A new approach to achieving selectivity for photodynamic therapy based upon the reversible off/on switching of the key therapeutic property (singlet oxygen generation) of a supramolecular photonic therapeutic agent (SPTA) in response to an external stimulus in the surrounding microenvironment is described. A series of SPTA analogues with pH responsive receptors of varying pKa are presented, in which the generation of singlet oxygen is shown to be dependent upon a proton source. For example, systems have been constructed such that the excited state energy of the photosensitizer can be decayed by a rapid photoinduced electron transfer (PET) mechanism, resulting in virtually no singlet oxygen being generated, but when the amine receptor is protonated the PET mechanism does not operate and singlet oxygen is produced. In vitro efficacy demonstrated that the SPTA derivatives can be activated within cells and one analogue is measured to have an EC50 value of 5.8 nM when assayed in the MRC5 cell line.

The value of the FIC index as a predictor of synergy has been investigated using the antibacterial agents alafosfalin and cephalexin combined together with themselves in fully blind experiments. Under the conditions used, even weak interaction (FIC index 0.5-0.99) proved to be statistically highly significant. The use of such fully controlled blind studies would greatly enhance the credibility of many of the claims of synergy published in the literature. The representation of results as average isobolograms is only of value with combinations which show moderate to strong interaction.

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Summary Single-crystal X-ray diffraction analysis (SCXRD) constitutes a universal approach for the elucidation of molecular structure and the study of crystalline forms. However, the discovery of viable crystallization conditions remains both experimentally challenging and resource intensive in both time and the quantity of analyte(s). We report a robot-assisted, high-throughput method for the crystallization of organic-soluble small molecules in which we employ only micrograms of analyte per experiment. This allows hundreds of crystallization conditions to be screened in parallel with minimal overall sample requirements. Crystals suitable for SCXRD are grown from nanoliter droplets of a solution of analyte in organic solvent(s), each of which is encapsulated within an inert oil to control the rate of solvent loss. This encapsulated nanodroplet crystallization methodology can also be used to search for new crystal forms, as exemplified through both our discovery of a new (13 th ) polymorph of the olanzapine precursor ROY and SCXRD analysis of the “uncrystallizable” agrochemical dithianon.

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Microbial biofilms are composed of a hydrated matrix of biopolymers including polypeptides, polysaccharides and nucleic acids and act as a protective barrier and microenvironment for the inhabiting microbes. While studying marine biofilms, we observed that supernatant produced by a marine isolate of Bacillus licheniformis was capable of dispersing bacterial biofilms. We investigated the source of this activity and identified the active compound as an extracellular DNase (NucB). We have shown that this enzyme rapidly breaks up the biofilms of both Gram-positive and Gram-negative bacteria. We demonstrate that bacteria can use secreted nucleases as an elegant strategy to disperse established biofilms and to prevent de novo formation of biofilms of competitors. DNA therefore plays an important dynamic role as a reversible structural adhesin within the biofilm.

Complementary synthetic routes to a new class of near IR fluorophores are described. These allow facile access (four synthetic steps) to the core fluorophore and substituted derivatives with emissions between 740 and 780 nm in good quantum yields.Surprisingly few fluorescent probes emit in the near-IR region with high quantum yields. 1, 2 Such compounds are valuable for intracellular imaging because autofluorescence in cells tends to obscure emissions at wavelengths below approximately 550 nm, but this factor becomes less of an issue at longer wavelengths. Probes that emit in the 750 -900 nm region are, therefore, relatively easy to visualize in vivo. 3 Cyanine dyes are currently the most widely used probes for this wavelength region, but their quantum yields and photostabilities are sub-optimal. 4 Thus there is need for new fluorescent probes that emit efficiently above 750 nm. Dyes based on the 5-6-5 fused BODIPY ring system A are popular in biotechnology because they tend to have relatively sharp fluorescence emission characteristics, and high quantum yields. 5 However, the emission wavelengths of most BODIPY dyes are between 530 and 630 nm, and this is sub-optimal for intracellular or tissue imaging. Previous work by Burgess et al ,6-8 and others, 9,10 successfully explored a modification strategy for shifting BODIPYfluorescence emissions to the red ( Figure 1). Adaptation of the core fluorophore scaffold by intramolecular B-O ring formation to produce the 6,6-5-6-5-6,6 ring system B gave a ca 65 nm bathochromatic shift (compare C and D), 11 but the fluorescence emission wavelengths were less than 700 nm. 12O'Shea and co-workers have demonstrated that BF 2 chelated tetraaryl-substituted azadipyrromethenes E, fluoresce with wavelength maxima between 670-720 nm with paraoriented electron donating groups being particularly effective in enhancing the red-shifted fluorescence, eg F (Figure 2). 13-19 This is close to the 750 -1,400 nm region at which light permeation through tissue is most effective. Subsequently, it was shown that derivatives with extended aromatic groups do emit in near-IR region. 20 The premise of this paper is that it would be advantagous to "hybridize" the structure B and E to shift their emissions beyond 750 nm. On the basis of the structures shown in Figure 1 it was therefore logical to introduce an intramolecular B,O-chelate on a tetraaryl aza-BODIPY scaffold eg G. The studies described here feature compound 1 of this type; it emerges that they can emit in this region.Scheme 1 shows one approach to the synthesis of the target class 1 from the precursors 2a-d which can be synthesized in four steps from commercially available materials. 21 A solid state X-ray structure determination of 2a illustrated that both 2-MeOC 6 H 4 rings lie out of the plane of the central chromophore with torsion angles of 42.7° and 61.4° (Supporting Information). Compounds 1 were obtained from the corresponding 2 by treatment with boron tribromide in dichloromethane. We anticipated that demethylation of the...

BACKGROUND: Photodynamic therapy (PDT) is a treatment modality for a range of diseases including cancer. The BF 2 -chelated tetraaryl-azadipyrromethenes (ADPMs) are an emerging class of non-porphyrin PDT agent, which have previously shown excellent photochemical and photophysical properties for therapeutic application. Herein, in vivo efficacy and mechanism of action studies have been completed for the lead agent, ADMP06. METHODS: A multi-modality imaging approach was employed to assess efficacy of treatment, as well as probe the mechanism of action of ADPM06-mediated PDT. RESULTS: Tumour ablation in 71% of animals bearing mammary tumours was achieved after delivery of 2 mg kg À1 of ADPM06 followed immediately by light irradiation with 150 J cm À2 . The inherent fluorescence of ADPM06 was utilised to monitor organ biodistribution patterns, with fluorescence reaching baseline levels in all organs within 24 h. Mechanism of action studies were carried out using dynamic positron emission tomography and magnetic resonance imaging techniques, which, when taken together, indicated a decrease in tumour vascular perfusion and concomitant reduction in tumour metabolism over time after treatment. CONCLUSION: The encouraging treatment responses in vivo and vascular-targeting mechanism of action continue to indicate therapeutic benefit for this new class of photosensitiser.