As a kind of unicellular eukaryotic protozoa, Tetrahymena is located at the bottom of the aquatic food webs and plays an essential role in the bioaccumulation of mercury (Hg). To track Hg in individual Tetrahymena, a capillary single-cell inductively coupled plasma mass spectrometry (ICPMS) online system was developed. The experimental and instrumental conditions were optimized to ensure the signal detected was the Hg uptake in individual Tetrahymena. Moreover, a quantitative method was established and validated by detecting Hg2+ standard solutions. The limit of quantity was calculated to be approximately 3.8 × 10–15 g Hg/cell, and the detection limit for Hg2+ exposure of Tetrahymena was 0.05 μg/L. By using the proposed method, we found the peak became wider with increasing of exposure concentrations, indicating the accumulated Hg by different Tetrahymena varied greatly, and the difference was more significant at higher exposure concentration. This novel method has the advantages of high sensitivity and real-time detection in individual Tetrahymena, and it could be widely used for further tracking the accumulation of mercury and other metals at the single cell level.

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Background. At present, the diagnostic accuracy of alpha-fetoprotein (AFP) for hepatocellular carcinoma (HCC) surveillance is insufficient. It remains controversial whether prothrombin induced by vitamin K absence II (PIVKA-II) has a better diagnostic value than AFP for HCC patients. Objective. To investigate the diagnostic role of PIVKA-II alone or in combination with AFP in Chinese HCC patients. Methods. Serum AFP and PIVKA-II levels were detected and analyzed in 308 HCC afflicted patients and 120 unafflicted controls. The receiver operator curve (ROC) and area under the curve (AUC) were conducted to evaluate the clinical value of AFP and PIVKA-II for diagnosing HCC and early HCC. Results. In the whole HCC cohort, the diagnostic values of PIVKA-II were better than that of AFP. The AUC of PIVKA-II and AFP was 0.90 (95% CI 0.87-0.94) and 0.79 (95% CI 0.74-0.84), respectively. “AFP + PIVKA-II” yielded a high sensitivity of 95.1% and a specificity of 83.3%, with the AUC 0.89 (95% CI 0.85-0.93). In the early stage HCC group, the diagnostic accuracy of PIVKA-II was also better than that of AFP. The AUC of PIVKA-II and AFP was 0.83 (95% CI 0.77-0.89) and 0.75 (95% CI 0.68-0.81), respectively. “AFP + PIVKA-II” achieved the sensitivity of 83.3% and specificity of 89.1%, with an AUC of 0.86 (95% CI 0.81-0.91). Moreover, for AFP-negative HCC patients, serum PIVKA-II showed good diagnostic performance, with an AUC of 0.804 (95% CI 0.720-0.887). Besides, elevated PIVKA-II level was a strong independent risk factor for HCC patients with portal vein tumor thrombus (PVTT) ( OR = 4.890 , P = 0.020 ). Conclusion. PIVKA-II is superior to AFP in HCC screening, and AFP in combination with PIVKA-II significantly improves the diagnostic value for Chinese HCC patients. PIVKA-II could effectively indicate HCC accompanied by PVTT and help to optimize the therapeutic strategy.