A Review on Manufacturing Processes of Biocomposites Based on Poly(α-Esters) and Bioactive Glass Fillers for Bone Regeneration

Abstract

The incorporation of bioactive and biocompatible fillers improve the bone cell adhesion, proliferation and differentiation, thus facilitating new bone tissue formation upon implantation. During these last 20 years, those biocomposites have been explored for making complex geometry devices likes screws or 3D porous scaffolds for the repair of bone defects. This review provides an overview of the current development of manufacturing process with synthetic biodegradable poly(α-ester)s reinforced with bioactive fillers for bone tissue engineering applications. Firstly, the properties of poly(α-ester), bioactive fillers, as well as their composites will be defined. Then, the different works based on these biocomposites will be classified according to their manufacturing process. New processing techniques, particularly additive manufacturing processes, open up a new range of possibilities. These techniques have shown the possibility to customize bone implants for each patient and even create scaffolds with a complex structure similar to bone. At the end of this manuscript, a contextualization exercise will be performed to identify the main issues of process/resorbable biocomposites combination identified in the literature and especially for resorbable load-bearing applications.

Keywords: PLA; bioglass; manufacturing process; mechanical properties.

Figure 2

Bioactivity and bone enhancement steps of bioglass. Reproduced from [53].

Figure 1

Chemical structure of the different poly(α-hydroxy ester).

Figure 3

Bacterial viability and morphology of biofilms treated with MBG and Cu_MBG 2% suspensions. Both suspensions were added to S. epidermidis RP62A biofilm formation cultures (A) or after the formation of a stable staphylococcal biofilm (C). Bacterial viability is designed by *** and ** for (A) and (C) experiments respectively. SEM representative images of the staphylococcal biofilms formed in the absence (control) or in contact with both types of nanoparticles for 24 h are shown (B). SEM images of post formed biofilms, untreated (control) or treated with both MBG or Cu_MBG 2% nanoparticles for 24 h, are shown (D). Reproduced from [88].

Figure 4

Diagram of the different FGM strategies for bone tissue engineering.

Figure 5

SEM images showing pore formation for PLLA scaffold during solvent extraction at different temperatures. Reproduced from [120].

Figure 6

Compressive strength of the polymer P (light gray) and the composite C30 (dark gray) in function of immersion time in PBS. Reproduced from [59].

Figure 7

Schematic diagram of fabricating porous PCL composite scaffolds. Reproduced from [60].

Figure 8

Results from compression test of immersed samples in PBS (a) Average Young’s modulus, (b) Average yield stress. Reproduced from [146].

Figure 9

(A) Schematic diagram of robotic dispending method, (B) enlargement of the dispensing nozzle and deposited fiber mesh, and (C) three-dimensional PCL/BG composite scaffold. Reproduced from [147].

Figure 10

Young’s modulus (a), elongation at break (b) and tensile strength (c) of random and aligned fibers. Results are expressed as (mean ± standard deviation). Bars show statistically significant differences (p < 0.05). In the inset of (a,c) a zoom view of the properties of randomly oriented fibers is reported. Reproduced from [161].

Figure 11

(a) Schematic diagram of the MEW process using an applied pressure (ΔP) to extrude a molten polymer or polymer solution through a nozzle with a radius R and a length L to a moving collector plate. (b) Visualization of the MEW device. (c–e) SEM image of microfiber morphology. Reproduced from [165].

Figure 11

(a) Schematic diagram of the MEW process using an applied pressure (ΔP) to extrude a molten polymer or polymer solution through a nozzle with a radius R and a length L to a moving collector plate. (b) Visualization of the MEW device. (c–e) SEM image of microfiber morphology. Reproduced from [165].

Figure 12

(A) Healing of individual polymer particles to form partially sintered and fully sintered material as a function of time and temperature. (B) Illustration of the effect of increasing filler content on the sintering of composite materials. An increase of filler content difficult the polymer sintering. (C) Schematic of sintering of powder particles with different particle sizes. Regions directly under the laser path are fully sintered, and heat is transferred to surrounding particles through contact points to form partially sintered regions. Higher partial sintering and lower porosity occurs for small particle sizes. Reproduced from [168].

Figure 13

Micrographs with 200× of magnification. (a) pure polymer; (b) polymer with 10 wt% of BG; (c) polymer with 20 wt% of BG; (d) polymer with 30 wt% of BG. Reproduced from [167].

Figure 14

(a) SEM image of a BG scaffold, (b) optical stereomicroscope image of a PCL scaffold with 20 wt% of BG and (c,d) SEM images of a surface of a PCL/BG scaffold. Reproduced from [178].