Current states and future views in photodynamic therapy

On the population of triplet states of 2-seleno-thymine

The population and depopulation mechanisms leading to the lowest-lying triplet states of 2-Se-Thymine were studied at the MS-CASPT2/cc-pVDZ level of theory. Several critical points on different potential energy hypersurfaces were optimized, including minima, conical intersections, and singlet-triplet crossings. The accessibility of all relevant regions on the potential energy hypersurfaces was investigated by means of minimum energy paths and linear interpolation in internal coordinates techniques. Our analysis indicates that, after the population of the bright S2 state in the Franck-Condon region, the first photochemical event is a barrierless evolution towards one of its two minima. After that, three viable photophysical deactivation paths can take place. In one of them, the population in the S2 state is transferred to the T2 state via intersystem crossing and subsequently to the T1 state by internal conversion. Alternatively, the S1 state could be accessed by internal conversion through two distinct conical intersections with S2 state followed by singlet-triplet crossing with the T2 state. The absence of a second minimum on the T1 state and a small energy barrier on pathway along the potential energy surface towards the ground state from the lowest triplet state are attributed as potential reasons to explain why the lifetime of the triplet state of 2-Se-Thymine might be reduced in comparison with its thio-analogue.

Current Advances in Black Phosphorus-Based Drug Delivery Systems for Cancer Therapy

Cancer has been one of the major threats to the lives of human beings for centuries. Traditional therapy is more or less faced with certain defects, such as poor targeting, easy degradation, high side effects, etc. Therefore, in order to improve the treatment efficiency of drugs, an intelligent drug delivery system (DDS) is considered as a promising solution strategy. Due to their special structure and large specific surface area, 2D materials are considered to be a good platform for drug delivery. Black phosphorus (BP), as a new star of the 2D family, is recommended to have the potential to construct DDS by virtue of its outstanding photothermal therapy (PTT), photodynamic therapy (PDT), and biodegradable properties. This tutorial review is intended to provide an introduction of the current advances in BP-based DDSs for cancer therapy, which covers topics from its construction, classified by the types of platforms, to the stimuli-responsive controlled drug release. Moreover, their cancer therapy applications including mono-, bi-, and multi-modal synergistic cancer therapy as well as the research of biocompatibility are also discussed. Finally, the current status and future prospects of BP-based DDSs for cancer therapy are summarized.

Theoretical investigation on bisarylselanylbenzo-2,1,3-selenadiazoles as potential photosensitizers in photodynamic therapy

Density functional theory and time-dependent (TDDFT) calculations were carried out for recently reported bisarylselanylbenzo-2,1,3-selenadiazoles derivatives capable of producing singlet oxygen (¹O₂) under UV-Vis irradiation. Conformational behaviors, excitation energies, singlet-triplet energy gaps, and spin-orbit coupling constants were evaluated. The conformational analysis evidences that two different conformers have to be taken into consideration to completely describe the photophysical properties of this class of molecules. TDDFT results show that these compounds, though possessing absorption wavelengths that fall in the violet region, are characterized by singlet-triplet energy gaps greater than the energy required to excite the molecular oxygen, thus being able to produce the cytotoxic species, spin-orbit coupling constants large enough to ensure efficient singlet-triplet intersystem spin crossing, and even the highly reactive superoxide anion O₂ ^•(-) by autoionization and subsequent electron transfer to molecular oxygen in its ground state.

The effect of two porphyrine photosensitizers TMPyP and ZnTPPS4 for application in photodynamic therapy of cancer cells in vitro

Photodynamic therapy (PDT) is one of the treatments for cancer. This therapy uses a combination of a photosensitizer (PS), light irradiation, and oxygen O₂, which is converted to cytotoxic ¹O₂ and other forms of reactive oxygen species (ROS), causing selective damage to the target tissue. In this work, we studied effect of two porphyrin photosensitizers TMPyP and ZnTPPS₄ at three different concentrations (0.25, 0.5, 5μM) after two irradiation doses (5 and 25 J/cm²). Photodynamic efect of TMPyP and ZnTPPS₄ were confirmed by a battery of in vitro tests including MTT, reactive oxygen species (ROS) production and mitochondrial membrane potential test (MMP). Morphological changes of the cells before and after treatment were imaged by atomic force microscopy (AFM). The most effective combination of irradiation dose and concentration for both PSs showed a concentration of 5 μM and a irradiation dose of 25 J/cm² in both cell cultures.

