Mechanical and in vitro biological performance of graphene nanoplatelets reinforced calcium silicate composite.

Mehdi Mehrali,Ehsan Moghaddam,Nahrizul Adib Kadri,Keivan Zandi,Saeid Baradaran,Seyed Farid Seyed Shirazi,Sara Tahan Latibari,Noor Azuan Abu Osman,Mohammad Mehrali,Hendrik Simon Cornelis Metselaar,Alexandre Hiroaki Kihara

doi:10.1371/journal.pone.0106802

Abstract

Calcium silicate (CaSiO3, CS) ceramic composites reinforced with graphene nanoplatelets (GNP) were prepared using hot isostatic pressing (HIP) at 1150°C. Quantitative microstructural analysis suggests that GNP play a role in grain size and is responsible for the improved densification. Raman spectroscopy and scanning electron microscopy showed that GNP survived the harsh processing conditions of the selected HIP processing parameters. The uniform distribution of 1 wt.% GNP in the CS matrix, high densification and fine CS grain size help to improve the fracture toughness by ∼130%, hardness by ∼30% and brittleness index by ∼40% as compared to the CS matrix without GNP. The toughening mechanisms, such as crack bridging, pull-out, branching and deflection induced by GNP are observed and discussed. The GNP/CS composites exhibit good apatite-forming ability in the simulated body fluid (SBF). Our results indicate that the addition of GNP decreased pH value in SBF. Effect of addition of GNP on early adhesion and proliferation of human osteoblast cells (hFOB) was measured in vitro. The GNP/CS composites showed good biocompatibility and promoted cell viability and cell proliferation. The results indicated that the cell viability and proliferation are affected by time and concentration of GNP in the CS matrix.

Highlights

Calcium silicate, (CaSiO3, CS), has been investigated as a bioactive biomaterial for tissue repair and replacement due to its osseointegration properties [1,2,3,4,5]
Powder processing The pristine graphene nanoplatelets (GNP) and 1 wt.% GNP/CS composite powders were analysed prior to sintering in order to evaluate the effectiveness of the mixing and processing
Walker et al [11] reported that the dispersion of GNP using cetyltrimethylammonium bromide (CTAB) occurs because the hydrophobic GNP is attracted to the hydrophobic tails of the surfactant

Summary

Introduction

Calcium silicate, (CaSiO3, CS), has been investigated as a bioactive biomaterial for tissue repair and replacement due to its osseointegration properties [1,2,3,4,5]. Rafiee et al [10,11] have shown that graphene reinforcement in ceramic-matrix composites can provide an excellent toughness, inhibiting the crack propagation and improving mechanical properties. Compared to single layer graphene, graphene nanoplatelets (GNP) are less prone to agglomeration and entanglement due to increased thickness of GNP Because of these properties, GNP has been used as reinforcement in composite materials. Zhao et al [22] used hot pressing (HP) to prepare graphene nanoplatelet (GNP)/biphasic calcium phosphate (BCP) composite, and a 76% increase in fracture toughness was obtained. They employed aqueous colloidal processing methods to obtain a uniform and homogenous dispersion of GNP and BCP ceramic particles. To the best of our knowledge, no study has yet explored the mechanical and biological properties of a free-standing graphene-calcium silicate composite

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