Review of gold nanoparticles: synthesis, properties and applications

Gold nanoparticles (AuNPs) exhibit exceptional physicochemical properties, notably localized surface plasmon resonance (LSPR), enabling diverse applications in biomedicine, molecular imaging (CT/PAI/MRI), photothermal therapy (PTT), and targeted drug delivery. This review systematically examines synthesis strategies, emphasizing pulsed laser ablation in liquid (PLAL) as a surfactant-free, eco-friendly “top-down” method producing pristine 5–50 nm AuNPs via plasma plume confinement and cavitation-induced nucleation. Complementary “bottom-up” green biosynthesis leverages plant/fruit extracts (polyphenols/flavonoids), microorganisms, and fungi (nitrate reductase) to yield biofunctionalized AuNPs (10–80 nm) with inherent stability for theranostics. Comparative analyses highlight PLAL’s superiority in purity/yield compared to chemical methods, while biological methods excel in scalability and multifunctionality. Shape-dependent plasmonic heating: nanorods achieve ΔT = 45–55 °C vs. spheres (25 °C), underpinning PTT efficacy. The review elucidates targeting strategies (passive EPR vs. active ligand-receptor), hybrid imaging, and challenges, including EPR heterogeneity, synthesis reproducibility, and clinical translation. Future directions prioritize fs-PLAL optimization, biohybrid architectures, and multimodal AuNP platforms for precision oncology.