Immobilisation of hydroxyapatite-collagen on polydopamine grafted stainless steel 316L: Coating adhesion and in vitro cells evaluation

Abstract

The utilisation of hydroxyapatite and collagen as bioactive coating materials could enhance cells attachment, proliferation and osseointegration. However, most methods to form crystal hydroxyapatite coating do not allow the incorporation of polymer/organic compound due to production phase of high sintering temperature. In this study, a polydopamine film was used as an intermediate layer to immobilise hydroxyapatite-collagen without the introduction of high sintering temperature. The surface roughness, coating adhesion, bioactivity and osteoblast attachment on the hydroxyapatite-collagen coating were assessed as these properties remains unknown on the polydopamine grafted film. The coating was developed by grafting stainless steel 316L disks with a polydopamine film. Collagen type I fibres were then immobilised on the grafted film, followed by the biomineralisation of hydroxyapatite. The surface roughness and coating adhesion analyses were later performed by using AFM instrument. An Alamar Blue assay was used to determine the cytotoxicity of the coating, while an alkaline phosphatase activity test was conducted to evaluate the osteogenic differentiation of human fetal osteoblasts on the coating. Finally, the morphology of cells attachment on the coating was visualised under FESEM. The highest RMS roughness and coating adhesion were observed on the hydroxyapatite-collagen coating (hydroxyapatite-coll-dopa). The hydroxyapatite-coll-dopa coating was non-toxic to the osteoblast cells with greater cells proliferation, greater level of alkaline phosphate production and more cells attachment. These results indicate that the immobilisation of hydroxyapatite and collagen using an intermediate polydopamine is identical to enhance coating adhesion, osteoblast cells attachment, proliferation and differentiation, and thus could be implemented as a coating material on orthopaedic and dental implants.

Investigation of Coatings, Corrosion and Wear Characteristics of Machined Biomaterials through Hydroxyapatite Mixed-EDM Process: A Review

“…Consequently, a HAp-based coating is proposed as a perfect candidate for enhancing the biocompatibility, mechanical characteristics, and corrosion resistance of biomaterials. Although HA-based ceramic exhibits a lower Young's modulus, similar to bone, compared to metallic biomaterials, bio-implants made from HA-based ceramics have proven to be inappropriate for load-bearing conditions because of their poor crystallinity and brittleness [11,40,48,[66][67][68][69]. Therefore, HAp is utilized as additive powders for the purpose of coating formation, and which promotes both the mechanical and the biological properties of the biomaterials.…”

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

“…The effect of coating stability on osteointegration performance of coated metallic implants can be examined by numerous techniques, including micro X-ray computed tomography (micro-CT), scanning electron microscopy, and histological examinations by laser scanning confocal fluorescence microscopy [249,250]. However, in order to achieve reliable results of implant-stability investigation, it is also worth considering the use of friction and wear tests of coatings [251], examination of the shear strength of the bone implant interface in an in vivo model [252], and the strength of coating adhesion as well [253].…”

Is polydopamine beneficial for cells on the modified surface?

“…PDA coatings have been applied to facilitate highly efficient bindings of growth factors, bioactive proteins or functional peptides on bioinert substrates for realizing the bio-related functions of materials or regulating cell behaviors [ 10–13 ]. Among these strategies, bioactive modifications by anchoring bioactive substances assisted by PDA has been quite popular to enhance or regulate proliferation, migration and differentiation of many types of cells and eventually promote the performance of biomaterials and medical devices [ 14–17 ].…”