Maciej Bero

Stereoselective polymerization of racemic DL-lactide in the presence of butyllithium and butylmagnesium. Structural investigations of the polymers

Abstract The use of butyllithium and butylmagnesium in the polymerization of racemic lactide leads to the formation of polylactide with a partially disyndiotactic structure. A coefficient of stereoselectivity p2 which describes the content of disyndiotactic structures appears to be higher for the lithium initiator; however an increase in the concentration of this initiator tends to enhance an intermolecular transesterification process thus leading to the formation of totally random structures in a polylactide chain. In contrast, in the case of butylmagnesium, an increase in the initiator concentration does not induce the intermolecular transesterification processes.

The application of microspheres from the copolymers of lactide and ϵ-caprolactone to the controlled release of steroids

Abstract The microspheres made of the copolymers of lactide and ϵ-caprolactone were used for the controlled release of progesterone and β-estradiol. The copolymers contained 83–94% of l or d,l -lactide. The influence of the microstructure of lactidyl blocks in the copolymer chains on the drug release rate was studied. More uniform release rate was observed in the case of the copolymer derived from d,l -lactide as composed to l -lactide. For the copolymer containing 83–94% of d,l -lactide units the progesterone and β-estradiol release rate in vitro was found to be practically constant within over 40 days. The in vivo studies performed on rats revealed that the period of constant release rate of β-estradiol can be prolonged to about 70 days. The microspheres made of the applied poly-( d,l -lactide-co-ϵ-caprolactone) are the convenient system for long time release of steroids.

Copolymerization of glycolide andε-caprolactone, 2. Random copolymerization in the presence of tin octoate

The copolymerization of glycolide with e-caprolactone was performed in the presence of tin octoate at moderate temperatures (100 and 150°C). The influence of the conditions (comonomer ratio, temperature) on the chain microstructure of the obtained copolymers was examined. Transesterification was found to affect considerably the course of the process. The effect of copolymer composition and chain microstructure on thermal properties was also investigated. A phase separation of glycolidyl and caproyl microblocks was observed. The heat of melting of the crystalline phases was found to be dependent on the length of glycolidyl and caproyl microblocks.

Synthesis of block copolymers of ε-caprolactone and lactide in the presence of lithium t-butoxide

SummaryHigh molecular mass copolymers with microphase separation can be obtained in block copolymerization of ε-caprolactone with L,L- and D,L-lactide carried out in the presence of lithium t-butoxide. A kind of solvent applied strongly affects the molecular mass and polydispersity index of obtained copolymers.

Controlled Release of 17β-Estradiol from d,l-Lactide/ε-Caprolactone Copolymers

A study of the release of β-estradiol from d,l-lactide/ε-caprolactone copolymers was performed. The copolymers were used in the form of films (in vitro) and microspheres (in vivo). The dl-lactide content was varied from 50 to 94% in the copolymers studied. It was found that an almost constant rate of β-estradiol release for about 70 days can be achieved by the application of appropriately selected material.

Effect of gamma-irradiation on cladribine and cladribine-containing biodegradable copolymers.

The aims of this study were to assess the effects of sterilization with gamma-irradiation on (i). bulk cladribine and (ii). cladribine-containing biodegradable copolymers. The stability of cladribine upon irradiation was confirmed by TLC, HPLC, UV, IR, DSC, rentgenography and electron microscopy. The stability of copolymers containing cladribine upon irradiation was assessed by IR, DSC and EPR. In vitro kinetics of nucleoside release from the copolymers before and after irradiation were compared, and only slight changes were found. Results of our study indicate that gamma-irradiation can be safely applied for the sterilization of cladribine or cladribine-containing copolymers for medical purposes.