Functional polylactide by cationic ring-opening copolymerization of lactide with epoxides

Stereoregular poly(2-phenylthiirane) via cationic ring-opening polymerization

Herein, we describe an effective strategy for synthesizing polythioethers with a well-defined structure through the cationic polymerization of thiirane with electron-withdrawing substituents. This strategy allows for precisely controlling the regio- and stereochemistry of the ring-opening polymerization of 2-phenylthiirane, thus allowing for producing poly(2-phenylthiirane) with high stereoregularity using enantiomeric pure thiirane.

Synthesis and Characterization of Functionalized Polylactides Containing Acetal Units

New functionalized lactide copolymers containing acetal units were prepared for the first time in a controlled manner that enabled the regulation of the number of reactive groups introduced into the polyester chain. The presence of functional groups in the copolymer backbone provided chemical modification sites, and the nature of the acetal unit affected the material degradability. First, paraformaldehyde was reacted with selected diols containing reactive pendant groups (3-allyloxypropane-1,2-diol and 3-chloropropane-1,2-diol), which was catalyzed by p-toluenesulfonic acid, to synthesize new cyclic acetals with different functionalities (allyl- or chloro-). In addition, using butane-1,4-diol, a nonfunctionalized seven-membered cyclic acetal (dioxepane) was obtained for comparative studies. In the next step, the prepared cyclic acetals were used for cationic copolymerization with lactide in the presence of glycol as an initiator and triflic acid as a catalyst. Different temperatures (-15, 2, and 30 °C) and copolymerization times (24, 48, 72, and 192 h) were investigated to produce copolyesters with variable contents of acetal units in the range of 5-27%. The copolymers' structure and molar masses were carefully investigated using 1H, 13C NMR, 2D NMR, and size-exclusion chromatography. Moreover, the ability of functionalized copolymers to perform post modifications was also proven by the reaction with sodium azide and propanethiol. Finally, we speculate that structurally diverse groups can be attached to the copolyester chain, fine-tuning the on-demand properties, which could rapidly expand the library of polylactide-based materials.

pH-tunable nanoparticles composed of copolymers of lactide and allyl-glycidyl ether with various functionalities for the efficient delivery of anti-cancer drugs

The designing of biocompatible nanocarriers for the efficient delivery of their cargos to the desired targets remains a challenge. In this regard, the most promising strategy relies on the construction of pH- or thermo-responsive nanoparticles (NPs). However, it is also important to preserve the balance between the responsiveness of the carrier and their stability in physiological conditions. Therefore, we described a new family of copolymers of lactide and allyl-glycidyl ether which were subsequently modified by thiol-ene reaction to functionalize the resulting copolymer with acetylcysteine (ACC) or thioglycolic acid (tGA) moieties. Subsequently, these copolymers were used to obtain blank and doxorubicin (DOX) loaded NPs with an average diameter of about 50-100 nm. Interestingly, the NPs were stable in different pH conditions, however, the presence of ACC or tGA units in the polymeric chain allows for the reduction of the undesired burst release due to the supramolecular interactions between polymeric pedant groups and DOX. The release tests of DOX from NPs showed that DOX release rate decrease depending on the pH values and the copolymer functionalization in order of non-modified NPs > ACC-modified NPs > tGA functionalized NPs. Most importantly, the MTT assay showed that all blank NPs are non-toxic against the normal L929 cell line. Subsequently, the antitumor efficiency of the obtained NPs was tested towards L929 (murine fibroblast cell line), HeLa (cervical cancer), and AGS (human gastric adenocarcinoma cancer) cells. The results demonstrated that DOX-loaded NPs efficiently induce the reduction in the viability of the HeLa and AGS cell, and this reduction in the viability was even below 20 % for the AGS cells. Together with their biocompatibility, the obtained NPs offer a novel route for the preparation of nanocarriers for the controlled and efficient delivery of anticancer drugs.

Effect on electrospun fibres by synthesis of high branching polylactic acid

Polylactic electrospun porous fibres have been widely used in tissue engineering scaffolds. However, the application of linear polylactic is limited due to its poor hydrophilicity, which leads to phase separation and has been seldom used in porous fibre preparation. Instead, branching polylactic acts as a new effective method to prepare porous fibres because it can increase polylactic polar property and make it easy to be formulated in the following application. In the current study, we prepared an ultra-high molecular weight of high branching polylactic with glycerol as the initiator by controlling the ring-opening polymerization time, adding amount of catalyst and glycerol. The structure, molecular weight and thermal properties of copolymers were tested subsequently. The result showed that the surface of the high branching polylactic films is smooth, hydrophilic and porous. This branching polylactic formed electrospun porous fibres and possessed a strong adsorption of silver ion. Our study provided a simple and efficient way to synthesize branching polylactic polymer and prepare electrospun porous fibres, which may provide potential applications in the field of biomaterials for tissue engineering or antibacterial dressing compared with the application of linear polylactic and 3-arm polylactic materials.

Unconventional ionic ring-deconstruction pathways of a three-membered heterocycle

Two different ionic deconstruction reactions of the oxaphosphirane ring in I are reported. One is induced by base and involves displacement of the aldehyde unit forming II whilst acid-initiated extrusion of the ring-carbon with its substituents yielded III. Further insights into the latter ring-deconstruction were obtained by quantum chemical calculations.