Properties of zinc doped hydroxyapatite bioceramic developed by using calcium precursor derived from biogenic waste / Mardziah Che Murad

Mardziah , Che Murad (2022) Properties of zinc doped hydroxyapatite bioceramic developed by using calcium precursor derived from biogenic waste / Mardziah Che Murad. PhD thesis, Universiti Malaya.

	PDF (The Candidate's Agreement) Restricted to Repository staff only Download (218Kb)
	PDF (Thesis PhD) Download (4Mb)

Abstract

The calcium derived from biogenic wastes materials is an inexpensive and innovative alternative to using commercial calcium reagents for producing various types of calcium phosphate bioceramics suitable for clinical applications. This research aims to synthesize zinc-substituted hydroxyapatite using calcium oxide derived from waste eggshells (ZnHA-Es) via chemical precipitation method and to evaluate its chemical, physical and mechanical properties as well as the cytotoxicity behaviour of the derived bioceramics. The performance of the ZnHA-Es was also compared with ZnHA that were synthesized using commercial calcium reagent. The concentration of Zn was set at 1 mol% (1ZnHAEs), 3 mol% (3ZnHA-Es) and 5 mol% (5ZnHA-Es). The derived powders were calcined at 700 °C and presureless sintered at various temperatures (1100 to 1300°C). Brunauer- Emmett-Teller (BET) specific surface area measurement of all synthesized powders were above 90 m2/g and composed of hydroxyapatite as the major crystalline phase. Transmission electron microscopy (TEM) micrographs showed that the zinc-free HA (HA-Es) and ZnHA-Es particles have nano-rod shape and were highly agglomerated. For densification study, it was found that sintering at 1250 °C resulted in an improvement in the mechanical properties of the ZnHA-Es when compared to the ZnHA samples. In particular, it was revealed that sintering at this temperature, the 5ZnHA-Es exhibited the highest fracture toughness of 1.55 ± 0.06 MPa.m1/2, grain size of 1.64 ± 0.20 μm, Vickers hardness of 3.01 ± 0.08 GPa and relative density of 94.6 ± 0.06%. This enhancement of the fracture toughness was attributed to the presence of minor β-TCP phase when 5 mol% zinc ion was incorporated into HA, combined with enhanced densification at 1250°C. Cytotoxicity analysis through methyl thiazole tetrazolium (MTT) assay indicated that both HA-Es and 5ZnHA-Es were non-toxic. Nevertheless, the 5ZnHA-Es specimen showed more than 90% of cell viability after 24 h exposure in the MTT assay solution, compared to only 81% for HA-Es sample. This finding inferred that the presence of Zn ion promoted cells proliferation more effectively than HA-Es. This work had provided an insight on the feasibility of using natural calcium extracted from waste eggshells as starting material in the preparation of Zn-substituted HA, suitable for biomedical applications.

Actions (For repository staff only : Login required)