Biomedical subjects

Harri Korhonen

Publications and source records attributed to Harri Korhonen.

3 recordsLinked to original sources

PubMed2006

Synthesis and hydrolysis behaviour of poly(ester anhydrides) from polylactone precursors containing alkenyl moieties.

Hydroxyl-group functional polylactones were prepared and converted to acid- terminated polyesters in a reaction with a series of alkenylsuccinic anhydrides containing 8, 12, or 18 carbons in their alkenyl chains. These polyester precursors were then linked into higher molecular weight poly(ester anhydrides) containing alkenyl moieties in their polyester blocks. The hydrolysis behaviour of the poly(ester anhydrides) was found to depend on the thermal properties of the polyester precursors. For poly(ester anhydrides) prepared from low molecular weight prepolymers with thermal transitions below 37 degrees C, the presence of hydrophobic alkenyl chains in the polyester precursors slowed the rate of weight loss. Poly(ester anhydrides) prepared from higher molecular weight prepolymers showed the opposite weight-loss behaviour; i.e., the crystallinity and thermal transitions of the alkenyl chain-containing poly(ester anhydrides) were low, and the weight loss was faster than for poly(ester anhydrides) without the alkenyl chains. The differences in length of the alkenyl chain, as such, had little effect on the hydrolysis behaviour and thermal properties of the poly(ester anhydrides).

Absorption↗

PubMed2005

Hand-held turbine spirometer: agreement with the conventional spirometer at baseline and after exercise.

Portable hand-held spirometers are widely used in outpatient clinics and in field surveys when examining children for asthma. However, the validity of the results obtained from the hand-held spirometers has not been assessed in population-based studies. We evaluated the agreement between the forced expiratory volume (FEV1) values got by the conventional flow volume spirometer (FVS) and the pocket-sized turbine spirometer (TS) at baseline and after exercise, among the 212 children screened for asthma and asthma-like symptoms from a population of 1633 school-aged children. The comparison was made between and within three diagnostic groups: clinical asthma (n = 34), possible asthma (n = 31), and controls (n = 147). In general, the differences in FEV1 between the FVS and the TS were small. For all children, the mean difference in FEV1 and the limits of agreement (difference +/-2 s.d.) was 0.05 l (0.23 to -0.13) at baseline and 0.06 l (0.24 to -0.12) after exercise. No significant differences were observed in the agreement between the diagnostic groups. In conclusion, although FEV1 results obtained by the hand-held spirometer are not interchangeable with those by the conventional spirometer, they are in reasonable agreement. The agreement is similar both at baseline and after exercise, and is not influenced by the presence of asthma.

Asthma↗

PubMed2004

Degradable polyesters through chain linking for packaging and biomedical applications.

The major route to convert lactic acid to high-molecular-weight polymers is ring-opening polymerization of lactide. We have investigated alternative synthesis routes based on oligomerization and chain linking to produce high-molecular-weight thermoplastic degradable polymers cost-effectively. Chain linking also offers new possibilities to prepare degradable polyesters for biomedical applications by extending the range of polymer properties achievable. In this paper, we briefly review different chain linking techniques used in our laboratory. Typically, lactic acid prepolymers with molecular weights of around 3,000-15,000 g x mol(-1) have been prepared by direct polycondensation. Hydroxyl terminated oligomers have been chain linked by using diisocyanate coupling agents, preferably 1,4-butane diisocyanate, forming poly(ester-urethanes). Poly(ester-amides) have been prepared by using 2,2'-bis(2-oxazoline) as coupling agent for carboxylic acid telechelic oligomers. Chain linking by end functionalization has been used in the preparation of poly(ester-anhydrides). In addition, a variety of crosslinked degradable polymers and copolymers have been synthesized through different crosslinking routes, by using methacrylic, itaconic or maleic double bonds or triethoxysilane moieties. A biodegradation test and ecotoxicological evaluation of the degradation products were carried out in addition to hydrolysis tests. Lactic acid based chain linked polymers were biodegradable and the degradation products were harmless. In hydrolysis tests, enzymatic degradation was pronounced in the chain linked poly(epsilon-caprolactone).

Biocompatible Materials↗