Peptide-targeted dendrimeric prodrugs of 5-aminolevulinic acid: A novel approach towards enhanced accumulation of protoporphyrin IX for photodynamic therapy

Photodynamic therapy (PDT) is a promising approach for the targeted treatment of cancer and various other human disorders. An effective, clinically approved approach in PDT involves the administration of 5-aminolevulinic acid (ALA) to generate elevated levels of the natural photosensitiser protoporphyrin IX (PpIX). The development of prodrugs of ALA is of considerable interest as a means to enhance the efficiency and cell selectivity of PpIX accumulation for PDT applications. In this work a novel peptide-targeted dendrimeric prodrug of 5-aminolevulinic acid (ALA) 13 was synthesised which displays nine copies of ALA on a core structure that is linked to a homing peptide for targeted delivery to a specific cancer cell type. The synthesis was accomplished effectively via a flexible, modular solid phase and solution phase route, using a combination of solid phase peptide synthesis and copper-catalysed azide-alkyne cycloaddition chemistry. The prodrug system shows a sustained and enhanced production of protoporphyrin IX (PpIX) in the MDA-MB-231 cell line that over-expresses the epidernal growth factor receptor (EGFR+) in comparison to equimolar ALA and the corresponding non-targeted ALA dendrimer (nine copies of ALA). This study provides a proof of concept for the development of a new generation of prodrugs for ALA-based photodynamic therapy that can deliver an enhanced ALA payload to specific tissue types.

Hypericin-mediated photodynamic therapy for the treatment of cancer: a review

OBJECTIVES

Hypericin is a polycyclic aromatic naphthodianthrone that occurs naturally. It is also an active ingredient in some species of the genus Hypericum. Emerging evidence suggests that hypericin has attracted great attention as a potential anticancer drug and exhibits remarkable antiproliferative effect upon irradiation on various tumour cells. This paper aims to summarise the anticancer effect and molecular mechanisms modulated by hypericin-medicated photodynamic therapy and its potential role in the cancer treatment.

KEY FINDINGS

Hypericin-medicated photodynamic therapy could inhibit the proliferation of various tumour cells including bladder, colon, breast, cervical, glioma, leukaemia, hepatic, melanoma, lymphoma and lung cancers. The effect is primarily mediated by p38 mitogen-activated protein kinase (MAPK), JNK, PI3K, CCAAT-enhancer-binding protein homologous protein (CHOP)/TRIB3/Akt/mTOR, TRAIL/TRAIL-receptor, c-Met and Ephrin-Eph, the mitochondria and extrinsic signalling pathways. Furthermore, hypericin-medicated photodynamic therapy in conjunction with chemotherapeutic agents or targeted therapies is more effective in inhibiting the growth of tumour cells.

SUMMARY

During the past few decades, the anticancer properties of photoactivated hypericin have been extensively investigated. Hypericin-medicated photodynamic therapy can modulate a variety of proteins and genes and exhibit a great potential to be used as a therapeutic agent for various types of cancer.

Photodynamic activity of 2,6-dibrominated dimethylaminophenylbuta-1,3-dienylBODIPY dyes

Mono- and disubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes were successfully prepared, and their in vitro photodynamic activities against MCF-7 breast cancer cells were evaluated with a Thorlabs M660L4 660 nm LED (336 J · cm[Formula: see text]. The IC[Formula: see text] value of the monophenylbuta-1,3-dienylBODIPY was ca. 2.1 [Formula: see text]M, while that of the diphenylbuta-1,3-dienylBODIPY was > 50 [Formula: see text]M. Both dyes exhibited minimal dark toxicity. The results demonstrate that monosubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes merit further in-depth study for use as photosensitizer dyes in photodynamic therapy.

Theoretical insights on type I/II photoreactions of potential Zn(II) polypyridyl photosensitizers for two-photon photodynamic therapy

Large two-photon absorption cross-sections are vital to photosensitizers (PSs) in TP-PDT, which can be used to develop in-depth treatment for diseased cells and minimize the harm to surrounding cells. Here, we conduct a study about photophysical properties of one Ru(II) polypyridyl complex and two designed Zn(II) polypyridyl complexes by means of DFT and TD-DFT methods. The main results are as follows: firstly, the two-photon absorption spectrum of two designed complexes Zn-OMe and Zn-OCOOCH₃ are all within the phototherapeutic window (550-900 nm). Secondly, large SOC values and small energy gaps ΔE_S-T of these complexes guarantee the efficiency of ISC process. Thirdly, their T₁ energy is greater than that required for generating ¹O₂ (0.98 eV) via Type II photoreaction. In addition, the calculated results of vertical electron affinities (VEA) and vertical ionization potentials (VIP) show that these complexes are able to form superoxide ions O₂^(-) via Type I photoreaction. Specifically, both of two designed Zn-centric complexes have larger TPA cross-sections than that of Ru-centric complex. In a word, we are pleased to report two potential photosensitizers with excellent performance and reasonable price for Type I/II photoreactions. We expect our study will offer some theoretical guidance and help in TP-PDT.

