Structure Property Relationship of Novel in-Situ Prepared Thermoplastic Polyurethane/Hydroxyapatite Nanocomposites with Improved Antithrombotic Property for Biomedical Applications

The paper reports the preparation of two types of 2D rod-like nano-hydroxyapatite (nHA) (unmodified and modified) of varying high-aspect ratios, by modified co-precipitation method, without any templates. These both nHA were successfully introduced into novel synthesized Thermoplastic Polyurethane (TPU) matrices based on polycarbonate soft segments, by in-situ techniques. These nanocomposites were characterized and tested by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy, Wide Angle X-Ray Diffraction (WAXD), High Resolution Transmission Electron Microscopy (HRTEM), mechanical and and thermogravimetry analysis. Physico-mechanical properties of the in-situ prepared TPU/nHA nanocomposites were found to be superior compared to the pristine TPU. Thermal stability of the nanocomposites was improved tremendously. The polymer-filler interaction was reflected in the improved mechanical and thermal properties which were the consequences of proper dispersion of the filler in the polymer matrix. Improved biocompatibility of the prepared nanocomposites was confirmed by MTT assays using osteoblast-like MG63 cells. Prothrombin time (PT) and activated partial thromboplastin time (APTT), as calculated from coagulation assays, displayed an increase in the clotting time, particularly for the PPG wrapped (modified nHA) nanocomposites, prepared through the in-situ technique. Only 0.3% of hemolysis was observed for the in-situ prepared nanocomposites, which establishes the antithrombotic property of the material. The key parameters for enhancing the technical properties and biocompatibility of the nanocomposites are: the interfacial adhesion parameter (B_σy), the polymer-filler affinity, the aspect ratio of filler and non-covalent modifications, and the state of dispersion. Thus, the novel TPU/nHA nanocomposites have great potential for biomedical applications, in particular for vascular prostheses, cardiovascular implants, scaffolds, and soft and hard tissues implants. 

Keywords: nanohydroxyapatite; thermoplastic polyurethane; polycarbonate diol; MTT assays