Strategies for Using Polydopamine to Induce Biomineralization of Hydroxyapatite on Implant Materials for Bone Tissue Engineering

Abstract

In the field of tissue engineering, there are several issues to consider when designing biomaterials for implants, including cellular interaction, good biocompatibility, and biochemical activity. Biomimetic mineralization has gained considerable attention as an emerging approach for the synthesis of biocompatible materials with complex shapes, categorized organization, controlled shape, and size in aqueous environments. Understanding biomineralization strategies could enhance opportunities for novel biomimetic mineralization approaches. In this regard, mussel-inspired biomaterials have recently attracted many researchers due to appealing features, such as strong adhesive properties on moist surfaces, improved cell adhesion, and immobilization of bioactive molecules via catechol chemistry. This molecular designed approach has been a key point in combining new functionalities into accessible biomaterials for biomedical applications. Polydopamine (PDA) has emerged as a promising material for biomaterial functionalization, considering its simple molecular structure, independence of target materials, cell interactions for adhesion, and robust reactivity for resulting functionalization. In this review, we highlight the strategies for using PDA to induce the biomineralization of hydroxyapatite (HA) on the surface of various implant materials with good mechanical strength and corrosion resistance. We also discuss the interactions between the PDA-HA coating, and several cell types that are intricate in many biomedical applications, involving bone defect repair, bone regeneration, cell attachment, and antibacterial activity.

Keywords: bio-implant materials; bone tissue generation; hydroxyapatite; improved biomineralization; polydopamine.

Figure 1

Polydopamine Hydroxyapatite Functionalization (pHAF) approach to improving the physical properties and biological properties for bone tissue engineering materials.

Figure 2

Schematic illustration of the polymerization of dopamine into polydopamine under the alkaline condition.

Figure 3

(a) Schematic illustration of polydopamine-assisted hydroxyapatite functionalization (pHAF) coating of the PDA layer by auto-oxidation of the DA on the substrate, followed by the mineralization of HA on PDA layer in SBF solution. Characterization of HA formed on the PDA-coated Titanium substrate: (b) TEM, (c) EDX, (d) XRD. Reprinted with permission from reference [2]. Copyright Wiley 2010.

Figure 4

Schematic illustration and scanning microscopic images of the SF scaffold engineered with two-stage hydroxyapatite functionalization. Enhanced collagen deposition in critical-sized calvarial bone defects, eight weeks after human adipose-derived mesenchymal stem cell transplantation with two-stage hydroxyapatite-functionalized silk fibroin (SF) scaffolds and improved bone regeneration. Reprinted with permission from reference [43]. Copyright (2018) American Chemical Society.

Figure 5

(a) Scanning electron microscopic (SEM) images of bare porous Ti6Al4V scaffolds (pTi) and polydopamine-assisted hydroxyapatite coating on titanium surfaces (HA/pDA-pTi). Fluorescent staining of MC3T3-E1 cells adhered to pTi and HA/pDA-pTi scaffolds, and (b) analysis of morphology of SEM images as shown in panel a and (c) fluorescence intensity of vinculin staining for cells on different scaffolds. Asterisks (*) indicate statistical significance compared to the pTi group, p < 0.05). Reprinted with permission from reference [55]. Copyright (2015) American Chemical Society.

Figure 6

Schematic for the preparation PLLA/pDA/HA, PLLA/pDA/Hep/BMP-2, and PLLA/pDA/HA/Hep/BMP-2 disk and screw samples based on the pHAF method. Reprinted with permission from reference [66]. Copyright Elsevier 2018.

Figure 7

(a) The upper hydrogel layer for cartilage defect repair was prepared by mixing Gelatin methacryloyl (GelMA) with polydopamine (PDA) (b) The prepared lower layer hydrogel for subchondral bone repair was prepared by mixing Ca²⁺-GelMA with PO₄³⁻-GelMA to generate hydroxyapatite (HA). (c) Combination of these two hydrogels to form the final structure of the hydrogel bilayer. (d) Illustration of the application of the hydrogel bilayer for the bone defect repair. Reprinted with permission from reference [71]. Copyright © 2019 WILEY-VCH.