Biophysical Characterization and Anticancer Activities of Photosensitive Phytoanthraquinones Represented by Hypericin and Its Model Compounds

Photosensitive compounds found in herbs have been reported in recent years as having a variety of interesting medicinal and biological activities. In this review, we focus on photosensitizers such as hypericin and its model compounds emodin, quinizarin, and danthron, which have antiviral, antifungal, antineoplastic, and antitumor effects. They can be utilized as potential agents in photodynamic therapy, especially in photodynamic therapy (PDT) for cancer. We aimed to give a comprehensive summary of the physical and chemical properties of these interesting molecules, emphasizing their mechanism of action in relation to their different interactions with biomacromolecules, specifically with DNA.

Chemical approaches for the enhancement of porphyrin skeleton-based photodynamic therapy

With the development of photodynamic therapy (PDT), remarkable studies have been conducted to generate photosensitisers (PSs), especially porphyrin PSs. A variety of chemical modifications of the porphyrin skeleton have been introduced to improve cellular delivery, stability, and selectivity for cancerous tissues. This review aims to highlight the developments in porphyrin-based structural modifications, with a specific emphasis on the role of PDT in anticancer treatment and the design of PSs to achieve a synergistic effect on multiple targets.

2-Naphthol Moiety of Neocarzinostatin Chromophore as a Novel Protein-Photodegrading Agent and Its Application as a H2 O2 -Activatable Photosensitizer

A 2-naphthol derivative 2 corresponding to the aromatic ring moiety of neocarzinostatin chromophore was found to degrade proteins under photo-irradiation with long-wavelength UV light without any additives under neutral conditions. Structure-activity relationship studies of the derivative revealed that methylation of the hydroxyl group at the C2 position of 2 significantly suppressed its photodegradation ability. Furthermore, a purpose-designed synthetic tumor-related biomarker, a H₂ O₂ -activatable photosensitizer 8 possessing a H₂ O₂ -responsive arylboronic ester moiety conjugated to the hydroxyl group at the C2 position of 2, showed significantly lower photodegradation ability compared to 2. However, release of the 2 from 8 by reaction with H₂ O₂ regenerated the photodegradation ability. Compound 8 exhibited selective photo-cytotoxicity against high H₂ O₂ -expressing cancer cells upon irradiation with long-wavelength UV light.

The Assessment of the Combined Treatment of 5-ALA Mediated Photodynamic Therapy and Thalidomide on 4T1 Breast Carcinoma and 2H11 Endothelial Cell Line

Photodynamic therapy (PDT) is a low-invasive method of treatment of various diseases, mainly neoplastic conditions. PDT has been experimentally combined with multiple treatment methods. In this study, we tested a combination of 5-aminolevulinic acid (5-ALA) mediated PDT with thalidomide (TMD), which is a drug presently used in the treatment of plasma cell myeloma. TMD and PDT share similar modes of action in neoplastic conditions. Using 4T1 murine breast carcinoma and 2H11 murine endothelial cells lines as an experimental tumor model, we tested 5-ALA-PDT and TMD combination in terms of cytotoxicity, apoptosis, Vascular Endothelial Growth Factor (VEGF) expression, and, in 2H11 cells, migration capabilities by wound healing assay. We have found an enhancement of cytotoxicity in 4T1 cells, whereas, in normal 2H11 cells, this effect was not statistically significant. The addition of TMD decreased the production of VEGF after PDT in 2H11 cell line. Our results reveal enhanced effectiveness of 5-ALA-PDT with TMD treatment compared to 5-ALA-PDT or TMD treatment alone. The addition of TMD may be a promising proceeding of the anti-tumor effect of PDT by decreasing the VEGF concentration in the culture medium. Further studies, including testing on different cell lines, are needed to confirm this assumption.

