Influence of infill patterns on the mechanical and antibacterial properties of 3D-printed polylactic acid reinforced with hydroxyapatite/magnesium oxide bone repair scaffolds

Abstract

Herein, the mechanical and antibacterial properties of 3D printed polylactic acid (PLA) reinforced scaffolds incorporating hydroxyapatite (HA) and magnesium oxide (MgO) nanoparticles utilising various infill patterns (line, triangle, and cubic) were investigated. Scanning electron micrographs (SEM) demonstrated a uniform distribution of HA and MgO within the PLA, whereas X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) patterns confirmed the presence of the nanoparticles synthesised without compromising the crystallinity of the composite. The line pattern exhibited superior performance in surface hydrophilic properties, facilitating the interaction of bacteria with MgO nanoparticles. Mechanical tests indicated that the triangular pattern produced superior tensile, compressive, and flexural strength owing to its optimal load distribution and structural stability. Conversely, in vitro tests, including but not limited to inhibition zone measurements and live/dead cell imaging, the cubic pattern exhibited the most effective antibacterial activity, particularly against S. aureus bacteria. The cubic pattern, characterised by its increased surface area and improved wettability, facilitates bacterial interaction with MgO, which produces reactive oxygen species (ROS) that compromise cell membranes, ultimately leading to bacterial death. This study assessed the mechanical strength of the optimised components, determining that the triangular pattern was most suitable for load bearing implant applications, while the cubic pattern was effective for bacterial eradication.