Vaterite-based in situ surface modification and process-dependent biocompatibility of laser sintered polypropylene

Polypropylene (PP) rapidly gains scientific attention as fatigue-resistant and lightweight tissue repair and implant material, while emerging laser-sintering based methods for PP processing further allow unlimited versatility of PP specimens and often reduced numbers of process steps, substituting traditional manufacturing approaches. Generally, PP is considered biocompatible for a variety of medical applications while showing superior long-term stability, however, thermoplastic processing of polypropylene may induce the formation of cytotoxic degradation products, necessitating its cytotoxicological assessment. In the present study, PP specimens have been fabricated using warm, quasi-isothermal and complementary cold, non-isothermal powder bed fusion (PBF), allowing processing PP at ambient powder bed temperature of 25 °C for minimizing thermal exposure and the formation of decomposition products. The surface of manufactured specimens has been modified with hybrid coatings consisting of mesoporous inorganic microcrystals of vaterite laden with model biomacromolecules, i.e., fluorescently labelled dextran, demonstrating the stable coating and attachment of dextran-loaded vaterite crystals independent of the applied PBF processing regime. Vaterite coating is degradable and enables the opportunity to endow the surface of PP with sustained release functionalities. Both coated and uncoated specimens demonstrated excellent biocompatibility independent of the applied processing regime, as evaluated in an ex ovo shell-less hen’s egg model.