves respond to photodynamic treatment. In previous work we showed that tomato plantlets were able to resist photoactivated tetra (N‐methylpyridyl) porphyrin (CP) or the zinc metalated form (CP‐Zn). To enlarge our plant expertise related to exogenous porphyrins treatment and to further defend this approach, we studied how a weed like Arabidopsis thaliana responded to exogenous supply of anionic and cationic porphyrins. Both types of photosensitizers had no negative effect on seed germination and did not hamper the development etiolated Arabidopsis plantlet under dark conditions. Thus, post‐emergence effects of porphyrin photoactivation on the development of 14 day‐old in vitro Arabidopsis plantlet under light were observed. CP‐Zn was the most efficient photosensitizer to kill Arabidopsis plantlets while anionic tetra (4‐sulfonatophenyl) porphyrin only delayed their growth and development. Indeed only 7% of plantlets could be rescued after CP‐Zn treatment. Furthermore, non‐enzymatic and enzymatic defense components involved in detoxification of ROS generated by CP‐Zn under illumination were downregulated or stable with the exception of sevenfold increase in proline content. As previously demonstrated in the literature for microbial agents and in the present work for Arabidopsis, CP‐Zn was efficient enough to eradicate unwanted vegetation and plant pathogens without at the same time killing plants of agronomic interest such as tomato plantlets.     

Photodynamic therapy and some clinical applications in oncology

Photodynamic therapy (PDT), a new treatment modality for localized cancers involving the selective interaction of visible light with photosensitizers, such as hematoporphyrin derivatives (HpD) or dihematoporphyrin ether/ester (DHE) (Photofrin II). Photodynamic therapy of malignant tumors includes biological, photochemical and photophysical processes. These processes involve: (i) absorption of photosensitizing agent; (ii) selective retention of photosensitizer in tumors and (iii) irradiation of sensitized tumor by laser irradiation. This paper provides a review of photosensitizers, photochemistry, subcellular targets, side effects and lasers involved in photodynamic therapy. In addition, gradual increase in knowledge related to in vivo and in vitro mechanisms of action of PDT, as well as some clinical applications of photodynamic therapy are presented.     

Lead Structures for Applications in Photodynamic Therapy. 6. Temoporfin Anti-Inflammatory Conjugates to Target the Tumor Microenvironment for In Vitro PDT

Due to the ongoing development of clinical photodynamic therapy (PDT), the search continues for optimized photosensitizers that can overcome some of the side effects associated with this type of treatment modality. The main protagonists being: post-treatment photosensitivity, due to only limited cellular selectivity and post-treatment tumor regrowth, due to the up-regulation of pro-inflammatory agents within the tumor microenvironment. A photosensitizer that could overcome one or both of these drawbacks would be highly attractive to those engaged in clinical PDT. Certain non-steroidal anti-inflammatory drugs (NSAIDs) when used in combination with PDT have shown to increase the cytotoxicity of the treatment modality by targeting the tumor microenvironment. Temoporfin (m-THPC), the gold standard chlorin-based photosensitizer (PS) since its discovery in the 1980’s, has successfully been conjugated to non-steroidal anti-inflammatory compounds, in an attempt to address the issue of post-treatment tumor regrowth. Using a modified Steglich esterification reaction, a library of “iPorphyrins” was successfully synthesized and evaluated for their PDT efficacy.     

Cytosolic superoxide dismutase activity after photodynamic therapy, intracellular distribution of Photofrin II and hypericin, and P-glycoprotein localization in human colon adenocarcinoma

In photodynamic therapy (PDT), a tumor-selective photosensitizer is administered and then activated by exposure to a light source of applicable wavelength. Multidrug resistance (MDR) is largely caused by the efflux of therapeutics from the tumor cell by means of P-glycoprotein (P-gp), resulting in reduced efficacy of the anticancer therapy. This study deals with photodynamic therapy with Photofrin II (Ph II) and hypericin (Hyp) on sensitive and doxorubicin-resistant colon cancer cell lines. Changes in cytosolic superoxide dismutase (SOD1) activity after PDT and the intracellular accumulation of photosensitizers in sensitive and resistant colon cancer cell lines were examined. The photosensitizers' distributions indicate that Ph II could be a potential substrate for P-gp, in contrast to Hyp. We observed an increase in SOD1 activity after PDT for both photosensitizing agents. The changes in SOD1 activity show that photodynamic action generates oxidative stress in the treated cells. P-gp appears to play a role in the intracellular accumulation of Ph II. Therefore the efficacy of PDT on multidrug-resistant cells depends on the affinity of P-gp to the photosensitizer used. The weaker accumulation of photosensitizing agents enhances the antioxidant response, and this could influence the efficacy of PDT.     

