Defining the Properties of an Array of –NH2-Modified Substrates for the Induction of a Mature Osteoblast/Osteocyte Phenotype from a Primary Human Osteoblast Population Using Controlled Nanotopography and Surface Chemistry

Abstract

Accelerating the integration of a joint replacement or the healing of a bone fracture, particularly a complicated non-union fracture, would improve patient welfare and decrease healthcare costs. Currently, an autologous bone graft is the gold standard method for the treatment of complicated non-union fractures, but it is not always possible to harvest such a graft. A proactive highly inductive so-called smart material approach is pertinent in these cases. In this study, the surface chemistry of a previously approved material with desirable bulk material properties was modified to investigate its potential as an economical and effective alternative. The objective was to create stable synthetic chemical coatings that could guide cells along the osteogenic lineage required to generate mineralised tissue that would induce and accelerate bone healing. Primary human osteoblast-like cells were cultured in vitro for 7, 14 and 28 days on amine-terminated (chain length in the range 3–11) silane-modified glass surfaces with controlled nanotopography, to determine how surface chemistry and nanotopography change osteoblast function. The materials were characterised using atomic force microscopy (AFM), scanning electron microscopy (SEM), water contact angle (WCA) and a novel ninhydrin assay. The cells were analysed using qRT-PCR, von Kossa tinctural staining for mineralisation, and visualised using both transmitted white light and electron microscopy. Bone-like nodules, quantified using microscopy, only formed on the short-chain (chain length 3 and 4) amines after 7 days, as did the up-regulation of sclerostin, suggestive of a more mature osteoblast phenotype. In this paper, we report more rapid nodule formation than has previously been observed, without the addition of exogenous factors in the culture medium. This suggests that the coating would improve the integration of implants with bone or be the basis of a smart biomaterial that would accelerate the bone regeneration process.Electronic supplementary materialThe online version of this article (doi:10.1007/s00223-016-0202-y) contains supplementary material, which is available to authorized users.

The optimization and production of stable homogeneous amine enriched surfaces with characterized nanotopographical properties for enhanced osteoinduction of mesenchymal stem cells

“…Parallel studies have proven that the CL11 substrates that were highly osteoinductive (ability to induce osteogenesis in MSCs) did not display significantly enhanced osteoconductive (ability to enhance the function of osteoblasts) behavior in vitro . Instead the shorter chain silanes supported osteoblast clustering and resulted in an upregulation of osteoblast activity and production of calcified matrices . This proves that different combinations of submicron material stimuli are required to increase the efficiency of different cell phenotypes in vitro .…”

“…The enhanced level of osteogenic cell maturity and production of an organized osteogenic rich extra cellular matrix was only observed on the CL11 modified surfaces. It is essential to reiterate that the observed cellular response on the CL11 surfaces was homogenous across the entirety of the surface, therefore, proving that modification with CL11 –NH 2 silanes is an effective mechanism to produce cost effective osteoinductive coatings on different base substrates over a large surface area …”

Cost effective optimised synthetic surface modification strategies for enhanced control of neuronal cell differentiation and supporting neuronal and Schwann cell viability

“…Previous studies have demonstrated that changing the chain length of silane changes the surface topography of a substrate, via deposition of amine groups, therefore controlling initial cell adhesion and influencing cellular differentiation 9 . Silane chain length has been previously shown to control osteo‐induced differentiation of mesenchymal stem cells, and a similar effect was hypothesized for neuronal cell differentiation 10 .…”

“…Previous work has demonstrated enrichment of surfaces with chemical reactive groups including amines, hydroxyl, and carboxyl 5 . Silane modification can mimic the ECM by changing surface nano‐topography, and substrate chemistry, providing a biological surface to enhance initial cell attachment and maintain proliferation 9 . Silane chain length has been shown to influence deposition of the chemical reactive group at submicron scale, and influence cell adhesion and differentiation due to topographic profile 9 …”

Molecular layer deposition builds biocompatible substrates for epithelial cells

“…Understanding surface chemistry of biomaterials becomes increasingly important for progress of regenerative medicine [1][2][3] as the initial interaction of biomaterials with cells is determined by parameters that define surface chemistry including wetting behavior, surface charge, homogeneity, functional groups, and surface topography. [4][5][6] Transplant materials usually need surface modifications to increase biocompatibility and to preserve the engineered function of the implant.…”