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The selectivity of photodynamic therapy (PDT) derived from the tailored accumulation of photosensitizing drug (photosensitizer; PS) in the tumor microenvironment (TME), and from local irradiation, turns it into a "magic bullet" for the treatment of resistant tumors without sparing the healthy tissue and possible adverse effects. However, locally-induced hypoxia is one of the undesirable consequences of PDT, which may contribute to the emergence of resistance and significantly reduce therapeutic outcomes. Therefore, the development of strategies using new approaches in nanotechnology and molecular biology can offer an increased opportunity to eliminate the disadvantages of hypoxia. Emerging evidence indicates that wisely designed phototherapeutic procedures, including: (i) ROS-tunable photosensitizers, (ii) organelle targeting, (iii) nano-based photoactive drugs and/or PS delivery nanosystems, as well as (iv) combining them with other strategies (i.e. PTT, chemotherapy, theranostics or the design of dual anticancer drug and photosensitizers) can significantly improve the PDT efficacy and overcome the resistance. This mini-review addresses the role of hypoxia and hypoxia-related molecular mechanisms of the HIF-1α pathway in the regulation of PDT efficacy. It also discusses the most recent achievements as well as future perspectives and potential challenges of PDT application against hypoxic tumors.

Diabetes, and several diseases related to diabetes, including cancer, cardiovascular diseases and neurological disorders, represent one of the major ongoing threats to human life, becoming a true pandemic of the 21st century. Current treatment strategies for diabetes mainly involve promoting β-cell differentiation, and one of the most widely studied targets for β-cell regeneration is DYRK1A kinase, a member of the DYRK family. DYRK1A has been characterized as a key regulator of cell growth, differentiation, and signal transduction in various organisms, while further roles and substrates are the subjects of extensive investigation. The targets of interest in this review are implicated in the regulation of β-cells through DYRK1A inhibition—through driving their transition from highly inefficient and death-prone populations into efficient and sufficient precursors of islet regeneration. Increasing evidence for the role of DYRK1A in diabetes progression and β-cell proliferation expands the potential for pharmaceutical applications of DYRK1A inhibitors. The variety of new compounds and binding modes, determined by crystal structure and in vitro studies, may lead to new strategies for diabetes treatment. This review provides recent insights into the initial self-activation of DYRK1A by tyrosine autophosphorylation. Moreover, the importance of developing novel DYRK1A inhibitors and their implications for the treatment of diabetes are thoroughly discussed. The evolving understanding of DYRK kinase structure and function and emerging high-throughput screening technologies have been described. As a final point of this work, we intend to promote the term “diabetic kinome” as part of scientific terminology to emphasize the role of the synergistic action of multiple kinases in governing the molecular processes that underlie this particular group of diseases.

New hybrid TiO2-based materials were obtained by impregnation of semiconductor with 5,10,15,20-tetrakis(2,6-difluorosulfonylophenyl)porphyrin (F2POH) and its zinc(II) complex (ZnF2POH). The efficient immobilization of the porphyrins on the surface of titanium dioxide was obtained due to the presence of -SO3H functional groups, which interact with the surface of TiO2. All prepared materials were thoroughly characterized in terms of their morphological, spectroscopic, electrochemical, photochemical and functional properties by diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry, photoelectrochemistry as well as biological and photocatalytic tests. The modification of TiO2 with halogenated (metallo)porphyrins allows to improve overall properties of the studied materials and assess their activity upon visible part of the electromagnetic radiation (>400 nm). Nevertheless, due to their limited stability, observed photochemical effects are quite short lived. It is shown that the fluorine atoms present in porphyrin structure modulate not only physicochemical properties of the hybrid materials but also their photoactivity in the generation of reactive oxygen species (ROS). The materials based on fluorinated porphyrins have shown photocatalytic activity in the degradation of model pollutants: 4-chlorophenol and opioid drug – tramadol. Moreover, they exhibit quite significant antibacterial activity against Gram-positive (S. aureus), notably higher than TiO2 modified with commercial tetraphenyl porphyrin (TPPS). The role of singlet oxygen, hydroxyl and iodide radicals in the performed photoinactivation processes is elucidated for all studied systems. Finally, TiO2 alone is not active against bacteria upon visible light irradiation, what implies that materials containing fluorinated and sulfonated porphyrins have improved photochemical activity and efficiency of the ROS generation. Thus, they are interesting materials especially for photodynamic inactivation of microorganisms.

Resistance of microorganisms to antibiotics has led to research on various therapeutic strategies with different mechanisms of action, including photodynamic inactivation (PDI). In this work, we evaluated a cationic, neutral, and anionic meso-tetraphenylporphyrin derivative&rsquo, s ability to inactivate the Gram-negative and Gram-positive bacteria in a planktonic suspension under blue light irradiation. The spectroscopic, physicochemical, redox properties, as well as reactive oxygen species (ROS) generation capacity by a set of photosensitizers varying in lipophilicity were investigated. The theoretical calculations were performed to explain the distribution of the molecular charges in the evaluated compounds. Moreover, logP partition coefficients, cellular uptake, and phototoxicity of the photosensitizers towards bacteria were determined. The role of a specific microbial efflux pump inhibitor, verapamil hydrochloride, in PDI was also studied. The results showed that E. coli exhibited higher resistance to PDI than S. aureus (3&ndash, 5 logs) with low light doses (1&ndash, 10 J/cm2). In turn, the prolongation of irradiation (up to 100 J/cm2) remarkably improved the inactivation of pathogens (up to 7 logs) and revealed the importance of photosensitizer photostability. The PDI potentiation occurs after the addition of KI (more than 3 logs extra killing). Verapamil increased the uptake of photosensitizers (especially in E. coli) due to efflux pump inhibition. This effect suggests that PDI is mediated by ROS, the electrostatic charge interaction, and the efflux of photosensitizers (PSs) regulated by multidrug-resistance (MDR) systems. Thus, MDR inhibition combined with PDI gives opportunities to treat more resistant bacteria.

