Synthesis and characterization of Zn-Doped hydroxyapatite: scaffold application, antibacterial and bioactivity studies

Abstract

In this study, the antimicrobial and scaffold of zinc-substituted hydroxyapatite, (Zn-HAp) synthesized via chemical co-precipitation technique was investigated. The structure of the synthesized Zn-HAp was investigated with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Scanning electron microscope (SEM), Energy dispersive X-spectroscopy (EDAX), transmission electron microscope (TEM), Thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). Bioactivity study was performed in simulated body fluid (SBF), while the antimicrobial activity was studied using disc diffusion method. The XRD structure revealed that Zn ion incorporation up to 10% led to the second phase hydroxyapatite (HAp) formation, while higher concentration diminished the apatite structure. The presence of phosphate ions, carbonates ions, and hydroxyl groups in the apatite powder was ascertained by the FT-IR evaluation. SEM evaluation showed that the apatite contains fine particles with nearly round shape with interconnected pores and decreasing Ca/P ratio with increasing Zn ion concentration. TEM results showed particulate polycrystalline apatite with crystallite size ranging from 68 nm in pure HAp to 41 nm in 20% Zn-doped HAp indicating a decrease in the crystal size with increasing Zn ion in the samples. The bioactivity study showed spherical deposition around the porous region of the scaffold HAp suggesting the growth of apatite in SBF media after 7 days of incubation, while antibacterial activity studies showed zones of inhibition with an increase in zinc ions concentrations.

Keywords: Materials chemistry; Materials science.

Scheme 1

Flow chart for the chemical synthesis of HAp.

Fig. 1

XRD spectra of HAp and Zn-HAp composite.

Fig. 2

XRD spectra of Zn-HAp composite after sintering at 1000 °C.

Fig. 3

FT-IR spectra of HAp and Zn-HAp composite.

Fig. 4

FT-IR spectra of HAp and Zn-HAp after sintering at 1000 °C.

Fig. 5

SEM images of (a) HAp (b) sintered HAp at 1000 °C, (c) 10%Zn + HAp and (d) sintered 10%Zn + HAp at 1000 °C.

Fig. 6

TEM images of (a) HAp and (b) 10%Zn-HAp with their corresponding SAED as inserted.

Fig. 7

EDAX of (a) pure HAp, (b) Zn-HAp nano composite, (c) Ca/P ratio and (d) green and sintered densities of Zn-HAp nano composite against Zn concentration.

Fig. 8

XPS spectra of 10%Zn-HAp nano composite showing the devolution of biding energies of (a) calcium, (b) oxygen and oxygen-phosphorous, (c) phosphorous, and (d) zinc.

Fig. 9

TGA Analyses of (a) HAp and (b) 10%Zn-HAp nano composite at 1000 °C.

Fig. 10

Images of (a) HAp, (b) pellet of HAp (c) scaffold HAp-AMB composite after sintering at 1000 °C and (d) mercury porosimeter of HAp scaffold.

Fig. 11

Plots of (a) porosity and densification against weight percent and (b) zone of inhibition of HAp and Zn-doped hydroxyapatite at different Zn concentrations.

Fig. 12

SEM images of (a) 10%Zn/HAp scaffold, (b) 10%Zn/HAp scaffold after 3 days, and (c) after 7days of immersion in SBF solution at pH of 7.4 and temperature of 37 °C.

Fig. 13

FT-IR spectra of 10%Zn/HAp before and after immersion in SBF solution.

Fig. 14

Kinetics study of the release of Zn ions from Zn-HAp composite at a solution pH of 7.4 and temperature of 37 °C.