Spatial analysis of urine zinc (Zn) concentration for women of reproductive age and school age children in Malawi

Simple distance-based thread analytical device integrated with ion imprinted polymer for Zn2+ quantification in human urine samples

This article presents the development of a distance-based thread analytical device (dTAD) integrated with an ion-imprinted polymer (IIP) for quantitative monitoring of zinc ions (Zn2+) in human urine samples. The IIP was easily chemically modified onto the thread channel using dithizone (DTZ) as a ligand to bind to Zn2+ with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as well as 2,2-azobisisobutyronitrile (AIBN) as cross-linking agents to enhance the selectivity for Zn2+ detection. The imprinted polymer was characterized using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Under optimization, the linear detection range was from 1.0 to 20.0 mg L-1 (R2 = 0.9992) with a limit of detection (LOD) of 1.0 mg L-1. Other potentially interfering metal ions and molecules did not interfere with this approach, leading to high selectivity. Furthermore, our technique exhibits a remarkable recovery ranging from 100.48% to 103.16%, with the highest relative standard deviation (% RSD) of 5.44% for monitoring Zn2+ in human control urine samples, indicating high accuracy and precision. Similarly, there is no significant statistical difference between the results obtained using our method and standards on zinc supplement sample labels. The proposed method offers several advantages in detecting trace Zn2+ for point-of-care (POC) medical diagnostics and environmental sample analysis, such as ease of use, instrument-free readout, and cost efficiency. Overall, our developed dTAD-based IIP method holds potential for simple, affordable, and rapid detection of Zn2+ levels and can be applied to other metal ions' analysis.

Understanding the role of zinc ions on struvite nucleation and growth in the context of infection urinary stones

Taking into account that in recent decades there has been an increase in the incidence of urinary stones, especially in highly developed countries, from a wide range of potentially harmful substances commonly available in such countries, we chose zinc for the research presented in this article, which is classified by some sources as a heavy metal. In this article, we present the results of research on the influence of Zn2+ ion on the nucleation and growth of struvite crystals-the main component of infection urinary stones. The tests were carried out in an artificial urine environment with and without the presence of Proteus mirabilis bacteria. In the latter case, the activity of bacterial urease was simulated chemically, by systematic addition of an aqueous ammonia solution. The obtained results indicate that Zn2+ ions compete with Mg2+ ions, which leads to the gradual replacement of Mg2+ ions in the struvite crystal lattice with Zn2+ ions to some extent. This means co-precipitation of Mg-struvite (MgNH4PO4·6H2O) and Znx-struvite (Mg1-xZnxNH4PO4·6H2O). Speciation analysis of chemical complexes showed that Znx-struvite precipitates at slightly lower pH values than Mg-struvite. This means that Zn2+ ions shift the nucleation point of crystalline solids towards a lower pH. Additionally, the conducted research shows that Zn2+ ions, in the range of tested concentrations, do not have a toxic effect on bacteria; on the contrary, it has a positive effect on cellular metabolism, enabling bacteria to develop better. It means that Zn2+ ions in artificial urine, in vitro, slightly increase the risk of developing infection urinary stones.

Association of Urinary Zinc Concentrations with Dyslipidemia and Its Subtypes: Baseline Data from the Chinese Multi-Ethnic Cohort (CMEC) Study

This study elucidates the association between urinary zinc concentration and the risk of developing dyslipidemia and its subtypes in China's ethnic minority residents. Based on the baseline survey data of the Chinese Multi-Ethnic Cohort (CMEC) study, 10,620 subjects were included in the study. Logistic regression analysis evaluated the relationship between urinary zinc concentration and dyslipidemia and its subtypes. After adjustment, compared with urinary zinc concentration quartile 1 (Q1), the odds ratios (ORs) and 95% confidence intervals (95% CIs) of dyslipidemia participants in the quartile 2 (Q2), quartile 3 (Q3), and quartile 4 (Q4) groups were 1.091 (0.963, 1.237), 1.151 (1.051, 1.304), and 1.393 (1.230, 1.579), respectively (P for trend < 0.001). While that of hypertriglyceridemia participants in the Q2, Q3, and Q4 groups were 1.130 (0.979, 1.306), 1.283 (1.113, 1.480), and 1.483 (1.287, 1.709), respectively (P for trend < 0.001). Lastly, the ORs and 95% CIs of hyperbetalipoproteinemia participants in the Q2, Q3, and Q4 groups were 1.166 (0.945, 1.439), 1.238 (1.007, 1.522), and 1.381 (1.126, 1.695), respectively (P for trend < 0.002). This study found that urinary zinc concentrations were not associated with hypercholesterolemia and hypoalphalipoproteinemia. The dose-response relationship was non-linear between urinary zinc concentration and dyslipidemia, hypertriglyceridemia and hyperbetalipoproteinemia (P for trend < 0.001). In the stratified analysis, urinary zinc levels were positively associated with the risk of dyslipidemia, hypertriglyceridemia, and hyperbetalipoproteinemia in male, ≥ 60 years old, Miao nationality, hypertension, diabetes, and BMI ≥ 24.0 kg/m² subgroups. Our study provides some possible evidence that elevated urinary zinc concentrations are associated with an increased risk of dyslipidemia, hypertriglyceridemia, hyperbetalipoproteinemia.

