The Institute of Textile Technology at RWTH Aachen University (ITA) is developing PLA fibers with microgels that can be degraded pH-neutrally. By using a bicomponent solvent spinning process, the distribution of the microgels in the fibre is to be controlled so that a fibre strength sufficient for further textile processing can be achieved.
The use of implants made of polyhydroxycarboxylic acids (PLA) is particularly important in medical applications; the avoidance of second operations for implant removal and the avoidance of long-term foreign body reactions are the focus of good, trouble-free medical care. The researchers Georg-Philipp Paar (Institute for Textile Technology at RWTH Aachen University), Catalina Molano and Andrij Pich (DWI-Leibniz Institute for Interactive Materials, Aachen), Renate Fourne (Fourne Maschinenbau GmbH), Thomas Gries (Institute for Textile Technology at RWTH Aachen University) and Stefan Jockenhvel (Institute for Textile Technology / AME-Helmholtz Institute for Biomedical Engineering) describe the development of these special PLA fibers for mechanical processing for the trade magazine “melliand Textilberichte”.
PLA fibers are established biodegradable polymers for surgical sutures, drug delivery systems and osteosynthesis systems. The problem is that conventional materials release the predominantly hydrolytic degradation of these polymers, which can lead to local acidosis. The drop in pH can lead to dramatic clinical consequences, such as massive inflammatory reactions or even complete tissue destruction. The low proton binding capacity of conventional additives has so far led to an unstable spinning process in material production and is ultimately the reason for intensive research. The final goal of the project at ITA is therefore the production of pH-neutral degrading PLA fibres whose strength is sufficient for further textile processing.
pH-value responsive microgels form the right approach
The approach for effective buffering of PLA fibres is the addition of microgels. Amine-based microgels are pH-responsive, colloidal polymer networks which, due to their high biocompatibility and high proton binding capacity, are much more suitable than conventional additives. However, the uncontrolled spatial distribution of the microgels in the fiber has so far unfortunately led to an unstable spinning process. In addition, the fibre strength of the fibres resulting from the process varies greatly.
By combining a strength-imparting component and a pH-value buffering component, fibers are now to be produced that are suitable for further textile processing and degrade pH-neutrally. In spinning tests, the technology (dry/wet/airgap spinning), the molecular weight of the PLA, the spinning solution, process parameters and the nozzle geometry are varied. Finally, the fiber properties are evaluated in tensile and degradation tests.
The EU-funded project is also investigating the synthesis of microgels and the production of nanoscale fibres in a bicomponent electrospinning process (DWI). In addition, the spatially defined introduction of microgels into non-fibrous PLA structures is being investigated. The focus is on the production of 3D-printed PLA structures, which also neutrally degrade the pH value.