The pathway to intelligent implants: osteoblast response to nano silicon-doped hydroxyapatite patterning

Abstract

Bioactive hydroxyapatite (HA) with addition of silicon (Si) in the crystal structure (silicondoped hydroxyapatite (SiHA)) has become a highly attractive alternative to conventional HA in bone replacement owing to the significant improvement in the in vivo bioactivity and osteoconductivity. Nanometre-scaled SiHA (nanoSiHA), which closely resembles the size of bone mineral, has been synthesized in this study. Thus, the silicon addition provides an extra chemical cue to stimulate and enhance bone formation for new generation coatings, and the next stage in metallic implantation design is to further improve cellular adhesion and proliferation by control of cell alignment. Topography has been found to provide a powerful set of signals for cells and form contact guidance. Using the recently developed novel technique of template-assisted electrohydrodynamic atomization (TAEA), patterns of pillars and tracks of various dimensions of nanoSiHA were achieved. Modifying the parameters of TAEA, the resolution of pattern structures was controlled, enabling the topography of a substrate to be modified accordingly. Spray time, flow rate and distance between the needle and substrate were varied to improve the pattern formation of pillars and tracks. The 15 min deposition time provided the most consistent patterned topography with a distance of 50 mm and flow rate of 4 ml min 21. A titanium substrate was patterned with pillars and tracks of varying widths, line lengths and distances under the optimized TAEA processing condition. A fast bone-like apatite formation rate was found on nanoSiHA after immersion in simulated body fluid, thus demonstrating its high in vitro bioactivity. Primary human osteoblast (HOB) cells responded to SiHA patterns by stretching of the filopodia between track and pillar, attaching to the apex of the pillar pattern and stretching between two. HOB cells responded to the track pattern by elongating along and between the track, and the length of HOB cells was proportional to the gaps between track patterns, but this relationship was not observed on the pillar patterns. The study has therefore provided an insight for future design of next generation implant surfaces to control and guide cellular responses, while TAEA patterning provides a controllable technique to provide topography to medical implants.

Nanohydroxyapatite shape and its potential role in bone formation: an analytical study

“…These NPs potentially have an important role in bone tissue engineering, forming nanosized building blocks for bone tissue repair and/or replacement. Thian et al evaluated the bioactivity of electrohydrodynamic atomized nanoapatite [9], as well as studying nanostructured HA coatings produced using magnetron sputtering and electrohydrodynamic spraying [10][11][12][13]. Nanoapatite has also been observed to form in various shapes, and with different aspect ratios, when synthetic HA has been incubated in simulated body fluid that contains similar ion levels to blood plasma [14].…”

Biomechanical evaluation and surface characterization of a nano-modified surface on PEEK implants: a study in the rabbit tibia

“…27,28 With a thickness of 10-20 nm and HA crystals with similar size and shape as those found in human bone, it was suggested that the novel coating facilitates implant integration. 27,29,30 Furthermore, since the nanosized HA coating is a monolayer, the risk of detachment is hypothesized to be lower than that of the thicker HA coatings. A recently published study, using an identical HA coating as in the present study, revealed a higher mean bone-to-implant contact for HA, indicating a higher level of osseointegration.…”

A Novel Surface Topographical Concept for Bone Implant

“…Thus, the concept of a nano-sized silicon-substitute hydroxyapatite (nanoSiHA) coated implant with 3-D surface topographies to guide bone tissue remodelling, has become attractive. Recently, a new technique, template-assisted electrohydrodynamic atomization (TAEA) spraying, is of considerable interest in surface topography formation [6,7]. TAEA has been developed from electrohydrodynamic atomization spraying, an electric-driven jet-based deposition method.…”