Optimization of composition, structure and mechanical strength of bioactive 3-D glass-ceramic scaffolds for bone substitution

Abstract

Fabrication of 3-D highly porous, bioactive, and mechanically competent scaffolds represents a significant challenge of bone tissue engineering. In this work, Bioglass®-derived glass-ceramic scaffolds actually fulfilling this complex set of requirements were successfully produced through the sponge replication method. Scaffold processing parameters and sintering treatment were carefully designed in order to obtain final porous bodies with pore content (porosity above 70 %vol), trabecular architecture and mechanical properties (compressive strength up to 3 MPa) analogous to those of the cancellous bone. Influence of the Bioglass® particles size on the structural and mechanical features of the sintered scaffolds was considered and discussed. Relationship between porosity and mechanical strength was investigated and modeled. Three-dimensional architecture, porosity, mechanical strength and in vitro bioactivity of the optimized Bioglass®-derived scaffolds were also compared to those of CEL2-based glass-ceramic scaffolds (CEL2 is an experimental bioactive glass originally developed by the authors at Politecnico di Torino) fabricated by the same processing technique, in an attempt at understanding the role of different bioactive glass composition on the major features of scaffolds prepared by the same method.

Novel full-ceramic monoblock acetabular cup with a bioactive trabecular coating: design, fabrication and characterization

“…Sponges with flat surfaces (e.g. cubes [35,36] or strips [26,28]) can be effectively and uniformly compressed by means of an axial press; however, the situation is much more complex in the case of curved samples since, ideally, a compression along the radial direction should be performed. A simplified strategy was adopted in this work and the principle behind the action of the two hemi-shells is schematically depicted in Fig.…”

Trabecular coating on curved alumina substrates using a novel bioactive and strong glass-ceramic

“…The compressive strength of S50P3 scaffolds (around 19 MPa) is above the standard reference range usually considered for cancellous bone (2-12 MPa [1]) as well as most of foam-like scaffolds with a comparable pore content reported in the literature [31,32]. This can be attributable to the higher silica content and to the presence of a small amount of alumina as an intermediate oxide, which is known to have a strengthening effect on the glass network.…”

Electrophoretic deposition of mesoporous bioactive glass on glass–ceramic foam scaffolds for bone tissue engineering

“…The scaffolds compressive strength is above the standard reference range (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) ) considered for human trabecular bone as well as most of foam-like scaffolds with the same porosity reported in the literature [11]; therefore, the produced samples can be proposed even for load-bearing applications like in joint prostheses [13,14]. The fracture energy is from one to two orders of magnitude higher than that reported for other glass-ceramic scaffolds produced by the same method and having analogous macroporous architecture [44,45]; in this regard, a key role is played by the formulation of the starting glass (SCNA) in affecting the sintering behaviour of glass particles and the densification of the scaffold struts.…”

“…Chen et al [6] and Vitale-Brovarone et al [7] pioneered the use of the sponge replication method to fabricate porous (70-90 vol.%) bioactive scaffolds able to allow tissue and blood vessels in-growth; however, these scaffolds were too brittle (compressive strength within 0.3-0.4 MPa [6], 1 MPa [7] ) to deem any real surgical application. The combination of PE particles and a polymeric sponge as pore formers [8] as well as various optimization strategies [9] were also reported in the attempt at improving the mechanical performance of Bioglass Ò scaffolds, but problems of brittleness still remained. This was one of the major reasons why other bioactive glass formulations were developed in recent years in the hope that a truly strong, bioactive glass scaffold can be eventually produced.…”