Reversible-deactivation anionic alternating ring-opening copolymerization of epoxides and cyclic anhydrides: access to orthogonally functionalizable multiblock aliphatic polyesters

A versatile catalyst system for the synthesis of narrow dispersity polyesters from readily available epoxides and anhydrides is reported.

The alternating copolymerization of epoxides and cyclic anhydrides is an increasingly popular route to aliphatic polyesters that are of interest as biodegradable replacements for petroleum-based polymers and for use in the biomedical field. However, broad and bimodal molecular weight distributions in these polymerizations continues to be an issue, limiting synthesis of multiblock copolymers. By use of a bifunctional catalytic system, the reversible-deactivation anionic alternating ring-opening copolymerization of epoxides and cyclic anhydrides gives unimodal polymers with Đ values generally less than 1.07. This allowed for the formation of well-defined triblock copolymers. Additionally, by incorporating both aldehyde and alkene functionalities into the polymer, orthogonal post-polymerization modification was achieved, giving access to well-defined highly modifiable aliphatic polyesters.

Evaluation of in vitro toxicity of polymeric micelles to human endothelial cells under different conditions

Polymeric micelles have been extensively studied in the area of antitumor therapy, and more recently explored as nanocarriers for atherosclerosis. These applications of polymeric micelles in biomedicine will increase their contact with human blood vessels. However, few studies have considered the interactions between polymeric micelles and endothelial cells, especially in a complex system. This study used human umbilical vein endothelial cells (HUVECs) as an in vitro model for endothelial cells to investigate the toxic effects of methoxy-poly(ethylene glycol)-poly(d,l-lactide) (MPEG-PLA) based micelles. In addition, an endoplasmic reticulum stress inducer thapsigargin (TG), and a pro-atherogenic stimulus palmitate (PA), were used to co-expose HUVECs to further mimic the responses of diseased endothelial cells to micelle exposure. Overall, up to 200 μg/mL micelles did not significantly induce cytotoxicity, reactive oxygen species (ROS), release of inflammatory mediators in terms of interleukin 6 (IL-6), IL-8 and soluble vascular cell adhesion molecule 1 (sVCAM-1), or adhesion of THP-1 monocytes to HUVECs. TG and PA significantly induced cytotoxicity and THP-1 adhesion as well as modestly promoted the release of IL-6, but did not affect ROS or release of sVCAM-1 and IL-8. Co-exposure of micelles did not significantly enhance the effects of TG and PA to HUVECs, and ANOVA analysis indicated no interaction between concentrations of micelles and the presence of TG/PA. Taken together, these data indicated that micelles are not toxic to HUVECs under different conditions in vitro.

Water-Soluble Poly(ε-caprolactone)-Paclitaxel Prodrugs Toward an Efficient Drug Delivery System

In this paper, poly(ϵ-caprolactone)-graft-carboxylic acid (P(α-C2CL)) was prepared via a thio-bromo click reaction between mercaptosuccinic acid and poly(α-bromo-ϵ-caprolactone). It is readily soluble in aqueous solutions (pH 5.5–9.8) due to the presence of carboxylic groups in each repeating unit. A series of water-soluble P(α-C2CL)-paclitaxel prodrugs with high drug contents (up to 41.4 wt-%) was prepared by esterification. Meanwhile, methyl tetrazolium (MTT) assays showed that P(α-C2CL)-paclitaxel prodrugs exhibited a high antitumour effect on A549 and MCF-7 cells. These prodrugs have appeared as a highly versatile and potent platform for cancer therapy.