Mixed-thiol functionalised gold nanoparticles for trastuzumab delivery: chemical interaction and photothermal therapeutic potential.

Small-sized gold nanoparticles (AuNPs) functionalised with hydrophilic thiols were investigated. Sodium 3-mercapto-1-sulfonate and 2-(diethylamino)ethanethiol hydrochloride were used as stabilising agents in a wet synthesis approach to provide a stable colloidal system. AuNPs were loaded with the antibody trastuzumab (TZ) to evaluate the potential use of the system for photothermal-assisted controlled drug release. Furthermore, to gain a deeper understanding of the chemical interactions occurring at the interface between TZ and the surface thiols of the nanoparticles, FT-IR studies were performed both in the solid state and in suspension, suggesting a strong interaction between the surface thiols and the amidic functional groups of TZ. The photothermal (PT) behaviour of the pristine AuNPs was investigated under continuous-wave laser irradiation at 532 nm, matching the plasmon resonance band of the gold nanoparticles, resulting in an up to 20 °C temperature increase. FT-IR measurements were also carried out after laser irradiation to evaluate the potential for a controlled release of TZ from the nanoparticle surface, suggesting that light irradiation can trigger the release of the drug from the AuNPs surface, with no detrimental effect from the temperature increase. Finally, SAXS studies enabled the investigation of TZ loading and release kinetics via in situ studies over 3 hours. This work provided a detailed investigation of the interfacial chemical interactions, also giving a dual potential application of the hybrid, evaluating its use for PT therapy and for PT-assisted controlled release of the antibody.