Progress in Clinical Trials of Photodynamic Therapy for Solid Tumors and the Role of Nanomedicine

Current research to find effective anticancer treatments is being performed on photodynamic therapy (PDT) with increasing attention. PDT is a very promising therapeutic way to combine a photosensitive drug with visible light to manage different intense malignancies. PDT has several benefits, including better safety and lower toxicity in the treatment of malignant tumors over traditional cancer therapy. This reasonably simple approach utilizes three integral elements: a photosensitizer (PS), a source of light, and oxygen. Upon light irradiation of a particular wavelength, the PS generates reactive oxygen species (ROS), beginning a cascade of cellular death transformations. The positive therapeutic impact of PDT may be limited because several factors of this therapy include low solubilities of PSs, restricting their effective administration, blood circulation, and poor tumor specificity. Therefore, utilizing nanocarrier systems that modulate PS pharmacokinetics (PK) and pharmacodynamics (PD) is a promising approach to bypassing these challenges. In the present paper, we review the latest clinical studies and preclinical in vivo studies on the use of PDT and progress made in the use of nanotherapeutics as delivery tools for PSs to improve their cancer cellular uptake and their toxic properties and, therefore, the therapeutic impact of PDT. We also discuss the effects that photoimmunotherapy (PIT) might have on solid tumor therapeutic strategies.

Theoretical exploration of the photophysical properties of two-component RuII-porphyrin dyes as promising assemblies for a combined antitumor effect

Due to the extraordinary success of porphyrins in photodynamic therapy (PDT) and Ru compounds as chemotherapeutics, a series of RuII-porphyrin complexes have recently been synthesized and proposed as promising dual-action therapeutic agents. The results of a careful DFT and TDDFT investigation on four mononuclear pyridyl triphenylporphyrin RuII-arene complexes are herein reported and compared with those obtained for the metal-free derivatives. The investigation aims at shedding light on the modulation of the photophysical properties of the light absorber upon metalation and exploring the hydrolysis process of the RuII-moiety in the presence of the bulky porphyrin unit. Type I and Type II photoreactions were analyzed computing absorption spectra, singlet-triplet energy gaps, spin orbit coupling constants and vertical electron affinity (VEA) along with ionization potentials (VIP) for all the investigated compounds, while the chloride/water exchange reaction kinetics were determined by exploring the first and second aquation reactions of the Ru-moiety. Despite the highly similar photophysical properties displayed by the members of this class of compounds, an analysis of the hydrolysis processes in the dark allows to point out an interesting difference related to the type of pyridylporphyrin isomer and could be a preliminary explanation of the greater phototoxicity experimentally found for 3'-pyridyl substituted compounds.

Targeting Mitochondrial Singlet Oxygen Dynamics Offers New Perspectives for Effective Metabolic Therapies of Cancer

The occurrence of mitochondrial respiration has allowed evolution toward more complex and advanced life forms. However, its dysfunction is now also seen as the most probable cause of one of the biggest scourges in human health, cancer. Conventional cancer treatments such as chemotherapy, which mainly focus on disrupting the cell division process, have shown being effective in the attenuation of various cancers but also showing significant limits as well as serious sides effects. Indeed, the idea that cancer is a metabolic disease with mitochondria as the central site of the pathology is now emerging, and we provide here a review supporting this "novel" hypothesis re-actualizing past century Otto Warburg's thoughts. Our conclusion, while integrating literature, is that mitochondrial activity and, in particular, the activity of cytochrome c oxidase, complex IV of the ETC, plays a fundamental role in the effectiveness or non-effectiveness of chemotherapy, immunotherapy and probably radiotherapy treatments. We therefore propose that cancer cells mitochondrial singlet oxygen (¹O₂) dynamics may be an efficient target for metabolic therapy development.

Improved water solubility and photodynamic activity of hydroxy-modified porphyrins by complexation with cyclodextrin

Porphyrin derivatives with hydroxyphenyl or dihydroxyphenyl moieties in the meso-position were able to dissolve in water by complexation with two trimethyl-β-cyclodextrins (TMe-β-CDxs) without further chemical modification of porphyrins or addition of dimethyl sulfoxide as a co-solvent. TMe-β-CDx-complexed tetra(hydroxyphenyl)porphyrins (THPPs) with phenols in meso-positions have a much higher photodynamic activity than TMe-β-CDx-complexed tetrakis(dihydroxyphenyl)porphyrins (TDHPPs) with dihydroxyphenyl in the meso-position. The main reason for the different photoactivity is due to the intracellular uptakes of these complexes. Thus phenols in meso-positions of porphyrin derivatives in the complexes were recognized by HeLa cell receptors. Furthermore, the photodynamic activity of TMe-β-CDx-complexed THPP was much higher than that of THPP injected as a dimethyl sulfoxide solution.

