Biomedical subjects

J R Roosma

Publications and source records attributed to J R Roosma.

3 recordsLinked to original sources

PubMed2005

Controlled release of proteins from degradable poly(ether-ester) multiblock copolymers.

A new series of multiblock poly(ether-ester)s based on poly(ethylene glycol) (PEG), butylene terephthalate (BT) and butylene succinate (BS) segments were introduced as matrices for controlled release applications. The release of two model proteins, lysozyme and bovine serum albumin (BSA), from poly(ether-ester) films were evaluated and correlated to the swelling and degradation characteristics of the polymer matrices. First- and zero-order profiles were found for the release of lysozyme, depending on the composition of the polymer matrix. The initial diffusion coefficient was correlated to the swelling of the matrix, which increased with longer PEG segments and lower BT/BS ratios of the polymer. High swelling matrices released the lysozyme according to diffusion-controlled first-order release profiles. Zero-order release profiles were obtained from less swollen matrices due to a combination of diffusion and degradation of the matrix. In contrast to the release of lysozyme, BSA was released from the poly(ether-ester) matrices via delayed release profiles. Both the delay time and the release rate could be tailored by varying the matrix composition. The BSA release rate was mainly determined by the degradation, whereas the delay time was determined by a combination of the swelling and the degradation rate of the polymer matrix.

Diffusion↗

PubMed2004

Biodegradable poly(ether-ester) multiblock copolymers for controlled release applications: An in vivo evaluation.

Multiblock poly(ether-ester)s based on poly(ethylene glycol), butylene terephthalate, and butylene succinate segments were evaluated for their in vivo degradation and biocompatibility in order to establish a correlation with previously reported in vitro results. Porous polymer sheets were implanted subcutaneously for 32 weeks in rats. The degradation was monitored visually (histology), by molecular weight (GPC), and by copolymer composition (NMR). Substitution of the aromatic terephthalate units by aliphatic succinate units was shown to accelerate the degradation rate of the copolymers. Direct correlation of the in vivo and in vitro degradation of the porous implants showed a slightly faster initial molecular weight decrease in vivo. Besides hydrolysis, oxidation occurs in vivo due to the presence of radicals produced by inflammatory cells. In addition, the higher molecular weight plateau of the residue found in vivo indicated a higher solubility of the oligomers in the extracellular fluid compared to a phosphate buffer. Minor changes in the poly(ether-ester) compositions were noted due to degradation. Microscopically, fragmentation of the porous implants was observed in time. At later stages of degradation, macrophages were observed phagocytozing small polymer particles. Both in vitro cytotoxicity studies and histology on in vivo samples proved the biocompatibility of the poly(ether-ester)s.

Animals↗

PubMed2003

Biodegradable poly(ether-ester) multiblock copolymers for controlled release applications.

Multiblock poly(ether-ester)s based on poly(ethylene glycol), butylene terephthalate, and butylene succinate units were synthesized by a two-step melt polycondensation reaction, with the aim of developing a new series of degradable polymers for controlled release applications. The copolymers were characterized with respect to their composition (NMR), thermal properties (DSC), and swelling. The main focus was on the degradation kinetics and release properties of the copolymers. The crystallinity and swelling could be tailored by the PEG segment length and the ratio of the building units. With increasing mol fraction succinate in the hard segment, the swelling increased. The in vitro degradation was found to occur by molecular weight decrease and mass loss. Substitution of the aromatic terephthalate units by aliphatic succinate units increased the degradation rate of the copolymers. Polymers with PEG segments of 1000 kg/mol showed a more pronounced degradation than copolymers containing shorter and longer PEG segments. Model proteins were successfully incorporated and released from the poly(ether-ester) films. Depending on the size of the protein, the release mechanism was based on diffusion of the protein and degradation of the matrix.

Animals↗