Properties and applications of photodynamic therapy

Photodynamic therapy (PDT) is the treatment of malignant lesions with visible light following the systemic administration of a tumor-localizing photosensitizer. Pharmacological and photochemical properties of the photosensitizer are combined with precise delivery of laser-generated light to produce a treatment which can offer selective tumoricidal action. Hematoporphyrin derivative (HD) and a purified component called Photofrin II are currently being used in clinical PDT. Initial patient results have been encouraging, and considerable interest has developed in the synthesis and evaluation of new photosensitizers with improved photochemical and pharmacological characteristics. In addition, there has been a gradual increase in knowledge related to in vitro and in vivo mechanisms of action of PDT. This report provides an overview of the properties and applications of PDT. Information and data related to drug development, photochemistry, subcellular targets, in vivo responses, and clinical trials of PDT are presented.     

Role of mitogen‐activated protein kinase in Zn‐BC‐AM PDT‐induced apoptosis in nasopharyngeal carcinoma cells

Photodynamic therapy (PDT) with a recently developed photosensitizer Zn‐BC‐AM was found to effectively induce apoptosis in a well‐differentiated nasopharyngeal carcinoma (NPC) HK‐1 cell line. Sustained activation of p38 mitogen‐activated protein kinase (MAPK) and c‐jun N‐terminal kinase (JNK) as well as a transient increase in activation of extracellular signal‐regulated kinase (ERK) were observed immediately after Zn‐BC‐AM PDT. A commonly used p38 MAPK/JNK pharmacological inhibitor PD169316 was found to reduce PDT‐induced apoptosis of HK‐1 cells. PD169316 also prevented the loss of Bcl‐2 and Bcl‐xL in PDT‐treated HK‐1 cells. However, inhibition of JNK with SP600125 had no effect on Zn‐BC‐AM PDT‐induced apoptosis while inhibition of ERK with PD98059 or p38 MAPK with SB203580 significantly increased Zn‐BC‐AM PDT‐induced apoptosis. Further study showed that knockdown of the p38β isoform with siRNA also increased Zn‐BC‐AM PDT‐induced apoptosis, indicating that the anti‐apoptotic effect of PD169316 in PDT‐treated HK‐1 cells was probably independent of p38 MAPK or JNK activation. Taken together, the results suggest that inhibition of p38β and ERK may enhance the therapeutic efficacy of Zn‐BC‐AM PDT on NPC cells. It should be noted that data only based on the use of PD169316 should be interpreted in caution. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and biological evaluation of 173-dicarboxylethyl-pyropheophorbide-a amide derivatives for photodynamic therapy

Three novel 17³-dicarboxylethyl-pyropheophorbide-a amide derivatives as photosensitizers for photodynamic therapy (PDT) were synthesized from pyropheophorbide-a (Ppa). Their photophysical and photochemical properties, intracellular localization, photocytotoxicity in vitro and in vivo were investigated. All target compounds exhibited low cytotoxicity in the dark and remarkable photocytotoxicity against human esophageal cancer cells. Among them, 1a showed highest singlet oxygen quantum yield. Upon light activation, 1a exhibited significant photocytotoxicity. After PDT treatment, the growth of Eca-109 tumor in nude mice was significantly inhibited. Therefore, 1a is a powerful and promising antitumor photosensitizer for PDT.     

