Biomass is an important feedstock for the renewable production of fuels, chemicals, and energy. As of 2005, over 3% of the total energy consumption in the United States was supplied by biomass, and it recently surpassed hydroelectric energy as the largest domestic source of renewable energy. Similarly, the European Union received 66.1% of its renewable energy from biomass, which thus surpassed the total combined contribution from hydropower, wind power, geothermal energy, and solar power. In addition to energy, the production of chemicals from biomass is also essential; indeed, the only renewable source of liquid transportation fuels is currently obtained from biomass.

The Catalytic Valorization of Lignin for the Production of Renewable Chemicals

Renewable Resources Robert-Jan van Putten,†,‡ Jan C. van der Waal,† Ed de Jong,*,† Carolus B. Rasrendra,‡,⊥ Hero J. Heeres,*,‡ and Johannes G. de Vries* †Avantium Chemicals, Zekeringstraat 29, 1014 BV Amsterdam, the Netherlands ‡Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands DSM Innovative Synthesis BV, P.O. Box 18, 6160 MD Geleen, the Netherlands Department of Chemical Engineering, Institut Teknologi Bandung, Ganesha 10, Bandung 40132, Indonesia

Hydroxymethylfurfural, A Versatile Platform Chemical Made from Renewable Resources

1.1 Photodynamic Therapy and Imaging
The purpose of this review is to present the current state of the role of imaging in photodynamic therapy (PDT). In order for the reader to fully appreciate the context of the discussions embodied in this article we begin with an overview of the PDT process, starting with a brief historical perspective followed by detailed discussions of specific applications of imaging in PDT. Each section starts with an overview of the specific topic and, where appropriate, ends with summary and future directions. The review closes with the authors’ perspective of the areas of future emphasis and promise. The basic premise of this review is that a combination of imaging and PDT will provide improved research and therapeutic strategies.

PDT is a photochemistry-based approach that uses a light-activatable chemical, termed a photosensitizer (PS), and light of an appropriate wavelength, to impart cytotoxicity via the generation of reactive molecular species (Figure 1a). In clinical settings, the PS is typically administered intravenously or topically, followed by illumination using a light delivery system suitable for the anatomical site being treated (Figure 1b). The time delay, often referred to as drug-light interval, between PS administration and the start of illumination with currently used PSs varies from 5 minutes to 24 hours or more depending on the specific PS and the target disease. Strictly speaking, this should be referred to as the PS-light interval, as at the concentrations typically used the PS is not a drug, but the drug-light interval terminology seems to be used fairly frequently. Typically, the useful range of wavelengths for therapeutic activation of the PS is 600 to 800 nm, to avoid interference by endogenous chromophores within the body, and yet maintain the energetics necessary for the generation of cytotoxic species (as discussed below) such as singlet oxygen (1O2). However, it is important to note that photosensitizers can also serve as fluorescence imaging agents for which activation with light in the 400nm range is often used and has been extremely useful in diagnostic imaging applications as described extensively in Section 2 of this review. The obvious limitation of short wavelength excitation is the lack of tissue penetration so that the volumes that are probed under these conditions are relatively shallow.






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Figure 1


(A) A schematic representation of PDT where PS is a photoactivatable multifunctional agent, which, upon light activation can serve as both an imaging agent and a therapeutic agent. (B) A schematic representation of the sequence of administration, localization and light activation of the PS for PDT or fluorescence imaging. Typically the PS is delivered systemically and allowed to circulate for an appropriate time interval (the “drug-light interval”), during which the PS accumulates preferentially in the target lesion(s) prior to light activation. In the idealized depiction here the PS is accumulation is shown to be entirely in the target tissue, however, even if this is not the case, light delivery confers a second layer of selectivity so that the cytotoxic effect will be generated only in regions where both drug and light are present. Upon localization of the PS, light activation will result in fluorescence emission which can be implemented for imaging applications, as well as generation cytotoxic species for therapy. In the former case light activation is achieved with a low fluence rate to generate fluorescence emission with little or no cytotoxic effect, while in the latter case a high fluence rate is used to generate a sufficient concentration of cytotoxic species to achieve biological effects.