A class of amphiphilic photosensitizers for photodynamic therapy (PDT) was developed. Sulfonate esters of modified porphyrins bearing&mdash, F substituents in the ortho positions of the phenyl rings have adequate properties for PDT, including absorption in the red, increased cellular uptake, favorable intracellular localization, low cytotoxicity, and high phototoxicity against A549 (human lung adenocarcinoma) and CT26 (murine colon carcinoma) cells. Moreover, the role of type I and type II photochemical processes was assessed by fluorescent probes specific for various reactive oxygen species (ROS). The photodynamic effect is improved not only by enhanced cellular uptake but also by the high generation of both singlet oxygen and oxygen-centered radicals. All of the presented results support the idea that the rational design of photosensitizers for PDT can be further improved by better understanding the determinants affecting its therapeutic efficiency and explain how smart structural modifications can make them suitable photosensitizers for application in PDT.

Bacterichlorins possess a characteristic intense electronic absorption in the near-infrared part of the electromagnetic radiation (NIR) from 700 nm up to 900 nm, where endogenous chromophores do not absorb and which allows deep penetration through tissues. Although naturally-occurring metal complexes derived from bacteriochlorophylls are unstable and their use is limited, it is currently possible to obtain large-scale libraries of photostable synthetic compounds belonging to the bacteriochlorin family. This review presents an up-to-date overview of the most significant studies on the synthesis, spectroscopic, photochemical, and electrochemical characteristics as well as various potential applications of bacteriochlorins and their metal complexes. Particular emphasis has been given to the possibilities of their use in medicine, especially in photodynamic therapy of cancer (PDT), photodiagnosis (PD), and photodynamic inactivation (PDI) of bacteria, viruses, and fungi. The combination of (metallo)bacteriochlorins with polymeric micelles, lipoproteins, nanoparticles, and metal-organic frameworks in order to increase their efficacy is also discussed. Other potential applications of (metallo)bacteriochlorins discussed in this paper include their use as light-harvesting antennas, optical sensors, photocatalysts, and dye-sensitized solar cells for efficient solar energy conversion.

Biodegradable nonionic sugar esters-based surfactants have been gaining more and more attention in recent years due to their chemical plasticity that enables the various applications of these molecules. In this review, various synthesis methods and biotechnological implications of lactose esters (LEs) uses are considered. Several chemical and enzymatic approaches are described for the synthesis of LEs, together with their applications, i.e. function in detergents formulation and as additives that not only stabilize food products but also protect food from undesired microbial contamination. Further, this article discusses medical applications of LEs in cancer treatment, especially their uses as biosensors, halogenated anticancer drugs, and photosensitizing agents for photodynamic therapy of cancer and photodynamic inactivation of microorganisms.

Photodynamic therapy (PDT) augments the host antitumor immune response, but the role of the PDT effect on the tumor microenvironment in dependence on the type of photosensitizer and/or therapeutic protocols has not been clearly elucidated. We employed three bacteriochlorins (F2BOH, F2BMet and Cl2BHep) of different polarity that absorb near-infrared light (NIR) and generated a large amount of reactive oxygen species (ROS) to compare the PDT efficacy after various drug-to-light intervals: 15 min. (V-PDT), 3h (E-PDT) and 72h (C-PDT). We also performed the analysis of the molecular mechanisms of PDT crucial for the generation of the long-lasting antitumor immune response. PDT-induced damage affected the integrity of the host tissue and developed acute (protocol-dependent) local inflammation, which in turn led to the infiltration of neutrophils and macrophages. In order to further confirm this hypothesis, a number of proteins in the plasma of PDT-treated mice were identified. Among a wide range of cytokines (IL-6, IL-10, IL-13, IL-15, TNF-&alpha, GM-CSF), chemokines (KC, MCP-1, MIP1&alpha, MIP1&beta, MIP2) and growth factors (VEGF) released after PDT, an important role was assigned to IL-6. PDT protocols optimized for studied bacteriochlorins led to a significant increase in the survival rate of BALB/c mice bearing CT26 tumors, but each photosensitizer (PS) was more or less potent, depending on the applied DLI (15 min, 3 h or 72 h). Hydrophilic (F2BOH) and amphiphilic (F2BMet) PSs were equally effective in V-PDT (&gt, 80 cure rate). F2BMet was the most efficient in E-PDT (DLI = 3h), leading to a cure of 65 % of the animals. Finally, the most powerful PS in the C-PDT (DLI = 72 h) regimen turned out to be the most hydrophobic compound (Cl2BHep), allowing 100 % of treated animals to be cured at a light dose of only 45 J/cm2.

Three photodynamic therapy (PDT) protocols with 15 min, 3 h and 72 h drug-to-light time intervals (DLIs) were performed using a bacteriochlorin named redaporfin, as a photosensitizer. Blood flow and pO2 changes after applying these protocols were investigated in a Lewis lung carcinoma (LLC) mouse model and correlated with long-term tumor responses. In addition, cellular uptake, cytotoxicity and photocytotoxicity of redaporfin in LLC cells were evaluated. Our in vitro tests revealed negligible cytotoxicity, significant cellular uptake, generation of singlet oxygen, superoxide ion and hydroxyl radicals in the cells and changes in the mechanism of cell death as a function of the light dose. Results of in vivo studies showed that treatment focused on vascular destruction (V-PDT) leads to a highly effective long-term antineoplastic response mediated by a strong deprivation of blood supply. Tumors in 67% of the LLC bearing mice treated with V-PDT regressed completely and did not reappear for over 1 year. This significant efficacy can be attributed to photosensitizer (PS) properties as well as distribution and accurate control of oxygen level and density of vessels before and after PDT. V-PDT has a greater potential for success than treatment based on longer DLIs as usually applied in clinical practice.

