Polymer Analyses for an Adapted Process Design of the Pipe-Extrusion of Polyetherimide

Over the last years, the use of high performance thermoplastic materials increased significantly especially in aviation applications. Thus, the processing of these high temperature polymers became more and more interesting. Especially, the groups of polymers like polyphenylene sulfide (PPS), polyether ether ketone (PEEK) or polyetherimide (PEI) are in the focus of recent developments and investigations. These materials show excellent thermal, mechanical and chemical properties while processing remains still challenging. Especially the influence of processing temperatures, temperature depending viscosities, the specific heat capacities and the thermal expansion show a high impact to the quality of the produced parts, e.g. degradation and dimensionally stability. Thus, this paper shows experimental characterizations in regard to the processing of PEI by pipe extrusion processes. In this context, a suitable methodology for the determination of appropriate process parameters is shown, which includes the comprehensive determination of temperature dependent thermal, thermomechanical and degradation properties of specific PEI extrusion materials.

Co-delivery of rhBMP-2 and zoledronic acid using calcium sulfate/hydroxyapatite carrier as a bioactive bone substitute to enhance and accelerate spinal fusion

Recombinant human bone morphogenetic protein-2(rhBMP-2)has been FDA-approved for lumbar fusion,but supraphysiologic initial burst release due to suboptimal carrier and late excess bone resorption caused by osteoclast activation have limited its clinical usage.One strategy to mitigate the pro-osteoclast side effect of rhBMP-2 is to give systemic bisphosphonates,but it presents challenges with systemic side effects and low local bioavailability.The aim of this in vivo study was to analyze if posterolateral spinal fusion(PLF)could be improved by utilizing a calcium sulfate/hydroxyapatite(CaS/HA)carrier co-delivering rhBMP-2 and zoledronic acid(ZA).Six groups were allocated(CaS/HA,CaS/HA+BMP-2,CaS/HA+systemic ZA,CaS/HA+local ZA,CaS/HA+BMP-2+systemic ZA,and CaS/HA+BMP-2+local ZA).10-week-old male Wistar rats,were randomly assigned to undergo L4-L5 PLF with implantation of group-dependent scaffolds.At 3 and 6 weeks,the animals were euthanized for radiography,μCT,histological staining,or biomechanical testing to evaluate spinal fusion.The results demonstrated that the CaS/HA biomaterial alone or in combination with local or systemic ZA didn’t support PLF.However,the delivery of rhBMP-2 significantly promoted PLF.Combining systemic ZA with rhBMP-2 didn’t enhance spinal fusion.Notably,the co-delivery of rhBMP-2 and ZA using the CaS/HA carrier significantly enhanced and accelerated PLF,without inhibiting systemic bone turnover,and potentially reduced the dose of rhBMP-2.Together,the treatment regimen of CaS/HA biomaterial co-delivering rhBMP-2 and ZA could potentially be a safe and cost-effective off-the-shelf bioactive bone substitute to enhance spinal fusion.