Institute of Analytical and Bioanalytical Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
Universitätsfrauenklinikum Ulm, Prittwitzstrasse 43, 89075, Ulm, Germany.
Anal Bioanal Chem. 2022 Jun;414(15):4519-4529. doi: 10.1007/s00216-022-04112-5. Epub 2022 May 13.
Placental elemental composition can serve as an indicator for neonatal health. Medical studies aiming at revealing such cause-and-effect relationships or studies monitoring potential environmental influences consist of large sample series to ensure statistically sufficient data. Several analytical techniques have been used to study trace metals in human placenta. However, most techniques require provision of clear liquid sample solutions and therefore time- and reagent-consuming total digestion of biological tissue is necessary. In total reflection X-ray fluorescence spectrometry (TXRF)-a straightforward multielement analytical technique-in contrast suspensions of minute sample amounts can be analyzed directly. Therefore, herein we report on a valid method to prepare homogenous sample suspensions for sustainable and fast TXRF analysis of large sample series. The optimized method requires only 10 mg of powdered placental tissue and 1 mL nitric acid. Suspensions are readily prepared within 30 min and the found mass fractions of major, minor, and trace elements are in good agreement in comparison to analysis of digests. In addition, possible effects on fixation time and the exact sampling location, i.e., maternal vs. fetal side of the placenta, were studied applying this method. Thereby, significant differences for fetal placenta tissue compared to maternal or intermediate tissue were observed revealing accumulation of trace elements in the fetal side of the placenta. Furthermore, considerable depletion of up to 60% mass fraction with longer fixation duration occurred in particular in fetal placenta tissue. These findings help to understand the large ranges of mass fraction of elements in placenta reported in the literature and at the same time indicate the necessity for more systematic investigation of non-homogenous elements distributed in placenta taking sampling and stabilization methods into account.
胎盘元素组成可作为新生儿健康的指标。旨在揭示这种因果关系或监测潜在环境影响的医学研究由大量样本系列组成，以确保有足够的统计数据。已经使用了几种分析技术来研究人胎盘中的痕量金属。然而，大多数技术需要提供清晰的液体样品溶液，因此需要对生物组织进行耗时且耗试剂的全消解。在全反射 X 射线荧光光谱法（TXRF）-一种简单的多元素分析技术-中，可以直接分析微小样品量的悬浮液。因此，本文报道了一种有效的方法，用于制备均质样品悬浮液，以便对大量样本系列进行可持续和快速的 TXRF 分析。该优化方法仅需要 10 毫克粉末状胎盘组织和 1 毫升硝酸。悬浮液可在 30 分钟内轻松制备，与消化分析相比，主要、次要和痕量元素的发现质量分数非常吻合。此外，还研究了该方法对固定时间和确切采样位置（胎盘的母体侧与胎儿侧）的可能影响。因此，与母体或中间组织相比，胎儿胎盘组织观察到明显的差异，表明痕量元素在胎盘的胎儿侧积累。此外，在胎儿胎盘组织中，固定时间较长时，质量分数的损耗甚至高达 60%。这些发现有助于理解文献中报道的胎盘元素质量分数的大范围，并同时表明有必要更系统地研究分布在胎盘中的非均质元素，考虑到采样和稳定化方法。
