Bioactive Glass 45S5 Powders: Effect of Synthesis Route and Resultant Surface Chemistry and Crystallinity on Protein Adsorption from Human Plasma

Markian S Bahniuk,Larry D Unsworth,Harsh D Singh,Hamidreza Pirayesh,John A Nychka

doi:10.1007/s13758-012-0041-y

Markian S Bahniuk, Larry D Unsworth + Show 3 more

Open Access

https://doi.org/10.1007/s13758-012-0041-y

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Abstract

Despite its medical applications, the mechanisms responsible for the osseointegration of bioactive glass (45S5) have yet to be fully understood. Evidence suggests that the strongest predictor for osseointegration of bioactive glasses, and ceramics, with bone tissue as the formation of an apatitic calcium phosphate layer atop the implanted material, with osteoblasts being the main mediator for new bone formation. Most have tried to understand the formation of this apatitic calcium phosphate layer, and other bioresponses between the host and bioactive glass 45S5 using Simulated Body Fluid; a solution containing ion concentrations similar to that found in human plasma without the presence of proteins. However, it is likely that cell attachment is probably largely mediated via the adsorbed protein layer. Plasma protein adsorption at the tissue bioactive glass interface has been largely overlooked. Herein, we compare crystalline and amorphous bioactive glass 45S5, in both melt-derived as well as sol-gel forms. Thus, allowing for a detailed understanding of both the role of crystallinity and powder morphology on surface ions, and plasma protein adsorption. It was found that sol-gel 45S5 powders, regardless of crystallinity, adsorbed 3-5 times as much protein as the crystalline melt-derived counterpart, as well as a greater variety of plasma proteins. The devitrification of melt-cast 45S5 resulted in only small differences in the amount and variety of the adsorbed proteome. Surface properties, and not material crystallinity, play a role in directing protein adsorption phenomena for bioactive glasses given the differences found between crystalline melt-cast 45S5 and sol-gel derived 45S5.

Highlights

Bioactive glasses, ceramic BioglassÒ formulation 45S5 (45 %SiO2, 24.5 %Na2O, 24.5 %CaO, and 6 % P2O5 by weight), have garnered serious attention as a functional biomaterial due to its ability to integrate with bone
Evidence suggests that the strongest predictor for osseointegration of bioactive glasses, and ceramics, with bone tissue as the formation of an apatitic calcium phosphate layer atop the implanted material, with osteoblasts being the main mediator for new bone formation
Most have tried to understand the formation of this apatitic calcium phosphate layer, and other bioresponses between the host and bioactive glass 45S5 using Simulated Body Fluid; a solution containing ion concentrations similar to that found in human plasma without the presence of proteins

Summary

Introduction

Ceramic BioglassÒ formulation 45S5 (45 %SiO2, 24.5 %Na2O, 24.5 %CaO, and 6 % P2O5 by weight), have garnered serious attention as a functional biomaterial due to its ability to integrate with bone. Previous work has shown that bioactive glass 45S5 can be inserted into areas of large scale bone damage to help augment its repair, while providing structural support by binding strongly to endogenous bone [1,2,3] This material is capable of interacting with the surrounding tissue milieu, and has been shown to serve as a substrate on which osteogenic stem cells can attach and differentiate [2,3,4,5,6,7,8]. The situation is more complicated: cells may not directly attach to these surfaces, rather cell attachment may largely be mediated via adsorbed proteins, and SBF contains no proteins It appears that the adsorption of proteins at the tissue bioactive glass interface has been largely overlooked regarding proxy tests for in vivo animal implantation and histology

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