The increasingly limited therapeutic options for the treatment of infections caused by multi-resistant Gram-negative bacteria due to the alarming increase in bacteria resistance, renewed interest in photodynamic inactivation (PDI) of bacteria. We address PDI of multi-resistant bacteria with a new family of cationic tetra-imidazolyl phthalocyanines bearing a diversity of cationizing alkylic chain sizes, degrees of cationization and coordinating metals. The antimicrobial activities of the phthalocyanines under white light against Gram-positive and Gram-negative bacteria have remarkable differences in efficacy. We relate their spectroscopic and photophysical properties with the generation of reactive oxygen species (ROS), biological performance and structural features. We show that sub-micromolar concentrations of a Zn(II) tetra-ethyl cationic phthalocyanine reduce colonies of Gram-negative bacteria (E. coli, P. aeruginosa) and C. albicans by 7 log units while leaving mammalian cells unharmed. This is a new lead to address hard-to-treat localized infections.

The photogeneration of reactive oxygen species (ROS) by molecular and nanostructured systems with d- and f-metal compounds is discussed with the emphasis on the mechanisms involved in the process. The effectiveness of ROS photogeneration in various systems from simple metal complexes with non-macrocyclic and macrocyclic ligands, through more complex supramolecular scaffolds, up to nano-platforms and hybrid materials is reviewed considering their biological and medical applications. A particular emphasis is focused on the comparison of mechanisms of ROS photogeneration exploited in d- versus f-metal systems. Perspectives for each type of systems are also outlined.

Highly-active, surface-modified anatase TiO2 nanoparticles were successfully synthesized and characterized. The morphological and optical properties of the obtained (metallo)porphyrin@qTiO2 materials were evaluated using absorption and fluorescence spectroscopy, scanning electron microscopy (SEM) imaging, and dynamic light scattering (DLS). These hybrid nanoparticles efficiently generated reactive oxygen species (ROS) under blue-light irradiation (420 &plusmn, 20 nm) and possessed a unimodal size distribution of 20&ndash, 70 nm in diameter. The antimicrobial performance of the synthetized agents was examined against Gram-negative and Gram-positive bacteria. After a short-term incubation of microorganisms with nanomaterials (at 1 g/L) and irradiation with blue-light at a dose of 10 J/cm2, 2&ndash, 3 logs of Escherichia coli, and 3&ndash, 4 logs of Staphylococcus aureus were inactivated. A further decrease in bacteria viability was observed after potentiation photodynamic inactivation (PDI), either by H2O2 or KI, resulting in complete microorganism eradication even when using low material concentration (from 0.1 g/L). SEM analysis of bacteria morphology after each mode of PDI suggested different mechanisms of cellular disruption depending on the type of generated oxygen and/or iodide species. These data suggest that TiO2-based materials modified with sulfonated porphyrins are efficient photocatalysts that could be successfully used in biomedical strategies, most notably, photodynamic inactivation of microorganisms.

The easy access and low price of pyrrole and aldehydes, conjugated with the simplicity in preparing meso-substituted porphyrins, makes this type of porphyrins very attractive for a broad range of applications. However, there is an increasing demand for the development of new synthetic processes involving more sustainable chemical principles substituting, whenever possible, dangerous organic solvents by alternative solvents, chromatographic purifications by precipitations and energy-intensive procedures by alternative energy sources such as microwaves and ultrasounds. In this review we will address some recent strategies to synthesize meso-substituted porphyrins using alternative energy sources, reaction media and catalysts, namely microwave irradiation, water as solvent, or solid microporous acid catalysts.

The impact of substituents on the photochemical and biological properties of tetraphenylporphyrin-based photosensitizers for photodynamic therapy of cancer (PDT) as well as photodynamic inactivation of microorganisms (PDI) was examined. Spectroscopic and physicochemical properties were related with therapeutic efficacy in PDT of cancer and PDI of microbial cells in vitro. Less polar halogenated, sulfonamide porphyrins were most readily taken up by cells compared to hydrophilic and anionic porphyrins. The uptake and PDT of a hydrophilic porphyrin was significantly enhanced with incorporation in polymeric micelles (Pluronic L121). Photodynamic inactivation studies were performed against Gram-positive (S. aureus, E. faecalis), Gram-negative bacteria (E. coli, P. aeruginosa, S. marcescens) and fungal yeast (C. albicans). We observed a 6 logs reduction of S. aureus after irradiation (10 J/cm2) in the presence of 20 μM of hydrophilic porphyrin, but this was not improved with incorporation in Pluronic L121. A 2-3 logs reduction was obtained for E. coli using similar doses, and a decrease of 3-4 logs was achieved for C. albicans. Rational substitution of tetraphenylporphyrins improves their photodynamic properties and informs on strategies to obtain photosensitizers for efficient PDT and PDI. However, the design of the photosensitizers must be accompanied by the development of tailored drug formulations.

