Zn-doped chitosan/alginate multilayer coatings on porous hydroxyapatite scaffold with osteogenic and antibacterial properties

Abstract

Porous hydroxyapatite (HA) scaffolds prepared by three-dimensional (3D) printing have wide application prospects owing to personalized structural design and excellent biocompatibility. However, the lack of antimicrobial properties limits its widespread use. In this study, a porous ceramic scaffold was fabricated by digital light processing (DLP) method. The multilayer chitosan/alginate composite coatings prepared by layer-by-layer method were applied to scaffolds and Zn2+ was doped into coatings in the form of ion crosslinking. The chemical composition and morphology of coatings were characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Energy dispersive spectroscopy (EDS) analysis demonstrated that Zn2+ was uniformly distributed in the coating. Besides, the compressive strength of coated scaffolds (11.52 ± 0.3 MPa) was slightly improved compared with that of bare scaffolds (10.42 ± 0.56 MPa). The result of soaking experiment indicated that coated scaffolds exhibited delayed degradation. In vitro experiments demonstrated that within the limits of concentration, a higher Zn content in the coating has a stronger capacity to promote cell adhesion, proliferation and differentiation. Although excessive release of Zn2+ led to cytotoxicity, it presented a stronger antibacterial effect against Escherichia coli (99.4%) and Staphylococcus aureus (93%).

Biocomposite Coatings Doped with Magnesium and Zinc Ions in Chitosan Matrix for Antimicrobial Applications

“…This behavior could be attributed either to the gradual release of magnesium and zinc ions from the hydroxyapatite, or to chitosan matrix degradation. Although novel materials based on metallic ions have recently been investigated for their antimicrobial activity, the information regarding the mechanisms involved in the antimicrobial features of these ions is still scarce [ 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 ]. Over the years, various studies have reported different mechanisms that could be deemed responsible for the antimicrobial properties of materials.…”

“…Another possible antimicrobial mechanism of zinc ions is their ability to activate immune cells, macrophages, and neutrophils, which could boost the body’s defenses against microbial infections. The generation of reactive oxygen species (ROS), that could damage cellular components and eventually lead to cell death was also reported as a possible antimicrobial mechanism of zinc [ 65 , 66 , 67 , 70 , 76 , 78 ]. Overall, the proposed antimicrobial mechanisms of zinc ions rely on a combination of both the direct and indirect effects of zinc against microbial cells and the human immune system.…”

“…In addition, magnesium has been reported to exhibit very good antifungal properties. Studies investigating the effects of magnesium ions against the common fungal pathogen, Candida albicans , showed that magnesium ions inhibited fungal cell growth and promoted the formation of reactive oxygen species, which have a significant toxic effect on fungal cells [ 61 , 63 , 76 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. In addition, chitosan is a natural polysaccharide found in the shells of crustaceans and in the cell walls of fungi.…”

“…Another important aspect of the proposed antimicrobial mechanism of chitosan is its ability to alter microbial cells’ surfaces by binding to their surface proteins, lipids, and other macromolecules. This could lead to the inhibition of microbial adhesion, biofilm formation, and colonization, thus eventually leading to the inhibition of microbial growth and survival [ 68 , 69 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 ]. These properties demonstrated that zinc and magnesium ions, as well as chitosan, exhibit significant antimicrobial properties against various type of bacteria and fungi.…”

Effects of hydroxyapatite-coated porous titanium scaffolds functionalized by exosomes on the regeneration and repair of irregular bone

“…HA has been utilized in clinical practice for numerous years due to its similar structural composition to bone tissue and its satisfactory biocompatibility (Bordea et al, 2020;Duan et al, 2020;Huang et al, 2022). Moreover, HA exhibits positive bone conductivity, which promotes the adhesion and development of bone tissue (He et al, 2023). It creates chemical bonds with bone tissue, thus improving the integration between the material and bone tissue.…”