Biomedical subjects

Helmut Münstedt

Publications and source records attributed to Helmut Münstedt.

3 recordsLinked to original sources

PubMed2005

Polyamide/silver antimicrobials: effect of filler types on the silver ion release.

The efficiency of various silver-based antimicrobial fillers (elementary silver and silver substituted materials) in polyamide (PA) toward their silver ion (Ag+) release characteristics in an aqueous medium was investigated and discussed. Anode stripping voltammetry (ASV) was used for the quantitative estimation of Ag+ release from these composites. The biocidal (Ag+) release from the composites was found to be dependent on the time of soaking in water and the nature of the filler. The long-term Ag+ release capability of the elementary silver-based PA/Ag composite is promising compared with the commercial counterparts. The silver ion release potential of polyamide composites where the silver filling was performed by using supercritical carbon dioxide (scCO2) is also discussed. The composites release Ag+ at a concentration level capable of rendering antimicrobial efficacy and proved to be active against the microbes. A good agreement exists between the Ag+ release experiments and antimicrobial test results. The observed results on the influence of the nature of the filler and crystallinity on the biocidal release and the varying long-term release properties could be helpful in the design of industrially relevant biomaterials.

Animals↗

PubMed2005

Silver ion release from antimicrobial polyamide/silver composites.

Silver ion (Ag(+)) the versatile antimicrobial species was released in a steady and prolonged manner from a silver-filled polyamide composite system. Metallic silver powder having varying specific surface area (SSA) has been used as a resource of biocide in polyamide. Strong evidences are found showing the release of the antimicrobial species from the resulting composite upon soaking it in water due to the interaction of the diffused water molecules with the dispersed silver powder within the matrix. The Ag(+) release was observed as increasing with time and concentration of the silver powder and is found to be influenced by the SSA of the silver powder, changes in the physical state of the composite specimen as a result of the water diffusion and the composite morphology. It is observed that the Ag(+) release increases initially which is followed by a marginal increase between day 4 and 6. Composites containing higher amounts of silver (4 and 8 wt%) exhibit a further rise in Ag(+) release from the sixth day of storage in water. Composite containing silver particles with the lowest specific surface area (0.78 m(2)/g) showed highest Ag(+) release. SEM shows a finer dispersion of the silver powder (4 wt%) having lowest SSA. However particles with higher (1.16 and 2.5 m(2)/g) SSA possess an agglomerated morphology leading to lower Ag(+) release. The composites are found to release Ag(+) at a concentration level capable of rendering an antimicrobial efficacy.

Anti-Bacterial Agents↗

PubMed2004

Determination of low amounts of long-chain branches in polypropylene using a combination of chromatographic and rheological methods.

The focus of our investigations lies on the detection of low amounts of long-chain branching (LCB) in isotactic polypropylene (iPP) created by electron beam irradiation. The modified samples were investigated by rheological experiments in shear and elongational flow and by size-exclusion chromatography. The comparison of the results demonstrates the efficiency and the detection limits of these methods, particularly at very low degrees of long-chain branching. The combination of chromatographic and rheological methods enables a sensitive and comprehensive way for the characterisation of the long-chain branching phenomena.

Chromatography, Gel↗