The potential of spot urine as a biomarker for zinc assessment in Malawian children and adults

Population-level assessment of zinc deficiency remains a challenge due to the lack of suitable biomarkers. Spot urinary zinc concentration (UZC) has the potential to provide information on population zinc status in large-scale surveys, but there is no established cut-off point indicating deficiency. A strong correlation between this biomarker and an established biomarker such as serum zinc concentration (SZC) in paired samples (i.e., from the same individual), could identify the thresholds indicating zinc deficiency. This study, therefore, aimed to regress spot UZC from school-aged children and women from the Malawi micronutrient survey with paired SZC data using a linear mixed-effects model. The nested variance components indicated no linear relationship between the UZC and SZC data, irrespective of adjustments for inflammation and hydration. Thresholds of urinary zinc excretion that have been suggested by expert panels were applied to the spot UZC data, as a post-hoc analysis. The zinc deficiency prevalence estimates derived from these suggested thresholds were not similar to the estimates from the SZC data, and further research is required to understand whether spot UZC can still provide useful information in population zinc assessment.

Distribution and Determinants of Serum Zinc, Copper, and Selenium Levels among Children under Five Years from Popokabaka, Democratic Republic of Congo: A Cross-Sectional Study

Information about essential trace elements among children in many African countries, including the Democratic Republic of Congo (DRC), is limited. We aimed to measure the distribution and determinants of serum zinc (Zn), copper (Cu), and selenium (Se) concentrations in a representative sample of children under five years old. We conducted a community-based cross-sectional study in Popokabaka, DRC. Blood samples were drawn from 412 children. The serum concentrations of minerals were measured using inductively coupled plasma−mass spectrometry. The median concentrations (P25−P75) of Zn, Cu, and Se were 61.9 µg/dL (52.8−70.2), 145.5 (120.0−167.0) µg/dL and 5.3 (4.3−6.3) µg/dL. The CRP-adjusted prevalence of serum Se deficiency was 84.1% (95% confidence interval [CI] 81.4−87.0) and of Zn deficiency was 64.6% (95% CI 59.8−69.1%). Only a few children were Cu deficient [1.5% (0.6−3.2)]. Evidence of inflammation (C-reactive protein, >5 mg/L) was associated with a lower Se concentration and higher Cu concentration. Furthermore, serum Se concentration was positively associated with linear growth. The average Cu/Zn molar ratio (2:1) was twice that recommended. Children in western Popokabaka had higher Zn and Se levels than their eastern neighbors. Zinc and selenium deficiencies are common among children in Popokabaka and require attention and prioritization.

Human urinary biomonitoring in Western Kenya for micronutrients and potentially harmful elements

Spot urinary elemental concentrations are presented for 357 adults from Western Kenya collected between 2016 and 2019 as part of a wider environmental geochemical survey. The aim of this study was to establish population level urinary elemental concentrations in Western Kenya for micronutrients and potentially harmful elements for inference of health status against established thresholds. For elements where thresholds inferring health status were not established in the literature using urine as a non-invasive matrix, this study generated reference values with a 95% confidence interval (RV95s) to contextualise urinary elemental data for this population group. Data are presented with outliers removed based upon creatinine measurements leaving 322 individuals, for sub-categories (e.g. age, gender) and by county public health administrative area. For Western Kenya, reference values with a 95% confidence interval (RV95s) were calculated as follows (μg/L): 717 (I), 89 (Se), 1753 (Zn), 336 (Mo), 24 (Cu), 15.6 (Ni), 22.1 (As), 0.34 (Cd), 0.47 (Sn), 0.46 (Sb), 7.0 (Cs), 13.4 (Ba and 1.9 (Pb). Urinary concentrations at the 25th/75th percentiles were as follows (μg/L): 149/368 (I), 15/42 (Se), 281/845 (Zn), 30/128 (Mo), 6/13 (Cu), 1.7/6.1 (Ni), 2.0/8.2 (As). 0.1/0.3 (Cd), 0.05/0.22 (Sn), 0.04/0.18 (Sb), 1.2/3.6 (Cs), 0.8/4.0 (Ba) and 0.2/0.9 (Pb). Urinary concentrations at a population level inferred excess intake of micronutrients I, Se, Zn and Mo in 38, 6, 57 and 14% of individuals, respectively, versus a bioequivalent (BE) upper threshold limit, whilst rates of deficiency were relatively low at 15, 15, 9 and 18%, respectively. Each of the administrative counties showed a broadly similar range of urinary elemental concentrations, with some exceptions for counties bordering Lake Victoria where food consumption habits may differ significantly to other counties e.g. I, Se, Zn. Corrections for urinary dilution using creatinine, specific gravity and osmolality provided a general reduction in RV95s for I, Mo, Se, As and Sn compared to uncorrected data, with consistency between the three correction methods.