Chemiluminescence as a PDT light source for microbial control

Chemiluminescence-Induced Free Radical-Promoted Cationic Polymerization

Chemiluminescence (CL) has recently been featured as a new external light source for various photoinduced reactions with attractive features such as eliminating continuous energy supply and advanced light source setups. In the present study, the free-radical-promoted cationic polymerization of cyclohexene oxide, n-butyl vinyl ether, and N-vinyl carbazole under CL irradiation is described. The method is based on the visible-light-induced generation of electron donor radicals from bis-(4-methoxybenzoyl)diethyl germane (BAG), bis(2,4,6-trimethylbenzoyl) phenyl phosphinate, and camphorquinone by CL illumination followed by electron transfer to diphenyl iodonium hexafluorophosphate (Ph₂ I⁺ PF₆ ^- ) to form corresponding cations capable of initiating cationic polymerization. The applicability of the process to network formation is also demonstrated by using a bifunctional monomer, tri(ethylene glycol) divinyl ether.

Photodynamic inactivation of S. aureus with a water-soluble curcumin salt and an application to cheese decontamination

In this study, the optimal parameters for the photodynamic inactivation (PDI) of Staphylococcus aureus in bacterial suspensions and in cheese were assessed using a water-soluble curcumin salt as the photosensitizer (PS).

Making and Breaking Chemical Bonds by Chemiluminescence

Chemiluminescent (CL) reactions are powerful analytical tools and are present in commercially available everyday objects such as glow sticks. Herein, the photons generated by chemiluminescence are exploited to induce covalent bond breakage and formation, using a chemically generated photonic field at ambient temperature through space as energy transducer. Remarkably, the generated photons enable both the cleavage of species generating radicals as well as the execution of [2 + 2] cycloadditions, demonstrating that disparate types of reactions can be triggered. The herein-presented photochemical concept establishes the field of CL-induced photochemistry, which is poised to enable photochemical transformations in situations where physical light sources, such as lamps, LEDs, and lasers cannot be employed, including in biological environments.

Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release

We describe progress on a one-step photodynamic therapy (PDT) technique that is simple: device tip delivery of sensitizer, oxygen and light simultaneously. Control is essential for their delivery to target sites to generate singlet oxygen. One potential problem is the silica device tip may suffer from biomaterial fouling and the pace of sensitizer photorelease is slowed. Here, we have used biomaterial (e.g. proteins, cells, etc.) from SQ20B head and neck tumors and whole blood for an assessment of fouling of the silica tips by adsorption. It was shown that by exchanging the native silica tip for a fluorinated tip, a better nonstick property led to an increased sensitizer output by ~10%. The fluorinated tip gave a sigmoidal photorelease where singlet oxygen is stabilized to physical quenching, whereas the native silica tip with unprotected SiO-H groups gave a slower (pseudolinear) photorelease. A further benefit from fluorinated silica is that 15% less biomaterial adheres to its surface compared to native silica based on a bicinchoninic acid assay (BCA) and X-ray photoelectron spectroscopy (XPS) measurements. We discuss how the fluorination of the device tip increases biofouling resistance and can contribute to a new pointsource PDT tool.

Validation of photodynamic action via photobleaching of a new curcumin-based composite with enhanced water solubility

Motivated by the photochemical and photophysical properties of curcumin-based composites, the characteristics of a new curcumin-based water-soluble salt were investigated via absorption and fluorescence spectroscopy. Photobleaching was investigated using a set of LEDs in three different wavelengths (405 nm, 450 nm and 470 nm) to illuminate an aqueous solution of curcumin, evaluating its degradation for five different exposure times (0, 5, 15, 45 and 105 minutes). The results were compared with equivalent measurements of dark degradation and illumination in the presence of a singlet-oxygen quencher. Three solution concentrations (50, 100 and 150 μg/ml) were studied. To measure the fluorescence, it was used low power 405 nm excitation laser source. Time dependent photodegradation of curcumin was observed, as compared to the natural degradation of samples maintained on a dark environment. Two main absorption peaks were detected and their relation responded to both concentration and wavelength of the illumination source. A spectral correlation between absorption of curcumin and the emission bands of the sources showed an optimal spectral overlap for the 450 nm LED. For this source, photobleaching showed a less intense degradation on the presence of singlet oxygen quencher. This last result confirmed singlet oxygen production in vitro, indicating a strong potential of this composite to be used as a blue-light-activated photosensitizer.