Physics Department, Mount Allison University, Sackville, New Brunswick, Canada.
Department of Community Health and Epidemiology, Dalhousie University, Halifax, Nova Scotia, Canada.
PLoS One. 2024 Oct 23;19(10):e0310845. doi: 10.1371/journal.pone.0310845. eCollection 2024.
Zinc and selenium are essential minerals for human nutrition. Reliable biomarkers of zinc status and selenium status in humans are therefore important. This work investigates a novel portable X-ray fluorescence (XRF) method with the ability to rapidly assess zinc and selenium in nail clippings. This approach used a mono-energetic X-ray beam to excite characteristic X-rays from the clippings. Nail clippings were obtained from the Mother and Infant Nutrition Investigation (MINI), a study designed to assess nutrition in a population of women and their breastfed children in New Zealand. Twenty mother-infant pairings were selected to provide nail clippings at two time points (visit 1 at 3 months postpartum; visit 2 at 6 months postpartum). Nail clippings from each mother-infant pairing were divided into three groupings of clippings prior to analysis: those obtained from a big toe of the mother, those from the other toes of the mother, and those from the toes and fingers of the infant. Clippings were prepared and mounted prior to XRF measurement, providing four distinct fragments from each clipping grouping. These fragments were assessed by XRF using a measurement time of either 300 s (visit 1) or 180 s (visit 2). XRF results were determined through both an automated system output and an analysis of the X-ray energy spectrum. Following this assessment of zinc and selenium with the non-destructive XRF method, clippings were measured for zinc and selenium concentration using a "gold standard" technique of inductively coupled plasma mass spectrometry (ICP-MS). Mean ICP-MS concentrations ranged from 122 μg/g to 127 μg/g for zinc, and from 0.646 μg/g to 0.659 μg/g for selenium. Precision, assessed by a relative standard deviation of measurement, was superior for ICP-MS relative to XRF. For both zinc and selenium, XRF results were compared with ICP-MS concentrations. Linear equations of best fit were determined for each comparison between XRF and ICP-MS results. Coefficients of determination (r2) were stronger for zinc (from 0.74 to 0.95) than selenium (from 0.53 to 0.70). A decrease in XRF measurement time from 300 s to 180 s did not appear to adversely affect the correlation between XRF and ICP-MS results. Using the mono-energetic portable XRF method, the correlation of XRF zinc results with ICP-MS zinc concentrations was improved over previous findings, and selenium measurement was reported for the first time. The method may prove useful for future applications to trace element analysis using nail clippings as a biomarker.
锌和硒是人体营养必需的矿物质。因此，可靠的人体锌和硒状态生物标志物非常重要。本研究采用一种新型的便携式 X 射线荧光（XRF）方法，能够快速评估指甲中的锌和硒。该方法使用单能 X 射线束激发指甲中的特征 X 射线。指甲取自母婴营养调查（MINI），这是一项旨在评估新西兰母婴营养的研究。选择了 20 对母婴配对，在两个时间点（产后 3 个月的第 1 次就诊和产后 6 个月的第 2 次就诊）获得指甲。在进行 XRF 分析之前，将每个母婴配对的指甲分为三组：来自母亲大脚趾的指甲、来自母亲其他脚趾的指甲以及来自婴儿脚趾和手指的指甲。在进行 XRF 测量之前，对指甲进行准备和安装，每个指甲分组提供四个不同的碎片。使用 300 s（第 1 次就诊）或 180 s（第 2 次就诊）的测量时间通过 XRF 对这些碎片进行评估。XRF 结果通过自动系统输出和 X 射线能谱分析来确定。使用非破坏性 XRF 方法评估锌和硒后，使用电感耦合等离子体质谱法（ICP-MS）的“金标准”技术测量指甲中的锌和硒浓度。锌的 ICP-MS 浓度范围为 122 μg/g 至 127 μg/g，硒的浓度范围为 0.646 μg/g 至 0.659 μg/g。通过相对标准偏差来评估的精密度，ICP-MS 优于 XRF。对于锌和硒，将 XRF 结果与 ICP-MS 浓度进行比较。确定了 XRF 与 ICP-MS 结果之间的最佳拟合线性方程。XRF 与 ICP-MS 结果之间的决定系数（r2）对于锌（0.74 至 0.95）强于硒（0.53 至 0.70）。将 XRF 测量时间从 300 s 缩短至 180 s 似乎并未对 XRF 与 ICP-MS 结果之间的相关性产生不利影响。使用单能便携式 XRF 方法，XRF 锌结果与 ICP-MS 锌浓度的相关性得到了改善，并且首次报告了硒的测量结果。该方法可能对未来使用指甲作为生物标志物进行微量元素分析的应用非常有用。