Infected leg ulcers are painful, debilitating and reduce a patient’s quality of life, therefore they are becoming a significant clinical and socioeconomic problem. Increasing resistance to antibiotics, is one of the most urgent challenge to medicine worldwide and requires searching for new, innovative and more efficient medical strategies. One of the opportunities for the cure of leg ulcers is photodynamic inactivation (PDI), which has been widely used in the treatment of various bacterial, fungal and viral infections. PDI encompasses three independently non-toxic elements: a photosensitizer (PS), light of an appropriate wavelength, and molecular oxygen that lead to generation of reactive oxygen species (ROS) responsible for inactivation of microorganisms, including those present in the form of biofilm in chronic wounds. PDI, due to its multiple mechanism of action, low invasiveness and lack of significant side effects, offers an interesting potential alternative for combating the microbial resistance in the infected leg ulcers. It also significantly decreases the area of leg ulcers, or may even heal them completely and thus remarkably improves a patient’s health.

Objective To compare hydrophilic and lipophilic bacteriochlorin photosensitizers in the photodynamic therapy of cancer, and relate their properties and in vitro phototoxicities to the efficacy of in vivo PDT treatments. Materials and methods Photochemical characterization of a hydrophilic bacteriochlorin (F2 BOH) photosensitizer, and its use in PDT was compared with the performance of a closely related but water-insoluble bacteriochlorin (F2 BMet or redaporfin). Biodistribution, pharmacokinetics, skin photosensitivity, PDT efficacy and immune responses of two bacteriochlorins were compared. PDT in vitro employed CT26 colon carcinoma cells. BALB/c mice bearing CT26 cells were treated according to a protocol where the illumination of the subcutaneous tumor is performed 15 minute after intravenous administration of the photosensitizer, while it is in the vascular compartment (vascular-PDT). Results F2 BOH has photochemical properties comparable to redaporfin and both are promising photosensitizers for PDT. Although, F2 BOH is 10 times less phototoxic in vitro than redaporfin, the phototoxicity of F2 BOH in vascular-PDT is comparable to that of redaporfin. This is consistent with the fact that the vasculature is the main target of vascular-PDT. F2 BOH-PDT led to long-term cures and stimulation of the immune system. Conclusion F2 BOH is soluble in aqueous media, photostable, has a convenient elimination half-life of 44 hours and leads to very low skin photosensitivity one week after administration. F2 BOH and redaporfin are both very phototoxic in vascular-PDT, but this could not be anticipated from their widely different phototherapeutic indices in vitro. PDT with F2 BOH enabled long-term cures of BALB/c mice with subcutaneously implanted CT26 tumors, and the cured mice rejected tumor re-inoculation one year after the treatment. Lasers Surg. Med. 50:451-459, 2018. © 2018 Wiley Periodicals, Inc.

We assessed the tolerability and safety in rodents of a single intravenous (i.v.) dose of redaporfin, a novel photosensitizer for Photodynamic Therapy (PDT) of cancer. Two approaches were used to evaluate acute toxicity: (i) a dose escalation study in BALB/c mice to evaluate the maximum tolerated dose of redaporfin, and (ii) a safety toxicology study in Wistar rats, of a single dose of redaporfin, with or without illumination, to evaluate possible signs of systemic toxicity. Redaporfin formulation was well tolerated by mice, with no signs of adverse reactions up to 75 mg/kg. In rats, there were no relevant changes, except for a significant, but transient, increase in the blood serum markers for hepatic function and muscle integrity, and also on neutrophil counts, observed after the application of light. The overall results showed that redaporfin-PDT is very well tolerated. No abnormalities were observed, including reactions at the injection site or skin phototoxicity, although the animals were maintained in normal indoor lighting. Redaporfin also showed a high efficacy in the treatment of male BALB/c mice with subcutaneously implanted colon (CT26) tumours. Vascular-PDT with 1.5 mg/kg redaporfin and a light dose of 74 J/cm2 led to the complete tumour regression in 83% of the mice.

Ideal reaction conditions were found to promote the "cold" monomethylation of 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin with CH3I, at minute time scale, in the presence of base. The photophysical characterization, cellular uptake and dark cytotoxicity of the resulting monomethylated porphyrin were appraised. Moreover, the syntheses of the corresponding labeled porphyrin, using short-lived carbon-11, prepared in the automated radiolabeling system were efficiently performed. The purification of the labeled product was achieved via preparative HPLC with high radiochemical purity and specific radioactivity. Preliminary studies on the biodistribution of 5,10,15-tris(3-hydroxyphenyl)-20-(3-[11C]methoxyphenyl)porphyrin carried out in a BALB/C normal mouse, using PET imaging, showed that the liver is the main pathway for excretion. Read More: http://www.worldscientific.com/doi/abs/10.1142/S1088424615500728

An efficient one-step synthetic strategy was used to prepare a set of dicarboxamides through palladium-catalysed amino carbonylation of iodoalkenyl and iodoaryl compounds, with use of various alkyl- and aryldiamines as N-nucleophiles. The isolated yields of the dicarboxamides depended signifi cantly on the iodo substrate and diamine structures, as well as on the reaction conditions, the best one (ca. 70 %) being achieved with 1-iodocyclohexene as substrate and 1,4-di aminobutane as nucleophile, at 100 °C and 30 bar of CO. When iodobenzene was used as model aryl halide, the high est yield of the target dibenzamides (ca. 65 %) was obtained with 1,4-diaminobenzene as coupling amine, at 100 °C and 10 bar of CO. Preliminary studies on their in vitro cytotoxicity against human lung carcinoma A549 cells showed N,N�- (butane-1,4-diyl)dibenzamide and androst-16-ene-based di carboxamides to be the most efficient cytotoxic agents, with IC50values of approximately 40μM.