Discovery of a Monoiodo Aza-BODIPY Near-Infrared Photosensitizer: in vitro and in vivo Evaluation for Photodynamic Therapy

Photodynamic therapy (PDT) as a rising platform of the cancer treatment method is receiving increased attention. Through systematic evaluation of halogen substitution on aza-4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY), we have found that monoiodo-derived aza-BODIPYs provided greater efficacy than other halogenated aza-BODIPY PSs. 4 and 15 as monoiodinated aza-BODIPY dyes containing p-methoxyphenyl moiety were identified to be potent NIR aza-BODIPY-type PSs with IC₅₀ values against HeLa cells at a light dose of 54 J/cm² as low as 76 and 81 nM, respectively. 4 possessed superior phototoxicity, low dark toxicity, and good thermal/photostability and distributed majorly in mitochondria in cells. Apoptosis was verified to be the main cell death pathway, and in vitro reactive oxygen species generation was demonstrated. In vivo whole-body fluorescence imaging and ex vivo organ distribution studies suggested that 4 afforded an excellent PDT effect with a low drug dose under single-time light irradiation and revealed advantages over known PSs of ADPM06 and Ce6.

Photophysics and visible light photodissociation of supramolecular meso-tetra(4-pyridyl) porphyrin/RuCl2(CO)(PPh3)2 structures

In the last decades, supramolecular structures have been explored in many technological efforts. One example of such supramolecules is attained when ruthenium complexes are attached in the outer sites of a porphyrin. Ruthenium complexes act as modulators of the photophysical processes of macrocyclic molecules. Besides the investigation of the main changes introduced by the ruthenium complexes in the electronic and vibronic properties, and in the excited state deactivation processes of porphyrins, discussions concerning the photostability of these supramolecules are much needed. Here, we investigate the supramolecular free-base meso-tetra(4-pyridyl) porphyrin decorated with "RuCl₂(CO)(PPh₃)₂" ruthenium species linked at each of its (4-pyridyl) moieties. The modifications in the photophysical processes introduced by the metallic outlying species are discussed and our results suggest an energy transfer process from the porphyrin B-band to the ruthenium complex MLCT-band. The demonstration of visible light photodissociation of the supramolecule, via both pulsed and continuous laser, is also addressed.

Bioorthogonal Turn-On BODIPY-Peptide Photosensitizers for Tailored Photodynamic Therapy

Photodynamic therapy (PDT) leads to cancer remission via the production of cytotoxic species under photosensitizer (PS) irradiation. However, concomitant damage and dark toxicity can both hinder its use. With this in mind, we have implemented a versatile peptide-based platform of bioorthogonally activatable BODIPY-tetrazine PSs. Confocal microscopy and phototoxicity studies demonstrated that the incorporation of the PS, as a bifunctional module, into a peptide enabled spatial and conditional control of singlet oxygen (1 O2 ) generation. Comparing subcellular distribution, PS confined in the cytoplasmic membrane achieved the highest toxicities (IC50 =0.096±0.003 μm) after activation and without apparent dark toxicity. Our tunable approach will inspire novel probes towards smart PDT.

Monitoring PDT effects in basal cell carcinoma treatment using thermal imaging

BACKGROUND

One of the most frequent type of malignant skin lesion (almost 95 percent of all skin tumours) is basal cell carcinoma (BCC). It is often treated by radiotherapy using ionizing radiation as well by photodynamic therapy (PDT) which is a selective method directed only on cancer cells and well tolerated by patients.

MATERIALS AND METHODS

Eight male patients of the Department and Clinic of Internal Diseases, Angiology and Physical Medicine in Bytom, Medical University of Silesia, in Katowice, Poland suffering from basal cell carcinoma were monitored by thermovision during the photodynamic therapy. All lesions were diagnosed as superficial were confirmed by histopathological examination.

RESULTS

The dynamics of changes observed in the isotherm area during the therapy can provide physicians with additional information. The significant increase of observed isotherm area in comparison to the lesion area diagnosed by a physician was confirmed, which may be connected with the increased metabolism processes occurring in the tissue surrounded the lesion.

