2.3 Characterization of the epoxy-functionalized magnetic
colloidal particles
Before the application of the prepared magnetic colloidal particles
(CSMPC) in MRI, they were characterized to determine the suitability of
their use in biomedical diagnostic. The chemical composition of the
prepared magnetic particles was examined by the Fourier-transform
infrared (FTIR) spectroscopic technique using a Shimadzu FTIR 8400S
instrument (IRPrestige-2, Japan). The spectra were recorded as the
average of 40 scans in the region 400 to 4000 cm-1 at
4 cm-1 resolution. TEM (Phillips CM120) was used to
investigate the morphology and microstructure of the magnetic polymer
particles. Briefly, a drop of water diluted sample was deposited onto a
carbon-coated copper grid and then left to dry at room temperature
overnight before TEM imaging. Malvern Zetasizer 3000 HS instrument was
used for measurement of average hydrodynamic size
(D h) of the magnetic polymer colloidal particles
in 10-3 M NaCl solution, at 25oC.
The average value of three measurements was determined and taken into
consideration. TGA (NETZSCH TG209) was used to determine the magnetite
content of the magnetic polymer particles. The measurements were
performed under a nitrogen atmosphere from ambient temperature up to
700oC with heating rate 20°C/min. The saturation
magnetization (Ms) and magnetic behavior of the dried magnetic polymer
latexes were investigated using a vibrating sample magnetometer (VSM).
This test was carried out on the Automatic Bench of magnetic
measurements, CNRS-IRC Lyon. The magnetization of all dried particles
was investigated by decreasing the magnetic field (H) from +20000 to
-20000 Oersted, at room temperature. Malvern Zetasizer (NanoZS2000) was
used to measure the charge density or zeta potential (ζ) of the magnetic
polymer colloidal particles in 10-3 M NaCl solution at
different pH media, at 25oC. Each recorded value was
the average of three measurements.
In-Vitro Magnetic Resonance Imaging
Studies
Samples for MR-imaging studies were prepared by using variable
concentrations (Fe concentration of 0.05, 0.025, 0.0125, 0.00625,
0.003125 ml/10ml of water) of CSMPC in deionized water. Testing was
performed on all the samples using clinical 1.5T Toshiba Vantage Titan
scanner. T1 and T2 weighted images were
captured during testing to measure both T1 sequences
“Longitudinal relaxation time” (typically TR: 40, 225, 425, 825 ms and
TE: 12 ms) and T2 sequence “Transverse relaxation
time” (typically TE: 15, 45, 75, 105, 135, 165 ms and TR: 5000 ms).
Experimentation was done under ambient conditions by placing the
colloids directly on the top of the multichannel coil’s body. MRI images
were studied in K-Pacs-Lite and images were analyzed, visualized, and
reconstructed using the statistical tool. Equal circular area (region of
interest ROI) was chosen for each sample image and intensity data
(Hounsfield) that is based on the intensity of the pixel contained
within ROI were recorded. The mean intensity values were taken to
compare relative intensity with reference (Deionized water) and each
concentration.