Showing papers by "Ann-Christine Albertsson published in 2008"
TL;DR: E enzyme-catalyzed ring-opening polymerization of lactones, lactides, cyclic carbonates and depsipeptides has been reviewed with special focus on the molecular weight of the polymers synthesized hitherto using enzyme catalysis.
198 citations
TL;DR: The chemical strategy presented herein is the nondestructive preparation of resorbable polymer scaffolds with heparin covalently bonded to the surface and an osteoinductive growth factor, recombinant human bone morphogenetic protein-2, immobilized in the heparIn layer.
74 citations
TL;DR: The hydrolytic degradation process and degradation product patterns of biodegradable homo- and copolyesters of 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL) were monitored by electrospray.
Abstract: The hydrolytic degradation process and degradation product patterns of biodegradable homo- and copolyesters of 1,5-dioxepan-2-one (DXO) and epsilon-caprolactone (CL) were monitored by electrospray ...
59 citations
TL;DR: In this paper, hydrogel microspheres were loaded with either a small hydrophilic substance (caffeine) or a macromolecular model protein (bovine serum albumin) and afforded diffusion controlled release in vitro.
Abstract: Hydrogel microspheres were prepared from the major softwood hemicellulose polysaccharide acetylated galactoglucomannan. The dry and swollen morphology was assessed by scanning electron microscopy. The microspheres were loaded with either a small hydrophilic substance (caffeine) or a macromolecular model protein (bovine serum albumin) and afforded diffusion controlled release in vitro. Statistical multivariate analysis was used to systematically determine the influence and significance of the hydrogel composition, the crosslinking density, and the dimensions of the incorporated substance on the microsphere size and release rate.
54 citations
TL;DR: It was concluded that a catalyst:monomer ratio of 1:10,000 or lower is required to achieve a polymer with tin content suitable for biomedical applications and showed that cells could grow on all polymers with an efficiency equal to or better than that on normal tissue culture plastic.
Abstract: By using less catalyst in the ring-opening polymerization of epsilon-caprolactone, a residual tin content of 5 ppm was reached without the need for additional purification. The initial amount of ti ...
52 citations
TL;DR: Both the pendant group composition and the enzyme action are valuable tools in the tailoring of hydrogel release profiles of potential interest for intestine drug delivery.
49 citations
TL;DR: In this article, the authors summarized the work done on the chromatographic analysis of degradation products from the most common aliphatic polyesters under different abiotic and biotic conditions including simulated, accelerated and real environmental conditions.
Abstract: Analysis of degradation products needs to be included in degradability testing to ensure the environmental adaptability of degradable polymers. Identification of breakdown products from environmental degradation is important for understanding the degradation process, environmental interaction and impact of degradable polymers. With regard to degradability aliphatic polyesters are a particularly interesting group of polymers. They are susceptible to hydrolysis and biological attack due to the ester groups in the main chain. This paper summarizes the work done on the chromatographic analysis of degradation products from the most common aliphatic and aliphatic–aromatic polyesters under different abiotic and biotic conditions including simulated, accelerated and real environmental conditions.
47 citations
TL;DR: The results presented here show that, for both sterilization methods, the crystallinity increased for all copolymers of 1,5-dioxepan-2-one (DXO) and l,l-lactide (LLA) at the minimum sterilization dose.
42 citations
TL;DR: The initial hydrolysis rate of PLA monolayer in presence of proteinase K is determined by volumetric analysis from the continuous AFM height images and the erosion rate of branched PLLA monolayers was found to be dependent on the average molecular weight of PLLLA segment in brancher molecules, not on the overall molecularWeight of samples.
41 citations
TL;DR: It was evidenced that the architecture of the resulting porous materials has a high order degree, emerging from the self-assembling of the microgel particles, which provided numerous, nearly uniform, large water release channels.
37 citations
TL;DR: Fingerprinting of degradation product patterns by electrospray ionization mass spectrometry (ESI-MS) was evaluated as a tool to monitor the degree of degradation in polyester-ether networks.
Abstract: Fingerprinting of the degradation product patterns by electrospray ionization mass spectrometry (ESI-MS) was evaluated as a tool to monitor the degree of degradation in polyester-ether networks Fo
TL;DR: In this paper, star-shaped homo-and copolymers were synthesized in a controlled fashion using two different initiating systems, using E-caprolactone, L-lactide, and 1,5-dioxepan-2-one.
Abstract: Star-shaped homo- and copolymers were synthesized in a controlled fashion using two different initiating systems. Homopolymers of E-caprolactone, L-lactide, and 1,5-dioxepan-2-one were firstly poly ...
Journal Article•
TL;DR: In this article, star-shaped homo-and copolymers were synthesized in a controlled fashion using two different initiating systems, i.e., a spirocyclic tin initiator and stannous octoate (cocatalyst) together with pentaerythritol ethoxylate 15/4 EO/OH (coinitiator), to give polymers with identical core moieties.
