Synthesis of composite based on vinyl ether of ethylene glycol structured nano particles hydroxyapatite

Temirkhanova G.E., Trubitsin M.A., Mun G.A., Urkymbaeva P.Y

National research university Belgorod State University, Belgorod

Al-Farabi Kazakh National University, Almaty

guldenka_t@mail.ru

Abstract:Millions of people are suffering from bone defect arising from trauma, tumor or bone diseases. Therefore, there is a growing need for the development of biocomposites with excellent bioactivity and compatibility. In this study,hydroxyapatite (HAp) nanorod embedded composite was prepared using vinyl etherof ethylene glycol(VEEG) as a matrix.The role of VEEG composition on the crystallite size, degree of crystallinity, functional groups and morphology of nanocomposites were characterised by TEM analysis. The results indicated that the size and crystallinity of Hapnano particles decreases with increase in VEEG concentration in the composite. This shows the size control effect of VEEG concentration on HApnanorods. Due to the chemical bond interactions between HAp and VEEG. TEM micrograph confirms the presence of Hapnano rod crystals in VEEG matrix.

1.Introduction

The calcium phosphate based bioceramics particularly hydroxyapatite (HAp) play an excellent role in biomedical applications owing to their excellent biocompatible, osteoconductive and bioactive properties, and its close chemical and physical resemblance to mineral component of bone tissue, enamel and dentin. The major mineral phase of bone is hydroxyapatite (HAp) with a ratio of calcium-to-phosphate is 1.67 which is embedded as nanocrystalline form in collagen triple helix structure. Currently, researchers are trying to mimic this natural nano composite system for tissue engineering applications. Since, the nanoHAp with high surface area to volume ratio is more desirable to increase their contribution in bone/tooth implants, adsorbents, gene delivery and immune sensor. However, the brittleness and poor performance of mechanical stability of pure HAp limit its use for the regeneration of non-load-bearing bone defects and tissue engineering applications.Composite biomaterials like metal and polymer matrix are used to improve the mechanical compatibility of nanoHAp (n-HAp). Generally, the composite biomaterials are prepared by using biocompatible/biodegradable synthetic/natural polymers [1].

The inorganic minerals such as hydroxyapatite, bioactive glasses, metal oxides, and carbon nanotube are incorporated into polymer matrixes to impart bioactivity. This enables us to developed the composite with desired properties. The addition of nanosized particles is desirable to develop the composite with a good mechanical strength since the natural bone contains mineral crystals which are at the nanometer scale and embedded in the collagen matrix. The polymer composites are designed to meet the specific requirement of biomedical applications like tissue engineering and drug delivery system. The right choice of the composition of both filler and polymer matrix are essential in addition to the process method to obtain suitable biopolymer composites. Recently, attempts have been made to develop nanocomposites, wherein n-Happarticles are embedded in VEEG polymeric matrices [2].

An extensive study have been made on both natural (collagen, gelatin, silk fibroin) and synthetic (polyethylene, polyamide, chitosan, polystyrene, poly (vinyl alcohol) and polyetherethilenglicole) polymers to overcome the mechanical problems associated with bioceramics in bone tissueengineering applications [3-5].Among the above polymers, VEEG remain one of the widely used polymer group of biomaterials applied for medical implants. This usage is due to its segmented block co-polymer character. This wide range of versatilityin terms of tailoring their applications such as tissue scaffolding, artificial cartilage and biodegradable scaffolds.

With the superior combination of the synergic effect and biocompatible HAp and the adjustable biodegradability of polymer matrix, HApnanorod embedded VEEG composites were prepared under controlled environment. The obtained nanoHAp/VEEG composites were characterised in light of crystallite size, degree of crystallinity, morphology, biological and mechanical properties [6].

2. Formation mechanism of HAp/VEEGnanocomposite

Fig. 1 shows the schematic representation of the synthesis of HAp/VEEG nanocomposite. When the calcium hydroxide was added to the VEEG solution, the Ca²⁺ ions were attached with OH^-group in the VEEG matrix. Following the above step, orthophosphoric acid was added drop by drop into the above mixed solution. As a result, PO^3-ions bind to the –OH^- and Ca²⁺group to form hydroxyapatite particles and the VEEG matrix regulates the growth of c-axis of HApnanorod.

Figure 1.TEM micrographs of the prepared nanohydroxyapatite samples: (a) without polymer, (b) with polymer

3.Transmission electron microscopy analysis

TEM(Jeol JEM-2100) images of pure n-HApand vinyl etherof ethylenglycolcompositions are illustrated in Fig.1. The TEM picture shows that particles exhibit nanorod morphology. In case of composites, when the composition of VEEG is added to HAp, the rod-like morphology starts to disappear. According to TEM analysis, the particles are homogeneously dispersed in polymer matrix. Further, the micrograph does not show any notable indication for the existence of agglomeration.

4. Conclusion

In the present work, novel hydroxyapatite/vinyl etherof ethylenglycolnanocomposite is prepared by simple chemical route. It inferred that the composition of VEEG shows significant influence on particle size, degree of crystallinity and microhardness, which facilitate to optimize the composition of composite for particular applications.

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