BODIPY dyes tend to be highly fluorescent, but their emissions can be attenuated by adding substituents with appropriate oxidation potentials. Substituents like these have electrons to feed into photoexcited BODIPYs, quenching their fluorescence, thereby generating relatively long-lived triplet states. Singlet oxygen is formed when these triplet states interact with 3O2. In tissues, this causes cell damage in regions that are illuminated, and this is the basis of photodynamic therapy (PDT). The PDT agents that are currently approved for clinical use do not feature BODIPYs, but there are many reasons to believe that this situation will change. This review summarizes the attributes of BODIPY dyes for PDT, and in some related areas.

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BODIPY dyes in photodynamic therapy.

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Reactive oxygen species (ROS) can attack a diverse range of targets to exert antimicrobial activity, which accounts for their versatility in mediating host defense against a broad range of pathogens. Most ROS are formed by the partial reduction in molecular oxygen. Four major ROS are recognized comprising superoxide (O2•-), hydrogen peroxide (H2O2), hydroxyl radical (•OH), and singlet oxygen ((1)O2), but they display very different kinetics and levels of activity. The effects of O2•- and H2O2 are less acute than those of •OH and (1)O2, because the former are much less reactive and can be detoxified by endogenous antioxidants (both enzymatic and nonenzymatic) that are induced by oxidative stress. In contrast, no enzyme can detoxify •OH or (1)O2, making them extremely toxic and acutely lethal. The present review will highlight the various methods of ROS formation and their mechanism of action. Antioxidant defenses against ROS in microbial cells and the use of ROS by antimicrobial host defense systems are covered. Antimicrobial approaches primarily utilizing ROS comprise both bactericidal antibiotics and nonpharmacological methods such as photodynamic therapy, titanium dioxide photocatalysis, cold plasma, and medicinal honey. A brief final section covers reactive nitrogen species and related therapeutics, such as acidified nitrite and nitric oxide-releasing nanoparticles.

Antimicrobial strategies centered around reactive oxygen species - bactericidal antibiotics, photodynamic therapy and beyond

Photosynthesis is used by nature to convert light energy into chemical energy in some living systems. In such a process, a cascade of very efficient, short-range energy and electron transfer events between well-arranged, light-harvesting organic donor and acceptor pigments takes place within the photosynthetic reaction center, leading to the overall generation of chemical energy from sunlight with near quantum efficiency.1-8 During the past decade, a significant effort has been made by the scientific community toward the preparation of synthetic model compounds of natural photosynthetic systems able to convert light into other energy sources,9 probably fostered by the increasing concerns related to the utilization of fossils fuels for the production of electricity in terms of both availability and environmental issues. However, considering the structural complexity presented by the natural photosynthetic systems, much of the scientific effort has been devoted toward the preparation and study of structurally simpler systems, with the aim of reproducing some of the fundamental steps occurring in natural photosynthesis, one of the most important being the photoinduced charge separation (CS).10-12 Among the chromophores that have been used as molecular components in artificial photosynthetic systems, porphyrinoids, the ubiquitous molecular building blocks employed by nature in natural photosynthesis, have been the preferred and obvious choice, due to their intense optical absorption and rich redox chemistry.13-20 Within the large family of porphyrinoid systems, phthalocyanines (Pcs) enjoy a privileged position (Figure 1a). These chromophores, which have a two-dimensional 18-πelectron aromatic system isoelectronic with that of porphyrins (Pors), possess in fact unique physicochemical properties which render these macrocycles valuable building blocks in materials science.21-32 Pcs are thermally and chemically stable compounds which present an intense absorption in the red/near-infrared (IR) region of the solar spectrum with extinction coefficients (as high as 200 000 M-1 cm-1) and fluorescence quantum yields * To whom correspondence should be addressed. E-mail: tomas.torres@uam.es (T.T.); dirk.guldi@chemie.uni-erlangen.de (D.M.G.). † Universidad Autonoma de Madrid. ‡ Friedrich-Alexander-Universitat Erlangen-Nurnberg. § IMDEA-Nanociencia. Chem. Rev. 2010, 110, 6768–6816 6768

Covalent and noncovalent phthalocyanine-carbon nanostructure systems: synthesis, photoinduced electron transfer, and application to molecular photovoltaics.

Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

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Unique Diagnostic and Therapeutic Roles of Porphyrins and Phthalocyanines in Photodynamic Therapy, Imaging and Theranostics

Ruthenium and iridium complexes bearing porphyrin moieties: PDT efficacy against resistant melanoma cells

The Role of Photoactive Materials Based on Tetrapyrrolic Macrocycles in Antimicrobial Photodynamic Therapy

Some new N-substituted pyridazinones and triazolo[4,3-b]pyridazinones were synthesized, respectively, by simple alkylation and 1,3-dipolar cycloaddition of pyridazin-3-one with nitrile imines The regioselectivity of the reactions was ascertained by 1H, 13C NMR spectroscopy and X-ray diffraction of the synthesized compounds

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Alkylation and 1,3-Dipolar Cycloaddition of 6-Styryl-4,5-dihydro-2H-pyridazin-3-one: Synthesis of Novel N-Substituted Pyridazinones and Triazolo[4,3-b]pyridazinones

Porphyrin-porphyrin and porphyrin-chlorin dimers have been synthesized and evaluated for their photo-physical and in vivo photodynamic therapy properties. Two of them can become potential new photosensitizers. Study of the reactivity of meso-tetraaryl porphyrins, as dienophiles, in Diels-Alder transformations and as dipolarophiles in 1,3-dipolar cycloadditions, has been undertaken. New synthetic methodologies for certain chlorin, bacteriochlorin and isobacteriochlorin type macrocycles, with potential biological significance, have been established.

Porphyrin Derivatives: Synthesis and Potential Applications

Cellulose is the most abundant natural biopolymer and owing to its compatibility with biological tissues, it is considered a versatile starting material for developing new and sustainable materials from renewable resources. With the advent of drug-resistance among pathogenic microorganisms, recent strategies have focused on the development of novel treatment options and alternative antimicrobial therapies, such as antimicrobial photodynamic therapy (aPDT). This approach encompasses the combination of photoactive dyes and harmless visible light, in the presence of dioxygen, to produce reactive oxygen species that can selectively kill microorganisms. Photosensitizers for aPDT can be adsorbed, entrapped, or linked to cellulose-like supports, providing an increase in the surface area, with improved mechanical strength, barrier, and antimicrobial properties, paving the way to new applications, such as wound disinfection, sterilization of medical materials and surfaces in different contexts (industrial, household and hospital), or prevention of microbial contamination in packaged food. This review will report the development of porphyrinic photosensitizers supported on cellulose/cellulose derivative materials to achieve effective photoinactivation. A brief overview of the efficiency of cellulose based photoactive dyes for cancer, using photodynamic therapy (PDT), will be also discussed. Particular attention will be devoted to the synthetic routes behind the preparation of the photosensitizer-cellulose functional materials.

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Maria A. F. Faustino

Papers

Ruthenium and iridium complexes bearing porphyrin moieties: PDT efficacy against resistant melanoma cells

The Role of Photoactive Materials Based on Tetrapyrrolic Macrocycles in Antimicrobial Photodynamic Therapy

Alkylation and 1,3-Dipolar Cycloaddition of 6-Styryl-4,5-dihydro-2H-pyridazin-3-one: Synthesis of Novel N-Substituted Pyridazinones and Triazolo[4,3-b]pyridazinones

Porphyrin Derivatives: Synthesis and Potential Applications

Porphyrin Photosensitizers Grafted in Cellulose Supports: A Review