IN VITRO PREPARATIONS AND STUDIES ON THE SUBSTITUTION OF CADMIUM AND LEAD IONS ON BIOMIMETIC HYDROXYAPATITE NANOCRYSTALS

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IN VITRO PREPARATIONS AND STUDIES ON THE SUBSTITUTION OF CADMIUM AND LEAD IONS ON BIOMIMETIC HYDROXYAPATITE NANOCRYSTALS

 

ABSTRACT

The hydrothermal and wet precipitation methods are successful routes to synthesize high purity hydroxyapatite (HA) as well as Cadmium and Lead doped hydroxyapatites at physiological conditions.

In this research, Ca(NO3)2.4H2O and NH4H2PO4 were chosen as the precursor materials used to synthesize HA. HA was first synthesized via optimization of the wet precipitation method under vigorous stirring using various precursor concentrations of 0.5, 1.0, 1.5 and 2.0M. The prepared HA powders were calcined at different temperatures of 300, 500, 800 and 1100oC for 3 hours and were characterized using XRF/EDX, FTIR and XRD. The FTIR bands were distinct, narrower with increased intensities when the precursor concentration and calcination temperature increases. XRF/EDX indicates an increase in Ca/P ratio as calcination temperature increased from 300°C to 500°C and at a particular calcination temperature, an increase in precursor concentration showed an irregular increase in the Ca/P ratio, an indication of a weak effect of precursor concentration on Ca/P ratio. XRD showed that as the precursor concentration is increased, with respect to the calcination temperature, peak intensities increased.

These observations of peak intensities and degree of crystallinity are reflected with a corresponding increase in crystallite size (D) with increase in both the precursor concentration and calcination temperature. The result showed that the HA particles were all in nano regime for all the precursor concentrations, although, the 0.5M precursor concentration and calcination temperature of 300oC gave the HA with greater similarity to the natural bone apatite as regards the Ca/P ratio. Based on the optimum conditions (0.5M and 300 oC) investigated at the first stage of the synthesis, further synthesis was carried out using the wet precipitation and hydrothermal methods at physiological conditions of pH and temperature (7.4 and 37 oC). The as-prepared powders were characterized via XRF/EDX, FTIR, XRD, SEM, PSA, BET, TEM and TG/DTA. The result obtained indicated particle nano-size particle with sizes of 26 nm ± 5% and 29 nm ± 5% respectively for the wet precipitation and hydrothermal methods and these were found to be thermally stable up to 1200oC. SEM images showed a non-uniform particle with various degrees of agglomeration that were observed to be highest for the hydrothermally prepared HA compared to the wet precipitated HA

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IN VITRO PREPARATIONS AND STUDIES ON THE SUBSTITUTION OF CADMIUM AND LEAD IONS ON BIOMIMETIC HYDROXYAPATITE NANOCRYSTALS