CONCLUSION

The obtained results based on the temperature gradient changes in the lesion vicinity area may bring some new information describing the range of biochemical and physiological processes occurring during photodynamic therapy.

Self-Assembly of Porphyrin-Containing Metalla-Assemblies and Cancer Photodynamic Therapy

In this report, we describe the synthesis of two porphyrin-containing Pt(II) supramolecular assemblies via coordination-driven self-assembly. X-ray crystallographic analysis on one assembly reveals that the metalla-assembly formation imposes large interchromophore distances, leading to a higher 1O2 generation efficiency, relative to the corresponding small molecular precursors. The metalla-assemblies were examined as photosensitizers for photodynamic therapy as the potential reduction of the unfavorable self-aggregation phenomenon. In vivo and in vitro investigations demonstrate that the metalla-assemblies exhibit enhanced anticancer activity with minimal dose requirement and side effects comparable to the small molecule precursors. Thus, our work demonstrates that self-assembly provides a promising methodology for enhancing the therapeutic effectiveness of anticancer agents.

Synthesis of Water-Soluble Thioglycosylated trans-A2B2 Type Porphyrins: Cellular Uptake Studies and Photodynamic Efficiency

The synthesis of water-soluble thioglycosylated A₂B₂ type porphyrins and their zinc(II) complexes is reported. The water-soluble trans-A₂B₂ porphyrins were synthesized in two steps, via [2+2] condensation between thioglycosylated dipyrromethanes and aromatic aldehydes in 15-21% yields. The thioglycosylated trans-A₂B₂ porphyrins showed decent in vitro singlet oxygen generation, which was supported by the intracellular DCFDA study. The in vitro cellular investigations of thioglycosylated A₂B₂ porphyrins were carried out in lung cancer cells (A549) to test their photodynamic therapeutic (PDT) activity. The PDT study revealed significant cytotoxicities of porphyrins with IC₅₀ values between 23.3 and 44.2 μM in the dark, whereas, after visible light exposure, the photosensitizers exhibited IC₅₀ values around 11.1-23.8 μM. The water-soluble thioglycosylated zinc(II) porphyrins having two meso-N-butylcarbazole groups exhibited an excellent degree of photocytotoxicity (IC₅₀ = 4.6-8.8 μM). The flow cytometry analysis revealed that cellular uptake and ROS (reactive oxygen species) generation efficiency of water-soluble thioglycosylated zinc(II) porphyrins were considerably higher than nonmetalated porphyrins. Confocal microscopy images displayed substantial distribution in the endoplasmic reticulum with partial colocalization in mitochondria and lysosomes of water-soluble thioglycosylated zinc(II) porphyrins in A549 cells.

Boto R, Ferreira D, R. Fernandes J, Almeida P, F. V. Ferreira L, Silva AM, V. Reis L. Red and Near-Infrared Absorbing DicyanomethyleneSquaraine Cyanine Dyes: PhotophysicochemicalProperties and Anti-Tumor Photosensitizing Effects

Photodynamic therapy is a medical modality developed for the treatment of several diseases of oncological and non-oncological etiology that requires the presence of a photosensitizer, light and molecular oxygen, which combined will trigger physicochemical reactions responsible for reactive oxygen species production. Given the scarcity of photosensitizers that exhibit desirable characteristics for its potential application in this therapeutic strategy, the main aims of this work were the study of the photophysical and photochemical properties and the photobiological activity of several dicyanomethylene squaraine cyanine dyes. Thus, herein, the study of their aggregation character, photobleaching and singlet oxygen production ability, and the further application of the previously synthesized dyes in Caco-2 and HepG2 cancer cell lines, to evaluate their phototherapeutic effects, are described. Dicyanomethylene squaraine dyes exhibited moderate light-stability and, despite the low singlet oxygen quantum yields, were a core of dyes that exhibited relevant in vitro photodynamic activity, as there was an evident increase in the toxicity of some of the tested dyes exclusive to radiation treatments.

