³¹P NMR Evidence for Peroxide Intermediates in Lipid Emulsion Photooxidations: Phosphine Substituent Effects in Trapping

Abstract

Intralipid is a lipid emulsion used in photodynamic therapy (PDT) for its light scattering and tissue-simulating properties. The purpose of this study is to determine whether or not Intralipid undergoes photooxidation, and we have carried out an Intralipid peroxide trapping study using a series of phosphines [2'-dicyclohexylphosphino-2,6-dimethoxy-1,1'-biphenyl-3-sulfonate, 3-(diphenylphosphino)benzenesulfonate, triphenylphosphine-3,3',3''-trisulfonate and triphenylphosphine]. Our new findings are as follows: (1) An oxygen atom is transferred from Intralipid peroxide to the phosphine traps in the dark, after the photooxidation of Intralipid. 3-(Diphenylphosphino)benzenesulfonate is the most suitable trap in the series owing to a balance of nucleophilicity and water solubility. (2) Phosphine trapping and monitoring by P NMR are effective in quantifying the peroxides in H O. An advantage of the technique is that peroxides are detected in H O; deuterated NMR solvents are not required. (3) The percent yield of the peroxides increased linearly with the increase in fluence from 45 to 180 J cm based on our trapping experiments. (4) The photooxidation yields quantitated by the phosphines and P NMR are supported by the direct H NMR detection using deuterated NMR solvents. These data provide the first steps in the development of Intralipid peroxide quantitation after PDT using phosphine trapping and P NMR spectroscopy.

Surface-Radical Mobility Test by Self-Sorted Recombination: Symmetrical Product upon Recombination (SPR)

“…The fluence rate at a midpoint in between the bulbs was 21.8 ± 2.4 mW/cm 2 . 68 Upon irradiation, the temperature of the particles was found to rise by ∼10 °C, as we detected in a similar system previously. 5 This was measured by a thermos couple probe attached to an IR thermometer.…”

“…The nanoparticles were tumbled by a stirring paddle during the irradiation, where samples were placed at a distance of ∼10 cm midpoint between two 400 W metal halide lamps delivering light (280 < λ < 700 nm). The fluence rate at a midpoint in between the bulbs was 21.8 ± 2.4 mW/cm 2 . Upon irradiation, the temperature of the particles was found to rise by ∼10 °C, as we detected in a similar system previously .…”

Dark-Binding Process Relevant to Preventing Photosensitized Oxidation: Conformation-Dependent Light and Dark Mechanisms by a Dual-Functioning Diketone

“…Rises in temperature of ∼2–3 °C were observed for the sample solution under irradiation after 1 h. We have previously measured the fluency rate at a midpoint in between the bulbs to be 21.8 ± 2.4 mW/cm 2 . 34 The tail of the absorption of dione 1 (280–310 nm) overlaps with the output of the metal halide light, but this overlap is poor and nearly nonexistent with dicumyl peroxide 3 , phosphorane 4 , (MeO) 3 P, and (MeO) 3 P=O. The compound, ( n -C 3 H 7 O) 3 P=O, was used as an internal standard.…”

Heterogeneous photocatayltic deperoxidation with UV and visible light

“…The absorption spectra of sensitizers 1 and 2 , but not dicumyl peroxide, overlapped with the output of the light from metal halide lamps (see Supporting Information). At the location where the sample was placed, the fluence rate for the 280‐ to 750‐nm light source was measured using a custom dosimetry system and found to be 22 ± 2 mW/cm 2 as was previously measured with a power meter . After the irradiation, the sensitizer 1 or 2 , dicumyl peroxide and products were desorbed with a polar solvent, such as acetonitrile.…”