/pdf/imaging-and-photodynamic-therapy-mechanisms-monitoring-and-76rc7acuq5.pdf

Imaging and photodynamic therapy: mechanisms, monitoring, and optimization.

Hydrothermal technologies are broadly defined as chemical and physical transformations in high-temperature (200–600 °C), high-pressure (5–40 MPa) liquid or supercritical water. This thermochemical means of reforming biomass may have energetic advantages, since, when water is heated at high pressures a phase change to steam is avoided which avoids large enthalpic energy penalties. Biological chemicals undergo a range of reactions, including dehydration and decarboxylation reactions, which are influenced by the temperature, pressure, concentration, and presence of homogeneous or heterogeneous catalysts. Several biomass hydrothermal conversion processes are in development or demonstration. Liquefaction processes are generally lower temperature (200–400 °C) reactions which produce liquid products, often called “bio-oil” or “bio-crude”. Gasification processes generally take place at higher temperatures (400–700 °C) and can produce methane or hydrogen gases in high yields.

/pdf/thermochemical-biofuel-production-in-hydrothermal-media-a-57itjyvhnt.pdf

Thermochemical biofuel production in hydrothermal media: A review of sub- and supercritical water technologies

2. Activatable Photosensitizer Design Considerations 2842 2.1. Activation Strategy 2842 2.2. Photosensitizer Selection 2844 2.3. Photosensitizer Conjugation 2845 3. Examples of Activatable Photosensitizers 2845 3.1. Environment-Activated Photosensitizers 2845 3.2. Enzyme-Activated Photosensitizers 2846 3.3. Nucleic Acid-Activated Photosensitizers 2852 3.4. Other Activation Mechanisms 2853 4. Conclusion and Outlook 2855 5. Abbreviations 2855 6. Acknowledgments 2855 7. References 2855

/pdf/activatable-photosensitizers-for-imaging-and-therapy-59czygeqqf.pdf

Activatable photosensitizers for imaging and therapy

A most useful strategy has been devised for the synthesis of 3-substituted pyrroles on the basis of the kinetic electrophilic substitution of 1-(triisopropylsilyl) pyrrole (1) at the β position and subsequent fluoride ion induced desilylation. This now becomes the preferred route to 3-monosubstituted pyrroles

N-(Triisopropylsilyl)pyrrole. A progenitor "par excellence" of 3-substituted pyrroles

Ketene chemistry: the second golden age

Preparation of β-lactams by [2+2] cycloaddition of ketenes and imines ☆

The development of activatable photodynamic therapy (PDT) has demonstrated a utility for effective photosensitizer quenchers. However, little is known quantitatively about Forster resonance energy transfer (FRET) quenching of photosensitizers, even though these quenchers are versatile and readily available. To characterize FRET deactivation of singlet oxygen generation, we attached various quenchers to the photosensitizer pyropheophorbide-α (Pyro) using a lysine linker. The linker did not induce major changes in the properties of the photosensitizer. Absorbance and emission wavelength maxima of the quenched constructs remained constant, suggesting that quenching by ground-state complex formation was minimal. All quenchers sharing moderate spectral overlap with the fluorescence emission of Pyro (J ≥ 5.1 × 1013 M−1 cm−1 nm4) quenched over 90% of the singlet oxygen, and quenchers with weaker spectral overlap displayed minimal quenching. A self-quenched double Pyro construct exhibited intermediate quenching. ...

/pdf/fret-quenching-of-photosensitizer-singlet-oxygen-generation-2ppkhmmrp1.pdf

Thomas T. Tidwell

Papers

N-(Triisopropylsilyl)pyrrole. A progenitor "par excellence" of 3-substituted pyrroles

Ketene chemistry: the second golden age

Preparation of β-lactams by [2+2] cycloaddition of ketenes and imines ☆

FRET Quenching of Photosensitizer Singlet Oxygen Generation

Addition reactions of ketenes