The cellular responses of human macrophages seeded on 3D printed thermoplastic polyurethane scaffold

Tissue engineering is an interdisciplinary field for the design of functional constructs that aid to repair damaged or diseased tissue. Three-dimensional (3D) printing is a growing technology that offers new opportunities for tissue engineering. Thermoplastic polyurethane (TPU) is a member of the polyurethane class. TPUs are commonly used in medical applications with their biocompatible, superior mechanical properties and shape memory behavior. Macrophages are key regulators of tissue homeostasis, inflammation, and regeneration. They play crucial roles in initial immune response to implants. In this study, we aimed to investigate the viability, adhesion, and distribution properties of human THP-1 macrophages seeded on 3D printed TPU scaffolds in vitro. The expression of CD68 and CD10 was also analyzed in human THP-1 macrophages on 3D TPU scaffolds. THP-1 macrophages treated with phorbol-12-myristate-13-acetate (PMA) were seeded on 3D TPU scaffolds or tissue culture plastic plates as control and cultured for 1, 3, 7, and 14 days. 3D TPU scaffolds were prepared using a custom made fused deposition modeling printer. The cell viability was measured by WST-1 assay on days 1 and 3. The cell adhesion was evaluated by scanning electron microscopy (SEM). The cell distribution was analyzed by hematoxylin and eosin (H&E) staining. Expression of CD10 and CD68 was analyzed by immunohistochemical (IHC) staining. The viability of THP-1 macrophages on 3D TPU scaffolds was lower than their control groups on days 1 and 3. SEM images showed THP-1 macrophage attachment on the 3D TPU scaffold surface with round and elongated morphologies. H&E staining demonstrated that THP-1 macrophages showed eosinophilic cytoplasm and large nuclei. CD68 staining was more intense in THP-1 macrophages on 3D TPU scaffolds on day 3 compared to days 1, 7 and 14. CD10 staining was more intense on day 1 compared to days 3, 7, and 14. Our results show that 3D TPU scaffolds are biocompatible with macrophages and might be a potential biomaterial for medical applications.