Materials and Methods: Seventy-five subjects, 42 males (56%) and 35 females (44%) of age group ranging 7-13 years, living in South Canara district of Karnataka, India, were selected as a part of the study. Hair and urine samples were collected for estimation of organic and inorganic levels of mercury, respectively. Informed consent was collected from all the participating subjects.
Results: On comparison between organic and inorganic mercury levels during the study period, the concentration of organic mercury in hair samples was greater irrespective of amalgam restorations present (1.172 and 0.085, respectively; P < 0.001).
Conclusion: Thus inorganic levels of mercury do not seem to pose a threat as much as the organic levels observed in hair, which remain fairly constant for a longer period of time. Hence in a coastal region where this study was undertaken and fish being a staple food, the risk could probably be attributed to more of an organic toxicity than an inorganic one. Thus amalgam is relatively safe to be practiced and the controversy against it should be reevaluated.
OBJECTIVES: The aim of this study is to develop a colorimetric sensor to detect Hg2+ in water sources using HRP inhibitive assay. The system can be incorporated with a mobile app to make it practical for a prompt in-situ analysis.
METHODS: HRP enzyme was pre-incubated with different concentration of Hg2+ at 37°C for 1 hour prior to the addition of chromogen. The mix of PBS buffer, 4-AAP and phenol which act as a chromogen was then added to the HRP enzyme and was incubated for 20 minutes. Alcohol was added to stop the enzymatic reaction, and the change of colour were observed and analyse using UV-Vis spectrophotometer at 520 nm wavelength. The results were then analysed using GraphPad PRISM 4 for a non-linear regression analysis, and using Mathematica (Wolfram) 10.0 software for a hierarchical cluster analysis. The samples from spectroscopy measurement were directly used for dynamic light scattering (DLS) evaluation to evaluate the changes in HRP size due to Hg2+ malfunctionation. Finally, molecular dynamic simulations comparing normal and malfunctioned HRP were carried out to investigate structural changes of the HRP using YASARA software.
RESULTS: Naked eye detection and data from UV-Vis spectroscopy showed good selectivity of Hg2+ over other metal ions as a distinctive color of Hg2+ is observed at 0.5 ppm with the IC50 of 0.290 ppm. The mechanism of Hg2+ inhibition towards HRP was further validated using a dynamic light scattering (DLS) and molecular dynamics (MD) simulation to ensure that there is a conformational change in HRP size due to the presence of Hg2+ ions. The naked eye detection can be quantitatively determined using a smartphone app namely ColorAssist, suggesting that the detection signal does not require expensive instruments to be quantified.
CONCLUSION: A naked-eye colorimetric sensor for mercury ions detection was developed. The colour change due to the presence of Hg2+ can be easily distinguished using an app via a smartphone. Thus, without resorting to any expensive instruments that are mostly laboratory bound, Hg2+ can be easily detected at IC50 value of 0.29 ppm. This is a promising alternative and practical method to detect Hg2+ in the environment.