Mechanical Properties and In Vitro Evaluation of Thermoplastic Polyurethane and Polylactic Acid Blend for Fabrication of 3D Filaments for Tracheal Tissue Engineering

Abstract

Surgical reconstruction of extensive tracheal lesions is challenging. It requires a mechanically stable, biocompatible, and nontoxic material that gradually degrades. One of the possible solutions for overcoming the limitations of tracheal transplantation is a three-dimensional (3D) printed tracheal scaffold made of polymers. Polymer blending is one of the methods used to produce material for a trachea scaffold with tailored characteristics. The purpose of this study is to evaluate the mechanical and in vitro properties of a thermoplastic polyurethane (TPU) and polylactic acid (PLA) blend as a potential material for 3D printed tracheal scaffolds. Both materials were melt-blended using a single screw extruder. The morphologies (as well as the mechanical and thermal characteristics) were determined via scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, tensile test, and Differential Scanning calorimetry (DSC). The samples were also evaluated for their water absorption, in vitro biodegradability, and biocompatibility. It is demonstrated that, despite being not miscible, TPU and PLA are biocompatible, and their promising properties are suitable for future applications in tracheal tissue engineering.

Keywords: 3D filament; polylactic acid; thermoplastic polyurethane; trachea scaffold.

Figure 1

FTIR spectra of TPU, PLA, and TPU/PLA blends.

Figure 2

Cross-section SEM images of reactively extruded films: (a) 100/0, (b) 0/100. Homogeneous matrices are present in pure TPU and pure PLA (c) 90/10, (d) 80/20, (e) 70/30, (f) 60/40. Some fibrous TPU is present in the polymer blends, with PLA domains are dispersed in TPU matrices in all blends. Red arrows show PLA particles in the TPU matrix, while blue arrows indicate the fibrous TPU of the fractured surface. Scale bar of 100 μm.

Figure 3

DSC secondary melting curves of pure TPU and PLA, and TPU/PLA blends. The blue arrows show the first and second T_g values of pure TPU, while red arrows indicate both T_m values of pure TPU. Grey arrows show the T_g and T_m values of pure PLA. Finally, the green arrows depict all three T_g values of TPU/PLA blends.

Figure 4

Mechanical properties of TPU/PLA blends showing (a) tensile strength and Young’s modulus in MPA, and (b) percentage of elongation at break.

Figure 5

Schematic diagram of hydrogen bonding between the molecules of PLA and TPU. Reproduced with permission from Feng and Ye, Journal of Applied Polymer Science; reprinted with permission from ref [69], Copyright 2011 John Wiley and Sons.

Figure 6

(a) Water absorption rate of TPU, PLA, and the blends, (b) In vitro degradation study of the samples. Pure TPU shows the fastest degradation rate, while the slowest is that of pure PLA.

Figure 7

Presto Blue viability assay towards BEAS-2B cells.