Fig. 2 |. Overview of the approaches used for synthesizing, conjugating and purifying nanomaterial-based contrast agents.
a, Nano-based contrast agents have traditionally been synthesized using aqueous and organic solvents. Recent syntheses based on green chemistry, biological precursors, microfluidics and artificial intelligence (AI) have become increasingly utilized for nanomaterial fabrication. b,c, Surface modification (part b) and/or functionalization (part c) is performed to render the agents viable for bioimaging applications. d, The agents are further purified to remove impurities before in vitro and in vivo evaluation. EDC, N-ethyl-N’-(3-dimethylaminopropyl) carbodiimide; MWCO, molecular weight cut-off; NHS, N-hydroxysuccinimide; PEG, polyethylene glycol. Part c reprinted from ref. 86, CC BY 4.0.