Synthesis of Siliconized Photosensitizers for Use in ¹O₂-Generating Silicone Elastomers: An Electron Paramagnetic Resonance Study

Abstract

Biomedical devices based on silicone are essential tools in modern healthcare but can be compromised by the development of device-acquired infections (DAIs). Unfortunately, the continued rise of antibiotic-resistant organisms makes current strategies to combat DAIs insufficient. Recently, the use of photoactive coatings that produce reactive oxygen species, specifically singlet oxygen (1O2), has attracted attention as a potential alternative to traditional strategies to prevent DAIs. However, the synthesis and characterization of silicone devices capable of 1O2 production are not trivial. Development is hindered by the incompatibility of photosensitizers with the silicone matrix and an incomplete understanding of how the method of incorporation impacts 1O2 production. Using the Piers–Rubinsztajn reaction, the photosensitizer 5,10,15,20-(tetra-3-methoxyphenyl)­porphyrin (TPMP) was derivatized to be compatible with silicone matrices without the assistance of solvents and could be incorporated either covalently or physically within silicone elastomers. Electron paramagnetic resonance measurements indicated that 1O2 was more efficiently generated from elastomers containing a covalently cross-linked TPMP derivative than their physically dispersed counterparts, due to the minimization of aggregates.

Hemin‐Doped, Ionically Crosslinked Silicone Elastomers with Peroxidase‐Like Reactivity

“…We have previously shown that porphyrins, which are typically insoluble in hydrophobic media, can be modified with silicone sidechains using the Piers–Rubinsztajn reaction, such that the products are readily and reliably incorporated in silicone elastomers; the properties of the porphyrin were retained. [ 29,30 ] That methodology requires aromatic alcohols or ethers on the porphyrin that, unfortunately, hemin does not possess. [ 31,32 ]…”

Learning from the trees: biomimetic crosslinking of silicones by phenolic coupling

“…Previous work has shown, in silicones, it is possible to use the oxidant aqueous H 2 O 2 with hemin as a peroxidase mimic in silicone, 35 or tethered porphyrins can be used for the photogeneration of the oxidant singlet oxygen. 36 Work exploring these oxidants for phenolic coupling is ongoing.…”

Tris(pentafluorophenyl)borane-catalyzed Hydride Transfer Reactions in Polysiloxane Chemistry—Piers–Rubinsztajn Reaction and Related Processes

“…The attachment of oligosiloxane chains to larger molecules makes them compatible with silicone elastomers. This approach was exploited by Brook and co-workers to link polysiloxanes via P-R condensation with a 5,10,15,20-(tetra-3-methoxyphenyl)porphyrine-Zn complex [ 125 ] ( Scheme 41 ), which is a photosensitizer. This modified porphyrin is well dispersed in the silicone material and may form covalent cross-links in the silicone matrix using vinyl groups at siloxane chain ends.…”