Photophysical and photochemical studies on 5,10,15,20-tetrakis(2,6-difluoro-5-N-methylsulfamylophenyl)porphyrin (F2PMet) and its cobalt(III) and zinc(II) complexes, including spectroscopic characteristics, photostability and photocatalytic activity, were carried out. The hybrid materials resulting from adsorption of these tetrapyrroles at the surface of titanium dioxide were prepared and examined in terms of their morphological, optical and functional properties applying absorption spectroscopy, scanning electron microscopy (SEM), photoelectrochemistry and photocatalytic tests. Our studies revealed that MF2PMet@TiO2 photocatalysts can be considered as the hybrid organic/inorganic photoactive materials enabling photodegradation of a synthetic opioid such as tramadol hydrochloride (TRML) and a model pollutant, 4-chlorophenol, in aqueous solution under visible light irradiation (λ > 400 nm). To elucidate mechanisms of photochemical processes, the photocatalytic activity of investigated metalloporphyrins was compared in homo- and heterogeneous systems. The results indicate that impregnation of TiO2 (P25) with functionalized porphyrins can improve its photoactivity. ZnF2PMet@TiO2 exhibited a superior photocatalytic performance towards TRML degradation. The role of singlet oxygen and hydroxyl radicals in photodegradation processes has been elucidated both for MF2PMet and MF2PMet@TiO2 systems.

The impact of substituents on the photochemical and biological properties of tetraphenylporphyrin-based photosensitizers for photodynamic therapy of cancer (PDT) as well as photodynamic inactivation of microorganisms (PDI) was examined. Spectroscopic and physicochemical properties were related with therapeutic efficacy in PDT of cancer and PDI of microbial cells in vitro. Less polar halogenated, sulfonamide porphyrins were most readily taken up by cells compared to hydrophilic and anionic porphyrins. The uptake and PDT of a hydrophilic porphyrin was significantly enhanced with incorporation in polymeric micelles (Pluronic L121). Photodynamic inactivation studies were performed against Gram-positive (S. aureus, E. faecalis), Gram-negative bacteria (E. coli, P. aeruginosa, S. marcescens) and fungal yeast (C. albicans). We observed a 6 logs reduction of S. aureus after irradiation (10 J/cm2) in the presence of 20 μM of hydrophilic porphyrin, but this was not improved with incorporation in Pluronic L121. A 2-3 logs reduction was obtained for E. coli using similar doses, and a decrease of 3-4 logs was achieved for C. albicans. Rational substitution of tetraphenylporphyrins improves their photodynamic properties and informs on strategies to obtain photosensitizers for efficient PDT and PDI. However, the design of the photosensitizers must be accompanied by the development of tailored drug formulations.

The emergence of Multi-Drug-Resistant (MDR) organisms has become a major worldwide clinical problem. The extensive and routine use of the first-line antibiotics to control infections imposed the development of multiple mechanisms of microbial resistance. Despite the fact that numerous advanced technologies enable the molecular design of new antibiotics, the MDR-associated infections remain a great challenge to modern medicine. Consequently, there is an urgent need to find other methods for reducing the antimicrobial resistance problem. Innovative bioinorganic antimicrobial platforms offer an interesting alternative for combating the microbial resistance. Herein, we describe the bioinorganic strategies with multiple mechanisms of action based on i) small metal complexes, ii) metal modified macromolecules, iii) metal and metal oxides nanoparticles, iv) light-activated bioinorganic platforms, to overcome the pathogen's resistance.

Reactive oxygen species (ROS) play key roles in cell signaling systems and homeostasis, and they are also fundamental to photodynamic therapy (PDT). PDT efficacy can be affected by the nature and persistence of ROS. A comprehensive understanding of ROS generation pathways greatly facilitates the analysis of photodynamic mechanisms and enables potentiation of PDT efficacy. Diverse methods exist to distinguish between Type I and Type II mechanisms of ROS generation. The direct monitoring of 1O2 formation involves the detection of its phosphorescence at 1270 nm. Electron spin resonance is also used in conjunction with appropriate spin traps for detection of oxygen-centered radical species. Moreover, a variety of more or less specific fluorescent probes are frequently used to detect both singlet oxygen and free radicals. This chapter summarizes our recent efforts in the design and characterization of new ROS-generating systems for PDT. Special attention is given to bacteriochlorins because they absorb in the NIR, generate ROS via both Type I and Type II mechanisms, and are very efficient in the PDT treatment of several types of tumors including pigmented melanoma. The current status and possible opportunities of ROS generation and potentiation in PDT are highlighted. Particular emphasis is placed on the elucidation of the ROS-mediated photochemical and molecular mechanisms that give rise to the establishment of PDT as a first-line systemic treatment of highly resistant diseases, especially invasive and metastatic tumors.

Progress in the photodynamic therapy (PDT) of cancer should benefit from a rationale to predict the most efficient of a series of photosensitizers that strongly absorb light in the phototherapeutic window (650-800 nm) and efficiently generate reactive oxygen species (ROS = singlet oxygen and oxygen-centered radicals). We show that the ratios between the triplet photosensitizer-O2 interaction rate constant (kD) and the photosensitizer decomposition rate constant (kd), kD/kd, determine the relative photodynamic activities of photosensitizers against various cancer cells. The same efficacy trend is observed in vivo with DBA/2 mice bearing S91 melanoma tumors. The PDT efficacy intimately depends on the dynamics of photosensitizer-oxygen interactions: charge transfer to molecular oxygen with generation of both singlet oxygen and superoxide ion (high kD) must be tempered by photostability (low kd). These properties depend on the oxidation potential of the photosensitizer and are suitably combined in a new fluorinated sulfonamide bacteriochlorin, motivated by the rationale.

