Superhydrophobic Surfaces as a Source of Airborne Singlet Oxygen through Free Space for Photodynamic Therapy

Abstract

A superhydrophobic (SH) sandwich system has been developed to enable "contact-free" airborne singet oxygen ( O ) delivery to a water droplet. The contact-free feature means that the sensitizer is physically separated from the droplet, which presents opportunities for photodynamic therapy (PDT). Trapping of airborne 1 O 2 in a H 2 O droplet residing on a lower SH surface was monitored with 9,10-anthracene dipropionate dianion by varying distances to an upper 1 O 2generating surface. Short distances of 20 µm efficiently delivered airborne 1 O 2 to the droplet in single-digit picomolar steady-state concentrations. Delivery decreases linearly with distance, but 50% of the 1 O 2 steady-state concentration is trapped at a distance of 300 µm from the generating surface. The 1270 nm luminescence intensity was measured within the SH sandwich system confirming the presence of airborne 1 O 2 . Physical quenching of 1 O 2 to ground-state 3 O 2 by the water droplet itself; and both physical and chemical quenching of 1 O 2 by the water droplet containing the trap 9,10-anthracene dipropionate dianion is observed. Unlike a majority of work in the field of PDT with dissolved sensitizers, where 1 O 2 diffuses short (hundreds of nanometer) distances, we show the delivery of airborne 1 O 2 via a superhydrophobic surface is effective through-air in tenths of millimeter distances to oxidize an organic compound in water. Our results provide not only potential relevance to PDT, but also surface bacterial inactivation processes.

Interparticle Delivery and Detection of Volatile Singlet Oxygen at Air/Solid Interfaces

“…We sought an optimal 1 O 2 photogeneration by the PS particles to allow a view of the through-space 1 O 2 process. In a previous study, we were not able to obtain direct lifetime measurements for airborne 1 O 2 generated on a superhydrophobic surface embedded with phthalocyanine particles. On that occasion, due to low phosphorescence emission, time resolution was not possible and only variations in the intensity were monitored.…”

“…Our three-phase interparticle reactive oxygen delivery system provides proof of concept for particle sensitization, reactive oxygen transfer in air, and oxidative damage to adjacent solid. This particle–air–particle 3-phase system connects to fields of atmospheric chemistry, environmental chemistry, and photochemistry with surface trapping agents, and also relevance of bi- and triphasic phenomena in 1 O 2 oxidation chemistry. − ,− That the amount of anthracene quencher loaded was linearly dependent, provides a key reference point for compound quenching on environmental surfaces for potential extrapolation, where trapping can increase steeply with loadings of oxophilic traps. We provide mechanistic evidence for the transfer of airborne 1 O 2 during the photooxidation of anthracene compounds adhered to particles.…”

“…Recently, direct laser techniques were carried out to measure singlet oxygen quantum yields (Φ Δ ) by NOM sensitization by monitoring the 1 O 2 phosphorescence directly with Φ Δ values of 0.6–3.8% . Only limited number of studies have focused on solid–air–solid systems − or how airborne 1 O 2 interacts with natural and artificial surfaces. ,, …”

Self-Sterilizing 3D-Printed Polylactic Acid Surfaces Coated with a BODIPY Photosensitizer

“…Strategies to anchor the PS to platforms that allow its posterior recovery have been investigated. In this regard, PS were immobilized/incorporated on magnetic nanoparticles, silicon dioxide, and natural and synthetic polymers. − For instance, polymeric nanofiber of polyurethane, polystyrene, polycaprolactone, and polyamide were doped with a tetraphenylporphyrin presenting a long-duration activity against Escherichia coli due to the generation of singlet oxygen ( 1 O 2 ) upon light activation of the material . Valkov et al prepared polymeric films of polystyrene with rose bengal (RB) or methylene blue as a PS, yielding a great bacterial eradication.…”