Laser Sintering Approaches for Bone Tissue Engineering

Abstract

The adoption of additive manufacturing (AM) techniques into the medical space has revolutionised tissue engineering. Depending upon the tissue type, specific AM approaches are capable of closely matching the physical and biological tissue attributes, to guide tissue regeneration. For hard tissue such as bone, powder bed fusion (PBF) techniques have significant potential, as they are capable of fabricating materials that can match the mechanical requirements necessary to maintain bone functionality and support regeneration. This review focuses on the PBF techniques that utilize laser sintering for creating scaffolds for bone tissue engineering (BTE) applications. Optimal scaffold requirements are explained, ranging from material biocompatibility and bioactivity, to generating specific architectures to recapitulate the porosity, interconnectivity, and mechanical properties of native human bone. The main objective of the review is to outline the most common materials processed using PBF in the context of BTE; initially outlining the most common polymers, including polyamide, polycaprolactone, polyethylene, and polyetheretherketone. Subsequent sections investigate the use of metals and ceramics in similar systems for BTE applications. The last section explores how composite materials can be used. Within each material section, the benefits and shortcomings are outlined, including their mechanical and biological performance, as well as associated printing parameters. The framework provided can be applied to the development of new, novel materials or laser-based approaches to ultimately generate bone tissue analogues or for guiding bone regeneration.

An Overview on the Big Players in Bone Tissue Engineering: Biomaterials, Scaffolds and Cells

“…This method allows users to easily manage and adjust the structures of the scaffold by controlling various SLS parameters. However, a sig drawback of this technique is that it needs to operate at high temperatures; af there is a need for post-processing to remove extra powder [117,140]. Selective laser sintering processes utilize a carbon dioxide laser to meld together various powdered materials such as wax, polycarbonate, ceramics, and polymers like nylon, as well as their combinations and metals, to form the desired scaffold structure.…”

“…Table 3 summarizes the advantages and disadvantages that result from the application of various techniques used in the production of different types of scaffolds. Post-processing required, expensive [114,117] Stereolithography Good potential for designing different cellular machines Resins used may be cytotoxic [114,[118][119][120] Hydrogel-based scaffolds…”

A Preclinical Trial Protocol Using an Ovine Model to Assess Scaffold Implant Biomaterials for Repair of Critical-Sized Mandibular Defects

“…PEK and PEEK are nonresorbable polymers with excellent tensile strength, high modulus, chemical resistance, and thermal stability. Due to its nontoxicity and biocompatibility, PEEK has been used extensively as an implant in the facial skeleton and as dental implants and abutments. , One significant drawback of PEEK is bioinertness and hydrophobicity, which can be however overcome by surface treatment using Plasma Immersion Ion Implantation (PIII). Our previous work has demonstrated the osseointegration of a FDM printed PEEK implants is enhanced by PIII treatment. − Here, both PEEK and PEK were 3D printed as a porous construct using FDM and SLS techniques, respectively; and then treated using PIII.…”

“…Due to its nontoxicity and biocompatibility, PEEK has been used extensively as an implant in the facial skeleton and as dental implants and abutments. 24,25 One significant drawback of PEEK is bioinertness and hydrophobicity, which can be however overcome by surface treatment using Plasma Immersion Ion Implantation (PIII). Our previous work has demonstrated the osseointegration of a FDM printed PEEK implants is enhanced by PIII treatment.…”

Three-Dimensional Scaffolds for Bone Tissue Engineering

“…Summary of composite sintering approaches outlining the specific print parameters utilized, physical attributes and biological outcomes of the printed constructs. Where P = Laser Power, λ = Wavelength, S = Scan Spacing, T = Layer thickness, V = Scan Velocity, Φ = Beam Diameter, E = Elastic Modulus, σUC = Ultimate Compressive Strength[79]. C bed temp Increasing β-TCP content was found to decrease the strength[81] PLLA/GO@Si-HAP = 7 W λ = N/A S = N/A T = N/A V = 180 mm/sCompressive strength and modulus improved by 85% and 120% after incorporating GO@Si-HA, with a marginal improvement in hardness 4 wk SBF: PLLA minimal, PLLA/GO minimal, PLLA/GO@Si-HA significantly improved appetite formation and MG-63 cell morphology and ALP activity after 7 mm/s Φ = 800 µm BG was found to be slightly exposed on the surface of scaffolds following EDS analysis BG 58s addition improved osteoconductivity and osteoinductivity of scaffolds, following SBF and MG-63 cell seeding analysis[84] Aliphaticpolycarbonate/HA(aPC/ HA) a-PC a-PC/5 wt% HA a-PC/10 wt% HA a-PC/ 15 wt% HA P = 11 W λ = 10.6 µm S = 0.15 mm T =0.15 mm V = 2000 mm/s Φ = 200 µm 135 • C bed temp Surface roughness and porosity (53 to 82%) increased with HA content, below 15 wt% ideal 6-7 times reduction in scaffold strength with HA compared to pure a-PC Osteoconductivity unchanged by SLS processing [85] Poly [3,6-dimethyl-1,4dioxane-2,5-dione]/HA P = 10 W λ = 1.06 µm S = N/A T = N/A V = mm/s Φ = 125 µm Young's modulus increased from 6.4 to 8.4 GPa with HA addition Sintered composite scaffolds improved ATSC attachment and viability, compared to foaming method and virgin polymer [86] PVA/HA 90:10 vol% 10-75 µm 50-100 µm P = 10-20 W λ = 10.6 µm S = N/A T = N/A V = 1270-2540 mm/s and 2032 mm/s 65-75 • C bed temp and 80 • C bed temp for larger particlesBall mixing was found to be best for homogenous blends of PVA and HA when compared to tumbler mixer.…”