The therapeutic outcome of photodynamic therapy (PDT) with redaporfin (a fluorinated sulfonamide bacteriochlorin, F2BMet or LUZ11) was improved using Pluronic-based (P123, F127) formulations. Neither redaporfin encapsulated in Pluronic nor micelles alone exhibited cytotoxicity in a broad concentration range. Comprehensive in vitro studies against B16F10 melanoma cells showed that redaporfin-P123 micelles enhanced cellular uptake and increased oxidative stress compared with redaporfin-F127 or photosensitizer alone after short incubation times. ROS-sensitive fluorescent probes showed that the increased oxidative stress is due, at least in part, to a more efficient formation of hydroxyl radicals, and causes strong light-dose dependent apoptosis and necrosis. Tissue distribution and pharmacokinetic studies in tumor-bearing mice show that the Pluronic P123 formulation of redaporfin increases its bioavailability as well as the tumor-to-muscle and tumor-to-skin ratios, in comparison with Cremophor EL and Pluronic F127 formulations. Redaporfin in P123 was most successful in the PDT of C57BL/6J mice bearing subcutaneously implanted B16F10 melanoma tumors. Vascular-targeted PDT combining 1.5 mg kg(-1) redaporfin in P123 with a light dose of 74 J cm(-2) led to 100% complete cures (i.e., no tumor regrowth over one year post-treatment). This remarkable result reveals that modification of redaporfin with Pluronic block copolymers overcomes the resistance of melanoma cells to PDT possibly via increased tumor selectivity and enhanced ROS generation.

Applications of metalloporphyrins and related molecules have been extensively pursued in the context of photodynamic therapy of cancer (PDT) and other biomedical applications. This review discusses photophysical and photochemical properties of metalloporphyrins and their analogues, such as metallochlorins, metallobacteriochlorins and metallophthalocyanines that are relevant for photodynamic processes. We specially emphasize the search for sensitizers strongly absorbing in phototherapeutic window (650–850 nm), the most penetrating and least harmful radiation to human tissues. Molecular engineering is guided by the understanding of the influence of the central metal ion and substituents on the electronic structure and photophysical properties of these compounds. The effects of the structural modifications are elucidated via studies of the electronic absorption and emission spectra, fluorescence and triplet state lifetimes and quantum yields, as well as quantum yields of singlet oxygen generation. The interaction between electronically excited (metallo)porphyrin derivatives and molecular oxygen is specially highlighted, because it leads to the generation of reactive oxygen species (ROS), the major players in photomedicine and photocatalysis. The parameters analysed and correlated encompass photophysical and electrochemical properties, cellular uptake and localization of the photosensitizer, as well as the mechanism of photodynamically induced cell death. The factors that determine the efficacy of PDT (drug and light doses, drug to light interval, oxygen concentration and tumour margin) are also emphasized. This review explores the most recent research performed on metalloporphyrin-based materials in photodynamic therapy, photodynamic inactivation of microorganisms, photodiagnosis and drug delivery, demonstrating their perspectives for biomedical applications.

This article focuses on the versatile ways in which hydrogen peroxide can be activated by metal ions and metal compounds, in terms of possible biomedical and environmental applications and future incentives in these areas. Mechanistic studies performed in our group are discussed in reference to related studies reported in the literature. It covers various thermal activation pathways, including Fenton and Fenton-like reactions, the application of iron, manganese and other metals complexes, as well as metalloenzymes. Furthermore, light-induced generation, activation and utilization of hydrogen peroxide are presented for the photo-Fenton reactions, the application of macrocyclic photosensitizers and the use of semiconductors such as TiO2 as heterogeneous photosensitizers. Mechanistic aspects of several thermal and photochemical pathways in metal-assisted hydrogen peroxide applications for biomedical or environmental purposes are discussed, and some obstacles to be overcome are highlighted.

A set of amphiphilic fluorinated porphyrins appended with sulfonate ester groups were synthesized and fully characterized. The reaction proceeds efficiently, with high yields, with an improved methodology. Their potential use as imaging and phototherapeutic agents was assessed measuring relevant photophysical properties. It is shown that these porphyrins have good photostability, long triplet lifetimes (between 47 μs and 102 μs), high singlet oxygen quantum yields (0.74≤FD≤1.00), low fluorescence quantum yields (

Chlorins have intense red absorptions and high tumor affinities that make them interesting candidates for photodynamic therapy (PDT) of cancer. This paper reports cytotoxicity, phototoxicity, in vitro cellular uptake, and in vivo biodistribution and PDT efficacy of a synthetic chlorin derivative (TCPCSO₃H) towards Cloudman melanoma cells (S91). No cytotoxic effects were observed in vitro at concentrations up to 20 μm, and no toxicity was observed in vivo in DBA mice with doses up to 2 mg kg⁻¹. Pharmacokinetics and biodistribution of TCPCSO₃H were evaluated in vivo in DBA mice bearing S91 tumors. TCPCSO₃H demonstrated preferential accumulation in S91 mouse melanoma, with tumor-to-normal tissue ratios of 5 and 11 for muscle and skin, respectively, 24 h after intravenous injection of 2 mg kg⁻¹. Photodynamic therapy performed under these conditions with 70 mW cm⁻² diode laser irradiation at 655 nm for 25 min (total light dose=105 J cm⁻²) resulted in scab formation, followed by temporary or permanent (>60 days) tumor remission. According to the Kaplan-Meier analysis, the median survival time of the control group was 9 days, whereas that of the treated group was 38 days.

