Surface Treatment and Bioinspired Coating for 3D-Printed Implants

Abstract

Three-dimensional (3D) printing technology has developed rapidly and demonstrates great potential in biomedical applications. Although 3D printing techniques have good control over the macrostructure of metallic implants, the surface properties have superior control over the tissue response. By focusing on the types of surface treatments, the osseointegration activity of the bone-implant interface is enhanced. Therefore, this review paper aims to discuss the surface functionalities of metallic implants regarding their physical structure, chemical composition, and biological reaction through surface treatment and bioactive coating. The perspective on the current challenges and future directions for development of surface treatment on 3D-printed implants is also presented.

Keywords: 3D printing; bioactive coating; bioglass; hydroxyapatite; metallic implant; micro-arc oxidation; osseointegration; surface treatment.

FIGURE 1

Schematic diagram of the (A) risk associated within FDA-classified medical devices; and some graphics of 3D-printed biomedical applications in the human body system. (B) Cranial implant (Jardini et al., 2016). (C) Cochlear implant (Brand et al., 2014). (D) Dental implant (Yin et al., 2021). (E) Knee implant (Chithartha et al., 2020). (F) Hip implant (Mattei et al., 2011).

FIGURE 2

A step-by-step approach of design control and performance evaluation to achieve successful fabrication of a 3D-printed biomedical implant (Wang et al., 2017).

FIGURE 3

(A) The start of foreign ions leaching, adversely affecting (B) immune response activities leading to bone resorption and implant failure. Image remodeled from Souza et al. (2020).

FIGURE 4

The tissue responsive effect on various metallic elements in the implant. Image remodeled from Steinemann (1998).

FIGURE 5

Protein adsorption on the substrate from (A) nano-to-macro level which is dependent on several factors. (B) Surface roughness (Stich et al., 2021). (C) Surface chemistry and surface energy (Meng et al., 2017). Diagram adapted and adjusted from Alipal et al. (2021).

FIGURE 6

A study on cell interaction and cell-growth concentration as pore shape changes. Reproduced from Rumpler et al. (2008).

FIGURE 7

Computer-aided design (CAD) model of multiplanar hexagonal unit cell structures with a macroscopical view of an MAO-treated scaffold (B); the MAO-treated scaffold at the (A) outer surface and (C) central surfaces. (D) The illustrative diagram shows the simultaneous generation of microporous topography and bioactive elements on the macroporous scaffold by MAO treatment in a Ca-Ethylenediaminetetraacetic acid (EDTA)–containing electrolyte and (E) the noncumulative and cumulative release curves of Ca²⁺ in phosphate-buffered saline (PBS) for 28 days; scanning electron microscope (SEM) images of the implant surface before and after immersion for 28 days are shown on the right side. (F) SEM image of the untreated porous Ti64 scaffold immersed in stimulated body fluid (SBF) for 14 days and (G) SEM image of the MAO-treated scaffold immersed in SBF for 3 days. Image reproduced from Xiu et al. (2016).

FIGURE 8

Formation of titanium alloy coating through alkali–heat treatment and HA-electrodeposited surface treatment. Image reproduced from Song et al. (2019).

FIGURE 9

A summary of bioactivity assessment conducted on different types of bioactive coating resulting in cell adhesion capability; (A) calcium phosphate (Heimann 2013). (B) Carbon nanomaterial (Li et al., 2011). (C) Biphasic calcium phosphate (Ebrahimi et al., 2017; Behera et al., 2020). (D) Bioglass (Tabia et al., 2021).