Deposition of a polymer-based honeycomb-like membrane on 3D printed bioactive glass scaffold and decellularized bone matrix as scaffolds for bone tissue engineering
Résumé
INTRODUCTION
Materials used to regenerate bone tissue must present several essential properties i.e. biocompatibility,
osteoconductivity/osteoinductivity, while promoting angiogenesis1 . One major challenge often encountered
when using these materials (naturel or synthetic) is the invasion of the implantation site by fibrous tissue before
complete bone regeneration. The implant site invasion is due to the faster proliferation rate of the cells involved in
the wound healing process (e.g., fibroblasts) compared to membrane/substrate assembly. Furthermore, on the BaG
based scaffolds, Ca/P precipitation was evidenced by SEM (Figure 1). However, such finding was not visible
on the materials prepared from CB. ICP EOS analysis evidenced the important SiO2, Ca2+ and PO4 2- release
from BaG based scaffolds compared to bone. This explains that bone scaffolds do not precipitate an apatite
layer compared to BaG scaffolds. Indeed, BaGs degrade upon immersion, releasing biologically interesting ions,
resulting in apatite precipitation. bone cells proliferation rate2 leading to incomplete bone
regeneration3. To prevent this fibrous tissue invasion, barrier membranes have been used to cover the defects
and avoid this adverse effect. However, with the currently available products, membranes degrades faster
than the bone regeneration occurs which does not solve the problem of fibrous tissue ingrowth4. To overcome
this second challenge, researchers have turned their eyes on the bone regeneration itself, with the aim to make it
faster to close the gap between the membrane degradation and the bone regeneration rate. One strategy to accelerate bone regeneration is the use of bone graft in combination with the barrier membrane5. In such cases, the barrier membrane and the graft are two distinct
materials that are not in direct contact which requires a two-step procedure that can be challenging for surgeons.
In this study, combining bioactive glass (BaG) and/or cortical bone (CB) with a polymer-based honeycomb
membrane, a new type of biphasic scaffold is proposed to avoid the two-step procedure.
EXPERIMENTAL METHODS
The two phases affixed are 1) the organic phase formed of poly-L-co-D, L-lactic acid (PLDLA), known to be
biodegradable and biocompatible, shaped with a honeycomb-like structure through the Breath Figure
Method (BFM), and 2) an inorganic phase. The inorganic substrates used are a) the 13-93B20, an experimental
BaG composition containing boron, already reported in our previous work6 and b) a decellularized xenogenic CB
matrix provided by BIOBank©. The BaG used here has been specially designed and 3D printed to allow the
deposition of the membrane through the BFM. Our BaGs were used pre-immersed (conditioned) in TRIS buffer or
bare prior to membrane deposition.
RESULTS AND DISCUSSION
Our study demonstrated that PLDLA honeycomb-like membrane was successfully deposited onto CB and 3D
printed BaG scaffold through BFM. Materials were incubated in TRIS to study their degradation and
bioactivity. After 28 days of immersion in TRIS, no membrane detached from their substrate regardless of
their nature, exhibiting the strong link of the The next step of this study will focus on the
membrane/substrate assembly-cell interactions using osteogenic progenitor cells, MC3T3 and HGF to
elucidate the effect of such assembly on cells involved in bone regeneration processes.
Our hope is to prove a surface dependent cell proliferation and growth showing that osteogenic
progenitor cells develop mostly on the BaG/bone surfaces while fibroblastic cells grow better on the
PLDLA membrane. This would support the fact that having a biphasic material allowing a one-step procedure
and a separation of the underlying bone (or graft) from the outside (or fibrotic tissue) would be beneficial for a
proper bone regeneration and an easier procedure for surgeons.