Near infrared (NIR) photons are ideally suited for photomedicine because they are relatively harmless and penetrate deeply in biological tissues. However, their use is impaired by lack of straightforward methods to synthesize large quantities of stable infrared-absorbing molecules with long-lived excited states. Here we present a one-step synthesis of amphiphilic meso -phenyl halogenated bacteriochlorins, via hydrazide reduction, possessing strong absorption about 750 nm. The reaction proceeds efficiently, in large quantities, with a solid–solid solvent-free methodology, that is characterized by its simplicity, efficiency and minimum environmental impact. The new bacteriochlorins have unprecedented chemical and photophysical properties, namely strong electronic absorption above 720 nm, adequate photostability, low fluorescence quantum yield and n -octanol/water partition coefficients (log P OW ) ranging from −1.7 to >4, meaning that the library of compounds synthesized in this work is versatile enough to be applied in photodynamic therapy for a range of biological targets.

Chlorin and bacteriochlorin derivatives of 5,10,15,20-tetrakis(2-chloro-5-sulfophenyl)porphyrin have intense absorptions in the phototherapeutic window, high water solubility, high photostability, low fluorescence quantum yield, long triplet lifetimes, and high singlet oxygen quantum yields. Biological studies revealed their negligible dark cytotoxicity, yet significant photodynamic effect against A549 (human lung adenocarcinoma), MCF7 (human breast carcinoma) and SK-MEL-188 (human melanoma) cell lines upon red light irradiation (cutoff λ

A water-soluble halogenated porphyrin, namely 5,10,15,20-tetrakis(2-chloro-3-sulfophenyl)porphyrin (TCPPSO(3)H), was prepared and evaluated as sensitizer for photodynamic therapy (PDT). Photophysical properties of TCPPSO(3)H, such as high photostability, long triplet lifetime and high singlet oxygen quantum yield suggest high effectiveness of this class of halogenated porphyrins in PDT. TCPPSO(3)H is non-toxic in the dark and causes a significant photodynamic effect examined against MCF7 (human breast carcinoma), SKMEL 188 (human melanoma) and S91(mouse melanoma) cell lines upon red light irradiation (cutoff < 600 nm) at low light doses. Time-dependent cellular uptake of TCPPSO(3)H reached plateau at 120 min and was the highest for S91, 20% lower for MCF7 and 70% lower for SKMEL 188. Our results show that this halogenated water-soluble porphyrin is an efficient photosensitizer and reveal the potential of this class of compounds as PDT agents.

Photodynamic therapy (PDT) requires a medical device, a photosensitizing drug and adequate use of both to trigger biological mechanisms that can rapidly destroy the primary tumour and provide long-lasting protection against metastasis. We present a multidisciplinary view of the issues raised by the development of PDT. We show how spectroscopy, photophysics, photochemistry and pharmacokinetics of photosensitizers determine the mechanism of cell death and clinical protocols. Various examples of combinations with chemotherapies and immunotherapies illustrate the opportunities to potentiate the outcome of PDT. Particular emphasis is given to the mechanisms that can be exploited to establish PDT as a systemic treatment of solid tumours and metastatic disease.

Photodynamic therapy (PDT) with current photosensitisers focuses on local effects and these are limited by light penetration in tissues. We employ a stable near-infrared (NIR) absorbing bacteriochlorin with ca. 8 h plasma half-life to increase the depth of the treatment and elicit strong systemic (immune) responses. Primary tumour growth delays and cures of BALB/c and nude mice bearing CT26 mouse colon carcinoma are related to the parameters that control PDT efficacy. The systemic anti-tumour protection elicited by the optimised PDT regimen is assessed by tumour rechallenges and by resistance to the establishment of metastasis after intravenous injection of CT26 cells. The optimised treatment regime offered 86% cure rate in BALB/c mice but no cures in BALB/c nude mice. Cured mice rechallenged over 3 months later with CT26 cells rejected the tumour cells in 67% of the cases. PDT of a subcutaneous CT26 tumour 5 days after the additional intravenous injection of CT26 cells very significantly reduced lung metastasis. The PDT regimen optimised for the bacteriochlorin leads to remarkable long-term survival rates, effective immune memory and control of lung metastasis.

Intravenous (i.v.) formulations with various amounts of organic solvents [PEG400 , propylene glycol (PG), cremophor EL (CrEL)] were used to deliver a fluorinated sulfonamide bacteriochlorin to mice, rats, and minipigs. Biodistribution studies in mice showed that a low-content CrEL formulation combines high bioavailability with high tumor-to-muscle and tumor-to-skin ratios. This formulation was also the most successful in the photodynamic therapy of mice with subcutaneously implanted CT26 murine colon adenocarcinoma tumors. Pharmacokinetic studies in mice and minipigs revealed that with the same low CrEL formulation, the half-life of the photosensitizer in the central compartment was longer in minipigs. Differences in biodistribution with the various formulations, and in pharmacokinetics between the two animal species with the same formulation, are attributed to the interaction of the formulations with low-density lipoproteins (LDLs). Skin photosensitivity studies in rats showed that 30 min exposure of the skin to a solar simulator 7 days after i.v. administration of the fluorinated sulfonamide bacteriochlorin at 1 mg kg(-1) did not elicit significant skin reactions.

High fl uorescence quantum yields, high singlet oxygen quantum yields and intense absorptions in the phototherapeutic window are fundamental properties for compounds intended for fl uorescence diagno- sis and photodynamic therapy. We report on photostable chlorins that combine these properties. The fl uorinated tetraphenylchlorin FCMet has Φ F = 0.396 and Φ Δ = 0.58 ± 0.07, whereas F 2 CMet has Φ F = 0.360 and Φ Δ = 0.54 ± 0.05, and both have molar absorption coe ffi cients larger than 30000 M − 1 cm − 1 above 650 nm. These dual functional agents use nearly all the energy absorbed to perform the desired functions and are appropriate for theranostics applications.

