  In order to increase the bone forming ability of MBG-PCL composite scaffold,
microporosity was created in the struts of 3D-printed MBG-PCL scaffolds for the
manufacturing of a construct with a multiscale porosity consisting of meso-,
micro- and macro-pores. 3D-printing imparted macroporosity while the
microporosity was created by porogen removal from the struts, and the MBG
particles were responsible for the mesoporosity. The scaffolds were 3D-printed
using a mixture of PCL, MBG and phosphate buffered saline (PBS) particles,
subsequently leached out. Microporous-PCL (pPCL) as a negative control,
microporous MBG-PCL (pMBG-PCL) and non-microporous-MBG-PCL (MBG-PCL) were
investigated. Scanning electron microscopy, mercury intrusion porosimetry and
micro-computed tomography demonstrated that the PBS removal resulted in the
formation of micropores inside the struts with porosity of around 30% for both
pPCL and pMBG-PCL, with both constructs displaying an overall porosity of
80-90%. In contrast, the MBG-PCL group had a microporosity of 6% and an overall
porosity of 70%. Early mineralisation was found in the pMBG-PCL post-leaching
out and this resulted in the formation a more homogeneous calcium phosphate
layer when using a biomimetic mineralisation assay. Mechanical properties
ranged from 5 to 25 MPa for microporous and non-microporous specimens, hence
microporosity was the determining factor affecting compressive properties.
MC3T3-E1 metabolic activity was increased in the pMBG-PCL along with an
increased production of RUNX2. Therefore, the microporosity within a 3D-printed
bioceramic composite construct may result in additional physical and biological
benefits.