A non-aggregated silicon(IV) phthalocyanine-lactose conjugate for photodynamic therapy

To develop a highly efficient photosensitizer for photodynamic therapy (PDT), we have designed and synthesized a phthalocyanine-lactose conjugate (Pc-Lac) through axial modification of silicon(IV) phthalocyanine with lactose moieties. With the lactose substituents, Pc-Lac is highly hydrophilic and non-aggregated with efficient reactive oxygen species (ROS) generation in aqueous media. With these desirable properties, Pc-Lac shows high photocytotoxicity and cellular uptake toward HepG2 cells. In addition, in vivo fluorescence imaging shows that Pc-Lac could selectively remain at tumor site, leading to its enhanced photodynamic efficacy against H22 tumor-bearing mice. Therefore, Pc-Lac shows a great potential as a highly efficient molecular photosensitizer for PDT.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.

miR-7112-3p targets PERK to regulate the endoplasmic reticulum stress pathway and apoptosis induced by photodynamic therapy in colorectal cancer CX-1 cells

BACKGROUND

Colorectal cancer (CRC) is the third most common malignant tumor worldwide. Photodynamic therapy (PDT) is an emerging modality for the treatment of solid tumors. Sinoporphyrin sodium (DVDMS) is a new photosensitizer with good therapeutic killing effects on cancer cells. Recent findings have shown that microRNAs play important roles in many biological processes. However, the functions of microRNAs in DVDMS-induced PDT remain largely unclear.

MATERIALS AND METHODS

Proteins involved in endoplasmic reticulum (ER) stress and apoptosis of CX-1 cells treated with DVDMS-PDT were examined by Western blotting and cell viability assays. 15 candidate miRNAs targeting RNA-dependent protein kinase-like ER kinase (PERK) were screened and verified using the TargetScan, miRWalk and miRDB databases. The downstream pathways of candidate miRNAs with high scores were studied by cell transfection, qRT-PCR, Western blotting and dual-luciferase reporter assays. The subcellular location of DVDMS was confirmed by laser confocal microscopy.

RESULTS

DVDMS-PDT induced apoptosis via elevated ER stress and activation of the PERK/ATF4/CHOP/caspase cascade pathway in CX-1 cells. The endoplasmic reticulum was involved in the subcellular accumulation of DVDMS in CX-1 cells. Dual-luciferase reporting experiment confirmed that a direct crosslinking between miR-7112-3p and PERK. In addition, miR-7112-3p was highly expressed in CRC tissues compared with peripheral tissues.

CONCLUSION

Our work showed that miR-7112-3p directly targeted PERK and further regulated PERK/ATF4/CHOP/caspase cascade pathway, resulting in enhanced apoptosis in CX-1 cells treated with DVDMS-PDT.

Nanoparticle-based drug delivery systems for controllable photodynamic cancer therapy

Compared with the traditional treatment, photodynamic therapy (PDT) in the treatment of malignant tumors has the advantages of less damage to normal tissues, quick therapeutic effect, and ability to repeat treatments to the same site. However, most of the traditional photosensitizers (PSs) have severe skin photosensitization, poor tumor targeting, and low therapeutic effect in hypoxic tumor environment, which limit the application of PDT. Nanoparticle-based drug delivery systems can improve the targeting of PSs and release drugs with controllable photoactivity at predetermined locations, so as to achieve desired therapeutic effects with minimal side-effects. The present review summarizes the current nanoparticle platforms for PDT, and offers the description of different strategies including tumor-targeted delivery, controlled-release of PSs and the triggered photoactivity to achieve controllable PDT by nanoparticle-based drug delivery systems. The challenges and prospects for further development of intelligent PSs for PDT are also discussed.

Singlet oxygen generation of subphthalocyanine-fused dimer and trimer

Subphthalocyanine (SubPc) macrocycles are known as an interesting class of nonplanar aromatic dyes. Despite documented high fluorescence and singlet oxygen quantum yields, the properties of SubPcs in photodynamic therapy (PDT) are underestimated, because their absorption bands do not reach a significant wavelength range. With this in mind, we combined a SubPc ring and a SubPc ring by introducing a common benzene ring and obtained a SubPc dimer (2) and trimer (3) with the Q-band at the near-IR region, owing to the expansion of the [Formula: see text] electron conjugated system. In this study, we reported1O2generation abilities of 2 and 3based on the applied absolute singlet oxygen quantum yields ([Formula: see text]absolute). Subsequent research revealed that 2 and 3 showed the potential to generate1O2to not only in toluene but also in DMSO. Although the photocytotoxicity of 2 and 3 were investigated upon photo-irradiation with a low light dose of approximately 1.5 J/cm2, 2 and 3 showed almost negligible toxic properties toward HEp2 cells.

