Hydrophilic Gold Nanoparticles as Anti-PD-L1 Antibody Carriers: Synthesis and Interface Properties

Amino and sulfonate ending groups thiols are used as functionalizing agents to stabilize of gold nanoparticles (AuNPs), obtaining hydrophilic AuNPs with a 10–20 nm diameter range and tunable surface charge. The nanomaterial is extensively characterized from a physicochemical point of view by UV–Vis and Fourier-transform infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, synchrotron radiation X-ray photoelectron spectroscopy (XPS), and dynamic light scattering to investigate the bonding between the two thiols and the metal surface. Systems are also biologically characterized on human multiforme glioblastoma T98G cells to understand their behavior in cell culture for biomedical applications. NMR and XPS studies evidence the presence of amino ending thiols with different chain lengths, 6-amino-1-hexanethiol hydrochloride (6EA) or cysteamine (CY) and sodium 3-mercapto-1-propanesulfonate (3MPS) on the metal surface: the relative molar ratio between the thiols bound to the AuNPs (3MPS/6EA or 3MPS/CY) is measured. On selected samples, the anti-PD-L1 antibody is loaded using AuNPs/antibody combination in a 2:1 weight ratio. Comparing different AuNPs concentrations (10 and 50 µg mL−1), the effect on colony-forming capacity after 24 h exposure is evaluated. The synthesized AuNPs are nontoxic, and they do not affect cell proliferation. These small particles can be used for targeting, opening tangible and interesting perspectives for further biomedical studies.