Biodistribution of photosensitizing agents

• 1.1. The features of neoplasia which predict for drug responsiveness are rapid growth and/or inefficient repair of damage, especially to DNA.
• 2.2. PDT has the advantage of yielding responses regardless of the growth fraction of a tumor, and repair appears to play only a minor role.
• 3.3. While an entirely different spectrum of tumors can be targeted with PDT, the perhaps unavoidable accompaniment is that a new set of rules for efficacy will need to be established.
• 4.4. The selectivity of PDT is based on the need for irradiation which can be directed, along with the short tissue half-life of the cytotoxic product, singlet oxygen. Sensitizers which target specific cellular organelles could promote PDT efficacy, if in vitro data (Woodbum et at., 1992b Photochem. Photobiol. 55, 697–704) can be translated into clinical practice.
• 5.5. It remains to be established whether total drug distribution to neoplastic tissues or concentration in specific sub-cellular sites is the more important factor.
• 6.6. Questions relating to the role of biodistribution as a factor in efficacy of PDT sensitizers of photosensitizers remain to be explored. Just as the political cartographers are grappling with changes in territorial boundaries of known lands, we continue to clarify the rules relating to PDT boundaries. In this regard, it is clearly important for determinants of pharmacokinetics and biodistribution to be evaluated and understood.
• 7.7. Once clinical reports on the “second generation” agents are published, we may get a better picture, although it is not unusual for clinical reports to raise more questions than they answer.
• 8.8. It seems safe to conclude that there is nothing “magic” about HPD, and that additional efficacious photosensitizers for PDT can be produced.
• 9.9. If we find that a wide variety of different structures are useful in the clinic, a likely conclusion is that there are multiple mechanisms of tumor localization. Since the nature of neoplasia is so diverse, this possibility should not be surprising.
• 10.10. In view of the finding, cited above, that liposomes show about the same degree of tumor selectivity as does Photofrin, it may be feasible to target any efficient photosensitizer for neoplastic tissues by development of an appropriate delivery system.

     

Photodynamic Therapy in Pythium insidiosum – An In Vitro Study of the Correlation of Sensitizer Localization and Cell Death

Pythiosis is an infectious disease caused by Pythium insidiosum, a fungus-like organism. Due to the lack of ergosterol on its cell membrane, antibiotic therapy is ineffective. The conventional treatment is surgery, but lesion recurrence is frequent, requiring several resections or limb amputation. Photodynamic therapy uses photo-activation of drugs and has the potential to be an attractive alternative option. The in vitro PDT response on the growing of Pythium insidiosum culture was investigated using three distinct photosensitizers: methylene blue, Photogem, and Photodithazine. The photosensitizer distribution in cell structures and the PDT response for incubation times of 30, 60, and 120 minutes were evaluated. Methylene blue did not penetrate in the pathogen''s cell and consequently there was no PDT inactivation. Photogem showed heterogenous distribution in the hyphal structure with small concentration inside the cells. Porphyrin-PDT response was heterogenous, death and live cells were observed in the treated culture. After 48 hours, hyphae regrowth was observed. Photodithazine showed more homogenous distribution inside the cell and with the specific intracellular localization dependent on incubation time. Photodithazine first accumulates in intracellular vacuoles, and at incubation times of one hour, it is located at all cell membranes. Higher inhibition of the growing rates was achieved with Photodithazine -PDT, over 98%. Our results showed that the photosensitizers that cross more efficiently the Pythium insidiosum membranes are able to cause extensive damage to the organism under illumination and therefore, are the best options for clinical treatment.     

Major determinants of photoinduced cell death: Subcellular localization versus photosensitization efficiency

We present a study on whether and to what extent subcellular localization may compete favorably with photosensitization efficiency with respect to the overall efficiency of photoinduced cell death. We have compared the efficiency with which two cationic photosensitizers, namely methylene blue (MB) and crystal violet (CV), induce the photoinduced death of human cervical adenocarcinoma (HeLa) cells. Whereas MB is well known to generate singlet oxygen and related triplet excited species with high quantum yields in a variety of biological and chemical environments (i.e., acting as a typical type II photosensitizer), the highly mitochondria-specific CV produces triplet species and singlet oxygen with low yields, acting mostly via the classical type I mechanism (e.g., via free radicals). The findings described here indicate that the presumably more phototoxic type II photosensitizer (MB) does not lead to higher degrees of cell death compared to the type I (CV) photosensitizer. In fact, CV kills cells with the same efficiency as MB, generating at least 10 times fewer photoinduced reactive species. Therefore, subcellular localization is indeed more important than photochemical reactivity in terms of overall cell killing, with mitochondrial localization representing a highly desirable property for the development of more specific/efficient photosensitizers for photodynamic therapy applications.     

Fluorescence characterisation of multiply-loaded anti-HER2 single chain Fv-photosensitizer conjugates suitable for photodynamic therapy.

We report the synthesis, spectroscopic properties and intracellular imaging of recombinant antibody single chain fragment (scFv) conjugates with photosensitizers used for photodynamic therapy of cancer (PDT). Two widely-studied photosensitizers have been selected: preclinical pyropheophorbide-a (PPa) and verteporfin (VP), which has been clinically approved for the treatment of acute macular degeneration (Visudyne). Pyropheophorbide-a and verteporfin have been conjugated to an anti-HER2 scFv containing on average ten photosensitizer molecules per scFv with a small contribution (相似文献