Highly Efficient Singlet Oxygen Generators Based on Ruthenium Phthalocyanines: Synthesis, Characterization and in vitro Evaluation for Photodynamic Therapy

The synthesis of ruthenium(II) phthalocyanines (RuPcs) endowed with one carbohydrate unit-that is, glucose, galactose and mannose-and a dimethylsulfoxide (DMSO) ligand at the two axial coordination sites, respectively, is described. Two series of compounds, one unsubstituted at the periphery, and the other one bearing eight PEG chains at the isoindole meta-positions, have been prepared. The presence of the axial DMSO unit significantly increases the phthalocyanine singlet oxygen quantum yields, related to other comparable RuPcs. The compounds have been evaluated for PDT treatment in bladder cancer cells. In vitro studies have revealed high phototoxicity for RuPcs unsubstituted at their periphery. The phototoxicity of PEG-substituted RuPcs has been considerably improved by repeated light irradiation. The choice of the axial carbohydrate introduced little differences in the cellular uptake for both series of photosensitizers, but the phototoxic effects were considerably higher for compounds bearing mannose units.

Hypoxia-Selective Dissociation Mechanism of a Nitroimidazole Nucleoside in a DNA Environment

Photodynamic therapy is a promising approach to treat a variety of superficial tumors and other diseases. One of its major limitations arises from its dependence on molecular oxygen, which decreases the efficiency of the therapy in hypoxia conditions commonly developed by solid tumors. The present contribution reveals the molecular mechanism of a modified thymine bearing a nitroimidazole substituent, a photosensitizer able to produce highly harmful interstrand cross-links in the DNA double strand after irradiation selectively in absence of oxygen. The mechanism is resolved at a fully atomistic and electronic level relying on quantum mechanics (CASPT2, coupled-cluster, DFT, and TD-DFT methods), classical molecular dynamics, and advanced biased QM/MM simulations, revealing an energy penalty of ∼8 kcal/mol for the anionic nitromidazole release. Our findings indicate that the global interstrand cross-link production is driven by a combination of multiple factors, namely, the reverse energy penalty, the diffusion of the nitroimidazole anion, and the further reactivity of the formed thymine radical. On the basis of these results, we also suggest some possible strategies to improve the efficiency of interstrand cross-link production.

Size-Tunable Targeting-Triggered Nanophotosensitizers Based on Self-Assembly of a Phthalocyanine-Biotin Conjugate for Photodynamic Therapy

Self-assembled phototheranostic nanomaterials used for photodynamic therapy (PDT) have attracted increasing attention owing to their several advantages. Herein, we developed a novel strategy for size-tunable self-assembled nanophotosensitizers for PDT through a simple method. A series of switchable self-assembled nanophotosensitizers (NanoPc90, NanoPc40, NanoPc20, and NanoPc10) of different particle sizes were readily prepared based on an amphiphilic silicon(IV) phthalocyanine (SiPc)-biotin conjugate by regulating the amount of the Cremophor EL surfactant used. The photoactivities, including fluorescence and reactive oxygen species (ROS), of the self-assemblies could be regulated by the particle size. The self-assemblies could be specifically disassembled by tumor-overexpressing biotin receptors, leading to the recovery of quenched photoactivities. Demonstrated by the competitive assay, the self-assemblies were able to enter HepG2 cells through a biotin-receptor-mediated pathway, followed by biotin-receptor-triggered fluorescence recovery at the cellular level. Moreover, the particle size could also affect the in vitro and in vivo PDT effects and tumor targeting. The photocytotoxicity of NanoPc20 against HepG2 cells was more potent compared to that of NanoPc90 because of its strong intracellular fluorescence, higher intracellular ROS generation, and different subcellular localization. In addition, NanoPc20 showed higher in vivo tumor targeting and photodynamic therapeutic efficacy than NanoPc90. This work would provide a valuable reference for the development of self-assembled nanophotosensitizers for cancer diagnosis and therapy.

Liposomal formulations of photosensitizers

Photodynamic therapy (PDT) is a clinical ablation modality to treat cancers and other diseases. PDT involves administration of a photosensitizer, followed by irradiation of target tissue with light. As many photosensitizers are small and hydrophobic, solubilization approaches and nanoscale delivery vehicles have been extensively explored. Liposomes and lipid-based formulations have been used for the past 30 years, and in some cases have been developed into well-defined commercial PDT products. This review provides an overview of common liposomal formulation strategies for photosensitizers for PDT and also photothermal therapy. Furthermore, research efforts have examined the impact of co-loading therapeutic cargo along with photosensitizers within liposomes. Additional recent approaches including imaging, overcoming hypoxia, upconversion and activatable liposomal formulations are discussed.