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Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core – Shell Particle for Protein Adsorption and pH-Controlled Release

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ABSTRACT

Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.

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TEM image of core–shell structure of apatite (Ap)-coated citric acid–stabilized cobalt ferrite (CFCA-Ap) in low (a) and high-resolution field (b), and SEM image of CFCA-Ap particles (c). EDS analysis of the samples at the CFCA-Ap surface: Ca/P = 1.47 (d). Core–shell structure of CFCA-Ap particles corresponding electron diffraction patterns of core structure (e) and shell structure (f). g is size distribution of core–shell structure of CFCA-Ap.
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Figure 4: TEM image of core–shell structure of apatite (Ap)-coated citric acid–stabilized cobalt ferrite (CFCA-Ap) in low (a) and high-resolution field (b), and SEM image of CFCA-Ap particles (c). EDS analysis of the samples at the CFCA-Ap surface: Ca/P = 1.47 (d). Core–shell structure of CFCA-Ap particles corresponding electron diffraction patterns of core structure (e) and shell structure (f). g is size distribution of core–shell structure of CFCA-Ap.

Mentions: The TEM image of CFCA-Ap shows the core–shell structure (Figure 4a, b). The calcium phosphate of hydroxyapatite coating on the CFCA surface is seen to be inhomogeneous. Plates like structure are distributed around the spherical CF particle. The composite particles formed have an average core of 100–200 nm and the shell thickness is about 50–100 nm. An analysis of the SEM images of the CFCA-Ap particles (Figure 4c) provides some insight into the mechanism of nucleation. They show the growth of apatite mineral to be the aggregation of particles to form globular spheres less than 1 μm in size. Large peaks that appear in the EDS patterns from the surface of the CFCA-Ap (seen in the insert (Figure 4d)) are due to Fe and Co to Ca and P. These peaks indicate that the average atomic Ca/P ratio is 1.47, which is within the range seen in biological apatite [28,29]. The ED patterns of CFCA-Ap particle at the core (Figure 4e) are indicative of the polycrystalline nature of the cobalt ferrite particles. They show that the particles are composed of fine randomly orientated crystal grains. The lower intensity of the diffraction peaks emanating from the embedded CoFe2O4 core is due to the decrease in the intensity of the incident electron before it reaches the core. The electron diffraction ring patterns of the apatite at the surface of cobalt ferrite particles are shown in Figure 4f. The pattern emanating from the shell exhibits poorly resolved ring spot due to the disordered nature of the materials in the shell. The distribution in the sizes of the particles is shown in Figure 4g. The diameters of the particles are in the range between 400 and 1,200 nm, with a mean particle diameter of about 750 nm. The relative high diameter implied that a high degree of agglomerations had occurred. This may have resulted from the heterogeneous surface activities of the mineralization processes.


Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core – Shell Particle for Protein Adsorption and pH-Controlled Release
TEM image of core–shell structure of apatite (Ap)-coated citric acid–stabilized cobalt ferrite (CFCA-Ap) in low (a) and high-resolution field (b), and SEM image of CFCA-Ap particles (c). EDS analysis of the samples at the CFCA-Ap surface: Ca/P = 1.47 (d). Core–shell structure of CFCA-Ap particles corresponding electron diffraction patterns of core structure (e) and shell structure (f). g is size distribution of core–shell structure of CFCA-Ap.
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Figure 4: TEM image of core–shell structure of apatite (Ap)-coated citric acid–stabilized cobalt ferrite (CFCA-Ap) in low (a) and high-resolution field (b), and SEM image of CFCA-Ap particles (c). EDS analysis of the samples at the CFCA-Ap surface: Ca/P = 1.47 (d). Core–shell structure of CFCA-Ap particles corresponding electron diffraction patterns of core structure (e) and shell structure (f). g is size distribution of core–shell structure of CFCA-Ap.
Mentions: The TEM image of CFCA-Ap shows the core–shell structure (Figure 4a, b). The calcium phosphate of hydroxyapatite coating on the CFCA surface is seen to be inhomogeneous. Plates like structure are distributed around the spherical CF particle. The composite particles formed have an average core of 100–200 nm and the shell thickness is about 50–100 nm. An analysis of the SEM images of the CFCA-Ap particles (Figure 4c) provides some insight into the mechanism of nucleation. They show the growth of apatite mineral to be the aggregation of particles to form globular spheres less than 1 μm in size. Large peaks that appear in the EDS patterns from the surface of the CFCA-Ap (seen in the insert (Figure 4d)) are due to Fe and Co to Ca and P. These peaks indicate that the average atomic Ca/P ratio is 1.47, which is within the range seen in biological apatite [28,29]. The ED patterns of CFCA-Ap particle at the core (Figure 4e) are indicative of the polycrystalline nature of the cobalt ferrite particles. They show that the particles are composed of fine randomly orientated crystal grains. The lower intensity of the diffraction peaks emanating from the embedded CoFe2O4 core is due to the decrease in the intensity of the incident electron before it reaches the core. The electron diffraction ring patterns of the apatite at the surface of cobalt ferrite particles are shown in Figure 4f. The pattern emanating from the shell exhibits poorly resolved ring spot due to the disordered nature of the materials in the shell. The distribution in the sizes of the particles is shown in Figure 4g. The diameters of the particles are in the range between 400 and 1,200 nm, with a mean particle diameter of about 750 nm. The relative high diameter implied that a high degree of agglomerations had occurred. This may have resulted from the heterogeneous surface activities of the mineralization processes.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.

No MeSH data available.