Photothermal nanomaterials have recently attracted significant research interest in therapeutic applications since they fulfill delivery and uptake requirement in biological paths. Photothermal agents which generate heat under NIR excitation can be designed to release drugs for chemotherapy or to kill the cancer cells for photothermal therapy. Silica nanoparticles have been used for drug release, sensing, therapy and bioimaging owing to the unique encapsulation and binding properties, however silica nanoparticles do not have intrinsic photothermal property. In this work, we hybridized mesoporous silica nanoparticles (MSN) with a diimmonium-based NIR dye, for the first time, and produced a robust photothermal agent. NIR dye which was synthesized by oxidization of an amine compound and an ion substitution reaction is water-insoluble unlike the FDA-approved photothermal indocyanine green (ICG) dye. Therefore, NIR dye was encapsulated into the mesopores of silica nanoparticles with the aid of surfactant interaction and made dispersible in aqueous media. Hybrid nanoparticles show very strong absorption within 800-1100 nm range. Absorption intensity is highly stable in physiological buffer solutions and pure water revealing successful binding of dye to the surfactant moieties. Hybrid photothermal nanoparticles possess a great heat generation performance under illumination with NIR laser with 915 nm-wavelength. Temperature increase is controlled with dye-loading percentage, nanoparticle concentration and laser power. Temperature of the nanoparticle solutions can rise to 42 °C and to 75 °C within 2 min at 1 W cm-2 and 5 W cm-2 excitation intensities, respectively. Nanoparticles remain colloidally stable and with unchanged photothermal heating performance after multiple laser-on/off cycles. Signal generation by pulsed excitation for photoacoustic imaging and NIR-responsive drug release using the nanoparticles are under investigation. New photothermally-functionalized silica nanoparticles with their facile preparation and controlled heat generation performance hold potential for various applications including biomedicine, environmental remediation, and actuators.

Photothermal nanomaterials have recently attracted significant research interest in therapeutic applications since they fulfill delivery and uptake requirement in biological paths. Photothermal agents which generate heat under NIR excitation can be designed to release drugs for chemotherapy or to kill the cancer cells for photothermal therapy. Silica nanoparticles have been used for drug release, sensing, therapy and bioimaging owing to the unique encapsulation and binding properties, however silica nanoparticles do not have intrinsic photothermal property. In this work, we hybridized mesoporous silica nanoparticles (MSN) with a diimmonium-based NIR dye, for the first time, and produced a robust photothermal agent. NIR dye which was synthesized by oxidization of an amine compound and an ion substitution reaction is water-insoluble unlike the FDA-approved photothermal indocyanine green (ICG) dye. Therefore, NIR dye was encapsulated into the mesopores of silica nanoparticles with the aid of surfactant interaction and made dispersible in aqueous media. Hybrid nanoparticles show very strong absorption within 800-1100 nm range. Absorption intensity is highly stable in physiological buffer solutions and pure water revealing successful binding of dye to the surfactant moieties. Hybrid photothermal nanoparticles possess a great heat generation performance under illumination with NIR laser with 915 nm-wavelength. Temperature increase is controlled with dye-loading percentage, nanoparticle concentration and laser power. Temperature of the nanoparticle solutions can rise to 42 °C and to 75 °C within 2 min at 1 W cm^-2^ and 5 W cm^-2^ excitation intensities, respectively. Nanoparticles remain colloidally stable and with unchanged photothermal heating performance after multiple laser-on/off cycles. Signal generation by pulsed excitation for photoacoustic imaging and NIR-responsive drug release using the nanoparticles are under investigation. New photothermally-functionalized silica nanoparticles with their facile preparation and controlled heat generation performance hold potential for various applications including biomedicine, environmental remediation, and actuators.

Hybridization of mesoporous silica nanoparticles with hydrophobic NIR dye for photothermal applications

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ACS Fall 2022

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