A comprehensive review of additively manufactured biomedical titanium alloys for bone tissue engineering: Biocorrosion, biomechanical, and biological properties

Abstract

In recent years, additive manufacturing has evolved rapidly in the healthcare industry to address rising demands for patient-specific, complex tissue scaffolds, vascular stents, dental and orthopedic implants, bone prostheses, and biomedical devices. Additively manufactured Ti-based scaffolds manifest a controllable combination of essential properties such as modulated porosity fraction, optimized porous architecture, tuned Young's modulus, and adjustable mechanical properties. Accordingly, the 3D-printed scaffolds favorably mimic natural bone structure and properties, eliminate stress-shielding effects, and enhance osteogenesis and osseointegration, offering significant advantages over traditional Ti-based bioimplants. Besides, microstructural features, hardness, wettability, surface properties, tensile and compression strength, fatigue life, and ductility affect the bioimplants' longevity and biological and biocorrosion performance. Herein, printability, in-vivo performance, and in-vitro characteristics of additively manufactured beta and alpha + beta Ti-based and Ni-Ti bio-alloys were holistically reviewed as promising alternatives to Ti-6Al-4V alloy in advanced manufacturing of bioimplant and tissue engineering scaffolds. The effects of AM processing parameters, post-surface and post-heat treatment on the microstructure, and the alloys' critical mechanical, biological, and corrosion properties were elucidated. We scrutinized the opportunities and challenges of using the most promising binary and multi-component AM beta-Ti alloys with superb properties in bone tissue engineering for better clinical applications. It gave a foretaste of biomimetic design of novel 3D beta-Ti scaffolds as local drug delivery systems for biological macromolecule-based drugs and growth factors in regenerative medicine and cancer therapy.