The bacteriochlorin-mediated PDT effects on melanoma tumors were investigated in correlation with its biodistribution. The pharmacokinetics of the photostable 5,10,15,20-tetrakis(2,6-dichloro-3- N - ethylsulfamoylphenyl)bacteriochlorin was determined in DBA mice bearing S91 melanoma tumors at different time intervals (2 h–72 h) after i.p. injection of a 10 mg kg 1 drug dose. PDT efficacy was maximal when irradiation was performed 24 h after i.p. administration, and led to the complete disappearance of tumors for nearly 2 months. Compared to the analogue sulfonated compound, the median tumor growth delay with respect to the control group increased from 27 to 44 days. This improvement is attributed to the higher stability, higher absorption in the NIR, amphiphilicity, and better selectivity of the sulfonamide bacteriochlorin.

Sulfonamides of halogenated bacteriochlorins bearing Cl or F substituents in the ortho positions of the phenyl rings have adequate properties for photodynamic therapy, including strong absorption in the near-infrared ( λ max ≈ 750 nm, ε ≈ 10 5 M − 1 cm − 1 ), controlled photodecomposition, large cellular uptake, intracellular lo- calization in the endoplasmic reticulum, low cytotoxicity, and high phototoxicity against A549 and S91 cells. The roles of type I and type II photochemical processes are assessed by singlet oxygen luminescence and intracellular hydroxyl radical detection. Phototoxicity of halogenated sulfonamide bacteriochlorins does not correlate with singlet oxygen quantum yields and must be mediated both by electron transfer (su- peroxide ion, hydroxyl radicals) and by energy transfer (singlet oxygen). The photodynamic ef fi cacy is en- hanced when cellular death is induced by both singlet oxygen and hydroxyl radicals.

The in vitro phototoxicity of a photostable, synthetic, water-soluble, halogenated bacteriochlorin, 5,10,15,20-tetrakis(2-chloro-5-sulfophenyl)bacteriochlorin (TCPBSO3H), toward mouse melanoma (S91) cells is ∼60-fold higher than that of the analogous porphyrin, and is associated with very weak toxicity in the dark; 90% of S91 cells were killed in response to a light dose of 0.26 J cm(-2) in the presence of [TCPBSO3H]=5 μM. In vivo toxicity toward DBA mice is very low, even at doses of 20 mg kg(-1). In vivo pharmacokinetics and biodistribution of TCPBSO3H were studied in DBA mice with S91 tumors; 24 h after intraperitoneal injection of 10 mg kg(-1), TCPBSO3H demonstrated preferential accumulation in S91 mouse melanoma, with tumor-to-normal tissue ratios of 3 and 5 for muscle and skin, respectively. Photodynamic therapy (PDT) performed under these conditions, with 90 mW cm(-2) diode laser irradiation at λ 750 nm for 20 min (total light dose of 108 J cm(-2)), resulted in tumor regression. Tumor recurrence was observed only approximately two months after treatment, confirming the efficacy of this PDT against melanoma.

New halogenated and sulfonated bacteriochlorins and their analogous porphyrins are employed as photosensitizers of singlet oxygen and the superoxide ion. The mechanisms of energy and electron transfer are clarified and the rates are measured. The intermediacy of a charge-transfer (CT) complex is proved for bacteriochlorins, but excluded for porphyrins. The energies of the intermediates and the rates of their interconversions are measured, and are used to obtain the efficiencies of all the processes. The mechanism of formation of the hydroxyl radical in the presence of bacteriochlorins is proposed to involve a photocatalytic step. The usefulness of these photosensitizers in the photodynamic therapy (PDT) of cancer is assessed, and the following recommendations are given for the design of more effective PDT protocols employing such photosensitizers: 1) light doses should be given over a more extended period of time when the photosensitizers form CT complexes with molecular oxygen, and 2) Fe(2+) may improve the efficiency of such photosensitizers if co-located in the same cell organelle assisting with an in vivo Fenton reaction.

We have previously reported the development of a telodendrimer, comprised of dendritic cholic acids and a linear polyethylene glycol (PEG), that can selfassemble and encapsulate hydrophobic chemotherapeutic drugs to form 25 to 50nm micellar-based nanoparticles. Using a highly efficient onebead-one-compound (OBOC) combinatorial technology, we have discovered several peptidic ligands that target cancer cell surface receptorswith high affinity and specificity. Such ligands can be easily conjugated to the telodendrimers via click chemistry, such that the ligands are displayed on the surface of the nanoparticles for efficient in vivo tumor targeting and intracellular drug delivery. Recently, we have developed a hybrid telodendrimer comprised of PEG, cholic acid and pyropheophorbibe. Like our standard telodendrimers, such hybrid telodendrimer can also self-assemble and efficiently encapsulate hydrophobic drugs to from 25 to 30nm nanoparticles. Such nanoporphyrin has proven to be extremely potent photosensitizer for in vivo phototherapy in both transgenic and xenograft tumor models. In addition to efficiently generate reactive oxygen species when illuminated with light, heat can also generated, thus allowing simultaneous photodynamic and photothermal therapy. In addition, we have discovered that low dose doxorubicin and/or heat shock protein inhibitor can be efficiently loaded into nanoporphyrin and greatly enhance the phototherapeutic effects. Clinical applications of nanoporphyrins include phototherapy of superficial tumors such as oral cancer and bladder cancer, and intraoperative phototherapy. Furthermore, nanoporphyrin can also be loaded with Gd(III) for MRI and Cu-64 for PET, making it a highly versatile theranostic agent.