Development of Porous Polyurethane Implants Manufactured via Hot-Melt Extrusion
Implantable drug delivery systems (IDDSs) offer good patient compliance and allow the controlled delivery of drugs over prolonged times. However, their application is limited due to the scarce material selection and the limited technological possibilities to achieve extended drug release. Porous structures are an alternative strategy that can overcome these shortcomings.
The present work focuses on the development of porous IDDS based on hydrophilic (HPL) and hydrophobic (HPB) polyurethanes and chemical pore formers (PFs) manufactured by hot-melt extrusion. Different PF types and concentrations were investigated to gain a sound understanding in terms of extrudate density, porosity, compressive behavior, pore morphology and liquid uptake. Based on the rheological analyses, a stable extrusion process guaranteed porosities of up to 40% using NaHCO3 as PF. The average pore diameter was between 140 and 600 µm and was indirectly proportional to the concentration of PF.
The liquid uptake of HPB was determined by the open pores, while for HPL both open and closed pores influenced the uptake. In summary, through the rational selection of the polymer type, the PF type and concentration, porous carrier systems can be produced continuously via extrusion, whose properties can be adapted to the respective application site.
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Article Information: Koutsamanis, I.; Spoerk, M.; Arbeiter, F.; Eder, S.; Roblegg, E. Development of Porous Polyurethane Implants Manufactured via Hot-Melt Extrusion. Polymers 2020, 12, 2950.
Materials: The hydrophilic TPU Pathway® PT83AE100 (HPL, shore hardness = 83 A, nominal water uptake = 100 wt%) and the hydrophobic TPU Pathway® PT72AE (HPB, shore hardness = 72 A) were kindly provided by Lubrizol LifeSciences, Wickliffe, OH, USA. Ammonium bicarbonate (NH4HCO3) and sodium bicarbonate (NaHCO3), supplied by Sigma Aldrich, Vienna, Austria, were used as pore formers (PFs). Sodium hydroxide, potassium dihydrogen phosphate (all by Sigma Aldrich, Vienna, Austria) and water purified by TKA MicroPure UV (JWT GmbH, Jena, Germany) were used to prepare the aqueous media.