From this point of view, Mieszawska et al. devised a method for the synthesis of lipidcoated PLGA nanoparticles loaded with nanocrystals . Their approach is based on the conjugation of AuNCs4a and CdSe core-CdS-CdZnS-ZnS multilayer shell QDs4b to PLGA polymers through an esterification reaction between the COOH groups of 11mercaptoundecanoic acid (MUA) ligands and OH groups of PLGA polymers. When evaluating the contrast effect of the CSHNs systems on J774A macrophages using the imaging technique CT, the researchers found that the probes exhibited much higher CT contrast and brighter fluorescence compared with commercially available iodine-based contrast agents. This study shows that the use of nanoparticles is not limited to the delivery of therapeutic agents in a specific area, but could also be extended to monitoring biomarkers in the body. This idea, of course, paves the way for nanocarrier-based theranostic systems that enable simultaneous imaging and treatment.