Nanostructure of bioactive glass affects bone cell attachment via protein restructuring upon adsorption

Abstract

The nanostructure of engineered bioscaffolds has a profound impact on cell response, yet its understanding remains incomplete as cells interact with a highly complex interfacial layer rather than the material itself. For bioactive glass scaffolds, this layer comprises of silica gel, hydroxyapatite (HA)/carbonated hydroxyapatite (CHA), and absorbed proteins—all in varying micro/nano structure, composition, and concentration. Here, we examined the response of MC3T3-E1 pre-osteoblast cells to 30 mol% CaO–70 mol% SiO2 porous bioactive glass monoliths that differed only in nanopore size (6–44 nm) yet resulted in the formation of HA/CHA layers with significantly different microstructures. We report that cell response, as quantified by cell attachment and morphology, does not correlate with nanopore size, nor HA/CHO layer micro/nano morphology, or absorbed protein amount (bovine serum albumin, BSA), but with BSA’s secondary conformation as indicated by its β-sheet/α-helix ratio. Our results suggest that the β-sheet structure in BSA interacts electrostatically with the HA/CHA interfacial layer and activates the RGD sequence of absorbed adhesion proteins, such as fibronectin and vitronectin, thus significantly enhancing the attachment of cells. These findings provide new insight into the interaction of cells with the scaffolds’ interfacial layer, which is vital for the continued development of engineered tissue scaffolds.

Transformation from calcium sulfate to calcium phosphate in biological environment

“…Since the theoretical densities of CaSO 4 and SrSO 4 are 2.96 g/cm 3 [15,16] and 3.96 g/cm 3 [17], respectively, the theoretical density of (Ca,7.6%Sr)SO 4 is 3.06 g/cm 3 . The density after heat treatment at 1100 °C for 1 h is 2.84 ± 0.01 g/cm 3 , corresponding to a relative density of 93.5 ± 0.3%. The remaining pores within the specimen are not likely interconnected [18].…”

“…Indeed, the presence of calcium phosphate could induce the differentiation of mesenchymal stem cells to bone tissue [ 2 ]. A recent study further indicated that the attachment of cells could be related to the re-structuring of protein on apatite [ 3 ]. Thamma et al suggested that the bioactivity of the bioceramic was determined only by its surface, with the composition of the bulk bioceramic itself mattering little [ 3 ].…”

“…Characteristics of (Ca,Sr)SO 4 specimen Values SrSO 4 content in the starting powder mixture/wt% 10 Sr content in (Ca,Sr)SO 4 /mol% 7.6Density after heat treatment/g/cm3 2.84 ± 0.01…”

Bone Tissue Response to Different Grown Crystal Batches of Octacalcium Phosphate in Rat Long Bone Intramedullary Canal Area

“…Mg 2+ and F − are assumed to be approximately zero. The solubility product constants used were 7.36 × 10 −60 (mol/L) 9 for HA [38], 2.51 × 10 −49 (mol/L) 8 for OCP [39], and 2.77 × 10 −7 (mol/L) 2 for DCPD [40] at 37 • C.…”

“…The surface microstructure of BCP modulates osteoclastogenesis and alters ectopic bone formation [7]. Furthermore, the microstructure of bioglass (30 mol% CaO-70 mol% SiO 2 porous bioactive glass) promotes MC3T3 cell adhesion as the β-sheet/α-helix ratio of adsorbed BSA protein increases [8].…”