Metabolizable dopamine-coated gold nanoparticle aggregates: Preparation, characteristics, computed tomography imaging, acute toxicity, and metabolism in vivo

To improve the computed tomography (CT) imaging ability and the toxicity of gold nanoparticles (AuNPs), hydrophilic dopamine (DPA)-coated gold nanoparticle (AuNP) (MSA AuNPs@DPA) aggregates (42 ± 2.65 nm) were obtained by assembling MSA AuNPs@DPA (5-6 nm) with the use of polyethyleneimine (PEI). They rapidly degraded into MSA AuNPs@DPA with PEI in blood. The acute toxicity test showed that the maximum tolerated doses of MSA AuNPs@DPA and MSA AuNPs@DPA aggregates were larger than 4.8 and 4.6 g kg^-1, respectively, which are much higher doses than those of the commonly used citric acid-stabilized AuNPs (CA AuNPs) (2.97 g kg^-1). The metabolic test in vivo showed that the elimination rates of MSA AuNPs@DPA aggregates and MSA AuNPs@DPA were 0.848 and 0.955, respectively. Most of the aggregates were eliminated by the kidney after 5 days and excreted by urine, whereas CA AuNPs remained in vivo and concentrated in some organs. The t_0.5 values of MSA AuNPs@DPA and MSA AuNPs@DPA aggregates were 24.28 and 43.68 h, respectively, meaning that MSA AuNPs@DPA aggregates had a much longer circulation time. Similarly, the CT absorption value of MSA AuNPs@DPA aggregates was much higher than that of the commonly used nonionic iodinated CT contrast agent iohexol and CA AuNPs at the same concentration. Thus, MSA AuNPs@DPA aggregates possess characteristics such as ease of fabrication, long circulation time, hypotoxicity, and excellent CT absorption value, which suggest their great potential applications in vivo.