Study of new practical ESR dosimeter based on carbonated hydroxyapatite and its dosimetric properties

<div><p>The development of new dosimeters with good dosimetric properties is important for quality control in radiation applications. A new practical electron spin resonance (ESR) dosimeter based on carbonated hydroxyapatite that simulated the composition and structure of tooth enamel was specially synthesized. The synthesized material was investigated by transmission electron microscope, X-ray diffraction, fourier transform infrared spectroscopy and X-ray photo electron spectroscopy to confirm to the main composition of carbonated hydroxyapatite with CO₃^2- successfully doped into the crystal lattice through optimizing the synthesis process of C/P molar ratio, pH value dynamical adjustment, annealing temperature and time. The dosimetric properties were systematically investigated by ESR spectroscopy. The results indicated that the radiation induced signal had a good dose response within a relatively wide dose range. The dose response was linear in the dose range of 0–400 Gy with a correlation coefficient of 0.9999 and had dose accumulative effect in the experimental dose range of 0–100 Gy. In a wider dose range up to 30 kGy, the dose response also presented linear feature in double-logarithmic coordinate system with a correlation coefficient of 0.9970. The dose detection limit was about 0.34Gy with a given probability of 95% confidence level depending upon a rigid calculation algorithm. The signal was extremely stable in the observation time of 360 days with a variation coefficient of 3.8%. The radiation sensitivity of the material showed no remarkable variation against photon energy from 662 KeV to 1.25 MeV and dose rate from 0.86 Gy/min to 12.17 Gy/min. The material showed more sensitive in lower photon energy range below 662 keV, which hint additional calibration may need when using in special photon energy condition. The preliminary results suggested that this newly developed dosimeter was potential to become a practical dosimeter that would expand the application fields of ESR dosimetry.</p></div

Study of new practical ESR dosimeter based on carbonated hydroxyapatite and its dosimetric properties - Fig 6

<p>The dose rate effect (A) and photon energy dependence (B) of dosimeters.</p

The RIS intensity against time (Days) after irradiation.

<p>The RIS intensity against time (Days) after irradiation.</p

The results of material analysis.

<p>(A) TEM micrographs. (B) XRD analysis. (C) FTIR spectra. (D) XPS analysis.</p

The ESR spectra of dosimeter irradiated at 0 Gy, 0.3 Gy and 10 Gy.

<p>The ESR spectra of dosimeter irradiated at 0 Gy, 0.3 Gy and 10 Gy.</p

Synthesis flow chart of CHAP.

<p>Synthesis flow chart of CHAP.</p

The dose response curve.

<p>(A) The RIS intensity against radiation dose (0–400 Gy). (B) The RIS intensity against radiation dose (1Gy-30 kGy). (C) The RIS intensity against accumulated radiation dose (0–100 Gy).</p

The mannose-binding activity of Tat-hLSECtin-CRD using mannose-agarose columns.

<p>The western blot showing the mannose-binding activity of washed and eluted fractions. A portion of Tat-hLSECtin-CRD proteins had bound on mannose-agarose column.</p

Schematic diagram showing the construction of the prokaryotic expression vectors.

<p>The hLSECtin-CRD (360bp) cDNA fragments were cloned into the prokaryotic expression vector pET28b-Tat, pET28b, pET22b (+) and pGEX-6P-1 to construct the prokaryotic expression vectors pET28b-Tat-hLSECtin-CRD, pET28b-hLSECtin-CRD, pET22b(+)-hLSECtin-CRD and pGEX-6P-1-hLSECtin-CRD.</p

Identification of the subcellular microstructure of overexpressed Tat-hLSECtin-CRD or Tat-free hLSECtin-CRD bacterial cells by transmission electron microscopy.

<p>The arrowheads indicate different aggregation level of Tat-hLSECtin-CRD and Tat-free hLSECtin-CRD. a: pET28b(control); b: pET28b-Tat-hLSECtin-CRD, the red arrows indicate the denser region of Tat-hLSECtin-CRD in cytosol ; c: pET28b-hLSECtin-CRD, the red arrows indicate the dot denser region of Tat-free hLSECtin-CRD in cytosol.</p