Polydiacetylene-coated Gold Colloids: a Multifunctional Nanostructure for Theranostic Applications

We report on the synthesis and the plasmonic properties of hybrid nanostructures realized surrounding gold nanoparticles (AuNPs) with an external layer of poly(10,12-pentacosadiynoic acid). Three different sizes of AuNPs (3–5, 20, and 75 nm) were prepared by tailored synthetic methods, which were subsequently coated by an in-situ photopolymerization process. These colloids function as nanoscale thermosensors as demonstrated with 2D substrates obtained by drop-casting and by monitoring the inner temperature of human prostate cancer cells (PC3). By use of the Full Width at Half Height of a peak at 1447 cm−1 as an analytical parameter, a sensitivity of 0.11 cm−1/°C and a reading range between 25 and 125 °C were achieved. These constructs also exhibited intense SERS signaling, by laser irradiation at 638 nm, which enabled sensitive cellular imaging. Measurements on a set of PC3 cells demonstrated a significant and consistent AuNPs uptake [(5 ± 1.1) × 104 counts/μm2 with a Coefficient of variation of 23.6 %]. Furthermore, the proposed nanostructures demonstrated efficient light-to-heat conversion, leading to a significant temperature rise at the plasmonic surface upon irradiation. By leveraging this thermoplasmonic property, we achieved a localized temperature increase exceeding 125 °C in tumor cells upon laser irradiation. The combination of temperature sensing, SERS signaling, and photothermal effect makes these nanostructures promising candidates for diagnostic applications, cellular imaging, and cancer treatment.