Synthesis and Characterization of Star-Shaped Block Copolymer sPCL-b-PEG-GA

Abstract

Compared to linear polymers with the same molecular weight, star-shaped polymers have the superiority of drug loading and delivery. The glycyrrhetinic acid (GA) from licorice is remarkably characteristic of liver distribution and liver cells targetability. In this paper, four-armed star-shaped polycaprolactone was synthesized and amino polyethylene glycol was modified by glycyrrhetinic acid (NH2-PEG-GA). Then the condensation reaction between the two above polymers finally produced four-armed star-shaped poly(ethylene glycol)-b-poly(ε-caprolactone) block copolymer (sPCL-b-PEG-GA). The structures of the intermediates and product were characterized by1H NMR. The results indicated that the structure and molecular weight of sPCL-b-PEG-GA can be controlled by the varied ratios of pentaerythritol (PTOL) toε-caprolactone (ε-CL) in the presence of stannous octoate (Sn(Oct)2), and the amphiphilic copolymer sPCL-b-PEG-GA consists of PTOL as core, PCL as inner hydrophobic segments, PEG as external hydrophilic segments, and terminal glycyrrhetic acid as targeting ligand. The work explored a new synthesis route of star poly(ethylene glycol)-b-poly(ε-caprolactone) copolymer with liver targetability. The star-shaped polymer is expected to be an efficient drug carrier.

Hydrolytic degradation of star-shaped poly(ε-caprolactone)s with different number of arms and their cytotoxic effects

“…The most used multifunctional cores to produce three, four, and six armed star polymers were trimethylolpropane (TMP), ditrimethylolpropane (diTMP), pentaerythritol (PERT), dipentaerythritol (diPERT), but a comprehensive list of star PCLs includes also glycerol, erythritol, sorbitol, xylitol, etc. 11,[16][17][18] The multi-armed structure was found to have great impact on the thermal properties and crystallization and some studies reported that the melting temperature (T m ) and degree of crystallinity (X c ) are affected by both the molecular weight and number of arms. 19 The molecular weight and multi-armed structure also played an important role in thermal stability of sPCL, which is important from the thermal processing aspect.…”

Glycyrrhetinic Acid Mediated Drug Delivery Carriers for Hepatocellular Carcinoma Therapy

“…51 An increasing interest was focused on star-shaped polymers which have higher drug loading capacity (three or more times) than linear polymers. 52 Zhang et al 53 combined the advantages of GA and star polymers as vector to design a novel livertargeted delivery system. This copolymer, four-armed starshaped poly(ethylene glycol)-b-poly(epsilon-caprolactone) block copolymer (sPCL-b-PEG-GA), was composed of a core of pentaerythritol (PTOL), the inner hydrophobic segments of PCL and external segments of PEG, and more importantly, terminal GA as targeting ligand.…”