Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite

Abstract

Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments.

PVA-based hydrogels for tissue engineering: A review

“…As shown in Fig. 8, the surface coating on bundle of PVA hydrogel fibres can be tuned from 0 to over 55% by increasing amount of HAp in PVA/HAp weight ratio (from 0.4 to 0.1).Further, it was observed that these coatings adhere well to the fibre bundles and detach by crack propagation inside the coating and may provide a guidance to select coatedimplants for anchoring artificial ligaments[249]. Chen et al 2015 prepared PVA-HAp hydrogel for articular cartilage (as a porous hydrated tissue covering the end of each bone at the joints[250]) and investigated the fluid load support mechanism under conditions of swing friction followed by the influence of load and swing angle on fluid load support.The swinging of Co-Cr-Mo ball on the surface of composite hydrogel showed the support mechanism, where its fluid flows to the surface, thereby reducing the friction between the ball and composite hydrogel and a small amount of fluid flows back inside the composite hydrogel, thereby restoring its mechanical properties.…”

Design of a Novel 3D Printed Bioactive Nanocomposite Scaffold for Improved Osteochondral Regeneration

“…nHA is the bioactive and osteoconductive chemical component in bone and the calcified zone in cartilage. 54-56 Hydroxyapatite and its derivatives have been studied and shown to increase cell-scaffold performance via incorporation within a bulk matrix as well as surface adsorption 57-59 and nucleation. 60-62 Through a hydrothermal treatment method, our lab can synthesize more biomimetic nHA with excellent control of the crystalline phase and surface morphology at the nano scale.…”

Integrating biologically inspired nanomaterials and table-top stereolithography for 3D printed biomimetic osteochondral scaffolds

“…Specifically, one of the key nanomaterials utilized in the manufacture of our graded osteochondral scaffold, nHA, can provide several key benefits to include: mechanical reinforcement, nanotexturization, and osteoconductivity. As a bioactive and osteoconductive chemical component in bone and the calcified zone in cartilage, 25,38,39 hydroxyapatite and its chemical derivatives have been extensively studied and shown to increase cell-scaffold performance via incorporation within a bulk matrix 3 as well as surface adsorption [40][41][42] and in situ nucleation. [43][44][45] Through a hydrothermal treatment method, our lab readily synthesizes biomimetic nHA with excellent control of nano scale crystallinity and surface morphology.…”