Abstract
The development of innovative materials for bone tissue engineering to promote bone regeneration while avoiding fibrous tissue infiltration is of paramount importance. Here, we combined the known osteopromotive properties of bioactive glasses (BaGs) with the biodegradability, biocompatibility, and ease to shape/handle of poly-l-co-d,l-lactic acid (PLDLA) into a single biphasic material. The aim of this work was to unravel the role of the surface chemistry and topography of BaG surfaces on the stability of a PLDLA honeycomb membrane, in dry and wet conditions. The PLDLA honeycomb membrane was deposited using the breath figure method (BFM) on the surface of untreated BaG discs (S53P4 and 13-93B20), silanized with 3-aminopropyltriethoxysilane (APTES) or conditioned (immersed for 24 h in TRIS buffer solution). The PLDLA membranes deposited onto the BaG discs, regardless of their composition or surface treatments, exhibited a honeycomb-like structure with pore diameter ranging from 1 to 5 μm. The presence of positively charged amine groups (APTES grafting) or the precipitation of a CaP layer (conditioned) significantly improved the membrane resistance to shear as well as its stability upon immersion in the TRIS buffer solution. The obtained results demonstrated that the careful control of the substrate surface chemistry enabled the deposition of a stable honeycomb membrane at their surface. This constitutes a first step toward the development of new biphasic materials enabling osteostimulation (BaG) while preventing migration of fibrous tissue inside the bone defect (honeycomb polymer membrane).
Highlights
It is commonly accepted that bone tissue regeneration requires innovative materials, with various properties, i.e., biocompatibility, osteoconductivity/osteoinductivity, while promoting angiogenesis.[1−3] In addition, newly developed biomaterials should have a structural organization mimicking the natural bone
In the case of silanization with APTES, the decrease in surface charge can be explained by the introduction of positively charged amine groups to the bioactive glasses (BaGs) disc surface at pH = 7.41 Upon conditioning for 24 h in TRIS buffer solution, the BaG discs started to dissolve which resulted in the formation of Si−OH and Si−O− groups on their surfaces
The surface charge decrease observed in our study may be explained by (1) the density of positively charged amine groups at the surface of silanized samples and (2) the nature of the Ca−P layer that has possibly deposited during the preincubation of the BaG discs for 24 h
Summary
It is commonly accepted that bone tissue regeneration requires innovative materials, with various properties, i.e., biocompatibility, osteoconductivity/osteoinductivity, while promoting angiogenesis.[1−3] In addition, newly developed biomaterials should have a structural organization mimicking the natural bone. This is due to the faster proliferation rate of cells involved in the wound healing process (e.g., fibroblasts) compared to that of the bone cells.[4] invasion of the bone defect by soft tissue will lead to incomplete bone regeneration.[5,6] To prevent this negative outcome, membranes have been used to cover the bone defect and prevent fibrous tissue ingrowth.[5,7] Many types of membranes have been developed, either made from synthetic polymers (either degradable, i.e., aliphatic acids such as poly-L-lactic acid (PLLA), poly-L-lactide-co-glycolide (PLGA) or not degradable such as polytetrafluorethylene (PTFE)) or natural polymers (collagen or chitosan, for example).[5,8] As of today, the majority of commercially available membranes are based on synthetic degradable polymers or collagen.[9] These membranes exhibit high biocompatibility, favor cell adhesion, and do not necessitate to be retrieved during a second surgery They have an unpredictable degradation rate, leading to a mismatch between the membrane degradation and the new bone formation rate.[9] There is still important work to be done to achieve the production of the ideal protective membrane, but there is a consensus on their required properties. The ideal barrier membrane should (1) be biocompatible, (2) be cellocclusive, (3) allow space-making (“define the volume of bone that can be regenerated”10), (4) allow tissue integration, (5) be easy to handle, and (6) have an appropriate pore size and pore interconnectivity to facilitate bone regeneration but preventing excessive fibrous tissue penetration.[5,10−12] While initially the membrane was only used to direct the bone regeneration (without the use of bone grafts), the review by Dimitriou et al.[5] reports the use of barrier membranes associated with a bone
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