Wolfe T, Guidelli E J, Gómez J A, Baffa O, Nicolucci P
Experimental Radiation Oncology Department, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA.
Phys Med Biol. 2015 Jun 7;60(11):4465-80. doi: 10.1088/0031-9155/60/11/4465. Epub 2015 May 19.
In this work, we aim to experimentally assess increments of dose due to nanoparticle-radiation interactions via electron spin resonance (ESR) dosimetry performed with a biological-equivalent sensitive material.We employed 2-Methyl-Alanine (2MA) in powder form to compose the radiation sensitive medium embedding gold nanoparticles (AuNPs) 5 nm in diameter. Dosimeters manufactured with 0.1% w/w of AuNPs or no nanoparticles were irradiated with clinically utilized 250 kVp orthovoltage or 6 MV linac x-rays in dosimetric conditions. Amplitude peak-to-peak (App) at the central ESR spectral line was used for dosimetry. Dose-response curves were obtained for samples with or without nanoparticles and each energy beam. Dose increments due to nanoparticles were analyzed in terms of absolute dose enhancements (DEs), calculated as App ratios for each dose/beam condition, or relative dose enhancement factors (DEFs) calculated as the slopes of the dose-response curves.Dose enhancements were observed to present an amplified behavior for small doses (between 0.1-0.5 Gy), with this effect being more prominent with the kV beam. For doses between 0.5-5 Gy, dose-independent trends were observed for both beams, stable around (2.1 ± 0.7) and (1.3 ± 0.4) for kV and MV beams, respectively. We found DEFs of (1.62 ± 0.04) or (1.27 ± 0.03) for the same beams. Additionally, we measured no interference between AuNPs and the ESR apparatus, including the excitation microwaves, the magnetic fields and the paramagnetic radicals.2MA was demonstrated to be a feasible paramagnetic radiation-sensitive material for dosimetry in the presence of AuNPs, and ESR dosimetry a powerful experimental method for further verifications of increments in nanoparticle-mediated doses of biological interest. Ultimately, gold nanoparticles can cause significant and detectable dose enhancements in biological-like samples irradiated at both kilo or megavoltage beams.
在这项工作中，我们旨在通过使用生物等效敏感材料进行电子自旋共振（ESR）剂量测定，以实验方式评估由于纳米颗粒与辐射相互作用而导致的剂量增加。我们采用粉末形式的2-甲基丙氨酸（2MA）来构成嵌入直径为5纳米的金纳米颗粒（AuNP）的辐射敏感介质。在剂量测定条件下，用临床使用的250 kVp正交电压或6 MV直线加速器X射线对含有0.1% w/w AuNP或不含纳米颗粒的剂量计进行辐照。ESR光谱中心线的峰峰值幅度（App）用于剂量测定。获得了有或没有纳米颗粒以及每种能量束的样品的剂量响应曲线。根据绝对剂量增强（DE）分析由于纳米颗粒导致的剂量增加，DE计算为每种剂量/束条件下的App比值，或者根据剂量响应曲线的斜率计算相对剂量增强因子（DEF）。观察到剂量增强在小剂量（0.1 - 0.5 Gy之间）时呈现放大行为，这种效应在kV束下更为突出。对于0.5 - 5 Gy之间的剂量，两种束均观察到与剂量无关的趋势，kV束和MV束分别稳定在（2.1 ± 0.7）和（1.3 ± 0.4）左右。对于相同的束，我们发现DEF分别为（1.62 ± 0.04）或（1.27 ± 0.03）。此外，我们测量了AuNP与ESR仪器之间不存在干扰，包括激发微波、磁场和顺磁自由基。结果表明，在存在AuNP的情况下，2MA是一种用于剂量测定的可行的顺磁辐射敏感材料，并且ESR剂量测定是一种强大的实验方法，可用于进一步验证纳米颗粒介导的具有生物学意义的剂量增加。最终，金纳米颗粒可在千伏或兆伏束辐照的类似生物样品中引起显著且可检测到的剂量增强。
