Development of novel tunable light scattering coating materials for fiber optic diffusers in photodynamic cancer therapy

To homogenize light emitted from fiber optic diffusers for photodynamic therapy (PDT), novel coating materials with tunable properties were designed. A class VI medical grade UV-curable acrylic resin for biomedical applications was used for the polymer matrix, and titanium dioxide (TiO₂) was added to the resin as a scattering agent. UV-curability of coatings containing TiO₂ was significantly influenced by the grade and surface treatment of the TiO₂ studied. Despite using a free-radical system without inert gas protection, all samples demonstrated considerable thermal postcuring. A novel TiO₂ surface treatment methodology was developed based on unsaturated alkoxyorganosilanes combined with unsaturated carboxylic acids for compatibilizing TiO₂ for use in the resin material studied. By adjusting the concentration of the surface-modifying agent, the scattering efficiency and UV curability can be controlled by decreasing the effective particle size and enhancing the dispersibility of the powder filler within the resin. This modification will enable fine-tuning of the effective size of TiO₂ particles to the wavelength of laser light to be scattered to maximize scattering efficiency in photodynamic cancer therapy and possibly also in other forms of cancer treatment (interstitial laser hyperthermia or interstitial laser photocoagulation).