Abstract: Star-shaped homo- and copolymers were synthesized in a controlled fashion using two different initiating systems. Homopolymers of e-caprolactone, L-lactide, and 1,5-dioxepan-2-one were firstly polymerized using (I) a spirocyclic tin initiator and (II) stannous octoate (cocatalyst) together with pentaerythritol ethoxylate 15/4 EO/OH (coinitiator), to give polymers with identical core moieties. Our gained understanding of the versatile and controllable initiator systems kinetics, the transesterification reactions occurring, and the role which the reaction conditions play on the material outcome, made it possible to tailor the copolymer microstructure. Two strategies were used to successfully synthesize copolymers of different microstructures with the two initiator systems, i.e., a more multiblock- or a block-structure. The correct choice of the monomer addition order enabled two distinct blocks to be created for the copolymers of poly(DXO-co-LLA) and poly(CL-co-LLA). In the case of poly(CL-co-DXO), multiblock copolymers were created using both systems whereas longer blocks were created with the spirocyclic tin initiator. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 1249-1264, 2008
TL;DR: A comparison between the fibrous materials and the homogeneous solvent-cast films revealed that the surface of the nanofibers was more hydrophobic and that the nan ofibers were degraded more rapidly in the presence of proteinase.
Abstract: Nanofibrous scaffolds of poly[(L-lactide)-co-(1,5-dioxepan-2-one)] generated by electrospinning have been compared with porous films obtained by solvent cast/salt leaching and homogeneous films. A comparison between the fibrous materials and the homogeneous solvent-cast films revealed that the surface of the nanofibers was more hydrophobic and that the nanofibers were degraded more rapidly in the presence of proteinase. It was obvious that the strain-to-break was reduced by the nanofiber formation, it decreased from 370% to 130% independent of fiber diameter. These values were however considerably higher than the strain-to-break of the solvent-cast/salt leaching scaffold. In addition, the nanofibrous material accelerated the adhesion and growth of the mesenchymal stem cell compared to the smooth material.
TL;DR: Resorbable porous scaffold discs and solid films were prepared from poly[ (1,5-dioxepan-2-one)-co-(L-lactide)] and poly[(epsilon-caprolactone-co-co)-co-L- lactide to increase their hydrophilicity and exhibited a tremendous increase in wettability.
Abstract: Resorbable porous scaffold discs and solid films were prepared from poly[(1,5-dioxepan-2one)-co-(L-lactide)] and poly [(epsilon-caprolactone)-co-(L-lactide)]. The surfaces of the scaffolds were ...
TL;DR: In this paper, the authors describe characterization by chromatographic techniques and sample preparation methods to identify and quantify antioxidants and their degradation products in polymeric materials, and the major difficulty in the characterization is usually not the analytical method but rather the separation of the antioxidants from the polymer matrix.
Abstract: The accurate and reliable measurement of antioxidant content in polymers by chromatographic techniques, e.g., liquid chromatography (LC) is an important tool in quality and manufacturing control, troubleshooting, and material or vendor identification. This chapter describes characterization by chromatographic techniques and sample preparation methods to identify and quantify antioxidants and their degradation products in polymeric materials. The major difficulty in the characterization is usually not the analytical method but rather the separation of the antioxidants from the polymer matrix. The separation can be performed by various extraction methods. Traditionally, Soxhlet or polymer dissolution methods are used. These methods have several disadvantages. Therefore, more complex and efficient methods with the possibility of working at elevated temperatures and pressures have been developed, i.e., microwave-assisted extraction (MAE), supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE), which are discussed here. These methods make it possible to study the relation between antioxidant efficiency and the release of degradation products from polymers. Another interesting aspect is the study of migration of antioxidants from plastic packaging into the surrounding media.
TL;DR: In this paper, the spontaneous reaction of unsaturated double bonds induced by the fragmentation of ether bonds is presented as a method to obtain a crosslinked polymer material and the formation of a network structure was confirmed by Fourier transform infrared spectrometry and differential scanning calorimetry.
Abstract: The spontaneous reaction of unsaturated double bonds induced by the fragmentation of ether bonds is presented as a method to obtain a crosslinked polymer material. Poly(1,5-dioxepan-2-one) (PDXO) was synthesized using three different polymerization techniques to investigate the influence of the synthesis conditions on the ether bond fragmentation. It was found that thermal fragmentation of the ether bonds in the polymer main chain occurred when the synthesis temperature was 140 °C or higher. The double bonds produced reacted spontaneously to form crosslinks between the polymer chains. The formation of a network structure was confirmed by Fourier transform infrared spectrometry and differential scanning calorimetry. In addition, the low molar mass species released during hydrolysis of the DXO polymers were monitored by ESI-MS and MALDI-TOF-MS. Ether bond fragmentation also occurred during the ionization in the electrospray instrument, but predominantly in the lower mass region. No fragmentation took place during MALDI ionization, but it was possible to detect water-soluble DXO oligomers with a molar mass up to approximately 5000 g/mol. The results show that ether bond fragmentation can be used to form a network structure of PDXO. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7258–7267, 2008
01 Jan 2008
TL;DR: Hakkarainen et al. as mentioned in this paper proposed a solid-phase microextraction for analysis of polymer degradation products and additives and showed that it can be used to measure the degradation state and lifetime of polymers.
Abstract: L. Burman, A.-C. Albertsson, M. Hakkarainen: Indicator Products and Chromatographic Fingerprinting: New Tools for Degradation State and Lifetime Estimation.- M. Hakkarainen: Solid-Phase Microextraction for Analysis of Polymer Degradation Products and Additives.- M. Groning, M. Hakkarainen, A.-C. Albertsson: Quantitative Determination of Volatiles in Polymers and Quality Control of Recycled Materials by Static Headspace Techniques.- M. Hakkarainen, A.-C. Albertsson: Degradation Products of Aliphatic and Aliphatic-Aromatic Polyesters.- C. Strandberg, A.C. Albertsson: Chromatographic Analysis of Antioxidants in Polymeric Materials and Their Migration from Plastics into Solution.- M. Hakkarainen: Migration of Monomeric and Polymeric PVC Plasticizers.-