Abstract
Amphiphilic block copolymers have attracted a great deal of attention in drug delivery systems. In this work, a series of monomethoxy-poly (ethylene glycol)-poly (ε-caprolactone-co-D,L-lactide) (MPEG-PCLA) copolymers with variable composition of poly (ε-caprolactone) (PCL) and poly (D,L-lactide) (PDLLA) were prepared via ring-opening copolymerization of ε-CL and D,L-LA in the presence of MPEG and stannous octoate. The structure and molecular weight were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The crystallinity, hydrophilicity, thermal stability and hydrolytic degradation behavior were investigated in detail, respectively. The results showed that the prepared amphiphilic MPEG-PCLA copolymers have adjustable properties by altering the composition of PCLA, which make it convenient for clinical applications. Besides, the drug loading properties were also studied. Docetaxel (DTX) could be entrapped in MPEG-PCLA micelles with high loading capacity and encapsulation efficiency. And all lyophilized DTX-loaded MPEG-PCLA micelles except MPEG-PCL micelles were readily re-dissolved in normal saline at 25 °C. In addition, DTX-loaded MPEG-PCLA micelles showed a slightly enhanced antitumor activity compared with free DTX. Furthermore, DTX micelles exhibited a slower and sustained release behavior in vitro, and higher DTX concentration and longer retention time in vivo. The results suggested that the MPEG-PCLA copolymer with the adjustable ratio of PCL to PDLLA may be a promising drug delivery carrier for DTX.
Highlights
Biocompatible and biodegradable amphiphilic block copolymers, which consist of hydrophilic and hydrophobic segments, have attracted considerable attention in the biomedical field, especially in drug delivery systems[1,2]
We assumed that the random copolymerization of ε-CL and D,L-LA in the presence of MPEG as initiator would result in the copolymers (MPEG-PCLA), which may have lower crystallinity, higher hydrophilicity, appropriate degradation rate and drug loading property compared with MPEG-PCL
The peaks around 3.30 ppm belonged to methyl protons of the methoxy units (CH3O-) and the sharp peaks around 3.65 ppm were attributed to methylene protons of the ethylene glycol units (-CH2CH2O-) in MPEG; the peaks around 5.10 ppm and 1.50 ppm belonged to the methylene protons and methyl protons of lactide units (-COCH(CH3)O-), respectively; the peaks around 2.30 ppm were attributed to ω-methylene protons of the caprolactone units (-COCH2CH2CH2CH2CH2O-), while the two peaks at 1.30 ppm and 1.60 ppm belonged to the repeat ethylene units
Summary
Biocompatible and biodegradable amphiphilic block copolymers, which consist of hydrophilic and hydrophobic segments, have attracted considerable attention in the biomedical field, especially in drug delivery systems[1,2]. These copolymers could self-assemble to form nanoscale micelles with a core-shell structure in aqueous solutions. (PCL) and poly(glycolide) (PGA), are a kind of extensively studied hydrophobic polymers with good biodegradability and biocompatibility[11,12]. Both of them are commercially available and have been approved for human use by FDA. We assumed that the random copolymerization of ε-CL and D,L-LA in the presence of MPEG as initiator would result in the copolymers (MPEG-PCLA), which may have lower crystallinity, higher hydrophilicity, appropriate degradation rate and drug loading property compared with MPEG-PCL
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