Role of phase separation on the biological performance of 45S5 Bioglass®

Abstract

We analyzed the biological performance of spinodally and droplet-type phase-separated 45S5 Bioglass generated by quenching the melt from different equilibrium temperatures. MC3T3-E1 pre-osteoblast cells attached more efficiently to 45S5 Bioglass® with spinodal than to the one with droplet morphology, providing the first demonstration of the role of micro-/nano-scale on the bioactivity of Bioglass®. Upon exposure to biological solutions, phosphate buffered saline (PBS) and cell culture medium (α-MEM), a layer of hydroxyapatite (HA) formed on both glass morphologies. Although both Bioglass® varieties were incubated under identical conditions, and physico-chemical characteristics of the HA layers were similar, the adsorption magnitude of a model protein, bovine serum albumin (BSA, an abundant blood serum component) and its β-sheet/β-turn ratio and α-helix content were significantly higher on spinodal than droplet type Bioglass®. These results indicate that: (i) a protein layer quickly adsorbs on the surface of 45S5 Bioglass® varieties (with or without HA layer), (ii) the amount and the conformation of adsorbed proteins are guided by the glass micro-/nano-structure, and (iii) cell attachment and proliferation are influenced by the concentration and the conformation of attached proteins with a significantly better cell adhesion to spinodal type 45S5 Bioglass® substrate. Taken together, our results indicate that the biological performance of 45S5 Bioglass® can be improved further with a relatively simple, inexpensive fabrication procedure that provides a superior glass micro-/nano-structure. A simple modification to the fabrication procedure of classic 45S5 Bioglass® generates spinodal (A(a)) and droplet (A(b)) varieties and has a significant impact on protein adsorption (B) and cell adhesion (C).

Effects of Titanium Implant Surface Topology on Bone Cell Attachment and Proliferation in vitro

“…Cells on smooth titanium and TC plastic proliferated rapidly (24.7 ± 2.8 and 22.6 ± 2.7-hour generation time), while cells on PEEK and rough titanium proliferated much more slowly (31.2 ± 2.4 and 41.4 ± 12.8-hour generation time), correlating with PEEK polymer’s inert, less favorable biological properties, 5 and with other rough surfaces including porous bioactive glasses that we characterized previously. 44–49 Our findings also correlate with an earlier study performed on the plasma sprayed Ti-PEEK composite implants investigated here. 13 …”

“…Interestingly, many of the biological characteristics described for rough and porous titanium implants are shared by other engineered implant materials, eg, highly porous bioactive glasses that we fabricated and characterized in detail previously. 44–49 Porous bioactive glasses, as described for roughened titanium surfaces above, form a layer of HA, readily absorb proteins, reduce osteoblast adhesion and proliferation, and stimulate pre-osteoblast differentiation. 44–49 Furthermore, research including our own has shown that these cellular responses are largely driven by the material’s chemical and physical surface characteristics.…”

“… 44–49 Porous bioactive glasses, as described for roughened titanium surfaces above, form a layer of HA, readily absorb proteins, reduce osteoblast adhesion and proliferation, and stimulate pre-osteoblast differentiation. 44–49 Furthermore, research including our own has shown that these cellular responses are largely driven by the material’s chemical and physical surface characteristics. 14 , 16 , 17 , 19 , 23 , 44 , 46 , 47 , 49 Taken together, it becomes clear that increasing surface roughness and porosity not only increase the reactive surface area of the biomaterial, but more importantly that osteoblastic cells are able to detect surface topology on a wide nanometer scale range (tens to hundreds of nanometers), and will react differently, according to specific surface parameters.…”

Evaluation of effectiveness of 45S5 bioglass doped with niobium for repairing critical‐sized bone defect in in vitro and in vivo models

“…Under physiological conditions the glass slowly dissolves releasing calcium and phosphorous ions into solution. Due to its micro-/nano-scale complexity this HCA layer supports the adsorption of adhesive proteins that will further anchor integrin proteins in osteogenic cells, which will allow the cells to attach, spread, and produce mineralized bone matrix while the biomaterial slowly dissolves, until it is completely substituted by the new-formed bone (Hench et al, 1971;Hench et al, 2000;Jones, 2013;Kowal et al, 2017). Due to its micro-/nano-scale complexity this HCA layer supports the adsorption of adhesive proteins that will further anchor integrin proteins in osteogenic cells, which will allow the cells to attach, spread, and produce mineralized bone matrix while the biomaterial slowly dissolves, until it is completely substituted by the new-formed bone (Hench et al, 1971;Hench et al, 2000;Jones, 2013;Kowal et al, 2017).…”

“…These ions then precipitate to form an amorphous calcium phosphorous layer that then crystalizes to form a layer of hydroxyl carbonate apatite (Ca 5 [PO 4 ] 3 OH) (HCA) on its surface (Jones, 2013;Martin, Twyman, Qiu, Knowles, & Newport, 2009). Due to its micro-/nano-scale complexity this HCA layer supports the adsorption of adhesive proteins that will further anchor integrin proteins in osteogenic cells, which will allow the cells to attach, spread, and produce mineralized bone matrix while the biomaterial slowly dissolves, until it is completely substituted by the new-formed bone (Hench et al, 1971;Hench et al, 2000;Jones, 2013;Kowal et al, 2017). Many variations of the original Bioglass 45S5 composition have been designed and investigated in the hope of improving the biological properties (Jones, 2013;Lopes et al, 2013;Lopes et al, 2017;Souza et al, 2018).…”