Synthesis and characterization of Gold-silica-ICG nanostars with photothermal effect and reactive species generation

ANDREOZZI, PATRIZIA ; DAVID GARA, PEDRO MAXIMILIANO; MOYA, SERGIO ; MÁRTIRE, DANIEL O.; MARTINEZ PORCEL, JOAQUÍN ; ARCE, VALERIA B.

Viña del Mar

Encuentro; XIV Encuentro Latino-Americano de Fotoquímica y Fotobiología (ELAFOT); 2019

Universidad de Chile.

When light couples with the oscillation frequency of the conduction electrons in the metal nanopartcles (NP), a so called localized surface plasmon resonance (LSPR) arises, which is revealed by a strong absorption band along with an efficient photo-to-heat conversion [1]. Photothermal therapy (PTT) and photodynamic therapy (PDT) are promising cancer treatments in which photo-to-heat conversion by nanoparticles and the activation of a photosensitizer (PS) occur in response to applied laser light. As a result of the photoirradiation, cytotoxic photothermal heating and reactive oxygen species (ROS) can trigger apoptotic and necrotic cancer cell death [2].Here we develop a multifunctional nanomaterial that could be used for simultaneously imaging and dual PTT and PDT treatment of the tumor.We have synthesized and characterized SiO2 NP funcionalized with gold NanoStars and Indocyanine Green (ICG), an amphiphilic carbocyanine dye that strongly absorbs and fluoresces in the NIR region of light, and produces singlet oxygen upon irradiation. The procedure employed for the synthesis of the nanomaterial was the layer-by-layer technique.TEM images showed core-shell NP of 600 nm diameter. UV-visible absorption spectra showed that the LSPR of the nanoparticles is located between 600 and 900 nm. These wavelengths are within the NIR window, where light has its maximum depth of penetration in tissue. Suspensions of the unfunctionalized silica NP (SiO2), silica NP decorated with gold nanostars (SiO2@AuNS), and the NP containing both the gold nanostars and ICG (SiO2-ICG@AuNS) were irradiated with a 800 nm laser and the temperature was measured at different irradiation times. Results showed that there is a photothermal effect for the suspensions of the gold-containing nanomaterials, since the temperature increase observed for these suspensions is larger than those observed upon irradiation of water and a calorimetric reference used for comparison. The production of singlet oxygen upon NIR irradiation was demostrated by employing the Singlet Oxygen Sensor Green probe. The generation of H2O2 was also investigated. These in vitro results seem to indicate that the nanomaterial is a good candidate to be employed in PTT and PDT.