Au-poly(lactic-co-glycolic) acid complex nanoparticles as ultrasound contrast agents: Preparation, characterization and in vitro study.

The present study aimed to prepare and characterize an Au-poly(lactic-co-glycolic) acid (PLGA) complex, surfaced with gold nanoparticles (GNPs), and to assess its use as an ultrasound contrast agent for in vitro imaging. PLGA nanoparticles (NPs) were prepared by a modified double‑emulsion solvent evaporation method. GNPs were prepared via reduction with sodium citrate. Au‑PLGA complexes were created through the binding of polyethylene glycosylated GNPs to the surface of PLGA NPs. Various physical characteristics of PLGA NPs, GNPs and Au‑PLGA complexes, including morphology, size, dispersion, ζ potential and stability were observed and measured. The study of the in vitro imaging capability of the Au‑PLGA complex was conducted by setting multi‑parameter imaging conditions. The average sizes of PLGA NPs, GNPs and the Au‑PLGA complex were 144.5±30.28, 21.42±1.56 and 359.4±67.94 nm, respectively. Transmission electron microscopy (TEM) revealed that PLGA NPs and GNPs were spherically shaped, but GNPs had smooth surface while PLGA NPs had a capsular morphology with a wrinkled surface and large voids. The maximum absorption peak of 20 nm GNPs was 508 nm while that of the Au‑PLGA complex was 515 nm on an ultraviolet‑visible absorption spectrum curve. The results of TEM and the redshift spectrum demonstrated that GNPs successfully bound to the surface of the PLGA NPs. The complex demonstrated good stability and its size changed little over time. In vitro imaging experiments revealed that the Au‑PLGA complex had a good imaging ability. The present study demonstrated that the Au‑PLGA complex is a promising novel ultrasound contrast agent.