In this work, glycyrrhetinic acid-modified chitosan (mGA-suc-CTS) used as liver targeted carrier for drug delivery, was prepared via hemisuccinate as a bridged group. The structure of the product was confirmed by IR and NMR methods and the degree of substitution (DS) of glycyrrhetinic acid groups was estimated via elemental analysis. Nanoparticles were formed by ionic gelation methold. The drug-loading and release behavior of the nanoparticles were investigated using BSA as the model drug. The results indicated that the carrier with a highest DS of 5.19% could be got and the DS was controlled by changing reaction temperature or feed ratio. BSA could be entrapped into the nanoparticles with the drug-loading ratio of 26.3% and the encapsulation efficiency of 81.5%. A sustained release over an 11-day period was observed in pH 7.4 in vitro.glycyrrhetinic acid, chitosan, drug delivery Hepatic targeted drug delivery systems (HTDDS) have attracted much more attention recently for their promising roles in increasing the efficiency of pharmaceutical agents for liver, reducing drug doses, and significantly decreasing the toxic side effects [1] . With the deepening understanding of the structure and function of the surface of cells, receptor-mediated targeted drug delivery systems have been extensively studied [2] . In brief, receptor-mediated targeting system is that the one functioned with ligands via chemical coupling or physical coating ways, reaching the desired sites by the special interaction between the ligands in the system and the receptors on the surface of the desired organ. Galactose compounds, which could be recognized by asialo-glycoprotein receptor (ASGP-R) presenting on the surface of hepatocytes, were extensively studied in HTDDS. Carriers modified with galactose compounds could be internalized by hepatocytes or accumulated in liver greatly in vitro or in vivo experiments [3,4] . However, further studies demonstrated the existence of inhibitors for ASGPR-binding ligands in the serum of patients suffered from liver disease, and the targeting effect of galactose compounds decreased greatly because of the presence of these inhibitors [5] . Therefore, it is quite necessary to discover new ligands with specific affinity to liver.Glycyrrhetinic acid (GA) and glycyrrhizin (GL) are the main components of liquorice, and glycyrrhetinic acid is the hydrolysis product of glycyrrhizin. The structures of glycyrrhetinic acid and glycyrrhizin are displayed in Figure 1. In 1990s, Negishi confirmed that the cell membrane of rat's liver contained specific high binding sites for glycyrrhetinic acid and glycyrrhizin [6]
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